Small Kayak - Under 13 feet - Stability? [Archive]

alan white

12-16-2008, 11:56 AM

For your weight, under ten feet will be a challenge if speed is an issue.
A kayak can be long and slim or short and fat. Your idea of a short kayak (under ten feet) means a rather beamy shape not only because of the length but also because of your weight carrying requirements.
A nine foot kayak for you might be 36" wide.
What happens to performance? The boat will be very efficient at low power input but when you treally want to move it will hit "the wall" early and waste your energy making waves.
If you enjoy paddling along at 2-3 miles per hour, you'll really like the short and wide kayak.
The shorter hull won't track nearly as well as the longer type. It will be more maneuverable, however, and you can load gear in it more easily due to the better (larger) access at the cockpit opening. The weight of gear will be closer to middle too, which is a plus.
Now, for stability, initial stability will be very good compared to a longer boat in potential, depending on the bottom shape. All things being equal, however, the wide boat will be initially very stable.
Final stability, meaning tndancy to be stable at greater angles of heel, will be poor with the wider boat. The reason has to do with the fact that such a shape becomes very narrow as presented to the water when heeled a lot, like a pancake on edge, while the narrowest of boats would be more like a banana on edge.
If rolling your kayak is how you intend to recover a capsize, get a narrow, long boat. If avoiding capsize in the first place is most importasnt, if you're happy with the slow speed limitation, go for the short wide boat.

Alan

millionswords

12-16-2008, 12:09 PM

NO rolling Thnaks Alan.

I intend to carry camera equipment, and never wanna roll with them all! :O

I'm looking to do some Bird watching, and photograph them.
So faster is not the 1st criteria or a criteria at all.

The shorter it is, the easier for me to transport, I have a small car.
The shorter, the easier for me to store (apartment).

So I will compromise on the speed for these priority.

Some one tell me how wide should the boat be? for a 9 foot LOA.

9' x 30" with a cockpit that is about 32" x 15" ?? would it work?

alan white

12-17-2008, 12:57 AM

That would work I think, as a waterline beam, if you don't carry much extra weight. A good margin would be to figure you might occasionally carry another 10-20 lbs.
You can figure this yourself easily. Multiply your proposed (underwater) midship section with the waterline length and then multiply again with .54 (an average prismatic coefficient). This gives submerged cubic feet.
Then multiply by lbs per cubic ft (of sea water, 62 lbs fresh, 64 lbs salt) to get displacement.
The displacement should be figured at about the weight you anticipate would be your average, meaning you, the boat, and average cargo combined.
You can adjust the depth, beam, and curvature athwartship until you come up with your target displacement using the formula. Every little change you make will also affect stability and speed, since you'll be working with bilge and bottom shapes to achieve the ideal.
A dead flat bottom amidship will make for a wider beam and greater stability but will have more skin friction than a bottom that's rounded more, and so it will be a bit slower with the same paddling input.

A.

millionswords

12-17-2008, 01:15 AM

Alan = that was really helpful in demystifying the formula.
I read it else where, but you explained it easier to understand.

I'm seeing KFoundry the Kayak software from blueheron site, and it seems useful, though it is specially made for Strip Built Kayaks.

My only hinderance to start building was to get some figures on board to make me confident to start building.

I searched yesterday night for many Kayak Shops online, and gathered a lot of LOA X Width X Height combinations that take an average of 300 lbs paddler.

It worked out well, and I understood the shorter the Kayak, the wider it became. So with that ratio in mind, I started to work out some ratios.

I have a discussion going in kayakforum about the LOA. Many debate to build a longer boat and I will be a happy man. And tell me it is not that difficult to carry a 14 foot boat in my smart car. :)

Guess experience talks, wondering if I will learn by my mistakes after making a short boat, or is there a trick to make a short boat decently fast.

I have summarized my application above, and you know I dont wanna race with my Kayak. Just go about without wobbling, and going with the wind.

What come up to your mind? Throw some light!

alan white

12-17-2008, 12:23 PM

For many reasons, I personally would prefer a fifteen foot long kayak for general use, but I use a nine foot one to ferry myself and cargo out to my sailboat because it is wide and stable in calm water. I say calm water because a beamy kayak isn't necessarily the most stable in rough water. It's more affected by the angle of the water surface it sits upon than a narrower round-bottom or arc-bottom type.
You mentioned that you'd be going out in relatively calm conditions, so beaminess is an asset for you.
You also said you don't mind a slow boat, but only if necessary. You have to strike a comprimise, of course. For instance, a slight arc in the bottom will reduce wetted surface, helping efficiency, though the final top speed will be about the same. Wetted surface doesn't change top speed so much as length does. A nine foot waterline length will limit you to 4.02 knots. A sixteen foot waterline, 5.36 knots. These figures are derived from taking the square root of the waterline length and multiplying that by 1.34.
The closer you get to the top speed, the harder you work to make the next quarter knot. Moreso with the beamy boat, which will be very tiring at four knots---- while the sixteen foot boat will be less tiring at say 5.2 knots.
The reason is in the shape itself, which favors the needle shape at the upper speed potential.
However, it's the short and squat shape (more 'bowl-like" as seen by the water) that takes less paddling input at the lower speeds, like at 1 or two knots. At very low speeds, length to beam ratios of 1:1 actually reduce power requirements because only skin friction matters, and a half-sphere hull underbody, for example, has the least surface area (wetted area) of all.
A small child with his tiny amount of power might do better with a bath tub shape, in other words.
You might choose a somewhat longer boat for one reason---- they track a lot better, which is itself an energy-saver. A zig-zag course wastes a bit of energy in addition to being less elegant to watch or experience.
My guess is, after reading this, you might think about a twelve foot kayak and its moderate speed potential of 4.64.
Everything in life is a comprimise.

millionswords

12-17-2008, 12:54 PM

Everything in life is a compromise - I liked that best of all! Alan - I more than agree!!

I have decided to go with a 13 foot, as a lot of you suggested.
A 13 footer that is!

Okay now coming to Offset Tables.
I have this offset table for a Kayak called Sea Bee by Tom Yost.
I thought I will use it to make my FORMS, and build over it.

I have just understood what these tables are, and how to interpret them.
I tried to Loft them on some poster board, and knew these are multi chine offsets.

http://lh3.ggpht.com/_v8LXlvxOgoY/SUk8XZOkDwI/AAAAAAAACGE/99Gx9JCOfFI/s128/IMG_5890.JPG
http://lh3.ggpht.com/_v8LXlvxOgoY/SUk8XXyEalI/AAAAAAAACGM/rTQU--3Rr8c/s640/IMG_5893.JPG
Would I need a multi chine (more work?) or will I do better with a Single Chine boat?

If so, how will I change this multi chine to a single-chine table?

Today I bought some bamboo and Poly twine.
The twine holds up a 20 KG UPS easily. I tried swinging my UPS, Ooh that was scary, but it took all the weight. It is easy to wax it and easy to use.

Bamboo looks healthy, green bamboo 20 feet, 1 incher, under $1
10 feet of it can be used for major frame construction, because of its nice even diameter.

Attached are the pictures of the Bamboo and Poly Twine.
http://lh3.ggpht.com/_v8LXlvxOgoY/SUiq0_oP2eI/AAAAAAAACFw/Czvh-kU3zvU/s512/IMG_5888.JPG
http://lh5.ggpht.com/_v8LXlvxOgoY/SUiq0-G1elI/AAAAAAAACFo/0bUrW0748Cw/s640/IMG_5885.jpg

Any suggestions welcome, I'm trying now to bind the bamboo in different styles. Will come up with some pictures later.

alan white

12-17-2008, 01:53 PM

You won't easily change from multi-chine to single! It's a lot of work even if you're a qualified designer. Best to start with a single-chine kayak in the first place.
I don't understand the rest of your comment. If you're using that bamboo for lofting, don't. They are too crude. In fact, why would you need to loft? A multi or single chine boat has the advantage of stitch and glue construction, so all you need are mold patterns and station spacing, which is what you pay for in any multi-chine plan.
The boat you mention, Sea Bee, must be a strip construction, without chines.
The offsets provided require a surface (usu. a floor you na nail into, or better, two sheets of clean plywood or particle board to tack into if done over a nice floor.
There are many sources for how to loft, but basically, each view of end, top, and side are divided into spaced slices. Sometimes, diagonal lines are also included. Each view shows the crossing points (intersections) of all views. The completed lofted drawing is full size. Every measurement used to create the lofted drawing is shown in the table of offsets as a height from a baseline below the boat or a distance from the centerline, or from one end of the boat, depending on which view. Think of that as the zero line. That's what the figures in the table mean. The measurement system used will be shown. Usually, in the USA, the system is in feet, inches, and for example eighths or sixteenths, such as might be shown, 1-2-5, which would mean one foot two and 5/8 inches if the last figure is denoted as eightths.
That would be the distance from the zero line in one of the several drawings.
Lofting allows correction first, to "Marry" all the lines of all views by adjusting bending battens to fall on crossing points rather than trusting your measuring or the offsets exactness (they aren't exact, but are almost so).
Then, the lofted drawing allows "picking up" the shape of many parts and pieces as well as providing measurements for your building jig.
Look online for a "How to Loft" article or book you can order. There's a lot to know, but it's not rocket science if you're only building a kayak.

Rick Willoughby

12-17-2008, 03:39 PM

Alan
You have done a great job in explaining the design issues.

If I was looking for a camera boat to go on a car then I would certainly consider buying a sit-on fishing kayak in the mix as opposed to setting out to build one. Here is an example of what is available in Australia:
http://www.fishingkayak.com.au/fishing_kayak_espri.htm

I have no idea what could be sourced in Bombay but I expect there would be something similar.

I wonder how the cost of building would compare with buying once you take in all the incidentals like paint, fasteners and even paddle. If the materials can be sought at a good price then you might come out in front but it would pay to make the comparison.

Rick W

alan white

12-17-2008, 06:38 PM

Thanks, Rick. My guess is the gentleman above is interested in the building process as an end in itself, but you're right, the comparison would make sense if dollars alone matter, especially if tools need to be puirchased as well.
Here in Maine, I see a lot of 10 ft kayaks all the time. New, as little as $300.00 USD on sale, which would be hard to beat!
A cheap kayak with good stability might be a box section (simple single chine Greenland type with a one-piece bottom). Two 4-6 mm plywood sheets would probably be enough--- three at most. Tape the seams and seal the rest. Maybe $250? Plus paint, paddle, hmmmm.
Yes, it has to be a labor of love.

messabout

12-21-2008, 02:48 PM

Rick and Alan; you are completely right in that is is more practical to buy a little rotomolded yak than to build one. If Millionswords is set on building while keeping it simple and hopefully economical, then Mike O'Briens Six Hour Canoe could be given consideration. It is a hard chined model with only two sides and a bottom. It even looks pretty good. Two sheets of ply, one 2x4, and four pieces of 1x2 spec lumber is all it takes. And yes an ordinary craftsman could build one in six hours. (not including paint and finish)The only tools required; a saw, screwdriver, a jack plane, and the will to do it. The two sheets of ply even provide enough material to get out the double paddle. No lofting, no sweat. The only parts that are the least bit challenging are the stems. In the case of the stems, your brother in laws, or someone elses brother in laws, table saw will make short work of it. Otherwise one has to plane a lot.

To Millionswords; Lose the bamboo idea. You'll be glad you did if you intend to build other than a skin on frame boat. OK if you are determined, I think that you could build a decent skin on frame boat with a bamboo frame and plenty of lashing. It could be light in weight and retain some of the twisty behavior of a Baidarka. Walrus skins are not a requisite covering material such as used by the Aleutes. The Brits and Irish have built Coracles that way for a couple of centuries. Not with bamboo, but with willow. The Irish do not have bamboo or they might have used it. Multiple chines are not a problem with a SOF design.

millionswords

12-23-2008, 07:06 AM

Thanks Rick, Alan and messabout!

Quite interesting to see more views and replies in the thread.
Bamboo - ONLY driving force is it is cheap and abundant around here.
2. Loosing the idea is not the question. Learning without punching a hole in my pocket is the idea.

I certainly know the complications in making a frame with bamboo. I'm seeing it getting difficult in every step I take closer to building, I'm evaluating the work load vs cost in Bamboo vs Wood frame.

I shall keep the forums updated when I keep moving towards the goal. Nansen some how made it look so simple, there must be a certain trick, that has to be revealed while I ponder for the answers. I shall post it here when I realize the mystery!!

So far I have been planning not to use a strongback, but now I have been visualizing the use of a strongback to hold my frame's first pieces - the Gunwales.

Need to see how well Bamboo reacts to mortise joints, and lashing over it.
Thinking how big (diameter) a bamboo would I require to hold the deck stems and ribs together.

Will keep this thread updated too.

To Alan:

This is the plan that I'm using - Sea bee 13'

http://yostwerks.com/SeaBee13Offsets.html
http://yostwerks.com/SeaBeeMultiChine.html

Rick Willoughby

12-23-2008, 08:04 AM

In terms of boat performance the thing that counts is length first and slenderness second. Fairness and finish are a long way behind and I believe often overstated. These certainly make the boat look nice but do not add significantly to functionality.

I think a bamboo frame has considerable merit. You could even use large section bamboo on the gunwale to improve torsional rigidity.

So if bamboo is abundant and cheap I believe it is a good material to start with. I have already spent a lot of time with different materials and do not consider anything but carbon fibre for my applications these days but that is because of easy of handling and is on the opposite end of the scale to economy. So for an economic build I believe bamboo would be high on my list if readily available.

At one point I purchased a heap of small diameter aluminium tube for a skin on frame hull but did not proceed with it but it was an economic one-off for me. The bamboo would be a good substitute for timber or aluminiun tube.

Bamboo at the right price may enable you to build your boat for less than it would cost for a sit-on kayak. There are other threads here covering skin on frame construction and ideas for low cost fabric covering.

Rick W.

alan white

12-23-2008, 10:38 AM

millionswords

12-23-2008, 12:42 PM

Alan and Rick - thanks for the comments.
reason for choosing bamboo

1. Cheap
2. Abundantly available,
3. Needs less special tools such as motorized saw, draw knife, etching tool etc.
4 and Cheap again.

+ its light weight, sturdy, bends wonderfully, and stays afloat on water.

About the concerns on the Ridges that are found on the bamboo, If I'm able to make the frame successfully, I think I can some how manage to reduce the ridges by sanding and peeling etc. It may be a compromise to test drive my first kayak.

Later when I'm confident about making them, I shall opt to do a Aluminum folding Kayak, which I think I can pull out easily. But the cost of Aluminum and HDPE Plastic would be great for a trial run. All the required material for the folding Kayak is available and I'm constantly making notes for it too.

But my first float would be just under $50 to $60 including the canvas cloth and paint! if all goes well.

millionswords

12-23-2008, 12:50 PM

Alan regarding sea bee - it is a neat little boat, sufficiently can carry a 250lbs as the designer claims. I picked it up because it is a SOF design, and uses un conventional material just like mine.

If i follow most of Tom's guidelines and make some necessary changes in the due course I think I will have a nice frame in hand.

Now thinking of the strongback, and how to proceed.
My first hurdle is to bend two bamboo Gunwales together and join them on the bow and stern to have the first base.

Once this is done, I think I will be off to chisel the mortise for the ribs and deck beams in the gunnel. So I need the gunnel to be large enough, and at the same time not break the hollow bamboo.

Because the sea bee is a multichine design, I'm thinking of not bending bamboo, but employing something like what Nansen does to his Arctic Kayak. Link: http://bp1.blogger.com/_yFfmvdFuhnI/SCdubOiAKxI/AAAAAAAABVc/EwNkpeeJOCY/s400/Bamboo+Interior.JPG

http://bp2.blogger.com/_yFfmvdFuhnI/SCdu0eiAK4I/AAAAAAAABWU/iUTOJMlBx_0/s1600-h/Stowage+Below.JPG

Rick Willoughby

12-23-2008, 03:52 PM

ancient kayaker

12-23-2008, 07:32 PM

I'm unfamiliar with using bamboo for boat construction, so I'll leave it to others to comment. My concern would only be straightness. I would also be careful, no matter what species of wood used, to avoid grooving or otherwise interrupting (by cuts, etc.) the longitudinals, at least to any significant depth.
Thanks for the link to the Sea Bee design. Looks like a good first project.

Alan

Bamboo can be straightened or indeed bent to surprisingly small radii: 10^6.swords has a video showing how it is done. If I could get 20 ft bamboo at all, let alone for $1 I would like to try it out for myself. The nodes are nobbly but are also, in my limited experience, strong points so shaving a bit off the outside to get a fair shape should not erode strength. I am looking forward to seeing how it turns out.

millionswords

12-24-2008, 02:31 AM

Yeah AK,

Today I just returned from the bamboo market, I was surprised to see so many varieties of them, same size but different weights. Some are hollow types some are solid types, green ones, yellow ones. All tall to the length of 22 to 30 feet.

I saw a couple of them as tall as 25 feet and weigh just about 2 KG or so. Feeling them in hand was amazing, and promising. Tall 3 to 5 inch radius bamboo are very nice and not narrowing too much to the tip. Cutting out the 13 feet from the 20+ footers would give a very stable Gunwale.

@Rick, the longitudinal chiseled do not bother the strength of the bamboo, they are surprisingly strong even if chiseled for mitering. This is because of the nodes that give strength to each nodal section.

Every 1ft to 1.5 feet has a node, and so the strength is distributed throughout the pole. I have seen and used bamboo ladders, and they are as tall as 15 to 20 feet, all made from bamboo, and lashing with coconut-fiber ropes. These are brilliant cheap use of bamboo and coconut fiber.

here are some pictures of Bamboo Ladders and how they are Joined!

http://www.emilyreadettbayley.com/images/mirrors/bamboo-ladder.jpg
http://www.symphonyproducts.com/assets/images/Ladder8.jpg
http://www.symphonyproducts.com/assets/images/ladder3_web.jpg

http://www.symphonyproducts.com/assets/images/ladder7_web.jpg
http://farm1.static.flickr.com/56/184745637_7228404006.jpg?v=0
[you can see it is being carried easily on a cycle, its not too heavy. In the background you can see the best Beer avaialble in India, Kingfisher Beer!!] :)

http://farm4.static.flickr.com/3214/2656623383_a590a269ed.jpg?v=0
http://farm4.static.flickr.com/3126/2628454890_fc97d0ca9f_b.jpg
http://farm3.static.flickr.com/2063/2250786024_5b3d505602.jpg?v=1202487760
http://www.istockphoto.com/file_thumbview_approve/2004143/2/istockphoto_2004143_bamboo_ladder.jpg

http://www.bamboocraft.net/workshop/data/523/medium/03_10_20_Bzr_Escola_038_mod.jpg

millionswords

12-24-2008, 02:37 AM

see what can be done to Bamboo in a manufacturing process - http://images.andale.com/f2/122/113/25154637/2007/8/23/manufacturing_process_bamboo.gif

Node removal, sanding and fumigating would be some process i would be interested in. :) - looks wonderful and promising.

This is a small fountain made with bamboo and mitering, it is promising to see how the bamboo is placed in water throughout, and seems it does not bother the wood!

http://www.newzealandwatergardener.com/content.asp?Category=373

Here is a nice joint! - http://farm2.static.flickr.com/1273/1085165710_73e1969437.jpg

millionswords

12-24-2008, 06:02 AM

Okay here goes the idea from today's pondering! and it answers Rick's concerns!

I'm not going to make holes or chisels in the bamboo.

Bamboo can be peeled.
So I intend to cut the bamboo across to about 90 - 95% and then leave the peel to hang.

http://www.boatdesign.net/forums/attachments/stability/27847d1230116256-small-kayak-under-13-feet-stability-img_5958.jpg

The above cut is not made from a Hack Saw, so it is a little amateurish!

This peel is fibrous and can be bent over the connecting pole. Now with the peel bent, start to lash like mad. :) Tight lashing using the right thread will enable a strong hold and no slipping.

http://www.boatdesign.net/forums/attachments/stability/27848d1230116256-small-kayak-under-13-feet-stability-img_5960.jpg

http://www.boatdesign.net/forums/attachments/stability/27849d1230116256-small-kayak-under-13-feet-stability-img_5967.jpg

http://www.boatdesign.net/forums/attachments/stability/27850d1230116256-small-kayak-under-13-feet-stability-img_5965.jpg

http://www.boatdesign.net/forums/attachments/stability/27851d1230116256-small-kayak-under-13-feet-stability-img_5966.jpg

Now the Strong Back Issue: addressed!

I think I was confused with too many articles and pictures on Strip Building and Conventional SOF kayak building! Now that what I do is not conventional, I had to pick up so many ideas from so many other construction methods and cook up a unique one...

The last picture is a drawing I made on paper to show how to proceed without Jigs of Plywood.

In this method, it is a slow process but certainly would work.

The two gunwales are lashed to a Bow piece/Stern first (may be a cross cut miter would help)

Then the first Deck Beam is lashed at the right interval one side at a time, to both the gunwale.

When this is done the gunwale start to take shape, and wont slip, I have shown two beams lashed in the drawing.

When all the beams are lashed, the gunwale will be a fully bent boat shape, lash it to the Stern.

What I propose is to also lash the ribs at this point at the same joints as the beams, leaving the stringer side hanging...

So what you will see will be some thing like that in the drawing..

And then I can lash the stringers to the Bow and Stern, then the hanging ribs should be lashed to it.

This way a strong back is not needed. Only a couple of saw horses to mount the frame for easy lashing height.

Ooof - that was what I wanted to do. Only now I come to a comfortable understanding.

I do not know how this will be numerically correct. It can't be, it must be a very very ancestral way of building the water craft, this is what I can do now, without tools.
I can't imagine how the Sea Bee's numeric would go into this sort of building?
I have started to loft the offset table of the sea bee to poster boards, but still wonder how would that help me?

1) Roughly I can follow the intervals of the ribs, and the beam of the sea bee.
2) I may not have a multichine, though it is possible
3) I cannot have a rocker, though it is possible remotely.
4) Knee Beam could be bent and managed.
5) Flooring can be a bit of plywood strips.
6) No idea about the coaming! - two thin bamboos can be lashed together and coaming made!

What do u people think? Alan, AK, Messabout and Rick?

alan white

12-24-2008, 10:31 AM

I would avoid any through notching of the bamboo. Once you notch it, groove it deeply or put a hole through it you create a stress raiser. You should devise a method of connection that avoids notching.

I expect you could make a good connection with twine and some waterproof glue to keep it together.

Rick

Years ago I built a very resiliant and strong backpack frame of ash. I lashed it with cotton twine that was first immersed in Weldwood waterproof glue. Once dry all was sanded and varnished. The lashings were hard as steel cables and over years never failed. Very snowshoe-like but since cotton (compared to gut) absorbs so well (look at boat decks) it resists rot very well.
Regarding node stick-out: Would it make sense to pad out the sections between the nodes? Maybe using strips of bamboo that are glued on the outer faces after the longitudinals are bent to the molds.

millionswords

12-24-2008, 11:40 AM

Years ago I built a very resiliant and strong backpack frame of ash. I lashed it with cotton twine that was first immersed in Weldwood waterproof glue. Once dry all was sanded and varnished. The lashings were hard as steel cables and over years never failed. Very snowshoe-like but since cotton (compared to gut) absorbs so well (look at boat decks) it resists rot very well.

That is really promising, but how much of thread can I glue - sand and varnish? :confused:

Regarding node stick-out: Would it make sense to pad out the sections between the nodes? Maybe using strips of bamboo that are glued on the outer faces after the longitudinals are bent to the molds.

Will think about it after the construction of frame. When I try it with plastic sheet wrap/saran test I will get an idea of how the nodes stick-out bothers the boat.

ancient kayaker

12-24-2008, 02:44 PM

3 to 5 inch radius bamboo sounds far too heavy for a skin on frame boat; more like what you would need for a small ship. Typical wood sections on boats I have seen are from 3/4 x 1 to 1 x 1-1/4 inches across. If bamboo is at as stiff and strong as the woods commonly used about 1-1/2 inches diameter should be plenty. The strength of the frame comes from attaching several light pieces together: most of the stiffness comes from the tightly stretched skin. If you put all the bamboo you plan to use in a bundle and pick it up you will get an idea of its weight: a skin on frame boat is second only to carbon composite for lightness; if it looks to be turning out more than 20 lb you are over-building it. A heavy boat is not likely to last longer, it gets banged about when handling it on land because it is clumsy. My 12 ft canoe is 20 lb, with no deck, including a rather fancy wooden slatted seat: it is made of 3 mm ply with 1 inch square gunnels, 1/2 x 3/4 wood strips along the seams and a 3/4 sq keel. A skin on frame boat of similar size should be lighter than that, around 15 lb is typical.

I like the idea of using peeled bamboo for binding but I didn't see the advantage offered by peeling the end of the bamboo to create binding threads, compared with an accurately cut joint and separate binding. All it saves is the task of anchoring the binding to one of the bamboo pieces.

If you build the boat "freehand" allowing the two gunnels to find their own shape you are likely to end up with an assymetrical boat rather than a more attactive and functional shape. To succeed you will have to match the opposite pieces of bamboo perfectly. While practice makes perfect you may have to make a lot of boats before you get it right, as you do not have ancestors to show you the methods developed over generations of boatbuilders.

You should be able to make a serviceable strongback as follows:

Take two sturdy bamboo pieces a foot or two longer than the boat will be, lash them together at both ends, then force a short crosspiece between them so they are bent into a kind of shield shape. Tightly stretch a piece of string between the ends. Then you have something strong to attach the boat to as it is built, and a straight line to ensure that is is symmetrical. Once all the parts are attached to the frame and securely lashed it should stay straight without support.

I think your original idea of smoothing the nodes will work without need for padding; from what I have seen the bamboo does not tend to bend unevenly at the nodes. But try it out first: with something unusual it is always wise to experiment first.

millionswords

12-24-2008, 11:40 PM

AK - U the man!

That tightly stretched string in the middle is a piece of cute tip!
Just like the chalking line right?

I saw a video yesterday night in youtube, and it was a bit different in approach like mine. They did not start from the ends, but made a ladder like structure first, starting from the middle beam, and then adding the beams towards the bow and stern. Then before adding the last beam pieces they lashed the ends. This way it would be symmetrical too.

In your idea of tying the gunwales together and then inserting the middle beams would be a little slippery but still work.

AK, You cleared a big doubt on the usage of larger diameter bamboo. I too thought it is unnecessary to use a large bamboo for the gunwales as this should be a light - real light boat. Strength is brilliant in a 1 inch bamboo and ease of working with it is to be considered too.

I tried to carry the bigger bamboo and weigh them roughly, it was light - but bulky! Moving a 13 feet x 2 gunwales lashed would be a problem.

I will check both options - will buy both sizes today the 1 or 2 incher and the 3.5 incher.

Will come back with reviews.

ancient kayaker

12-25-2008, 12:07 PM

The 3.5" sounds about right for the strongback. By bending a pair around a crosspiece you create a stiff base on which to build the boat. It would be convenient to fasten it securely to the ground at about waist height. However a flat surface to build on is convenient, a place to put tools and for small things you may drop to be found. If you do not have plywood for this, perhaps a canvas or tarp cover over the strongback would serve as well.

Regarding bamboo size: boat design and biulding is an evolutionary process in which we build apon the experiences of others. Since there is not much of a dtabase for bamboo boat construction the key is to experiment, observe bamboo use in other areas, compare that to wooden constructin in the eame areas, and be prepared to make mistakes!

ancient kayaker

12-27-2008, 01:42 AM

I have done some research on Bamboo using the Internet. There’s not much detailed information out there but these are the basics:

Strength is proportional to density (like most woods). I have not been able to obtain any specifics.
Stiffness: no data found.
Structure is very different from wood which has cells: bamboo is essentially a composite of fibers and lignin, a natural resin. Lignin is a thermoplastic which is why bamboo can be bent using heat. As far as I can determine the only reason to use water in the process is for rapid cooling and to prevent charring, so steaming should have no advantage apart from temperature control.
Density is high, specific gravity is about 0.95: compare this with oak at about 0.75 and cedar at about 0.4, spruce about 0.5. Bamboo is hollow: based on samples I have seen and handled the hole is about ½ of the outside diameter or 1/4 th of the cross section, reducing its average density to about 0.7 SG, similar to oak or ash.
Resistance to decay is moderate to good, as far as I can establish. It should be protected like most woods, especially the end grain and hollow ends, but the natural enamel of the skin is very hard. Older bamboo (age when harvested) is more resistant.

Use in a canoe is discussed first as I have more familiarity with wood canoes than with wood kayaks.

The 4 most important considerations in my opinion are strength, stiffness, weight and ease of use. With no strength or stiffness data, but it is probably safe to assume that it is at least comparable with durable hard woods. Samples I have handled seemed lighter than hardwood (maple) doweling of comparable diameter and less stiff in proportion, presumably due to its hollow nature. Its most obvious feature is, it’s round.

In canoe construction wood with a rectangular profile is commonly used, which has several advantages over bamboo. It can be cut to precise dimensions, it accepts screws and nails readily, most glues are designed for use with it, by varying the thickness to width ratio of the wood it is easy to optimize the ratio of resistance to bending in the 2 directions normal to the axis, and it is easy to fasten the skin by sandwiching between two strips of wood.

When using bamboo you can use binding instead of fasteners and glue but binding can be stabilized with a coat of glue.

You need to match the stiffness and strength of the wood you are replacing with bamboo. As you are stuck with using round section you must match the strongest direction and accept the unwanted extra strength in the other direction.

Gunnels: 2 pieces of spruce are typically used with the skin sandwiched between, for a total dimension of 1 to 1.5 sq in. I would use bamboo 1.25 to 1.5 inches diameter here.

Keel: typically a rectangular section 0.5 x 1 is used; I would use 1 to 1.25 inch diameter bamboo here.

Stringers: I have seen typical stringers range from 0.75 sq to 0.25 x 1.25. I would use 0.75 diameter bamboo here. Usually a boat will have 3 or 4 stringers between the gunnel and keel on each side.

Ribs: I have only seen one boat with bent ribs, these were about 0.4 x 0.8 steamed ash: I would use 5/8 to 3/4 diameter bamboo here provided it will bend easily. Steamed ribs are spaced about 6 inches apart. They are usually sandwiched between the 2 pieces of wood forming the gunnel; these joints are structurally important. When using a single piece of bamboo for the gunnel, you must join the ribs neatly to the gunnels. Rather than relying on a simple bound butt joint, I would drill the gunnel halfway through to fit the rib end, possibly tapering the rib to fit in a smaller hole, then bind. If this joint is drilled then it should be made water-tight.

Hull shape: there is a nice looking skin on boat canoe featured in the Wooden Boat magazine numbers 205 and 206 (Nov/Dec 2008 and Jan/Feb 2009 issues), if you can get that in India. The boat is 11.5 ft long with a 28 inch beam. The magazine may sell you back copies or a copy of the article. E-mail woodenboat@woodenboat.com.

Another source of hull design is the Adirondack Museum at http://www.adkmuseum.org/. I bought a plan for the Wee Lassie, a famous boat designed by Henry J. Rushton around 1886. It is a small boat, 9.4 ft long with a 27 inch beam, but could easily be made larger, 12 ft long with a 28 inch beam would be about right for your 220 lb weight.

Skin: 9 oz nylon is often recommended.

Waterproofing: water-based exterior grade polyurethane is recommended by several designers. In the past oil-based paint was often used. The paint should remain slightly flexible; any paint designed for use on wood should remain flexible for several years at least.

For your application in calm waters a kayak has no advantage over a canoe, and will carry a lot more luggage without the complexity of hatches and deck straps. A canoe is typically lighter than a kayak of the same construction. However, if you prefer a kayak, a canoe design can easily be adapted. The difference between a canoe and a kayak is the deck and cockpit. Because of the deck a kayak is usually built lower; when adapting a design such as the Wee Lassie .the top plank could be left off to achieve this. A kayak is stiffer because the deck provides additional bracing. The deck should be strong enough to support your weight. Typically you will sit on the rear deck in order to enter the cockpit so this area should be well braced, a piece of plywood under the skin would be OK.

alan white

12-27-2008, 12:47 PM

I've toyed (mentally) with using abs plastic (that hula-hoop material) to construct a tubular canoe/kayak frame. I don't know if it's been done but the technique would be the same as bamboo. Somehow, it would be lashed. at the ends, wood plugs would be inserted either to seal or to shape the ends.
Abs isn't as stiff as bamboo and it's a lot like poly kayak hull material in terms of resiliance.
I mention this because abs tubing is cheap and universally available. It provides some flotation and cannot rot. It could even be used to augment a bamboo construction, where smooth chines are desired.
Apologies for changing the subject!

messabout

12-27-2008, 03:45 PM

ancient kayaker

12-27-2008, 06:07 PM

No apologies needed for a good idea, Alan! I think it has come up before in connection with rafts or floating docks or some such thing, I'm not sure whether ABS or PVC was considered the best material, the consensus was that wood was cheaper but I didn't verify that.

My previous post contained an error: the skin is not sandwiched between the 2 pieces of spruce comprising the gunnel, it's stapled to the gunnel and covered by the rub rail. In a bamboo canoe the rounded gunnel presents a problem which I did not address. If a flat is made along the outer edge of the bamboo gunnel to accommodate a half-round rub rail it may be seriously weakened, and there will not be enough material depth to hold screws since it is hollow. One method of anchoring the skin to the gunnel that might work would be to glue it, then protect and disguise the glue with a sewn fabric tube filled with suitable stuffing, kapok perhaps or closed-cell plastic foam.

In a kayak the skin can be stretched over the gunnel all the way to the center of the deck for attachment to the king plank, but it will pose the same problem there and in any case it is unlikely that the skin will be wrinkle free.

alan white

12-27-2008, 07:24 PM

I think abs is dirt cheap, while pvc is costlier but a bit stiffer. In other words, longitudinals could be pvc and transverse frames which are extremely curved, abs.
Some woods would be cheaper, maybe, but you have to paint them. Imagine how fast a plastic frame would go together if the lashing system were worked out.
I googled abs kayak frame, but nothing came up.

carboncopy001

12-30-2008, 04:35 PM

I have not sold my 14 foot kayak mold yet, what where you looking to spend on a kayak maybe I can help you with what you are looking for. My mold is also dset up for vaccume bagging, I have been in the kayak industry for over 14yrs mostly with current designs when it was in canada.

millionswords

01-05-2009, 04:59 AM

Alan; you may be onto something with the plastic tubing. I am thinking in terms of PVC plumbing pipe. Cheap, and you can get all sorts of fittings and connectors, no rot, and if kept reasonably well protected from UV it will last for years. The adhesive is also cheap and very affective. It has the advantage over bamboo in that it is continuosly smooth and uniform in size.

I have seen greenhouses and othr small enclosures made of this stuff. It had not occurred to me that it could be fashioned into a SOF boat skeleton. One of the features of PVC is that it will bend into a near perfectly smooth curve. The greenhouse structures are like a Quonsett hut. Just bent into an inverted U shape and the ends stuffed into a hole in the ground. What amounts to purlins or girts can be made useing straight lengths joined with X or T fittings of the same material. I once experimented with that concept in order to make a boat shed. It works.

I think that a suitable ( define "suitable"?) boat could be made in the shape of a punt or spoon ended scow by using available PVC fittings only. No wood or other material required. The main drawback would be weight, no doubt. Using schedule 20 pipe as opposed to schedule 40 could keep weight more reasonable. Cheaper too.

Hi Alan, Messabout and dear AK,

New year wishes to u all, my Laptop crashed two weeks back, and is still bad.
Sorry for the long delay.

I have not been able to even read your posts till today.
Well the thoughts about ABS and PVC have come up before, and they are a tad expensive. I get 2 feet of PVC for $1

13 x 7 = 91 feet needed = about $50 + fittings + glue = way out of my idea.
:eek:

Attached are some samples of PVC kayaks built by others.

I have been thinking of ideas from the Dysons Baidarka and this last PVC kayak, for the Stern and Bow joints. These are neatly made Ply or Aluminum rigs, to hold together the Gunwales, stringers and Keelson.

I like this idea better than to lash all the longitudinal stems together. It would be neat, durable and give it that sharp look.

----
PS: I set out to try doing a scale model to learn the mistakes and prepare for the real material. So a friend and me bought some bamboo strips and split them into sticks of say 0.5 mm thickness.

will post about the scale model in next post.

millionswords

01-05-2009, 05:01 AM

Well in the past days I was thinking of making a scale-model of the kayak,
with the same material - Bamboo. And I started out with work.
[attached are the building photos and the final scale-model, made a canoe lol]

Bamboo splits were made out of a bigger bamboo, and shaved and sanded to avoid split ends.
When i had the enough number of them, I and a friend started out with making the first structure. Here are the steps we followed one by one:

1. First two gunwales were attached at ends with strings.
2. A middle temporary rib was inserted and held
3. then two ribs one after another was inserted and lashed
4. lashing the model gave insight on the larger lashings I might make in the real scenario.
5. now the bow and stern stems went in, lashing over
6. with a semi tight stern and bow stem, the keel was lashed
7. now the stringers went in, made the shape look right, repairing any twists that was visible so far.
8. we lashed the ribs with care, and made sure it is tight between the gunwales and the stringers.
9. When completing the stringers we thought we should have cut short one end, the stern or bow to give it that shape. But nevertheless we finished it with a plastic wrap,

It's too light, but looks neat, still haven't tried the floating test.
Should make some seating pad and then put some weight and test.

Things understood in the process:

1.Need saw horses
2. need some kind of strongback
3. what goes first, what goes next, [this scale-model saved a lot of trial and error]
4. How bamboo behaves, to bending, cutting, peeling, rubbing, etc
5. Greatly gave an insight on lashing with and without wax, we waxed the last few ribs.

The scale-model metrics:

LOA: 73.5 cm
Height: 23 cm
Width: 20.4 cm

What do you all think? Will it float? still to test it out :D

alan white

01-05-2009, 12:29 PM

Hi Alan, Messabout and dear AK,

New year wishes to u all, my Laptop crashed two weeks back, and is still bad.
Sorry for the long delay.

I have not been able to even read your posts till today.
Well the thoughts about ABS and PVC have come up before, and they are a tad expensive. I get 2 feet of PVC for $1

13 x 7 = 91 feet needed = about $50 + fittings + glue = way out of my idea.
:eek:

Attached are some samples of PVC kayaks built by others.

I have been thinking of ideas from the Dysons Baidarka and this last PVC kayak, for the Stern and Bow joints. These are neatly made Ply or Aluminum rigs, to hold together the Gunwales, stringers and Keelson.

I like this idea better than to lash all the longitudinal stems together. It would be neat, durable and give it that sharp look.

----
PS: I set out to try doing a scale model to learn the mistakes and prepare for the real material. So a friend and me bought some bamboo strips and split them into sticks of say 0.5 mm thickness.

will post about the scale model in next post.

Thanks and Happy Holidays back to you.
i wonder if the price of plastic is cheaper here in the USA. Any case, interesting, and thanks for the photos.

Alan

ancient kayaker

01-05-2009, 01:32 PM

Alan: I think the price of money is cheaper here as well! And Millionswords gets bamboo very cheaply. Frankly, I would love to experiment with bamboo but here it is simply not available in the necessary sizes and quality and would be quite expensive, I suspect, to import.

Millionswords: way to go with the model; as I mentioned earlier you can learn by doing especially when venturing into somewhat new terrritory. The pictures of the PVC kayak with the ply frames is precisely what I envisaged but using bamboo instead of PVC tubing. Note the attractive lines of the PVC frame, due to the uniformity of the material.

If ply is in short supply or costly you do not need a lot of it; it is most useful at the bow and stern to provide tough and tidy stems, and for the frame at the front of the cockpit where it will hold the shape of the boat while you install the ribs. Just drill holes for lashing instead of using screws; this frame will also support the front of the cockpit structure.

As you have discovered, uniform lengths of wood adopt a pleasing and streamlined shape when simply bent around one or two cross pieces. If I may critique your model, the vee-shaped bottom is much too deep in the midships location and in a full-sized craft will result in instability unless it is ballasted; it might be OK in a heavy sailboat or power boat, not a canoe or kayak. The angle of this vee-shape is called deadrise, and typically flattens midships, becoming more acute toward the stems.

As far as the skin is concerned, you will have learned that a little stretch is needed to get a neat appearance. Material that will shrink with water or heat is great. If you are still planning a kayak rather than a canoe as shown for the full-sze boat, I suggest you use the model to develop methods of completing the deck and cockpit, and bringing the skin material to a neat finish over the center stringer of the deck which is called the king plank.

When you do that take a look at other kayaks and note that the foredeck has a pronounced peak or camber to shed any water that comes over the bow and leave room for your feet, but the aft deck is much less peaked and often flat for ease of entry and exit. Reinforce the aftdeck where it meets the cockpit, your weight will rest on this area as you enter and leave the cockpit. Visualize where you will have to put your hands to do that then reinforce that part as well.

I have not built a kayak yet, but everyone I talk to tells me the cockpit is the trickiest part, so it is wise to have some idea how you will do it before you begin the full-sized boat.

millionswords

01-05-2009, 11:07 PM

hi AK and Alan,

thanks for the comments.
I like Alan to comment on the LOA x HB x HAB ratio in the model. is it okay?

I think I will repair the model to get it look like a kayak.
AK - I like the kayak's look and feel. So I will make a Kayak first where my heart is at! For taking my wife along I shall make a Canoe later, when you will be my best mentor! Bad luck that you have not made a Kayak before!

Okay about the repair, I will correct the height to be shorter, shorter Bow and Stern stems, and may be more mid-ribs.

I will keep the cockpit in mind, I know it is a big procedure on its own, just like making a Kayak. Tom Yost has a big big section on making the cockpit, which I will learn patiently.

Today I will repair the model.

ancient kayaker

01-06-2009, 12:18 AM

Just a point: there is not a great deal of difference between the small, one person canoes designed for use with a double bladed paddle, such as I build, and a kayak. Most canoes are two seaters, but you can also make a two seater kayak.

For lightweight single seat boats much of the difference is above the water line. My canoes have somewhat more freeboard than a kayak to keep out the water because they lack a deck. Underwater shape, seat position, paddling arrangements are substantially the same.

I plan to build a canoe called the Wee lassie to its original, classic 1893's lines. Later I may build another in kayak form, extending its length, reducing height and adding a deck and cockpit. The underwater lines will remain more or less the same however.

It's called convergent evolution; we are both looking for the same thing and will likely end up with very similar designs even if our construction methods differ wildly.

millionswords

01-06-2009, 01:30 PM

I thought Canoes were a little taller than the Kayaks. and the seating differed.
And there are no Mid Ribs in a canoe!! wow that means lot of strip work!

Well that apart, I cut out my Cross-Sections just now, all the 5 of them from the seaBee offset table.

Looking nice. And looks like I already have the shape!

1. I wonder how high will it be, the tallest of the cut cross sections were just my hip high. Will I be letting water inside? - scares me a lot! I don't want a wet Kayak errr!

Every thing else looks fine, I must either use these to make my ribs using bamboo mounted on some sort of a strong back, or I should get them cut from Ply!!

If i choose to cut them from Ply, I should get ply and go out and get it cut, and drilled too. I do not have a jig-saw nor a power drill. I have seen table saw at the timber merchant's will that do my job?

Drilling has to be done at some place else, or I should get a cheap power drill for this purpose, and it will be an addition to my tool kit!

Over. back to u people...

millionswords

01-06-2009, 02:36 PM

ancient kayaker

01-06-2009, 02:38 PM

Canoes are indeed a little taller than the Kayaks at the gunnels, typically 4 inches or so for a single seater and perhaps 7 inches for a two seater, but the kayak foredeck is considerably higher than the gunnels. For a two or three seater the seats are about 8 inches above the bottom, that is a larger boat, 30 to 36 inches beam. In a single seat canoe the seat is close to the bottom as in a kayak. Hip-high sounds very high indeed; we may not be talking about the same thing here

It's important to remember that a typical kayak or canoe sinks no more than 4 to 5 inches in the water fully loaded, so they seem very low. If you're not used to a kayak, it is hard to believe it will support you.

For cutting the outside of frames virtually any hand or power saw will do provided it is sharp and has fine teeth suitable for plywood. For the inside, the best tools are a drill and a handheld power jigsaw; you can drill a hole close to the cutting line and then run the jigsaw around the line, it's quite easy. If you can get a power jigsaw practise a few times on scrap first.

Without a power jigsaw a bow saw will do very well, a bit more time and effort, and a really sharp keyhole saw would also work but slowly. Even a coping saw can be used if you cut the outside first and set the blade to cut sideways, but be gentle as the blades are delicate. Neither a bandsaw nor a table saw are much use for this kind of work.

There are so many readily available and cheap power tools here in North America that it is hard to advise you as I don't know what you have there. Many years ago in the UK I had a rich and friendly neighbour who was very obliging! Perhaps you can rent a handheld power jigsaw for a day.

alan white

01-06-2009, 09:14 PM

[QUOTE=millionswords;246867]hi AK and Alan,

thanks for the comments.
I like Alan to comment on the LOA x HB x HAB ratio in the model. is it okay?

I see it's about 3.5:1 length to beam. What matters is the waterline beam, which is a bit of work to calculate, requiring an accurate measured set of drawings. To produce drawings you have to start with an underwater midsection (depth and shape) that comes close to producing your target displacement given the waterline length and beam.
All of this involves a knowledge of what CP (coefficient of prismatic, or fineness of the ends) is desired first, then using that to produce a rough displacement figure (later refined if desired by calculating several sections independantly)...
So unless you can do this, the best alternative is to use an existing design, which I highly recommend.
The 3.5:1 waterline beam/length ratio is a bit extreme. But if the waterline beam/length is more like 4:1, that could work on a short boat. The problem is that your model's dimensions mean nothing--- they say nothing of the actual boat. For example, youe model's ratios might work on a 9 ft kayak, but would be ridiculous on a 18 ft kayak.

millionswords

01-06-2009, 10:00 PM

thanks Alan. Understood they mean nothing!

AK,

I have a Bow Saw and a Coping saw(fine tooth).
I guess it would take ages to get that right with these.
There are a few places here, where we can get the wood cut to desired shape. They have proper tools to do it right. I shall not bang my head over this matter then till I have right tools. All I need to do is to stencil my poster-board pieces to a plywood (marine grade?) and take it to the cutter. I will have cross-section frames then.

Will start thinking about the strong back next.

alan white

01-07-2009, 01:12 AM

Millions, you must get yourself a good saw. A simple 10 tooth per inch hand saw is what you need, and old ones (the older the better) are almost always better than new ones (though they will probably need sharpening, and make sure the saw is straight). A hand saw will cut a very straight line, unlike a bow or coping saw. It is better to pay for a sharpening than to pay for cutting job.
Another good saw is a Japanese hand saw, which you pull rather than push. Good for most woods except plywood, which will dull the teeth in no time.
They cut straight and leave a very thin cut, and would be perfect for bamboo, for trimming parts and pieces.
If you can afford a power tool, I'd suggest a jig saw for cutting curves fast. The nice thing is that you change blades and there are a hundred different types of blades avaiable cheap, which are used to cut very tight curves or pretty straight cuts as well, and metal, plastic, or almost any material.

Alan

millionswords

01-07-2009, 03:00 AM

that is encouraging Alan.
Will procure a hand-saw, guess my friends, brother or father must have one.
Will try my hand and let u guys know!

robherc

01-07-2009, 08:38 PM

Neither a bandsaw nor a table saw are much use for this kind of work.
Hmmm, I'd think a bandsaw COULD work perfectly well for this, with the right blade. I actually managed to cu 2-inch tall letters (the whole alphabet) on a bandsaw once...painted 'em up & gave 'em to a younger cousin for learning toys... Anywise, the bandsaw would have to have a fairly narrow blade on it, and 10^6sword would have to have ACCESS to the bandsaw, but it seems a viable option.

I have a Bow Saw and a Coping saw(fine tooth).
I guess it would take ages to get that right with these.
That sounds like a viable way to me...I'd recommend hacking out the rough shape (just don't get too close to your lines) with the bowsaw for speed...then trim it up nicely with the coping saw.

A simple 10 tooth per inch hand saw is what you need... . A hand saw will cut a very straight line, unlike a bow or coping saw.
Alan, Unless I misunderstood his intents...he is wanting to cut curved surfaces here. A had saw is great for straight, but isn't worth diddly for cutting out the letter "C". I think the coping saw/bow saw are his best bets there, short of procuring a jigsaw or reciprocating saw (not a sawzall, the bench-top ones) that is. I could be wrong, but that's the impression I got from his post.

ancient kayaker

01-07-2009, 10:14 PM

Hmmm, I'd think a bandsaw COULD work perfectly well for this, with the right blade. I actually managed to cu 2-inch tall letters (the whole alphabet) on a bandsaw once...painted 'em up & gave 'em to a younger cousin for learning toys... Anywise, the bandsaw would have to have a fairly narrow blade on it, and 10^6sword would have to have ACCESS to the bandsaw, but it seems a viable option.

The problem with using a bandsaw is cutting the inside edge of a closed shape, as the frames have internal holes for lightness and to accommodate body parts.

Alan, Unless I misunderstood his intents...he is wanting to cut curved surfaces here. A had saw is great for straight, but isn't worth diddly for cutting out the letter "C". I think the coping saw/bow saw are his best bets there, short of procuring a jigsaw or reciprocating saw (not a sawzall, the bench-top ones) that is. I could be wrong, but that's the impression I got from his post.

Actually the hull is hard chine so the frames are made up from straight edges. However, the hand saw won't cut the inside line.

millionswords

01-07-2009, 10:56 PM

I have to cut something like this.
This is not off the SeaBee but just like it.

robherc

01-07-2009, 11:35 PM

hmmm...ok, I was thinking canoe....where your frames would be fairly simple "C" shapes...so my last post may have been a bit misguided.

Best scenario:
1. Cut out rough outside shape with handsaw, circular saw, or table saw
2. Smooth out outside shape with coping saw or jigsaw
3. Drill holes at "corners" of inside cut
4. Cut out inside opening with coping saw & bow saw, or jigsaw

Seem like that'll work for you?

alan white

01-07-2009, 11:48 PM

More than one cutting method is required. A lot of different saws make work easier and more accurate. I can't over-emphasize the value of a power jig saw. A good one costs a lot here ($159.00 US for my Milwaukee) but you can also buy a cheap one that will do the job nicely for $50.00 here.
Good quality non-electric saws, whether coping saws, handsaws, keyhole saws, jap pull saws, or back saws, are actually MORE costly if you need several to do the many types of cuts required to shape the frames shown in the pictures. Yes, you could buy low quality saws, but they will be a big disappointment and are usually not even worth sharpening.
The advantage of an electric jigsaw lies in the many choices of blade types you can buy (narrow blades for tight curves, wide for straight cuts) and the price of the blades is very reasonable. Especially when a kit of blades is purchased, the price per blade is very cheap even with good steel.
If I had to choose one saw to build a boat, I would choose an electric jigsaw without hesitation.
I don't know which brands are available in India, but it's best to stay away from any power tool you can't find tested somewhere on the internet.

ancient kayaker

01-07-2009, 11:57 PM

One other thing on buying a jigsaw; if you have a choice get one that has an orbital cutting action.

Squidly-Diddly

01-09-2009, 02:16 PM

I paddles just fine and feels safe and stable.

Maybe I'll post pics if I can figure out how to do that in this site.

Last time I built a fabric over frame kayak with white PVC piping and nylon, I was surprized at how much the water bowed in the skin. I then covered the skin with one layer of fiberglass and resin and that was a huge improvement.

Many short and stable kayaks(designed for fishing) use a 'twin hull' design where the center is concave.

ancient kayaker

01-09-2009, 02:29 PM

My first kayak was 9.3' x 30", and very stable. Not very fast though. You can post pictures by clicking on "Go Advanced", then click "Manage Attachments". That will open a popup that will enable you to browse, select and upload files.

messabout

01-09-2009, 05:21 PM

I have been watching this thread since its' beginning. As it progressed, I gathered that the desire is: build a small boat capable of carrying camera equipment and a paddler, while operating on canals and other protected bodies of water. The boat must be light, easily transportable, convenient to store, very economical construction, can be built with very few tools, can be built by a person with limited construction skills. Does such a boat exist??? Yes! A coracle is such a boat.

Coracles are sauce ror dish shaped boats that were probably one of mans earliest inventions. Archaelogical evidence dates them back as far as 8000 BC. They were and are used in locations throughout the globe. In Iraq, they are called Kodru, In the British Isles they are Coracles, In India they are called Parisal.

The Parisals use split bamboo for framing. It is woven into an intricate pattern to form a somewhat hemispherical frame. In the past, water buffalo or ox hide was used for the skin. These days sack cloth is used and it is waterproofed with bitumen. See www.wikipedia.org/wiki/bitumen. Parisals are still in use in southern India as a tourist ride on the river Couvery. A Vietnamese Coracle is also made largely of bamboo with some rattan. The waterproofing is made from bitumen mixed with ox dung and resin from the Rei tree. (the ox dung statement is not a feeble attempt at humor. That material apparently has some useful qualities for such a purpose). These boats are still in use along the coastal region in places like Nha Trang on the river Cai. In the war, these boats were actually used to lay mines.

Such a boat was used by the mother of Moses when she layed him in the bull rushes. At least that is what is said in the christian bible...Exodus chapter 2 verse 3.

The Coracle is of such a modest weight that one carries it on his back. They usually have straps of some kind into which you put your arms while carrying the boat. The single thwart usually has a slot or hole in it. One end of the the paddle is placed in the hole and the other end extends over the shoulder of the person carrying the boat. That makes a handle of sorts, to control or balance the boat.

Small Coracles are a little over one meter in diameter. There is much freedom in deciding the size to build. Large ones are said to have been capable of carrying 10 or more people at river crossings and such.

Tibetans use boats of the Coracle type and general construction, to navigate in some of their far removed locations.

These boats were used by native Americans of the Hidatsa and Mandan tribes. They lived on the northern plains of this continent. There were very few trees in those laocations so they did not build dugouts or birch bark canoes. They simply used what they had to work with. Willow perhaps. The Coracle of America was called a "bull boat". It was the only one of its' type to use animal hide with the hair on the outside. That method seemed to make a hydrodynamic difference. Of course the builders were unaware of that kind of science. They just knew that it worked a little better that way. The tail of the animal was left in place on the bull boat. It was a convenient handle for dragging the boat up on the beach and it probably was trailed astern when under way. No doubt the tail helped the boat track better.

These boats are still in use for fishing in some of the coastal villages of Wales. There are tales that claim these boats have crossed the English channel. ( If true, I suspect that the paddlers chose their weather carefully)

A Coracle museum is located in the Welsh village of Cenarth on the Tefi river. See: www.coracle-center.co.uk Millionswords might not choose a boat of this type, but a few of us might be interested in exploring the capabilities of this ancient watercraft. Who knows? maybe we might even build one. Sounds like fun to me. Those of you who know about the designs of Platt Montfort will get ideas about geodesics and modern coverings.

ancient kayaker

01-09-2009, 07:50 PM

Messabout: thanks for an interesting post. I was under the impression that the coracles of the UK used animal skins but I could be wrong. This link has information on coracle building as well as other small boats-
http://home.clara.net/gmatkin/freedes.htm
Propelling a coracle is a challenging task, but I have seen an expert move one of these ungainly craft at a surprising clip.

millionswords

01-10-2009, 12:16 AM

:) Messabout!!

Certainly I wont choose the Parisal.
Why?

1. Not stylish :D
2. It is not steerable with less effort,
3. It wont stay stable without effort, needs constant correction
4. I will get a headache sitting on it, even with an expert propelling it. Rotates the hell out of you :))
5. It is not easy to build like you might think.

Building a parisal:

You might need hundreds of strips of bamboo, that is sanded on edges to avoid small bristles. And combing them together without gap needs an expert with experienced hands. Lashing is minimal, actually there is no lashing in some parisal i have seen, it is combed in such a manner it don't need lashing. It is a piece of art in itself. Then the outer fabric is sometimes tarp, canvas tarp, or just jute bag, hemp cloth, and covered with " tar" which is bitumen as messabout mentions. Very cheap to make indeed, and lasts freaking long! easy repairs, no or least maintenance needed. It can capsize easily, and usually people with experience can recover form capsize in no time.

I have had some real good time on parisals, and its fun. Will try my hand in propelling it sometime when I see it next.

Not for me - messabout!

http://img390.imageshack.us/img390/1822/img3176wx2.jpg
http://lh5.ggpht.com/_m_p3RoutWkw/Ra5tzhX0pWI/AAAAAAAAAec/EnW5Fnt1p6U/DSC02791.JPG
http://en.wikipedia.org/wiki/Parisal

ancient kayaker

01-10-2009, 10:44 AM

One is truly a work of art, the other an article of work! What else will I learn on this forum?

Occasionally when I leave a dock I need to work out sideways to avoid hitting other boats nearby. I use a sculling stroke to do this, it is surprisingly powerful once I got the hang of it, and much more stylish than shoving off against the dock! The underwater path of the paddle is a figure of eight. It is awkward to do with a double paddle however. When I sneak up to wildlife with a camera and canoe I use the indian or underwater stroke in which the paddle does not leave the water so less motion is visible to shy waterbirds like herons, and no splash is audible. The underwater path of the paddle is somewhat circular.

I assume the skulling stroke is used for the parisal and coracle. I would not like to have to do that for an extended period though, very tiring. Also if I had to lean forward to use the stroke at the bow it would be rough on my back.

1E6swords: how is the boat coming along? I noticed that the model had frames made of short, straight pieces, does that mean you have given up on bending bamboo? I think that would be a pity as it could make for a very elegant boat.

millionswords

01-10-2009, 12:36 PM

hi AK,

Yes. Not going to heat bend the bamboo.
I thought it would be good to heat bend a strip of flat wood, but not a cylindrical bamboo.

And more over the heat bend will not give hard chines for me.
The plan is to make a hard chine kayak. Even strips split form a larger bamboo, bent to make ribs wont work for a hard chine.

I'm following the Johansen Kayak building, which was used by Nansen in his Fram Expedition. Fram171 is the plan I try to replicate.

Still options are open, I keep thinking of a plywood cross section, but might just do it like Johansen and Anders Thygesen (norway).

Will get back to you with some pictures of materials procured in few days.
Managed to get a 15 foot bamboo, 40mm in diameter, almost same dia till the 13 feet length.

Others in the market were too thick or brittle, expecting to see new bamboo in the market in the next few days. Will visit again and check for the right size and length. Once procured, work will start!

A power drill, cope saw, hand saw, bow saw and a few chisels are in hand for tools. Guess I wont need all of them here, but this is abundant tools for this method of construction.

I have roped in a friend to help me out, we will be working on week ends form now on. Lets see how it all turns out!

messabout

01-10-2009, 02:43 PM

O.K. Millionswords I agree that the Parisal might be a bitch to paddle in a straight line. And, indeed they are neither as stylish or as efficient as a decently built kayak. Some of the Coracles were not round but somewhat more boaty in appearance. Were I to build one, I'd surely try for the kind that is longer than it is wide. It seems that neither of us are going to build one of primitive things.

You must have done some good research in order to find descriptions of Nansens boats. Many people are not even aware of Nansens exploits and his incredible dedication to survival in the Arctic. He was one tough dude.

AK, have you experimented with a Yuloh for sculling? It is a marvelous propulsion tool and it can be used for long periods without excess fatigue. It is not a prime candidate for kayak propulsion because the user usually stands while sculling. Talk about sculling, you ought to see 9 year old Bahamian kids scull Abaco dinghys. They make the boat go fast while making it look absurdly easy. Some of the dinghys do not even have notches or yokes on the transom. I wish I could do that.

millionswords

01-10-2009, 09:40 PM

Messabout,

If that is what you feel, not re-building a parisal, picking the idea from it.
Yes that is doable, at the cost of some serious knitting work, we can make something like a strip-built Kayak.

With some Lofting from a decent Offset table, we could start with the knitting of the hull (no gunwales at this point) and once the knitting is over, few long strips of bamboo can be lashed together as gunnels and the rest is history!

Hope these pictures make the above clear:

http://www.modelboats.co.uk/news/Images/Cor20Aug08_001.jpg
http://www.nancarrow-webdesk.com/warehouse/storage2/2008-w30/img.278893_t.jpg
http://oziahz.tripod.com/blog/BasketWeaving.jpg
http://www.theartplacetoday.com/sites/r_a_hansen/_files/Image/Basket%20weaving%20012.jpg

http://images.pictopia.com.edgesuite.net/perl/get_image?provider_id=320&ptp_photo_id=afp:862862&size=500x500_mb&re=1&m=1173485448.0
http://www.foei.org/en/get-involved/photo/gallery/51.jpg/image_preview

What you above are all basket making with bamboo strips. There are made in circle shape, what messabout proposes was to make it little longer, thats what I see from the river-Teifi shots from wikipedia. [http://en.wikipedia.org/wiki/File:Coracles_River_Teifi.jpg]

If we can manage to hold the mold in proper shape with some technique, we can build a Kayak in this principle, though the bottom of the kayak would be heavy, if closely knit!

Waterproofing with Canvas, painting, fiberglassing the bottom all can happen as desired! May be I would add a stringer to the sides and a keelson?

ancient kayaker

01-10-2009, 11:38 PM

Go for it MS: and you will need all those tools, I'm betting. Remember sharp tools use less forces so they are much safer than blunt ones, just in case you are inexperienced at working wood. Also, no reason why you can't have both ply and bamboo frames.

Messy: I hadn't heard of the yuloh and I thank you for the information. I did a net search and it is an interesting idea; it seems to be optimized for a standing sculler but can be adapted for ue in a coracle/parisal I imagine.

millionswords

01-11-2009, 01:06 AM

hi AK,

I can have both ply and bamboo, but Ply beats my budget.
When using Ply I need marine ply. Which is expensive and not my kind of budget for the frame at this point. More over, ply makes building work easier, but takes more to get it cut, and drilled etc. Also I want to make it as traditional as possible keeping the challenge involved in it. Just like the Johansen Kayak, I want it to be a replica in my adapted design.

Once this is done and a success, I would be making two or more boats for friends that has to go company with me. During these building a composite off Ply cross-sections and bamboo will be employed. There is scope for improvement always!

This project - till frame is done and saran wrap test is over will be a prototype test for me. Once that is done, I might think of investing on ply to make it look better either! Lets see first how things turn out!

ShagRock

01-15-2009, 08:56 AM

This is a fascinating thread! Bamboo was used extensively in boats and ships particularly in countries in southeast Asia, India, Indonesia and China etc. Extensive sea trade was highly developed in ancient times. paraws, proas come to mind. I don't where I found this photo of the lovely white canoe, but it may be in India??. I believe it is a SOF canoe with Bamboo frames (please correct me if I'm wrong here) - note the black burn chars on the ribs from heat bending. Also, neat use of small blocks as separators to make the lashing easier. For comparison sake, I included its western cousin:)

Bamboo is poor for nailing, but your ladders were interesting. What if the kayak stern was an triangular piece of wood (or some shape) that had holes drilled in the aft side to receive the ends of bamboo stringers. Glue them tight! Bamboo also has good flotation potential.

Also, would it make any sense to look at monofilament linefor lashing - it's now being used in some strip-plank boats to avoid dents in the wood from edge-nailing. Real curious to see how you make out!

Newfie

millionswords

02-03-2009, 10:33 PM

Hi Ak, Alan ans Messabout...

I dunno if this is the right section to make the updates for the building WIP.
Any how as this is where we discussed a lot about the kayak, I post here.

I started to buy tools and hunt for bamboo poles one by one, and collected them over the past few weeks, ad mist other work. I bought a Power Drill and some saw, wax, thread etc etc. When I thought it is all what I needed, I started out to put things together, and here is what I did yesterday afternoon.

1. cut miters for the poles on the stern side, joined them temporarily with rubber tube strings.
2. inserted a temporary stringer in the Half-Mark and drilled it to let the string go through, tied it in place with Hemp-String.
3. now I joined the bow side, again with rubber tubing.

The bow side has the sleeker side of the Bamboo pole.
As I searched for bamboo poles, I found either they are grown crooked at the top or at the bottom, and only very few about 50 in 1 grow straight from the bottom to top in a almost straight line. I found some grow like a big curve of about 17 feet tall. I picked one of these thinking they will any way be bent, so the already present bend would help. But seems it proves wrong, because I need the poles to bend evenly.

More over in yesterday's exercise I learned how a inset infected bamboo would behave and look., partially green, partially yellow and pale in color, partially patchy and very uneven colouration. I worked hard on a pole and it broke after a few minutes of bending and lashing.

I have to replace the left side pole with a much straighter stern side. Will look for some in the market today or so.

1 doubt.

I happen to notice the stern side with the ROOT side of the bamboo would grow more heavy as I build the kayak. What about the weight ratio between the Bow and stern?

Should i reverse the bamboo direction so as to place 1 root on either side?

Looking forward, to hear from you guys!

MS

alan white

02-03-2009, 11:31 PM

Weight difference between bow and stern will not be enough to notice. Please keep up the photos--- it's an interesting project to watch, and no doubt useful to others who will be working with bamboo.

robherc

02-04-2009, 12:15 AM

I agree with A.W. ... and even if it is noticeable, a slight amount of bow-up trim shouldn't hurt you much (at least not nearly as much as the opposite would).
Also, I think this is the perfect place for you to post updates. Keeps all the info. on this project organized :)

millionswords

02-04-2009, 05:03 AM

Oh k,

Weight difference might be very little, as the bamboo dries, it will be least noticeable. But I can balance it with root to tip; root to tip combination, if you people think it is necessary.

Sure will keep updating the progress here in this thread, this thread has helped me decide on many things while planning, and I owe this to the thread and forum.

Thanks for the support robherc, welcome aboard to the Bamboo Kayak project!

Have you guys noticed this little zig-zag bend in the stern side here:

millionswords

02-04-2009, 05:38 AM

Here is the set of Deck Stringers getting ready.
I might need to attach two bamboo sticks to achieve the knee bend or employ some other method. Any ideas welcome...

Thygesen made it all look so easy!
Here is his Knee Bend Stringer in the last picture (http://www.boatdesign.net/forums/attachments/stability/29006d1233743871-small-kayak-under-13-feet-stability-dscn2246.jpg)!

----------------------------------

Update: I went out to get some ply and cut some Jigs out of them so that it can hold better than the rubber tubes.
It worked just fine, will update with pictures of how it is installed 2morro.

Now will post the Jigs and how the deck stringers are cut and ready for lashing.
If time permits, I shall drill holes and lash them tomorrow, and hopefully the deck will be ready by the end of day!

Here are the pictures from todays work...

ancient kayaker

02-04-2009, 12:18 PM

It's nice to see you making progress. I would suggest keeping the root ends together at one end of the boat. There's a trade-off for each end.

You can put the root ends towards the bow for strength. That would tend to make the stern portion curve more than the bow causing the maximum beam to shift aft, which results in a faster boat.

However, when carrying kayaks I find the bow always wants to hit the ground because the cockpit is behind the balance point and putting the root ends towards the stern would compensate for that.

Your choice, I don't think it matters much unless there's a huge differnce between the 2 ends of the bamboo, in which case it might be wiser to splice them to get a more even distribution of stiffness.

I think you should try out the heating method for bending bamboo, using it to straighten the kinks that some of the pieces seem to have.

Keep posting pictures as we are all learning from this.

millionswords

02-04-2009, 10:29 PM

AK,

Splitting the bamboo will expose it, and treating it will become mandatory.
Will Keep this in mind, once some portion of the deck is set up, I will make sure I check if the Bow and Stern are some what balanced, with various methods to compensate it.

What I have in mind:

1. Join the root ends, make the Gunwale.
2. Join the Root ends reverse it and make the stringer portion,
3. Reverse the root end and lash the Keel

Which will balance the overall weight.
As bamboo dries, the weight factor will balance itself to a certain extent which will help me a bit too. So building with Gunwales reversed to the Stringer poles would do the job.

Will update as I progress..

ancient kayaker

02-04-2009, 10:50 PM

Sounds OK, but I did not mean split I meant splice which is a method of joining 2 lengths of bamboo. I think that a scarf joint would work, that would involve selecting 2 pieces of bamboo to be joined together, cutting the ends at a fine angle, perhaps 1 in 10, and then joining them either with glue (epoxy suggested) or lashing them together. If they are lashed it might be a good idea to ensure they do not work apart, by drilling a hole across the joint and inserting a dowel. However, if the bamboo is long enough you may not need to do that.

millionswords

02-05-2009, 03:35 AM

Oh, K

That way eliminating the uneven bamboo issue.
Well, Will keep that in mind, I'm going ahead with what ever the single bamboo length offers. Dunno how good will a scarf joint work with bamboo, I have seen Wood Scarf joints, that stay goo enough. But Bamboo being fibrous, unlike wood, will give way for peeling over some time.

Updating now with the progress made this morning, in the past 3 hours.

1. Cut the rest of the deck stringers.
2. Drilled holes in them,
3. Attached the middle deck stringers, with waxed hemp.
4. Cut the stern end and drilled holes, lashed them with hemp string.

Todo: attach the rest of the deck stringers, and have a look at the finished deck side frame!

millionswords

02-06-2009, 08:40 AM

Issue1:

http://www.boatdesign.net/forums/attachments/stability/29000d1233717824-small-kayak-under-13-feet-stability-img_6334.jpg

If you look at the image above,
When I try to hold the two miter-cut ends there is enormous elastic strength from the bamboo, and hence i don't get to join them right.

As compared to what Thygesen has achieved, what I get to see is pathetic. I'm doing it all alone, dunno if that is the reason, will get help from a friend on Saturday, shall update after I do so. Meanwhile, any ideas welcome.

ancient kayaker

02-06-2009, 10:44 AM

Can you fit a dowel into the center hole to help join the two pieces? Also, I can see why a simple scarfed joint doesn't work, you have round elements to join and the scarf joint is intended for flat planks. A scarf joint can bear loads in only one direction and the bamboo has to bear loads in all directions. So you will have to cut the ends straight across. A dowel may not have as much strength of the bamboo. Perhaps the traditional craftsmen have already worked out a method. If not, perhaps a thin sleeve over the joint in addition to the inner dowel will work; it is important to fill all voids with epoxy to ensure that the strain of bending is taken up evenly by the dowel and the sleeve at the same time, or one will bear all the strain and fracture, followed by the other. It would be best if the parts fit well without the glue, so the dry joint has some rigidity, then the glue can be added.

millionswords

02-08-2009, 01:49 AM

Hi AK,

I started to dream about the next project already, a wooden Kayak that is. :)
I checked with the timber merchants, and found the prices to be alright because I may need just very little timber, for the stringers and the ribs. Some what under $20 I can get red cedar some 80 to 100 feet in total length.

Guess working with wood will have less complications, and innovations, and will be a very heartening project. Well that is for later, what I did yesterday was to remove the lashings, and do it all again with more strength and perfection. A friend came by to help me out holding and lashing. Upper deck is done, with all deck ribs lashing with waxed hemp string. [spent about 3 hours]

We will continue today and try to finish the stringers and the hull ribs, need to check is the bamboo poles that I have will be pertinent to the hull stringer. If, it is, we shall complete the lashing of hull stringer, and ribs, and keep the keelson lashing for another day.

Keelson lashing will need a little bit of innovation so as to achieve a little rocker in the bottom, dunno what challenges await me.

I was in the meantime, taking serious consideration for your idea of bending ribs AK, but without making drills in the gunwale we cannot keep it tied in shape. If holes are drilled throughout the Gunwale the bamboo would loose the longitudinal strength and will break in the weakest section!!

Instead of taking the risk, I thought let me continue the building and experiment with this idea at a later time! [what do u think AK?]

I also started to cut flat strips of bamboo, about 1" in width, but they too need to be inserted into the gunwales with grooves chiseled in them, spoiling the longitudinal strength of bamboo. I some how dropped the idea of bending stringers fearing this, and continue to lash the ribs.

ancient kayaker

02-08-2009, 09:29 AM

All high-risk ideas should be tried as experiments away from the hull being built! If lashing will hold the ribs then you can go with that. With wood, the ends of the ribs fit in narrow slots under the gunnel. These slots do not weaken the gunnel to any significant degree because they are in the center of the wood and bending stresses are taken up by the outer layers of the wood. The slots serve to stop the ribs moving around. To avoid weakening the gunnels, the ends of the ribs are usually tapered down to reduce their cross section to allow use of smaller slots. The problem with bamboo is its hollow so there's no center in the gunnel to cut a slot in, and if you taper the rib there is no center left there either. Perhaps a small dowel can be put in the end of the rib which can fit into a small hole in the gunnel. There is not a lot of stress on this joint so the dowel does not have to be large.

millionswords

02-09-2009, 09:50 AM

wonder what should be the length of the Chine Stringer? when mu Gunwales are about 13 feet length...

robherc

02-09-2009, 11:10 AM

I'd start out with it longer than I think I'll need it, bend it in & see how it looks. If it's too long/too much bend, you can take it out, cut some off and try again. Remember, it is always easier to cut a little more off, than to put a little back on! :P

millionswords

02-12-2009, 11:55 AM

I measured and cut my Chine Stringers today.
The gunwale are about 13.5 feet. And My chine stringers are cut at 11.7 feet.
It looks perfect to my eyes, some one suggest if the ratio is fine.

The Height above base for the Kayak planned at about 28 inches, so I'm cutting my Rib Stringer at 10 to 11 inch long, will connect the ribs from Gunnel to Chine stringer and the next set of ribs to chine to keel.

Did not take any pictures today, just cut them and no lashing, will post with pictures when I progress with some lashing.

robherc

02-12-2009, 02:31 PM

Sounds good, can't wait to see them lashed in. :-)

millionswords

02-14-2009, 05:49 AM

Report on day 005

Day 004 went without any lashing or construction, today I had cut some rib and started, but later thought I will improvise on the cut.

I used a hole saw to cut it like a half circle (Miter) to let the bamboo Gunwale and Chine stringer rest on it while I lashed them tight.

It works wonderfully, but I need another hand to help me out, so I'm waiting for a friend to come in. Issues I faced was, the ribs need not be of the same height all along the Chine/Gunwale, so Wonder how I would calculate?

Not resting the frame on a StrongBack is posing me problems, but my space constraint keeps me from making a strongback or may be I'm too lazy?

Need to cut more Ribs, about 16 to 18 of them for the Gunnel-Chine Stringer portion and Miter them all - sounds a lot of work!!

Some pictures of the miter and a test lashing...

alan white

02-14-2009, 12:28 PM

Looking good there million. It's beginning to become a boat.

robherc

02-14-2009, 12:33 PM

Million:

If you're wanting to make sure all of your stringers are EXACTLY the same length, try measuring them all & placing dots to start the drill bit in the center of your hole saw on. This way, you should be able to get them all the same length +/- about 1/8" (3mm) or less.

...Just my $0.02 worth

ancient kayaker

02-14-2009, 01:03 PM

It's hard to tell from a photo but it looks rather tall. It would be a good idea to study a few photos of kayaks to get a feel for the overall shape, which has evolved over centuries.

There are many variations of size, design and style related to use and sea conditions where the style was developed. Because kayaks are so low in the water they are higher at the bow to allow them to rise to a wave. Some have bows that curve well above the rest of the boat; this looks nice but is unnecessary for flat water use.

The gunnels slope gradually down from the bow to midships where the cockpit is located. From midships to the stern the gunnels may rise a little or remain somewhat flat, but the stern is never as high as the bow. The foredeck may be domed or ridged, so water runs off to the side before reaching the cockpit. The foredeck typically slopes up to the coaming at the front of the cockpit then the coaming slopes down from front to back. This allows you to slide your legs into the cockpit. The side decks either side of the cockpit slope down sharply to deflect water and to provide clearance for the arms and paddles. The after deck is very often nearly flat but may have a slight camber to support weight; it is never ridged as you often have to sit on it while getting in or out. The Inuit people used these boats for hunting seal and small sea animals which could be carried on the after deck so it is kept low.

There is a balance of forces as a beam wind (from the side) may push either the bow or stern around, causing the boat to head into the wind or away from it. The higher bow counteracts the paddlers body sticking up out of the cockpit which is behind the center of gravity (CoG). A pronounced tendency to head up or down wind is undesirable, I prefer a slight tendency to head into the wind so if I have to paddle upwind I can concentrate on paddling hard and not worry about maintaining my course. People living where there is a prevailing wind blowing them to shore may prefer otherwise.

The bottom of a kayak is never completely flat although it may have a flat center section. A flat bottom results in a lot of buoyancy low-down which lifts the boat causing the CoG to be too high; this requires a wider boat for stability or it will tend to flip over. Generally the bottom is barely wide enough for the hips, then flairs up and out to the waterline from which comes the stability. Anything that lowers the CoG improves stability, including rocker, which is the convex curve of the bottom viewed from the side.

Here are some good links:
http://www.guillemot-kayaks.com/guillemot/information/kayak_design/kayak_stability
http://www.greenval.com/jwinters.html
http://gorp.away.com/gorp/publishers/ics/how_can2.htm
http://capefalconkayak.com/howtoskinakayak.html

millionswords

02-21-2009, 12:32 AM

here is what it looks like when I test lashed the Chine Stringers.
I had cut the ribs to lash @ 11 inches, it proved to be too high like AK exclaimed, so I made 8 inch cuts and have them ready for lashing.

2. I made sure the only way to keep the Chine Stringers in position till lashing is to lash the Bow and Stern Stems first to the Gunwale and then to the Chine Stringers.

3. Now with the temporary lashing, it helps me hold it in some position without the need for a helping hand[a second person].

4. I'm yet to start lashing the ribs from gunnel to chine

I plan to lash the middle ribs first and then start from either side (bow or stern) and proceed to the center. Wonder how it goes...

millionswords

02-22-2009, 12:09 AM

Update:

I had cut the bamboo culms at about 7.5 inches long, the culms were about 1inch thick in diameter. I drilled using a "hole saw" bit for the Hammer-Power drill and made the miter ends.

The Gunwale and Chine stringer rest on this miter, this rally made things easy and lashing was more nicer. Earlier when I did the deck ridge ribs, I had not employed this idea, with a straight cut the lashing was a big problem and they never stayed tight on the Gunwale. I'm thinking to cut them deck ridge ribs once again and lash them with this miter idea.

The whole structure is a little flexible I feel it will be like this because it is just lashing and nothing else.. [waiting for a friend to help in holding while lashing..guess will make tighter lashes then]

Pictures: after lashing the Gunwale to Chine stringers with the mitered culms the shape has improved, looks little like a boat [atleast to me :) ]

robherc

02-22-2009, 11:50 AM

Hey, 10^6 Swords;

You're right, it IS starting to look a bit like a boat now; looks like the chines are going to be quite hard, but that's ok. I'm glad you found the hole-saw method works so well for you.

millionswords

02-23-2009, 01:01 AM

yes rob the hole saw idea made the whole process a breeze!
I'm now contemplating to employ the same idea for the deck ridges too.
Might work on it now and post pictures soon...

millionswords

02-25-2009, 12:24 AM

Here are some close ups of lashing, and the work in progress..
After some practice with lashing, and getting a right position to seat the frame, I think the lashing is coming a bit better, and holds the frame well. here are some pictures...

sigurd

02-25-2009, 10:55 PM

tight lashing will be stiff enough if you have the right geometry on the sticks.

I don't know what direction of flex is bothering you but you can try to add some diagonal sticks.

1) A cross in the deck,
2) a cross from stbd gunnel to port chine and vice versa,
3) a cross from gunnel to chine on the same side
those are some options.

Is that coconut fiber? are you putting any oil in it?

edit: It is also possible to use cord instead of sticks for the crosses.
edit: with 3) you can force some rocker, which will be good like AK said.

rwatson

02-27-2009, 09:49 PM

You will get a much more rigid structure if you slice the bamboo into say 1" strips, and bend them in U shapes to join gunell, chines and keels together.

Sigurds suggestion of diagonals is valuable - you can run these strips in U shapes that run from the centre frame to either end.

From experience, I would be inclined to use the current shape as a "base" to build an almost "woven" frame of thinner bamboo slices, and not even use the current frame as part of the finished boat. Use thin hemp rope to lash it all together.

Boats have been built sucessfully that way for years in different parts of thw world.

A rough drawing is attached to illustrate some options.

millionswords

02-28-2009, 02:20 AM

millionswords

02-28-2009, 02:37 AM

** --- for my reference ----

--------------------------------------------------------------------------
Here is the list of wood we see out here:

1. Aini/Aangili 595 Kg/m3 [Artocarpus hirsutus, locally called Pala in Tamil, it is the Jackfruit tree most used for boat making in Kerala]

2. Bean Teak - 675 [ Lagerstroemia parviflora Roxb. Kaccaikkattai or Chenangi in Tamil]

3. Jack 595

4. Saj/Lauraceae - 880 [Cinnamon verum, Ilavangappattai in Tamil]

5. Red Cedar - 450 Kg/m3 [Cedrus deodara, this is Indian Cedar, locally called Deodar, Devadaru or Karuppu Tekku in Tamil means Black Teakwood]

Other than this, without any density data, we get Palak, Thekku, Vengai maram, puliya maram, silver oak, Kongu[Sal], Burma teak, Paduk[ Pterocarpus], Rubber wood, beech wood.

---------------------------------------------------------------

rwatson

02-28-2009, 05:34 PM

thanks for the suggestion rwatson, this has been discussed in length previously with ancientkayaker and alan, then we decided to go on with this type of lashing, if this does not give me desired results I would not mind ripping apart the frame and using the 1" strips technique, sure the bamboo strips method would work, but the bend will be "U-shaped" rather than a "flat bottom U". I have to source a jig to cut bigger dia bamboo into strips of same width. [see these Jigs used in Brazil - http://www.bamboocraft.net/workshop/showphoto.php?photo=806&size=big&cat=
]

The splitting and the U shape are things to think about, thats for sure -

I dont think you will achieve the stiffness you need with the current technique. You still have a lot of "infill" to create, in the way of lengthways sections to support the fabric. Doing this in large section bamboo will make for a very cumbersome and hard to fasten structure.

You certainly dont want to have a pronounced U in the bottom section, which would be the case if you bent thinner strips for the framing moulds.

I had better success using very thin strips in longitudinal directions only, bent over frames that were hardchined (small straight bits fastened together). I predict this would give you much better results.

Using strips will make the fastenings way easier and more robust. You can even 'pin' through two or more thinner strips as well as lashing them.- something hard to achieve on bigger diameter sections.

Without a lot of back tracking to find out the reason for the shortness in this design, I cannot stress too highly the advantages of going as long as is feasible. I had to manually carry my canoes up and down a very steep hill for about a kilometre to get to the beach. I started off with an 11 ft canoe.

The final and best solution was a 21ft kyak, made of quite a few 5mm x 7 mm longitudinal wooden strips. It was very light, and when it was in the water, the ease of paddling was phenonenal compared to the shorter versions. You may have storage and transport limitations of course.