Small Kayak - Under 13 feet - Stability?

[alan white]

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]

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]

Originally Posted by messabout

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.


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]

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

[alan white]

Originally Posted by millionswords

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.


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]

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]

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]

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]

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]

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...

[ancient kayaker]

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]

[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]

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]

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]

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!