Proof of Concept

Very interesting clever designs!

For those that have experience with these sectional boats, how does the portage work in practice? Is the boat assembled and loaded with gear at the vehicle and then carried to the launch point? Seems like you would need wheel or at least 2 people. If you assemble at the launch point, that means several trips and you might tie up a busy boat ramps. Same for the storage process, you will lose some time on the water compared to other designs. Not meant in a negative light, just wondered how it is all done...

Porta

 

You must get the ergonomics and function of the boat correct. I would first design the boat with no bulkheads..no sections. Then , since oars are the primary power of a small craft , optimize the layout of the boat to give the oarsman the most power.

Once you got the rowing detail down then Id rig the boat. Two masts sound good..you have two oars. Use the oars as masts. Get the sailing layout correct.

Now you have a good boat...chop it into pieces and protect ergonomics of the layout for sailing and rowing.

I wouldn't worry about the structural location of the joint sections. Any engineering problem can be solved.

Ergonomics is what will make a good boat. The ability to do everything well. Concentrate on ergonomics.

As Daiquiri stated..a dagger board is preferred. Perhaps you could use your rowing thwart as a dagger board ?

 

That is a very draggy hull design. It appears you have room to make the bow and stern sections a bit longer, make a smoother transitioning bow, and open up the transom so it is bit wider and makes a smoother transition from the aft part of the center hull section. IT will give you a bit more storage capacity too.

Better yet, find a hull design that is about the same length as you want, and than cut it up so it nests as you want it.

The use of the chine runners in a great idea for your use, it keeps the center open and simplify the operation of the boat.

Your mast idea is not really viable. Go with a short cantilever mast at your length limit, and than design a gaff rig sail. OR a Gunter rig. Or you might just find some 4 cm dia aluminum tube and make sleeves from smaller dia tube (epoxy into place), like a tent pole.

 

If these are your requirements than you should think again about daggerboard keel, for the following reasons (replies numbered as in the above quote):

1) If you want to find space, you can do it really easily. See this possible arrangement:

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There is enough space in between the sections to accommodate a daggerboard box. It will take some internal space, but if you have ever sailed a dinghy like an Optimist, you'll know that it is not anything to worry too much about. You will not be in that area of the boat during the navigation under sails.

2) The purpose of the daggerboard keel is exactly that: it can be raised or lowered even partially, allowing you to have a control of the amount of keel area you need for that particular windspeed, boatspeed and course.

Besides the above, you have also said that the boat will occasionally be powered by oars. In that case, those chine keels are your enemy, because they will approximately double your boat's drag in the rowing speed range. A daggerboard can be retracted on those occasions, and hence don't add any drag.

Hope these considerations will provide some more food for your thoughts.

Cheers.

 

Thanks people, from the bottom of my heart! I am back at my drawing screen and will post something to address your comments.
Kind regards.

 

More thoughts:

A long boat will row and sail better than a short stumpy one.
You can fit a longer, narrower end section on either side of the daggerboard trunk.
There's no big reason why the daggerboard and its trunk must be on the exact centerline.
There's nothing all at wrong with leeboards.

Speaking of leeboards, there's usually two with the one on the lee being deployed and the weather side raised, changing over during each change of tack. That's customary, but a single leeboard can be mounted in a short "trunk" on one side, as the highly respected Phil Bolger did on one or two of his "instant" boats. I did that on my first foray into sailing with a canoe, because I "didn't know any better" and it worked fine. The trunk just needs to support the board against water forces from either side.

 

Thats very true - on a boat of this size, the difference in 'efficiency' is sooooo marginal as not to be worth worrying about.

Having a trunk in the middle will make low paddling impossible, which would be a tragedy for a kayak like boat, but useful if you need a central seat for rowing.

 

Great point there, it made me think about a possibility to use the daggerboard as a seat when rowing (see the attachment). :idea:

 

I don't like trying to paddle or row on a seat with a hole in it personally . . .

 

Crawler 2

Hello everyone!

It is so nice to read critical comment pointing me in the right direction. I wish there are more like these. I combed replies starting with #26.
I tried to pick up comments, which I organized in form of bullets. Then I tried logically answering them as best as I could.

(a) Using a dagger board
This happens to be a tough one. I have not yet decided what to do about it. I do understand that a single keel is better from the forces balance, it is easy to place in the right place and it is easy to predict its behavior. The drawback is the price of inconvenience. Considering my desire to travel in this boat, the dagger board would be too expensive in terms of accommodation convenience. So, I have this question still open and still think how to get performance, portability, convenience and redundancy.

(b) Many people said the earlier boat is a “floating iron”
Oh well, here I am trying to reconfigure lines as best as I can do. Actually the second crawler (I called it “The Crawler” because of two chine runners which looked like, eh… kind of feet. So I present only the hull form of “The Crawler.” To me it looks beautiful, but experienced architects possibly could say now that it is “a floating shoe box.”

(c) Some people suggested breaking the boat for pats differently
But I cannot! The folded boat must fit inside 6.5’H x 5’W x 1.8333’D built-in wardrobe closet. Well, I am about 6 feet high, and I would like to have at least some room to stretch after a long day of sailing and rowing. So, 6.5’ long middle section is here to stay. And the dreaded dagger board comes to mind as well. It would be nice to have 6.5’L x 4.5’W dry level pad to stretch.

(d) As Post #32 suggests I am trying to get “a good boat”

(e) Especially valuable suggestions by Petros
I did bow and stern a bit longer, but not by much. The boat is now 12’-0” I also tried to make smoother transitions and opened transom, I believe, to the utmost. The mast idea is still brewing. Most likely, I will be forcefully corralled in using Gaff, Gunter or Junk rigs.

(f) I don’t plan to have rowing thwart. I plan to have a dolly like in open rowing shells.

(g) Speaking of leeboards
This is a very real option for constrains my purpose requires.

(h) RWatson – you are so right about small boat and insignificance of those small marginal improvements. I totally agree with you!

So, below is the hull only of a boat where I tried to address all of comments. Hopefully it is better than what I had before.

The next thing would be slicing this hull at STA. 2.75’ and STA.9.25 It is too late and I am a bit tired.

Hopefully, kind people would comment on the second iteration and point me in the right direction.

Thank you and G’night.

 

It looks nice but it's a beamy boat with a relatively limited freeboard and no side decks or coaming that you will not be able to sail heavily heeled. A daggerboard has its biggest advantage ove a leeboard at the higher heel angles, when a leeboard used on the weather side loses immersed area. However, for relatively flat sailing there will be virtually no performance difference and - other things like area, aspect ratio, blade profile and foil shape being equal - the leeboard has less draft. It is certainly less difficult to build, with no worries about the trunk leaking, so I'm glad you're giving it due consideration.

 

Perhaps the section in my drawing isn't clear enough, as there's actually no hole in that "seat".
But even a seat with a hole in it can have one useful purpose and add to the comfort on board. But I wouldn't elaborate any further...

 

Great design, much improved. I would make the bow a little sharper only because is looks faster and sexier, however the bluff bow in your design gives you much more storage capacity and more righting moment.

Lee boards are a good option for such a craft, but I do like the dagger boards since they make the hull symmetrical and give the boat a cleaner look, and slightly better performance. These however are not good reasons to use them on your craft.

I highly recommend you consider a junk rig: They are very easy to control by solo operation (very forgiving of mistakes), will not flog if mis-set, rapid solo raising and lowering (little risk of fouling), the forces on it are lower so rigging can be light weight (lower cost to build), it does not need any of the expensive fittings necessary on traditional sloop or cat rig, less risk of having to make major changes to rig due to design mistake, very efficient operation in all points of sail except when close hauled. They do suffer in performance where they will not point as high into the wind as other designs. You can find excellent information on designing your own junk for your boat on the internet (and elsewhere in this forum).

In a boat that size you can also go boomless, use the batten tails to control the sail with sheetlets, so it eliminates the need for a boom, fittings, etc. You can make the max batten length six feet so they can stay in the sail for stowage, upper batten is canted upward to get more height above the top of the mast. You just roll up the sail with the battens in place and stow it in the center section of the hull with the bow and stern (and your 6 ft tall mast). It would also be very fast to set up and rig, in the last one I built I just used a single sheet off the longest batten, and went boomless. It almost sails itself, set it and forget it. Self tacks nicely as well.

I have built a number of small sailing rigs, and I have more recently tried out the junk on small tri. I really love the way the junk rig works in a small boat. I think I will stick with it, or variations of a modified junk, from now on in most applications.

 

Petros: I assume you do not mean the traditional junk rig with a separate sheet leading down from every batten, which has great control but is messy to strike. Without those it's just have a fully battened sail and has a nice low center of area. I like the idea of going boomless but I've never seen that with full battens.

One of the simplest sail types that also has a low center of area is the standing lug sail, which also works well boomless. Like the junk, the sail is simply cut flat with no darts, and tarp works well if you can stand the noise. The sail tack is taken to the mast so tension on the luff holds down the fore end of the yard, raising the aft end and also the leach of the sail.

Only two lines are needed, the halliard and the mainsheet. Where I sail I must continually raise and lower the sail because of bridges so I find this a handy rig. This year I plan to try using retracting dog leashes for the lines so I don't have to worry about tangles; the lines will still go to the same cleats of course as the locking mechanism of the leash is not strong enough to withstand sailing forces.

Afterthought: I checked the price on the retracting dog leashes at the pet store $30 each. Too much for an experiment. Nice units though, made in Germany. Same make as the one I use for the dog, but I don't need anything that good for this purpose. I will check Walmart for something made in China . . . should be much cheaper!

 

The Crawler v.3

Hello, dear forum members!

I would like to thank all who contribute by reading and directing me away from mistakes, especially Petros-ancient kayaker-daiquiri-portacruise-michael pierzga. Thank you again!

After some inspirational posts, I fumbled with the model and arrived at the “The Crawler” v.3

Again, this is nothing but empty hull. No keel, rigging, coaming, deck and other details are shown. I would like to nail down the hull and then proceed with the rest of design. I only dismembered the bow and aft in order to physically fit them inside the mid-ship section. The pictures are actual snaps of the DELFTship FREE screens. Of course, I did some editing.

I plan using foam and glass it over in ¼” (6 mm) layers. Then I am going to repeat the procedure until the hull reaches approximate 2” (51 mm) thick. The inner- and outer-most layers will get an extra glass on top. All edges will have wood trim under epoxied glass. All dimensions shown are outside margins. I made allowance of 2” (51 mm) for all major intersections of the folded sections.

This will give the empty hull 823 lbs (375 kg) buoyancy. So, the boat should be unsinkable with positive flotation. I also plan using aft and stern two separate hermetic compartments, as shown on the pictures. This will give extra buoyancy and dry storage.

I did not get to the other details yet and hope that knowledgeable and kind people would point me in the right direction.

As I go along, I will post more pictures, drawings, photos of a model mockup in 1:10 scale. I would like to make sure that I do not build an incapable boat, as I plan to navigate rivers, lakes and calm near-shore seas.

I have ideas and thoughts on collapsible coaming, decks, type of rigging, rowing dolly and masts, but before I proceed I kindly ask if knowledgeable people would correct any possible gross mistakes. If you have any thought – please give it to me now, so I would not waste more time on this branch of the boat design. Then I would move on.

The next thing would be the sail rig and the keel resistance systems.

Thank you all and especially people who actively point me in the right direction:

Petros-
ancient kayaker-
daiquiri-
portacruise-
michael pierzga
Thanks and g’night!