Proof of Concept

Some thoughts of my own, although the subjects of folding and nesting boats tend to get controversial so not everyone will agree I am sure.

From my own personal experience with folding kayaks and canoes - the ones that dismantle and pack into a bag - they fall into one of the following categories 1) very expensive, 2) difficult and/or time consuming to assemble, 3) awful appearance and/or performance or 4) all of the above. I haven’t seen one that I would wish to possess, have the patience to assemble or take apart, and still be able to afford. They’re just the thing if you want to travel and take it with you on a plane. I doubt a true folding boat is practical in the size of boat that you are displaying.

A nesting boat doesn’t pack into as small a space but goes together and breaks down far quicker and is probably easier to make. There’s a bit of a performance compromise to get the smaller parts to fit inside the bigger parts, but not too bad. The joints between the sections is no big deal, the further they are from the cockpit the less stress they have to take, therefore I would prefer a 3-section boat to one with 4 sections. One of the simplest and safest ways to join the sections is with loose-pin hinges. If you have a minivan hauling a nester that will fit inside is less of a hassle than car-topping.

I wonder how much boat design experience you have had. How wise is it to undertake this part of the job yourself and risk your investment in time, materials and effort? If this is your first own design and you are determined to go ahead, I suggest you try your hand on something smaller and simpler first. That was the route I took; I considered my first boats as disposable from the outset and I never regretted the time and cost sent "learning the trade" by building and quickly tossing them.

 

Congratulations -
what you have re-invented is the Phil Bolger Folding Schooner

http://www.ace.net.au/schooner/fs.htm

 

I owned Sigma expedition tandem kayak - so I know about folding kayaks. I agree with Ancient Kayaker that it is a pain in the butt. You are right - there is a joy in building "something." I would enjoy building a boat. I agree that there would be other issues with this boat. Thanks for the reply.


I don't have much boat design experience and trying to learn along. This is one of the reasons I am asking more experienced people of their opinion. So far I have gotten philosophical advice.

Actual building, stress check, working with foam and epoxy, sanding and fairing - I have done it before. I don't think this will be a problem. The boat will be just a foam/glass shell with a few through bolts to hold parts together. Simple toungue and groove joint below waterline will provide secure connection. Through bolts will fix it above.

Basically it is a sailing canoe. I just want to know if the shape of this boat concurs with basic hull principles. I did some reading, and think that it is. That is why I asked the opinion of true design professionals.

Again, this model is not finished. It reperesents an intermediate result. Thanks for replies.

 

I have some sympathy with each of the last 2 posts! I don't want to see a builder disappointed with the results once the boat is in the water. There are two challenges here -

First there's building a boat that will fold or come apart in sections for storage and transportation, which can be met by selecting a suitable non-folding boat design and modifying it. The Bolger Folding Schooner gives a lot of clues on what kind of design to start with, including the multi-mast approach although the Bolger has far too much rigging IMHO and a rep for fragility. I am sure you have the skills for this aspect of the task.

Secondly there's the question of how it will sail: that requires a whole different set of skills, experience and training that I am not convinced you possess. Ultimately, the performance on the water will pass the final judgement on the boat - not its ability to fit into a closet.

it's a big job to undertake and I want you to start off right!

 

Thank you! Under the circumstances I consider it to be a compliment.

 

looks good, it could disassemble and fit in the back of a pickup, sweet, no trailer.
I would be concerned about the open hulls getting filled with water and sinking as a sailboat will heel over. Make it a trimaran too, why not.

 

A great idea and it is certainly feasible. I have made or designed similar home-built kayaks, as well as actual skin-on-frame folders.

this is what I would suggest: find a well mannered and proven hull design and stay fairly close to the same lines, even if you use a different construction method. That way you will have something you know will perform well once you have a viable folding design. No need to reinvent the hull shape, find something that works well and copy it. Go out and try one out yourself if possible.

For the attachment means try to use something with no loose parts. The nut and bolt attachment is simple but you will almost certainly loose the parts sooner or later (even drop them in the water), and it will require tools to assemble. I did that on my first one and would not use it again, too much hassle for actual use in the field, consider you are usually on a beach or a dock, dropped bolts and tools can mean you are done for the day before you even get started.

The best method I have found is to use stainless over-center latches. these are the ones with a clamp or bail with a lever than locks closed because it goes "over-center". The best ones are also self locking, so even if bumped or pulled on will not pop open unless the lock is manually depressed. It takes some searching but you should be able to find what you need available from England or USA suppliers. Make sure they are large enough for the intended loads, a failed latch out on the water would not be fun.

I made a take-apart kayak this way, three parts, fore and aft section had waterproof hatch for access. Each segment was held in place with three stainless locking over-center latches. Only the lower one (at the keel) penetrated the water tight envalope, used a large neoprene gasket to keep water out. It only took about 3 or 4 min to assemble, including the time it takes to replace the hatch lids in the bow and stern compartments. I had a wood framed boat so I made some mounting plates for the latches that allowed more screws for attachments to the frame for a stronger mounting.

Good luck

 

Good advice from Petros.

A couple more points: it is not practical to have side-decks in a nesting boat AFAIK; The hull will have to be built so the stiffness comes from the construction, but a canvas deck could be used to increase the swamping angle, with tie-downs or heavy-duty snaps.

It occurs to me that building a nesting boat accurate enough so the sections come together perfectly may be a challenge. Perhaps one solution to that would be to build the boat in one piece with double bulkheads at the joins - provided you have the space - with just enough space between them for a handsaw.

Petros: the over-center latch is a great idea but the only ones I have seen are small ones for suitcases. What are the larger sizes intended for? Then I will know what to ask for.

 

I do not know if there was an intended use, my customer found the supplier, they are used in marine applications, holding down hatches, cargo bins, life boats, etc.

There are lots of load rated stainless latches available, you just to search for one with all the features you want. Good ones are not cheap, but well worth it, the suitcase type are way too flimsy. I think the ones we used were rated for 400 lb loads, but they only used two 1/8" screws for mounting, so even if the latch was good for 400 lbs it seemed unlikely two 1/8" screws into cedar would have worked. I drilled the holes for the next size up screws, made a stainless mounting plate that used 4 stainless screws each, all were thru screws with stainless washers and ny-loc nuts installed "wet" with epoxy. Held up well. See the attached pictures. The sections of the kayak could be packed and shipped as "luggage" and used at your destination.

I calculated the loads on the latches as if a fully loaded kayak (paddler plus cargo) was suspended by the bow and stern only, plus a 2.0 safety factor. Pretty severe loading not likely to ever occur, I suspect frame would fail before the latches.

It worked so well I am thinking of designing and building a 16' folding skin-on-frame sailboat (with a cabin to get out of the weather) using the same assembly buckles on the frame. The idea was to have a portable micro-cruiser that can be packed into 2 or 3 duffel bags.

 

Don't give me more ideas Petros! I have enough boating projects already . . . .

 

Very nice craftmanship! Really nice work and impressive kayak! If I could not finish my closet-folding-sailboat, this is what I am going to build. Thaks for the pictures.

Regarding the loading -- being a structural engineer, I believe you over rated the load on your joints. It will be much less because the midle of your kayak is supported by water acting as a spring mat as well. Nevertheless, these latches is the most probalble joint I will use above the water.

In my neverending quest, I am still trying to fit a sailboat in my closet. The model below folds in a package 6.5'H x 5'W x 2'D. This contraption will fit inside my closet and I wonder if I made any really gross error in the hull shape. I would speculate that this hull should sail fine in flat water and a very little chop.

Because I have specific requirements, it is difficult to use an example, or I haven't seen one...

Any opinion would be very welcome and deeply appreciated. Thank you.

I think pictures are self explanatory.

 

I would put an Optimist-style daggerboard keel on that boat:



It is enormously more efficient than the twin chine-keels your drawings show, can be easily stored inside the volume of your dismantled hull, and both the keel and the keel box are easy to construct. Besides that, eliminating the thin, protruding chine keels would make your boat less vulnerable to damages (either from grounding or due to handling and transport) and would save some storage space.

Cheers

 

Thank you for your thought. First of all, I did not show the ruder in the pictures above.

I was thinking more of accommodations. If I have a box in the middle I would not be able to stove bow and aft sections and to keep the folded boat in the closet. The keel box would also prevent from rowing this boat, and this is one of the requirements.
That should explain why I extended fins to sides.

Also, during expedition, the box in the middle would greatly limit convenience of a sailor. On the other hand if keels are set outside, the whole midship area is available for camping, sleeping, convenient sailing, gear, etc.

Another convenience of the keels on sides, is the ability of beaching the boat so the boat stays level.

Regarding twin keels, my thought was that when the wind is light, there is no need for much of a keel area and when wind is strong, the boat would heel and one of keels would fully engage. And both of these keels fit in the "closet" envelope 6.5'Hx5'Wx2'D.

Besides, extreme performance of the boat is not required, it needs just to sail OK. Probably convenience and ease of storage/portage is more important than an extra half-a-knot performance.

Perhaps my posts do not reflect what I keep in my mind.

 

I would break the boat up differently. Put the sleep in..full length... section in the middle. Perhaps long bow. long mid, short stern section

 

Thanks, I was also thinking about the structural integrity of the hull. As shown, the bow bulkhead would provide needed longitudinal and transverse stability for the mast. If I use a different arrangement of split sections, then I would have to reinforce the mast base somehow. When I have this conveniently located bulkhead, then I could just provide a slip sleeve for the mast. I think it is simple. Actually I was thinking about a threaded mast with a cotter pin bolt. This should provide sufficient connection detail.

How to make such a large thread? Here is my take on it:

(a) soak enough rope length in epoxy, use mechanical force to fully saturate
(b) tight wind this rope around the base of the future mast pole in a predetermined spiral pattern (mark it with a pen) and nail the ends only
(c) let the saturated rope harden and sand smooth all irregularities
(d) the thread must be smooth and without uneven bumps, really
(e) prepare a sleeve larger in diameter than the hardened "rope thread"
(f) grease the bottom of the new mast thread well, Vaseline should work fine
(g) insert the mast bottom in the sleeve and fix it there, somehow
(h) fill the sleeve half-full with long pot life epoxy with strength filler, filament filler is fine for this purpose, warming up the mix should make it less viscous
(i) when epoxy hardens - unscrew the pole, some initial force may be needed
(j) some possible voids in the receptacle is OK
(k) I would do it on a mockup-model first
(l) attach the sleeve to the bow bulkhead with enough of S.S. flat ribbon U-brackets on a rubber mat

I have done something similar before, but not on this scale. This technique should work for small boats with moderate loading and it would also allow inclining the pole backward a little. My problem is what should be the angle of inclination and how high should be the mast pole?

That is where I need help. Thanks.