Baby Boat - the one sheet boat madness continues

[flo-mo]

This may be one of the smallest double ended rowboats ever designed and this one is made of a single sheet of 4mm plywood.







It's no surprise there are no comparable boats. It's simply pointless to make a double ender of this size (7' 4" x 42,5") because of the lacking buoyancy in the ends and the resulting low stability (both longitudinal and transverse).

Anyway - I am going to build this boat because this is my attempt to create the one sheet design with the highest capacity possible that can still be called a boat and I think it's a cute and funny looking little boat.

Here is a quote from Hannu's Boatyard explaining

What is a one sheet boat?

A boat made of just a single standard sheet of plywood (The "standard" standard, 48" by 96", or 122 cm by 244 cm. There are other standards too...)
If the transoms, sides or any other parts of the hull are made of something else, the boat is not a one sheet boat, but something else.
Chine logs, rubrails, internal frames, butt blocks, seats etc. may be made of whatever You like, but not the actual hull enclosure.

Basic one sheet boat design criteria:

• make it carry as much load as possible
• make it look like a boat

The load carrying capacity is connected to the maximum displacement of the boat (displacement just before swamping), or the maximum enclosed volume, if You like. So make the thing as big as possible.

But what makes a boat look like a boat?
If You make it:

• longer than it's wide
• wider than it's deep
• tapered in at least one end, in at least one plane (horisontal or vertical)
• throw it into water
• and it floats

then most people will probably call it a boat.

I am going to use this sheet of 4mm Sapeli plywood (250 x 125 cm) which is slightly larger than a standard sheet so the boat will be larger by 2,46%.



The building method will be the same that I used for my one sheet canoe Little Guide.

[flo-mo]

Again I am cutting the panels with a knive. The Sapeli plywood is much harder than Okoume and my fingers almost got sore but I was persistent and finally had all panels neatly cut.

[flo-mo]

Two glass reinforced butt joints need to be made. I tried to make them as accurate as possible hoping they will bend almost the same way as the symmetric panels without joint.

[flo-mo]

The short panels and the huge amount of twist require unusual steps and some improvisation to get the panels connected.



These wedges connect the sheer panels. I covered them with masking tape so they wont stick to the panels.

[Gerarddm]

It's an interesting exercise, sure.

[flo-mo]

I glue these wedges to the delicate pointed ends of the bottom panels to be able to apply clamp pressure to get the ends together.





This is stress for the plywood and the builder.

[flo-mo]

[MiddleAgesMan]

That sure is a lot of boat for one sheet. Good on you! :-)

[JimD]

Brilliant!

[flo-mo]

A forum member asked me for advice because he had trouble with the build of his Baby Boat.
Unfortunately the bottom panel cracked at the location of maximum stress shown in this picture (red colour).



He is using 4mm birch ply – maybe it is more brittle than okoume or sapeli.

At the time he approached me I hadn’t started my own build so I could not give him any advice. But this was another reason for me to build my own boat because I wanted to know if I would have the same difficulties and if it’s possible to build this boat at all. Now with all panels assembled I can say it is possible though it’s really not easy and until the end I was afraid that my panels might crack too. I am hoping this thread may be helpful for him.

So I am happy that I was able to assemble the hull successfully but wanted to inform potential builders of this design about the problems that might occur.

[flo-mo]

Next step is adding a "false" inner stem. A heavy fillet would be ok as well but I like this method better.



Dry-fit of a strip of ash.



I made small fillets to seal the cavity formed by the strip and the ends of the panels and temporary spacers are helping to align the panels at places where they need some persuasion



With a funnel this cavity is filled with epoxy when the fillets are half cured so there is no more danger of leaking



When everything has cured I remove these spacers

[potomac]

As with so many of your designs, I think this is quite something. I know that to some extent, these are done as an exercise, but so often they are lovely- or cute in this case, and show a brilliant efficiency in the use of materials. Are the offsets or even a nesting diagram available?

[flo-mo]

I wanted to be sure that after removing all temporary fasteners the panels wont disassemble because of the enormous twist. So I glued small pieces of ash at the places with the highest tension on the outside of the hull. I don't know if this is necessary but somehow it feels reassuring.



Now I can remove the clamps and the wedges at the tip of the panels. The wedges are made of a very soft wood (paulownia) so sawing is easy and sanding flush should be as well.

[flo-mo]

Are the offsets or even a nesting diagram available?

You can find them in my thread about the one sheet canoe but of course it makes more sense to show them here:

[potomac]

Wow, you are full-service. Thanks so much. As I've said, I'm a real admirer of the work you are doing. I hope you'll write up how she goes when in the water. It sounds like a fun project to do with a kid. -Aaron

[Harbormaster]

Incredible, a real delight.

[JimD]

He is using 4mm birch ply – maybe it is more brittle than okoume or sapeli...

Just about everything is more brittle and less flexible than okoume. I think birch would not be a great choice but I hope he got it resolved, perhaps with a liberal use of epoxy and some fiberglass.

[htom]

Incredible. Flo-Mo, your designs are delights. Each and every one of them.

[gstanfield]

I agree, what a great exercise in making the most with the least!

[Daniel Noyes]

Very cool, "almost" ... or should I say "a little more than" a corracle, should be fun.

I wonder about how you have the rails finished in the model, coming to a point beyond the bow, will the full size boat be the same?, I think I would prefer the rails cut back flush and parrallel to teh bow, or add a solid wood cut water to the bow of sufficient depth that the rails could terminate agaisnt it, something like a Adarondack guide boat cut water.

[flo-mo]

I wonder about how you have the rails finished in the model, coming to a point beyond the bow, will the full size boat be the same?, I think I would prefer the rails cut back flush and parrallel to teh bow, or add a solid wood cut water to the bow of sufficient depth that the rails could terminate agaisnt it, something like a Adarondack guide boat cut water.

I understand your concern and I am considering how to solve this detail but haven't made a decision yet.

A little update:



I made fillets and taped the uper chine. I will glass the bottom panels later and the glass will also cover the center and lower chines.







Filling the gap on the outside:

[flo-mo]

I am adding a small outer stem. This is not really necessary and probably overkill but again it is because of the look.



I bend a strip of black locust with a heat gun.



Then I rip it with a table saw

[potomac]

It's looking great. It looks like the interior fillets are getting fiberglass tape. When you say the chines will get fiberglass, do you mean you intend to fiberglass the outside of the chine, or are you referring to the work you've shown in the pictures above?

[flo-mo]

Glass for the bottom









Glass tape for the upper chine

[flo-mo]

[Daniel Noyes]

looks like alot of fun... how much do you think it will weigh when done? 40lbs? or less.

[flo-mo]

Here is a rough estimate:

panels 6kg (13,3 lbs)
stems 0,5kg (1,1 lbs)
gunwales 2,5kg (5,6 lbs)
decks 1kg (2,2 lbs)
seats 3,0kg (6,7 lbs)
epoxy, glass and varnish 3kg (6,7 lbs)

makes a total of 16kg (35,6 lbs)

I don't think this guess will be far out.

[Dave Hadfield]

A wonderful exercise, and very fine-looking designs.

But with respect, I think it's easier to join 2 sheets of plywood first, then mark and cut panels.

Plywood isn't really that expensive.

Speaking for myself, I find that most of building a boat is labour. It's only my own perspective, but after a few years, the cost of materials-used doesn't really seem to matter much.

Dave

[Bram V]

A wonderful exercise, and very fine-looking designs.

But with respect, I think it's easier to join 2 sheets of plywood first, then mark and cut panels.

Plywood isn't really that expensive.

Speaking for myself, I find that most of building a boat is labour. It's only my own perspective, but after a few years, the cost of materials-used doesn't really seem to matter much.

Dave

But the the point of the excercise is to make the most with one panel. This is a voluntary design constriction flo-mo gives himself. I think it is brilliant, I may not wish to make this exact boat, but marvel at how much boat can be made from a single, double, or triple sheet.

[flo-mo]

The gunwales are made of 4 laminated strips and the first one has a small hardwood strip attached to cover the end grain of the plywood panel.







I pre-bend the strips with the help of a string which makes it easier to glue them to the hull

[flo-mo]

Here is my solution for the "rail end situation":



A steam bent piece of locust ...





... covers the end of the gunwale

[flo-mo]

Any association ?

[Momist]

"Any association ?" That is one very sexy looking boat. I've never been able to honestly say that before!!

"As an exceedingly labor intensive wood sculpture this is an ingenious project." Beautiful as it is, it looks far more practical than most coracles, and should have sufficient stability for practical use. Just how much stability is yet to be seen, perhaps, but in my view it is a worthwhile project from both the artistic and the practical perspectives. Surely, there is a niche for such a small boat capable of being built from a single sheet of plywood? It could make a great little cabin top dinghy for a small cruiser?

[flo-mo]

This is what I was thinking of:

[flo-mo]

Beautiful as it is, it looks far more practical than most coracles, and should have sufficient stability for practical use. Just how much stability is yet to be seen, perhaps, but in my view it is a worthwhile project from both the artistic and the practical perspectives. Surely, there is a niche for such a small boat capable of being built from a single sheet of plywood? It could make a great little cabin top dinghy for a small cruiser?

At its best it will have the stability of a small canoe so I don't think it could be used as a dinghy.
I know it does not make much sense to build a boat like this particularly the way I do it - nevertheless I am enjoying the process.