sewing a wood boat?

[sigurd]

In Kerala, India I saw boats that were sewn with cocoa fiber drenced in I think it was sesame oil and rice powder.
If you would imagine the stitches, they were straight across the seam on the outside, with the thread in little grooves in the planks. On the inside the stitches were crossing over a sausage of the same fiber.

It looked very solid and tight. For thinner boards nails will sometimes tear the skin of a flexible hull.

I am wondering if any have experience or advice to give. I am considering sewing a "whitewater kajak"/snow kite sled/pulk from 3mm oak. I could put thinner strips behind the seams or just overlap them or bevel them to a smooth overlap. there would be lots of thin, what do you call it, not stringers but the other direction, and a stiff bottom plank going from the bow and almost all the way back and be about 30cm wide. Reason for oak is that even if 5mm pine or some soft wood is lighter, it is so soft when running on ice and snow. What do you think?

Edit: Hemp or some other stuff that will shrink in water, and live very long as long as there is tar or oil, might not be strong enough, considering how small the grooves in the 3mm wood will have to be. Any idea?
considering using carbon tow, but when a glued seam goes, it leaks, but in a soft boat the fiber sausage or drenched fiber behind the narrow seam support plank will still be a gasket as long as the stitches are not slack..? Besides, it is easier to fix anywhere. What about sewing with carbon tow drenched in tar, and still using the gasket seam?

[Fanie]

You are going to need a big sowing machine.

I'm a fiberglass fan, not sure why you would put yourself through using such unscientific materials which is going to be a huge job and lots and lots of frustration. Not only leaks and the constant maintenance but it is going to be slow as well.

While it is interesting that people make boats that way, here in Africa they use hollowed tree stumps.
Fortunately I never felt the urge to grab a tree and hollow it for water use

Shop around a bit, there are some very very nice boats you could build that can last for many years and give many hours of reliable pleasures aboard.

[Jimbo1490]

Sew it with copper magnet wire. Use the good stuff with class 'H' insulation as it is epoxy coated rather than lacquer. somewhere between #12 and #20 should do the trick.

Jimbo

[sigurd]

Fanie: Why do you think it will be slow?

Jimbo: Interesting idea, I'll think of it some more. Do you think it will be better than carbon thread?

[robherc]

I'd go with the wire over carbon thread...should be quite a bit cheaper I'd think...though I haven't been pricing carbon thread lately.

Getting the stitches put in place could be slow, but if you stitch first, and bend later, it should make the process a LOT easier IMHO.

I think if I were to take on such a project, I'd drill 1/16", or 1.5mm holes to stitch through, then seal everything up (inside & out) with a coat of epoxy/vinyl-ester/polyester for the waterproofing...why take the chances & extra effort (plus maintenance) of having a degradable gasket? Though silicone caulk for a gasket might not work too badly...

[sigurd]

I'm getting some tow now anyway. But those are only filaments stuck together, maybe copper will be stronger on abrasion.

What would you do, scarf them, overlap them, or put a backing plank behind the seam?

Re the gasket, yes I suppose anything will do, if it is coated in epoxy then surely the seams will be glued, but then I would probably not bother to stitch. But behind the epoxy coat, maybe there can become pockets of water somewhere, if you put linseed oil and tar on every few years, then it won't rot, for sure! P.S. The indians said the cocoa gaskets lasted forever.

[robherc]

Oh, I was thinking stitching for a tortured-plywood approach.

Anywise, for either case, I'd prob. try to bevel the edges of the wood so they meet flush (unless you wanted to get REALLY fancy & make a bead/tongue-in-groove joint). And for a gasket on a non-epoxy sealed version, I guess I'd recommend using the clear 100% silicone caulking that's labeled for aquarium use. I've built SEVERAL custom aquaria & aquarium decorations using the stuff. It isn't NEARLY as strong as epoxy for gluing (which isn't your goal anywise), but the stuff can be submerged in salt OR fresh water for MANY years and stay as flexible, strong, and waterproof as the day it cured!

If you're wanting to go more traditional & "low-tech" though, then I guess I'd take the Indians' advice. They've had countless decades to perfect their methods, so there's prob. nobody alive who could be of more help to you there.

[Fanie]

Originally Posted by sigurd

Fanie: Why do you think it will be slow?

Jimbo: Interesting idea, I'll think of it some more. Do you think it will be better than carbon thread?

Female instinct

On the other hand it would probably have to be fast if you are going to row it over the river

Just pulling your leg, but building a boat that way I would save as a last resort. If you like it, it's up to you.

Remember to take the life jacket

[ancient kayaker]

Sounds like a fascinating and very "green" concept. Crossing the stitches over a fiber sausage would reinforce the seam similarly to an epoxy fillet and function as a shock absorber as well as sealing the joint. If you use thin oak planks then ribs or frames would be needed to relieve strain across the seam and also cross-grain stresses. Basswood was the material of choice back when small wood boat building technology was evolving from traditional methods in the 1880's, and may have advantages. Ply would be an easier and structurally better choice but not as green. Looking forward to seeing what comes out of this.

[sigurd]

But what happens to plywood or laminated wood if the epoxy capsulation is worn away? Doesn't it trap water under the remaining epoxy? I may want to build from single-ply veneers and epoxy instead, but not sure what to do on the outside if so. Some people use glass to protect the epoxy sheath, but would it be possible to just tar/linseed the outer surface veneer, in order to prevent damage from moisture?

[ancient kayaker]

Since you are thinking about epoxy and ply you’re not particularly worried about being “green” but it is still an interesting alternative to S&G that is worth a try as an experiment. I think you can make a fine canoe using this method, I am not sure it will be robust enough for whitewater use but I would like to be proved wrong. You should certainly stay as close as feasible to the original methods but modern materials will make your task easier. Here are my suggestions.

Sewing: this link http://www.wedigboats.org/Thaikkal.htm has a close up of the sewing method; it looks like the plank edges do not come together, they are separated by the sealing rope. If this is the case then you can take the plank developments for a S&G boat and cut off a strip equal to the rope radius from the edges that form the chines. I imagine the gunnel, which should probably be wood, can also be sewn. These boats do not have ribs or frames apparently. Google will find other links for you for researching.

Coatings: based on my own experience epoxy and glass aren’t necessary for a light boat that is removed from the water so it can dry out. While glass can greatly increase strength, ply already has enough. My first boat was not successful on the water but it survived an entire year of outdoor storage, found it half full of water once, it vanished under several feet of snow in the Winter and was fine in the Spring. It was just painted with regular outdoor latex house paint. While marine ply doesn’t deteriorate rapidly even with repeated soakings, on that boat I used very cheap door skin ply.

Planks: I don’t think think oak planks will have enough cross-grain strength. I would suggest you go with 3 or 4 mm or 1/8-3/16" ply, marine if you can get it, and paint the planks before sewing it up paying particular attention to the edges and holes. However, sew up a few trial seams first before spending real money, as you may find such thin ply to difficult to work with.

Sealing rope: The rope should be intrinsically waterproof if possible as otherwise it will eventually end up soaked. It does not require tensile strength. If you aren’t particularly aiming for traditional materials, you could try small diameter pool noodles.

Binding cord: copper is far too weak. Skin boat builders use a product called artificial sinew for binding the frame together, it will probably be ideal for your application. You can Google it but these guys will have it: http://www.shop.skinboats.com/main.sc

Sealing the holes: Any decent caulk material will do the job.

I’m not sure how to handle the stems, which will need more stiffness and strength than I can see the sewn method providing. As far as time is concerned, it should be very fast, it’s similar to the skin boat method which is generally quicker than S&G.

[sigurd]

I think what you see on the coseup is the inner sausage - I do not think any fiber is driven between the planks - could be wong though.

[keith66]

Sewing wooden boats together has been around for thousands of years, it was also used in England by Samuel Saunders who pioneered his patented "Consuta" system. he started in about 1998 and his company S E Saunders ltd became famous for high speed motor launches and seaplanes. The company built thousands of boats this way from small launches right up to torpedo boat destroyers, eventually the firm became Saunders Roe & eventually got swallowed by British areospace.
Effectively he built laminated wooden boats of similar scantlings to modern cold moulded ones but without the glue. There are not many of them left as by all accounts they were very difficult to repair. I own a 28 ft launch built in 1905 and she was built from 2 diagonal layers of port orford cedar planking 1/8" thick with a single 1/4" later of mahogany running fore & aft, the stiching consists of vertical runs of continuous copper wire running in & out. the stitches are about 3/4" long and are inlet on the outside, runs are about 1 1/8" apart.
Oiled calico was placed between the layers for waterproofing. For more on the history of these boats see Ray Wheelers book from River to sea
I am halfway through the rebuild of my boat though i confess i have cheated by stripping of her outer layers and laminating a cold moulded hull directly to the original. It has taken too long but is getting there!