Small Kayak for Backwater Canals ?

Araldite is an epoxy which has been around for a long time. It is very strong, as all epoxies are, but there are different epoxy formulations. I have a lot of respect for Araldite as I used it for many years in the UK but I don't know if it has all the features necessary to make a good marine glue.

Special marine epoxies are used in boat construction. Even marine epoxies vary; some are formulated for gluing wood with a degree of flexibility to match the flexibility of the wood, and to hold when the wood gets wet. Others are formulated for use with glass fiber and yet others used for coating wood.

You should also note that the "five minute" epoxies are often not an epoxy at all, most of them use an entirely different type of resin. These, and also Araldite are very thick so may not penetrate into the wood grain well.

"Should I coat the lashings with epoxy?" I wouldn't reccommend it. It would make the lashings very rigid so any flexing could result in breakage of the lashing or the bamboo. If nylon lashings are used the epoxy may not adhere to the nylon and could flake off when the boat is flexed. The stiffness of a skin on frame boat comes from the skin not the frame. A small amount of glue on the knot might be a good idea though.

"Should I coat the skin with epoxy?" Absolutely not! The skin and the frame work together as an integral whole with the frame in compression and the skin in tension. If you epoxy the skin it may become so stiff that it is in compression when the boat flexes; it is far too thin to support compression loads so it will buckle. even if it doesn't crack it will develop wrinkles that will look ugly and slow the boat.

Based on my limited knowledge I would think the main application for epoxy would be if you wished to use solid wood frames instead of using steam bent bamboo ribs or one-piece plywood frames. Other than that, and possibly in the contruction of the coaming, there is really no much need for an adhesive in a boat of this kind.

The Inuit (Eskimos) that perfected the art of kayak building only had driftwood and bone for the frame, animal tendons for the lashings and seal or walrus skin for the covering. These boats did not last long in use, but with materials such as bamboo, man-made thread and fabric, and a good paint or sealant skin on frame boats become very durable.

Having said all that, I reiterate that I have never built or even owned a skin on frame boat; what I have said is based on engineering knowledge and intuition. So, while I am delighted to provide advice I must be careful not to mislead you inadvertently. The best way for you to proceed now would be to obtain a book, consult with a skin on frame designer of builder, or troll the Net for as much information as you can find on the subject.

 

Thank AK for the time and help...

Thanks a million AK.
Epoxy was always lingering in my mind, may be I was confused with the wooden frames and bamboo.

But now I know I don't need Epoxy at all.

I have shifted the topic in some appropriate forum (greenland kayak forum - qujaqusa forum) I guess I will get better help there, hope to see you around. Thanks for all the help, you got me going really.

I shall update this thread when i start the work, your presence will be really wonderful through out the process.

cheers
MS

 

Good luck and good sailing, or paddling that is!

 

AK,

Do i need to follow an Offset Table, and plot it and make a lofting at all?
What dimensions and numbers should I follow if else?

What is the height of the Boat,
what is the interval between the ribs,
what is the curve/rocker to achieve?

Should I consider them at all? Or do I trust my eyes and instinct and proceed?

Where is the need for my station and strongback?
Do I need a strong back - which of them do I mount first 0 Gunnel or ribs or keelson?

Am I asking the right questions?
Or am I worried too much instead of jumping into building them?

MS

 

Your questions reveal that you have not yet decided to design it yourself, adapt a design meant for a different construction method or build to an existing plan for a skin-on-frame boat. Let's look at the options and see the implications.

How you go about it is your choice.

Option 1. If you are willing to do as I did and make several unsuccessful boats to gain experience by all means design it yourself, but there is a lot to learn. Although free software is available on the Internet which will help you develop the general shape of the boat it will not help you with the construction details or guarantee that the boat will be stable and perform well unless you know how to interpret the values given by the analytical features of the software. Questions about the height of the boat, rib or frame spacing, beam, and rocker are related to boat design. Given the experience of designing a few boats, or years of study of boat design, it is no doubt possible to design a boat that will meet it's objectives first time. In practice, it takes lots of practice to get it right.

Option 2. At the other extreme if you build to a plan for a skin-on-frame boat you will have dimensions for all the components such as the frames and the frame to frame spacing, constructional information such as the strongback, material specifications etc.

Option 3. In between, if you have a plan for a boat of a different construction, or just an offset table, then you have the shape of the boat and must decide how to build it. If you have an Offset Table, you will have to determine frame location, which will probably be at the same location as the stations in the table, and you will have to plot the outline of each frame onto your ply or other material and cut it. If you use bent bamboo frames you will still have to make forms around which to bend them.

Should you trust your eyes and instinct? I did that and went for option 1. The first boat had a Vee-shaped bottom, was lovely to look at but flipped me into the water unless I lay flat in the bottom. I ripped out the Vee bottom, increased its beam, and installed a flat bottom. A bit better, I was able to sit up in it but it was still unstable and I only dared try it in my swimming pool. I sawed off the last 2 feet and installed a transom to remove buoyancy and make the stern sink an inch or two, lowering the center of gravity. At this point it was good enough to take to the lake but I had to stay in shallow water. I built another, also with a flat bottom, incorporating what I had learned, but it was little better although much easier to build. After a bit more thought I decided that the flat bottom was the problem. Flat bottomed boats float high in the water and usually have a lot of beam for stability, mine did not and I did not want to built a "fat boat." Up to this point all my boats except the very first one had three planks, two sides and the bottom. I used very cheap materials for these boats.

The next boat had five planks: two sides or sheerplanks and the bottom plank, which were connected by two planks called garboards. The cross section was five sided. Success! This shape resulted in less buoyancy than a flat bottomed boat so the boat sat lower in the water when loaded. Lowering the center of gravity by only 2 inches made all the difference; in such tiny boats stability is on a razors edge. This boat is much lighter and faster than plastic boats and effortless to paddle; slightly tippy but I feel safe enough to tackle a modest-sized lake on a windy day with power boats zipping around. I would not take it out to sea! It's only shortcoming is, it is not easy to turn around, but that is not generally a problem. I used marine ply and other quality materials for this boat, and it attracts compliments and interest. The first 2 boats were scrapped, but I have a good boat after three years of work, several hundreds of hours work and about twice as much money as it would have cost if I had built it to a plan, which would only have taken 60 or so hours. Sounds like a poor bargain, but I loved doing the work and I understand so much more about boats now.

I was in it to learn. I already had boats, and I enjoyed the learning experience of both designing and building; I ended up with a great boat and the ability to produce more if I wish (I have a second one under construction). If you want a reasonable boat for a reasonably low cost in a reasonable amount of time which the certainty that it will turn out well, buying plans for the specific boat and construction method is the best way to go (option 2), the plans will be a fraction of the overall cost and you will have the confidence to invest in good quality material at the outset.

The strong back is needed to keep everything in place and lined up until the boat is strong enough to hold its shape. It will ensure that your boat turns out properly shaped and true, not bent or twisted. Since a skin-on-frame boat without its skin is very flexible, the strongback is still needed even after the frame is completed until the skin is applied, shrunk and sealed or painted. A strongback is not needed for all methods of construction; I do not require one but I do not build skin-on-frame boats.