need help with new drawings for kayak

hi all, heres a big request.
my daughter and i are on a s.o.f kayak workshop- a community project, where all 8 new boats go to the local "re-discovery programme".
anyway, my mate who is running the clinic/workshop is considering getting into selling his boats commercially- it is a design he has developed over time- and the skills he is teaching the kids are amazing- with the steam bending of ribs, fairing, lashing etc etc


The creation of these boats is a real art form, however if he wants to produce them a little more efficiently- he is going to need to look at an assortment of jigs, particularly cauls to bend the ribs on, both for consistency and efficiency.
is there anyone who can assist my mate, Kielan, in doing some drawings up for his craft.
i would imagine a cross section at each rib station, so that i can help him make some plywood bending cauls.
he obviously doesnt need any design specs, stability, waterline etc etc etc- this is a proven design of his.

i have thought of just taking lines off the frame of boat, but as there are minor discrepancies in the hand bent forms, the keel and stringers are made fair with some shimming and trimming, during the construction process,- so lines off the skeleton would not work.
maybe lines off the finished nylon skin, fair them out digitally,where they might need it, and then work backwards to the rib stations!!???

any ideas anyone- is this way too much work, or can somebody help with this project?

many thanks
wayne

 

what you ask is a lot of work if you want demenstioned drawings. I suggest making card board templates at each location, off a finished hull, and than use those to make your bending forms. no drawings necessary.

 

^^ This. If the finished boat is fair you should be able to take patterns straight from it. Much easier.

 

What is the information you have and what plans would you need someone to draw?

 

Nope. It's pretty much what you have to do, if you want exact copies of the boat. Even then, the reproduction accuracy is going to be nothing like with fiberglass.

Probably better to define templates for the frames, as they are, then put up with the fairing process later, which is probably all but inevitable anyway, as you are using timber rather than plywood to make the frames out of.

The problem is that no two pieces of oak are going to bend the same way when steamed. So first you need a cardboard template for each frame, and each template is going to need a tolerance range for the new frames.

Next, bending jigs are going to be have to be made with "pressure points", to mimic the hand bending. A minimum of three such pressure points are going to be needed for each frame, plus some kind of clamp at each end.

The beauty of the pressure points is they can be shortened or lengthened as needed to get each rib to fit within the tolerance curves on the template. Once that is done, you can be pretty sure every rib made, using that jig, will fit within the tolerance curves.

This will take some time. But once done, it will be possible to manufacture ribs on a mass production scale, making maybe a dozen of each at a time.

The ancient Romans used a similar technique when building their war galleys.

Another time proven method is to make station molds, as many as a dozen or as few as four, that define the stringers. These are placed to not interfere with the frames. The stringers are temporarily fastened to these, then the frames are bent to fit them.

This is the most common method of defining the shape of wooden boats.

The weakness of this system is the stringers may not be stiff enough to hold their shape, as the frames are forced in.

There are two cures for this problem:

1.) more molds, and
2.) Stout ribands between or in place of the stringers. These are removable if they are in place of the stringers, or permanently attached to the molds, if they are not.

 

or 3: Female moulds or braces external to the frames.

This allows a lot of force to be applied to the ribs, without distorting the stringers.

 

thanks guys, i have been giving this whole process a lot of thought today- while at the workshop.

the way these boats are made- the ribs are bent, then the stringers lashed on top of them, and in order to get the stringers fair- shimming is placed between the ribs and the stringers.
so problems 1. cant take lines off the finished boat- cos the stringers and skin dont represent the ribs, and 2.cant take lines off the ribs alone- cos they are not 100% fair.
but i have a few ideas after today- so i will work on them.
many thanks fellas- for the thoughts and consideration.
thanks
wayne

 

Great project Wayne !
Have you read up the excellent books on designing/sizing and building Greenland SoFs by Cunningham and also Morris ( the latter's book is way out of print and is the absolute bible of SoF-ing if you can find a second hand copy) ?
Both books explain how the get the individual rib lengths correct then then the seam bent correct length rib "automatically" (?) gives you the correct hull shape without any frames or patterns.
Some folk do make a simple bending jig in which one does a lot of/most of the first bending of the steamed rib end.

Mind you, I built my SoF in the Yost fuselage style which is faster, easier and generally lighter than the traditional steam bent 25 or so ribs 'traditional' method.

 

No problem. Take patterns off finished boat. Deduct thickness of stringers and ribs. Re-cut patterns to that line. You now have bending forms for your ribs.

 

Hi Martin,
i am new to the sof way of life!!!
what is the yost style of building?.
by the way, your kayak looks really amazing.
i found a really good tutorial on "instructables" for a greenland style of kayak- i really like the look of them, as apposed to the multitude of other configurations.
i will look for those two books right now!!

where did you get the specs/plans/ lines for your boat

cheers cobber!

 

thanks NED, but its not gonna be so easy- with a single keel strip and 1 chine stringer on each side- it does not give an accurate representation of the ribs underneath..
but thanks for the consideration, and trying to assist, mate.
but i might have to try another route on this one.
wayne

 

Oh well, all you need then is a fair form that goes through three points. That can't be hard to sort. Same basic principle applies.

 

Yost SoF Kayaks

Wayne, thanks for the nice words.
Tom Yost is a VERY helpful chap who as posted his many kayak designs on the internet and they all are free.
See www.yostwerks.com
He has virtually all designs - kids, touring, cruising, rolling, single chine, multi chine, folding, non-folding, timber stringers, aluminium tube stringers, you name it !
His website has detailed Manuals on how to build his craft and lots of pics of the resulting home-built craft. You work from his Table of Offsets - it is not at all difficult to build a very light, striong and sleek kayak from his information

If you have not already joined, I suggest you register and join at least two kayak information web Forums :-
The Australian Sea Kayak Forum where there are great build details in the "Kayak Building" section (including mine titled 'SoF in the West')
http://seakayakforum.com

and the USA Kayak Forum sponsored by Guillemot Kayaks which covers strip built, Skin on Frame and Stitch 'n Glue techniques.
www.kayakforum.com

I have also found Dave Gentry very helpful as well - he is a designer too but probably more of a builder. Google his site.
Also look at Jeff Horton's website Kudzu Craft for more fuselage frame designs. Jeff has a good Building Guide book and has posted a couple of videos on particular aspects of building fuselage frame Greenland style kayaks.

 

just joined, thanks mate!