More details on construction
Thanks for the interest.
Skin is 600g/m2 on the hull, 400g/m2 on the deck. There are zips most of the length of the front and rear deck, the assembled frame goes in through the rear zip opening and then everything is tensioned and zipped up. There are 5 longitudinal cords that are tightened up to maintain rocker and rigidity, I might be able to reduce that to three cords.
The main tubing is 19mm ID/21.4mm OD/1.2mm wall, the ferrules are 16mm ID/18.8mmOD/1.4mm wall made by C-Tech Carbon Tube - Round - www.carbon-tube.com in Auckland, NZ. There are 5 four metre long stringers (keel, 2 chines, 2 gunwales). Each is made of 4 one metre sections with a ferrule glued in one end and shock corded together. (For the Americans 19mm is about 3/4 inch, so OD of main tubes is a little bigger than 3/4 inch)
The end frames are made of HDPE and are/need to be quite strong in all directions. There are 4 intermediate frames of 12mm marine ply with a few bits of WRC laminated on where necessary. Ply frames are at the footrest position, front and rear of the cockpit and middle of the rear part of the kayak. It might be possible to design to eliminate the middle rear frame, but with the asymmetric swedish form (LCB is 54%), it's needed to hold the shape back there, and in any case helps support the rear deck in a re-entry following capsize if you don't roll. The ply frames "snap" to the carbon stringer to some extent, at the moment they are held together with velcro straps where necessary, but I plan to make two small trianglular HDPE snap connectors for each corner and screw them on either side of the ply. Details/pictures soon.
The cockpit rim is laminated from 12mm and 4mm ply and is hinged so it folds in half.
Bill P - I'd be prepared to send you a table of offsets (Similar format to Tom Yosts) if you wanted to have a go at this or a similar design. Be aware it's built around me (70kg, 175cm height), and is quite narrow (52cm beam, but waterline beam of 43.3cm which is quite narrow, tippy). It's easy for me to make adjustments to LOA, beam, waterline beam, position of footrest cross frame to suit, so if you are interested let me know your leg length, weight and desire for stability and I can fiddle things accordingly. Also, what build method are you thinking of - copy of mine with carbon, non folding wooden or aluminum tube following Tom Yost more closely.
More with pictures soon, probably on Wednesday morning.
Ian
"Determination and self belief"
Hi Brian, good to hear from you. "Determination and self belief" - maybe, but I also had a fair idea of what I didn't know, and the journey I'd have to take to get there.
One big plus of the folding skin on frame kayak method is if you stuff up the design, go too far out on a limb in some direction, you can always take what you learnt, redesign, pull the frame apart, make some new frames from ply, put it together with a new skin and try again, so it was knowing that that I spent $1000 on some carbon tube. (Please don't tell my wife!) It's also possible to make cheap cross frames, put them in temporarily with tape, wrap it all in polyethylene sheeting and duct tape and give it a try on the water before finalising the construction (though I didn't do this)
Spend $1000 or more on ply, timber and epoxy, glue it all together into a sailing boat, put it on the water and find it doesn't work and there's not much you can do with the result. If you do come up with something new and it actually works really well, then if you do more looking, you'll probably find you've re-created something that someone else has already designed!
I didn't do any prototyping as described above, I just built my kayak complete, put it on the water but I'd done a lot of computer modelling so I knew where the waterline and longitudinal centre of buoyancy and such like would be. I also downloaded line drawings or pictures of every kayak in the range of designs I had in mind, overlaid them with what I'd come up with and analysed where mine was different and what the consequences would be.
A kayak is also much easier than a sailboat, the kayak is purely a displacement hull, there is only so much that you can vary and get wrong.
For those who feel inspired to follow the amateur self design route, I'd still recommend caution. I'd agree with everything that real designers such as Michael Storer, Par, Ross Lillistone have said on this forum and elsewhere about the pitfalls of designing or modifying designs yourself, it's much more complicated than you think. On the other hand, all these guys started somewhere (Par at age 10 I believe).
A sailing dinghy has to work in both displacement and planing modes and transition between them, and there are the issues with lateral balance and the way things scale with size. Stability scales with the forth power of size, displacement hull speed with the square root of length, foil lift with the square of speed... There's also all the structural stuff.
If you understand all these things and lots of things I haven't mentioned/don't know about and have built and sailed half a dozen boats yourself and start from something existing that already works, and enjoy a challenge and the possibility of failure, then go for it!
I did see the article on the boat named Alice, I thought the construction out of lots of very thin tube made it very complicated and fragile, (but was dictated by a source of cheaper tubing?). Was his down to 10pounds? Mine uses only 5 longitudinal stringers which are quite solid at more than 3/4 inch dia. When I figure out simplicating the end frames and cockpit combing, it could be built quite quickly and easily. My aim was to build the strongest expedition capable boat I could at around the 10kg mark rather than the lightest possible kayak. I can stand all by weight on any one of the cross frames, and I'm sure it would be OK going end over end in big surf as long as the end didn't hit the bottom. (I'll post some pictures once I've completed sea trials at St Clair beach, Dunedin)http://farm2.static.flickr.com/1046/...8c596c.jpg?v=0
Have to go now,
Ian