Building my first kayak....help!

Any Skin-On-Frame kayak builders out there?
I've started accumulating supplies to build a Yost Sea Rider, a 17 foot Greenland boat.
We have no clear cedar in my area, so it looks like I'm going with pine. Covering will be urethane coated ballistic nylon.
This boat is 4.5" inches narrower (19.5") and 4.5' longer than my longest boat currently.
Any advice appreciated!

Dryer - man you came to the right place. I have a medium sized library of polar peoples including one classic on skin covered kayaks, the whole skinny.

First off you know that the boat MUST be built for YOU. I'll dig up the book and the info. but just as exampple - perhaps the keel, should be twice your height pluse one upper arm including the outstretched fingers. Every dimension is taken from the body of the owner, the kayak is magical and must be properly made to please the seal god so the hunter will be successful.

There are a great many types of skin kayak - what type were you thinking of? Will you copy a traditional design?

Unfortuately the skin kayak is sort of a living thing and almost all of them in museums have been destroyed by drying out.

More later
Jim <img src="/forums/images/graemlins/cool.gif" alt="" />

Paul-

check out:

http://www.foldingkayaks.org/phpBB/viewforum.php?f=27

the folding kayak forum has quite a few people all over the world who are building their own kayaks.

Good luck!!

Don Hall
KQ6KV Ca

Jim, if the seal god smiles on me here, it truly will be a miricle! <img src="/forums/images/graemlins/grin.gif" alt="" /> I'd have to go to the Dallas zoo to get me seals....

Yes, I've got my design already and am making tweaks to fit me. It's a Greenland style, low volume boat, 17.1 feet long. Not building a traditional rib boat yet. Thought I'd try something a little simpler (same lines though) first.
The tricky bits are transferring 'offsets' to wood, and then "which wood". This boat is a single chine design with a little bit of rocker built in. I don't need the rocker here so I'll flatten it out some.
These low volume boats have a combing thats smaller and lower than anything I currently own and getting into the thing looks to be a trick. It's also 4" narrower beam than my skinniest boat. As you say Jim, it's made to fit.

Here's what I'm building:
http://yostwerks.com/SeaRiderWoodFrame.html

Mine won't have the clear skin though. I'll be sewing on a nylon skin.

Really nice looking boat. I've always wanted to try a greenland type.
The closest I came was a Nordkapp, way too tippy for my at 19". ha ha

I think reducing the rocker some isn't a bad idea for lakes, but I would be careful what it does to stability. Hmmm. Let me think about that a bit.


All else being equal reducing the rocker should...
1. Increase the prismatic coefficient some, and possibly the surface areas also, which usually means slightly better high end speed but somewhat higher cruising drag, which you sort of had already by virtue of long and skinny.
2. Better tracking.
3. Essentially, less rocker will make it seem even longer and skinnier.
4. I'm not sure about the effect on stability. You gain some waterplane beam in the ends but lose some waterplane beam in the middle. What's even less clear is the effect on secondary stability. I think initial stability might stay about the same and secondary stability might go down.
5. Your center of gravity will be slightly higher also, this will reduce stability for sure. Maybe not much.

The other thing you really have to watch for is your total weight, and your center of gravity. As you probably know, heavier guys need wider boats. That's all there is too it. Just 1/2" can make alot of difference though. Keep in mind reducing the rocker will raise your center of gravity also.

Remember your basic theory, at least for initial stability...

Height of metacenter = I/V
I = Area Moment of Inertia of Waterplane, a function of beam^3 x length
V = ( weight of you + your boat + your gear ) / density of water

You are in fresh water also, I think. This also means more volume, and thus a lower area moment of inertia, so less stability again even though your center of gravity drops a little also, just not as much. I think that's right anyway. Not sure.

Anyhow, I think you have the software for all this. If you don't Jim does. Also you pretty much have to do eskimo rolls with this type, though they are easier, as long as you have the energy. Alot depends on how hard you want to work to stay upright, how long your trips are. That nordkapp was lots of fun, but I didn't go too far from the dock that day. ha ha

p.s. 17.1' seems rather short for 19" beam. Maybe not. Depends on your size. I prefer a shorter boat myself, but mine is 16.5' long and 23.5" wide, single chine. That is actually wide enough for me to wet exit and re-enter. I add some foam on the inside sides of the cockpit, too reduce free surface effect when swamped. Works for me and makes it a great boat for the Bay. If I went skinnier, like more towards a Greenland type, working with a total displacement of 220#+60#+40# = 320 pounds, I might go to 20' x 21". If I got my weight down to say 170+40#+20# = 230#, I might go to 19'x 19.5". With some more skill, maybe 19' x 19". Maybe. Depends again how hard I want to work. ha ha

Definitely try out a boat close to what you think you want to build. Cheers.

This site in New Zealand is very interesting and informative. I would still rather try a traditional Greenland type, but this guy seems to be very experienced and knowledgeable and so the site has alot of good ideas that might help you understand and appreciate all the merits of a good kayak, including the traditional greenland type even though its so different. Definitely not inferior, as long as it fits. I think that's the key like Jim says.

http://www.sissonkayaks.co.nz/

Here is my kayak. It's a bit heavy and rough around the edges, but performs really well. I need to make it a little more watertight for the Bay. Thinking of getting rid of the hatches altogether. I take very little gear when I go, and it can pretty much fit with me in a drybag between my knees. I've even thought of modifying it into a semi sit-on-top. I like that because I could dress for the water without getting overheated inside the boat.
http://www.seaknife.com/sk17.htm

Wow, thanks, JAK!

One thing I've learned while doing my reasearch is that most, if not all, of the late kayak designs are done on boat CAD software. Hopefully, all those parameters you mentioned are taken into account in the design. I've designed/optimized telescopes and antennas this way on specialized software....it's a big time saver. The 'offset' tables are in decimal inches, which has been a pain, so I converted it to metric. I've never worked with "offsets" before, so this is a learning experience for me.
Two things concern me about building such a low volume, skinny boat....my weight (180ish) and the fact that salt water is 5 hours away, meaning, I'm dealing with fresh water displacement. This boat is designed for a 190 lb. driver, and assumes 15lbs. of gear. I'm hoping that gives me some headspace in the design.
The boat I'm building is designed and used in the Denver area, so fresh water is the medium. It's also a 'low draft' design, meaning not much of it sticks out of the water. This is good in that wind won't effect it as much, but I better be wearing a skirt or we'll become a submarine.
Like all my boats, I'll stuff all open space with pool noodles for flotation, and to take up volume. A sea sock is recommended....still thinking about that one.
I've decided I don't like hatches...my three yaks all have 'em...but I think I can save weight and headache by using drybags instead. I'd rather have deck perimeter lines and bungees on top, instead of fixed hatches/bulkheads.

My 13.5' boat is 23.5" beam, is flat bottomed with a 1/2" keel, and is quite stable and fast. With a bit of rocker and the extra 2+' of wetted area, I'm thinking 19.5" inches should be manageable...a little better than a surfski, since my center of gravity should be lower.
I'm thinking of lengthening the design slightly and raising the combing a tad. That's the enlightening part of skin-on-frame....you can change your mind in the middle of the design.

I'll try and wrap my brain around all this.

Jim?....software? What's recommended??

Dryer
Nice looking boat, looks like plywood ribs. <img src="/forums/images/graemlins/grin.gif" alt="" />

I spent some time looking up the classical stuff last night. <img src="/forums/images/graemlins/wink.gif" alt="" /> The first thing to do is to determine the use for your kayak. You will either be hunting Caribou in rivers <img src="/forums/images/graemlins/shocked.gif" alt="" /> and they swim fast - thus the longer kayaks with rocker which makes for less wetted surface area.
OR


You will be hunting Marine mammals and there stealth not speed is required, that and a flexible frame that will give in a seaway. <img src="/forums/images/graemlins/smirk.gif" alt="" />

Don't forget to treat it with boiled seal oil once a month. <img src="/forums/images/graemlins/blush.gif" alt="" />

Oh and a really nice extra is a kayak sled to get it from the flow onto open water. <img src="/forums/images/graemlins/grin.gif" alt="" />
Jim

Jim, do your book sources say anything about the kayaks of the Southwest Texas desert people? I understand seals were hunted to extinction in the Rio Grande and that global warming made the Texas-Mexico ice flows completely disappear. I definitely feel a kayak connection with those ancient people but archaeological evidence is really hard to find regarding their maritime adventures. <img src="/forums/images/graemlins/grin.gif" alt="" />

As far as stealth goes, I'll be painting the yak with the same stuff that F-117's are coated with. It's like seal oil only updated just a tad to keep the radar signature
at a minimum. That way if I see any caribou swimming, they'll not detect me until I'm ready to pounce with my lance*. It should also buy me some time in the game warden's interrogation room. <img src="/forums/images/graemlins/cool.gif" alt="" />

* considering a contact mine laying kayak and foregoing the lance.

Dryer
That looks like an interesting design. Since my knees are not what they used to be, I've been thinking of switching to kayak from Canoeing. Plywood frames makes it simple. Here's an idea - I built a light weight sailboat years ago with a similar frame - that is with conical sides and similar frames. I bent Luan door skins - 3 ply 1/8" wood over the frames and nailed with bronze annular ring sailboat nails. It makes the boat extremely rigid and durable, yet light.

I may try it. You need to have very carefully planed frames so the skin sits on and glues to nice flat spots. It would require a more carefully made frame than a cloth cover, but it would be nicer I think.
Jim <img src="/forums/images/graemlins/cool.gif" alt="" />

This is sort of important <img src="/forums/images/graemlins/grin.gif" alt="" /> <img src="/forums/images/graemlins/grin.gif" alt="" />
I think the desert Eskimos were killed 200,000 years ago. <img src="/forums/images/graemlins/blush.gif" alt="" /> and theres been several ice sheets in North america since. <img src="/forums/images/graemlins/tongue.gif" alt="" /> There is an ancient site of that age in the Mojave in California. Its a BLM site called "Calico early man archaeological site" Its the OLDEST human site in North America. I've seen the relics - its convincing, been there twice. But the age of 200,000 years means that they must have been neanderthal - perhaps Bigfoots ancestors? <img src="/forums/images/graemlins/blush.gif" alt="" /> <img src="/forums/images/graemlins/grin.gif" alt="" /> Contact the BLM Barstow Resource Area, or friends of calico early man site, PO box 535, Yermo, Ca 92398.
Jim

Jim, I paddle with a guy who builds strip kayaks. They are so pretty they look like fine furniture. Fiberglass sandwiching the cedar strips, and the epoxy makes the glass weave go completely away to a glass smooth finish.
"Stitch and glue" is the same idea, only using plywood and fiberglass.
I'm looking for a fast build and want something really light weight. An 'ultra-lite' hot rod to do 'ultra-lite' camping with. Skin-on-frame fits the bill for me. Instead of vinyl, I'll be sewing on ballistic nylon with a single seam down the middle and sealing it with two part polyurethane varnish to make it like plastic. Re arching the building method, I believe I can measure just about any kayak or canoe and duplicate it using skin-on-frame. The 'ancestors' had some serious tech going for them, still relevant today.
I've paddled canoes all my life....still have a nice 19ft. Grumman with a flat transom....but once I paddled my first kayak, I'm hooked. A fleet of three and a forth about to be built No knee problems, much swifter in the water, and easier on the back when loading on the car top. The perfect boat, IMHO.
Why not build one with me?

Check into these: Pygmy boats . My sister and her husband have built several kayaks and these are their overall favorites for lightweight versatility. They were also the quickest to build.

This is my sister in hers:
[img][image]http://i30.photobucket.com/albums/c342/prabson/Paminpygmy.jpg[/img][/image]

Believe me, Mockturtle, I've drooled all over Pygmy's website. Probably the best kits out there but pricey. I've got the tools to slice wood and skin on frame will get me a really light boat, at under $300 in the end, compared to $700 for a kit.
I guess it's my time that make Pygmy's smart, but buying up the parts is part of the fun, for me.

Beauty looking boat. Wooden boats and skin on frame are both lighter than fibreglass also. 40# is a good target, and easily achievable with stitch and glue or skin on frame. Keeps the material cost down also. Most production kayaks in fibreglass tend to be upwards of 60 pounds, and very expensive also. Mine wasn't too bad as I got a deal second hand, but I will build the next one after I play around with this one and turn it into a semi sit-on-top.

I've often wondered about the Micmac ocean going canoe. It was sort of half way to becoming a kayak. Originally very narrow with lots of tumblehome, and a bump in the middle. I've thought of scaling one down for a single. My thinking is that there must be a reason kayaks are traditional only in northern waters, and that more open designs might be better suited as you go further south. I think sit-on-tops are a partial reflection of this. I think canoes could be re-invented, or at least deserve another look. Way too many tubby canoes out there. I have seen some marathon canoes that are real beauties, and the traditional birch bark canoes of the Mik'maq and Malecite and other tribes were absolute marvels in engineering, and still are, even to this day.

I have no experience building kayaks, but I've got to mention this...

My neighbor built a homemade airplane. While working on it he took fiberglass cloth (the kind that looks like burlap) and coated it with high temp silicone gasket sealer (the same kind you use on auto gaskets) using a "Bondo" spreader. I think he may have developed an entirely new material when he did this.

The result is a super tough, flexible, heat resistant, waterproof material. I've worked with many different media while building different projects over the years and I can tell you that this stuff is pretty darn cool.

You should be able to coat one side with silicone sealer, lay the piece in or over a mold, and coat the other side with epoxy or polyurethane resin to make a hard part (as opposed to flexible). Of course, you should be able to use kevlar or graphite too.

It's cheap and easy to make a fiberglass sample yourself to test and play with. You might find it has an application that fits your project... If nothing else it'd make the world's toughest Dry Bag <img src="/forums/images/graemlins/smile.gif" alt="" />

That a cool project you're working on and a beautiful boat design you've chosen. While this may not be much inspiration, here's the last boat I built (sort of). I wanted to build a sailboat with off the shelf items for a total of no more than $100.00. I pondered this a lot before coming up with the "Hobocraft" below:

Bill