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New kayak design, is it good? Answered

Hello everybody! I've moved most of my robotics projects to Let's Make Robots (All LMR are belong to us!) and I'm gonna do some wood-working now!
I decided to build a kayak. Why? I dunno, I want to build one, and I always wanted to go kayaking. No I'm not gonna go take lessons (tips/tricks are welcome), I'll train myself. I'm expecting a couple capsizes. LOL.

Anyways, I found a program that helps to design kayaks called Kayak Foundry. The software tells me where to put the sheer strip, where the waterline will be, and it also generates the forms to build from.
The only problem I have is that this thing will cost $400-$450 to build. Before I invest that kind of money in a possible failure, I need to know if I have a stable design. Below are the cross sections and a model I made in Google Sketchup (gotta love free software!). Take a look at them, I need to know:
-Is the design stable
-Will it float with a 185lb man in it
The software gave me a stability rating of 90 (out of 100, with 40-50 being a racing kayak)
Also, there are pictures of data from the software. the red line on the graph is my design, the black
line is the target. Also, on the volume distribution curve, the line should be right in the middle (the cockpit or whatever it is called should be in the middle of the boat.) I guess I forgot to save or something.

If you can help, please do. I'd rather not spend $400-$450 dollars on an unstable boat that always capsizes.

Thanks,
Gimmelotsarobots

17 Replies

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KudzuCraft (author)2011-04-08

And I meant to add, the stability factor is not 1-100. It actually goes up to 200+ 100 -110 is a good number for a new paddler.

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KudzuCraft (author)2011-04-08

You really should post this over at BlueHeron where you got the software. There is a forum and you will be really good advice there. Hard to say without seeing the boat file but I see what I think are some problems in the image.

And please don't take this wrong but your styling could be improved a little.

Bottom line is building a stripper is a HUGE amount of work. Your really need to let us look it over and make sure you get the most possible for you effort.

http://www.blueheronkayaks.com/phpBB2/index.php

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sparkplugs (author)2010-08-15

can I get a fiberglass kayak from this company?

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trike road poet (author)2010-08-13

I built several boats over the years, and used the plastic sheeting used to make those heavy duty totes used by the U.S. mail. Plastic houses can get you the stuff (It looks like a white plastic version of corrugated cardboard.) I used a rental hot-air welder to make the seams, and it was easy to seam and seal. The material is slippery, water proof, and light. I built a one man punt for fishing that cost me about $230 to make, and it last for five hard years of service and outside storage until I sold it. Check out the material, useful for a lot of things and not all that expensive.

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T.Rockwell (author)2010-08-12

check out this instructable..... i think its gonna end up being my first attempt at kayak building!!. instructables.com/id/Stitch-and-Glue-Kayak/ very interesting without getting too complex, and really quite nice looking..... plenty of room for personal mods too...

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zieak (author)2010-01-12

I don't have experience building kayaks but i have at least a few hundred hours of time in them...

Your profile looks like it has good primary stability which is what you'll want for casual paddling.  Secondary stability has more of a V shape hull.  You want a flattened out U. 

One observation (from a decade of pool sessions) is that you might want to consider building bulkheads in the boat and putting hatches in.  Inflatable flotation bladders don't do nearly as well at keeping water out and enabling getting back in the boat.  That said, with high primary stability hopefully you'll never accidentally get in the water.

I bet that if you build it and decide it is too tippy, rides too low (I have no idea about how the waterline would end up on a boat), or whatever, I'm sure you could sell your creation for at least your materials.  Most kayakers love the look of a wooden boat. 

I had a college professor that taught a traditional kayak construction class.  They used no tools for measurements other than the body of the person building it.  That was canvas stretched over a wooden frame. 

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gimmelotsarobots (author)zieak2010-01-13

So that's what bulkheads are for on a kayak! The very middle (around the cockpit) is a flattened U, will that help any? What is the difference between primary and secondary stability?

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zieak (author)gimmelotsarobots2010-01-13

A good flattened U in the center will give good primary stability - making it stable when you sit straight up.  Secondary stability would kick in with a more V shape - it would sit on either side of the V well.  The V shape is better for cutting through the waves - which is why you come to a nice V at the bow.  A high secondary stability boat stays nice and steady while moving swiftly but when you slow down it becomes less stable. 

The bulkhead makes for great storage but i usually use a drybag regardless.

Depending on what kind of paddling you plan on doing consider your storage solutions for the deck.  If you'll be wearing a spray-skirt it is really nice to have bungees in front and behind you for a map case, water bottle, camera... but make sure the fasteners are not positioned where they will bump your hands or dig into your thighs if you do a hard brace with your legs inside.

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gimmelotsarobots (author)zieak2010-01-13

I plan on going down some small local rivers and paddling round the lake.
How do you make the bungees water-tight? I don't really want storage in the hull.

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zieak (author)gimmelotsarobots2010-01-13

When we would put rigging on the deck we just drilled through the hull and used a kit that included the screws plastic parts, and bungee cord.  It may not have been waterproof in the end but some caulk in the hole before putting the screw or bolt in wouldn't hurt.

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gimmelotsarobots (author)zieak2010-01-14

I have another question, would 40 feet of 6oz fiberglass be enough to cover this boat? I was thinking that since this is a 17' boat, 20 feet for the top, and 20 feet for the bottom might do.

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zieak (author)gimmelotsarobots2010-01-14

I'm sorry - I've never done any fiberglass work.  If it is measured in square feet then i would take the width of the boat and the length of the boat to calculate the rough surface area of the top or bottom.  If your boat is 24 inches wide at the center and 17 feet long then that's 34 square feet. (Realizing that at the bow and stern you need much less and that the calculation is ignoring the "sides.")  So i think you would want about 70 feet.

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gimmelotsarobots (author)zieak2010-01-14

I wasn't talking square feet. The fiberglass I want to order is 60 inches wide by any length you choose.

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zieak (author)gimmelotsarobots2010-01-14

In that case it sounds like 40 feet would be plenty!

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gimmelotsarobots (author)zieak2010-01-14

Great, but how do I get $400 before the winter ends (humidity in my area during summer would warp the wood badly)?

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Tool Using Animal (author)2010-01-12

do you have experience with either boat design or construction?

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I have no previous boatbuilding experience. However, I have carpentry experience, I learn fast, and I did lots of research about strip-built kayak construction. I'm gonna practice fiberglassing on some scrap wood so that I learn the technique before possibly screwing up the kayak. You got any tips?

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