Fibreglass kayak building

[lisa_w]

Hey, i'm pretty new at this, i was wondering if i can get some info about building fibreglass kayaks. I want to build a moderate sized sea kayak. I have built surfboards before, had no trouble. I just really have no idea on how i make the molds for the kayaks. i have a friend building a wooden kayak, i dont really want something wooden. So basically if anyone could help me out that would be awesome, any tips help.

[frosh]

Hi Lisa, No-one in their right mind builds a fibreglass kayak (one only) by first building a mold and then taking a single kayak off the mold. What is wrong with a wooden boat anyway. I will give you a web site that sells plans and kits for wooden kayaks of many different designs of very high quality.
You can always sheath the outer surface in fibreglass if you want a tougher surface finish.
Any way, even if you could borrow a mold, the chances that your first attempt to produce a boat off the mold, unless you had expert help would not give you a really good result.
I would go with a kit, as the quality of the finished product is virtually guaranteed as is the design, because you have some construction experience already.
http://www.clcboats.com/boats/shearwater.php

[marshmat]

Welcome aboard, Lisa- good to see another Canadian around!
Building moulds is essentially like building three whole boats. The first step is to make a plug- essentially an exact replica of the part you want, made from whatever materials you're able to work. I'm doing some out of monolithic blocks of MDF board right now, it's very tedious. Then you make a fibreglass mould from that plug, and give it enough of a backing structure that it can't flex at all. Then you make the boat in that mould. As you can see it's quite an efficient way of making a lot of identical boats, but it doesn't work too well for making a single boat. There are ways of getting the mould directly provided the shape isn't too complicated, but they're all kind of tricky and require a lot of careful hand fairing as well as being pricey.
If you don't want wood (and there are some really, really strong, light and gorgeous wooden canoes and kayaks out there), or glass-over-wood, a kit is probably a much cheaper and less stressful way to go for a single composite hull.

[lisa_w]

actually i wasnt just going to make one boat, i was a little worried about copying someone else's design, i was thinking of making about 6-12. I dont actually know what the laws are on taking a mould from someone else's kayak design, but i think it would be a crappy thing to do.

[Sean B.]

what I would do if building a one-off sit-in style kayak in glass....

glue blocks of (either expanded or extruded) styrene foam together to get the overall size.... shape the foam to the shape of the kayak you want (same process as shaping a board... planer, surform, sandpaper)... completely encase it in epoxy/glass composite... now you have sort of a pontoon.

after the resin has completely cured, cut out your cockpit and whatever hatches you want and remove the fiberglass piece from the cockpit & hatch holes.... using either mineral spirits or acetone (you could use gasoline too, but I wouldn't at today's prices), pour it into the holes you just made. now you can scoop (or pour) out the styrene.... the acetone reacts with the styrene and basically "melts" it away into a gel/liquid form.

I believe this process is called "lost mold"... works great for a one-off, but kind of messy.

[marshmat]

Originally Posted by lisa_woot

actually i wasnt just going to make one boat, i was a little worried about copying someone else's design, i was thinking of making about 6-12. I dont actually know what the laws are on taking a mould from someone else's kayak design, but i think it would be a crappy thing to do.

This is called 'splashing', and it is both illegal and disrespectful to do so. If you're thinking about perhaps building a fleet with some friends, then you could probably negotiate a very reasonable royalty with the designer of a boat you like. Or you could design your own although then you need to learn a lot about how to do so.... If you're thinking of building boats for profit, then I'd quietly lay such dreams aside for the moment as "profitable boatbuilding" is an oxymoron of the same type as "honest politician" or "military intelligence".

[frosh]

Hi Lisa, I don't like the sound of the lost mold method for at least 3 reasons.
Firstly it wont give you ability to build several boats economically. Second it is difficult to get a fair shape by carving polystyrene and very messy to plane or sand. Thirdly acetone attacks epoxy resin strongly even after it is set and softens the surface leaving it sticky.
Another idea is to go to a canoe building factory and make an arrangement to rent a good quality mold providing they have the ownership over the design.

[JEM]

I did a decked canoe design for a customer who wants to do exactly what you're doing.

He's using the method prescribed in the book Building Your Kevlar Canoe: A Foolproof Method and Three Foolproof Designs

Toughest part will be assembling the deck to the main hull. But since it's using a male mold and building only one, you can take the time to do it and make it look nice without having to worry about production time constraints.

[jasman]

I'm yet another Canadian. I just recently purchased some molds and hope to learn how to fibreglass them. I've posted a couple of questions looking for help in learning how to fibreglass.
Are you near Peterborough by chance?

[JEM]

me? No. North Carolina, USA.