Basics of canoe materials
by Steven Gates — a long time epoxy/composite boatbuilder, who has been repairing OC1s for the past 3 years. Steve will touch upon aspects of OC1 construction, maintenance, and repair. Steve will also welcome specific questions.
Aloha and mahalo for reading this first article about OC1s. We will cover many aspects of these incredible, yet delicate canoes, from what they are made of, how they are made, maintenance, safety, to the actual repair of them. What makes these boats so light, is also what makes them so delicate.
Most of the canoes today are made with epoxy, as opposed to a polyester or “surfboard resin”. Epoxy is used in the same way as a polyester resin; it is used to wet out a structural cloth, be it fiberglass, carbon fiber, or Kevlar. Epoxy, however, is a far superior product for many reasons. It is 100% waterproof, polyester is not, it is one of the strongest adhesives available, polyester is not at all, and epoxy is flexible and will not crack easily like polyester. Because of epoxy’s flexibility however, boats of all kinds are usually built with a core of foam or wood to add stiffness. This is true even with our OC1s. Most of today’s canoes are constructed of a laminate of carbon fiber outside and inside sandwiching a 1/16” foam core. Carbon fiber offers a much better strength to weight ratio than fiberglass, and combined with the foam core and epoxy, results in a strong, stiff, and light laminate. An important note here…although most paddlers are concerned about the weight of their canoe, stiffness is far more important than weight. A canoe flexing in choppy waters will certainly slow you down more than a few pounds of weight. Having repaired all brands of OC1s both old and new, I can say that the manufacturers are making stiffer and lighter boats than just a few years ago.
You may be wondering now, if epoxy is flexible and doesn’t crack easily, why does my boat have all these hairline cracks? The finish coat, or color is gel coat, a polyester resin product. The same stuff they use on production big boats. It is the first thing done in the construction; the gel coat is sprayed into the smooth mold, and the epoxy/carbon laminate is applied and vacuum bagged over the color. Gel coat is very brittle, and has been traditionally applied fairly thick. If the canoe flexes a bit, whether from a large seaway or from tightening your tie down straps too tight, the epoxy laminate can handle the flexing, but the gel coat will crack. More about these surface cracks next week!
Posted by SteveGates on Tue, 11/19/2002 - 11:43am
Hi Steven,
Can you give us a quick step by step guide to making solid gel coat repairs for small (and not so small) chips and cracks ?
Thanks - Guy W
Wed, 11/20/2002 - 6:00pm
Aloha Guy,
Thanks for your question, a good one that I am sure a lot of people are interested in. In the next article, after further explaining the materials and techniques used in the construction of OC1s, I will try to include a guide for these gel coat repairs. Give me a few more days…..mahalo!
Fri, 11/22/2002 - 10:19pm
Hey Steve,
What about your follow up on gel coat repairs?
Thu, 04/03/2003 - 2:07pm
edit
There are a couple of things to consider before beginning a gelcoate repair. First is it really just a stress crack in the gelcoat or has the laminates structural integrity been compromised? In determining this, consider the cause/location of the cracks. If the damage occured while the canoe was under load it probably goes deeper than the gelcoat. A quick way to check is to try to suck air through the crack. If you have access to a compressor, bucket, sponge and dish soap, you can pressure test the area by gently pressurizing the hulls interior. Be careful here, you could blow a seam!!! Fill the hull with (just a little!!)Air and and swipe the crack with the sponge and very soapy water. If you get bubbles the laminate is probably damaged. Once you determine the severity of the damage consider its location. Some ares of the canoe see more stress than others and require more strength. If the crack is actually more than a surface blemish but is in a low stress area you may be able to get away with a simple gelcoat repair. If you do and it cracks again you will need to repair the laminate underneath. Just a note here: ive built and repaired hundreds of boats and its almost always structural. So lets begin the repair. The laminate of an oc1-2 or a surfski is a very delicate thing and is best handled by a person familiar with this highly specialized laminate. A typical fiberglass guy may do more damage. Your first step should be to take it to a proffesional. But if you insist on doing it yourself consider your skills. Even a simple repair requires knowledge, skill, materials,equipment, and patience. Often times the cost of the materials you purchase for the small repair will cost as much or more than a professional would charge. You then have to deal with storing and disposing of flammable/ hazardous materials. If you have to purchase the equipment you will definitely be spending more than you’d pay a pro. Oh yeah, if you attempt to do it yourself and you screw it up the pro is going to charge more because its a larger repair. All things considered, the simplest way to repair a crack is to take a triangle file and and open the fissure up. Be careful not to enter into the laminate. Using 2” masking tape, mask off the opened up crack with about a 1/4” margin all around. Using 220 grit sand paper sand the crack focusing pressure on the center of the crack. Again, be carefull not to enter into the laminate. Although you focus on the center of the crack make sure you sand out towards the masking tape. The idea is to create a ” valley” which is creating more surface area for the new layer of gelcoat with the deepest part of the “v” at the center of the crack. Try rolling the sandpaper up into a 1/4” roll. If you damaged the tape replace it. Wipe the sanded area down with acetone or denatured alcohol to remove dust build-up and/or oils from your hands. Use disposable latex gloves throughout the process if possible. Don’t use vinyl gloves!!!! Mix a small portion of gelcoat with cabosil before adding the catalyst. It should be the consistency of mayo. Using a popsicle stick or q-tip slather the catalized mash into the sanded area. Over fill the area. Using a degreased razor blade ( use acetone) bridge the damaged area with the razor, keeping the razor 90 degrees from the surface,and sweep off the over filled mash with one clean sweep starting from one end of the repair to the other. Clean off any excess being careful not to touch the repair in progress. Once the gelcoat mash is set hard enough to sand lightly sand it with the 220. This is just a surface sand. Dont create any “valley’s”.you can also sweep the razor blade across to “knockdown” any high spots. Clean the area again with acetone and repeat the process with unfilld gelcoat. If you want to make the repair “dissapear” wetsand it with 600, 800, and then 1000 grit and use a rubbingcompound/ polish for luster. If you have an old boat or know someone who does practice on the old boat first. Good luck! :-), gary.
Sun, 08/17/2003 - 7:05pm
edit