A couple of years ago I’d posted a question about repairing a small crack in the bow of my friend’s fiberlar bell canoe. We ended up applying a very small fiberglass patch using a West system repair kit and then applying gel coat from Bell over the patch. The gelcoat that was applied over the epoxy broke off and had to be redone after a collision, but other than that it worked ok. Now this same boat is again in need of repairs, this time major patching of multiple ~6" tears that go through the hull. (a result of pinning on a log) Epoxy resin seems to be the standard in most discussions of canoe repair, but Bell now lists vinylester resin available in pint or quart quantities on their website. What are the advantages and disadvantages of vinylester vs epoxy for applying fiberglass patches to a fiberlar layup boat? Thanks in advance for your insights.
The advantages of epoxy are that it
is a little stronger than vinylester, AND epoxy keeps, while vinylester will harden in the container within a year or two.
I have patched with both West epoxy and with vinylester. Both are nice and thin, wet out cloth well, and result in strong patches. I find epoxy more controllable and predictable in its setting time. I encourage you to get West epoxy, the faster 205 hardener, and the pumps.
I'm very sorry to hear of all those through-the-hull tears. If the boat is not to be used in whitewater, it might be possible for you to do the major patching on the inside of the hull. That will leave the owner feeling less bereft of gelcoat on the outside. Personally, I patch for strength, and I don't care about gelcoat.
Rather than launching into my usual lecture on patching (dishing out, bias-cutting concentric patches, laying on the LARGEST patch first, and so on down to the smallest), I'm going to check to see if Walbridge's "Boatbuilders Manual" is still in print in its final (1987) edition. It describes the standard patching routine. Otherwise, I think I need to write up what I have learned and keep it as a document to send to those who need it.
Don't dismiss the possibility that a powerboat repair place or a Corvette body shop might do an adequate repair for an acceptable price. You will be out at least 60 bucks for the epoxy and pumps, but you may use at least half of it.
Inside patches are often done in Kevlar, but if the boat is glass inside, probably E-glass patches will do.
I see that you are in LA. We go to New Orleans fairly often to visit our daughter. If it seems useful and logistically feasible, we might be able to drop by for a look at the damage.
pnet post
hi angstrom has a post in paddler discussion board for a link to epoxy supplies on sale , in case ya need some.
I’d avoid power boat repair places
I’ve seen kayak work from a few and it was terrible. The problem is that power boats have MUCH thicker hulls and the tools and materials used to repair them are designed for removing and replacing large amounts of materials. They’re not appropriate for a kayak or canoe with a 1/8" thick skin. For example, kayaks are typically made with layers of 6-9 oz./yard woven fiberglass. Boat hulls are usually repaired with layers of 18 oz. “woven roving”, sewn to layers of chopped-strand mat, which can weigh over 20 oz./yard ounces/yard. While it can be made to work, it’s not ideal.
Someone who works on car bodies, snowmobiles or other thin fiberglass skins may do a good job on a kayak, but you may still need to specify that you want the repair done with woven cloth rather than chopped-strand mat, where it’s appropriate.
Both materials will work…
...as G2D stated, but I also prefer using epoxy for repairs, for the same reasons he mentioned. If you are going to apply gelcoat over an epoxy repair, here are some key things to remember:
1- The epoxy must be fully cured. If you're trying to get the repair done in a couple of days, this typically means that you will need to apply heat to the repaired area to accelerate the curing process. I use electric heaters or shop lights to raise the temp of the repaired area to over 100 degrees, which dramatically speeds the curing and also increases the strength of the cured epoxy. If you cannot do this, full curing will take anywhere from several days to several weeks, depending on the ambient temperature. If the epoxy isn't completely cured, you may find that gelcoat that you apply over it won't cure.
2- Before applying gelcoat the epoxy surface must be COMPLETELY clean. It is absolutely essential that all traces of amine blush be removed and even with "non-blushing" epoxies, I don't take any chances. My preferred method is to start by scraping the patch with a carbide scraper to completely remove the outer surface (steel scapes work but dull quickly). Next, I'll clean it with lacquer thinner (not "paint thinner", which is mineral spirits). Only then will I do any sanding. If you start sanding right away, you will sand any impurities INTO the surface, making them much harder to remove and creating the potential for bonding problems with the gelcoat.
3- You should sand the epoxy surface with 80-100 grit paper to give it some tooth, then clean it with lacquer thinner again.
4- Use "finish" gelcoat (a.k.a. "waxed gelcoat"). The more common "laminating" gelcoat will not cure when exposed to air, but finish gelcoat will. There are also gelcoat paste products on the market which are waxed and work really well to prevent runs on curved or vertical surfaces.
Once the gelcoat is cured, sand and buff as necessary.
I have pics of this process in my repair albums at:
http://community.webshots.com/user/brian_nystrom-reg
Have fun!
Epoxy is the king
Vinylester is a more refined polyester that is supposed to have better lay-up properties. However it does not bond easily to already hardened vinylester or polyester. Epoxy has tremendous adhering qualities and that's why it is the unanimous choice for repairs. It's bonding strength is unbeatable and it has more flexibility and wont crack easily. The reason boats are not made from epoxy is because it's expensive and polyester does a great job for making a casting with fiberglass cloth such as a boat. Once it's hard, it will bond to itself with good preparation but nowhere as good as epoxy. Use epoxy for your repairs.
check out this brand and prices:
Raka.com Many wood builders use it and it gets great reviews. Get the blush free hardner.
Well, see, we had some PB/Corvette
guys in Georgia go into making glass/Kevlar canoes, and they did a good job, and good repairs too.
J, the vinylester I used to
get from Noah made a very good bond wherever I used it, on polyester, vinylester, and epoxy. If you check the composition of vinylester, it actually has epoxylike molecules in it. I don’t think Bell would be handing out vinylester for people to repair Bell canoes if they thought it was inferior to their vinyester.
Also, epoxy does not have a big edge in flexibility or hardness over vinylester. My Millbrook vinylester boats are just as surface-hard and just as able to flex without splitting as my Bluewater and Dagger epoxy boats. For that matter, my '73 Mad River Compatriot made with polyester was no slouch, though it had problems with hydrolysis that vinylester and epoxy boats don’t have.
I prefer epoxy, but properly formulated vinylester comes real close for boat construction. My only issue with it for repairs is that it does not “keep” once promoted.
More info
Send an email to info@placidboatworks.com and I will return the Bell/Placid repair protocol along w/ pics.
charlie
Thanks everyone for your advice!
It sounds like the main disadvantage to vinylester is that the unused resin won’t keep for future work. My friend was inclined to order the repair material from Bell and he may still want to do that. I think we’re optimistically hoping that more repairs after this one will not be necessary :).