Brian Nystrom Posted September 8, 2004 Share Posted September 8, 2004 Scott managed to knock a hole in his Explorer, so we did an impromptu repair session over the long weekend. I've posted some pics in a Webshots album at: http://community.webshots.com/user/brian_nystrom Quote Link to comment Share on other sites More sharing options...
ccarlson Posted September 8, 2004 Share Posted September 8, 2004 ...and very useful info as well. Only a matter of time before I'll need to put it to use ;-) Quote Link to comment Share on other sites More sharing options...
alan Posted September 10, 2004 Share Posted September 10, 2004 Thanks Brian! Those are great! How would, if at all, the process for repairing a kevlar boat differ? I've got quite a bad ding on the keel which will need reepair. Also, in the last issue of Sea Kayaker Magazine, they did a bit on applying a keel strip. Wish i applied one BEFORE my last trip! ;-) Any experience with that?AlanCD Andromeda - red on whiteDagger Id 6.9 Quote Link to comment Share on other sites More sharing options...
Guest guest Posted September 10, 2004 Share Posted September 10, 2004 Brian,Why did you used Epoxy Resin rather than a Polyester that the boats are originaly built with. I know its stronger, but doesn’t the Polyester cure faster and it is as strong as the rest of the boat anyway right?Isn’t the gelcoat a Polyester resin ? Quote Link to comment Share on other sites More sharing options...
Brian Nystrom Posted September 10, 2004 Author Share Posted September 10, 2004 The major difference with Kevlar is that you can't sand it, or it will become a fuzzy mess. I haven't done any Kevlar repairs, so I can't give you any tips other than to make sure that the fabric is fully encapsulated in whatever resin you use. If you need to fair it, use a scraper rather than sandingIf you're just talking about a gelcoat repair, there's no difference between glass and Kevlar boats.As for the keel strip, the method used in the article looks good. I plan to try it on one of my boats, probably my terribly abused Pintail. Quote Link to comment Share on other sites More sharing options...
Brian Nystrom Posted September 10, 2004 Author Share Posted September 10, 2004 I used epoxy for the extra strength it provides. Once the hull is holed, you no longer have a continuous laminate and the extra strength of epoxy helps to compensate and ensure a strong bond between the original hull and the repair. The boat certainly could have been repaired with polyester or vinylester resin and perhaps it wouldn't make any difference. For that matter, I could have used the same (weaker) chopped strand matt that the hull was built with instead of (stronger) fiberglass cloth. However, I know how this boat will be used/abused and figured it was prudent to use stronger materials. Considering the small quantities of products used, the difference in cost was probably just a few cents.You're correct that polyester resin cures faster than the slow setting marine epoxy we used (West Systems with slow hardener). Considering that all the epoxy work was done in one step late in the day and allowed to cure overnight, it didn't really add any time to the repair. But if you're in a time critical situation, polyester resin or a faster setting epoxy certainly would save time. Using fast hardener with the same epoxy we used would have cut the cure time down to about the same as polyester resin.You're also correct that gelcoat is a polyester product. One advantage of using all polyester products or vinylester/polyester is that you get a better bond between the gelcoat and the repair, since they bond chemically as well as mechanically. I assume that's what you were getting at with your question? The rule of thumb is that epoxy bonds very well to cured polyester, but polyester doesn't bond as well to cured epoxy. Still, I haven't found this to be a problem with any of the kayak repairs I've done with epoxy and gelcoat. The gelcoat seems to bond well enough to serve it's intended function as a cosmetic/abrasion layer. I suspect that the caveat is more relevent to larger boats with heavier applications of gelcoat than is common on kayaks. I've found this to be true with much of the commonly found information on fiberglass repairs. Our little boats with their thin skins require some adaptation of techniques and materials, though the basics remain the same. Quote Link to comment Share on other sites More sharing options...
Walter Posted September 10, 2004 Share Posted September 10, 2004 Thanks Brian, the pictures were great.I just had a couple of questions.What size Fiberglass mat did you use?Was there any problem taking off the milk jug form at the end? I assume you left it there until everything was cured?Did you put a patch on the inside also or was that not necessary?ThanksWalterImpex SerenityOrange/White Quote Link to comment Share on other sites More sharing options...
scamlin Posted September 10, 2004 Share Posted September 10, 2004 I believe Brian used a 12 oz. cloth. (The cloth and many other supplies and tools were generously contributed by Michael Brokenshire as neither Brian or I had brought anything). I was amazed how well five layers of this relatively heavy cloth fit in the feathered hole Brian created. To be clear: one layer with resin was applied first from the inside overlapping the edges and supported by the milk jug plastic and a foam seat. There were five layers applied from the outside onto the inner layer and the feathered edges of the hole, each patch slightly smaller than the previous (see photos). Brian kept mumbling he had room for one or two more patches and could have saved some of the buildup of gelcoat later on. The trick is to build up the fiberglass/resin matrix to near but still below the eventual surface of the gelcoat. If it's too high, no big deal as you can sand the fiberglass/resin down as needed. Too low, and you just need more layers of gelcoat. To me, the key to a successful, strong, even beautiful patch was the form provided by the plastic cut from the milk carton and supported by a blow up foam seat wedged beside the seat. It maintained the contour of the chine and gave a solid base for the cloth layers as they were laid down.The milk jug plastic released easily: it did not stick. Only if you get some resin oozing around and on top of the plastic would it stick slightly, but without glass, resin doesn't have much strength. We only had to sand down some minor ridges around the edge (sparing use of resin helped).Very slick repair by Dr. Nystrom. I learned a lot by watching: fundmental principles (e.g. good support for the patch to maintain the contour), knowledge (e.g. how much hardner to add), experience (e.g. what the gelcoat does when it 'kicks') and improvisation (e.g. create 'forms' out of packing tape to build up gelcoat on the keel).I want to publically thank Brian for the repair, but more importantly for taking me to school.ScottSurgical Assistant and Photographer Quote Link to comment Share on other sites More sharing options...
Guest guest Posted September 10, 2004 Share Posted September 10, 2004 Brian,thanks, I saw another expert repair job the other day and he also used epoxy..just wondering why you both did that...I mostly avoid situations that may hole the boat simply because I don't want to fool with patching...but soon it may happen. Quote Link to comment Share on other sites More sharing options...
Brian Nystrom Posted September 11, 2004 Author Share Posted September 11, 2004 I don't claim to be an "expert" at kayak repair, but merely competent. The method I use is a combination of a things I've read and a bit of improvisation. If there were differences in the method you watched, I'd be very interested to know what they are. I'm still learning this stuff. Quote Link to comment Share on other sites More sharing options...
alan Posted September 14, 2004 Share Posted September 14, 2004 Thanks Brian. I'd definitly like to apply a keep strip, too. Maybe we could make a workshop out of it. Though I need to fix the several gelcoat dings i got from my last trip first (all along the keel!). One of them has compromised the kevlar layer, and i will probably need to repair it. However, given the difficulties in cutting and sanding kevlar, is there any objection to repairing a kevlar boat with fiberglass? From my (very) limited understanding, it is the resin that bonds, making me think that it is not dependent on the fabric. Though i'm not sure how holing the boat would go when trying to feather kevlar.AlanCD Andromeda - red on whiteDagger Id 6.9 - blue/black Quote Link to comment Share on other sites More sharing options...
Brian Nystrom Posted September 15, 2004 Author Share Posted September 15, 2004 A keel strip workshop is certainly a possibility, though I'd want to try the procedure on one of my own boats first. I'd still like to do a workshop on fiberglass repairs and have figured out how to do it in a reasonable time span, but it will require a lot of preparation.As for repairing your boat, the procedure will depend on the nature of the damage. If the Kevlar layer is merely abraded, covering it with additional Kevlar or fiberglass is all that's necessary. If the Kevlar is fractured, crushed and/or delaminating, the damaged fabric must be removed, just as with a fiberglass repair. That will involve cutting and scraping to feather the area, which really isn't too much more of a hassle than sanding fiberglass. Quote Link to comment Share on other sites More sharing options...
alan Posted September 16, 2004 Share Posted September 16, 2004 Thanks, Brian. I appreciate your feedback.The kevlar is crushed a bit, so i guess it will be a more involved fix. Thanks, again.AlanCD Andromeda - red on whiteDagger Id 6.9 - blue/black Quote Link to comment Share on other sites More sharing options...
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