I'm in the middle of "reattaching" one edge of the cockpit coaming on my Eddyline Wind Dancer. The coaming separated from the deck over a period of a year or so, with the failure occurring where the polyester resin (?)/phenolic microballoon (?) putty joined the underside of the deck. (Coaming seems solidly attached to the putty material.) I had this same problem with another WD I owned 6 years ago, whose coaming was attached with a Cabosil-polyester resin putty (I think). This also failed at the putty/deck interface. Considering the stresses I have applied to the coaming/deck joint, I'm not upset about the failure. It's not too bad a job, though the fiberglass itch nails me for a week or so on projects like this, and it's tough to get to all the surfaces which need sanding/grinding. I am curious, though, why Eddyline chose a putty which was NOT epoxy-based, and why there was no chopped glass in the mix to improve its strength. I'd think both of these would improve the durability of the joint. Anybody else know what adhesive/filler combo is used to keep the coaming/deck joint intact on their FG yak? Anybody else experience failure of this joint? I'm finding that sanding/grinding a little ways into the deck material seems to be necessary to get a good "tooth" for the repair. When I did this five/six years ago, I used polyester resin and a couple layers of mat to reinforce the seam, and that seemed to be pretty strong. (Did not know epoxy was better, then.) To prevent a reoccurrence, I'm going to make sure the tangs which extend down from the coaming are supported by the hull. I think the separation started when there was a little gap between the end of the tang and the hull inner surface, so when I used the coaming rim to lift myself out of the yak, I over-stressed the coaming/deck joint. Finally got so bad a couple weeks ago, there was a FLOOD of water entering the cockpit when I did leaned turns on that side! That's what initiated the repair. -- Dave Kruger Astoria, OR *************************************************************************** PaddleWise Paddling Mailing List Submissions: paddlewise_at_lists.intelenet.net Subscriptions: paddlewise-request_at_lists.intelenet.net Website: http://www.gasp-seakayak.net/paddlewise/ ***************************************************************************
Dave wrote; -(SNIP) >Considering the stresses I have applied to the coaming/deck joint, I'm >not upset about the failure. It's not too bad a job, though the >fiberglass itch nails me for a week or so on projects like this, and >it's tough to get to all the surfaces which need sanding/grinding. > >I am curious, though, why Eddyline chose a putty which was NOT >epoxy-based, and why there was no chopped glass in the mix to improve >its strength. I'd think both of these would improve the durability of >the joint. There may be chopped glass in the mix although the fiber length may be short so they are not easily discerned. Also, polyester adhesive mixes are not unusual and do hold up quite well when the resin used is flexible enough for the job. With time polyesters do get more rigid and maybe the resin Eddyline used was not as flexible as it could have been. Production demands often eliminate epoxy as a practical adhesive. > >Anybody else know what adhesive/filler combo is used to keep the >coaming/deck joint intact on their FG yak? Since kayaks are rather flexible the coaming joint can be the stiffest part of the deck. This invites failure so the best adhesive is one that has enough elongation to accomodate the flex of the deck. Sikaflex 292 is a good flexible adhesive for polyester joints. I would rate it better than epoxy since it allows movement. There are other similar adhesives but those I am familiar with are industrial materials and not readily available. (SNIP) >I'm finding that sanding/grinding a little ways into the deck material >seems to be necessary to get a good "tooth" for the repair. When I did >this five/six years ago, I used polyester resin and a couple layers of >mat to reinforce the seam, and that seemed to be pretty strong. (Did >not know epoxy was better, then.) You would need a good "tooth" for the epoxy too and you should be sure all the brittle filler is removed or the joint will fail again at the epoxy/polyester filler interface. >To prevent a reoccurrence, I'm going to make sure the tangs which extend >down from the coaming are supported by the hull. I think the separation >started when there was a little gap between the end of the tang and the >hull inner surface, so when I used the coaming rim to lift myself out of >the yak, I over-stressed the coaming/deck joint. Finally got so bad a >couple weeks ago, there was a FLOOD of water entering the cockpit when I >did leaned turns on that side! That's what initiated the repair. The flooding is a bummer. Be cautious with the support to the hull. You may cause a hard spot that could cause a hull failure. Sea kayak hulls and decks tend to thin and joints should give a bit and not cause "Hard" spots. Cheers, John Winters Redwing Designs Specialists in Human Powered Watercraft http://home.ican.net/~735769/ *************************************************************************** PaddleWise Paddling Mailing List Submissions: paddlewise_at_lists.intelenet.net Subscriptions: paddlewise-request_at_lists.intelenet.net Website: http://www.gasp-seakayak.net/paddlewise/ ***************************************************************************
John Winters wrote: > There may be chopped glass in the mix although the fiber length may be > short so they are not easily discerned. Also, polyester adhesive mixes are > not unusual and do hold up quite well when the resin used is flexible > enough for the job. With time polyesters do get more rigid and maybe the > resin Eddyline used was not as flexible as it could have been. Production > demands often eliminate epoxy as a practical adhesive. I think you nailed it here, John. This stuff is hard as a rock, and the fillet is very thick in places -- giving essentially no flex. BTW, the technician I spoke to at Eddyline recommended epoxy/glass as a fix -- could be they now use that. When I was up there a year ago, looked like they were using a Cabosil/polyester mix, but they may have switched, since. > Since kayaks are rather flexible the coaming joint can be the stiffest part > of the deck. This invites failure so the best adhesive is one that has > enough elongation to accomodate the flex of the deck. Sikaflex 292 is a > good flexible adhesive for polyester joints. I would rate it better than > epoxy since it allows movement. There are other similar adhesives but those > I am familiar with are industrial materials and not readily available. [snip] Gotcha. I'd use Sikaflex if I had the energy/time to remove the whole coaming insert. The failed segment is only 18 inches long along one side, so I think I'll go with something having compliance comparable to the rest of the joint. > You would need a good "tooth" for the epoxy too and you should be sure all > the brittle filler is removed or the joint will fail again at the > epoxy/polyester filler interface. [snip] Good advice. > The flooding is a bummer. Be cautious with the support to the hull. You may > cause a hard spot that could cause a hull failure. Sea kayak hulls and > decks tend to thin and joints should give a bit and not cause "Hard" spots. Yeah, aware of that. The failure of the coaming joint is really my fault. I removed the stock seat (integral with the coaming) and "extended" each tang with a screwed-on flange of polycarbonate sheet, leaving a quarter-inch gap, which I filled with a sandwich of hard black rubber and softer foam. I'd have been OK with this arrangement, but somehow my sandwich got flushed out on one side, and the lack of support on that side allowed my 100 kilos to delam it on exit. (I usually lift myself out using the cockpit rim.) I'll make sure the sandwich does not leave this time! I much appreciate your very professional and highly knowledgeable advice, John. Your expertise, alone, makes PW a terrific resource! Thanks for the response. -- Dave Kruger Astoria, OR sea kayaker -- and chemist *************************************************************************** PaddleWise Paddling Mailing List Submissions: paddlewise_at_lists.intelenet.net Subscriptions: paddlewise-request_at_lists.intelenet.net Website: http://www.gasp-seakayak.net/paddlewise/ ***************************************************************************
This archive was generated by hypermail 2.4.0 : Thu Aug 21 2025 - 16:32:50 PDT