Resin/repair problem

I’ve run into a problem with a repair. I made this board a few months ago. I originally made a mistake placing the fin boxes. I put the rear of the fin box where I wanted the rear of the fin to be, the result being that the boxes were too far back. so I decided to make it into a quad to see how that would go.

I installed the boxes, and glassed them in. During the process my dog ran into the stand and knocked my board onto the garage floor. so I also had a nice ding on the tail to fix and some spots along the rail where the weave showed but didn’t look like it went through. I sanded lightly before applying the resin for the repair.

Anyway, When I went to sand the resin wasn’t sticking. I’ve never had this problem. I had painted a little where the tail repair so I thought it might just be not sticking on the paint, but no it didn’t stick on the other side either, or on the rails. I’ve made repairs before and haven’t had a problem. I’m using RR epoxy over EPS. It is not a new batch. My garage was slightly cold, around 65 degrees, but I glassed an entire board a month ago in the same temp, same RR batch, with no issues.

I ground all the resin/cloth down that want stick and I am considering starting over, or putting the board away for a while since I am frustrated. I would love some help.


1 - any idea what went wrong and how I make sure it doesn’t happen again?
2 - Do you think the spots on the rails need to be repaired? I don’t think it went through, but the weave is showing (why is that?)

If I have left out any needed information let me know.

Thanks - Jeff

Problems with resin not bonding are usually related to surface prep before applying fresh resin.

The weave is showing because you sanded into it. There is no other explanation for it.
Your resin isn’t sticking because there is contamination of some sort. A properly sanded repair should not have adhesion issues.
Was the sandpaper new, or dirty? Did you wipe the area with a dirty rag after sanding it?

nothing different, but I will use new paper/rag next time. As far as my weave question - I know it is showing around the fins because I sanded into it, I did that to get it all off before another repair. I was asking about the bottom pic with the weave showing on the rail. that is exactly how it looked after it hit the garage floor. Does it need to be repaired?

Data point: I had some old RR resin that had gone through a lot of heat in my garage over the summer. I did a hot coat with it and it later came off in large sheets. I am a competent laminator. Smug about it in fact. I wrote it off to old resin and threw the stuff away. Hasn’t happened since.

I’ve had the exact same thing happen on a couple of my boards. I’m a newbie with only 4 boards under my belt, so bear that in mind. However, I’m fairly certain that the weave showing there is due to a not-so-tight wrap on the rail. At least on my boards, it seems like my wrap wasn’t as tight as it could have been, and after flexing a little the weave ever so slightly separates from the fill coat. I’ve had the same issue once on the rail, and once on the deck apex at the beginning of a down rail. I can 100% confirm that neither case was there any sand through. That was my first thought as well and after doing a fill coat patch it was still clearly visible. Haven’t had any water intrusion that I can see in my case, but that’s not to say it shouldn’t be repaired. Using RR epoxy on EPS.

Again to reiterate, I’m no pro. I’ve learned the small amount I know from trial and error and the folks here on Sways. These are just my thoughts in analyzing my own observations. I could be completely wrong, and I’m following this closely now to see if anyone chimes in.

What grit sandpaper did you use to prepare the area around the ding with?

How much resin did you use to glass it? I’ve used too much resin before and had cloth ‘float’ up to the top, away from the underlying glass layer, and then cure. Once it does that, when you sand, the weave can appear. At that point, you either need to sand flat and reglass with more cloth or say screw it (don’t do that). Or it could be you contaminated the underlying layer somehow (done that). Or, maybe you didn’t presand enough so there wasn’t a physical bond with the new resin/cloth.

not sure what grit i used. I’ve never had a problem before and I think I was getting complacent. I sanded with 80 grit, cleaned the surface and put on another layer yesterday. I’ll try sanding it in a few days and see it it sticks this time. Thanks for the help.

I sanded, cleaned and tried again. It came out fine. I still have no idea what happened, but my guess is I sanded one day and left it a day or two then did the repair. There must have been dust or something else on the board. I sometimes do a little each day before or after work, so I will have to pay closer attention to that. Thanks