I offered to try and fix a collegues brand new board which had collided with a long board. The sidefin boxes were badly damaged. On routing slowly down into the damaged area I found that the core is EPS with no high density foam around the boxes.
Surely this is pretty shoddy? You can see the resin around the boxes and it has made a good bond with the foam, but the foam is really soft. Any side pressure on the fin would crush the foam, wouldn’t it?
My plan (and here I’d love some advice) is to open up the area almost to the rails. Remove the foam and glue in a high density block, bonding it inside the rails and onto the deck with low exotherm epoxy. Then glass and instal FCS plugs (coz that’s what he wants) in the usual way.
Does that sound OK? Maybe I should incorporate somesort of glass box first then add the foam and then glass?
I’ve read here that glassing over FCS plugs makes them much stronger but how would you set the depth so that once glassed they are right? I could probably work it out but suspect that somebody out there might help me not stuff it up!
I’ll post pictures of the repair as it progresses in case somebody spots an upcomming disaster.
Although I agree with your sentiments, it’s probably not going to impress the owner when I pass your views on! Having said that it’s good to have someone else’s views to back my own.
The bottom’s not flat, convex or concave, it just looks “wobbly”, changing from one area to the next. Very soft when pressed.
Paint job’s OK.
It IS light, but it’s bound to be when they’ve left out some of the inportant bits!
Is it a sandwich board? I’d just fill with EPS, glass over and install FCS as normal (connected to the deck), but make sure there is an extra wide contact with the glass around the hole. I use a small grinding bit in my drill to do this, there is probably 3-4mm where I remove all the foam under the glass around the hole. I’ve installed FCS in soft EPS like this and not had a problem(yet). A high density foam block is better though(but more work). A fin system that install like FCS is bound to be trouble if it’s not connected to the deck (or set in a high density block, but this block has to be connected to something as well or have large area or you get the same problem).
It’s not a sandwich, just epoxy/glass on EPS. Will post more pix as the repair procedes.
Have decided to overdo the whole thing! Instal balsa “box”, put high density foam in the box (all glued in place with thickened low exotherm epoxy), glass it and instal fins. What think the world.
Unfortunately the quality of the construction doesn’t surprise me as I have had a cheap imported(?) board myself. My only suggestion would be to tell the owner to deal with a reputable board manufacturer to begin with. Not that this will help you with your repair but this just doesn’t surprise me. And this sort of board (cheap import?) is supposed to be the end of the surfboard industry as we know it…
You will need to be carefull with the plugs as pop-out eps boards have really shoddy eps in my experience. You will need to reinforce it a bit. I would suggest making slightly oversized cavities for the plugs in the FCS “H” pattern and then using a microsphere filled resin to set the plug, that’s right, don’t fill it in quite yet, just enough to bond the deck of the board and the bottom of the “H” hole to the base of the plug (don’t forget cant and toe in at this stage), any more and you risk overheating epoxy melting the foam. When this has set you can pour in some straight resin in the cavity to top it up… when dry, sand and lam as usual…
The two step filled resin bit is critical to avoid melting foam in these pop-out eps boards.
Great, thanks. Any suggestions how to set the plug at the right height so than when ground back and glassed the thing finishes at the right height for the grubscrews to locate in the fin?
I have just bought some low exotherm epoxy and ultra slow hardener which will hopefully avoid exotherm problems.
I’ll do a test run to see what happens with a solid plug of epoxy in EPS.
Of course when retro fitting a board you may actually have to improvise a bit. If your cavity is oversized you could tape some cardboard over the cavity with a hole for the plug allowing it to rest as shown above. I would advise against a solid plug as exotherm will be an issue for sure… do a test… also a solid plug may be too stiff and shear off the adjoining materials in due course. Try to stick to the H pattern, if necessary, shape some foam offcuts to sit as the lower half of the H.
Be sure to tape everyhting down well when you have set your jig to the toe in and cant, you wouldn’t want the plug to “float” about and harden in the wrong position. For EPS it is important to realize that (low density) EPS foam is a weak material and you need to ensure a good bond to the deck glass, otherwise your plug will “wiggle” itself loose.
EDIT:
Having looked at the pictures, your cavities are big, you may want to consider squirting some PU foam into the cavities first and then routing out your proper holes in H pattern… this would be a much better solutions as the PU foam will be stronger and mroe resistant as well as properly bonding to the surrounding materials.
You can see what “low exotherm slow hardener epoxy” does to low grade EPS…
wheras injected PU squirts do this:
Neat cavity filling foam… it’s strong too… Yep, in your friends boards case, I would avoid a “china syndrome meltdown” and squirt some PU in the cavity…