Novice question: Using plastic sheet over fiberglass for smoothness when repairing dings?

General Discussion
1

Please excuse my remedial questions, but I’m trying to tackle some repair work on my own.

While I love the satisfaction of seeing fiberglass take form, I’m still getting rough results. 

First, when I make a repair the hardened glass is considerably higher than the q-cell-filled ding (and the rest of the board). I don’t want to sand too much and remove the strength of the glass. Do I just have to live with a slightly raised bump on the board? Or am I not sanding low enough to give space for the fiberglass and resin to fill in?

Second, would it work to put a sheet of plastic over the fiberglass to get a smooth finish, similar to when filling a ding? 

 

Thank you in advance. 

2

I’m not sure what you’re asking, but you can use packing tape to get a smooth result when taping over wet epoxy.

The keys are:

  1. if using the backside (non-sticky side of the tape) that’s the safest method, and the tape won’t stick to the epoxy after it cures, and

  2. if you use the sticky side, you want to wait until the epoxy is completely cured (not less than 8 hrs) to remove the tape.

If you use tape and try to remove it before the epoxy’s cured, the “stick-um” on the tape may cling to the epoxy.

It may be significant what tape you use…

3

I use waxpaper

4

That’s briliant. At what point do you apply it? During the initial application of the fiberglass? Or on the hot-coat layer, after it’s been set?

5

 

Same.

Wax paper and wide (2"), cheapo masking tape to hold it in place. Wax paper is a handy aid when filling dings with a paste mix, too. Whether you use bondo, resin and thickener, what have you. Gets the filler nice and uniform and makes for a lot less sanding. Unless you over-fill, of course. I’ve done quickie repairs in small pukas using just resin and wax paper. Fill the hole, apply paper, let it harden, remove paper,  sand a little, done.

Works for epoxy and poly.

6

Which weight of glass are you using? To prevent a lot of buildup it’s best to use multiple layers of 4 oz than just one layer of heavier glass. The layers should be scaled in size so the edges are not stacked on top of each other. One smaller patch, one bigger. And yes, you should always try to get the area around a ding sanded a bit lower than the original finish.

Well, if you’re using lam resin that is not a good idea, since you have more resin to put on the repair and don’t want to load too much resin in the glass. When you apply a fiberglass patch the weave in the cloth should be very obvious, texture-wise. Same as laminating a board. If the surface is smooth you used too much resin. Plus, putting wax paper on lam resin essentially makes it sanding resin.

7

Look for a plastic bag called polyethylene or PE, it feels different to other plastics and it never sticks to resin. I use it for all small repairs whether its a rail ding or on the flat. Its good for creating the correct curve without getting your fingers sticky and it stops resin from running.

Big garbage bags are usually PE and I use them for vacbagging, you peel it off and the resin is like glass.

8

Staggering the glass is a good way to go. My advice would be forget the plastic and use a brush with your sanding resin. If you do it right and pull your tape at the right time you basically shouldn’t have to sand. Good luck keep experimenting
peace.