Sanding and polishing fiberglass repairs.

[Terry Chiccino]

Well I finally did it, I was lowering the mast the other day and while lowering I was practicing the art of using the furling line to keep the furler from scratching the deck. I inadvertantly left the hatch cover open while lowering the mast and the "c" flange on the mast where you attach the boom kicker popped a hole right in the curved part of the hatch cover.
I repaired the hole with Marine-tex (that stuff works good!) and now I have to sand off the excess. My question is do I start with 400 grit and go say 600, 800, 1200 and compound from there or has somebody got an easier way?

[Frank C]

Click the button-left for "Featured Articles." Steve K wrote up a piece on fiberglass repairs. I think Steve formerly worked on Corvettes.

[Terry Chiccino]

Thanks Frank , I guess I should spend more time looking around this site there is a wealth of info here. Well off to WM for supplies!

[Jack O'Brien]

Terry:

Skip the elbow grease. Get a couple plastic petunias and stick 'em in the hole.

[Timm Miller]

Start with 320...wet and keep them wet up to 2000. Did it punch a hole all the way through?.....if so you may need some glass to give it some strength........MarieTex works great as long as it has something to grab to...just grabing the sides of the hole.......it may pop out or off over time. The edges of the hole need to be beveled out and glass would used to build it back up.

[Terry Chiccino]

Yep Timm it punched a hole right on through. The exteriorside of the hole is retangular about 1/8" to 3/16" X 1" long. The hole on the inside is conically shaped, the existing fiberglass matting was kind of oval shaped and hanging on still one one side. I cleaned the whole area with acetone which incidently ate right into the interior coating. The interior surface looked kind of dirty but turned white when I wiped it with the acetone. I placed some marine-tex from the inside then jammed the piece of fiberglass mat into it . I then plastered up the inside over the fiberglass mat with the marine-tex.
All said it came out looking pretty good considering my experience with fiberglass repairs. While I was at it I patched a scrape on the side of the boat just below the waterline and the keel scrapes at the bow where the boat rubs on the trailer when loading it. Now it's time for the initial sanding and possible refilling the low spots. I'm going to take your advise and start with 320 grit to remove the high spots because I know I'm going to have to fill the low spots one more time before final sanding.
Damn, there are so many things to watch when raising and lowering that mast seems like my shrouds and stays catch on everything and find every nook and cranny to get into!

[Duane Dunn, Allegro]

For next time, here's a tip when using marinetex.

Before it kicks, but after it has developed some stiffness smooth the area with a wet object. It will not stick to a wet tool. I find I just use my finger dipped in a cup of water. You can smooth the area right down to the level you need and the process of tooling it with a wet finger puts a very smooth finish on the repair. Do it well, and you will not have any sanding required at all. To me this is very important as the marine tex becomes very hard after it dries and it's difficult to sand down the repair without messing up the softer gel coat around it.