Freebee
Well-known member
Can I use car body filler to patch up the scars on a grp hull??
Car body filler
- Thread starter Freebee
- Start date
DownWest
Well-known member
Not a good idea, as is not waterproof. Use white gelcoat filler.
Body filler is polyester resin mixed with talcum powder and I have seen air escaping through it under pressure.
Body filler is polyester resin mixed with talcum powder and I have seen air escaping through it under pressure.
ripvan1
New member
use the stuff with fibreglass strands in it - it comes in flexible packs - cars get wet too.
PaulRainbow
Well-known member
More detail of the scars is required. How wide ? How deep etc ?
PaulRainbow
Well-known member
It's good stuff in the right places, but they would have to be some very serious scars.
Ardenfour
Active member
I used standard polyester filler (cataloy / P38) as a finishing coat on top of epoxy when I carried out major structural work to the mast step and beam on my last boat. Easy to sand to shape, and no evidence of cracking or detaching from the substrate after a couple of years of frequent and sometimes hard sailing. Op should be fine using it above the waterline. He doesn't say where the gouges are...
cmedsailor
Well-known member
Is a car body filler the same thing as a fiberglass filler? I have used the latest to repair/fill a hole near a stanchion base and because it's grey colour I added some white gelcoat filler on top of it. Both are very easy products to use.
Freebee
Well-known member
I have quite a few screwholes to fill where the rubbing strake has been removed although a strake is getting refitted I will drill new fixing holes and some small chunks out of the bow above water line and one long scar through the gel coat its above the water line but I can see the fibre substrate in places on this one. should I just fill and fair this???
fredrussell
Well-known member
Yep. That's why cars that have filler on can never go in the rain ever again!
AntarcticPilot
Well-known member
I think that the issue is that car filler is permeable; gel-coat filler (which comes in handy tubes!) is not.
cmedsailor
Well-known member
If your boat is white I will suggest to use gel coat filler. Strong enough for what you want to do and no need to paint it white.
PaulRainbow
Well-known member
For screw holes, drill them out a little bigger and slightly bevel the edge hole (from both sides if possible). Stick a piece of tape over the outside of the hole, pressing it into the hole a little, and fill from the inside. When dry, remove the tape and fill the slight depression with gelcoat. If no access to the back side of the holes, fill from the front, remove a little with a drill when dry and fill with gelcoat. For small holes just drill, bevel and fill with gelcoat.
Clean and abrade the long scar and fill with gelcoat. This may require several coats in the deeper places, sanding flat between coats.
Depending on the depth of the chunks in the bow, either fill with gelcoat, same as the scar, or grind out slightly fill with epoxy filler or gelcoat filler and finish with gelcoat again.
Any gelcoat repairs should have a final sanding with 1000 grit wet and be polished with a fine compound, such as 3M Finnesse It.
I'd use epoxy filler, rather than car body filler for these jobs.
PowerSlapper
New member
You could but not recommended
Irrevelant. Car body filler is not suitable.
Use fibreglass filler (or microfibres in Epoxy resin) for the holes topped off with gelcoat filler. and gelcoat filler only for the "scar".
The car body filler is protected for a period of time by the paint applier after the repair however the filler on its own is NOT waterproof and is of inferior strength to fibreglass filler.
Finally, a sensible answer.
DownWest
Well-known member
Most people with a bit of pride tend to paint over the filler on cars... which might just make it a bit more waterproof..
On a boat, unless it is already painted, it would be difficult to match the gelcoat. YMMD
Ah, missed Jules reply.
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PaulRainbow
Well-known member
Seriously ? :beaten:
Do you see anywhere that i recommended using car body filler ? My question was perfectly relevant, as any advice is dependent upon what damage the OP is intending to repair.
I note that in your reply you recommend different methods of repair for the different types of damage. How would you have tailored your advice without knowing what the damage was ?
There is nothing here that requires the use of "fibreglass filler", it is totally unsuitable for scrapes and small screw holes.
Oh, and whilst you were considering that asking what the actual damage consisted of was irrelevant, you also forgot to ask what type of car filler he was planning to use. Because, some car fillers are waterproof and work extremely well for certain types of repair.
Freebee
Well-known member
Forgot to saying I'm painting the hull on completion of filling probably with 2 pack
PaulRainbow
Well-known member
Grrrrrrrrr
In that case :
For screw holes, drill them out a little bigger and slightly bevel the edge hole (from both sides if possible). Stick a piece of tape over the outside of the hole and fill from the inside. If no access to the back side of the holes, fill from the front.
Clean and abrade the long scar and fill, same with the bits at the bow.
It may require more than one coat in the deeper places, sanding flat between coats. Use epoxy filler.
lenten
Active member
worked for a garage owner painting 2 ex rnli watson life boats---we used car body filler ---it worked well---the owner wanted a high standard---on the 52 footer we had a problem with primer staining the boot topping---it took 9 coats and 36 hours before he was happy-----he then bought an ex admiralty mfv and tried to make a silk purse out of a sows ear ----i worked on it alone-----when i finished owner said he had added up all 7 lb cans of filler-- and i had used 1/2 hundred weight (25 kilos) ---used to get the port hamble painters round to check this "new" filler-------there might be better ways of doing things nowdays but i wouldn t completely rule out carbody filler
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