# how is bondo for boats?



## TSOJOURNER (Dec 16, 1999)

hey all 
i have some superficial dings on my fiberglass hull and was wondering if bondo would work as fill? i have auto body history and not much in the marine end yet i think itll be ok because their both fiberglass just want to check first 
cheers


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## sailingdog (Mar 19, 2006)

I wouldn't recommend it. Bondo isn't really meant for use in a marine environment. It would be better to repair the dings with something like MarineTex two-part epoxy instead, and then gelcoat over it.


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## TSOJOURNER (Dec 16, 1999)

When you try to sand the Bondo smooth you will have a problem. The Bondo is much denser than the gelcoat - harder. You will end up sanding away the gelcoat and the Bondo will still be there. There is a "bondo" for boats - I think that it may be called Marine Tex - but ask around on this forum. Lots of people can suggest various things that they have had success with. The best thing to do is to get a gel-coat repair kit. They are easy to find, and made specifically for that purpose.


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## Sabreman (Sep 23, 2006)

Bondo is polyester resin with a low density filler. It's extremely porous, will absorb water, and will probably not hold (at least it never did for me). Use an epoxy with a filler (I like West System collodial silca fillr) and it will stay put forever. Use a sanding pad on a random orbit sander and you won't have to worry about densities of the surrounding material. A tip - don't try to save $ on sand paper. Start with a coarse (80-100 grit), then medium, then fine paper. Most people create ripples by trying to use only one paper and sand and sand and sand. which will cause ripples to form. A word of caution - if you're trying to match gelcoat, it will be nearly impossible without a manufacturer's gelcoat repair kit. If you don't have the exact color, you can experiment with color mixing before adding hardner but only use coloring agents listed for the resin - other agents may contaminate the mix and it won't cure properly.

Good luck!


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## TSOJOURNER (Dec 16, 1999)

I saberman good choice , and makes for a fine repair


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## TSOJOURNER (Dec 16, 1999)

be very carefull with the #80 grit CR.


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## TSOJOURNER (Dec 16, 1999)

*thanks*

thank you all for taking the time to read my post and thanks for the advice


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## hellosailor (Apr 11, 2006)

Rick-
Genuine Bondo? No way. As Sabreman notes, it absorbs water and it is infamous for failing when used on boats.
If they are small dings and not many of them, I'd also recommend MarineTex. Any comparable product will be just as expensive. If you need more than what you'd get in a box of MarineTex...stick to marine epoxy with appropriate thickeners. West Systems makes a whole line of them--and they'll give you free pre-sales support by phone or email if you call them. 
If you have auto body experience you'll know the materials are the cheapest part of a good repair.<G>


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## Sabreman (Sep 23, 2006)

Concur with hellosailor. West & MarineTex are great. Regarding the 80 grit - yes, be CAREFUL and go lightly and quickly; just touch the paper to the repair. Be patient and use a random orbit palm sander. Maybe even switch to 100 grit depending on where you're working. 

I once worked in a repair yard and rebuilt the corner of a transome that was destroyed on a piling. I rebuilt the corner, but when I was sanding the final coats, I used too fine a paper and couldn't get it the ripples out. My boss finally came by with a belt sander and 100 grit and flattened it in 5 mins. He then went to finer orbital papers to remove the scratches. We awlgripped the whole thing afterward since it's so hard to match gelcoat. Bottom line - in general, flatten with coarse grits, remove scratches with finer grits.


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