Bondo

[Pavel24]

Hello,

I need to do same cosmetic job on the hull above water line and i need a filler .

From what i read some people recommend following products :

Evercote Formula 27
Marine-tex

But every one speak poorly of Bondo , from what i understand they say it contain some ingredient that absorbs moisture and cant be used on boats( if i am not mistake they speak of the car body filler)

What about the all-purpose one ? on the package it says that it is water resistant ant it is polyester resin that will work with gelcote

https://www.3m.com/3M/en_US/company-...3786499&rt=rud

Any one have experience with it ?

I ask because it is easily available near me.

[model 10]

That link was just a resin? You want a better resin and some sort of filler. Not micro bubbles either, they fill with water. Just order the proper filler from somewhere. Or make your own from the proper stuff.

[Chotu]

What are you filling exactly? How deep? How long? What's the material you're fixing? What will go over the bondo or other filler?

[Pavel24]

in high winds the aft portion of the boat rubbed against the docks and a part of gelcote broke off , the fiberglass is in good condition (the fiber glass is more rounder , i guess it the reason why the tip broke off ).

I want to use filler to mold small point and then put gelcote over it

From what i read , its possible to use polyester resin with different fillers ( ex: west marine epoxy fillers or other materials) but most probably i will just order the right filler like formula 27

PS in photo its not my boat , but another columbia 9.6

[Chotu]

Epoxy with colloidal silica and microbaloons will stay better but you can certainly use Bondo for this without any real worry. It will be a lot easier to paint the whole transom than to try to match and apply a tiny patch of gel coat , however.


I think you'll get a lot of people saying never use Bondo on a boat, but it's just a polyester filler and you are shaping something above the waterline with it so it's going to be ok. Just seal it off well with the protective coating (ie paint, gel coat).

[Franziska]

That area is exposed to water, ideally use a two component epoxy filler to built up the missing piece, sand it to shape once cured & paint.
If your damage is bigger you should even mix in some glass microfiber.

If it's only scratches, use a polyester topcoat.

Check from inside if there is not more substantial damage.

Btw. real microballons which are used for making a putty from resin are made of glass and do not absorb water.
They are fine to be used on boats.

Bondo, or similar products, are typically thickened with chalk and similar materials and absorb water. Not good for building up substance. You can use them to fill very small (=thin, not requiring built up) scratches when finishing, but these areas need than proper protection by paint or epoxy coating.

[Pavel24]

i have epoxy with fillers but i know that gelcote dont go well with epoxy and i dont want to use another paint.

I have read on another forum that they had success with polyester resin with 407 filler from west systems . And after that i was thinking putting gelcote over it

[jimbunyard]

You can use it above the waterline, but some 'Bondos' have less than 'quality' ingredients, leading them to have adhesion and other issues.

Blew your picture up 500 percent and can't see the broken point. Is this a 'before' picture?

If not, I'd just sand the broken point smooth and try and match the gelcoat without adding anything at all in regard to rebuilding the point, because it's likely just to get knocked off again (though epoxy sticks better than polyester).

Or you can make your own polyester 'bondo' with some high quality laminating resin, some fumed colloidal silica and glass beads...

[Pavel24]

Originally Posted by jimbunyard

You can use it above the waterline, but some 'Bondos' have less than 'quality' ingredients, leading them to have adhesion and other issues.

Blew your picture up 500 percent and can't see the broken point. Is this a 'before' picture?

If not, I'd just sand the broken point smooth and try and match the gelcoat without adding anything at all in regard to rebuilding the point, because it's likely just to get knocked off again (though epoxy sticks better than polyester).

Or you can make your own polyester 'bondo' with some high quality laminating resin, some fumed colloidal silica and glass beads...

In the photo is another Columbia 9.6 ,i posted it just for reference.

the more i think, the more i want to just make it flat , like you say. With fiberglass being more round and not going to the tip , the point have high chance of being broken again in the future.

Finally i purchase 3m marine filler to do the job.

https://www.3mcanada.ca/3M/en_CA/com...4529206&rt=rud

[Fore and Aft]

Just use this gelcoat repair putty. Its white so it should be close to your hull colour.
https://www.boatingandrv.com.au/gelcoat-repair-putty/
Cheers