Can I glass over car bondo? MFG Challenger

[garth123]

I was given a boat, it is an old MFg Challenger...
It has car bondo on the main keel. Is it ok for me to glass over that hardened bondo.

 

[rockyrude]

Re: Can I glass over car bondo? MFG Challenger

The car bondo was the wrong product from the get go. I'm sure it is still holding some moisture. I'd dig it all out , if the repair area is large use something like "peanut butter" ( see resto section) to repair before reglassing the area.

 

[Woodonglass]

Re: Can I glass over car bondo? MFG Challenger

Welcome to iBoats!

A Close Up of the area in question would really help us to help you. Rocky is correct that Bondo is NOT a good choice especially for Below the Waterline repairs

 

[MTboatguy]

Re: Can I glass over car bondo? MFG Challenger

You need to dig the bondo out, it is not water proof as will drawn and hold water, which will cause anything put over it, to swell and pop and crack the overcoat, there are specific products made that will do the job, just search around here for a while and you will be on the right track.

 

[Yacht Dr.]

Re: Can I glass over car bondo? MFG Challenger

View attachment 98096Is it ok for me to glass over that hardened bondo.

Yup.. Glass over that Bondo.. as long as your glass and prep is done correctly ..

Your using the bondo instead of Foam I presume.. for shape right ?

You can use whatever you want prior to Glassing .. just as long as your prep and glass is done correctly .. .

YD.

 

[MTboatguy]

Re: Can I glass over car bondo? MFG Challenger

Well either I did it wrong a few years ago, or the bondo that had been exposed to the elements had absorbed water, because it popped and cracked the fiberglass overcoat, I have also seen it do this on motorhomes and cars.., if the Dr. is correct, then I would dig any bondo out that had been sitting in the elements for a while and redo it. You don't know if the previous person did it correctly.

 

[Yacht Dr.]

Re: Can I glass over car bondo? MFG Challenger

I am only presuming that the Bondo is a shape/form for the glass...Bondo or PB is not any kind of structural form.

Kinda like Center Boards being formed with Pig lead into a mold and filled with some kind of sloth putty to make shape..then a few layers of glass.

Or reverse shape and glass..It does not matter at this point ..unless the bondo was used through and through.

In which case Yes you would glass the inside ..

YD.

PS. Mebbe a case of not enough info here ?

 

[MTboatguy]

Re: Can I glass over car bondo? MFG Challenger

I think it is a case of not enough info, I always approach a repair that someone else did, with a strong suspect feeling, if I do it, I know it has been done correctly, if I don't, then I redo it, I have in the last 50+ years been burned to many times at the wrong time!

 

[garth123]

Re: Can I glass over car bondo? MFG Challenger

Here are some pictures of the bondo from the last guy...
I will chip it out. What would be the best filler or shound I take it down completely?
Garth

 

[ondarvr]

Re: Can I glass over car bondo? MFG Challenger

It depends on how the Bondo is used, plus how the boat is used as to whether Bondo will hold up.

As a fairing compound on a hull that is never put in the water....it may hold up well, soak it in the water much and the chance of failure climbs rapidly.

As a filler to fill a void that will have glass over it.....it depends on how thick the glass is and whether any of the Bondo is feathered out onto the surrounding surface.

If you were just using it as a shape to glass over, like reshaping a keel that had worn through and it wasn't going to be part of the new resin to hull surface bond, then it isn't going to be much of an issue. If there is Bondo between the new layup and the hull (like what is shown in one of the pics above), then it will fail rather quickly if it's left in the water. In one pic it appears to show a large section of some kind of filler has fallen off, this is typical for a Bondo type product.

 

[Yacht Dr.]

Re: Can I glass over car bondo? MFG Challenger

Oh .. um.. Thats not just not bondo/filler on your main keel .. like some nerfing was patched up on the stem with filler thing..

Looks like someone did some Serious Troweling with putty on a good part of the whole keel that is failing.

I would scrape/grind off that stuff and glass it ( dont use putty unless its for sub-shaping ONLY ).

Coulda used them close-ups earlier .

YD.