Epoxy or Automotive Bondo??

[jimhales]

Hi;
I have a small runabout that has stress cracks in the gel coat. They are hair line in thickness but go to the depth of the fibreglass. I have ground them out making the hairline cracks much more exagerated and down to the fibreglass.
What I am wondering is, Can I use automotive body bondo to fill, then use a glazing putty over top to finish or, do I have to go with the Epoxy resin? What would be the pros and cons?
I will be recoating the boat with interlux topcoat.
Thanks in advance.

[Geoh]

I used a product called Marine-tex White for that problem yesterday except i had some larger areas to fill ...Recommended by the western marine guy. patched some scraches in the hull also....really looks like it works. says its a heavy duty structural apoxy.
Geoh

[fiberglass jack]

bondo got no flex, and you need flex with a boat so no bondo and the **** soaks up water and you will get blisters, go with epoxy say sikiens it will hold up better, the problem may be in the glass and by filling the cracks may only band-aid, good chance they will come back in a year or two. to do the job right you will want to grind away all the gelcoat and some glass , put in some new glass and then sand it down and prep it for paint

[jimhales]

Thanks to both responses, Geeeezzzzz,,,I'm greatfull for this site. It has saved me countless hours of research, trial and error!!.
Jim

[VKRUE]

Jim:
The question I'd be conserned with most at this point is... Why does the boat have STRESS cracks in the first place...

The word stress means exactly that... STRESS... and anything that is stressed, is so for a reason.

An old friend of mine (the guy that sold me my boat) once had a 21' open bow that he took to the marine doctor to have something fixed. After looking the boat over, the guy told my friend that he refused to make the repairs as asked. When asked why, the guy pointed out the stress cracks and told my friend that the boat would soon crack up (probably in half) and that the repairs he was asked to make would not only be in vain but, actually cover up an existing problem that could be dangerous to anybody in the boat. My friend listened to his advice and scraped the boat... and asked me to help cut it up.

I learned a lot about a fiberglass boat that day.
What I saw while cutting this tub up into small pieces to haul off to the dump was amazing. This boats keel was a plain ol' 2"x14" (approx.) piece of wood totally encapsilated in fiberglass... the wood was completely rotted... gone... practically powder in places.

The stringers were the same way. If he would have (spiced up) that old gelcoat and put it out on the water with friends & family aboard they would have all been swimming for shore at some point, if not injured or worse.

That boat might possibly have been able to be saved had my buddy been willing to put the time and effort into the proper repairs but, he was not. I think that the replacement of the keel and stringers would have done it... but, what do I know about boats... I'm a truck driver.

This is not to say that your boat is in the same condition... nor am I trying to discourage you. Just simply pointing out that you should ask yourself why are the stress cracks there in the first place. If you can't answer that question yourself... accurately... then you might want to have someone that knows more about fiberglass boats than you take a look at it.

[jimhales]

Thanks VKRUE;
The stress cracks are from poor design I am sure. They only appear on the upper portion of the two piece hull where curves are and where tie cleats were placed. I have gutted the entire boat to find the hull is in good condition. Stringers need replacing as well as the trasnsom. The transom has a couple soft spots and I am not prepared to let her on the water wondering if I should have. I am enjoying the rebuild as it keeps me out of my wifes hair.
Thanks again.

[alan white]

I did the same job two years ago, Jim. I srore the boat here for the customer, so I see it as the job ages. I used epoxy after grinding out the cracks. I also noted the probable causes as I doctored up that 30 yr old boat.
Many were a result of the gelcoat being too heavy in certain places, some from impact, and none appeared to be from structural problems, but as VKRUE mentioned, structural problems dont go away, and so it's best to analyze each area that's crazed or cracked.
So far, no evidence shows that would indicate the epoxy had let go, and frankly, I wouldn't have considered using anything else, considering the small amount required.
As you've further described the cracks above, this may be due to heavy gelcoating combined with flexing. You can probably see what might have cause flexing. Maybe a bit of stiffening inside is in order.
Good kuck.

Alan