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DUCKY 11-03-2005 05:35 AM

Bondo over fiberglass
If I drill holes to pull a dent can I cover the holes first
with fiberglass matt and resin before the bondo?

beemdubya 11-03-2005 06:59 AM

Nah, i would just use duraglass or something first.. then bondo..

cboy 11-03-2005 07:01 AM

I'm not a body/fender guy but I've played with glass and bondo enough to know it never acts quite like you want it to. My thinking on this particular repair is that if you do a good job pulling the dent the surface of the metal is going to come of fairly flat (uniform). Yes, you can put a layer of glass & resin over the pull hole, but when you sand everything down to the level of the rest of the metal, you will have sanded off nearly all of the glass cloth - thereby defeating your purpose and possibly even sanding right through to expose the hole again.

The best fix, obviously, is to weld up the hole and grind it down. The next best (IMHO) is to use the normal shade tree approach, which is to press the bondo into the hole allowing it to ooze through the whole and then expand a bit on the back side making somewhat of a "plug". Again, any fill of a hole of gap with bondo is NOT going to give you the best results. But if you are just doing a quick fix, it will last for a little while.

roger1 11-03-2005 07:01 AM

The right thing to do is to weld those holes up. Niether fiberglass or bondo can completely seal out the moisture.

Get yourself a small mig. Small units work fine but get a name brand like a Miller, Lincoln or Hobart. You will be glad you did.

DUCKY 11-03-2005 07:28 AM

I don't have a welder and I'm concerned about the filler over the hole.
I read somwhere on here that no bondo is waterproof, I'm afraid
of moisture on the back side of a panel, like a door.
I have Dynaglass that claims to be waterproof but some say it really isn't.
Wouldn't fiberglass be more waterproof? I can dimple the holes in to
hold it.

BondoKing 11-03-2005 08:14 AM

Ducky if you are not going to get a welder... do this... get some short hair fiberglass... it has the fiber in it already... Fill your holes... sand down, cover with skim coat of glaze ( 2 part by the way, like Icing)..

Get access to the back of the panel and spray a rubber undercoating on it... Now you are sure you are water proof... I have used fiberglass before and never had any failures with it absorbing water, but there is always the first time for everything :D


crashtech 11-03-2005 08:18 AM

Maybe I will be accused of heresy, but if you just can't or won't weld up the holes, sand the backside of the repair first, then fix the frontside beginning with something like Duraglass or Everglass. Once the repair is complete, return to the backside and sand it again, knocking down the 'worms' that have formed. Apply a coating that will prevent moisture from entering through the holes, primer and paint would be good, or even undercoating would be acceptable. Whatever you do, getting a good coating on the back of the repair is a critical element, no matter what repair procedure is used!

DUCKY 11-03-2005 08:33 AM

If I can get to the back side I'll do that, but my concernes
are all those places where the back side is not accessable
or very difficult to get to.

jcclark 11-03-2005 08:35 AM

You really need to consider a stud welder, I got one for about
a hundred bucks and it works great, and no more holes.

overspray 11-03-2005 08:35 AM

If you can't weld the holes a good fix is to use marine epoxy to fill or cover from the back side. It works with fiberglass matt (thin) or cloth and for the most part marine grade epoxy is water proof. Sand or grind and bondo sticks to it just fine. I get mine (POXY-PRO I think) at Menards. It seems to hold up better than fiberglass fillers as a moisture barrier and it's handy around the shop.


red65mustang 11-03-2005 08:43 AM

"no welding required"
use 2 part body panel adhesive with a backing patch piece of metal on the inside of the hole (plastic filler and blend the patch if it's gotta be pretty)

use enough so it comes thru the hole a little, sand that down, plastic filler on top to blend your done.....

fiberglass cloth and resin is hydroscopic, gelcoat on fiberglas is the moisture barrier....

kenseth17 11-03-2005 03:32 PM

My take on this if you can't weld them would be to indent the holes a little then use something like panel adhesive to fill the holes first prior to plastic filler. This is if the area isn't low already, like trim holes. Being it is dented already the area may be a little low after pulling and you can apply it past just the hole. You can get small tubes adhesive from 3m I believe where a gun to apply isn't needed. You don't want it just adhering to the hole only. Fiberglass filler would be my second choice. The stud welders are a good investment, as well as a small welder. I've gotten plenty of use out of mine. I don't miss drilling holes for dent pullers or pull rods.

mitmaks 11-04-2005 09:37 PM

either fix it right way or pay someone to fix it right way.

BarryK 11-04-2005 09:42 PM

Solder the holes with a soldering gun, than apply your filler, if you don't have access to a welder.

For next job buy a stud gun.

adtkart 11-05-2005 05:04 AM

If you have access to the back side, why would you drilll holes to pull it anyway? You should be able to work out the dent. If you haven't drilled the holes yet, don't. Either buy, or find someone that has a stud gun and use it. If you are going to repair it, repair it, not just cover it up.


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