the Dune Buggy Archives
DBA Forum - Not logged in
Previous Next Up Topic Public / General Discussion / Filling in small holes .... (12833 hits)
By JohnnyOCock Date 2010-10-06 11:09
The previous owner must of drilled 100 or so holes in the fiberglass body.   I'm preping the body and want to fill them in.

From underneith, looks like some holes were filled in with bondo (you can see the hardened drip) .  Seem to be holding up.

Is this method ok, or is there a better way ?
By Jeffrey P 655 Date 2010-10-06 12:11
The best way would be to taper them out to about the size of a quarter (assuming they are small holes. For larger holes the taper needs to be larger), duct tape a small piece of wax paper behind the hole, and then fill with a mix of chopped up matt and fiberglass resin. The sand smooth, fill and pinholes with a two part glazing compoud, prime with a high build primer, block, and shoot your paint.
By Allison Daytona Ken Date 2010-10-06 12:34
Jeffery is right fiberglass resin and cloth are the best but if the holes are small you can also use another product , it has different names, Tiger Hair, Kitty Hair, etc, etc, it is more like a body filler and uses a cream hardener verses a liquid hardener, it is a lot less messy , and a lot easier to use . Here is a link to one brand      Ken.............
By Manx1173 Date 2010-10-07 14:32
If they are small, I would use West Marine epoxy with either high density additive or fairing additive.  High density is stronger (but a pain to sand).
By Jeffrey P 655 Date 2010-10-07 15:52
I would also suggest that you consider the compatibility  of differing materials if that is what you choose to do. Fiberglass expands and contracts. Having similiar materials in your repairs is important. Your not looking for alot of "strength" per se if your just filling small holes.

Also, no matter what you choose, the tapering of the hole and how you finish the repair is as important as the material you use.
By Jeff GS Date 2010-10-08 01:07
Hey Jeff, so how does one actually go about properly tapering the holes?

I too have lots of leftover pop-rivet holes that will need to be filled.  I need something fast and repeatable that does a proper taper job with the right angle and good coarse finish surface for bonding.  I've heard about tapering the holes before filling lots of times - but nobody describes exactly how to do it!

Some kind of rotary tool?  Seems like some sort of very shallow V angle 60-grit sanding wheel you could pop on a high speed drill motor would do it?  But I've never come across such a tool.

By Jeffrey P 655 Date 2010-10-08 14:12
I use my 4 1/2 grinder with a grinding wheel. It doesn't have to be an exact circle. The grinder does them real quick & provides a nice coarse surface for the new resin and matt to soak into the existing fiberglass. Its also really rather controllable.

I know its hard to accept that your actually making something bigger in order to fix seems counter intuitive...but in reality your allowing a better base for the repair to bond to and spreading out the stresses and flexing issues. And I know the number of small holes can seem very overwhelming but its not really a big deal. A grinder can wallow out a appropriate hole in 30 seconds. And filling them is also not a great big deal. Chop up some matt (I put mine in a cardboard box and walk around with it), mix up some resin and fill them up using a disposable brush. They don't have to be perfect. A little too little? No problem...a little filler will be fine. A little too much? No big deal....just sand them flush with 80 grit and fill any pinholes with filler.

I also am not afraid to use good fillers in moderation (ie: NOT 1/4" thick). The other day I was filling some pinholes on my Avenger with a real good quality two part spot putty. I was applying it with a small, thin, and very flexible metal spreader. A decent amount cured up on me on the spreader while I was temporarily distracted. No matter how much I bent that spreader the putty would not pop off or even crack. And I was bending the crap out of that spreader. It certainly more flex than a fiberglass body would ever flex.

You can see some hole repairs on the following pics.

By Jeff GS Date 2010-10-09 12:14
Thanks Jeff,

When you say a "grinding" wheel, are you talking about a metal grinding (solid like) wheel like you'd use on steel?  I got away from those types of wheels on my chassis work and went to flap-style discs.  They work great on cleaning up steel, but not sure how controllable they would be on fiberglass?

Here is the flap-disc I'm familiar with:

Seems like working the edge of a wheel like this down into the fiberglass wouldn't result in a very nice flared opening?  More likely a series of gouges!

Any pics of the holes you've prepared for filling.  Everyone posts pictures of the "before" and "after", not showing what took place in-between!

BTW, that buggy in the photos looked fantastic after your excellent work (I followed it during your original build thread).

By Jeffrey P 655 Date 2010-10-09 17:56
Yeah...the stone like wheels you use for metal grinding. Thats what I use. I find them very controllable. They take really no pressure and cut very quickly. Usually when you really have to lean into something to make it work you lose controlability. The stone like wheels take very little pressure.

And yes...they are more like gouges. But if you work it through you will realize that it really doesn't matter. Here is my reasoning:

You want the repair to be invisible under the paint right? Is a perfectly round hole any better than the erratic shape of a gouge? I don't think so as long as the taper is sufficient. If its egg shaped or oval is that still fine? What you look for is a nice taper and a rough surface. The shape doesn't matter. It doesn't matter if you start off with two rivet sized hole and grind one out perfectly round and the other egg shaped.  On both you fill with matt/resin, sand and then skim with filler. If its perfectly blended then neither will show under primer/paint. The real key is to make a good taper and then finish it correctly.

I wish I had some pictures of what they look like. Most of the time when I am grinding glass my wife does not want her camera anywhere near me. If you look at my prior pics you can see lots of different shapes of the filler. Some are kind of elongated and some are more round. Its easier to make a true circle on larger holes than it is on smaller holes.
By SHERMAN Date 2010-10-30 21:44
hey what about a countersink or a burr bit for a dremel?

By Brad H 1498 Date 2010-10-30 21:56
The rotary file ,yes, but messy. The countersink will make too smooth a hole you want a bit of edge for the resin to bond to.

By jim s 1837 Date 2010-11-01 21:40
Jeffery, I must say that is a good way to patch holes. I did that this morning before work chopped up the mat and made a mix. It gave me good working time and I was able to put it on with a paint stick believe it or not

Thanks a lot
By Jeffrey P 655 Date 2010-11-01 22:35
Glad it worked out for ya Jim!

I think I must have 100 or more repaired holes under my belt!
By Brad H 1498 Date 2010-11-01 23:25
Jeffrey P 655 Date2010-11-01 22:35

Glad it worked out for ya Jim!

I think I must have 100 or more repaired holes under my belt! .

So you've only fixed one buggy full of holes :-) :-) :-) Rookie!!! LOL

By Jeffrey P 655 Date 2010-11-02 00:20
I only count the ones bigger than a pie plate!
By Bill E 1873 Date 2010-11-14 03:51
Thats a sweet looking buggy love the color. I too am filling loads of little holes and some small cracks very time consuming. Bill
Previous Next Up Topic Public / General Discussion / Filling in small holes .... (12833 hits)

Powered by mwForum 2.10.2 © 1999-2007 Markus Wichitill