first time at fiberglass repair so forgive the ignorance

pulled a nut through the fiberglass on the inner wheel well (attaching a clamp that hold the heating hoses to the wheel well

left with a 1/2" hole

what do i need to do to prep the surface? - do i need to sand down to bare fiberglass on both sides first? or is resin such that it will soak through the dirt, grime, paint and adhere anyway?

thanks!

 

Clean area first with acetone to remove grease and dirt so you don't grind it into the glass. Next use a 2" roloc disk, 36 grit and grind both areas so that they bevel inward and meet with a sharp edge. Then you can lay in your little pieces of matt and isophtatlic resin which has a very low shrinkage.

 

ONLY bare, clean glass.

Dirt and grease - guaranteed fail.

On a small hole like this sand/grind the edges of the hole to a taper back from the edge about 1/2 inch. This gives you more clean surface area for the mat and resin to bond to.

Do both sides at the same time with the wet mat to create a sandwich.

 

Yea, good point.

 

thanks guys - (newbie) follow on questions:

1. 2" rolloc brings up both of the attached - i am assuming you are suggesting the backing plate that sandpaper would stick onto, correct?

2. if so, this looks like an attachment for a die grinder ... is that right?

3. is this 3M #401 (fiberglass resin) an example of an isophtatlic resin?

 

If you have never worked with mat and resin I suggest you experiment and practice a bit first before you do actual repair on your car. Form and shape some pieces of mat with the resin and learn how much time you have to work it before if kicks-off and begins to harden. Mix it carefully with not too much or too little hardener. Once it sets up and gets hard you will be able to form, sand, file it to about whatever shape you want.

With some sample scrap pieces it's no big deal if you screw up, pitch them and try again. Wear the thin gloves to keep it off your hands and have a can of acetone to clean up and get off your hands even with the gloves.

Filling holes in a wheel well should be easy as its not crucial like the body would be.

John.

 

thanks John will do

 

Hi Scott (or anyone) - thanks in advance for your answers to these questions!

 

If you don't have air tools just use something like a lacrosse ball or hardball, wrap the 36 grit paper around it and work the area until you dish out both sides. I doubt the 3m resin is isophtatlic.
https://fiberglasssupplydepot.com/Is...ic-Resins.html

 

or use a dremel to sand back the area
or
Roloc 2 inch or 3 inch - 80 grit
look like this.....
https://www.google.com/search?q=rolo...Vu9jN8lAxTM%3A

 

You can use roloc sanding discs with an electric drill. For a single hole you can even use a dremel with a grinding disc. Put several layers of masking tape over one side to act as a form and cut circles of fiberglass mat to fill the hole, with larger circles to overlap the tapered edge of the ground area. Use the brush to dab the glass and resin into place and compact it as well as possible. They make little rollers to roll out fiberglass repairs in between layers of resin and mat to make a dense matrix. Probably not worth the effort to find one for a single hole. After the resin has hardened, peel off the masking tape and lightly grind the area again and lay resin and another piece or two of mat on the backside to fill it in above final level. Then sand after hardening until flush and smooth. You may need to use a little dab of spot filler on the surface to fill minor air bubbles and pits.

 

Scott - I called 3M - you are correct, it is not Iso, it is ortho

I do have shop air (but excellent suggestion with the ball)

 

thanks Csherman - i see the roloc is a sanding disc and not a cup - got it

out of curiosity, several of the types have a backing that looks like they screw into something...what would that be?

 

A roloc adapter

https://www.amazon.com/Roloc-Disc-Pa.../dp/B003VOO92M

 

I have used this with excellent results, and it's not messy like resin.




.

 

Numerous good suggestions and advice above.

Honestly I would NOT worry about the type of resin. This is due to where you are doing the laminating. No one EVER will know due to you are NOT laminating on an exterior panel that will see sunlight....AND

When you are done..you are going to put the clamp right back into place.

The advice on tapering it correctly is important.... and I can show you photos of the right way and wrong way in a moment.

AS for cutting out circles...I prefer to tear the fiberglass so it has strands and not a defined clean cut edge...which will not blend into the panel like the frayed edge of torn fiberglass. I DO AGREE with making your circles larger as you go but that also depends on how you ground the areas and its size. But do it however you choose.

AS for doing both sides in one lamination step or doing like 'DansYellow66' mentioned. That will depend on how good you feel that you can lay up one side and then seal it off with tape so you can get to the other side and laminate some more and try to get all the air out. Laminating all of it on both sides at one time should be fine due to the hole is so small.

And honestly...in this area there is a way to do it with out even laminating it.

Some photos... so you can see why tapering your area can make a difference.
https://www.corvetteforum.com/forums...-drag-car.html

DUB

 

Surface prep is key. This stuff is terrific.

 

many thanks Dub

when you say this: "And honestly...in this area there is a way to do it with out even laminating it." - what is that way?

thanks again for the tips

 

thanks for the tip phil2303

 

Dub - when you say:

AS for doing both sides in one lamination step or doing like 'DansYellow66' mentioned. That will depend on how good you feel that you can lay up one side and then seal it off with tape so you can get to the other side and laminate some more and try to get all the air out. Laminating all of it on both sides at one time should be fine due to the hole is so small.


in the videos i have seen on line, i have never seen them put tape over the patch - is this what you are suggesting? - if so, once the one side is dry, what does the tape do for you while you start on the other side?

thanks