Fiberglass hood repairs

[sodly]

As someone who's never worked with fiberglass before.... how hard is to to have holes filled on a fiberglass hood?  A big deal?

[fxfymn]

I have never done automotive glass work, but I have fixed lots of boats in my time. I don't think it will be a big deal. Clean the back side of the hole, rough it up, coat with resin and patch it with glass. Re-coat with resin and squeeze out any extra resin. The front can be filled with resin or Bondo. Getting paint to match will be the hardest part of the fix.

If it is a large hole you may need to build up the surface with glass and resin before you complete the final finish.

The key to working with glass is to remember that the strength comes from the glass, not the resin. Use only enough resin to saturate the glass and do your best to remove any excess resin before it hardens.

[Vladislav]

If your plan is to get a good reliable repair on a fiberglass part you should grind the hole or crack over to form the edges biased. As closer the angle of the ground surface to the part's surface as wider the area new material adheses to the part. And stronger the repair. I.e. if you work out a hole of 1/2 you should gring for about 1 or 2 inch all around. This allows also to minimize circular traces over repaired spots after your paint will almost dry in a half a year or so.

Clean an area to repair. Grind over or sand every thing you will apply resin onto. Degrease with solvent. Cut some pieces of glass mat of a size a bit less than the area to repair. Mix resine, apply onto the surface. For the best do it with a brush. Than put a piece of glass. Brush again with resin and put the next layer of glass. As long as the resin doesn't show it's hardening you can apply as many layers as you need to obtain enough thickness. Or a bit excessive. After the resin is set completely sand the repair "hill" to the parts's level. Some filling might be required after that but could be done easier with body filler as long as you have your structure fix with glass wires already done.

For the best results, especially when you fix a crack, you first grind off one side of a part for a bit more than half its thick and do repair. Then after the resin is set up completely you grind the other side getting up to the material you already applied. And glue up a glass-resin slice-cake again. This way you almost delete a damaged area resting new material there only.

[BillyT]

Everyone has  given good advice for fiberglass repair! Get the paint sanded off a few inches beyond the hole. Like Vlad said be sure to degrease the area you are working,this is important so the resin will adhere to the surface! If you see any bubbles between the layers of glass mat one of those plastic sqeegees you use for bondo works well to force the bubbles to the edge of the repair. Get a pack of those throwaway gloves like a doctor uses,the resin can burn your skin,and the fiberglass "hairs" you mix with the resin will cause your skin to itch like crazy! The best place to get supplies is the Napa store.They work with pro bodymen all day and most of their countermen can advise you on procedures. Long sleeves are a good idea if it isn't too hot. An extra layer of mat under the hood will strengthen the repair! Good luck!

[Freightrain]

I've done a few repairs.  If the hole is large enough(and through) make sure you have a backer behind it or the resin/fiber will just sink through.  Few layers of heavy tape should do the trick.  You'll have to dress it up on the back when done.

Blend it out and rough it up so the resin has plenty to bite into.  Make sure to grind out any cracks.  More to fill is better then burying a crack underneath.  You have to work fast with the resin as it starts to get stiff in a few minutes.  Have it all ready, then go quickly.

 

My latest work when someone smacked the bumper on the race car with a golf cart:

Edited September 22, 2016 by Freightrain

[steve p]

tip for the day ,when sanding /grinding fibreglass ,before starting grab some talcum powder, rub it into your skin then sprinkle a liberal dose over your skin again DO NOT RUB OR BRUSH IT OFF the put your overalls /long sleeved shirt /trousers this will minimise the glass particles getting into your skin ,once finished working have a hot shower hot as you can bear ,let the hot water run over your body to draw the fibres out your skin .get dressed as no one needs to see ya naked ,if your still  a bit itchy just rub some talcum powder on the affected areas and bobs your uncle.            steve   this does work

[mowerman]

Done a lotta it it's pretty rewarding when it come out good these other fellas about covered the process lotta fresh sandpaper and take your time good luck.bob

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[Maddog13407]

Napa around here sells some good bonding resin already pre mixed in packets you put in a caulk type gun. forget the brand but its pl100 and pl150 or something. one is stronger and one is heat activated to. that's mostly what we use for repairing truck hoods

[41chevy]

44 minutes ago, Maddog13407 said:

Napa around here sells some good bonding resin already pre mixed in packets you put in a caulk type gun. forget the brand but its pl100 and pl150 or something. one is stronger and one is heat activated to. that's mostly what we use for repairing truck hoods

That is some of the best glass repair item about. Excellent for panel bonding. Used that and chopped glass on my Valkyre body mods.

[Maddog13407]

it could be 100 and 150 or 200,i forget the model numbers but it comes in a big packet and you put it in a canister type caulk gun. we use that we fiber tape on all gel coat, fiberglass and the weird plastic type truck hoods

[sodly]

Thanks for all the comments and tips fellas.  I don't plan to do this work myself, though.  Just wondered how difficult it was for a body shop to do.  Say you have a hypothetical  3" hole to repair in a flat section of a hood (hole was drilled for an accessory that's no longer there).  Is that a difficult/expensive repair?  Not being a Corvette man, I'm not very familiar with how hard it is to find someone to work on fiberglass.  

[Maddog13407]

not much more different than Bondo or drywall work..... you can always sand it off..... id rather use the Fuzor brand premixed resin at Napa tho than the old fashioned two part stuff. wear gloves, use a small chemical brush to push the resin into the fiber mat and smooth out with a bondo spreader. intimidating at first but not that bad

[fxfymn]

I think glass work is much easier, and should be less costly, then metal work. There are no issues with shrinking, warping, or stretching metal like there is when you weld a patch into sheet metal. This is particularly true in your case since you have full access to the back side of the hole.

[Vladislav]

13 hours ago, sodly said:

Just wondered how difficult it was for a body shop to do.  Say you have a hypothetical  3" hole to repair in a flat section of a hood (hole was drilled for an accessory that's no longer there).  Is that a difficult/expensive repair?

I would say about half a day to do for a one man. Or maybe less when it's his everyday job and he has everything for by his hand.

I mean just glueing up a hole with sanding to a flat surface. Filling up, primering and painting should be count extra.