Fiberglas repairs

[Crosley.In.AZ]

The  air dam on my car trailer needs some repairs after 15 years.

In the photos I hope the problems are seen clearly.  One corner the wood is exposed / rotted.

In a flat area the wood is exposed from the glas gettin a bit thin.

How deep to cut / grind the areas for repair?  Insert some fresh wood in the areas or foam or inject something or what?

Years ago I would simply cut and grind ... then slobber on the fiber mat material and resin....... still the same technique?

Good resins , bad resins?

[jaybee]

Wood rot is a lot like rust in that if you don't cut it all out it will just show up next to your repair, if you trap moist wood under the fiberglass.  Looks like your glass isn't real thick, which would make it hard to undercut the repair to help in the bonding.  Looks like a small area and if it isn't structural I'd think you could cut out the bad wood and build up with fiberglass.

[enjenjo]

If you can get some Kwik Poly  http://www.epreservation.net/Products_&_Services/Listing_Detail.cfm?Listing=904

It works good for killing rot in wood, and stabilizing whats left. Then you can fill any voids with a fiber filler plastic filler, Long and Strong or the like. Cover it with a couple layers of fiberglass mat, using epoxy resin, and you should be fine.

[40]

OK...I really am not intending to hijack this thread but I have a fiberglass problem as well....It's not car related but maybe someone can help?I have a fiberglass shower unit in one of the baths that has developed a crack about 6" long....It was a very "soft" area from day one and finally split....I did not notice it untill it was too late.I need to repair the crack as well as reinforce that area of the floor to prevent it from reoccuring.It is a built-in unit...not impossible to remove/replace but it wouldn't be much fun I am thinking...maybe laying a couple of layers of matt over the entire floor?? I have absolutely ZERO experience with fiberglass,cars or otherwise.Any ideas???

[jaybee]

OK...I really am not intending to hijack this thread but I have a fiberglass problem as well....It's not car related but maybe someone can help?I have a fiberglass shower unit in one of the baths that has developed a crack about 6" long....It was a very "soft" area from day one and finally split....I did not notice it untill it was too late.I need to repair the crack as well as reinforce that area of the floor to prevent it from reoccuring.It is a built-in unit...not impossible to remove/replace but it wouldn't be much fun I am thinking...maybe laying a couple of layers of matt over the entire floor?? I have absolutely ZERO experience with fiberglass,cars or otherwise.Any ideas???

Without reinforcement on the backside or some sort of bracing against the floor I'd strongly suspect your repair will "hinge" at the crack and crack at the same point again.  It might have a shot if these things were sturdy and stiff, but they're usually pretty thin to begin with.  Sorry, that's not the most convenient answer but I'm pretty sure that's what will happen.  Still, if you want to try it you wouldn't have that much to lose.  It isn't cracked across the drain, is it?

[enjenjo]

OK...I really am not intending to hijack this thread but I have a fiberglass problem as well....It's not car related but maybe someone can help?I have a fiberglass shower unit in one of the baths that has developed a crack about 6" long....It was a very "soft" area from day one and finally split....I did not notice it untill it was too late.I need to repair the crack as well as reinforce that area of the floor to prevent it from reoccuring.It is a built-in unit...not impossible to remove/replace but it wouldn't be much fun I am thinking...maybe laying a couple of layers of matt over the entire floor?? I have absolutely ZERO experience with fiberglass,cars or otherwise.Any ideas???

Can yo get to the back side of it at all? through the crawl space or something? Squirt some foam into the void to stiffen it up, and then patch from the top. It may be hard to match the gell coat color.

[docchevy]

Good suggestions.  My boss taught me a little trick that works great for finishing.  You do the wood and 'glass work, then paint on the resin for the top coat and wrap it with aluminum foil.  the foil will keep it from dripping and the surface will cure flat!  Then the foil will just peel off without leaving anything in the resin, if you keep it flat.  I like to put a piece of plywood on the bottom side and support it with a jack or something.  It works out really nicely and avoids a lot of the mess!
    Oh Tony, Thanks for the 700R pages I used them two years ago!

[DrJ]

I would use expandable HARD when set URETHANE foam, like Enjenjo suggested.
The Polyester or Epoxy resin won't attack urethane foam, but it would dissolve "styrofoam" like you hit it with a blow torch.
Cut out the rotted wood and squirt the foam in the area, Leave the glass on if you can so it forms the foam but then cut or grind (I hate flying glass fibers!) anything that looks "milky" from shattering or plastic breakdown. Scarf the edge about 2" so you have some bare fibers to mechanically bond to. Shape the hard foam to your liking but about 1/8" lower than you want the finished surface, then get some "surfboard laminating resin" to lay up about 6 layers of cloth. at the scarf, lay the first layer almost allthe way to the finished edge, and then lay them a bit short each layr so there isnt a layer buildup to need grinding off before applying the "surfboard finishing resin"

Same with the "hole" cut it back far enough to get the rot out, fill with foam and refinish

glass layer edges
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On the tub, I'd drill a hole and squirt in the foam, walk on it, if it's still got soft,actually unsupported by the two or three boards they put under them areas, drill more holes and add more foam. The foam expands a lot and at about 80 PSI so don't put in more than the space can handle at one time or it WILL lift the tub off the floor.
In fact you might want "breather" holes.
Then scarf the crack back 2"or so to each side of the crack the whole thickness of the tub and laminate it back up.
Then surface coat it with "surfboard finishing resin" or have a tub refinising service do it for you.
If you go that route, you might want to consult with them first. they might just be able to fix the whole thing for less than you can buy materials

I prefer working with Epoxy to Polyester, just because it's not "sticky" to work with, and smells like taffy, but be careful. The fumes are heavier than air and can and will collect down where you are working and KILL YOU before you realize it and flammable, so they will creap over to that water heateror gas dryer in the corner of the garage and Ka-Boom!
Ventilate!!!!

ALSO WARNING!!!
MEKP the polyester resin catylist, WILL blind you if you get it in your eyes!
They say you have 10 seconds to wash all of it out or you will be blind in a month, no antidote. No shyte

[40]

Thanks for the suggestions! I had thought about the expanding foam idea but wasn't sure how it would react.I don't have access to the area beneath the shower as it's in the lower level,sitting on the concrete floor....however,I can drill a couple of small holes in the face of the bottom of the shower or perhaps can dis-assemble the drain to the point where I can inject the foam around it.I have no idea how to work with fiberglass and perhaps the best idea,as was suggested, is to call one of those "Surface Doctor" type people to resurface it....The couple of days it would take me fooling around with it would surely be better spent working on my 36 Coupe Thanks for the help!!

[Crosley.In.AZ]

bump

[WZ JUNK]

Sounds like a lot of good advise.  I would only reinforce the comment about tapering the repair back at the edges.  In addition do not vary the overall thickness of the repair much from the original thickness of the piece you are working on.  If you have a thick and thin area next to each other, it will fail or break between these two areas.  This is one of those cases where more is not necessarily better.  If you do need to join a thick and thin piece, they need to taper into each other gradually.

John

[Arnold]

I would use expandable HARD when set URETHANE foam, like Enjenjo suggested.
The Polyester or Epoxy resin won't attack urethane foam, but it would dissolve "styrofoam" like you hit it with a blow torch.
Cut out the rotted wood and squirt the foam in the area, Leave the glass on if you can so it forms the foam but then cut or grind (I hate flying glass fibers!) anything that looks "milky" from shattering or plastic breakdown. Scarf the edge about 2" so you have some bare fibers to mechanically bond to. Shape the hard foam to your liking but about 1/8" lower than you want the finished surface, then get some "surfboard laminating resin" to lay up about 6 layers of cloth. at the scarf, lay the first layer almost allthe way to the finished edge, and then lay them a bit short each layr so there isnt a layer buildup to need grinding off before applying the "surfboard finishing resin"

Same with the "hole" cut it back far enough to get the rot out, fill with foam and refinish

glass layer edges
________________________________1
____________________________2
________________________3
____________________4
________________5
_________________________________last


On the tub, I'd drill a hole and squirt in the foam, walk on it, if it's still got soft,actually unsupported by the two or three boards they put under them areas, drill more holes and add more foam. The foam expands a lot and at about 80 PSI so don't put in more than the space can handle at one time or it WILL lift the tub off the floor.
In fact you might want "breather" holes.
Then scarf the crack back 2"or so to each side of the crack the whole thickness of the tub and laminate it back up.
Then surface coat it with "surfboard finishing resin" or have a tub refinising service do it for you.
If you go that route, you might want to consult with them first. they might just be able to fix the whole thing for less than you can buy materials

I prefer working with Epoxy to Polyester, just because it's not "sticky" to work with, and smells like taffy, but be careful. The fumes are heavier than air and can and will collect down where you are working and KILL YOU before you realize it and flammable, so they will creap over to that water heateror gas dryer in the corner of the garage and Ka-Boom!
Ventilate!!!!

ALSO WARNING!!!
MEKP the polyester resin catylist, WILL blind you if you get it in your eyes!
They say you have 10 seconds to wash all of it out or you will be blind in a month, no antidote. No shyte

 About the strongest type of f/gl repair is with the VERY heavy cloth.Not the mat. But it makes regular f/gl cloth seem like Kleenex. Especially the weaving.I think it is referred to by some in the trade around here as "Gun Cloth"? You are probablly gonna have to hit a plastics place that really doesn't deal with the public to get it. You will know if they have it. It is THICK! You'l also know when you use it by the amount of resin it takes. This stuff is VERY strong! and actually can have/has a fair bit of flex to it.
 There are different qualities of resin too..I buy mine from a plastics supplier.
 I like to get all the rot out..however..sometimes you need to leave some to retain the original structure. If it is wet/rotted and I can't get it all out..I find that lacquer thinner is a pretty good drying agent. A little common sense when using that around plastic/f.glass goes a long way.
 In areas that are tough..I always try and make some sort of a mould. I like to use thick corrugated cardboard from boxes. I try and somehow get this into blind areas.I find this extra good..because the resin soaks into it too.
 As for filling really tough areas..I bore holes..all kinds of stuff. If it is nasty tough..I put the mixture of resin and hardener into one of those dollar store plant sprayers..and spray it in first. Next I may put some in some sort of a syringe  and try and force some in.For the actual filling..a good stiff mixture of resin and short strand fiberglass is very good and strong.
 For areas that you need "cling"..like upside down..it is best to buy some of the special additives/fillers that the plastics places sell. Ya..I know that ya can make up a pretty stiff batch with the talc..but it can sag..lose it's grip because of the weight of it.
 I just buy Baby Powder..the corn starch stuff..talc..and use it as a bulking agent for final finishing.

  Epoxies..WOW!..a few years ago some of the newer  "cold set" types..with rubber in them.Different degrees of flex for cold weather.or vibrating/.flexing  use. And of course the Kevlar cloth for brute strength.

Just too expensive for me. Plain 'ol glass works great for me in a lot of areas!

 HAHA..that expanding foam..the stuff that got REAL hard..and REALLY expanded..is actually pretty hard to come by in our climate in S.Ontario..very cold..then very hot..very damp..then very dry. WAAY too many complaints from customers at the large building/home supply/hardware stores..about that stuff and the problems it can cause! when it expands way too far and with waay too much force. That coupled with our climate..the weaker expanding foam is still very popular

 YES! The hardener..the data sheets here say "SECONDS COUNT before medical treatment"