Fiberglass for dummies.....I'm the dummy.

[BigB98]

So lets say a guy puts a little too much gap where the door hinge lines up with the front clip....What is the best way to add more material to that end piece of the door hinge thingy? I want to make sure it's strong enough, etc...Do I use just use a fiberglass strand filler or fiberglass matt or?

This fiberglass dummy appreciates your help.

 

[Dave Deerson]

Are you extending a flat door skin or building up the door jamb area? For skins/panels I have done this to build up panel gaps with good results:
1. From the inside, grind down the glass back about 2in and tapered to a sharp edge. Then using the metal foil type HVAC duct tape,apply to edge to be built up as a "extension mould"( the metal tape gives good support when doubled or triple layered). Then lay up very thin (I actually separate 3oz mat to yield even thinner layers) layers equal to about 3 full layers.

2. When that cures, remove the tape, grind the top surface back about an inch and lay up on or 2 layers.(you are trying to "sandwich" a new section to the old").
3. Sand/prep/fill and prime.
If done carefully, the repair can't even be seen from the inside.
I should also say that I use laminating resin that does not have the wax in it. This gives a better secondary bond, but the sticky surface must be sanded off or spray the surface with a coat of PVA.
I'm sure there are other methods. Good luck.

Dave

 

[Neal]

I used west system epoxy and colloidal silica. Back the gap with tape. Scuff the area to be built up with 100 grit. Mix to a peanut butter consistency. Fair to shape.

 

[Jack]

I believe the method selected should be based upon the gap distance. Anything more than 3/16 inch, I would use Dave's method of fiberglassing using 1.5 Oz mat.
Smaller gaps can be done with Neal's method using a silica filled epoxy as he stated.
I have seen folks use "Bondoglass" but I always worried that it would break out.

 

[Jim Rosenthal]

Bondoglass etc will not stay there very long. If you have to modify a fiberglass panel which was made using polyester resin, you should use either epoxy (West, System 3, MAS, etc) or vinylester resin (3M is what we use) Polyester resin is great for laminating panels and constructing pieces, but it bonds poorly to itself; its gluing properties aren't very good. Epoxy and VE are MUCH better and quite a bit stronger. If you use the right additives, they will fair pretty easily and take primer the same as polyester, so the final product won't show any difference where you built it up.

The body for my car had been around for several years before we were able to get it on the car, and numerous cracks had appeared. We ground those areas back and layered them with fiberglass cloth and VE resin, then sanded to shape, and then faired with VE resin and a filler. So far, so good. We had other areas where things needed to be extended or reshaped, and we used templates like suggested above to hold the shape until the part was set up and would hold shape itself. In one instance, we needed to lengthen a rocker panel cover- one side was made too short for the car. We sawed it transversely and then fixed the halves about 3/4" apart using wooden splints and self-tapping screws, plus cardboard covered with a release fabric to help us fill the space in. I strongly recommend the use of release fabric when you are doing jobs of this kind- the one we use is called "Peel Ply" and is available through West System dealers. It can be reused over and over again.

I have done repairs of this type in the keel of my 36' sportfishing boat using these techniques; some of the repairs are nearly fifteen years old and holding up fine. I formerly used epoxy for everything, but after using VE resin for all the work on the GT40, I may use that on the boat as well. It is great stuff.

 

[Jack]

+1 Jim. I would recommend VE resin for most of our needs. It works very well with matt, unlike epoxy.

 

[Howard Jones]

Lets use the door as an example. The gap between the leading vertical edge of the rear clip and the vertical trailing edge of the door is too wide. Lets say you need to close the gap from 3/8 inch wide to 3/16 inch wide.

Orientate the edge of the door that will have length added to it horizontally, you must do this or the strips will just slide off from gravity. Cleaned and scuff up the edge by sanding off any paint and scuff to 80 grit.

Then cut a length of fiberglass mat 1/2 inch wide and to the same length of the edge of the door that will have material added to it to decrease the gap width.

Bond the single strip of mat to the door edge so that it forms a 1/2" wide ledge the full length of the gap. Do only one strip the first time so that you have a solid flat piece to work with later. Tape off the work area and cover the rest of the door with cardboard to prevent the dripping resin from making a mess of the rest of the door. The smaller the mess the less sanding you will need to do to fix it later.

When it hardens you will have the door sitting vertically on end with the rear edge up and a 1/2" wide hardened strip of fiberglass centered on the edge horizontally.

Now add as many additional layers of 1/2" wide strips of FG mat as needed to add length to the door and therefor close the gap width. When you ave added enough "plys" of glass-mat and they have hardened you can trim the edges of the additional mat (now 3/16 + a little thick to allow for fine finishing) to bring it back to the original door panel thickness.

This method will result in a very strong all fiberglass edge and you can add length to any edge this way. I did my GTD this way and it has stood up well for at least 5 years with no cracks.

Note: Just building the edge up with bondo will not work at all, this is a waste of time and money and you will need to do it again the right way anyway.

 

[Jim Rosenthal]

Absolutely right. The added material needs to have glass in it in an organized way to have any strength. If it's done right, it is very strong and as Howard says, will stay in there indefinitely.

 

[Jim Dewar]

I also used West Systems epoxy. It worked great with very little effort. I guess we all made the same mistake!

 

[Jack Dunn]

I hope i'm not hijacking this thread, but I'd appreciate the fiberglass experts' help.

I'm trying to restore the nose of an Alba AR5(80's GTP car). The nose was run at the Daytona 24 and has lots of star cracks, esp. over wheelwells(it is very thin fiberglass and there were no wheelwell tubs to protect overlying bodywork-you can imagine the damage).

I've read you must completely grind out and replace any fiberglass that is damaged. If so, how do you save the shape of the nose?
Are there any tricks to repairing something like this? I did not get any bodywork molds with car, and only the one long AR5 nose(I do have a nice short nose, but I'd like to restore the damaged long nose).

I'd appreciate anyone's experience concerning restoration of damaged FRP racecar bodywork.

Jack

 

[Jack]

I remember two AR5's, a Buick powered one and the other had Old's power.
Have you considered making only cosmetic repairs and producing a new mold
using the original as a "plug"?

 

[Jack Dunn]

Mine has a Buick V6. I've seen other Albas powered by ferrari, mazda, olds, even subaru 12 cyl.

I'd like to adequately repair this nose so I can have the car painted and back on the racetrack while I look for another nose/mold.

I've been involved with making a whole fiberglass mold in the past, and I don't have the time (or patience) to do it again.

Jack

 

[Randy V]

Jack - I've repaired fiberglass racecar bodies like yours by cleaning/sanding the bottom side with 36 grit and laying in Mat/Resin, then grinding out the top side damage and laying in more Mat/Resin. Followed up with Featherfill epoxy primer to seal the whole panel.. Yes - the end result is a heavier piece, but not substantially.

You could do the same - and while you're at it - you should consider adding in Kevlar on the bottom side over the tires to absorb the impacts of stones/debris.