Fiberglass Repair

[jonny]

I received a PM from another ASF member asking if i could provide some tips on fiberglass repair. I thought it would be cool to start a thread on this topic and get some input from other members regarding this dusty, itchy job. I work in a production autobody shop so my experience in this area of repair is limited to the amount of fiberglass repair work that comes through the door which isn't very much. The senior bodyman at my work used to work on a lot of Corvettes back east, so i have learned from him as he is very knowledgable in this field. I know alot of members on this site have a lot more experience in autobody repair than i do, so please feel free to fill in any gaps i may leave.

Safety 1st:
Fiberglass gets everywhere and itches like a bastard. I like to wear a pair of painters coveralls that have elastic ankle and wrist bands and a hood. A good quality NOISH approved respirator w/dust filters is a must.
Also always wear gloves, ear plugs, and eye protection.

Materials: Lordco, Valley Car Color etc. carry everything you will need.
Check out this site for materials www.evercoat.com
Fiberglass resin
Quality fiberglass mat the kind that can be peeled into thinner layers for curved panels.
1 1/2 paintbrushes
Fiberglass reinforced body filler
Various grits of sandpaper
razor blades
Wax and grease remover
Finishing putty

Tools:
Angle grinder or die grinder
D/A sander
Filler spreaders
Sanding blocks
In-line sander

Clean surface to be repair front and back (if access allows) with wax and grease  remover or suitable cleaner. Grind area to be repaired creating a \"V\" groove. This is done by grinding back the existing material approx. 4 to 6\" and bringing the material to a sharp point. Grind both sides if you can if not one side will do.
Cut two peices of fiberglass mat, one approx 2\" bigger all around than the area to be filled and one approx. 1/2' bigger. If you are working on a wicked curve the mat can be peeled to seperate it in two peices to take the contour of the panel being repaired. Clean or blow off the repair area. Mix resin with hardener. Very litte hardener is neccesary for this, there are no hard and fast rules as to how much hardener to use you kind of learn as you go. Mix the hardener thoroughly using a stir stick or paint brush, you will notice it turn from a pink color to a greenish color. With your paintbrush saturate repair area with mixed resin. Apply one peice of mat, large or small it is your choice once again you learn as you go what works best for you. Saturate mat with resin being careful not to overwork it as the mat will start to seperate. Apply your second peice and saturate again with resin mix. It is a good idea to let this set up for approx. 12 hours. I like to apply mat at the end of the day and let it sit till the next morning before working any further. Using an aggressive sandpaper (40 or 80 grit) on a D/A sander shape the panel to desired contour and shape. Mix up some fiberglass reinforced body filler and spread over repair area to fill remaining low spots. Sand with D/A sander, maybe a little block sanding to finish. Apply a thin coat of putty and sand with 180 grit when hardened. Send to the painters for primer and paint.

Have fun and work safe.
Jon.
 

[Matt]

Although I miss bodywork a bit, I sure don't miss this stuff. Jon pretty muched nailed the process.

Keep in mind the less skin you have exposed while working with fiberglass the happier you will be after the fact. Also, never wash your clothes you were wearing with anything else, especially your underwear. Trust me on this one.
 
I worked on semi- trucks where most of the hoods were fiberglass and most of the time I didn't have 12 hours of cure time. An infrared heat lamp works wonders in \"kicking\" the resin to move onto the next step.

When you grind the panel before the lay-up, make sure you have gone large enough for the repair as fiberglass on paint/undercoat/ road grime will not last. I also preferred to tear the mat rather than cutting it, I found it left the edges blended instead of a sharp edge, a little easier to finish with.

If the back side of the damaged area is not accessible, drill a couple 1/8\" holes next to the damage. This will enable you to see the thickness of the fiberglass while you grind it down because you do not want to grind it all the way creating a large void. On some cracks, this wont be necessary, but if it is a crushed type damage it may help you.

With large voids, aluminum tape works well to create the shape you need as does cardboard.

[James Buchan]

A good quality NOISH approved respirator w/dust filters is a must

Something to add about safety and personal protective equipement - Jonny brings up a good point about respirators and choosing the right level of protection for the task you are to about to complete.

Above in the quote from Jonny you will see \"dust filters\" you have to keep on mind that not all filters are adequate in protecting you from vapours/dusts or whatever you else you might encounter. As an example everyone has seen a dust mask and I am sure lots of people use them for a variety of tasks (paper gauze that covers your mouth and nose) - these are useless for almost all tasks other than sweeping something like sawdust.

For working with fiberglass I would suggest a 3M half mask (7500 series) with a 6001 (OV filter with a P100 a pre-filter) or a North half mask with a 75001 filter. This would be a minimum level of protection and would be dependant on the level of ventilation and other variables that may be present.

If anyone ever has a health/safety/environment related question feel free to ask as I am more than happy to help. Or if you ever need a piece of protective equipement contact me as well as I am able to get some kick ass deals due to the amount we purchase from our suppliers.

[jonny]

Hey Matt.
Good call on the infared heat lamps. I have tried this before with limited success. The edges of fiberglass resin that I had added kept lifting. Kind of the reason why I now try to let the stuff set up overnight whenever possible. What do you recommend for bake time and distance to keep the lamps from the workpeice?  I would like to try this again to speed my turn around time up.  

[Matt]

I never had that problem, and I would vary the time/ distance of heat lamp depending on how much I wanted to get done in a day. We used \"hetron\" resin, it worked for both traditional fiberglass and SMC, the only product I know of that did work for both.

Letting it cure overnight is your best bet, and I also tried to do most my layups near the end of the day but sometimes it just wouldn't work out that way.

Did you let the substrate cool back down after you had the heat lamp on it? or maybe you need just a touch more hardener.

I do know there was good money in fiberglass repairs, pulling 10-25 hours out of a 8 hour day if you wanted to work hard.  

[epic3]

I do alot of fiber glass fabrication as a stereo installer and one of the most handy tools I've used to prevent bubbles and edges lifting is a god set of ribbed aluminium rollers they range in price from $5 to $15 and just soak em in acetone to keep them from getting ruined

[Matt]

That's a good tip too,

Fiberglass is a funny material to use, and only experience will you ever be good with it. Find a system that works for you, I could never use the rollers without gettin angry and tossin them across the shop only to use a paintbrush. but that may just be me

[epic3]

Ya can't use the rollers till you get a few layers of wet stuff down then I use them to soak the excess resin into the next layer sometimes two layers of dry matt that I put down. If you have to much resin you can get brittle fiberglass in the end that just cracks easily

[GRK]

I used to use the air rollers all the time in the chemical plants on fiber glass pipe . They work good but you do need  a couple of layers fairly wet and roll from the middle at bottom to outside edges working up.

Gary