How to Work Fiberglass Right

So there are a lot of us working with fiberglass bodies, accessories, and parts that need repair, modification or total re-work and it seems that there are a lot of ideas being tossed out as "The Gospel" for what's right and what's not. I picked up my approach by talking to a guy with 40+ years of paint & body, much on glass or using fillers the right way for long term stability, and reading tech articles and books on glass working. That said, my way may not be right for everyone, and simply may not be right!!

I'm posing a question to the guys out there who have been working glass through the years, and who know what's right and what's not without having to ask anyone for suggestions. We have a few guys on here who earn their daily bread slinging resin on mat, and we have a few more who have been building/repairing glass boats, car bodies, consoles, etc, etc, for many years. My thoughts are that it would be a big value to have some true expert input on something like 1) repairing a hole in a panel, 2) repairing a rolled edge, like a door jamb, 3) extending a panel, like a door or hood edge that may need an added 3/4" to close a gap with the jamb, 4) molding a part where one has or makes a mold, lays up mat & resin and then pops it out after curing to finish, maybe relatively small parts, 5) making a panel from scratch, like a Deuce hood side or... that needs to be flat, and stay flat, and maybe free forming with fleece the right way ?

Any true Glass Master's out there who are willing to share? Looking for some good, step by step ideas on how to do the work and thinking it might save some of us some grief as time goes by.

Good idea Roger, I would buy this book too!

first off you need to know what your fixing glass or SMC sheet molded composite

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Originally Posted by pat mccarthy

first off you need to know what your fixing glass or SMC sheet molded composite

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Pat, for the lions share of what we see here I'd say we're dealing with hand laid fiberglass if it's a quality product, and chopper gun fiberglass if it's lower quality. I don't think that I've seen any SMC sheet molded composites being used for street rod bodies or components, but I could be wrong. For purposes of this thread let's assume Fiberglass, not composites as the title states.

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Originally Posted by rspears

Pat, for the lions share of what we see here I'd say we're dealing with hand laid fiberglass if it's a quality product, and chopper gun fiberglass if it's lower quality. I don't think that I've seen any SMC sheet molded composites being used for street rod bodies or components, but I could be wrong. For purposes of this thread let's assume Fiberglass, not composites as the title states.

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well if your taking hand laid glass or chopper glass that s fine but over the years guys have been fixing what they were thinking was glass when it was smc .what you are looking for is on west systems web pages and making body plugs and making bodys and fixing holes look at any thing on the west systems under jon s . i fixed glass for many years and smc work on many thing s over the years did finish work for jon at one time seen him make many things one of the best i seen. pick a subject and maybe i can put a finer point to how i would do it

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Originally Posted by rspears

. . . hand laid fiberglass if it's a quality product, and chopper gun fiberglass if it's lower quality.

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Dang, Roger - that hurts! :LOL:

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Originally Posted by pat mccarthy

well if your taking hand laid glass or chopper glass that s fine but over the years guys have been fixing what they were thinking was glass when it was smc .what you are looking for is on west systems web pages and making body plugs and making bodys and fixing holes look at any thing on the west systems under jon s . i fixed glass for many years and smc work on many thing s over the years did finish work for jon at one time seen him make many things one of the best i seen. pick a subject and maybe i can put a finer point to how i would do it

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Pat, did you read the first post to the end or stop at the title? There are five different subject lines stated as suggested starting points there, but maybe that's not what you mean by "pick a subject"?

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Originally Posted by Henry Rifle

Dang, Roger - that hurts! :LOL:

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Jack, not trying to throw rocks, just seeking some knowledge.

[QUOTE=rspears;524717]Pat, did you read the first post to the end or stop at the title? There are five different subject lines stated as suggested starting points there,.. maybe that's not what you mean by "pick a subject"?...... yes holes .door jam . what first . body plug . fixing a poor built body what??? you can not do much for a poor body parts that are thin and a air cure lay up out in the sun parts move so that ones been done :)

[QUOTE=pat mccarthy;524720]

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Originally Posted by rspears

...yes holes .door jam . what first . body plug . fixing a poor built body what??? you can not do much for a poor body parts that are thin and a air cure lay up out in the sun parts move so that ones been done :)

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Thanks for your input! Robin? Parkwood? Shine? MP&C? Dave S? Uncle Bob? Others who've fixed stuff for fun & profit?

[QUOTE=rspears;524721]

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Originally Posted by pat mccarthy

Thanks for your input! Robin? Parkwood? Shine? MP&C? Dave S? Uncle Bob? Others who've fixed stuff for fun & profit?

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oh i am done :) why not ask the burning question about a air void in a gell coat ? if you can use a ground glass filler to fix the air pockets ?

chopper gun or hand laid means nothing. type of resin is all that counts. there are many different tiers of resins. just like paint there is good better and best with 50 qualities in each. epoxy is the upper tier, vinylester then polyesters. i use epoxy resin for any repairs , vinylester for any mold work , polyester for things like speaker boxes and such. the key to resin work is cure. best way is to wrap in black plastic and set in the sun for a while. exposed to higher temps than normal.

I want to to make a piece for the top of my grille to the radiator to keep the air from going over the radiator. I have fashioned a fair fit from a plastic trash can lid, how can I make this from fiberglas or some other material that will hold up?

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Originally Posted by 36 sedan

I want to to make a piece for the top of my grille to the radiator to keep the air from going over the radiator. I have fashioned a fair fit from a plastic trash can lid, how can I make this from fiberglas or some other material that will hold up?

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the cost of one in glass will be much more then getting sheet of tin and building it

My tin skills are poor, this has compound curves. I'm afraid I've wasted more on tin already than I could have made it from fiberglas.

Do I need to make a reverse mold out of plaster first, or can I lay over the plastic lid?

Are there other materials besides fiberglas I should be looking into to make this from?

Jamestown Distributors

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Originally Posted by 36 sedan

My tin skills are poor, this has compound curves. I'm afraid I've wasted more on tin already than I could have made it from fiberglas.

Do I need to make a reverse mold out of plaster first, or can I lay over the plastic lid?

Are there other materials besides fiberglas I should be looking into to make this from?

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If you've got a good fit with the plastic lid, and if you can accept that the fiberglass piece is going to be slightly bigger since it's laid on top of the fitting part, then simply wax the plastic with a good coat of wax and lay the glass mat on top. Let it cook off for an hour or so and it will pop off easily and you can then sand it smooth, hit it with a coat of filler and it's done.

Thank you, exactly what I was looking for!

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Originally Posted by shine

chopper gun or hand laid means nothing. type of resin is all that counts. there are many different tiers of resins. just like paint there is good better and best with 50 qualities in each. epoxy is the upper tier, vinylester then polyesters. i use epoxy resin for any repairs , vinylester for any mold work , polyester for things like speaker boxes and such. the key to resin work is cure. best way is to wrap in black plastic and set in the sun for a while. exposed to higher temps than normal.

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Shine,,I know you have had experience with glass,too,,as has Pat.. We all have different methods,and different ways of approaching things with this stuff.. I was taught in the late 70's,by one of the better guys in the industry,,who did his apprenticeship in a boat factory..He went on to become a leading light in boat repair in West Auckland,,and was actually known by many,as the pox doctor,,cos of his experience in repairing polyester yacht hulls,,some of which had spent a year or two in the tropics..Anyway,, my forte has been,for several years,repairing a lot of automotive parts,,including SMC truck fronts,and bumpers,,and the regular fibreglass truck hoods,,from Kenworth,Mack,Freightliner,etc.. All of my work is done with polyester..I have no problem with it,,and I would prefer to do my repairs,,where possible,with what was used originally.. I have a few dirty tricks up my sleeve,for SMC,,and while it's not 100% foolproof,,they still last..
I use polyester for making molds,,with a good vinylester tooling gelcoat.. As a rule,,I don't even have epoxy in the shop,,but do get tired of grinding out crappy epoxy repairs,from inside some panels laid up in poly... ;),,that look like they have been whacked in with a mop,and 4 times more resin than necessary..
I usually set my layups off with an infra red lamp,then leave them to finish.. most of my stuff,that I do in my molds,stays in the mold for two days,or so before I pull them.. Hey,,the black plastic works well,too.. have speeded up the mold curing with that method..
Gunna leave it at that,cos I don't think we need to have too many disagreements in this issue.. One of the reasons I hang back from these threads,,is,that you can guarantee there will be a few differences of opinion.. ;)
Gotta say though,,most of the chopper gun layups I have seen,,are either good,,or real bad,,such as the Deco Rides Lincoln Zephyr bodies..Ya need an experienced operator,with his mind on the job,,and a good guy on the roller to finish..

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Originally Posted by rspears

If you've got a good fit with the plastic lid, and if you can accept that the fiberglass piece is going to be slightly bigger since it's laid on top of the fitting part, then simply wax the plastic with a good coat of wax and lay the glass mat on top. Let it cook off for an hour or so and it will pop off easily and you can then sand it smooth, hit it with a coat of filler and it's done.

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There is no reason,for a fiberglass piece to be larger,Roger,,since a mold is usually taken off the outside surface of that part..If you take a mold from that part,,what comes out of the mold will be the same..... Unless,of course,that the plug is taken out of the mold,,before the mold has finished curing,,in which case,,the mold will shrink slightly..And,,it is very hard to take a mold off a thin plastic item,,or,,as I call it,,a ''street weight'' fiber item..They need to be braced well,,and build the mold slowly,,a couple of layers of glass at a time.. AND,,,DON'T use too much gelcoat in the mold,,as if it's too thick,,it will shrink from the mold as it dries..
For a small item,,I will make my mold about 3mm thick,,built up over a couple of days,and a week of curing..minimum..

done more fixes with polyester it worked . cost as not has much as the epoxy but it has its place . over the years working with smc i used siwss polyester gell for smc for the big semi flip fronts ends re built many with the gell . many times i was the guy that took the part raw and did finish work to paint with no gell coat on the air plane stuff . last time i was close to a boat repair i did not even work on the damn thing i started getting cold and breaking out.i found out the epoxy i can not be in the same shop with epoxy dust. most repair job were someone did not do a good fix were guys think slopping on to much resin with no mat or cloth

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Originally Posted by lamin8r

There is no reason,for a fiberglass piece to be larger,Roger,,since a mold is usually taken off the outside surface of that part..If you take a mold from that part,,what comes out of the mold will be the same..... Unless,of course,that the plug is taken out of the mold,,before the mold has finished curing,,in which case,,the mold will shrink slightly..And,,it is very hard to take a mold off a thin plastic item,,or,,as I call it,,a ''street weight'' fiber item..They need to be braced well,,and build the mold slowly,,a couple of layers of glass at a time.. AND,,,DON'T use too much gelcoat in the mold,,as if it's too thick,,it will shrink from the mold as it dries..
For a small item,,I will make my mold about 3mm thick,,built up over a couple of days,and a week of curing..minimum..

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See, there's the reason for the question as you jumped right to taking the part that fits and making a mold of it, while my inexperience pointed me to simply using the piece that fit as the mold, making a fiberglass over lay of the part, popping it loose and then working it to finish. Your method is right, taking time to make a mold from the part, built up slowly and maybe even sticking on some ribs for bracing it straight, and then being able to make multiple identical parts out of that mold with a gel goat finish, too.

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Originally Posted by pat mccarthy

done more fixes with polyester it worked . cost as not has much as the epoxy but it has its place . over the years working with smc i used siwss polyester gell for smc for the big semi flip fronts ends re built many with the gell . many times i was the guy that took the part raw and did finish work to paint with no gell coat on the air plane stuff . last time i was close to a boat repair i did not even work on the damn thing i started getting cold and breaking out.i found out the epoxy i can not be in the same shop with epoxy dust. most repair job were someone did not do a good fix were guys think slopping on to much resin with no mat or cloth

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Thankfully,Pat,,the only boat repairs I've had anything to do with,,are polyester layups,,and not GOP,with epoxy..In fact,,i do very little in the boat side of things..We have enough boat repairers in the area to take care of them.. I have a problem with people who come to me,wanting me to fix their broken junk,,and expecting me to do it for very little,,and the parts have been damaged and repaired badly in the past,,and can't see that it usually means more work,,by going down deep in the repair,,and starting with a clean slate,,so to speak,,instead of just slapping more junk on top..

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Originally Posted by rspears

See, there's the reason for the question as you jumped right to taking the part that fits and making a mold of it, while my inexperience pointed me to simply using the piece that fit as the mold, making a fiberglass over lay of the part, popping it loose and then working it to finish. Your method is right, taking time to make a mold from the part, built up slowly and maybe even sticking on some ribs for bracing it straight, and then being able to make multiple identical parts out of that mold with a gel goat finish, too.

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I usually look at a mold,as an ongoing item,Roger,unless it's a strictly one off,,which will then only get the minimum requirements.. All my molds are about 5mm thick,,for the auto parts,,coremat on any flat surfaces,in the last few layers,,that is,,under the top layer of glass,,and a piece of 1/4inch mild steel rod around the edges of the mold,to keep the shape.. Over the last ten years,,the molds we bought,have had a check over for fit,etc,,and usually a new part has been developed,,prepped,,painted,,and molded..Our T bucket mold has had 33 bodies out of it now,and requires minimum maintenance..

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Originally Posted by lamin8r

Thankfully,Pat,,the only boat repairs I've had anything to do with,,are polyester layups,,and not GOP,with epoxy..In fact,,i do very little in the boat side of things..We have enough boat repairers in the area to take care of them.. I have a problem with people who come to me,wanting me to fix their broken junk,,and expecting me to do it for very little,,and the parts have been damaged and repaired badly in the past,,and can't see that it usually means more work,,by going down deep in the repair,,and starting with a clean slate,,so to speak,,instead of just slapping more junk on top..

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when i was at the boat yard i never did any glass work. the glass shop was at the very end of the boat yard them guys would do the small fix were the boat was many times i was working on the boat to .seen them fix some nasty stuff we drop off boats many times for fixing in glass shop .i knew i lost brain cell s in that place. i think they kill flys with MEK . jon did the air plane a cars and race boats so the boats were wood then with cloth over the wood so the glass was not flying around the shop less it was a fix were you had to get to the wood and strip back paint for good bond with 8inch pad

MEK was band from our plant. They used it as a solvent for inks. when they used it they had to have a in plant fireman and truck at the job. realy bad stuff. Right up there with Triclorethyline .

AT THE AIR LINE S back in the 60s we used tri clor for washing parts---solvent tanks everywhere in the shop and hangers

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Originally Posted by cffisher

MEK was band from our plant. They used it as a solvent for inks. when they used it they had to have a in plant fireman and truck at the job. realy bad stuff. Right up there with Triclorethyline .

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yep love the smell of all of it to a point its right up there with nitro. and good race fuel that de icer for them planes sounds lke hot stuff must be alot of hot land /ground water by some of them air ports

MEK melted my plastic lid before I could apply the cloth or resin. Keep this up and I'll try painting next.........

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Originally Posted by jerry clayton

AT THE AIR LINE S back in the 60s we used tri clor for washing parts---solvent tanks everywhere in the shop and hangers

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McDonnell Douglas used it to clean interior panels and just about everything else until, 69, I believe, when some idiot dropped a smoldering rag behind the aft galley in a DC 8 that was ready for delivery. That caused quite a fire that delayed delivery for 6 months or so. That crap will turn your skin white, nasty stuff.

DC 8s were pretty much done about then---DC 10 and B747 and Convair 990 were becoming biggies with the B737 coming along in late 1968? I was in class on 37 in March 69 and a lot of the upper training people and flight management dept were starting to do dc10 and 47 stuff-----


I remember when I was still a ground mech working on a electrical problem in the dash of a food truck and got to feeling woosy---there was a open bucket/and rags under the drivers seat of tri clor-------

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Originally Posted by NTFDAY

McDonnell Douglas used it to clean interior panels and just about everything else until, 69, I believe, when some idiot dropped a smoldering rag behind the aft galley in a DC 8 that was ready for delivery. That caused quite a fire that delayed delivery for 6 months or so. That crap will turn your skin white, nasty stuff.

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older engine builder i know said all good carb guys died young from working in the stuff it a liver killer .:cool: eats the ozone .but smelled great and did a good job . my dad love to tell me storys when mom was not around . he went in the Army that or jail . he love to out run the cops with is 50 chevy 4 door with red ram in it . well ran out of gas sat on the hood till they found him . Army was a good deal for him.he need teeth and went to the doc as well . he was abit of a smart ass in a nice way. told the doc that when he was work in the parts washer cleaning parts . he would break out . doc told him i can cure you. all is i need abit of what makes you break out .doc told him i put some on this band aid stick it on you . before long you be fine next time dad shows up with a can of the stuff handed it to the doc sprayed on the band aid and it melted in this hands . doc said what the hell is this stuff

Fiberglass is great stuff! Whatever you can dream up is possible!!!

Attachment 61602

Here is one of my projects from many years ago, which was intended to be marketed. Unfortunately, the bike market shifted unexpectedly before we got to market with it. The molds and some parts are for sale from my partner in the effort.

I've mocked up masters, built molds, hand laid car bodies, body parts, and done a ton of Corvette repairs and customizing, bike parts, and drag car work.

I would like to help, but my deep involvement slowed way down about 20 years ago. I am just not familiar with the chemical products available today. :-( If it is anything like paint products, they have changed radically... and not for the better.

Probably the best I can do would be to share some ideas for mocking things up. One thing I used to use was 1/4 inch hardware cloth. I used to buy it at Ace Hardware. It is like a stiff screen that could be cut and wired together, then wet cloth or mat laid over it. After you build up enough strength, the mesh can be pulled away from the inside, and the outer surface finished by skim coating with filler and block sanding. That technique, combined with finding some suitable shapes to add compound curves, could be used for almost anything.

Another thing I used regularly was a spray product that acted as a mold release. That kept the new glass from sticking to the old.

If I see something I can offer solid advise on, I'll jump in.

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Originally Posted by HOTRODPAINT

Fiberglass is great stuff! Whatever you can dream up is possible!!!

Attachment 61602

Here is one of my projects from many years ago, which was intended to be marketed. Unfortunately, the bike market shifted unexpectedly before we got to market with it. The molds and some parts are for sale from my partner in the effort.

I've mocked up masters, built molds, hand laid car bodies, body parts, and done a ton of Corvette repairs and customizing, bike parts, and drag car work.

I would like to help, but my deep involvement slowed way down about 20 years ago. I am just not familiar with the chemical products available today. :-( If it is anything like paint products, they have changed radically... and not for the better.

Probably the best I can do would be to share some ideas for mocking things up. One thing I used to use was 1/4 inch hardware cloth. I used to buy it at Ace Hardware. It is like a stiff screen that could be cut and wired together, then wet cloth or mat laid over it. After you build up enough strength, the mesh can be pulled away from the inside, and the outer surface finished by skim coating with filler and block sanding. That technique, combined with finding some suitable shapes to add compound curves, could be used for almost anything.

Another thing I used regularly was a spray product that acted as a mold release. That kept the new glass from sticking to the old.

If I see something I can offer solid advise on, I'll jump in.

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It is an awesome product,HRP..I enjoy my job,,even if it is a dirty job.. I use a mold release on a regular basis..I only wax my molds about every third pull of the product,,but spray two light coats on the mold each time I use them..

With race car body stuff plus go karts---


long time ago--used hardware cloth, plaster lathes, etc to build substructure then plaster of paris to which would file sand into shape desired, then make a heavy stiff mold over that, then make the lighter race car part(think dragster front body work)


Also have used lots of Styrofoam? for wing shapes---cut a couple pieces of plywood into wing profile and then use a wire with electricity for heat to guide over profile pieces to cut the foam to wing shape----then wrap the foam with waxed freezer paper and lay cloth (Kevlar,glass,carbon fiber)


Also for floor panel type stuff over transmissions, etc, I use the sponge egg crate type foam rubber packing material that comes in the Pro Charger kits to lay over trans and then freezer paper then glass cloth/mat/cloth

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Originally Posted by rspears

....I'm posing a question to the guys out there who have been working glass through the years, and who know what's right and what's not without having to ask anyone for suggestions..... Any true Glass Master's out there who are willing to share? Looking for some good, step by step ideas on how to do the work and thinking it might save some of us some grief as time goes by.

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.....well it seemed like a good idea. :HMMM:;):LOL::LOL::LOL::LOL::LOL:

There's a decent amount of info at fibreglast. They mention that the preferred thickness for gel coat is .010 to .020 inch. If the gelcoat is no thicker than that and has some pinholes, sanding the area down to the base fiberglass is easy, but you may find more pinholes in the base fiberglass. Polyester glazing putty is sufficient to fill pinholes for a car body, but not a boat hull.

There are some videos too. There's some info on various fillers that are used to repair boats. One mentions using a lightweight filler, to a thickness of up to 1/4 inch. They have other reinforced fillers for deeper fills.

Gel Coat Troubleshooting Guide | Learning Center

Fillers for Resins and Composites in Stock | Fibre Glast

Books & Videos for Fiberglass & Composite Material DIY | Fibre Glast

I'm fighting a unique problem with my body. The gel coat thickness is OK in most places, except on many external corners of the body, that were internal corners in the mold. The gel coat apparently ran into the low areas and pooled to a thickness of up to 1/4 inch in the internal corners. The gel coat is full of bubbles and must be removed to avoid future paint problems. I've even found areas where the thick gel coat is not bonded to the base fiberglass.

I've removed the gel coat, and feathered out the repair area with a 36 grit disc or 60 grit sandpaper. Since the body is not lacking is layup thickness, I use fiberglass reinforced filler to make the repair.

I have only found a few spots where the layup thickness of the body is lacking. Most are around the rolled-under edges of the fenders or the fender mounting flanges. If I find a thin area, I've sanded the back side and built up the thickness with matt and resin.

FWIW, if I find a slight wave or mismatch at a mold line that needs a shallow fill, I just scuff the area with 60 grit and use any good polyester filler. I see no need to remove the gel coat because filler always has to feather out onto the gel coat. The bond between the gel coat and base fiberglass should be every bit as good as you'd get between the filler and the base fiberglass, so I see no purpose in removing a large area of gel coat, where a thin layer of bondo is applied.

I'm scuffing my entire body with 80 grit and applying several coats of Evercoat G2 featherfill, a high build polyester primer, after all of the bondo work is done. More sanding follows that. In the end, I want the whole body to have a decent layer of polyester primer.

Evercoat

Dave,,the reason why the gelcoat is not stuck to the glass layup,,is usually because it(the lay up) hasn't been rolled into the corners,,or any one area properly.. If the gelcoat has been sprayed into the mold,,it is quite often the case,that it's hard to get the spraygun into the area to get the gelcoat into the mold..I usually follow up with a brush,to even it out in those cases..can't do much about it sometimes.. As I said elsewhere,,if the glass isn't rolled into the mold properly,,this is what happens..

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Originally Posted by lamin8r

Dave,,the reason why the gelcoat is not stuck to the glass layup,,is usually because it(the lay up) hasn't been rolled into the corners,,or any one area properly.. If the gelcoat has been sprayed into the mold,,it is quite often the case,that it's hard to get the spraygun into the area to get the gelcoat into the mold..I usually follow up with a brush,to even it out in those cases..can't do much about it sometimes.. As I said elsewhere,,if the glass isn't rolled into the mold properly,,this is what happens..

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I've seen that in a couple of places, where my fenders have a rolled-under edge. Even found some dry fiberglass in a spot on one rear fender - it never saw any resin. What irritated me is that the gel coat was falling off in that area and the seller didn't both to fix it before sending me the body. That fender also had a small crack where the layup was real thin. Probably cracked it when it was removed from the mold. I ground all the way through that crack from the outside and feathered it out with a 36 grit disc on both sides before applying mat and resin.

My build log has some pictures of the first fiberglass console that I received, that had gel coat that was probably 3/8" thick. That console was not useable and was replaced for free. All of the other repairs were on my time.

http://i1282.photobucket.com/albums/...psfb2fed83.jpg