Please QC my flberglassing process (steps)

Anything goes in the world of fiberglass and plastic



Non-Lurker
Posts: 2
Joined: Sun Jan 23, 2022 6:47 pm

Country:
Australia
PostPosted: Sun Jan 23, 2022 8:48 pm
Hi all,

I'm beginning a fiberglassing project repair on my Lotus Elise body.

Went to a fiberglass specialist store and bought some parts along with gleaming what knowledge I could from them. Other than that, I've been cramming youtube vids and other articles.

Just wanted to talk out what I've narrowed down here as a mental exercise before I start (along with a couple of questions) to get some feedback.

Supplies I have for the job:

1. Chopped mat, Power Mat, Cloth fiberglass.
2. Epoxy resin w/ hardner
3. Acetone for cleaning
4. Cordless random orbital sander, my hands :lol: , 80 grit, 120 grit sanpaper.
5. Primer
6. Brushes
7. Mixing cups

Supplies I might need to get?

1. filler (which kind, how many, and should one of them be a fiberglass mixed filler?)

I've got some cracks in my body work, front and rear corner on one side that's starting to spiderweb a bit over time:

Image

Image

Image

Image


From what I gather when speaking to the fiberglass shop, they mentioned on the back of the panels I'll use one layer of chopped mat as a base, then add layers of the power mat on top of that as the actual support.

For the cracks, am I cutting my mat pieces from large to small? I.e. I cut the first chopped mat to cover more than just the crack and I cut the powder mat after to be narrower and narrower until it just covers the crack?

How do I know how many layers I need to put down, is it just enough to match the thickness of the existing panel?

The fiberglass shop also mentioned to lay the top of each crack (like the one below), on the panel facing outward, with cloth fiberglass. After that to fill it with a filler and sand it down.

Image

Image


I mentioned that to another paint/body supply shop and the painter there said it was bad info, that the cloth fiber would show up during painting no matter how much I sanded it. They mentioned I should only be using a fiberglass mixed resin for the cracks on top of the body work.

Which one should I follow for fixing the cosmetic cracks on top of the bodywork? Bit confused on this one....

There's a couple of seams where the fiberglass was bonded from factory, different parts bonded together. There's been clean split (like in the image below) and I'm assuming I'll just try to sand in between and get epoxy in there and clamp it to set.

Would that be the way to do it? Is there a special epoxy you'd recommend?

Image


When everything's been fix, I'm not expecting to sand or do anything to the repairs on the underbody. They're out of sight and it's purely cosmetic to address it (right?). For the filler/fiberglass on the outerbody, I'll be sanding it with my random orbital sander and hand sanding, 80 grit to cut it down and some 1XX grit to clean it up?

Once that's done I'll just spray some primer over the repaired areas to protect them till it's time to paint. I won't have a paint booth available to me till a couple of weeks after repairs.

Does this process sound right, am I missing anything?

I was originally going to have a shop do it locally, but it's been such a f$^#fest dealing with most of them that I decided just to do it myself. The pros for me are that I can do it again if I get into an accident on track (where this existing damage is from) where insurance won't cover. Other than that I just like working on cars and developing new skills.

TIA



Fully Engaged
Posts: 408
Joined: Fri Feb 03, 2017 7:36 am

Country:
USA
PostPosted: Mon Jan 24, 2022 8:26 am
There may be others who have exclusive fiberglass experience here, to give you more detailed advice, but I've been repairing and even making fiberglass parts on and off, for years.

Just the highlights I read:
First, I believe chopped matte is not compatible with epoxy resin. Cloth is. Something about the binder in the chopped stuff not letting epoxy wet out with it. You may have to use the cheaper polyester resin, with the matte.
You have the right idea about opening up a crack, gradually feathering it into the untouched area around it. And yes, you start with thin pieces, and gradually get bigger to cover more area as you go outward, until it's just about level with the surface.
BUT, when you do a repair, you want the cloth (not sure what 'power matt' is) on the INSIDE of the repair, with the chopped matte being the last layers, closest to the surface. This way it covers the texture of the cloth, so it doesn't 'witness' up into your final surface.
I'd add some sort of grinder to the list. A random orbit doesn't have the cutting power you need to knock down a high mound of fiberglass. Or cut a good bevel in the surface to be repaired. I use a 4 1/2" grinder with flap discs. You can also use an angle die grinder with a 3" back-up and 40 grit discs. Use the random orbit, with some 80 and 180 grit to do final feathering and sanding on the repair.
You can work the front, or back first, but I prefer to do the back, so I have more idea of the final surface of the front. DO the repairs the same way, bevel the crack, gradually opening up the area as you go outward. When I do one side, I let cure overnight, then do the other, being sure I grind through the topside to reach the repair on the back, eliminating the cracked area completely. On the back side, you can just use the cloth, unless it's seen, and you want a smooth surface there, as well. The do the repair, just like the front, with matte as a final layer or 2, or 3.
Tip: the chopped matte can be split in half, thickness-wise, for a thinner piece to fill in slight low spots. It's also more flexible, for tight curves.
When finishing my cloth/matte repair, if the surface is more than 1/8" that needs to be filled, I mix up the same resin I used, with some finely chopped strand, or glass sphere filler, to make a stronger body filler. If the repair is less than 1/8", regular body filler will do.

User avatar

Board Moderator
Posts: 6208
Joined: Tue Feb 24, 2004 7:00 pm
Location: central Ohio
Country:
USA
PostPosted: Mon Jan 24, 2022 9:59 am
It's just not the good ol' days anymore. Most of the information needed for working on these newer plastics is considered "proprietary" information by the manufacturers. So I keep seeing the word "fiberglass" here which is not correct for what you have.... Your car is made of SMC which is probably why the body shop supplier has you doing epoxy as a resin. SMC stands for Sheet Molded Compound which have even further evolved into Sheet Molded COMPOSITES. Chopolds hit a major factor here concerning that when he said that mat won't work with epoxy. Here in the US I buy a special universal mat that is designed to work with both epoxy and polyester resins. Ohh, and don't even think about using a polyester resin anywhere on this thing, totally not compatible with SMC. Wondering about your Power Mat as well. That could be some kind of carbon fiber backer, but hell, I don't know.
Best advice? STOP...... Get online with a couple of Lotus Forums and try to identify the guys, companies, that are doing successful work with their cars. See if you can find any exploded diagrams of the "plastics layout" on your car. I use to get these years ago on the old Pointiac Fieros so I knew how to identify and repair the 5 different plastics that were in use. If you could find a local Lotus body shop visit them and see what they are saying about how their repairs are done. I talk to people all the time about how I do exotic wood repairs, knowing full well that when most people know what "must" be done about 80% of the time I get the work anyway..... By the way, always been a big Lotus fan....just could never fit in them, ha, ha....... Tried to shoehorn my way into an Europa when I was a teenager.... no way.....
Last edited by DarrelK on Mon Jan 24, 2022 10:38 am, edited 1 time in total.
Reason: spelling
Metal, wood, fiberglass, we work it all... www.furniturephysicians.com We can restore the irreplaceable!



Top Contributor
Posts: 5542
Joined: Tue Sep 16, 2008 1:17 pm
Location: Pahrump NV.
Country:
USA
PostPosted: Mon Jan 24, 2022 1:18 pm
Ditto what Both these guys are saying!

You cant fix that with regular store bought fiberglass stuff!

You need a Print out of what each panel is made from (It could also be identified on back side of panel?)
I say a Print out because in my Factory Chevy manual for my Corvette it has an entire section just to Identify each Major autobody sections panel material for repairs to be made.
In my Case my car has like 5 or 6 different types of Plastic and SMC type materials.
Just in the major assemblies.

Their are special materials for the repair of all these different types of parts plastic and Fiberglass look alike parts of cars today. gone are yesterdays polyester fiberglass dune buggy or what ever, todays Auto panel parts today are very specialized which are made from some very special light weight materials. These different types of materials require special compounds and Glues in order to repair them. gone are the days of just grabbing random repair materials.



Best page I have seen yet
https://www.polyvance.com/identify.php

I visited a couple Lotus web forums lots of others are just using regular fiberglass?
no explanations on resigns used.
Dennis Barnett
A&P Mechanic, FCC General radio Telephone Operator
Line Maintenance A&P Mechanic and MOC Tech specialist.



Non-Lurker
Posts: 2
Joined: Sun Jan 23, 2022 6:47 pm

Country:
Australia
PostPosted: Mon Jan 24, 2022 6:57 pm
Thanks for the advice so far guys.

Sorry for the typo about the "power matt" what I actually meant to say is "powder mat". Here's the supplies I'm using as recommended from the composite repair shop/store I bought them from:

Chopped Mat - I think the shop recommended this as the first layer on the back since it would mold and contour much better to the shape/cracks/etc. of the body.

Image


Powder Mat - I looks like a weave/cloth texture, but it has a powdering feel to it when touched. The shop called it "Powder Mat" and recommended using this to build layers for structural strength on top of Chopped Mat (the base/first layer).

Image


Cloth/Surfboard Cloth - The shop called this one surfboard cloth for some reason (maybe they use it to fix surfboards?) and said it was a light layer that I would use on top of the bodywork. The previous layers would be on the underside (the actual structural repair) and the cloth would be used on the top (directly over those underside repairs) to address the cosmetic cracks. They mentioned it would be flexible and allow top to move/prevent recracking.

Image


Epoxy Resin - The one they sold me. The mentioned the first two mats would be a 2:1 ratio (being quite thirsty) and the cloth would be a 1:1.

Image


As for the Lotus forums, I've read and ask there too. Good bunch of guys but information is all over the place.

Here's my post:
https://www.lotustalk.com/threads/fiberglass-repair-process-qc-me-please.487465/

Here's the top result for repairs on there (with guys arguing with each other about method on the second page):

https://www.lotustalk.com/threads/diy-fiberglass-repair.459488/#post-5871824

There's a couple of guys who have fixed their Lotus locally but they've just gone to Bunnings (like Lowes in Australia) and bought a generic off-the-shelf fiberglass repair kit.

Here's a video of a guy who does alot of Lotus repairs and says he's followed what Lotus do, which is to do a repair on the back (he doesn't mention fiberglass material) and then bond a piece of metal on top of the repair for structural rigidity, say that it's exactly what Lotus does :|

https://www.youtube.com/watch?v=4d9KxTfPi3M

It's a bit information overload at this point, so I'm happy to find a (this) forum focused just on autobody to hopefully cut through some of the mud :lol:

User avatar

Board Moderator
Posts: 6208
Joined: Tue Feb 24, 2004 7:00 pm
Location: central Ohio
Country:
USA
PostPosted: Tue Jan 25, 2022 12:17 am
All, I can say is WOW....information and obviously a lot of misinformation is available everywhere concerning this partiular model. Hey, we have a fellow countryman of yours NFT5 that might be able to shed more light on "how" this should be done and more importantly what the correct materials are for this car. And, using aluminum to repair a laminated plastic composite????.....that is a new one on me. I don't even understand the physics of how that would be a long term stable repair..... I'm going to hit Chris (NFT5) with a PM and see if he can help you with this.....
Metal, wood, fiberglass, we work it all... www.furniturephysicians.com We can restore the irreplaceable!

User avatar

Top Contributor
Posts: 2031
Joined: Sun Dec 16, 2012 4:46 am
Location: Canberra
Country:
Australia
PostPosted: Tue Jan 25, 2022 1:04 am
Got the message but not on PC now. Will respond in more detail later tonight.
Chris

User avatar

Top Contributor
Posts: 2031
Joined: Sun Dec 16, 2012 4:46 am
Location: Canberra
Country:
Australia
PostPosted: Thu Jan 27, 2022 4:19 pm
Well, thanks to my 3rd Covid shot, been off the air for a bit longer than I thought.

My experience is more with boats, but as I was racing at the time the competitiveness meant that we tended to consider right of way enforceable with fibreglass and in the later years boats were made more of composites than just straight fibreglass. That said, really major damage was rare and sent away rather than fixed ourselves.

Chopolds has detailed the basic procedures that I used. Remove as much of the damaged/cracked area as you can, from the back, Then start laying in mat, wetting out completely but not building too much thickness with the epoxy. BTW, the one you have is fine and I wouldn't do other than very small spot repairs with polyester resin, which I only ever used for hydrodynamic shaping of rudders and such. Chopped strand mat first, couple of layers, followed by woven mat, two layers laid at 45 degree angles, then one or two layers of chopped strand again. I'm not familiar with the "powder mat" but see that it could be used instead of the second chopped strand layer. Every layer must extend further than the previous one and, of course, preparation must be good - coarse sanding down to glass or original composite. If the back is going to be visible then you need to be careful, but a bit of a lump is kind of unavoidable. Gelcoat can be used to smooth out.

At the front, open up the damage and feather the edges, then lay in small pieces of chopped strand mat, building up to the desired level, or a little higher then sand smooth. Your repair then should have like a squashed _X_ shape (if viewed from the side), bonding top and bottom to the original.

Thin strips of metal (say 10mm x 60-70mm) can be used for increased structural strength, but I've always put them at the back, after first layer of glass. You can buy them pre-cut (used for plastic repair), or just use whatever you have available - raid the recycle bin for a tin can and cut to size. Rough the surfaces up with 40G - you want maximum bond.

Except for the spot where you have an obvious hole, I'd be checking that the cracks aren't just in the surface (paint/filler) layers, in which case you can just bog and prime.

Alternative is to take it to a boat repair joint that has experience with composites. Much more expensive but they'll do a good job. Very few car repair places have much experience with fibreglass, unless manufacturer specific and for those you'll need to win Lotto first, which you can't do until I've had my turn.
Chris

Return to Fiberglass and Plastic

Who is online

Users browsing this forum: No registered users and 11 guests