Some fibreglass repair questions I need answering

[Luke]

Hello all,

I am getting ready to order the various bits required for a complete strip and repair of my 66 S3 Elan FHC body. I have plenty of experience with composites but unfortunately it was aerospace work using vac bags and autoclaves so I still have some questions I need answering by you guys with specific knowledge of the Elan and air-cure gfrp. I have searched but haven't found the answers anywhere else.

1. What areas should be reinforced? There are a few stress cracks that will be getting attention but I can only guess where else it may be required.

2. Does anyone treat the reverse side of the body, in the interior, engine bay etc. with anything? I thought about applying something to prevent osmosis but then I may trap moisture that is already in the laminate.

3. What material should be used on the outer layers of a repair, normal mat, lighter weight mat, tissue/veil? I want to ensure it is not possible to see a difference through the paint when compared to the adjacent gel coat, note that I will be doing a final full tissue layer.

4. Should filler be skimmed over a repair prior to the tissue layer? Option 1 does not do this.

5. How thick or how many plys should a tissue layer be? Option 1 says they "laminated with a mix of resin and gel coat to the ENTIRE exterior of the shell and panels. It is then hand sanded to a thickness of 1.0 and 1.5 mm"

Thanks in advance

[nmauduit]

Hello,

this is no advice (esp. as you're probably plenty qualified to figure out what is good for your car), just sharing opinions so here is what I would do on my car :

1) check the trunk/boot hinge area, esp. at the hinges, and if appropriate reinforce with a beam type structure (still flexible but no so much as to allow for cracks when opening/locking the trunk opened) - I do that with a shaped aluminium profile hidden behind the water gutter, a steel equivalent may have been done in period on later cars.

2) I don't, but am extra careful of quality sealer on the outside prior to spray filler and quality paint

3) just like you say, the workshop manual describes that well (margin required to take out cracks extension, tapering the top and bottom surface so that the patches do not create a stress point because of a different thickness from the original material etc)

4) I use no putty, brings the body within a few 1/10mm at the most of proper shape with fiberglass work (that is where gelcoat had to be removed for repairs) then use spray filler

5) I don't get that (esp. short of a detailed evaluation of the body and areas to be repaired) : for a restoration I aim at bringing the thickness of the repaired area back to original thickness. imho a veil over the entire car as a one stop for a completely ruined gelcoat is a "quick fix", the durability of which will be heavily dependent of the underlying fiberglass (do cracks extend into the body, how deep, have they all been repaired...) and future car use: if the outside layer has unrepaired cracks that make the body more flexible there, cracks will reappear as soon as the car will be put under stress (may never happen if the car is kept in a garage and only driven slow to gatherings or weddings every now and then).

[alan.barker]

I only finish with tissue/Veil no filler but it takes longer.
This is a very personal choice but when i have used filler in the past there has always been shrinkage and possible to see previous repaires.
Imho Option 1 is the good way to go.
Alan

[h20hamelan]

Member here Mrdoow did some excellent work. He is from the same occupation as you. He was a body off, bagging Kevlar/Epoxy (not Vinyl-ester) to the underside.

There are many of good repair threads here.

I am very glad I ran spider web style strips on the floor 2” mat/cloth, not sure if Poly-ester was correct. I also reinforced corners of floor paying attention to bobbin areas, and corners where jacking or hoisting may take place.

When/if the body comes off, I will address a few areas from the underside. Bagged or not?

One thing about driving, with 3oz of chop strand glass between occupants and debris on the road. For me, it is far too weak. Medoow used Kevlar for this reason.

Also, I Dremel (die ground) followed the stress cracks. Applied Poly, then sanded. Humidity below 50 for a few weeks. Re-Face coat, then epoxy primer and paint. Seems good, almost a year later. No bubbles, no cracks...

[Luke]

Hello,
this is no advice (esp. as you're probably plenty qualified to figure out what is good for your car), just sharing opinions so here is what I would do on my car :

Thanks for the detailed reply, I feel I may need to start a new thread just for body modifications and reinforcements as there's a lot to talk about! The tissue layer is not to hide anything, I will be doing full and proper repairs to the whole body and then adding the tissue over the top (possibly in epoxy), this should stop any new gel coat issues appearing and hopefully keep the body in a great condition for years to come.

I only finish with tissue/Veil no filler but it takes longer.
This is a very personal choice but when i have used filler in the past there has always been shrinkage and possible to see previous repaires.
Imho Option 1 is the good way to go.
Alan

I very much like to do things once and do them right, it seems like spending the time and not using filler is the way to go. I will definitely be using option 1 for the paint.

I am very glad I ran spider web style strips on the floor 2” mat/cloth, not sure if Poly-ester was correct. I also reinforced corners of floor paying attention to bobbin areas, and corners where jacking or hoisting may take place.

Can you please expand a bit on what you mean by spider web style strips on the floor? Kevlar in the footwell and floor is an interesting idea...

[h20hamelan]

2” strips, crossing from corner to corner. Some side to side. I probably used woven roving strands here and there. My idea was simply to reinforce the floor. Without destroying the lightness of the car. Also, that running over an object on the road. The object hopefully would not make its way into the cabin.

And I believe, Kevlar is to be used with vinyl-ester. Or you loose the elastomeric properties attributed to Kevlar.
Though, even some of my Vinyl/Kevlar down river racers/squirt kayaks and tripping canoes have cracks. They fair far better than the poly or epoxy counterparts.

[h20hamelan]

Can’t recall the name for the Clark Foam (solvent resistant) ribs, with bonded fibres. For your structure areas. You sand/file the cut sections to make your curve. Not sure if its better than metal?
I am sure you Aviation folk would just use honeycomb.
Too bad Boeing surplus is closed, or moved to Chicago. Luckily I stocked up many years ago.