Lotus Europa Community
Lotus Europa Forums => Garage => Topic started by: RonPNW on Thursday,September 05, 2024, 10:39:20 AM
-
My experience in fiberglass comes from years of repairing white water kayaks. Lots of strength and flexibility, beauty, not so much.
The Europa is unique in that all the panels are thin and flexible. Very different compared to a boat or corvette that layup thick rigid panels. I think the repair process should be different because of this.
I’m still working on major cracks (some parking lot abuse and some Lotus design flaws) and trying to get bonnets and doors to line up.
Years ago I did some repair using polyester that developed cracks around the repair. I’m sanding those out and replacing with epoxy. Current epoxy products claim to stick better to polyester, stay flexible and are stronger. I’m finding interior / unpainted panels are fuzzy with exposed fiberglass fibers. Many of the visible paint cracks are only in the paint. That is when you sand to the fiberglass body (and often only to the primer layer) the crack is gone. So here I my process using epoxy resin (Tap Plastics) and woven cloth for the interior and mat for the exterior (the weave of the woven cloth will show through the paint but it is stronger and easier to squeegee out excess resin). The attached picture shows cracks in paint that disappear at the primer layer.
I’m trying to repair any actual cracks from both the front and back side. The usual drill of sanding to a clean solid surface and a few layers of cloth in a tapered stack. Squeegee the repair to remove excess resin to prevent making the repair too stiff.
Reinforce the weak areas in the original build including the rood, roof pillars, wheel arches, rear bonnet hinge area, rear bonnet rear panel and a few others that will show up when sanding off the paint.
I mixed up an epoxy filler (less than 1/16 thick, for the bad areas) using micro-ballons and epoxy resin. It sticks very well, is light weight, stays flexible and becomes inert once cured, but is a serious pain to sand. A few areas needed a layer of thin matt (veil) to bring panels into alignment.
I’m nearly done with major repairs and rework and need helps on the next steps.
Questions:
What are people using as a final thin filler before primer? It seems that most fillers dry hard and brittle. A likely cause of new cracks. I would like to stay with epoxy which stays flexible (at least the one I’m using does).
I’m thinking a high build epoxy primer. The only one that is easily found is Eastwood. Are Eastwood products worth it? I’m sure it’s someone else, rebranded but I don’t know who.
What has worked for primer, paint coat, clear coat (should I have a clear coat?). It seems most paints assume a stiff panel and are not flexible. Are there a more flexible products available?
Thanx
Ron
-
I started repairing with epoxy until I found that polyester cannot be used over epoxy as it will not cure. I did the same as you though, mixing my own fillers. Milled fiber, microballons, and cabosil. I used straight milled fiber and polyester to fix door gaps and ground out spider cracks.
I used a black epoxy primer over everything then sprayed a 2k sandable gray primer over that.
I did single stage paint on this and will never do that again. Base/clear is better. Easier to add thickness with clear and you can remove runs without discoloration.
-
A guy trued up all the sloppy fitting parts of a Europa body. Maybe this will be helpful to you (https://www.lotuscorps.org/wp/truing-up-the-body-fit-on-a-1973-lotus-europa-part-1/).
-
My painter used this stuff: https://u-pol.com/en-us/product/coatings/specialty-coatings/reface-2k-polyester-spray-putty/ (https://u-pol.com/en-us/product/coatings/specialty-coatings/reface-2k-polyester-spray-putty/)
When I checked in at that stage, the stuff appeared to sand very nicely, very smooth.
-
My painter used this stuff: https://u-pol.com/en-us/product/coatings/specialty-coatings/reface-2k-polyester-spray-putty/ (https://u-pol.com/en-us/product/coatings/specialty-coatings/reface-2k-polyester-spray-putty/)
When I checked in at that stage, the stuff appeared to sand very nicely, very smooth.
Yep, I've used Reface on both the Elan & Europa. Very thick to spray, looks awful going on but settles down nicely. Dry sand to remove any obvious dust, etc, and then prime with 2-pack is the way I would go again.
-
Many of the visible paint cracks are only in the paint. That is when you sand to the fiberglass body (and often only to the primer layer) the crack is gone.
In your pic, apart from the broken corner, the cracks in the paint radiate from that damage. I wouldn't be assuming they aren't part of the same event.
It may well be that sanding has mostly removed surface cracks under the paint, but the sanding also tends to hide the little ones, too. Me? . . I wouldn't take the chance. But I like the method - doing the repairs with the paint initially intact so you can see the issues clearly.
I had my body sand blasted which is a great way of avoiding the mind numbing time soak associated with sanding the whole thing. It also means I might miss a few little surface cracks but it'll be covered with veil which should ameliorate that.
I stuck with polyester and chopped strand mat for compatibility reasons. Kitty hair is also marvellous stuff.
I don't think anyone would argue about the strength of epoxy but if the repairs are done properly, it's unnecessary, I reckon.
That said, Fort might chime in and point out anything I missed! :D
-
I use upol 2251, It's been replaced by up2253. The reface seems fine also but i wonder why cleanup is acetone and not a lacquer thinner. It doesn't seem to have any other colors than gray whereas 2253 has 4 shades plus black. :D
I stay away from epoxy, to each there own. Veils are good and as soon as the humidity goes away down here in Florida I have a few panels to test.
Dakazman.
-
I use upol 2251, It's been replaced by up2253. The reface seems fine also but i wonder why cleanup is acetone and not a lacquer thinner. It doesn't seem to have any other colors than gray whereas 2253 has 4 shades plus black. :D
I stay away from epoxy, to each there own. Veils are good and as soon as the humidity goes away down here in Florida I have a few panels to test.
Dakazman.
I do have acetone in the workshop but for the Reface I've only ever used the cheapest cellulose thinners to clean the gun afterwards. I vaguely recall you can use acetone to thin it but I don't, just use a large jet size, gravity gun & adjust pressure until it works. (high tech, that's me)
As for epoxy resins, ditto, I don't use them either. I know they are stronger but don't see the logic in mixing resins, at least when it's all the same stuff you should get the same expansion/contraction/flexing/etc.
Brian
-
As for epoxy resins, ditto, I don't use them either. I know they are stronger but don't see the logic in mixing resins, at least when it's all the same stuff you should get the same expansion/contraction/flexing/etc.
Brian
:I-agree:
I am on a steep learning curve and information gathering journey regarding body work but "yes" this comment makes sense to me.
-
I'm in the epoxy camp. The bottom line for me is that epoxy resins stick much better to everything, including old polyester resin, than polyester resins do. I don't plan to ever use polyester resin for repairs, so I don't worry about polyester over epoxy.
There is a huge difference between the thermal expansion coefficient (CTE) of glass and any of the polymer matrix options, so in practice the integrity of the repair depends upon an adequate fiber/resin ratio in the repair and having a good bond between old and new and between resin and fiber. Epoxy resins deliver a much stronger bond than polyester resins, so I trust them more.
For the interested, you can bond polyester to cured epoxy if you must (though preparation is critical). See here -
https://www.epoxyworks.com/index.php/polyester-gelcoat-over-epoxy/
A source for some CTE figures
https://www.engineeringtoolbox.com/linear-expansion-coefficients-d_95.html
-
I'm in the epoxy camp. The bottom line for me is that epoxy resins stick much better to everything, including old polyester resin, than polyester resins do. I don't plan to ever use polyester resin for repairs, so I don't worry about polyester over epoxy.
There is a huge difference between the thermal expansion coefficient (CTE) of glass and any of the polymer matrix options, so in practice the integrity of the repair depends upon an adequate fiber/resin ratio in the repair and having a good bond between old and new and between resin and fiber. Epoxy resins deliver a much stronger bond than polyester resins, so I trust them more.
For the interested, you can bond polyester to cured epoxy if you must (though preparation is critical). See here -
https://www.epoxyworks.com/index.php/polyester-gelcoat-over-epoxy/
A source for some CTE figures
https://www.engineeringtoolbox.com/linear-expansion-coefficients-d_95.html
Very informative Gideon.
So the repairs you do to a 1/8" panel would have a scarf cut of 6" according to the proper repair shown here. ( 1/4" Fiberglass on these cars ?)
https://www.epoxyworks.com/index.php/west-system-epoxy-vs-polyester/#more-1582
Then I read about the different shrinkage rates, I have seen Bondo to polyester and the results in the final paint clearly defined a repair, much like using fiberglass cloth.
Don't get me wrong, I agree with all the strength characteristics and durability of epoxy if laid completely over the entire panel.
Trust me, I can see every flaw I missed a year after painting. Watch the finish move with high temps, I can only imagine what small cracks filled with water look like after freezing temps hit. a repair that doesn't have the proper is surely to crack or heave.
(12:1 is the minimum bevel angle recommended for repairing cured composites.)
Dakazman
-
So the repairs you do to a 1/8" panel would have a scarf cut of 6" according to the proper repair shown here. ( 1/4" Fiberglass on these cars ?)
https://www.epoxyworks.com/index.php/west-system-epoxy-vs-polyester/#more-1582
That's not too different from the method described in the Europa workshop manual.
The 'Epoxyworks' example shows a 1/4" (6.3mm) panel and three layers of glass material used - must be pretty heavy stuff, and fair enough, too because they're talking about a boat. The Europa body is supposedly 0.093" (2.3mm) thick.
For me, a significant question arises re the proposed glass material to be used with epoxy. Obviously the common chopped strand mat is out as it's designed for polyester due to the specific binder added. Yet it is often said that CSM is OK to use with epoxy so I tend to be less persuaded about the promotion of a supposedly superior system when it accepts an inappropriate material.
But don't listen to me.
Here's a YouTube video of a hands on comparison between CSM using polyester and epoxy.
https://youtu.be/uLKiDa2dqq8?si=S3703XZXIyfGVEKr
However, when someone produces a carbon fibre body, we should all embrace epoxy as the appropriate material for those. 8)
-
Thanks for posting that video Gavin and as usual with me, "every day is a school day".
I didn't know about the differences in CSM binders before, typical me, I'd just assumed CSM was just CSM, all the same. The comparison in the video shows the different resin reactions and the guy explains it very well. You can see that yes, you can use both resin systems but there are differences in the final result and I'll admit that without a side by side comparison and his explanation I wouldn't have been able to tell one from the other seen in isolation.
Worth watching for anyone considering mixing systems.
-
.....Obviously the common chopped strand mat is out as it's designed for polyester due to the specific binder added. Yet it is often said that CSM is OK to use with epoxy so I tend to be less persuaded about the promotion of a supposedly superior system when it accepts an inappropriate material....
Sorry - you've lost me here with the above statement - (and I believe it to be of some importance in this discussion) - may I trouble you to reword it somehow so as I can better understand it. ?
-
.....Obviously the common chopped strand mat is out as it's designed for polyester due to the specific binder added. Yet it is often said that CSM is OK to use with epoxy so I tend to be less persuaded about the promotion of a supposedly superior system when it accepts an inappropriate material....
Sorry - you've lost me here with the above statement - (and I believe it to be of some importance in this discussion) - may I trouble you to reword it somehow so as I can better understand it. ?
If I've got it right, it means that CSM isn't all the same stuff. The glass component is, but when it's made they use an additive to bind the fibres into that sheet of matting - whether it's woven roving/CSM, veil, or whatever.
From the video it seems the additives used can be formulated to work better with a specific resin. The video shows how easily the polyester resin is absorbed into the CSM and results in what looks like a good composite. The epoxy resin used in the same CSM does work but it's clear that it takes more manual pressure to push it in and the resulting composite panel is heavier, has more resin weight and doesn't look as good IMO. It is worth 10 minutes of your time if this topic interests you.
There's a comment that in Europe the binder/additives are powder based and work with either resin so we should be ok in the UK. But that immediately flagged up "there's a difference in CSM which could depend on where it's sourced" which made me think that if I ever wanted to use epoxy on the car then I'd need to be careful. But I'm not likely to, I don't see the point in putting a stiff area in the middle of an otherwise comparitively weaker panel.
-
Interesting topic ???
-
Interesting topic ???
:I-agree:
If you really want to learn more visit :
https://www.fibreglast.com/category/Learning_Center
Dakazman
-
but when it's made they use an additive to bind the fibres into that sheet of matting - whether it's woven roving/CSM, veil, or whatever.
It's my understanding that woven cloth doesn't have any binders at all and relies on the fact that it's woven which kinda holds it together.
How is CSM marketed in the UK/Europe? Here in Oz, I couldn't find any CSM with the powder binding and as far as I can gather, the situation is similar in the US.
I'm just wondering if they sell both over your way or just sell the powder binder version and don't include the binder in the description at all . . . which would also be logical.
Harking back to that video, if you scout around YouTube, you'll find other videos demonstrating CSM with epoxy pointing out it's nearly impossible to work around, say, a right angle form. The glass itself kinda stays stiff, whereas with polyester resin, the CSM becomes floppy and takes to complex forms much more readily.
-
In regards to polyester & vinyl ester vs epoxy laminating resin, don't minimize the health, comfort and ease of usage factors. The styrene fumes in polyester and vinyl ester not only smell like hell but they will kill you sooner than the epoxy gases. Epoxy, while considerably stronger than the ester resins, also afford one longer kick-off times which makes it much friendlier to work with. Much less stress and if you are going to vacuum bag, you have an hour or so to work with. Set times are easily adjustable. Cloth is always a superior choice over matt for too many reasons to list. I believe that every cloth (fiberglass and carbon) that I have ever used, did not contain styrene binders. That's my two cents worth...
-
I agree with My S1.
Just don't use CSM. Use cloth or some loose chopped fibres mixed into resin. Or both. Add some peel ply and vacuum bag the repair if possible. I found some lightweight, fine weave glass cloth that would make a nice finishing layer to minimize the potential for print through
https://fiberglasswarehouse.com/collections/fiberglass-cloth/products/1-5-oz-x-50-wide-fiberglass-cloth-style-108
One youtube channel I like for demonstrating practical composites repairs and stuff is the Duracell project. In this clip he repairs the sheer clamp. It's a bit heavier duty than a Lotus bodyshell repair but some of the procedure would be similar.
https://youtu.be/NybZZF6-Gk0?t=938
-
Gideon and S1,
Do you use epoxy for spot repairs or over an entire panel? have you got a year after shot of the repair?
I'm always looking for an easier way to do the job and make it look better than OEM.
This is an ongoing discussion for our group, corvettes, boats and they can't decide. I've seen my experts set fire to some resin repairs that they were rushing. vacuum, nice repairs of aircraft structures are mandatory. We are just trying to get a professional finished look.
golden gate also states that there is no structural component to the body.
Dakazman
-
Spot repairs or an entire panel. Either way. I haven't even started on bodywork yet, let alone have a one year after photo. All my practical experience comes from fixing boats. I'm actually fixing one right now, but I guess that would be off topic.
-
Spot repairs or an entire panel. Either way. I haven't even started on bodywork yet, let alone have a one year after photo. All my practical experience comes from fixing boats. I'm actually fixing one right now, but I guess that would be off topic.
Boats :)
Been there, Lets see upstate NJ ... Lake Hapatcong ? I lived in Jersey, 30 years, which was all my life at the time.
Dakazman
-
… Regrets, I've had a few ...
Below is a pic before I knew any better - woven fibreglass cloth which printed through my then new paint job. >:(
Here's a video (approx 12 min) illustrating some common issues working with fibreglass for the uninitiated.
While the demonstration pertains to laying glass in a mould, there's plenty of info relevant to the common type of repairs on a Europa body.
https://youtu.be/ZfRBgvXRpY8?si=sWLFggk1oF-hQ5N2
The same people show how to replicate a 'EUROPA' badge in this vid (8:30 min). How cool is that!
https://youtu.be/WmDfJicrrYo?si=0u0GGnF5LXg1d7wp
-
GavinT above - what color was the paint on the car? That looks like woven cloth that is lacking in saturating resin.
-
'Twas green as per my avatar. (pic below)
Re the woven cloth . . dunno exactly. It may well have been scuffed during the extended time it's sat idle (and shipped around the country) but it is sufficiently saturated. And don't forget, the body was also sand blasted, so that may be part of it.
At the right-middle of pic you might observe an oversaturated 'lake'. It's not all that bad, but does reflect the nature of the task, i.e. applying a thin layer of material on a preexisting hard cured panel.
At the time, both anomalies were rectified during the paint prep stage and a few small furry areas don't present an issue.
But that's not the actual problem, of course. The woven cloth stopped the crack reoccurrence just fine, but it printed through worse than lycra bike shorts. This all showed up maybe a year or so later.
In my case, the cloth will be coming off, of course.
All that might explain my experimentation with thinned down resin in a quest to avoid an over saturation of the veil/tissue.
Cheers,
Gavin
-
Without going into the history of my car, I had a buddy who was in partnership in a fiberglass shop cover my car with thin cloth. According to him, he tried everything (fillers and sanding) but the cloth still printed through the paint. I imagine you could prevent the printing by covering it with veil but I don’t think cloth belongs on the exterior of a car in the first place.
-
According to him, he tried everything (fillers and sanding) but the cloth still printed through the paint. I imagine you could prevent the printing by covering it with veil but I don’t think cloth belongs on the exterior of a car in the first place.
Some years back, I heard, personally, this argument used by one of the UK's renowned automotive glass fiber specialists - he maintained that you cannot create a stable base for the various paint processes on a car without first covering,(encapsulating really), the car with veil.
In my ignorance I am hoping that glass fiber technology and more to the point, available products, have now developed and advanced to a level whereby this process can now be avoided.
-
With my car, the cloth print through came and went, to some degree. This wasn't something I watched closely or thought about much at the time; I was just annoyed. Only now since the subject has come up do I recall our own D'man who made a number of comments with respect to changes in paint surface characteristics on his car.
He was noting his car changed before your eyes (or words to that effect) and I think he said it was related to hot sunny days. His car is black, so that may exacerbate the phenomenon - dunno. D'man lives in Florida (I think) which is a similar climate to mine, so that might be something.
Perhaps the resin expands and contracts differently than the glass strands in the cloth on a hot day and it becomes more obvious because the cloth pattern is more distinct & recognisable than, say, CSM.
Hopefully, D'man might chime in.
-
The resin is also different thicknesses on the top of a cloth strand (wrong term...) versus in the valley between strands. I suspect the mat has less variation across the surface.
As an aside, while reading about surfboard building, where they used cloth, some finished with a surface layer of micro-balloons in resin, to fill in that weave. I don't know how effective it would be.
-
I am no expert on fiberglass or fiberglassing so I could be wrong or I this could be ridiculously obvious but because I'm not an expert, I can't judge that but I've always thought that a primary reason for veil is to be a resin carrier. It obviously provides some strength but holding resin seems like a main purpose and in a way makes a sort of gelcoat surface. Resin is not only among the fibers of the veil but above it and I think that layer of resin is what you actually want to end up sanding to provide a good smooth surface for your paint.
Just my thought about it...
-
Veil is intended (and used) in a mould situation to mask (diffuse) the coarse CSM underneath. The heavier weights of CSM are considerably courser so it probably makes sense in a production environment to lay down one layer of veil plus three layers of heavy CSM instead of eight layers of lighter CSM. That'd be my speculation anyway, and that veil provides some 'insurance' against print through. Also, the moulding process usually includes gelcoat as a finished surface which can be relatively thick, too.
I guess someone came up with the idea of using veil post-production and applied externally on our cars with not so much the masking objective, but of encapsulating cracks.
Needless to say, these are entirely different use cases with entirely different objectives.
So, yeah, this application of veil post-production inevitably makes it a 'resin carrier'. That's unavoidable given the viscous nature of the resin and the lightness of the veil. We end up with a resin rich layer on top. Or, to put it another way, the additional surface layer essentially creates a thicker panel but with less reinforcement.
To me, that's acceptable provided the cracks are arrested.
In practice, the next step is to prepare that newly created surface for the paint stages. To do that, we need to scuff the surface at a minimum in order to provide a key and to eliminate the wax on the surface. The question then becomes; how can that scuffing be accomplished without breaking through that poofteenth (technical term) of veil.
There's other issues like how to deal with the seam created when overlapping sections of veil. While it might be possible to cover the bonnet, doors or engine cover in perhaps two sections (probably one for the doors) that's not the case with the majority of the body.
What's actually happening here becomes a conflict of objectives; we need to perform the final shaping/scuffing of the body and yet, not break through the veil.
It's with the above in mind that I think the best practical step is to apply spray polyester filler as the base for that final shaping instead of attempting to shape at the veil stage.
But that's just my take.
-
You pretty much explained what I did: I covered the engine cover and bonnet and IIRC both doors. I didn’t have any stress cracks but I really don’t remember why I thought it was necessary. There could have been some printing from thin cloth or there was some general roughness. I used fine sandpaper on a DA orbital sander so as not to get into the fibers of the veil. I believe my final grit was 600. It seemed to work pretty well. The paint shop kept my car for what seemed like a long time. They didn’t mention any extra work they needed to do but they may have figured that into the estimate… or they may just have been jammed up.
I didn’t try to cover the cloth printing on other parts of the car so I didn’t need to worry about seams but I think if I had, I would have butted the pieces of veil and filled in the line with something - resin, micro balls, or other body filler.
So that was my amateurish method. Thanks for filling in the technical details didn’t know.
-
My first experiment with veil was covering the front trunk lid. A PO had repaired the front edge with cloth and I wanted to cover it. I used two sheets overlapping on the front/back axis, and had a hell of a time sanding down the overlap. So in future lapping applications, I cut veil to shape and picked the edges, pinching off small bits along the edge. That basically feathers the edge. So then any overlaps are practically invisible. It works for single pieces too, feathering the edges into the old surface. Using one of those rollers that look like a stack of washers also helps to push the fiberglass down to the bottom of the resin.
-
Digressing slightly but on the same subject - what is the difference, (in simple terms please), between polyester, epoxy and we now have it seems "isophthalic" resins (the later championed by Banks), and which should we be really using for localized repair works?
-
If you choose polyester resin then I believe that isophthalic is a better choice than orthophthalic. It has better mechanical properties and some other advantages, but the main practical advantage for repair work is probably that isophthalic resin shrinks less than orthophthalic. I thought this was a fair summary
https://www.ecfibreglasssupplies.co.uk/what-type-of-resin-shall-i-use
-
Well, this link says the opposite!
https://aronpolymer.com/isophthalic-vs-orthophthalic-polyester-resin-which/
But whatever the truth is, I don't think it matters much. The shrinkage issue is of interest to manufacturers of FRP moulded products that look to hold tighter tolerances.
In our application we're more concerned with patch repairs which will be sanded down anyway, so, not a problem IMHO.
-
I'm new to this but my reading indicates that the shrinkage can result in cracking at some later date. It is usually due to some temperature extreme or sitting in the sun. That is one of the reasons that all my repairs and filling is done with epoxy.
I have also read that a few coats of epoxy primer may mitigate shrinkage in layers below the primer.
To be fair, I have no direct knowledge but the info did come from one of the pro level bodywork forums.
Ron
-
Well, this link says the opposite!
https://aronpolymer.com/isophthalic-vs-orthophthalic-polyester-resin-which/
But whatever the truth is, I don't think it matters much. The shrinkage issue is of interest to manufacturers of FRP moulded products that look to hold tighter tolerances.
In our application we're more concerned with patch repairs which will be sanded down anyway, so, not a problem IMHO.
Gee, I'm confused now !
My knowledge in this area is at least 20yrs out of date. In my working life we did specify & use GRP vessels and I was fortunate to work with a couple of fabricators who also had technical bods on their payroll. So I did learn a bit about the resins they/we used and more importantly how easy/hard it was to fabricate with them. As this was the chemical industry we were more concerned with chemical & mechanical properties so we tended to use vinyl esters with a cheaper polyester resin for the external (non chemically exposed) layers to keep fab costs down.
I'll be honest and say that up to this juncture I'd have said Isophthalics were the ones for us but as to what Lotus used in the 70s, well I think that would be whatever was cheapest at the time. A car body doesn't have a lot of stress or chemical attack, it's just there to keep the rain off the driver.
Anyway I read both links and the second one appears to contradict itself unless of course I haven't had enough caffeine yet to be thinking clearly. The screenshot shows a description and from my limited knowledge, shorter chains usually means better chemical stability, stronger, heat resistance, etc. It says OPs with longer chains have lower melting points and by inference, lower heat resistance which I understand. So IPs are "better" ?
Then a paragraph later it goes on to say OPs have higher heat resistance ?
Here's where the luddite comes in and I'm not convinced that in repairing a 50yr old Lotus, it makes any difference what you use. They all shrink a bit and from what I remember the catalyst/accelerator choice and ratios can make or break your repair. Miles Wilkins often said that repairs should be left for much longer than we'd like to settle (shrink) before sanding down or painting. His turnaround was several weeks for repairs and I think the experts in this field do the same today. So if you're leaving it for 3-4 weeks then does it really matter which one you pick ?
Brian
-
Agreed, Brian. Mea culpa . . . my link is both confusing and contradictory. I should have examined it more closely.
Ron, my presumption is that Colin used the cheapest Polyester he could find. I'm not convinced cracking can be attributed solely to the resin used and cursory examination of a bare shell will reveal what we already know - the hand laminating was done by relatively unskilled people. Some of the factory's efforts to fill defects were truely dismal.
That's not to say they didn't do an OK job, but it is what it is, as they say. There's thin sections, thick sections and pools of resin which subsequently and inevitably crack - some did on mine. To be kind, this could be considered a testament to the forgiving nature of the material, but these bodies are also 50 years old.
I favour the Polyester system because it's the well trodden path with a depth & breadth of knowledge, experience and related products not always easily found with the Epoxy system - and better the devil you know, too.
There also seems to be ample info on painting boats with Epoxy substrates but precious little re cars.
But I reckon one could largely adapt an equivalent Epoxy system.
I'd want to find some CSM with powder binding in several different weights. I believe there are non-woven veils that are Epoxy compatible.
Epoxy fairing compounds are readily available but I haven't seen anything equivalent to the 'glaze' type Polyester based automotive products.
What's the procedure from there?
Does the new Epoxy surface require a primer? Presumably it'd be epoxy primer (presumably non-etch?) over the whole car and then Polyester spray filler for the final shaping followed by urethane 2K primer and the top coats? - dunno and there's others with better knowledge than myself on this aspect and this enquiring mind would like to hear that.
So, I tend to think the shrinkage angle draws rather more attention than is deserved and doesn't come into play in any practical sense as Brian lays out.
-
I'm staying out of this because I only can comment on polyester resin repairs.
I am learning a lot though, as EuropaTC says, my experiences are 20 years old.
Shrinkage after painting, on panels that haven't been repaired are showing flaws.
Flaws in fibers rising in OEM sections, In my opinion these cars have been through a lot of environmental changes, in that they all have hidden internal flaws. Covering an entire panel with either epoxy or polyester resin will probably mask the underlying flaws, encapsulate them, so to speak for the next generation. We can only preserve history so much. WTS, lets document these repairs and compare notes in a year or so.
Dakazman
-
This whole thread reminds me of the time I asked somebody the time - they then proceeded to tell me how to build a clock.
Whilst this was interesting, at the end of an hour, I still didn't know the time.