Panel Bonding

[ckrueger]

What is the general contentious out there on using the silicone as called out in the manual vs a panel adhesive. Does it offer a better product in the end or just overkill?

Chuck

[michael everson]

There really isn't any reason to use anything but silicone. Of course you will get 10 different opinions on this. I have built over 38 FFR kits and have always used silicone.
Mike

[68GT500MAN]

I have always used silicone when attaching the panels. I had to use piano wire and a LOT of elbow grease to remove them later when needed.
Doug

[Robert Andrew]

What is the general contentious out there on using the silicone as called out in the manual vs a panel adhesive. Does it offer a better product in the end or just overkill?

Chuck

Many one part silicones contain acetic acid, which like most acid is corrosive. Over long term they may cause significant internal corrosion on bonded parts, especially ferrous metals. There are silicone adhesives which don't contain acetic acid, so you should look for the proper silicone compound. Polyurethane adhesives are non-corrosive, but also more permanent. More permanent when you get it on your hands and fingers, and more permanent bonding agents. Some polyurethanes require a little bit of moisture to cure, so read the instructions carefully. The aircraft industry uses epoxy systems for metal bonding, and there are a number of professional grade epoxy products on the market specifically designed for bonding various types of metal together. Some require heat curing, some cure at ambient temperatures. The epoxies are definitely permanent adhesives.

[ckrueger]

Thanks for the info so far. I see Breeze offers a Bostik 1100 and a Bondaflex 21110. Both are urethane adhesives. Anyone have experiences with these. I plan on powder coating most of the panels and the frame will be powder coated, so maybe the risk of corrosion from the acetic acid in the silicone will be reduced????

[SCFFR]

I was under the impression that the silicone we used on the panels was mostly to seal and help prevent rattles/vibration and less of a bonding agent. I thought the rivets/screws provided all the attachment strength. Definitely important for all of the floor panels in case you run through some wet roads.

[edwardb]

This subject is way over analyzed, IMHO. The chassis on these cars is extremely rigid, and doesn't need the aluminum panels for additional strength. The body sits mostly on chassis components, but it's not heavy anyway. The panels form the footboxes, cockpit, trunk, engine compartment, etc. but high strength is not a big topic. As long as they are mechanically sound, they're not going anywhere. Agreed it's important that they are sealed from moisture, dust, etc. and you don't want them rattling around. But debating over what adhesive, e.g. silicone, ureathane, epoxy, etc. just isn't necessary. Properly applied, all are going to give way more strength than necessary. The decision is better left to best value and simplest to apply. I can't cite the number of builds as Mike (not many can) but with two I've tried both silicone and ureathane. The ureathane was more expensive and harder to clean up. I've tried several silicone products. The best I've found is GE II silicone builder's caulk at Home Depot, Lowes, etc. Made for 20-25 years in the outside elements, comes in a large caulking gun tube, multiple colors available, quite reasonably priced, cleans up relatively easily as you're building. If you've ever tried disassembly after using (I have unfortunately) and as others have cited, it's very difficult and often the piece is damaged/destroyed. So yes, it's giving significant additional strength to the bond. The rivets are important to get everything lined up, pulled together, etc. But once the adhesive sets up, they're probably not doing too much. Regarding the citric acid discussion, this material doesn't have that strong citric smell like some of the bathtub caulk materials. I Just looked it up, and based on the MSDS looks like it's an ammonia based cure. I really don't think corrosion, especially with PC'd panels, is anything that should be worried about.

[ckrueger]

edwardb - Thanks for the input. Makes sense and I will probably just stick with the silicone. You are correct in the adhesion properties. I had a prefabricated glass block wall I had made for my house and they assembled the glass blocks with silicone in that application. I had to take it apart and it was a pain in the butt!

[michael everson]

Since your powder coating your panels, go with black silicone. Assuming your going black.
Mike

[fastthings]

Many one part silicones contain acetic acid, which like most acid is corrosive. Over long term they may cause significant internal corrosion on bonded parts, especially ferrous metals. There are silicone adhesives which don't contain acetic acid, so you should look for the proper silicone compound. Polyurethane adhesives are non-corrosive, but also more permanent. More permanent when you get it on your hands and fingers, and more permanent bonding agents. Some polyurethanes require a little bit of moisture to cure, so read the instructions carefully. The aircraft industry uses epoxy systems for metal bonding, and there are a number of professional grade epoxy products on the market specifically designed for bonding various types of metal together. Some require heat curing, some cure at ambient temperatures. The epoxies are definitely permanent adhesives.

Most don't believe that silicone will rust the metal it bonds, but it does. I've been a body man all my life, silicone is outlawed in body shops. Paint don't stick to it and it won't last. It will eventually rust the metal right under the top coat. You won't even know it until the paint bubbles off. I'm not sure why this is not more common knowledge, except maybe because it takes so long for it to happen.

[amasciarelli21]

I used panel adhesive on my firewall panels I don't think i'll ever get them off and black silicone on aluminum that i've installed so far, seems to work fine. Silicone is not on bare metal- powder coat on frame and lizard skin on panels so I hope corrosion isn't an issue

[VdubJoe]

I agree with edwardb . Take some silicone and bond a piece let it dry. Take it apart and see what a pain it is. I use the GE stuff.
Works great.

Joe

[Scargo]

Regarding RTV silicones, there is the acetoxy cure silicone (which smells of acetic acid), and the moisture cure type, which relies on moisture in the air. A lot, regarding performance, is going to hinge on what you are bonding to. Acetoxy cure is generally stronger with a higher peel strength. It would be good for powder coated paints, conversion coatings and anodized aluminum but not good for bare metals and possibly not great (or a good idea), for regular automotive paints. My experience is that acetoxy cure type silicone was used to put glass in car frames, painted with regular automotive paint, with no ill effects.
A data sheet for an acetoxy cure industrial grade structural adhesive that GE offers (http://www.siliconeforbuilding.com/pdf/speciality/Data_Sheet_SCS1200_Construction.pdf).
Moisture cure data sheet. (http://www.siliconeforbuilding.com/pdf/structuralglazing/Data_Sheet_SSG4000_UltraGlaze.pdf) Again, both not recommended for bare metals.

Rather than speculating, if you have something unique, like let's say Lizard Skin or POR 15, I would suggest calling a manufacturer's rep or looking on a website forProduct enquiries for Momentive, who seems to be making the "GE" brand now:

Toll Free

+1 888 443 9466


Direct Dial

+1 614 986 2497

[fastthings]

I won't get into the strenght debate. I'm just talking about something like holding on something as simple as a emblem. I always thought it attracted moisture, but I never understood how it got threw a nice sealed up paint job. After hearing the acid thing, maybe that makes more sense. It does though, now I don't know about powder coat, that may be fine. I just stay away from it, after seeing what it does over time.

Just my observation,
Gene

[michael everson]

There really isn't any reason to use anything but silicone. Of course you will get 10 different opinions on this. I have built over 38 FFR kits and have always used silicone.
Mike

See? told you.:):)

[Scargo]

There really isn't any reason to use anything but silicone. Of course you will get 10 different opinions on this. I have built over 38 FFR kits and have always used silicone.
Mike
Was it acetoxy cure silicone or moisture cure? Have any joints ever been taken apart and examined? Have any failed to adhere? Has anyone seen signs of paint blistering, peeling or coming off with the silicone? Has any one done any tests on samples of various coatings/substrates? That's why I included the numbers to call.:cool:

[michael everson]

I am not a Chemist. Just followed FFRs recomendation like every one else. I have removed some panels years later with no adverse affects. In fact my first Coba was completely dismantled 6 years after I built it, to have the frame powder coated. No damage at all from the silicone. Had a heck of a time getting some of the panels unglued though.
Mike

[oldguy668]

Whatever panel bonding method you decide to use, invest in a gallon of Acetone so you can clean both the aluminum and the steel just before you bond and rivet. If you use original GE silicone, also get some denatured alcohol. It will clean up UNCURED silicone like it was never there.

[rtz]

Has anyone ever done a rivetless build using only bonded panels?