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Discussion Starter #1
Found this post on ARBB - at first I thought the OP was having a laugh but then did a bit of digging and found a lot of discussion about it - glues are commonly used in modern car construction - I mean the metal to metal bit - and have been used in aeroplane wings for many years so what about on old Alfa's, I'm not an engineer but I know some here are so would be interested to know their opinions?



"For replacement of floor panels, entirely or sections, has anyone used, or considered, using adhesive instead of welding? There are some pretty amazing permanent adhesives available for automotive and marine applications, so resistant to any number of environmental factors. Any thoughts from the group?"
 

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I have been a windscreen fitter on & off for the last 25 years. Most of the older cars I have owned have had various metal plates & panels bonded to them using the glue I use for glass. My most recent Transit van has a plate glued to the rear floor now. Non structural areas I don't have a problem with but don't think the mot inspector would like to see outer sills & the like bonbed on.
 

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There are specific primers to go with the glue I use. Can be used on painted or bare metal but nothing is going to stick 2 pieces of metal together if 1 or both are rusty.
 

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Modern cars designed to use adhesive, with chassis strength designed around this. Whereas old cars I'm not sure I'd be as happy to have bonding in crash prone areas.

Happy to see proof though.

Although there then kicks in the technique vs origenalty. If you owned a GTA junior, would you crash repair with welding, or the origenal riveting ????
 

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Modern cars designed to use adhesive, with chassis strength designed around this. Whereas old cars I'm not sure I'd be as happy to have bonding in crash prone areas.

Happy to see proof though.

Although there then kicks in the technique vs origenalty. If you owned a GTA junior, would you crash repair with welding, or the origenal riveting ????
I think regardless of whether its welded or bonded a serious crash is going to have the same outcome in a 40+ yr old car :(
 

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I worked on some repair schemes for the Lotus Elise chassis, ironically at The Welding Institute, which all used adhesives and they were outrageously strong, in most cases stronger than the aluminium substrate.

Would I glue my car back together? No, as I don't have a clue how the adhesive systems work! Would I let someone who understands the stuff do it? Absolutely.
 

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Jaguar Sports cars are made out of bits of glued together tin foil, I've seen them being made in the factory, it's a bit bonkers and very cool
 

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When I built a Lotus 7 copy loads of people used adhesive or industrial strength double sided tape to fix ali floor pans to tube chassis rails. Compared to the traditional rivet system it was a lot stronger due to the surface area compared to the size of rivet heads. As said its all down to the design and the way forces are applied.
 

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When I built a Lotus 7 copy loads of people used adhesive or industrial strength double sided tape to fix ali floor pans to tube chassis rails. Compared to the traditional rivet system it was a lot stronger due to the surface area compared to the size of rivet heads. As said its all down to the design and the way forces are applied.
And in that scenario you're also not drilling lots and lots of holes in the chassis, which while it probably only has a minor effect on strength does serve to provide an (eventual) point of water ingress into the tube sections. I did something similar - about 200 rivets and a couple of tubes of some black gunk which while being an adhesive and a sealant for the rivets you just know water will work in eventually.
Rivets went in from underside too. And I really, really wished I'd bought an air riveter - but covered in gunk and halfway round wasn't the time to nip out to Machine Mart!
 

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Discussion Starter #11
I think regardless of whether its welded or bonded a serious crash is going to have the same outcome in a 40+ yr old car :(
I think I'd agree with that - our classics have no crumple zones, air bags, deformable steering columns etc, just makes you a bit more aware of the traffic around you and drive accordingly, whether welding and glueing the priority is good prep and find clean metal, problem I could see with glue is you can drill spot welds but if the whole panel is glued how do you get it off if you need to?
Interesting discussion
 

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The major enemy with all on the road cars is rock salt, so if you have underside corrosion on the floor pan, sills,outriggers etc. etc. weld repairs are the only way to go, until they mass produce rot proof bellies for production cars. ;)
 

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Adhesive bonding is on the rise due to a) strength and b) weight savings. Adhesive bonded parts perform much better in crash tests without tons of reinforcement. BMW, MB, Porsche, etc all utilize adhesive bonding in their construction. The new 991 Porsche should be pulled, even on a jig bench to avoid possibility of adhesive bonding cracking between structural components.

the process for adhesive bonding recommended by many manufacturers still utilize the use of rivets. The bonding kits are not cheap, for example BMW costs roughly $450 for glues and rivets.

Surely it's an interesting concept in reinforcing some areas of the Alfa. However in order to accomplish that, the components must be removed, surfaces ground down. Adhesives have one drawback - you have to get it right the first time, unlike spot welding where you can drill out welds and retry...
 
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