24 replies to this topic

[cornishcrock]

Putting on new sills and jacking points.  Was going to weld on but toying with the idea of using 3M panel adhesive 08115 which comes in a 2 part tube that mixes as you push it out.

I know they don't suggest it for structural work but has anybody used it to put sills etc on?  Thought it might be good as I could paint up the inside of the sills before putting them on also it doesn't encourage rust which would save me treating all the welds with rust converter.

Thing is, it needs to have a temperature of around 70F to go off.  Not going to be that warm in the garage (not even the house is that warm).  I could apply heat in the form of a hot-air  gun or the like but just how long would I need to heat it for?  It says it will go off in about 4hrs in 70F so would it go quicker with hotter air?

Never used this stuff but as a lot of the modern car manufacturers use it to assemble cars now thought it worth considering.

Another drawback is that you need a special application gun which is very pricey.

Would appreciate some advice.

[alex-95]

No, weld them on.

[myredmini]

The structure of the mini was designed for all panels to be welded as they are. Modern cars are specially designed with these new adhesive bonding methods in mind.

Especially with something as crucial as a sill it really needs to be plug/spot welded on.

[spiguy]

Apart from anything else, it could fail an MOT if the tester noticed a lack of evidence of welds. This would not be an acceptable method of attaching sills on a mini from an MOT perspective. I'm not even sure if it would be acceptable on a car where this was the original method of assembly - as far as I am aware the rule is that a complete replacement panel can be spot/plug welded on, whereas a patch / replacement section must be attached with a continuous seam weld.

[The Matt]

A seamlessly bonded sill, using a decent adhesive would no doubt be as good, or better than the original in terms of strength.  But the issue may well be that the 'repair' is different to the OE specification.  Could fail an MOT? Yeah, but could pass if the tester doesn't spot the fact it's bonded on.

 

I think the idea is sound in terms of structure, but as the method isn't approved (as mentioned above).

[Daz1968]

If you were spot welding the sills on it is safe to use the adhesive and spot weld the joint, but can't be used on its own for structural applications.

[crazypainter]

According to manufactures regulations of modern cars 3M panel bond is the right product to use, if used correctly.

You CAN only use it on two surfaces that contact directly so you will still need to plug-spot the floor join, heel Board and inner front arch.

The only area on an out sill you can bond is the external lip to lower quarter/side step.

The contact surface area is greater than when welded and stronger.

There have been strength tests for panel bond vs MIG plug/spot and each and every time panel bond came out on top.

People can think and do what they want by above is the facts, I know I teach it.

[castafiore]

It may well produce the requisite strength but as others have said I don't think it would pass an mot if noticed by the examiner. This has been discussed at length on the mig forum and the outcome seems to be that you can use spot welds if the original panels were spot welded. If you are repairing a patch it must be seam welded. As panel glue wasn't the original method, I don't see how it would pass an mot on a Mini.

[crazypainter]

We train VOSA testers where I work and they say there's nothing wrong with it. If there was modern brand new cars would fail on their first MOT.

Personally I've never had any issues in fact the testers I know do not bad an eye lid.

If you were to mig plug you would level welds and paint leaving a smooth finish both sides and bonding gives you then same.

Most spot welds if prepped and painted correctly are lost also leaving a smooth edge along the external join.

So basically if done right the out come and finaihed result should look the same.

[Steve G]

Using adhesives to stick Mini's together is interesting. I'm not in the trade but know a lot of repairs on modern cars involve sticking repair panels on where there wouldn't originally been joins. 

A lot of corrosion starts where two panels are spot welded as the don't normally get any paint. Properly prepared glued joints would be completely sealed. 

Cars like the McLaren SLR although made from Carbon Fibre are glued together, I expect it's mainly cost that stops most manufacturers doing the same.

[Tamworthbay]

A seamlessly bonded sill, using a decent adhesive would no doubt be as good, or better than the original in terms of strength.  But the issue may well be that the 'repair' is different to the OE specification.  Could fail an MOT? Yeah, but could pass if the tester doesn't spot the fact it's bonded on.
 
I think the idea is sound in terms of structure, but as the method isn't approved (as mentioned above).

+1 I have built whole cars using structural adhesive but it MUST be a full structural adhesive. 3M DP410 is brilliant and is used for F1 and LMP kit (and I believe Airbus wings but not 100% sure) so you can be assured it's good stuff. However the key with any structural adhesive is that it is only as good as the surface it sticks to. If you have a genuinely chemically clean surface than its amazing. A 25mm square patch of DP410 would easily support the weight of a mini. You also have to look at potential load paths in an accident, the metal would bend but the blue can't so the metal would peel from the glue line. How much energy is needed to do that? I don't know and without crash testing there is no way to find out. Could you get a properly chemically clean surface on an old mini sill area? Almost certainly not. Would I ever use it in a mini instead of welding in a structural area? 100% not. And that is before the issues regarding MOTs

[petey81]

Many car wings are just screwed in. As mentioned planes boats and other machines use bonding to attach panels.

[sonikk4]

Many car wings are just screwed in. As mentioned planes boats and other machines use bonding to attach panels.

True but they are designed from scratch with this joining process in mind. A mini was designed with welding as the joining process. Deviate away from that process at your peril.

[cornishcrock]

Thanks for all your views on this.  Between the cost of the adhesive and the applicator gun AND the chance of some MOT testers failing it, have decided to go down the old welding route after all.. 

[petey81]

Many car wings are just screwed in. As mentioned planes boats and other machines use bonding to attach panels.

True but they are designed from scratch with this joining process in mind. A mini was designed with welding as the joining process. Deviate away from that process at your peril.

Absolutely correct