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MG Midget and Sprite Technical - Bonding on rear wing panels

I am in the process of replacing my rear wings and I have the half height repair panels.

Has anyone ever bonded these in along the wheel arch edge and to the panel that forms the boot floor corner? (Both the inner arch and boot floor will be new panels "properly" welded in).

I would weld the wing repair along the top edge (joint to old wing) to the sill, B post and where it joins under the rear lights.

Part of my brain thinks it's a great idea. The other part says "just weld it, fool".

There are some pretty amazing adhesives about these days and there is plenty of surface area between these two. I would also be so bold as to say I bet a bonded joint would be stronger than my welding! I just can't prove it.

People bond on fibreglass rear ends, right?!

Malcolm
Malcolm Le Chevalier

Hi Malcolm. I can't in principal think why not so long as you use an appropriate bonding agent. Now there in is the question.

If bonding GRP the GRP you are using for bonding bonds chemically to the GRP shell you are adding so at least one side of the bond should be a flawless homogenous mass so only one bond interface (with the metal). You drill holes in the metal side of the bond so that you can grp along the hidden back to get the metal 'embedded' in the GRP and GRP 'through' the metal and all is well.

What you are suggesting is two bonding interfaces with a material that is not chemically part of either side of the bond.

This is a question for a metal to metal bonding expert before you do it. I know its possible but ....

I also know that FrankeFrog owner (can't remember his name) from Thailand knows about bonding. He may know about this metal to metal or knows a man that does.

Keep going , sounds like its going OK, progress report if you have time. If not keep at it. Cheers, Dave
Dave Squire (1500)

Hey malcolm,

I did it.

Not with the rear wing, but I do plan to do that area as well when I do the swa to rwa conversion

I did it on a critical area... the top portion that fits on top of the fire wall and connect to the 2 A post that the windshild sits on top of and the dash bolts to... what ever panal thats called

It worked great... not a problem and super strong

Once I got everything lined up and into place... I drilled for pop rivets, then used the really long set time (48) hours 2 part epoxy from locite then pop riveted for several days to insure full tight bonding then removed the pop rivets and finished

My plan on the rear wings is to avoid a butt joint and do a stair step over lap (my terminology) ... a zig zag going into a zag zig over lap...I hope that makes scence

I think the joint so strong there is no way it would be torn apart

The true secret is in the prep work... super shinny metal and then a harsh rasp file to scar up the area to be glued so it has a harsh edge for the glue to grip onto

Avoid the fast setting stuff like the plague..longer the set / cure time the better

The real set back on useing this method, is the time involved, welding is fast normally less then a few hours....glueing is at least a minume of 48 hours

If my welding skills were better for such an important area, both structural and appearance....then yes id weld it... but im a welding hack... I know just enough to set my seats and interior on fire.

Thats my personal experiance

Prop
Prop and the Blackhole Midget

Sikaflex.
there are several varieties, could do worse than ask some local bodyshops which type they use.
David Smith

Just a quick update on this, thanks for your advice Dave, David and Prop.

I have had some experience in bonding things at uni. A fair bit of the wee race car I built was glued together, thats why I thought about doing it. Your thoughts and experiences are also encouraging.

The only issue maybe is the crappy fit of replacement panels. Big gaps don't help the bond. Sikaflex would perhaps help this but then the bond is quite flexible... hmmm...

Finally, Prop, yes it might take 48 hours to set but I can spend those 48 hours getting drunk or something, I don't have to sit and watch it! :-D

Cheers guys,
Malcolm
Malcolm Le Chevalier

Correction Malcolm, you can use the 48 hours working on something else on the Midge!

Oops I'l get my hard hat. :-)
Dave Squire (1500)

Malcolm

Not quite what you asked, but worth looking at how Sebring Sprite replicas bond grp Frogeye rear ends to steel B posts and rear floor, with a combination of adhesive and rivets, e.g. http://www.sebringsprite.com/henderson.html

Bonding can be with a 3M product apparently 3M 08793 Polyurethane Mastic: http://catalogue.3m.eu/en_eu/eu-aad/Sealers/Extruded_Sealers/td%7EPolyurethane_Sealer_in_Sachet%7Enocode/Polyurethane_Sealer%7E08793

Cheers
Mike
M Wood

Mike do you have a link to a spec sheet for that 3M stuff? Unusual for a sealer to have good or better bonding properties.
David Smith

David

Good point, I had wondered how good a bond such a sealant would provide (probably structural join is by rivet and sealant provides just that). Can't find a spec sheet for it, but perhaps the following product may be better answer to Malcolm's problem anyway: http://catalogue.3m.co.uk/en_gb/gb-aad/Adhesives/Panel_Bonding_Adhesives/td%7EPanel_Bonding_Adhesive%7Enocode

(Also look at: http://catalogue.3m.co.uk/en_gb/gb-aad/Adhesives/Panel_Bonding_Adhesives/td%7EStructural_Adhesive%7Enocode)

As for the steel GRP join I brought up, the Broadspeed GT had such a join which must have been done with grp lamination (have a pic in Miles Wilkins grp car repair book) - perhaps with perforations in the steel to help integrate the grp lamination over a larger area? - and I guess the non-aluminium Sebring Sprites grp rear body sections may have been done that way too in the old days? (Not sure how Sebring Sprite grp roof and windscreen are/were effectively joined to front metal scuttle).

Thanks
Mike
M Wood

which is why I mentioned Sikaflex. It's used by manufacturers to bond panels on and the right sort is almost epoxy adhesive strength.
David Smith

Malcolm,
I know this is a B but have a look at the first para of page 4
http://www.an-mg-is-born.com/pdfs/january-2006.pdf

This is the product in question I think

http://www.lord.com/products-and-solutions/adhesives/automotive-repair-adhesives/product.xml/289

or

http://www.lord.com/products-and-solutions/adhesives/product.xml/1622

I'm considering using something like it on the rear wings of my projects if only because I'm fed up with grinding the tops of the plug welds ;)

Best of....
MGmike

M McAndrew

This thread was discussed between 02/09/2013 and 04/09/2013

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