Why I will not glue on quarter panels

dougklink

Member
Adhesive bonding its now used to assemble all modern cars with great success. I used 3M 8115 to attach my rear lower quarters and we use it on all our fire truck restorations when replacing sheet metal. You have to do it correctly though, which this guy obviously didn't. Welding has its own problems such as protecting the welded area from future rust in places you can't get to so it has to be done correctly too. A hack can botch up either one and a skilled person can do a nice job either way imho.
 

jfriese

Active Member
I agree with Doug. Using the type of adhesives that the manufacturers use result in a perfect, watertight and strong bond. This is especially true if you are replacing lower door skins because the excess glue oozes up into a small area that Amphicar didn't pay enough attention to and unfortunately can result in catastrophic rust problems in door bottoms. Use extra adhesive along those outer edges and just wipe off the excess. A light wipe along the inside will leave a nice filet of glue that fills that small gap at the bottom of the doors between the inner door frame and the outer skin.

John Friese
67 White
67 Red
 
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Midwest Amphicar

Worlds Largest Amphicar Destination
A full quarter patch or quarter panel is structural integrity to the entire car/boat. The quarter patches I or others make are not factory stamped. The steel wants to revert to its original shape of flat. New cars are ENGINEERED using crazy over the top hybrid metals for adhesives. Putting a welder to a 2013 Ford F 100 frame would result in ... a law suit. A door skin is not structural. It is easy to have one or two positive experiences then extrapolate your findings for continued success. Nearing 20 years now of seeing the good, the bad and the ugly. Glue non important parts, weld structural for safety. No argument just will not do it.
 

mike_israel

Amphicar Forum Admin
Staff member
Adhesive technology is advancing rapidly and certainly has its place. This does not mean it is a substitute for all welding applications.

Much depends on the design / intended use of a given structure. As used in aviation, the structure and parts are designed to be built using adhesive. Thus, the joint will have large surfaces in contact to allow the adhesive to create a bond over a large area. The cumulative strength is proportional to the unit area. Also the direction that forces applied to the structure act in is important. In a straight pull situation adhesives can be quite strong, introduce twisting movements or shock and they can fail much easier, depending on the adhesive. Bonding edge to edge is not advised with adhesive as there is too little surface area.

Yes, the auto industry is increasingly using adhesives and are designing many parts accordingly. However, many of those adhesive products will not be found on the shelf at your local auto body supply shop. They have a very limited shelf life (days or weeks from manufacture) and are therefore not generally available to the wider public. You can buy some really amazing adhesives but just as most shops will not have access to robotic laser welders, most will not have access to the stuff used in the factory. None of the auto manufacturers have abandoned welding quite yet.

I see an increasing number of uses for adhesives. At least for today, on things like mild steel quarter panels, there is still nothing better than a professional TIG weld. Crappy welding is another story but that is not the fault of the technology.

Alternate opinions are always welcomed!

BTW, Glad to hear Daves news that smoking is safe. I guess I should take up the habit! :)
 

dougklink

Member
Poor application of adhesive is not the fault of the adhesive either. If I was doing a full quarter I'd weld, but for a lower rear quarter with a good joint edge flanged into it under the rub rail area you have lots of glue area compared to the size of the panel. I respect those who want to weld, I just feel for me the adhesive is a preferred process. And I take that decision into the lake with me every time I swim. 3m 8115 is available though any parts store if you order it or on line. It is a professional product and we have experience using it in a professional restoration shop. I just didn't like the inference that the userof adhesive implied a crappy job. It's just a technique choice, a novice could screw up welding just as badly as adhesive. Nuf said for me, let's be open minded.
 

mike_israel

Amphicar Forum Admin
Staff member
This comes directly from the 3M 8115 technical data sheet.

When the manufacturer’s directions are followed, this product can be used to bond
door skins, roof skins, quarter panels and box sides. In addition, product can be
used for bumper cover repair under certain conditions. Typical substrates include
cold roll steel, aluminum, SMC, and FRP. This product is not intended to bond
structural components of a vehicle such pillars, rockers, or frame members.
If doubt exists as to whether a particular component is structural, then that
component should be welded.
 

jfriese

Active Member
Mike,

I think that tech data sheet says most of all you need to know. We all know that plastic glues are fine for areas with a large bonding surface but useless for small contact areas subject to large loads. I personally like to patch skin areas with tightly fitted pieces of steel sheet and butt weld them in. Certainly not a situation that is well suited for a glue bond. Nuff said by me.

John Friese
67 White
67 Red
 

SNOWBIRD

Amphicar Expert
I tryed to post some pics of the workings of my Fiberglass Amphicar but they were too large.
Put together right this car hits the water at 30 mph.With Dave in the back!(gee he got wet...)
Now metal to metal on an Amphicar..... WELD..
Just did one where a fast bodyshop put rear quarter patches on (right over the old rust)
with what looked like silacone. I just started a corner and pealed the whole thing off!
 

peterboz

New Member
Hi there,

I have remove the skin of my trunk cover by drilling out the spot welds and repaired it . After sandblasting I have put 2 k epoxy primer on it .So far everything went good.
But know i am wondering what to do , spot welding everything back or glue it back together.
Normale I prefer welds but the epoxy is burned off again and then the rust will kick in very soon.
With glue no heat so no damage to paint or primer.
Anybody done this with glue????
 

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