In preparation for a replacement fender install yesterday the bonding strip was 'glued' to the replacement fender. The bonding adhesive material set up overnight. This morning I went out to test the bonding-strip-to-fender 'holding power' of the bonding adhesive.

Using thumb and fingers I was able separate a section of the bonding strip from the fender. There was a bit of flexing of the parts before the separation occurred. It took 'some' force to effect the separation but seemingly not a whole lot. Then, snap. .. Not good! ..

The bonding strip and pertinent fender section were ground with a 24 grit rotary sanding disk to prepare the surface for the bonding adhesive. Catalyzed bonding adhesive was slathered on the bonding strip and then installed onto the fender. A number of clamps held fast the bonding strip to the fender.

The bonding adhesive that was used is a polyester based material available through one of the forum vendors.

What to do. .. I'm wondering if I did something wrong. Has anyone had this happen to them? ..

 

my opinion..

bonding adhesives are just that... they don't fuse the materials to be 'bonded' together in an inseparable way in the same way a resin impregnated piece of glass cloth or mat does; if they did; you wouldn't be able to separate body panels from each other in order to make repairs.

i have to assume you cleaned the joint areas of any release agents, mixed the adhesive correctly, spread the adhesive to each part in a way that made sure it was 'sticking' to each piece before clamping the pieces together, that the adhesive had not begun to 'cure' before being applied, that you didn't squeeze most of the adhesive out when clamping, and that you let it cure for a sufficient time at the temp and humidity conditions you had.

you said you ground the surfaces to be joined and then applied and cured the adhesive. when you separated the pieces, was there any remnants of the separated piece still attached to the adhesive; ie: did some of the material pull off with the adhesive?

Bill

 

That doesn't sound right. If your using something else, I would get Ecklers bonding adhesive instead. Unless it has somehow changed in recent years, it will bond the parts properly. Other possibility is going a little too light on the hardner to compensate for the warm weather. If so the surface will feel sticky and probably won't sand without gumming up the sandpaper.

 

I did not see the most important thing what year car are you bonding too and who's parts are you bonding?? You can not bond SMC glass to a53-70 car with standard bonding material, they won't bond with out a special epoxy based bonding material, also some of the reprduction glass has silicone in it, not only won't it bond but paint won's stay on without small bubbles comming out. If you are using original glass or some NOS glass (some NOS glass is SMC) the normal bonding material is good. I make my own I buy a can of powered Fiber glass and add resin to it until it is like puddy (You only make as much as you need) add hardner and it is like Iron, store it in a cold place and you can increase the working time.

 

Bill ..
I tested the bonding adhesive cure time with a test sample before doing the actual bonding strip to fender bond. The test cure window was about 10-15 minutes before the bonding adhesive material started curing to the point where it would be unusable. With this in mind I applied the bonding adhesive to the bonding strip as quickly as possible (about 2 minutes). The amount of adhesive applied was roughly 1/8 inch thick. I tried to keep the thickness fairly uniform along the length of the bonding strip.

The bonding adhesive oozed out from top and bottom of the bonding strip and fender when the clamps were applied. The excess, along the fender edge, was removed with a putty knife. The removed bonding adhesive material was still pliable and hadn't started curing yet, at that point. Bonding adhesive was only applied to the bonding strip itself, then installed onto the fender and clamped in place. From what you say above it sounds like I should have covered both parts with bonding adhesive before joining them together.



So far only about 12 inches of the bonding strip have been separated from the fender. From what I can see it appears the bonding adhesive seems to have stuck to each piece about the same, or roughly 50/50 of bonding adhesive sticking between the bonding strip and fender. The thickness of the cured bonding adhesive where it separated from the bonding strip and fender does appear to be a bit thin.


Dan ..
The bonding adhesive I'm using is Ecklers.


65 Pro Vette ..

The car is a '64. I had read in the past here on the forum that the Ecklers bonding adhesive was a good product to use for bonding regular fiberglass panels. ..

Where to go from here? .. Remove the bonding strip, grind all the old adhesive out, give it another shot and start over? . .

 

John
i guess i'm left scratching my head, as you are... at this point, i see no alternative other than to remove all the adhesive from the pieces and start again, maybe with an expoxy type adhesive this time.

BUT, i would call Ecklers and talk with them before doing anything. i certainly will be interested in hearing what they have to say....
Bill

 

Good point, Bill. .. I'll give Ecklers a call and see what they say. At this point I have to say I'm a bit leery of using the Ecklers bonding adhesive.

There's a web page, 'The Corvette Restoration Page', where the author describes using a two part Fusor product - 127EZ - as the bonding agent that he used for bonding a replacement rear deck to his '71 resto project. I'm thinking this might be the way to go.

 

Try giving evercoat bonding adhesive #994 a try. Last week, I used this for a repair and it seemed to work really well. No problem with coming off. Also, you might want to clean it using grease and wax cleaner and a tach cloth.

Reconnected the bonding strip plus it was recommended to use to adhere the strip to the back of the glass.

 

I've used Fusor 127EZ and T21 many many times and never had a failure. They bond the upper fairings on over the road trucks and have never had one come apart. At least we never paid a claim and I'm sure if it failed we would have paid.

Fred Z.

 

I used Eckler's bonding adhesive to repair my 'dropped' front valence and that stuff is rock solid. I think if I ever need to remove it I'll have to take it off with a cold chisel....

 

That was pretty much my experience with it too. Must be an old or bad can or some problem in mixing the hardner. About 10 to 15 minutes working time, depending on the temperature, sounds about right however - not under catalyzed.

 

The material did appear to harden rock solid as you say. Without good 'stickyness', though, I have to wonder how reliable the joints will hold together after the paint goes on.

The factory applied bonding adhesive sure held tight. I had to chisel the original fender off.

I put an email in to Ecklers tech department about the problem. Waiting to hear back from them. I'll post back here what they have to say. Thanks for the replies.

 

Email sent 3 1/2 days ago - no word back from Ecklers. Customer service has to stand for something. Is the the best they can do? . . Time to move on. Going with the Fusor product.