Best Adhesive for Plywood Struts to Foam Board

[Mr NCT]

I'm not in a rush to glue the struts and cabanes on my Jenny so I thought I'd test different adhesives and see which held the best and, most importantly, which don't work well. I'm using 3/8" wide strips of 3/32 ply. I slit the FB, widened the hole to accept the ply and applied adhesives per the instructions. I'll check them in 24 hours or so.

Place your bets!!

 

[Monte.C]

My prediction: For every one of those samples the foam around the glue joint will break (equally among the samples). The glue joint itself will not break. I would say for a stronger connection you would need to re-engineer it for more surface area or for some sort of additional structure behind the FB.

 

[Tench745]

My prediction: For every one of those samples the foam around the glue joint will break (equally among the samples). The glue joint itself will not break. I would say for a stronger connection you would need to re-engineer it for more surface area or for some sort of additional structure behind the FB.

I would tend to agree with this assessment. I think the strength of the joint will largely be in the strength of the glue bond to the paper.

 

[Ratcheeroo]

I agree with @Monte.C , probably a better way would be to "lock" that piece into place with a thin piece of ply on other side of foamboard. Another way is to use a hook and loop system by using wire and your wood. It would take me a while to find the pics but if you go through the 2021 Piper Challenge thread I am pretty sure I posted pics of what I am referring to as hook and loop when I attached my struts

 

[Monte.C]

One thought I have is if you add a second layer of FB, like a small plate maybe 1-1/2" square, under the outer layer so it's hidden inside the wing. Glue through both layers. That would add a load of strength, probably all you need.

 

[Monte.C]

Good job @Mr NCT , you gave us all something to keep us occupied for a few minutes.

 

[Mr NCT]

Good job @Mr NCT , you gave us all something to keep us occupied for a few minutes.

I was going to add vacuum bagged carbon fiber with titanium threads but then I thought "Ah, the rest of the plane's foam board."

 

[Monte.C]

I was going to add vacuum bagged carbon fiber with titanium threads but then I thought "Ah, the rest of the plane's foam board."

Right! Remember, you don't need a 24 hour epoxy on a paper airplane!!

 

[Mr NCT]

I'll be sure and post a video of the top wing coming loose in flight!

 

[Monte.C]

I'll be sure and post a video of the top wing coming loose in flight!

 

[Mr NCT]

The results of my semi-scientific and totally subjective test.
First I checked for side to side stiffness with a recently calibrated index finger
Best - hot glue
Tied in the middle - foam cure, gorilla, foam safe medium CA
Worst - beacon
Next I pulled them out of the foam board. Fingers flat on the FB, 1/2" each side of the stick and 14" away from the edge of the table (with a right torn rotator cuff).
Beacon pulled out easily
Gorilla clear and foam safe CA both put up some resistance and pulled up some foam
Foam Cure put up a little more resistance and tore the paper
Hot Glue bowed the foam board and I had to move it closer to me to pull it out.

Sorry @Monte.C, but the clear winner in this test was hot glue.

Note: No animals, glues, snowflakes or Karens were harmed in the conducting of these tests. Conclusions are purely subjective, your results may differ.

 

[Monte.C]

Sorry @Monte.C, but the clear winner in this test was hot glue.
Note: No animals, glues, snowflakes or Karens were harmed in the conducting of these tests. Conclusions are purely subjective, your results may differ.

Test was rigged. If it's not on video it didn't happen. And I bet there was some copyright infringement involved. And hurt feelings. MY hurt feelings.

 

[Mr NCT]

Test was rigged. If it's not on video it didn't happen. And I bet there was some copyright infringement involved. And hurt feelings. MY hurt feelings.

Glueist!

 

[rcbigtirepilot]

The results of my semi-scientific and totally subjective test.
First I checked for side to side stiffness with a recently calibrated index finger
Best - hot glue
Tied in the middle - foam cure, gorilla, foam safe medium CA
Worst - beacon
Next I pulled them out of the foam board. Fingers flat on the FB, 1/2" each side of the stick and 14" away from the edge of the table (with a right torn rotator cuff).
Beacon pulled out easily
Gorilla clear and foam safe CA both put up some resistance and pulled up some foam
Foam Cure put up a little more resistance and tore the paper
Hot Glue bowed the foam board and I had to move it closer to me to pull it out.

Sorry @Monte.C, but the clear winner in this test was hot glue.

View attachment 220829

Note: No animals, glues, snowflakes or Karens were harmed in the conducting of these tests. Conclusions are purely subjective, your results may differ.

Yeah could have told you it would be hot glue. The struts on my kitfox are SOLID

 

[Mr NCT]

Yeah could have told you it would be hot glue. The struts on my kitfox are SOLID

Man! You could have saved me a bunch of time. But now the results are glued in my brain - no more experiments needed.

 

[Monte.C]

While my planes keep falling apart if you look at them crooked.

 

[Mr NCT]

It looked to me the with the exception of the Beacons they all glued to the foam but the hot glue was the best at adhering to the brown paper of the FTFB with the Foam Cure a middle second.

 

[Mr NCT]

Your trick of cutting windows in the paper so you get foam to foam is a good idea with the Foam Cure.

 

[Monte.C]

It looked to me the with the exception of the Beacons they all glued to the foam but the hot glue was the best at adhering to the brown paper of the FTFB with the Foam Cure a middle second.

Yeah that's exciting to hear about the BSI Foam Cure. Word on the street is Beacon Foam Tac rules. For like half the price I buy BSI. Who woulda thunk.

I've wondered about that myself, that hot glue doesn't seem to have a problem with brown FB. Must be the heat of application.

Oh and for just a couple things I use CA, and so far I haven't experienced any issues whatsoever with CA adhering to brown. Cross fingers.

 

[rcbigtirepilot]

While my planes keep falling apart if you look at them crooked.

or if you build them crooked