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Best Adhesive for Plywood Struts to Foam Board

Mr NCT

Elite member
#1
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!!

IMG_3616.JPG
 
#2
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

Master member
#3
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

Legendary member
#4
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
 
#5
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.
 

Mr NCT

Elite member
#11
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.

IMG_3617 (2)_LI.jpg


Note: No animals, glues, snowflakes or Karens were harmed in the conducting of these tests. Conclusions are purely subjective, your results may differ.
 
#12
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.
 

Taildragger

Legendary member
#14
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

Elite member
#17
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.
 
#19
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.