Help! New Plastic Motor Mounts Pulling Free

[Hvon11]

I built the FT Tutor with the new plastic firewall/motor mount; hot glued it and taped it to the pod as per build video. I use clear packaging tape on all my builds. After several flights and a few crashes I noticed the plastic had become unstuck from the pod foam. Reglued and retaped and all is well. Yesterday i went to fly my Spitfire, 20+ flights and no crashes and it has the same plastic mount, as I throttled up for launch the motor pulled free. Held back by the power leads it swung into the wing and chewed it up and broke prop before I could throttle down. The plastic had become unstuck from the hotglue (no glue on plastic at all) and the tape simply ripped free at the corners. Picture attached.

I repaired it using strapping tape, the kind with fiber filaments inside. Will fly again this morning and will be pre-flight checking this from now on. Never had a problem with the plywood firewalls. Anyone else experiencing glue unsticking on plastic mount?

 

[SSgt Duramax]

I use those (I assume those are pretty much the 3D printed ones sponz made). I'll tell you what I do.

I rough up the contact surface with some 80 grit, although a wire brush (like the stiff ones for welding) work well too.

Next I put some white gorilla glue in there, you don't need too much, it expands, it also moistens and goes through the paper and soaks into the foam. It does a decent job bonding to the plastic too.

Before it dries, I tape the motor mount using either gorilla packing tape or the fiber reinforced packing tape. I suppose if you really want it indestructible, you could use some thick duct tape like the gorilla brand duct tape. It is heavy, but neigh on bullet proof on most uses for us.

If the tape is losing bond to the plastic, stick some super glue or CA between the tape and the plastic.

The last motor mount I went to remove from a power pod like this, I removed the tape, and the motor mount itself split before it let go of the foam.

For whatever reason, hot glue does an abysmal job of bonding to the plastic. 100% guaranteed it will come off. You could drill little holes in that joiner that goes up into the powerpod to let the hot glue pass through if you are set on using hot glue.

 

[Hvon11]

I use those (I assume those are pretty much the 3D printed ones sponz made). I'll tell you what I do.

I rough up the contact surface with some 80 grit, although a wire brush (like the stiff ones for welding) work well too.

Next I put some white gorilla glue in there, you don't need too much, it expands, it also moistens and goes through the paper and soaks into the foam. It does a decent job bonding to the plastic too.

Before it dries, I tape the motor mount using either gorilla packing tape or the fiber reinforced packing tape. I suppose if you really want it indestructible, you could use some thick duct tape like the gorilla brand duct tape. It is heavy, but neigh on bullet proof on most uses for us.

If the tape is losing bond to the plastic, stick some super glue or CA between the tape and the plastic.

The last motor mount I went to remove from a power pod like this, I removed the tape, and the motor mount itself split before it let go of the foam.

For whatever reason, hot glue does an abysmal job of bonding to the plastic. 100% guaranteed it will come off. You could drill little holes in that joiner that goes up into the powerpod to let the hot glue pass through if you are set on using hot glue.

Awesome tips. Will try the gorilla glue. Thanks!

 

[WillL84]

I don't see any packing tape over the face of the mount, might just be the lighting though. I had a nasty crash on my Legacy last weekend and they didn't pull out. The motor mounts actually pulled on the skewers holding them into the nacelles and egged out the holes in the nacelles.

 

[skymaster]

I built the FT Tutor with the new plastic firewall/motor mount; hot glued it and taped it to the pod as per build video. I use clear packaging tape on all my builds. After several flights and a few crashes I noticed the plastic had become unstuck from the pod foam. Reglued and retaped and all is well. Yesterday i went to fly my Spitfire, 20+ flights and no crashes and it has the same plastic mount, as I throttled up for launch the motor pulled free. Held back by the power leads it swung into the wing and chewed it up and broke prop before I could throttle down. The plastic had becomne unstuck from the hotglue (no glue on plastic at all) and the tape simply ripped free at the corners. Picture attached.

I repaired it using strapping tape, the kind with fiber filaments inside. Will fly again this morning and will be pre-flight checking this from now on. Never had a problem with the plywood firewalls. Anyone else experiencing glue unsticking on plastic mount?

Remember guy's that the weather affects every thing. you go out to the field or the park in freezing weather, that tape and hot glue are going to get hard and them soft when you heat them up and the glue will not be holding on to your motor.

 

[Hvon11]

I don't see any packing tape over the face of the mount, might just be the lighting though. I had a nasty crash on my Legacy last weekend and they didn't pull out. The motor mounts actually pulled on the skewers holding them into the nacelles and egged out the holes in the nacelles.

I don't see any packing tape over the face of the mount, might just be the lighting though. I had a nasty crash on my Legacy last weekend and they didn't pull out. The motor mounts actually pulled on the skewers holding them into the nacelles and egged out the holes in the nacelles.

The tape pulled free and the only bit remaining was directly between the motor mount and plastic mount. I think the suggestion to rough up the surface good with sand paper is what is needed. That plastic is fairly smooth/slick stuff.

 

[Hvon11]

Remember guy's that the weather affects every thing. you go out to the field or the park in freezing weather, that tape and hot glue are going to get hard and them soft when you heat them up and the glue will not be holding on to your motor.

You make an excellent point. I have been flying and landing these over snow all winter and yesterday was a fairly warm day. 👍

 

[SSgt Duramax]

I feel like foam safe CA could be a good option too, I just don't have any. Standard wood glue also doesn't fair too well, but I haven't used the titebond quick n thick yet on a motor mount. I just use gorilla glue because that is what I have and I know it works.