Repairing cracks and stress fractures.

[Skyboom]

If anyone knows of any products besides glue for repairing stresses in foam aircraft. Something friendly for all types of foam. If there is some sort of mesh to wrap and strengthen weaknesses. Using small carbon rods to strengthen horizontal stabilizer that cracked on the Mig 15.

[xviper]

For small cracks, I use FoamTac and squeeze that into the crack, press the crack closed and wipe up what oozes out. Then I put clear Gorilla tape across the crack. For a clean break, I do the same thing except that I have the advantage of putting the FoamTac on the open surface, put the two pieces together, pull them apart and wait a minute and put them together again. Then apply the clear tape across the break. Cosmetically, it doesn't look so good but by this time, I really don't care. I just want the plane together again and flyable.

[fhhuber]

Depends on where the crack is... but since said its a stress crack its an indication of overloading the structure of the aircraft. Therefore I would assume just glue is not going to last long.

Stress cracks need to be bridged with structure as well as sealed with glue.
Sometimes sticking a bamboo skewer (or a split skewer to get a lighter piece) or CF tube or rod from tip to tip f the horizontal tail-plane for example.
Sometimes clear packing tape or packing tape with fiberglass filaments in it will provide the needed additional structure.

I tend to use either epoxy or Gorilla "Dries White" (fast setting polyurethane foaming glue) The gorilla glue will expand into microscopic crevices in the foam and lock it together better than anything else I have found.
Cover the repaired area with tape while the glue sets up to hold things in place.

I load my models heavy and yank hard on the sticks. So I tend to stress the foam aircraft A LOT. I've had to reglue the strip in the wings of my Dynam P-51 that hold the CF tube in a few times. That strip is now pinned in place with toothpicks along with the tube being glued in with a generous amount of the Gorilla glue. The motor is upgraded from the original to the one from the Me-109, using 4S 3300 mah instead of the OEM recommended 3S 2000 mah. Its heavier... its much faster. and I'll not hesitate to put the sticks in the top-right corner to induce a high G negative snap-roll in the middle of a high speed pass.
Calculated "pitch speed" of the OEM motor and prop is about 70 mph. Calculated pitch speed with the bigger motor and 4 bade prop is 95 mph. (based on full throttle tachometer reading on the ground)