Mel Francis

Here's an interesting repair, that we managed to pull off, on a composite wing assembly that was damaged in shipment earlier this summer. Otherwise, the wing would have been scrapped, and was able to be returned to full service.

First, the damage pics. Granted, this wasn't a flight-impact hit, but a lot of damage was done due to compression, while in the shipping box.......

Mel Francis

First, the lower skin was removed, by cutting open and peeling the complete lower skin off the bonding strips and ribs. An aluminum wing tube was re-inserted, to aid the return to straightness, and the assembly was left in the sun for a couple of hours, to relax some of the stresses.

Mel Francis

Finally, the new, replacement lower skin was bonded into position and the edges were sanded smooth. The adhesive used for all structural airframe bonds is 3M #8551 Panel bonding adhesive, an automotive product.

These skins are two layers of 4.5oz cloth, with a 2mm layer of coremat between, for a thickness of .080". The overall weight is 2.8 lbs, for a 46" wing assy.

Once the repair was complete, there was no indication of any repair, since this process was somewhat similar to a complete body panel replacement at an autobody shop.

Mike James

Nice job. Thanks for sharing the photos with us. What is the plane?

Mel Francis

This wing is from a small UAV project that I worked on with Jim Prouty, earlier this year. He's hoping to secure a gov. contract for the planes.

Here's a shot of the same aircraft after the wing repair, during pre-delivery flight tests. This unit was subsequently shipped to a university in Australia for geological work.

Mike James

Cool, Mel.

I've received your PM, and will be answering you via email.

SCALECRAFT

My Feedback: (13)

Hi Mel

Is the weight of the wing including the alum tube.

Thanks

Steve

Mel Francis

The wing tube was not part of the weight.

This wing has both inner and outer flaps and ailerons, so that's the weight of the complete, fully hinged assembly, including 3 servo covers.

This certainly isn't as light as a glider or racer wing, being built more to handle equipment payloads.

Randy Etken

My Feedback: (10)

Mel
Is the 3M panel bond stronger than the Epoxy and cabosil mix that is used to join wings now? What is the cost difference, if you know?
Thanks

Mel Francis

Ive done peel tests with this flexible epoxy-based adhesive, and it bends a long way before peeling loose.

It's more expensive than the same volume of straight epoxy with cabosil, but one cartridge goes a long way.

What makes it really attractive, is the much shorter cure time and it's resistance to vibration and stress cracking.

SCALECRAFT

My Feedback: (13)

Thank you Mel

Steve