Wing Repair

[Anonymous]

Peter Brock had a great Dec and Jan with two Eloy wins but Feb was difficult damaging his modela and losing one at MaxMen. He bought a short model and asked the following:

I just got an older mechanical short wing M&K from Austin Gunder. At one tip I have a bit of delaminating at the bottom of the D-box to the ribs. I’ll put some small holes into the carbon at the ribs. Would you use epoxy or Ca? Also, what white epoxy paint do you use on the D-box after a repair?

Thank you, Peter

[Anonymous]

Peter,

If the repair is the rib cap to D-box only, I’d cut a small slit in the covering, lift the rib cap and using a .020 wire dipped in thick impact resistant CA, work the CA into the space quickly and press together using wax paper to keep from gluing yourself to the wing.

If the delaminating is in D-box skin to the D-box ribs, the poke thru the CF skin and applying thin CA will work but I avoid this, a. thin CA is brittle and often re-cracks and b. the CA runs between the covering and carbon and looks bad. If the delaminating is within 12 inches of the tip, I have used a 12 inch 1/16 drill to come in from the end. Attach 1/16 tube to a hypo needle. Mark the tube to indicate the location of the ribs. Use thin lamination epoxy, inject measured amount of epoxy into each volume. Use a heat gun to warm the D-box and rotate the wing so the epoxy runs into all the cracks. Position the wing for final cure so the epoxy runs to the area of the original crack. This may be a bit more weight but makes a good repair. I’ve used this at the root, drilled the hole right at the LE inner surface and then inserted a 1/16 dowel after injecting the epoxy. I have also done this at the dihedral joint but makes one hole in the D-box that I patch with CF and fiber glass.

I use epoxy white primer, sprayed on very lightly. For small repairs I have used a piece of foam rubber to dab the primer on. On the last repair I made, I use an old can of Coverite white spray can. OK for small repair but must use a single brush stroke to apply the coving sticky and let it dry several hours below using the hot iron to attach the covering.

Thermals, JIM

[Anonymous]

Hi Jim,
very interesting your advice for repairing dbox/ribs.
I wonder if drilling a small hole at each bay, enough for a neddle to inject fluid epoxy would be better, even to reach ribs along wingspan.
So a weaken panel after hitting the ground could be reinforced avoiding wing flexings.

regards

[Peter Brocks]

Jim, thank for the advise for the repair. I had some delamination of the bottom d-box not only from the ribs but also from the spar in the wing tip of an F1A wing not too far from the dihedral break. Yes, Javier, I put in vertical holes.

This is how I repaired it:
Drilled 1mm holes through the covering into the bottom of the d-box between the ribs.
Warmed and thinned the West System epoxy a bit with Acetone .
Used a Teflon bulb with a pointed piece of 1.2mm SS tubing inserted at the end.
Sucked up small amount of thin epoxy into the bulb and inserted and pumped into the rib bays.
Used a small bent wire to distribute epoxy inside bay.
Used round toothpicks to close the holes.
Clamped lightly
See my picture

The wing tip is now really strong again with just a slight weight gain. Also, the repair is hardly visible.

Thermals, Peter

[Anonymous]

Hi Peter, good job… that was what I meant, never tried yet but need to do it now.
Good flying 😉

[Author]

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