Hey guys,

I am about to tape the seam of my wing with fiberglass and epoxy.

The servo mount hole lies right in the seam of the two wing halves. Do I cut this out first, then tape it and then just cut away the fiberglass from the hole? Or do I tape it, and then cut the hole? The latter seems like it would be more difficult as you would have to cut through thick glass...

Thanks!

taped it and cut it out later with a hobby knife, no need to flood it with epoxy if its in the air, any way you need to sand it with a file and servo installment.

You can do it either way. It's your call.

Suggestion: Use only fiberglass resin with the cloth, not epoxy. It will "flow-out" much better than epoxy & is much easier to sand, it's also lighter, & you can "feather it out" Then use a light coat of a finishing glaze or putty to get a real good transition to the balsa.

wing joint is a high stress area i would use 30 min epoxy

Using poly resin on the glass tape will be no weaker than using 30 min epoxy. The wing halves should be joined with 30 min epoxy for sure, but for glassing, the poly is just fine.

Yea, definitly join the wing halves w/ 30 min. epoxy. Just do the tape thing w/ fiberglass & resin. I've had a plane cartwheel (it was the other guys fault- yea, yea, that's the ticket.) the wing broke at the edge of the fiberglass tape. The wing joint & the tapped area was fine

You don't need "thick glass... " For example, the 4*60 instructions has you use a very light weight tape and then CA in down. Let me tell you, that is all you need and then some. Two pounds of epoxy and glass tape is doing nothing for you but adding weight and a dificult place to fair out.

I threw together a replavement wing for an ARF evolution that I put into a fence. I built the wing like the ARF construction, 2 halfs with a dhiedral brace and a locating pin at the TE. Covered and the halfs epoxied together. NO glass tape. I flew that plane for quite a while making a lot of high G moves, mostly by error. I finally totaled out the plane and engine hitting the ground knife edge and hit so hard that the engine was shattered into pieces. The center section of the wing was intact. Now that joining of the halfs wasn't near my better work, and I could see daylight about 45% of the length of the seam between the halfs. This brd was a 60" span with an O.S. 52 Four stroke for power. I can only conclude that the stress on the center section is greatly exagerated. Am I going to quit using the very light glass over the joint, no. But I am now using as thin a glass tape as I can find and then one layer with a bare minimum amount of epoxy or CA to hold it down.

As to cutting out the servo opening, you will get a smoother finish if you glass it and then cut it out. Just be sure to sand down the edges to remove a knife edge that will cut your finger or chafe your servo leads.

Don

Thank you to all of you- you are helping out a beginner. I appreciate it very much.

How far up from the trailing edge should the servo mount be made? The directions weren't very clear here.

I am hoping to accomplish this today. I will let you all know how it went with hopefully some pics too.

Thanks!

The opening should start next to the main spar and go toward the traling edge the length of the servo. Make sure the opeinging leaves clearance so that the sides of the servo case are not rubbing anywhere. I usually wrap the servo case with 3 or 4 layers of masking tape to make sure I am fitting and drilling the mount screws with this clearance locked in. Then remove the tape for final assembly, doing this there is no issue of vibration transmitting and affecting the servo.

This is a foam core wing- so there is no main spar. Ideas?

Thanks

Then you have some measuring and planning to do.... More than likely the thickest portion of the wing will be best as it will allow the servo to be recessed into the wing. You want the linkage to be as short and straight as possible if this is going to torque rods. If this is not the case, then more info is needed. What type of plane? ailerons or flaps? what type of linkage?

What about using finishing epoxy for the glass cloth?

This would work... it will flow better, but will take a while to set and not be tacky. Use sparringly as it does not sand easily. I personally use thin CA or thinned Poly Resin and I use .5oz to .75oz cloth, 1.5" to 4" wide on 25-90 size planes (wider cloth for larger spans).

Make sure what ever you use is foam friendly. Some (all?) poly resin will melt the foam. Some CA also.

i'm still saying 30 min epoxy spread with an old credit card.
it will hold.

my 2 cents

Very, true... test with a piece of foam to check whatever you use unless is says "foam safe" on the bottle.



Well, as with most aspects of the hobby, everyone has thier own way of doing things. I was just pointing out that the use of 30 min epoxy for any added strength is not needed. It will hold very well, no question about it.

I do respect all of your comments ...

I recently glassed the wing joint of a Sky Raider Mk II. I applied 30 min epoxy over SIG glass cloth (type unknown) with the help of a Popsicle stick. I then flowed it out with the old heat gun. The resulting surface covered fairly well without bubbles, holes, or recesses in the epoxy. However, the margins between the epoxy and the uncovered balsa sheeting were all over the place. Do you have any suggestions as to managing the flow of the heated epoxy?

i didnt mean to say one method is better then the other, its the most simple one i could think of.

as for epoxying:
i place masking tape that marks a border, then i spread the epoxy on to the fiberglass tape with a credit card, when satisfied i peel the masking tape off before 30 min time.

if i see that the edges of the fiberglass tape will cause issues i just cut them off before.

it helps when the epoxy resin and hardener were heated in hot water before mixing them.

i moistened the surface with epoxy brush before i put the fiberglass and then epoxy.

for bubbles:
i dont use heat gun any more when fiberglassing, epoxy is a polymer, heating it makes several solidification points which looks like bubbles but some of them are just a different phase.
if it happens let it cure and use some thin CA after you cracked them a little bit.

what is holding the structure is the fibers, the epoxy just hold everything in place attached to the surface.

it could be other fibers too not just fiberglass.

fiberglass has this tendency to stay straight that is the reason the borders of the fiberglass weave cause so much problems, its hard for them to stay bent.

I'll make a note on using a hot water bath for the epoxy components before I mix them together.

Are all your references to "tape" specific to the masking tape used as the border?

Thanks for the revision ...

revised