Shoulder Mounted Wings - Top Mounted Fuse

[atjurhs]

Hey all,

I have a set of wings that are made to attach at the "shoulders" of a fuse via a wing joiner rod and anti-rotation pins.

I have a fuse that is made to have wings mounted on the top of the pod.

And I want to marry the two together.

I have one idea of how I can do it, but that method may add a fair bit of weight, so I'd like to find out from you all what your ideas would be.

Thanks!

[BigTilly]

Build a carry through wing section that has a spar joiner and bolt blocks to attach the wings to the fuse. As an added bonus, you get a little extra span.

[atjurhs]

Build a carry through wing section that has a spar joiner and bolt blocks to attach the wings to the fuse. As an added bonus, you get a little extra span.

Yep, that's my current plan. I'm looking for ways to build it lite. Right now I'm planning for it to have two pieces of 1/8th inch ply held together with some balsa sticks and a full wrap of 1/16th balsa sheeting, plus a bit of reinforcement where the bolts go through. I'm not at all sure how beefy (structurally strong) it needs to be, but beefy means additional weight, and that I don't want. What's just enough structural material to get by with?

Still, if somebody has another idea, I'm certainly listening.

[BigTilly]

What is the construction of the wing panels themselves?

[atjurhs]

foam, composite cloths and a plywood end rib.

[Phoebusflyer]

What is the wing span? Obviously a 2meter won't generate the forces that a 3 meter would, also do you plan on winching, hi-starting, hand launch or slope fly? All these things will have some bearing on how much "beef" you build the wing box with.

[atjurhs]

2 meter full-house competition zoom to the moon

[BigTilly]

What is the construction of the spar? Aluminum joiner in a composite tube?

[atjurhs]

yep, aluminum joiner going into composite tubes

[BigTilly]

Well, the key here is that the load in your new center section has to get from fuse (where the mass is) to bolts to spar to wing (where the lift is). Fundamentally, your joiner to wing panel joint isn't any different than it would have been for the shoulder mounted wing, so you want to keep that interface the same. The issue is a weight efficient means of getting the load from the bolts to the spar (in this case the aluminum joiner).

It is likely that the "correct" method would be to replicate the construction of the wing (e.g. skinned core) with the joiner built in, and some ply plates to beef up the bolt area. Then the issue is getting the load from the bolts to the joiner, which is a matter of reinforcing that path with glass/carbon.

Not the lightest solution, but remember that this area needs to be as beefy as the wing is, because it has to carry all of the load. You might also consider permanently bonding this area to the wing saddle on the fuse, depending on whether you need access to that area, and if the fuse has been cut there for radio access (bonding to a hole doesn't work!)

[atjurhs]

I was hoping for info a bit more specific in terms of dimensions, probably based on experience or load analysis, something like:

1/8th inch plywood is overkill, use 1/16th with 0.014 CF laminate reinforcement for the ends ribs

and similar comments for the rest of the joiner panel's construction

[T.D.]

Here is how I have done what you are wanting to do and it will take any launch I have thrown at it and btw I've tried the carry through wing section and while it does work it is more complicated that it's worth, adds weight, requires matching the wing roots and IMO is just not worth the time. No drag benifit that I could find either.

I use a 1/8" ply root rib with a partial inner ply doubler that captures the wing rod receiver tube hole and extends 1/2" past the tube hole front and rear.

Wing hold down bolt is a button head 10-24. Rear wing alignment bolt is 4-40 nylon to allow the wing to pivot in a hard landing. Or 4-40 metal if you are not worried about hard landings.

Take a rat tail file and file a vertical slot/hole in the root rib located such that the hold down bolt will just touch the wing rod when it is screwed down on the pod shoulder. Make another vertical slot aft for the alignment bolt.

Set the wing on the fuse and screw the 10-24 bolt into the hanger nut in the wing bolt plate in the fuse/pod, set the wing up square to the tail and make a mark on the pod to locate the nylon alignment bolt then tap the plywood or hard wood wing bolt plate for the nylon bolt. Squirt a bit of CA into the wooden threads to toughen them up and you are done although I would recommend a small metal washer under the 10-24 wing bolt to help spread the load.

It's also a good idea to fare the wing to the pod by putting packing tape on the bottom of the wings and laying a bit of bondo on the pod, then put the wing on and screw it down...when the bondo hardens pop the wing off and sand the bondo pretty. No anti-rotation pins are required.

I've been using this system on two piece wings for years and it works great, my latest wing is 136" and it's held on the fuselage by a single 10-24 bolt.

PS, if you would like a photo let me know.


T.D.

[atjurhs]

Yea Tony, I could use a photo or two or a drawing (btw, it will be for the 2M fuse I just got). I understand the bondo part, but before that I'm having a hard time picturing what you're describing.

THANKS

[T.D.]

Todd, here are a couple of photos' which might help with the V-Tail mounting extension you are working on.

I used 9/16 ID carbon tube which works well with the boom you have. There are two mounting screw holes in the tube and I would test fit/square it to the boom using 4-40 bolts then dissemble, apply some epoxy/cabosil and then re-attach using the screws...in fact I'd leave the screws in after the epoxy has set, unless you want a removable tail.

To set the V-Tail halves at the correct angle (in my case 108 degrees) I cut a template out of 2" foam (think of a V shape cut from foam with the V at the correct angle), put a small bit of double sided tape on the stab halves, stuck them to the foam with the appropriate gap between the stab halves for the 9/16" tube and then glued (with epoxy) the tube to the root of the stab halves.

It helps if you 3-M spray a bit of sand paper to a piece of spare 9/16" tube and sand a relief in the root of the stab half before gluing as it makes it conform nicely to the tube you are gluing them to. Let the epoxy set and then lay up a couple layers of bias 1.4oz. glass top and bottom of the stab/tube joint and you are good to go.


T.D.

[atjurhs]

Perfect Tony! That's exactly what I had in mind.