In my Sig 1/6th scale Cub, I am about to install the aileron servo, but the two center-most ribs in the wing's center section are too close together to allow the servo to lie down flat against the sheeting. Can I cut out pieces from the center ribs without sacrificing strength? Both sides of the center section will be sheeted, if that matters at all.
Thanks for the help.

Not familiar with the Sig kit, but if you are concerned you can add stiffening ribs lengthwise on the cut ribs. I'm guessing you are taking no more than 1/2 the height of the rib away for the servo cut-out. You're going to have to add a couple basswood or spruce stringers to screw the servo down into anyway (aren't you?), and they will add strength too.

If it's in the center section it will be inside the plane and unobtrusive, so flush is not critical. Are you setting it flush just to clean up the cockpit for inside static scale appearance?

Bear:

Save yourself a lot of bother and frustration. The stock aileron setup in the Sig 1/6 Cub is a bad idea.

Get two Hitec HS-225 servos, and put one in each wing to operate the ailerons.

If it's too late to set it up for dual servos, or you just insist on using a single servo, you can cut the wing srtucture away between the front and rear spars without worry, bettween the rear spar and the trailing edge you can cut it away provided you add material to keep the strength between the rear spar and the wing hold-down screws.

The 1/6 Cub has functional wing struts that carry the majority of the load, so the center structure is not as critical as with a cantilever wing.

Just DO NOT try to fly this plane without the struts. Almost a guaranteed conversion to folding wings.

The plane was designed in the days of silkspan, or silk and dope covering. If you plan to use a film covering you should also use a lot of gussets to reinforce the wing - there are notes on the plan (or in the instruction booklet) about this. Don't ignore it.

When finished you'll have a lot of time in it, but if it's done carefully it is a very nice airplane. But don't try to make it an aerobat.

Hope some of this helps.

Bill.

Wow,
Thanks Bill. You know a lot about this kit. It may, however, be too late to install two aileron servos. I have already added the bellcrank mounts but have not done anything else. The bottom part of the center section is still unsheeted to make it easier to drill any holes if necessary. What are the advantages of using two servos aileron control? I guess it would be much easier to set up, with less linkages and only small holes for the wires. For covering, I am using Sig Koverall applied with Stix-it and then I will seal the grain with WB Polyurethane. Is this an OK setup? I have only the covered the rudder and elevators so I can make changes if I need to. Thanks for your help.

BearcatPilot:

The Hitec HS 225 servos are mini size, with the power of standard servos. Very good fo all-round use if you need the power and have limited space.

If the Sig 1/6 Cub had full span ailerons I'd say go with a single servo, but being scale the linkage makes it a pain. The problem I had with Cubs one and two was aileron centering. They never wanted to come back to the same neutral.

I have Sig 1/6 Cub number three in the box waiting for my attention. And I am debating the use of torque rods for the ailerons, which is something you could probably do from where you are.

It would require drilling holes in the ribs for the wire to go from the aileropns, in line with their pivot, to the center section. The worry I have with torque rods is their long run from the ailerons into the center of the wing, if they are too small in diameter they might act like springs and let the surfaces flutter. If they are large enough to resist this they will be heavy.

I'll most likely stay with the HS 225s. They are only 0.65 wide, laid on their sides they can be fully enclosed in the wing, and with a slight alteration they'll sit on/through the bellcrank mounts.

The Sig Koverall is an excellent choice for covering - easy to put on, strong, and not too expensive.

Short history - I mentioned Cub #3 waiting in the box. My number one Sig Cub is so long gone I remember only that it was destroyed, but not why. Might have been my error, or it might have been one of the kids - had two smaller ones in the house then. Number two was sold when I moved out of Virginia.

A lot of work, but a very nice plane.

Bill.

Why not use a carbon fiber tube for the torque rod?

Minn:

Very good suggestion. I hadn't even thought about CF torque rods.

BCP:

Using CF torque rods looks like the way to go.

Bill.

I come up with one every few tries.

Are carbon fiber rods very expensive? If they are, I don't see much point to using them over two mini servos. If I were to use the CF tubes, how could I connect them as torque rods to the servo, but keep them and the servo hidden? Would it be possible?

BearCat:

Think back to your ARF, and the ailerons. Remember the wires that stuck out of the wing near the center where the aileron servo connected to operate the ailerons? Those were the ends of the torque rods.

With full span ailerons wire torque rods are fine, they're not long enough to twist and wind like a torsion bar.

With the scale "Barn door" ailerons of the Cub, the wire would be long enough to give a problem, but a CF tube, around 1/8" outside would be all you needed.

Definitely less expensive than two mini servos, and lighter than the stock wire and bell crank system. More precise too.

Minn, come on in here and give us one of your famous drawings, please.

Bill.

I understand the concept of the torque rods, but what I meant was, what would you do to get the 90 degree bends in them at the ends? Would you just short pieces of music wire at the ends? Also, where can I find carbon fiber tube? I don't think I have seen it at my LHS. Thanks for all your great information.

Yes, short pieces of music wires in the end will work just fine. I'd draw a pic, but I'm away from my work computer right now, and Photoshop kills my little home computer

(New super-computer coming this week! )

Last question, hopefully for a while. Are the strut braces also functional? I would rather fly without them for simplicity if they are not. And how are they attached to the main struts? Is it just a metal to wood glue joint?
Thanks, you help has been greatly appreciated.

BearCatPilot:

On the Sig 1/6 Cub the midstrut braces are purely decorative, to make the plane more scale. Yes, you can leave them off.

They're attached with little strips of 'glass and resin, or that's the way I did it on my last one. I made sure they would fold down against the struts.

With the struts hinged at their attachment point on the wing, I could unfasten them at the rear gear leg, then when the wing was off I folded the mid strut braces against the struts, and folded the struts against the wing.

Handy for assembly, yet out of the way for transport.

Bill.