Aileron Balance Weights

[Bil4381]

I'm making Hoerner Wingtips and I'd like to use the aft 1 foot of each tip for mass balance weights screwed to the outboard rib of each aileron.

I have seen photos where others have done this. The weights are in an enclosure which extends forward of the aileron.

My question is to those who have flown their aircraft with this mass balance weight configuration.

If the aileron moves abruptly will the rotational inertia of the weight hanging forward cause the aileron to twist?

I suppose that might cause something like flutter at least temporary flutter.
Bill E

 

[wbpace]

This is a common configuration in general, and the original Sonerais do it this way. The RV's also use an outboard counterweight, their ailerons are broader (albeit only half wingspan) and they don't have any such problems. Even in the alternate configuration where the counterweight is inside the wing, you will still have similar loads (it's only a 6" difference).

I'd be more concerned with torsional loads than flutter...and I am not at all concerned.

My 2 cents, although I do not have a flying plane.

O'Bill

 

[Bil4381]

Bill
Thanks for the reply. My local advisor is a stability augmentation engineer for Bombardier aerospace. He asks what you ask. What is the torsional stiffness and stability?

I'll need to find a non-destructive way to determine that.
Bill E

ps The one wing tip I made looks pretty good to me and it matches up nicely with the original.

 

[wbpace]

Can you post pictures? I'm thinking of doing the same thing.

For stiffness, you could consider doing a full-span hinge, instead of the three separate hinges. that will help. Plus you get a gap seal for free. This is what I plan to do.

This design has been successful forever, so I wouldn't worry about it. Is there a specific concern you have, or just general interest in the educational sense of building a homebuilt?

O'Bill

 

[Bil4381]

Bill
The ailerons have full span piano hinges now. Not sure what they add but they are riveted every inch or two to the rear spar. It must have some stiffness.

I'm trying to remember whether the ailerons have ribs. Ribs make a big difference.

My SII has 400 hours on it. Half of them are by me.

Send me your email by PM and I'll send you photos. My OS is Ubuntu 12.04. & cannot upload to this site.

I placed the one Hoerner wing tip beside the original wingtip. They align nicely. My calculation says each tip will hold 3 US Gals. That's enough to regain the duration I need due to the J3300 engine.
Bill E

 

[Bil4381]

Re: Aileron Balance Weights Now wing tips

Bill,
Did you get my photos of the wingtips? What do you think of them?

They are being filled before paining as I write.

Bill E

 

[wbpace]

Hi Bill,

Yes, I did, thank you, and they are fascinating. I'm really looking forward to seeing the final product. Sorry it took so long to reply. Must have something to do with the 70 hr/week workweeks I've been having lately. Thankfully, that seems to be behind me now.

The ailerons do not have ribs. I was wondering about that as well, but with only a 6 inch width and a max thickness of 1-3/8 inches at the hinge, ribs would be pretty small. So getting 4 or 5 homemade ribs (including the ends) could be hard to get right without inducing a twist. Even the in-wing counterweight doesn't use them.

But I go back to the success of the design. Unless one is really hogging it around the sky doing hard aerobatics (which is not what this design is intended for), then I don't have any worries. Has anyone ever heard of an aileron failure in a Sonerai? I haven't.

O'Bill

 

[pilotsailing]

My plans show ribs in the aileron where the in wing counterweight attaches to.

 

[Bil4381]

There was a Sonerai with just two aileron eye end hinges on each aileron. One hinge broke or somehow came adrift. The aileron flapped about like a palm branch in a storm. He managed to land it somehow.
A good reason to install full length piano hinges.
Bill E

 

[soneraifred]

Just a point or two of clarification: The original Sonerai II with the balance weights at the tips have only two ribs in each aileron, the steel drive rib at the root end, and the aluminum counterbalance rib at the tip. The Sonerai II "S" ailerons each have four ribs, the steel drive rib on the root rib, two aluminum ribs under the counterbalance arm attachment point, and a third aluminum rib on the tip end. The full span aileron on the "S" wing was done more to act as a gap seal than for strength reasons. Three 6" long hinges on each aileron are more than adequate.

 

[wbpace]

Argh, my bad! I looked at the plans, but missed the section A-A' that shows the counterbalance ribs. I knew something didn't seem right. Sorry for the error.

O'Bill

 

[pilotsailing]

That's what this site is all about ! ;D