Halifax Electric Flyers Association

Last week while flying my SHAFT25e I heard what sounded like control surface flutter but on landing did not see anything broken.
Today while holding the wing up to the light it showed that there are two broken ribs and one broken diagonal brace.

I have sent the attached pictures to the designer with some questions. I'm thinking since the breaks are near the TE of the wing that, indeed, the aileron fluttered. It happened while I was steaming along at full bore on a 4S lipo pack, so maybe it was simply overstressed. I had not applied tape to the bottom side of the aileron to close the small hinge gap but will do this after I finish the repair. Each aileron has six c/a hinges and there is no linkage slop.

Bill

Update on the aileron flutter problem...

I repaired the broken ribs, applied tape to the already small aileron gap....flew it again at high speed and heard the flutter sound..landed, no damage, but one of the aileron servo rods was bowed..so I can only assume that the servo (HS81MG) and rod could not hold the aileron steady. So next I will either replace the 5 inch rod with heavier gauge material or maybe slide a cf tube over the rod and apply a few drops of ca. I'm told that if the servo was not a metal gear type (nylon gears) it probably would have stripped. In fairness to the model and the designer, this type of speed was not what he had in mind with these large ailerons.

Bill

I replaced the aileron linkage rods with stiff cf tubes and still heard the flutter sound, so I emailed Bill Stevens about it and here is his response...

Thank you for your question.

What is your motor and prop selection for this model? I'm thinking that with 4S you may simply be overspeeding the airframe. Certainly slop in the linkage can encourage flutter so your servo and associated hardware needs to be slop free.

Ultimately there is a top end for the airframe when built per speck the stall should occur just over 15mph and you should be propped for no more than a theoretical 50mph pitch speed. The only way to increase the top-end potential of this model would be to capture the ailerons by extending the wing tips aft or cutting in the ailerons in 45 degrees from the hinge point at the wing tip.

-Bill S

So, that is an interesting cure for those that are building a new wing ...(which if I continue to overspeed the airframe, I may be doing..!) ...do not let the aileron continue to the wing tip.

Bill

Can you imagine Billy overtaxing an airframe. You did sign your e mail to Bill Stevens as Zoom Zoom Billy did you not. Terry

Shucks...I left that part off..!

Actually I'm finding that the left stick does move and can be quite handy at times..!

I'm also being reminded that the SA Edge is not a speed demon either as it's ailerons are almost identical to the Shaft.

Gotta stick with the Stryker for "my need for speed" I guess..!

Bill

too funny

..another note from Bill Stevens re my aileron flutter,

Bill, I'd suspect Over-speeding.. I run the A30-16M on a 3S 2100 Pro-
Lite V2 with an 12x6 which is considerably slower pitch speed than
what you are running. At WOT I can't induce a flutter. I
disconnected one aileron from the servo linkage just to test this out
and with the servo linkage disconnected I develop flutter in a full
power dive... with linkage back in-place there's no issue. If high
speed is the goal I think I'd mod the aileron by slashing them in from
the wing tip as discussed or simply extend the wing tip to create a
pocket for the aileron.

Bill S.


..guess I should go back to 3S packs..!

Bill

On the weekend I built another wing for the SHAFT...due to trying to "sift" the old wing through "that" tree at Shannon a few months back.

If you have to build a second wing for anything....a wing kit from Stevens-Aero is definitely the way to go...each piece tabs into the next with such precision that the alignment of the wing is maintained.

Since my 4S packs seemed to overstress the first wing, resulting in cracked or broken diagonal truss pieces as shown above, I did a mod and added additional braces to these diagonal pieces which makes the entire wing more rigid without much additional weight.

Bill

Can't keep a SHAFT down for long ....ready to go again with new wing..

Bill