Control surface gap filling worthwhile?

[David Hall 9]

After seeing the wing control surfaces on many of the top-notch F5J gliders, where the gaps between the ailerons/flaps and wing are filled, I wondered if this was worth doing on my smaller (and cheaper) gliders.

I thought that I could tape (with double sided tape) a strip of plastic sheet (like the clear stuff used for "windows" on boxed toys) over the gap, fixed to the wing side, so that the surface slides beneath. This would create a "step" of a little more than 0.2mm, the thickness of the strip.

Is this worth doing?

Dave.

[flight1]

Yes it can make a difference , even taping the wing to fuselage joint. and elevator join

It is done automatically when using wing hing tape for the smaller gliders no other hing is needed, use both tape and mechanical hinges on fast /high performance planes.

I just use hinge tape on a semi scale ASW 27 3.45m glider on elevator and ailerons (top seface hinge), never any issue which I have replaced every few years as a precaution.

 also on a DLG I have the hinge is part of the top surface skin  moulded in

 

Edited By flight1 on 26/09/2017 17:24:27

[David Hall 9]

Thanks for your post. I didn't really make my question clear enough.

I was thinking of a wing surface, my DLG style esoarer with bagged foam wing for example. The aileron is top hinged and is already sealed there, as would my gliders that use hinge tape for their full length. The gap I meant is the gap on the opposite side to the surface hinge. On this wing, the foam and skin is cut out to allow the surface to move down to around 30 degrees. When in neutral position there is a gap at the wing surface of around 5mm for the length of the aileron, in this case around 60% of the span. Sorry for not being clear.

[flight1]

 bottom gap sealing..  It might not make any difference , it depends on the wing section design,  there is know harm in trying to see if it improves performance. how to go about it without creating more drag than benefit could be difficult.

as mentioned in opening post you probably could  eliminate the 0.2mm step by sanding the wing to accommodate the plasic strip/

 

Edited By flight1 on 26/09/2017 19:05:32

Edited By flight1 on 26/09/2017 19:06:15

[Simon Chaddock]

David

The theory is that the fast moving airflow over the top of the wing is more sensitive to disturbance that the lower surface hence the benefit of a top tape hinge that both smooths and seals the control surface joint.

Also remember that the aileron joint is fairly close to the the wing railing edge by which time the turbulent boundary layer is quite thick so a 'slot' in the wing does not have the same effect as if it was close to the leading edge.

Of course if you set up differential ailerons that have less (or even none!) down than up the underside slot can be much smaller.as well as reducing the effect of aileron adverse yaw.

[John Emms 1]

In my own experience, sealed hinge lines make a massive difference. The simplest form of sealing the hinge line is using hinge tape for the hinge, on the top only with smaller models, and on both sides with models over 1kg.

Yes, the gap is at the trailing edge, and well into the turbulent area, but the real advantage of sealed hinge lines is that by preventing air leaking through the hinge line, the control surface is far more effective. A far more effective control surface needs less deflection for the same effect, and less deflection means less drag.

Hope that helps,

John