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Jan 05, 2014, 01:58 PM
Hot Dawg Glider Pilot
schrederman's Avatar
Thread OP
Discussion

Sealing


This is a subject I've not seen discussed in any forum for RC gliders, except I saw it mentioned about sealing the canopy on a scale ship the other day. In full-scale, great effort is paid to sealing the aircraft against air leaking into joints and other areas. The old Schweizer 1-35C I used to fly was helped immensely just by adding duct tape over some holes in the trailing edge c-channel in front of the flaps and ailerons... I mean a very noticeable difference. These differences are quite measurable in man-carrying aircraft with the instrumentation available. My PIK-20B was competition sealed and very quiet, and flew very nicely.

So, I have decided to do a little sealing on my 2 Xplorers. It will probably not be too noticeable to the casual observer. A little foam here and there especially in the trailing edge push-rod areas, a little more care in taping, and so on. It can't hurt... Maybe it will help... Any thoughts?
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Jan 05, 2014, 04:01 PM
Mark LSF # 3792
When I tape my wing tips on I always make sure I close the gap from the hinge line to the LE. I also wrap the tape around the LE at least an inch. Most guys seem to do that. I figure that way there is no air migration from the bottom of the wing to the top, until you get to the moving surfaces.

Wonder if it would make a difference to continue the tape all the way to the flap/aileron on the bottom as well? Not many other places on a Supra where you could seal a gap, except for the hatch on a Pro and the aft end of the nose cone on a Classic.
Jan 05, 2014, 04:18 PM
Pure soaring - no motor
Do you know this:
http://www.dg-flugzeugbau.de/index.p...dl-absaugung-e

Sealing the conopy should prevent the deflection of the airflow above the canopy gap (hope im right), but it would be better to have a lower pressure inside the fuse.
Jan 05, 2014, 10:08 PM
Hot Dawg Glider Pilot
schrederman's Avatar
Thread OP
Sealing the canopy area of F3J models would be problematic. From what I remember, any air leaks anywhere caused extra drag. It appears that they are concentrating all of that in one location with the vent as described. This probably prevents the air from going out into the wings and out openings for controls, etc. With our J models, the fuselage to wing junction has little chance of air passing from one to the other, anyway. Perhaps all we really need to do is tape the canopy down, or go back to nose cones... and tape that joint. I have just finished installing the wing servos in my 4-meter X2, and I looked at the possibility of adding seals... I don't think it's worth the effort... I will be taping my joints all the way around as I almost always do...

Enjoy...

Darth X-Fan
Jan 05, 2014, 10:28 PM
Registered User
Larry Jolly's Avatar
Jack,
How do you propose to test your modifications? Chasing air leaks on full size was long championed by Johnson and Moffat.. I am sure it will do something, I am just asking how far you are willing to go to verify your results.. LJ
Jan 06, 2014, 10:02 AM
Hot Dawg Glider Pilot
schrederman's Avatar
Thread OP
Larry... I guess that's really the problem with models. Even with the telemetry, this could be a wild goose chase...
Jan 06, 2014, 01:22 PM
Mark LSF # 3792
Yep, maybe more trouble than it's worth...who's to know with out really good instrumentation? Also, how about not hearing that "whish" on a speed run when you get her all sealed up?
Jan 06, 2014, 01:43 PM
Registered User
Larry

One possible way to test the effectiveness of "sealing" is to quantify the noise made during high speed flight. If the glider is noticeably quieter after "sealing" I would assume the sealing had a positive effect.

On my Xplorer II that I converted for cross country, I noticed during low level high speed flight it was quite loud, especially when ballasted up to 11lbs. I assumed the most likely source for the noise was air escaping from the wing upper surface gap seals.

I added mylar seals that are adhered to the top surface of the ailerons just aft of the wipers. The mylar extends froward over the wipers and is tight up against the underside of upper wing skin and forms a very tight seal. I could not do for the flaps because when extending the flaps more than about 20 degrees the mylar seal would pop out from the underside of the wing. Therefore at the flaps I just added a layer of tape to the surface of the wipers which made for a tighter seal with the underside of the wing skin.

With these modifications the noise made during a high speed pass seemed to be noticeably less.

John
Jan 06, 2014, 03:20 PM
Registered User
Larry Jolly's Avatar
Jack and John.
Many thanks for your replies. I am very interested in being able to test our models..
I was secretly hoping that Jack had come up with some nifty micro instrumentation package that he was about to drop on us.. But yes, a quiet aircraft on a high speed pass is a good start..LJ
Jan 06, 2014, 03:54 PM
Registered User
concreteman's Avatar
Wheres Tuan when you need him????
Jan 07, 2014, 07:50 AM
Registered User
David Cortina's Avatar
I'm sure Jeremy's got some sort of electronics to sort this out, his stuff will test it and then fly it home too!
Jan 07, 2014, 10:26 PM
Stable genius
vespa's Avatar
Dude. A gyro would totally fix that.


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