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General control line discussion => Open Forum => Topic started by: bill rutherford on July 20, 2014, 08:04:48 PM

Title: flap control horns
Post by: bill rutherford on July 20, 2014, 08:04:48 PM

I/8 vs 3/32 control horn wire.
     The last few years I have been using 1/8 control horn wire for the flaps. The only trouble is when you have to twek the flaps it is really hard . For years we all used 3/32 wire and had no problems , even with big flaps like the mustang and bearcat. If the wire is short how much difference could it make? Whatcha think???
    Bill Rutherford

Title: Re: flap control horns
Post by: Tim Wescott on July 20, 2014, 08:10:32 PM

I think many comments will follow.

I do fine with 3/32" wire, but I think my next plane is going to have a Paul Walker style flap tweak mechanism built in, in which case I'll probably go to 1/8" wire for the rigidity.

Title: Re: flap control horns
Post by: Steve Helmick on July 21, 2014, 03:38:19 PM

Somebody needs to figure out how to make CF control horns for flaps and elevators as commonly used in stunters. Howard's CF tube spar flaps might be the first step toward that? Another trick piece to look at is the Yatsenko's 2 pc. stabilizer joiner system. 

Until then, short 3/32 wire horns work, at least if the flaps are not too large, or fuselage/fillets too wide.  H^^ Steve

Title: Re: flap control horns
Post by: bill rutherford on July 21, 2014, 05:13:12 PM

yea that's about what I have been thinking. Keep em short and the3/32 should be just fine. Bill

Title: Re: flap control horns
Post by: Randy Cuberly on July 21, 2014, 05:17:29 PM

Quote from: bill rutherford on July 21, 2014, 05:13:12 PM

yea that's about what I have been thinking. Keep em short and the3/32 should be just fine. Bill

Sorry but I vehemently disagree with this statement for large stunters. 
3/32 horns on the flaps will flex and cause loss of tracking in corners and even bouncing out of hard corners in windy conditions.  Just ask RJ about this!!!

Randy Cuberly

Title: Re: flap control horns
Post by: Steve Helmick on July 22, 2014, 04:11:16 PM

I asked PW, although now he uses two fancy "Igor" flap horns and drives them from the rear. The use of two horns of course means you don't need bigger wire, since they simply must be shorter in the spanwise axis.  y1 Steve

Title: Re: flap control horns
Post by: Howard Rush on July 23, 2014, 12:55:20 PM

See Derek Moran's writeup.  He gives the McMaster-Carr part number for the requisite wire.  I tried ordering it twice and got bent pieces both times, so I'm interested in an alternate source.

Title: Re: flap control horns
Post by: Trostle on July 23, 2014, 07:40:50 PM

A famous multiple Nats winner has been quoted that there is no such thing as a flap that is too stiff.  The same applies to flap horns.  3/32" dia wire for a full size stunter flaps will allow more flex than needs to be acceptable.  If the flaps need to be "tweeked", there are ways to do so.

Keith

Title: Re: flap control horns
Post by: bill rutherford on July 23, 2014, 09:12:20 PM

Thanks guys. I think I will stick with the 1/8 horns but will try to get some of the wire Howard was talking about.   Bill