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General control line discussion => Open Forum => Topic started by: Glenn Quarles on March 17, 2015, 07:01:45 PM

Title: trim help needed
Post by: Glenn Quarles on March 17, 2015, 07:01:45 PM: Friends, I flew my 1/2A Waco yesterday and it acted completely different than the one I built a few years ago. My problem is that the plane flies VERY nose out. The plane is built exactly per the instructions with the lead outs as shown on the plans, about 1/4" rudder offset and I had one thin washer under the front engine mounting bolts for some out thrust. After the first flight I removed the washer to set the motor straight ahead and it didn't help any (not enough to tell anyway). So my question is on what should I do next, move the lead outs forward or get rid of some rudder offset, or both.

Any help will be appreciated!
Glenn
Title: Re: trim help needed
Post by: Tim Wescott on March 17, 2015, 07:29:28 PM: I'd lose the rudder first. Are the leadouts adjustable?
Title: Re: trim help needed
Post by: Akihiro Danjo on March 17, 2015, 07:32:45 PM: Have you checked out the C/G location? It may be too far forward.

Aki
Title: Re: trim help needed
Post by: Glenn Quarles on March 17, 2015, 07:33:56 PM: Quote from: Tim Wescott on March 17, 2015, 07:29:28 PM
I'd lose the rudder first. Are the leadouts adjustable?

Hi Tim, no the lead outs are not adjustable, but it would be easy to do.

Thanks,
Glenn
Title: Re: trim help needed
Post by: Ron Cribbs on March 17, 2015, 07:37:07 PM: Sounds like a leadout issue. By nose out do you mean yaw? Can you see both LG wheels during flight?
Title: Re: trim help needed
Post by: Glenn Quarles on March 17, 2015, 07:39:39 PM: Quote from: Akihiro Danjo on March 17, 2015, 07:32:45 PM
Have you checked out the C/G location? It may be too far forward.

Aki

Hi Aki, yes it is a slight bit nose heavy. I was gonna add a bit of tail weight before the next flight, but I didn't think about it helping the nose out problem.

Thanks!
Glenn
Title: Re: trim help needed
Post by: Glenn Quarles on March 17, 2015, 07:43:25 PM: Quote from: Ron Cribbs on March 17, 2015, 07:37:07 PM
Sounds like a leadout issue. By nose out do you mean yaw? Can you see both LG wheels during flight?

Ron, yes it is yaw. There is no landing gear, but yes the outboard wingtips are visible well behind the inboard.

Glenn
Title: Re: trim help needed
Post by: Tim Wescott on March 17, 2015, 07:58:40 PM: I'd lose the rudder offset and make the leadouts adjustable. Adjustable leadouts on a 1/2A is a bit overboard, but what the hey.

The CG issue is probably a productive line of inquiry, but I suspect it's not the whole answer.
Title: Re: trim help needed
Post by: Glenn Quarles on March 17, 2015, 08:03:46 PM: How much should I move the lead outs? Is there a general rule of thumb for leadout position relative to the bellcrank? Right now the rear leadout is about even with it's position on the bellcrank and the front leadout is about even with the pivot point on the bellcrank.

Glenn
Title: Re: trim help needed
Post by: Howard Rush on March 17, 2015, 09:42:10 PM: Leadout location is a function of CG, not bellcrank position. You can use this to get close: http://www.tulsacl.com/Linelll.html .
Title: Re: trim help needed
Post by: Tim Wescott on March 17, 2015, 10:00:01 PM: The only general rule for leadout position vs. bellcrank is that if the leadouts have a severe bend at the leadout guide, then friction will be increased.

That, however, isn't a big problem unless the bellcrank is absurdly placed.

Set the leadouts correctly with respect to the CG, and you'll be a happy camper.
Title: Re: trim help needed
Post by: Glenn Quarles on March 18, 2015, 07:11:29 AM: Awesome! Thanks for the help guys!

Glenn
Title: Re: trim help needed
Post by: john e. holliday on March 18, 2015, 10:40:56 AM: If the CG is spot on, hang the plane by the lead outs. That will tell you if you need to move them or not.
Title: Re: trim help needed
Post by: Dave_Trible on March 18, 2015, 11:59:05 AM: With the airplane hung by the leadouts on one hook the fuselage should hang nose down 1-2 degrees. The bellcrank location is not important.

Dave