trimming

[Greg L Bahrman]

Might be nice to have a board for trimming or trimming problems only.

[Clint Ormosen]

Ditto.

[De Hill]

If you have the bandwidth, that is a good idea.

[Terry Bolin]

Okay, here we go with the trimming questions: I have a friend.....no really! Who has a 40 size Legacy and it is loose in the overhead 8's. He has tried Moving the lines forward and back and has added tip weight. (still loose) These are just the things he has tried, what have you guys seen and done to correct this problem?
Thanks and Merry Christmas!
Terry Bolin.

[Bill Little]

Okay, here we go with the trimming questions: I have a friend.....no really! Who has a 40 size Legacy and it is loose in the overhead 8's. He has tried Moving the lines forward and back and has added tip weight. (still loose) These are just the things he has tried, what have you guys seen and done to correct this problem?
Thanks and Merry Christmas!
Terry Bolin.

*If* the usual trim tricks have been tried, as you say, and *IF* everything is straight, and *IF* the plane is not flying too slow, and *IF* he is not on way too long lines, then add a degree (maybe two) of out thrust to the engine.

[Dennis Vander Kuur]

My Brodak kit-built Pathfinder was loose overhead. Adding about 1/4 inch rudder offset took care of the problem.
DennisV

[john e. holliday]

With as many flights as Emmy and I had on the Brodak Mauler with the B-25 I happened to notice it turning in on takeoff just a little bit.  Put a washer under the front of the mounting lug corrected that.  Of course I never paid attention to the overheads until she started doing wingovers and loops.  She has quit complaining about my needle settings now.  DOC Holliday

[Terry Bolin]

This last summer My Nobler was loose in the overhead 8's. Ended up fixing the problem by using a APC 10X6 prop instead of the wood 10x6 prop that was on it!
Ken Nash just told me he fixed his new Legacy being loose in the overhead manuevers by moving the rudder to less offset. It worked for him.  Go figure!

[Bill Little]

This last summer My Nobler was loose in the overhead 8's. Ended up fixing the problem by using a APC 10X6 prop instead of the wood 10x6 prop that was on it!
Ken Nash just told me he fixed his new Legacy being loose in the overhead manuevers by moving the rudder to less offset. It worked for him.  Go figure!

Taking OUT rudder offset makes *perfect sense* to help overhead tension!  Rudder offset causes the model to crab, bleeding off airspeed, which (guess what) causes a loss of tension!  Anything that causes yaw is going to cause the plane ot los speed maneuvering, causing less line tension.

Same concept as moving lead outs FORWARD if tension is poor over 45*

[Terry Bolin]

Taking out rudder off set like Bill said actually fixed a overhead 8 problem on a friends Legacy recently. You would think more but the problem was just as discribed above.
See, this thread is a good thing!

[Bill Little]

Taking out rudder off set like Bill said actually fixed a overhead 8 problem on a friends Legacy recently. You would think more but the problem was just as discribed above.
See, this thread is a good thing!

It has been found out that when everything is petty straight, that having the plane fly as close to tangent to the flight path makes for the best overall tension.  That is why so many top echelon pilots use a 0-0-0 set up.  I still like a degree or two of engine out thrust (mainly to make sure I don't have *in* thrust! LOL!! 

I did fly three patterns one day with a Tomahawk and FP20 with a degree or so in thrust.  Even in gusts it didn't behave badly.  And the pattern was recognizable!   (my son found it when he flew it.  He said it seemed a *little* light on the lines.   Didn't bother me!   If I could fly with 0 lbs. line tension I would! 

I am firmly convinced that MOST pilots fly with excessive line tension AND nose weight......

[Terry Bolin]

I agree Bill. After being off the handle for 3 months for winter then going to Ice-0-Lated last weekend. My Vector seem to have way too much line tension. Now I want to move the LO forward to get rid of some of that pull.

[Kim Mortimore]

 

It has been found out that when everything is petty straight, that having the plane fly as close to tangent to the flight path makes for the best overall tension.  That is why so many top echelon pilots use a 0-0-0 set up.  I still like a degree or two of engine out thrust (mainly to make sure I don't have *in* thrust! LOL!! 
....................

I also thought the 0-0-0 thing was fairly universal among The Stunt Gods, but recently I have seen some interesting exceptions. 

I got a set of plans for the Chinese F2B Skywriter and was surprised to see engine offset--a lot of engine offset.  The engine installation is sidewinder, but I don't think there is any connection.

Ted Fancher has said that he builds downthrust into his planes, and Bob Whitely says that a combination of down and out thrust results in a more stable flying airplane.  I don't have the quotes in front of me, so don't want to list exact numbers, cuz sure as I do they will be wrong.   

The fact that very small angles like this are hard to measure doesn't make it easier, but other things do help make it easier, such as Windy clamp mounts (for downthrust on profiles or outthrusht on upright/inverted engines) or R/C mounts which can be shimmed between the mount and firewall with slightly angled shims, allowing adjustments and experimentation.   

Kim Mortimore

[Bill Little]

Hi Kim,

The Skywriter being an '80s Chinese design doesn't really surprise me, nor do Ted's and Bob's set ups.  Both have been at this for decades, and have found what pleases them.  There are more than a bazillion ways to skin a cat.

[Chris Gilbert IRL-1638]

I'd try a different prop, based on last weekends experience, maybe more diameter if you can.

[Bill Little]

I'd try a different prop, based on last weekends experience, maybe more diameter if you can.

Hi Chris,

A prop change can definitely make a huge difference!