Trimming Help
 

Hi all. I've been out of pattern for a while but I'm trying to get the hang of it again. I finished a Focus II this spring and am having a time getting it trimmed right. It always wants to pull to the canopy on down lines. It pulls upline fine. I've tried incidence changes, added tail weight until now it will fly inverted with almost no down elevator. The only way I've been able to stop it is to add down elevator to low throttle, but that is messing up straight and level flight when going from no power to powering up after a downline. Does anyone have any advice? Thanks, Michael Medlin.

RE: Trimming Help
 

Reduce down thrust?

It could be that elevator and down thrust are cross trimmed.
Under power the plane triies to pitch nose to belly, which is compensated with up elevator trim.

Just a thought.

Check it by abruptly cutting power to idle at level flight.
See this trimming chart:

http://www.nsrca.org/technical/trimm...mmingChart.pdf

RE: Trimming Help
 

Just mix to get 1-3% down elevator at idle. I never seen a pattern plane that does not require this mix. Try to get back to the original settings recomended for the Focus II.

Vicente "Vince" Bortone

RE: Trimming Help
 

Michael,

Glad to see you are flying again. A couple of % downline mix is not unusual for the newer pattern planes. On my Focus II that my brother Wes is flying now, I think I have 2%. Very nice flying plane,

Archie

RE: Trimming Help
 

Mine requires significantly more push than I'd like when inverted, and also requires significantly more than 2% down mix at idle (although I don't have a mix yet) for downlines, so I am thinking of reducing the wing incidence a little.

Does this sound right? Stop me before I do something idiotic. Again.

RE: Trimming Help
 

How much incidence you have now? I think my Focus was around +0.5 degrees. This was long ago and I could be wrong. If you have a lot more than this will cause the problem you are having.

Good luck,

Vicente "Vince" Bortone

RE: Trimming Help
 

Bob,

If the plane flies fine every where else, but you have to push a little harder inverted try either lowering the amount of expo on down elevator, or increasing the throw slightly if you are already running very low expo. Use the expo and rates to give you the feel you want.

My Focus II that my brother currently has is pretty close to .5 positive

Arch

RE: Trimming Help
 

I don't know for sure what the incidence is because I have only the couple of Robart incidence meters which don't have the resolution to measure, and I have no faith at all in the table top flatness or the airframe straightness (complete lack thereof, actually!). BTW I didn't mention that it is a Focus II ARF, which I often describe as having been assembled at the factory on a Friday afternoon after a 9-Mimosa lunch. It took a LOT of work, guesswork and some luck to get the wings, stab and fin to square up.

So without an absolute baseline, measuring 0.5 deg isn't a realistic proposition. Therefore, I will just try things one at a time and see what happens.

RE: Trimming Help
 

If your uplines are straight then your wings should be fairly close. That is a good place to start anyway. Most people tend to run the same amount of throw for down elevator as they do up, which means the down is going to feel sluggish as it takes a certain amount just to fly level, so I tend to run a little more throw, plus I even run expo to make it more sensitive around neutral so that I'm not having to push harder than I want to.

Arch

RE: Trimming Help
 

Thanks, Arch! I will keep this in mind as well while I work on the trimming.