jester_s1

Did my first flight on the Intruder ARF last week. I had. .6 degree of decalage and found that I needed significant down trim to fly level. Am I correct that I need to reduce the decalage setting until the elevator is straight with the stabilizer? I have flown a Kaos in SPA for 5 years now, so I do have the standard trim guides. I know I'll need to check knife edge flying and such also, but if elevator trim is an indicator of how the decalage needs to move, that lets me get it close before I get that rare calm day in Texas to really dial it in.

speedracerntrixie

My Feedback: (29)

You will want to run tests to verify your CG location and measure thrust line before adjusting the wing. I usually set up my airplanes with .5 positive incidence on the bench and have no noticeable elevator trim. The reason for this is the a symmetrical wing has to be flown with a positive AOA. If set to zero you will have to fly the fuse at positive as well.

jester_s1

The Intruder has an adjustable tail, so incidence changes are fairly simple. I'm planning to go through the trim sequence on Saturday. I just asked this to see if this hunch was right so I could go ahead and get it close.

speedracerntrixie

My Feedback: (29)

If your CG and thrust angle is correct then yes an incidence change would be the way to go. Both CG and thrust line will influence elevator trim too. Check those first.

jester_s1

It was a bit nose heavy on the first flight, which I've moved back a little, and it still needed down trim. I didn't check the thrust line, but I'd be surprised if it were that far off. I'll test fly it again tomorrow and get the CG right then the thrustline, then the incidence. Thanks for the help.

TFF

Don't move the stab an equal amount to make even. Creep up in it; probably about 1/3 of what is even will be about right.

jester_s1

I got to do some trimming yesterday. I moved the CG back a good way just a little at a time until the plane barely has any weight on the nosewheel. It still falls to the canopy in an inverted 45 upline, so I'm going to get a good measurement today and calculate where it actually is on the MAC before moving it anymore. I tweaked the tail until the trim was just barely down before running out of time. I got the aileron differential right so the rolls are very axial and I don't get any yaw when doing a full roll during an upline. The plane flies smoothly through the maneuvers, but still pulls to the canopy in knife edge. I can mix that out if I need to, but I'm still going to experiment to see if I can straighten that out mechanically.

speedracerntrixie

My Feedback: (29)

It would depend on how hard it pulls to the canopy on the inverted 45 degree upline. I like for it to take roughly 5-7 seconds for it to go from 45 degrees to level. I have found that any farther back then that and the rudder to pitch cross couple ( tucking towards the gear ) gets to be a bit much. You are pitching towards the canopy so I would think you can still come back more. I bet your landings are getting easier too.

jester_s1

It lands very nicely, although it's too light on the nose gear. I'll move the main gear back some once I have the CG sorted out.

speed- At this point the inverted upline looks like a big Cuban 8 when I release the sticks. What was weird was that I got almost no trim change as I moved the CG back and couldn't see a difference in the CG test. One of the other pilots said his Dirty Birdy was that way and then made a sudden change when he reached the neutral point. I still haven't had time to put it on the balancer and see where it actually is, but it has to be close.

speedracerntrixie

My Feedback: (29)

If the weight you are removing has little to no effect then I would call that very nose heavy. Not that I am suggesting removing a bunch of weight. I would continue removing small amounts at a time. Everything you are telling me is leading me to beleive you are still nose heavy. I would suggest measuring out the wing, finding what the mean aerodynamic cord is and then determine what percentage you are at now prior to any adjustments. For that airplane I would expect the ideal CG to be very close to 30%. As you move the CG back your elevator will gain sensitivity, do not mistake this for instability. Just reduce your elevator throw. Thinking of that, it is also a good indicator of forward CG, for the intruder having elevator throw of about 1/2" up and down would be plenty.

jester_s1

I did that last night. And you are right, it was super nose heavy. I'm really suprised the manufacturer suggested such a forward CG, as I can't imagine anyone flying this plane that far forward. I used an online CG calculator that uses the desired static margin to recommend the CG. My trimming that had moved it back an inch from the factory recommendation had it at 15% SM, which is the most forward that is normally recommended for a plane. That agrees nicely with my flight observations that the plane was smooth and stable but still pulling to the canopy and a bit resistant to spinning. I made a hatch and put the battery in the tail then added lead to go about 1/3 of the way between 15% and 5% SM. I also figured out how much more it will take to get to 5%, so next time I fly it I'll be able to find the sweet spot without having to measure anything. It's impressive how big the CG range is on this plane and it still be flyable.

elmshoot

My Feedback: (6)

"Nose heavy Airplanes might fly poorly, but tail heavy planes fly once"
So If I'm importing the plane Ill recommend the fwd CG to make sure there is a reasonable level of success to their airplanes first flight
Keep cranking the stab to make it all trim out with the elevator fared with the stab.
Only change one item per flight other wise you will be chasing your tail on these trims flight.
I've raked the main landing gear back about 15 degrees to add a little weight to the nose gear for taxi purposes.
I temporarily put a reverse rotation Saito 1.00 in my Intruder to build some air time on the engine. What a mess to get it flying straight I've given up and just clumsily add rudder as the need arises.
Sparky

speedracerntrixie

My Feedback: (29)

who said anything about tail heavy?

jester_s1

I totally get suggesting a safely nose heavy setup for the first flight. Any plane ever made (unless it's a lifting tail or some kind of radical tandem wing sort of thing) will fly just fine with a CG at 25% of the MAC or with a 15% static margin. There is no danger whatsoever with that. But the Intruder instructions and the landing gear placement call for it to be even forward of that by about an inch. Nobody is going to be happy with the CG that far forward, so why would they recommend it? The end user locates the battery, chooses the engine and exhaust, and maybe even adds weight based on the recommended CG on any new plane. But then on this one you find out on the first day that it's all wrong and you have to change it. It shows poor product testing and a lack of knowledge about pattern flying on the part of the manufacturer. But I'll get it there. I cast some lead weights to permanently mount on the back of the fuselage yesterday and bent the landing gear back so I could keep on moving the CG without it tipping backwards on the runway. The trimming process is tedious, but so worth it.

On the positive, lateral balance looks perfect, as does the thrustline. In testing the other day, I did 4 consecutive loops without touching the ailerons at all. I'd say that's about as good as it gets.

crankpin

My Feedback: (15)

A little negative incidence on the stab, fly it, if it works, epoxy it in. Set on ground, push the tail down, if it settles back up to NG down, dry, go fly.
Crank