Precision and flutter worry

[whaturi]

i have never flown in an IMAC contest, but i went to my first one as a spectator recently. i fly a lot and when i can't, i fly on the sim. i find that when i fly on the sim, i like to leave it at full thottle for all flat stuff (point rolls, knife edge, slow rolls, snaps), while i would be afraid to do that with my real plane(35% giles). it seems like it is easiest to fly precise when at the fastest speed. snaps also work out much better that way. i have developed the habit of full throttle horozontal flight on the simulator and it really does look better than 3\4 throttle. i lost a 50cc yak early last summer because it fluttered while at full throttle while flat.

my question is how do you guys keep from worrying about flutter? i know about keeping my linkages slop free and using the right servos. is prop pitch selection the main method to get safe full throttle?

it seems to be a difficult problem, mainly because you want the plane to be set up with 45 degree or more 3d throws and then hit the switch for low rates.. since many people like to 3d with their IMAC planes.

hopefully i can drum up some coversation on this so i can be more confident that my baby will not shred herself next time i fly. im sick of going slow for real life snaps. looks like crap.

[ShortBus]

Have you tried not flying your plane like a drag racer?

Throttle management!

[whaturi]

yeah, i've tried it.

i am asking about this because it looks to me like a lot of the IMAC guys use full throttle during things like point rolls, slow rolls, knife edge, knife edge snaps. and i don't mean leaving full throttle the whole time. with 3d capable planes, i have always thought that any full throttle while horozontal is unsafe.

i fly tons of 3d, so i know how to manage throttle. i just want to know how fast is to fast? how do people know?

[DA2000]

I use two different models in the transmitter, one for Imac, one for 3D. To switch to 3D, I pop the balls off the servo arms and screw the horns in ten turns.

The increased mechanical advantage in IMAC mode eases my mind with regard to flutter issues. That gives me about 25 degrees IMAC, 40 or so 3D.

I also use full throttle on the flats for 4 and 8 points with my Dalton 260 as it presents much better.

Lately I find myself leaving it on the IMAC model for 3D anyhow. The plane doesn't waterfall well at the current CG, and I can do enough for a good freestyle (including high alpha rolls and hovering) with 25 degrees.

Dan

[whaturi]

now that makes sense. very cool.

work out a quick change system from IMAC to 3d and don't risk the plane in the process. and better resolution also.

[DA2000]

Just keep it in the back of your mind not to come screaming downhill full throttle in 3D mode.

This is a compromise setup for a single elevator servo per side, and being able to do some moderate 3D with my IMAC plane. For a purpose built 3D monster, I would stick with two per side and about 50-60 degrees of throw.

My .02

[whaturi]

thanks for the advice. very good points.

i am terrified of flutter, and after pulling out of downlines i make sure to observe my speed before adding to much power.

i believe i will set up my giles like you mentioned, with two programs in my radio and change the horns back and forth.

[Kevin Y]

ok my .02

I think finding the right prop will help you get the speed you want. I personally want a prop that will be the same speed in any attitude (upline, downline, or horizontal flight). I try to keep it as slow as possible and as large as possible to give yourself time to breath and setup for you next manuever. Generally on a horizontal line I will be about 1/2 throttle and when I need to do a snap on a horizontal or 45 degree downline I will bring the throttle to about 1/4, this way I tend to get a good consistant snap and dont have to worry about over rotation. For stall turns I always bring the throttle to about 2 clicks above idle and let go of rudder when the airplane is at the knife edge point, this way the tail will not wiggle on the way down. Another thing that a lot of people mess up on is try not to correct with rudder, use a small amount ailerons its a ot less obivious to judges. Say its a windy day and the wind is blowing in towards your face, drop the outboard wing just a little to keep your line. Or if you have a roll on a downline that you under rotate by 10 degrees, wait until you are pulling to horizontal to correct with your ailerons. Make the judges second guess themselves. Pretty much any downline you have you should be basically at idle.

There are lots of secrets to Imac that you will pick up by going to more and more contest and watching the top level pilots fly. Practice, Practice, Practice is what will help you. The other thing is dont just jump right into the upper classes of IMAC right away. There will be some things that you need to learn, like getting ready for unkowns.

As for IMAC and 3D rates I have it setup as

15 degrees elevator for Imac
35-40 degrees elevator for 3d

30 degrees aileron for Imac
40 degrees aileron for 3d

50% of throw of rudder for Imac
100% throw for 3D

As like Dan I actually have been using my IMAC Rates mostly for 3d now. You should not have to worry about flutter if you are using decent equipment and have your mechanical advantage right.

[whaturi]

thanks, i need all the information i can get.