Mixing question

[Pistolera]

I have yet to fly a plane, or speak with any pilots (precision style flying) that DON'T have some mixing in to cancel out these issues. Even a Carden will generally need something here or there. Can one fly without the mixes....sure! Is it a little easier to fly precision with them....in my opinion Yes!

Bart....I gave up long ago on trying to understand exactly what's going on to cause it. Makes my head hurt . Some models are better and some not so much. With any given plane, CG has an effect on it.

Does a full scale Pitts, Extra, etc have coupling? DamnedifIknow....we just applied the appropriate control inputs to keep the nose where we wanted it! But with RC, why not let the capabilities of the system help us out.....of course once we've fine tuned mechanical stuff (CG, incidences, thrust lines, etc).

I've always had my planes set up so the mixes where active all the time....never saw a reason for turning them off.

 

[thurmma]

what are the aerodynamic forces that are causing the nose to tuck in response to rudder? or is it gyroscopic precession?

@thurmma does it happen regardless of if the rudder input is quick or slow?

just trying to understand what is happening to make the nose tuck with rudder input

The speed of rudder input does not matter. The tucking is consistent.

 

[thurmma]

What Bunky says.....try some washers between your engine and firewall, if you can't move batts etc.

Other than increasing the spinner gap a tad, it's the easiest way to get CG forward.

The engine is already sitting further ahead than the DLE-170 was. The gap is almost 1/4" between the cowl and spinner. I may try to move my batteries a little further ahead and see if that helps.

 

[Pistolera]

Are you running pull-pull on the rudder or servos in the tail?

 

[thurmma]

Are you running pull-pull on the rudder or servos in the tail?

Pull-pull.

 

[Bartman]

The speed of rudder input does not matter. The tucking is consistent.

ok, gyroscopic precession is more of a problem when abrupt attitude changes happen, like when you first start a turn or when a plane lifts its tail or pitches up to take off. it's one of the things that causes the nose to yaw left at takeoff and one of the reasons the WWII fighter guys had to really get on the rudder when they lifted the tail of their planes during the takeoff roll.

if you've ever tried to hold a bicycle wheel that was spinning and then tried to move it around, it's that weird force that doesn't act in the direction you'd expect it to and the spinning propellor is similar with the same affect on the plane as you're trying to maneuver. but it's more pronounced during maneuvers and less pronounced if the movements are gradual. a right yaw if done abruptly would be like pushing forward on the prop left of the prop shaft (directly in front of the left wing) but gyroscopic precession would make it into a force acting on the prop at the top of its arc so it would push the nose towards the landing gear if that makes sense. it's freaky and I tried to find a good youtube video to explain it but they're all junky.

 

[Terryscustom]

I agree with most of this, I mix everything down to foamies because they fly so much better. Once you get the hang of it, only takes a minute. Tail heavy will always pull more to the gear, nose heavy will be less. Also the water line of the engine in relation to the drag surfaces of the plane play a large key (note your 3DHS has a lower wing, more drag below the water line).

One thing I noticed is that you said "the plane is balanced neutral" but you referenced the wing tube. That is not entirely correct, that is a starting point by the mfg. You always need to fine tune it in the air like @Pistolera said. One thing that I do different though, with aerobatic planes when you fly at a 45 degree angle the wings are lifting so it is an indication but not the most accurate. Our aerobatic planes have fully symmetrical wings so they rely on angle of attack in order to fly. Without power or slight angle of attack the wings technically are not lifting at all. With that in mind I find it way more beneficial to test the CG at half throttle, straight and level flight both with and against the wind. See what it does, if the nose falls just slightly then you are just forward of neutral. If it climbs up or stays dead level then you are technically a bit too far tail heavy as the wing is not lifting at all.

Once you learn to balance them and mix them you will really enjoy the planes more. Also make sure that if you balance the plane exactly how you want BEFORE you mix it. Any slight change in CG you will need to re-mix. Also make sure that your mixes are on all the time as the effects are constant and contrary to some peoples understanding you don't need to turn the mixes off on landing.

One other mix you will want is to make sure you trim your rudder, but most dont do it correctly. Pull straight up and make sure you do not have a cross wind. Chop to idle and point the plane straight down with no throttle. Trim the rudder there. Once you do that you will notice that at full throttle uplines your plane will veer off to the right. This is the "P" factor. you can see it on an upline but it is always doing it even on straight and level flight, it messes with high speed passes, uplines, slow rolls....everything. What you do to fix it is add a mix for full throttle to about 2-3% right rudder. Again, not on a switch. Adjust that until your uplines are dead straight and your downlines are dead straight. Again check your mixing but it should be unchanged.

You will be absolutely blown away at how ARF's benefit from these mixes.

 

[orthobird]

mark, also, I do not know if you have mentioned this, but these airplanes are notorious to come out of the factory with the incidence off, sometimes, way off, so check the incidence of both stabs and the wings, and on the wings, at three different areas.

 

[Terryscustom]

Incidence would get worse with speed incrementally. Flat and level full throttle, chop throttle if it dives or climbes or vs. vsa if you are at low speed, flat and level and punch it and it changes attitude. It's either an engine thrust line issue or an incidence issue. Also incidence issues on stabs are easy to tell if your counterbalances are way off from the stab.

 

[thurmma]

I am pretty sure it is not related to incidence. The full throttle chop and excelleration tests produce no ill effects at all. I am thinking I just need to rebalance the plane and set it up just a tad on the nose heavy side and work with it from there