ThunderGazer Elevator Trim

[Motorman]

With the flaps neutral how much down elevator would you dial into a TunderGazer.

I just discovered I've been flying with up elevator which would explain a few things. I shortened the push rod and now it's about neutral or maybe 1/32" down.

I've heard some planes like 5/16ths down so, wondering where you put your Tundergazer when bench trimming.

How can you tell it's right while flying?


Thanks,
MM

[Clint Ormosen]

Unless someone here has knowledge to the contrary about is model, I'd start at 0-0 and trim from there.

[Brett Buck]

With the flaps neutral how much down elevator would you dial into a TunderGazer.

I just discovered I've been flying with up elevator which would explain a few things. I shortened the push rod and now it's about neutral or maybe 1/32" down.

I've heard some planes like 5/16ths down so, wondering where you put your Tundergazer when bench trimming.

How can you tell it's right while flying?

   I haven't looked at either of Dave's but  would guess 1/8-1/4 to start. Searching out the position that provides the best tracking upright and inverted is certainly one way. At some point , as you move it to "up", the tracking will suddenly go away, this is too much. I suspect that the down direction will start causing it to turn faster outside than inside before you reach the point the tracking degenerates.

    This presumes you have a *conventional* prop. If you have an electric and use a backwards prop, you are on your own.

     Brett

[Motorman]

When you say "tracking upright and inverted" does that mean being able to fly a straight level line or, flying a straight line without being nose up or down?

Thanks for the advise, I'm going to shorten the push rod a little more.


MM

[Motorman]

Ok, went flying a few times. Didn't know where to set neutral LOL. Big difference this thing flys so level and steady compared to before, even inverted is better. One thing, I had to keep feeding down into the handle, plane wanted to jump off the ground. I got it close but still seems to be more pressure on my pinky finger when flying level and needs a tad more input on the outsides. Will it ever get to neutral with a set up like this or will I always have to feed some down into it when flying level?

Thanks,
MM

[Steve Helmick]

Keep adjusting it until it's right! Understand that adjusting the elevator pushrod will probably require a neutral readjustment on the handle. Somewhere in the mix should be a nice groove and equal inside/outside response. The later is critical, or your timing and input will get confused at some point and your new plane will be history.  Steve

[Dan McEntee]

     5/16" Down elevator at neutral handle??? With flaps level?  Never heard of such a thing. I subscribe to the Bob Whitely method of 1 degree positive incidence in the stabilizer, and elevator is neutral with the flaps.  Every model I have built and bench trimmed this way has always flown right off the board with no hunting or tracking issues. It was in a list that he called, "Things That Always Work" that was in Stunt News years ago, and has been mentioned on the forums numerous times. The rest of the drill is 1 degree down thrust and one degree right thrust. Basic balance and tip weight during bench trimming will usually yield a model capable of the pattern on the first flight. There are probably other opinions on this and your mileage may vary an all that jazz, but this is what has been working for me.
   Type at you later,
    Dan McEntee

[Brett Buck]

Ok, went flying a few times. Didn't know where to set neutral LOL. Big difference this thing flys so level and steady compared to before, even inverted is better. One thing, I had to keep feeding down into the handle, plane wanted to jump off the ground. I got it close but still seems to be more pressure on my pinky finger when flying level and needs a tad more input on the outsides. Will it ever get to neutral with a set up like this or will I always have to feed some down into it when flying level?

   Adjust the handle neutral to remove the bias. This will probably have to change slightly as you adjust the elevator, but over the range you are adjusting it, it should not be a big neutral shift. You have gone too far on the adjustment when you notice significantly different control force between inside and outside maneuvers. It shouldn't take much.

     Brett

[Ted Fancher]

I.C.? Electric? right or left hand prop rotation?

Ted

[Motorman]

remove

[Brett Buck]

Electric, pusher prop. Why does that matter to elevator trim?

 

  Because I think the effect you are compensating for with down elevator is the largely the result of conventional prop rotation. Other way, who knows and you are on your own. Same process, except that you might have to move the elevator in both directions to seek out the ideal position.

    Almost everyone has gone back to conventional rotation at this point.

    BTW, it's not a "pusher" unless its behind the engine, on a Thundergazer all props are tractor props.

    Brett

[Motorman]

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[Randy Cuberly]

In propeller speak there is the tractor and the pusher, the application doesn't matter. Like a tug boat is still a tug boat even when it's pushing.

MM

UUhhhh...If it was pushing in front of the airplane, the airplane would be going backwards.  I think it's referred to as right or left hand rotation!

Just say'in! 

Randy Cuberly!

[Steve Helmick]

In propeller speak there is the tractor and the pusher, the application doesn't matter. Like a tug boat is still a tug boat even when it's pushing.

MM

That's just totally wrong. Lots of twin engined airplanes have LH & RH rotation prop shafts, and they both pull. A lot of boats have LH & RH rotation prop shafts, and they both push. What you have is a LH propeller, not a pusher. Get used to it!   Steve  

[Brett Buck]

In propeller speak there is the tractor and the pusher, the application doesn't matter. Like a tug boat is still a tug boat even when it's pushing.

   Incorrect. They are labelled that in the modeling world because they assume that all the engines run in the conventional direction.

    Brett

[Howard Rush]

My Impact stunt planes have no stabilizer incidence.  With neutral flaps, elevator downrig is 4 to 5 degrees with conventional props.  It wasn't much different with backwards props.   

[Mark Scarborough]

My Impact stunt planes have no stabilizer incidence.  With neutral flaps, elevator downrig is 4 to 5 degrees with conventional props.  It wasn't much different with backwards props.   

Howard,, technically should this not read,, " Myh Impact Stunt Planes have no INTENDED Stabilizer incidence"? I mean, any angular variation from the zero datum line would be incidence whether you put it there on purpose or not, and from what my Geomotry memory says, any angular variation would be incidence even if it is minutely small......

 

[Ted Fancher]

Oops.  Should have added to my questions in the previous post:  Did you build your Thundergeezer with positive incidence in the stab as David advocates?  I've never seen the kit plans so don't know if that "feature" was included.

Ted

[tom brightbill]

The plans show a note "1/64 positive incidence" for the stab.  Also, the 12" motor mounts are noted as "1/8" down tilt" from vertical at the front (of course). I think that works out to roughly .7 degree of negative incidence.
I only wish I could build within 1/64---  

[Dan McEntee]

In propeller speak there is the tractor and the pusher, the application doesn't matter. Like a tug boat is still a tug boat even when it's pushing.

MM

   Yes, it does matter. As has been stated, it's left hand or right hand tractor, or left hand or right hand pusher. Only you never see right hand pusher props on IC engines. The direction is determined in relation to the pilot sitting in the cock pit. It's a simple thing, but if someone is working on your full scale airplane and gets left and right confused, it could mean your life.
   Type at you later,
     Dan McEntee

[Ted Fancher]

The plans show a note "1/64 positive incidence" for the stab.  Also, the motor mounts are designed and noted as "1/8" drop" from vertical at the front (of course). I think that works out to roughly .7 degree of negative incidence.
I only wish I could build within 1/64--- 

That's all standard "David" stuff and was detailed in his Stunt News article "Details" a number of years ago...a combination of Bob Whitely's "Things that always work" (down thrust and offset) and some brainstorming by Brett Buck regarding the horizontal effects of gyroscopic precession and/or P-factor resulting from operating in a tethered environment.

Pretty much all of it based on a right hand "tractor" prop and counterclockwise upright flight.

The Whitely part of it (down and out thrust) is probably valid for a left hand rotation prop as well although I've not given it much thought.  The Brett Buck part argues more for the reverse of the positive incidence of the stab (or drooped elevator equivalent I personally prefer as it's adjustable).

In either case it is probably not the best way to align those surfaces when operating with a left hand prop rotation.  Greater minds than mine should give it some thought.

You're on Brett/David/Howie

Ted

[Motorman]

remove

[Steve Helmick]

The LH & RH is per view from the pilot's location. The "P" for "pusher" is on nylon model props because many wouldn't understand what "LH" and "RH" means. A classic case of "dumbing down America". How are 1:1 scale propellers labelled? "LH" & "RH". Check it out.  Steve

[Tim Wescott]

The Paul Walker trim chart suggests that you fly level and eyeball how level the fuselage is, in both upright and inverted.  Adjust the elevator bias so that it's equal in both attitudes, then adjust the flap/elevator ratio until it's level in both attitudes (tweaking the elevator as necessary as you go).  Adjust the handle bias so that the plane "wants" to fly at the same altitude above the deck both upright and inverted.  Repeat as necessary until you're achieving all three criteria as best as can be.

Theoretically when you do this your plane will then "want" to fly the same on inside and outside corners; I don't know 'nuff to know how reliable this is.

[Dan McEntee]

Guys have you seen a Grish Tornado? it says pusher right on the prop. They know it's going on a the front of a reed valve running backwards or a carrier engine with a left hand crank. APC  has it too EP electric pusher, they know it's going on the front of a motor running backwards. These are major propeller designers/manufactures that know what to call a prop. I also design and make my own props but keep my terminology in line with the industry. When you flip start a model prop it goes to the left but you call it a right prop. When I say tractor or pusher you know what it is. Where do you get your info Wikipedia?

MM 

    At the time those props were marketed, there were several main stream application for pusher props, especially for Cox engines on cars like the Prop Rod and Shrike and the little boat they marketed. The left hand props they used on plastic RTF airplanes that used left hand props were marked as such, LH Prop, not as pusher props. Most pusher props were aimed at the R/C air boat operators. They were labeled and marketed as pushers. To operate a "pusher prop" on a typical model airplane engine, you need a reverse rotating crank shaft, and there were next to none offered. That and the fact of the limited use on air boats, and that explains the very limited varieties of diameters and pitches available for left hand and/or pusher props.
   Type at you later,
    Dan McEntee