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Author Topic: FLAP/ELEVATOR MIX ?  (Read 991 times)

Offline Rafael Gonzalez

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FLAP/ELEVATOR MIX ?
« on: March 25, 2011, 06:02:26 AM »
 I have looked for an answer on search and on the web with no definite responses. I know it depends on the plane and on the pilot.
From my experience in R/C and learning to fly at one time, when Flaps are applied, a trim for up elevator is required. This is due to the change in vector force away from the CG/CM. In this change, the vector force is cancelled/moved to a more forward effect by the elevator and its position away from the CG/CM (length moment). I have built a decent quantity of flapped stunters, profile and full fuse. All did not have an adjustable elevator/pushrod on them. They were fixed. The Stiletto I am building has the system.
OK here is the question:
What ratio of mix is the general area to start, 1:1, 1:xx?
I had set up most of my (old and defunct) stunters as 1:1 in my younger years. I find the transition from combat to a stunt ship is quite a different response experience  ???. I am planing to set up my ratio to generate elevator before flap (2-3 deg). Is this a no-no?

Thank you for the help in advance,

Rafael

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Offline Allan Perret

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Re: FLAP/ELEVATOR MIX ?
« Reply #1 on: March 25, 2011, 08:31:52 AM »
Quote from: Rafael Gonzalez on March 25, 2011, 06:02:26 AM
I am planing to set up my ratio to generate elevator before flap (2-3 deg). Is this a no-no?
Not sure what you are talking about here, but it sounds like a no-no to me.
Best Flap:Elevator ratio I think depends on your finished weight, so its good to use the slider type elevator horn to make it adjustable. 
1:1 ratio is most common, but I think less flap is becoming more popular. 
I like a 2:3 ratio or 30° flap and 45° elevator.   
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Offline Randy Ryan

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Re: FLAP/ELEVATOR MIX ?
« Reply #2 on: March 25, 2011, 11:38:46 AM »
Quote from: Rafael Gonzalez on March 25, 2011, 06:02:26 AM
I have looked for an answer on search and on the web with no definite responses. I know it depends on the plane and on the pilot.
From my experience in R/C and learning to fly at one time, when Flaps are applied, a trim for up elevator is required. This is due to the change in vector force away from the CG/CM. In this change, the vector force is cancelled/moved to a more forward effect by the elevator and its position away from the CG/CM (length moment). I have built a decent quantity of flapped stunters, profile and full fuse. All did not have an adjustable elevator/pushrod on them. They were fixed. The Stiletto I am building has the system.
OK here is the question:
What ratio of mix is the general area to start, 1:1, 1:xx?
I had set up most of my (old and defunct) stunters as 1:1 in my younger years. I find the transition from combat to a stunt ship is quite a different response experience  ???. I am planing to set up my ratio to generate elevator before flap (2-3 deg). Is this a no-no?

Thank you for the help in advance,

Rafael






I wouldn't say its a no-no. I designed a completely adjustable system for a GB Nobler and I can reduce deflections to zero, therefore I can get any ratio I want. I can't lead with flaps or elevator, but I'm not sure that's necessary. Unfortunately I haven't had allot of time to play with the Nobler, but the first set point was at 2:1 (elev-flap) and I liked it there. The model is quite light, so I'd expect to use less flap, I just want to find out how much. Experiment, go for it, learn something maybe all of us can use.
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Offline Randy Ryan

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Re: FLAP/ELEVATOR MIX ?
« Reply #3 on: March 26, 2011, 08:19:24 AM »
Here are pics of my "infinitely" adjustable control system. Designed to be used for testing E/F ratios







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Offline Rafael Gonzalez

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Re: FLAP/ELEVATOR MIX ?
« Reply #4 on: March 26, 2011, 07:46:22 PM »
Holy cow Randy!  BW@

That piece is exemplary of design and craftsmanship. Fantastic silver solder work and superb machining.

Hopefully some day you will have some time to create an Excel or similar file with tables on deflection angles.  D>K H^^
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Offline Randy Ryan

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Re: FLAP/ELEVATOR MIX ?
« Reply #5 on: March 26, 2011, 10:40:02 PM »
Thanks Rafael, maybe I'll do that, but don't hold your breath as sporatic as I've been the last few years. I get all pumped for the season that other stuff just seems to get in the way.
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Offline Bill Little

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Re: FLAP/ELEVATOR MIX ?
« Reply #6 on: March 27, 2011, 04:01:31 AM »
Hi Rafael,

1-1 is the standard staring point for most everyone, unless they know from previous builds of the same plane that something different is expected.  If the model is lighter, then it can usually benefit from more elevator than flap.  it does depend on all the variables, especially wing loading and tail volume, but starting at 1-1 seems to always be safe.  If you have an adjustable "slider" horn on the elevator, then you can experiment with more elevator and see what the effect is.  I know that Ted, and others, say a heavier plane will need 1-1 for sure since it will need the wing to generate more lift.  More flap also creates more nose down pitch when the flaps deflect. 

I have not heard of anyone having the elevators start to deflect before the flaps.  So no help there. ???

And, do you mean that the pushrod is going to be "length adjustable"?  That will be effective if you need to bias the elevator, up or down, compared to flap neutral.  Many times a droop is installed on the elevator to equalize inside and outside turn rates since some designs will naturally turn easier inside than outside.  On my son's latest stunter, it appeared to fly a bit "low in the tail" in level flight. abut 1 1/2 turns to shorten the elevator pushrod (droop the elevator) brought the tail up to where the fuselage appeared level in flight.

Personally, I have found that on a light stunter, more elevator throw in relation to flaps (like a 2-3) gives a better turn response.  But on a heavier model closer to 1-1 works best.

Having the slider horn is a good way of finding the effect different flap/elev ratios have on a model, and can be a real tool in trimming.
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Offline Rafael Gonzalez

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Re: FLAP/ELEVATOR MIX ?
« Reply #7 on: March 27, 2011, 01:53:46 PM »
Quote from: Bill Little on March 27, 2011, 04:01:31 AM
Hi Rafael,

1-1 is the standard staring point for most everyone, unless they know from previous builds of the same plane that something different is expected.  If the model is lighter, then it can usually benefit from more elevator than flap.  it does depend on all the variables, especially wing loading and tail volume, but starting at 1-1 seems to always be safe.  If you have an adjustable "slider" horn on the elevator, then you can experiment with more elevator and see what the effect is.  I know that Ted, and others, say a heavier plane will need 1-1 for sure since it will need the wing to generate more lift.  More flap also creates more nose down pitch when the flaps deflect. 

I have not heard of anyone having the elevators start to deflect before the flaps.  So no help there. ???

And, do you mean that the pushrod is going to be "length adjustable"?  That will be effective if you need to bias the elevator, up or down, compared to flap neutral.  Many times a droop is installed on the elevator to equalize inside and outside turn rates since some designs will naturally turn easier inside than outside.  On my son's latest stunter, it appeared to fly a bit "low in the tail" in level flight. abut 1 1/2 turns to shorten the elevator pushrod (droop the elevator) brought the tail up to where the fuselage appeared level in flight.

Personally, I have found that on a light stunter, more elevator throw in relation to flaps (like a 2-3) gives a better turn response.  But on a heavier model closer to 1-1 works best.

Having the slider horn is a good way of finding the effect different flap/elev ratios have on a model, and can be a real tool in trimming.

Thank you!!!

By changing the ratio, the elevator starts to deflect (up) at a higher rate that the flap. In effect, if the flap deflected (dwn) 1 degree, the elevator would respond in 2 degrees (up)counter acting the nose down tendency that would be a 1:2 ratio.
Generally, I have found that as the pushrod is changed closer or further from the pivot point of the horn, the length needs to be adjusted for neutral.  I use engine thrust to adjust any tendencies if I can. I've had models that turn better one way. I've changed the engine thrust and it worked. If the thrust line on a model is above or below the center of the wing, it tends to want to dip if above the wing, or climb if below the wing.
Thank you all for the great help!!! H^^ I'll start safe on a 1:1. I believe my Stiletto is going to be on the "Plus" size   LL~ LL~
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Offline Bill Little

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Re: FLAP/ELEVATOR MIX ?
« Reply #8 on: March 27, 2011, 02:46:21 PM »
I understand the part now about the elevator coming in before the flaps.  Yes, if the horn is adjusted to give more elevator, the flaps will deflect less in that regard.

More or less elevator, given that the lane will turn adequately, seems to be a personal preference in some instances.  Some just like the feel of more of an "elevator turn".  I guess it is a little "quicker turning feel".  I tend to like the feel better, but I am no where near a "great" level, flying wise.

Big Bear
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Offline Rafael Gonzalez

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Re: FLAP/ELEVATOR MIX ?
« Reply #9 on: April 07, 2011, 09:36:04 PM »
Quote from: Bill Little on March 27, 2011, 02:46:21 PM
I understand the part now about the elevator coming in before the flaps.  Yes, if the horn is adjusted to give more elevator, the flaps will deflect less in that regard.

More or less elevator, given that the lane will turn adequately, seems to be a personal preference in some instances.  Some just like the feel of more of an "elevator turn".  I guess it is a little "quicker turning feel".  I tend to like the feel better, but I am no where near a "great" level, flying wise.

Big Bear

Thank you Bill, et all. The part about an "elevator turn" convinced me of the ratio that I will start with. I do not know if it is an illusion but when I fly a stunter (it could be the way I have it trimmed at 1:1) It seems to "rotate" before it starts to turn on an inside or outside maneuver. I have never had the opportunity of someone that is knowledgeable or an expert fly one of my planes. I feel that I am always trimming them as a very quick response to satisfy my "combat" wrist. Since all my previous stunters had fixed 1:1 ratio, I compensated by increasing the tail weight. The Stunter I am building now, has adjustable ratios for the elevator and flaps. I have no idea how it will fly, but I will have plenty of adjustments!

 H^^
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