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Design => Stunt design => Topic started by: Joe Yau on June 29, 2012, 12:08:10 PM
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Just wondering when setting up the flap/Elev to 1:1 ratio. Do you set it for up elevator or down? As if there are a few degree of down elevator introduced to the set up for to help level flight tracking. There will always be more flaps on up elevator and less on down. So, the question is do I set the 1:1 on up elev or down?
Thanks in advance
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This question is the reason to use adjustable elevator trim in relation to zero flap and to use a system to change elevator/flap movement ratio. Then you can eventually find the trim that works best for your model. There is no recipe book answer. If the model is built to plans, the plans may show some initial settings. These will probably work, but most likely, a better trim situation can be found by trial and error based on your model, any slight alignment differnee built into it, its wing loading and its power train.
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Just wondering when setting up the flap/Elev to 1:1 ratio. Do you set it for up elevator or down? As if there are a few degree of down elevator introduced to the set up for to help level flight tracking. There will always be more flaps on up elevator and less on down. So, the question is do I set the 1:1 on up elev or down?
Thanks in advance
What you are actually setting is the rate of movement the same, not necessarily the absolute up or down motion.
Brett
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I would read 1:1 to mean that if the flaps move up 10 degrees then the elevator moves down 10 degrees. Whether the elevator is also biased is a different issue.
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I took Keith T's advice (also Ted, Bob H., Brett and Paul) and install adj. elev. horns in all my models. I also use an adj. length pushrod to the elevator. It is strange but almost all of my planes have benefited (at least to my liking) from more elevator than flap. Especially if it is fairly "light" for the design. A few have needed a touch of down elev. to neutral flap (shorten the elev. pushrod), but none have needed "up" elev.
Bill
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Another point which is sometimes overlooked is the use of flap and horn being 90 degree's.
These are the funny kink shaped horns you see from Tom Morris and the like - it makes a big difference to control geometry.
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I would read 1:1 to mean that if the flaps move up 10 degrees then the elevator moves down 10 degrees. Whether the elevator is also biased is a different issue.
^ That's exactly what I meant.. and with 2 degree down elev bias will give 2 degree more flaps on up elev = flaps at 12 / up elev at 10 degrees. and flaps at 8 /down elev at 10 degrees.
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^ That's exactly what I meant.. and with 2 degree down elev bias will give 2 degree more flaps on up elev = flaps at 12 / up elev at 10 degrees. and flaps at 8 /down elev at 10 degrees.
HI Joe,
You are correct that the elevator will move at a different "neutral" compared to the flap "neutral" which is why you may have a differential to begin with. That is done to help cure a different rate of turn. BUT, the ratio of movement between the two will still be 1-1. (or whatever ratio you have used)
BIG Bear
RNMM/AMM
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HI Joe,
You are correct that the elevator will move at a different "neutral" compared to the flap "neutral" which is why you may have a differential to begin with. That is done to help cure a different rate of turn. BUT, the ratio of movement between the two will still be 1-1. (or whatever ratio you have used)
BIG Bear
RNMM/AMM
That make sense. Thanks. H^^ I guess the rate will depends on the plane's response to insides turns vs outside.
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Another point which is sometimes overlooked is the use of flap and horn being 90 degree's.
These are the funny kink shaped horns you see from Tom Morris and the like - it makes a big difference to control geometry.
How do you know this?
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Thanks for all the replies! H^^
Just one more question on the flaps.. On a stunter that is on the heavy side. Would more flaps vs Elev (like 1.25 flaps:1:00 Elev etc) help in the corners? or it will just make it hard to fly in the wind.
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Thanks for all the replies! H^^
Just one more question on the flaps.. On a stunter that is on the heavy side. Would more flaps vs Elev (like 1.25 flaps:1:00 Elev etc) help in the corners? or it will just make it hard to fly in the wind.
HI Joe,
Although I e heard of instances where more flap then elevator has been used, it is a rare event. I would not suggest it.
BIG Bear
RNMM/AMM
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Thanks for all the replies! H^^
Just one more question on the flaps.. On a stunter that is on the heavy side. Would more flaps vs Elev (like 1.25 flaps:1:00 Elev etc) help in the corners? or it will just make it hard to fly in the wind.
Maybe, you just have to try it and see. One thing I would note is that changing it to 25% more flap is probably WAY too big a change. This adjustment is VERY sensitive.
Al Rabe's method of adding noseweight to require more deflection, and thus you get more lift, is variation on the same theme. More-or-less, it makes the elevator less effective, meaning you have to deflect the elevator more, which moves the flaps more, too, which in turn increases the camber. Changing the flap elevator ratio towards "more flap" also makes the elevator less effective, meaning you deflect it more, which deflects the flap more. WITHOUT the severely negative effects of a far-forward CG that does tend to kill you in the wind.
Brett
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Maybe, you just have to try it and see. One thing I would note is that changing it to 25% more flap is probably WAY too big a change. This adjustment is VERY sensitive.
Al Rabe's method of adding noseweight to require more deflection, and thus you get more lift, is variation on the same theme. More-or-less, it makes the elevator less effective, meaning you have to deflect the elevator more, which moves the flaps more, too, which in turn increases the camber. Changing the flap elevator ratio towards "more flap" also makes the elevator less effective, meaning you deflect it more, which deflects the flap more. WITHOUT the severely negative effects of a far-forward CG that does tend to kill you in the wind.
Brett
I guess I'll give it a try. H^^ It is close as is (1:1), just would like to get the turns more precise & consistent.
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Howard ;
Simply Geometry.. horns which allow as close to 90 degree points offer as close to equal turn from a mechanical standpoint than your traditional Straight horn with 2 holes side by side ( 1:1 )
I suspect you know this.....
I personally run all my horns from Kaz yet I run my own modified Elevator horn which allows me to alter the pivot point geometry in 1/32 increments + or - Which is different from simply having an adjustable pushrod.
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Simply Geometry.. horns which allow as close to 90 degree points offer as close to equal turn from a mechanical standpoint than your traditional Straight horn with 2 holes side by side ( 1:1 )
I suspect you know this.
Everybody seems to "know" this. It's a three-dimensional problem, though, and is weirder than it looks. See http://stunthanger.com/smf/index.php?topic=19875.0 .
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Howard ;
Simply Geometry.. horns which allow as close to 90 degree points offer as close to equal turn from a mechanical standpoint than your traditional Straight horn with 2 holes side by side ( 1:1 )
I suspect you know this.....
I personally run all my horns from Kaz yet I run my own modified Elevator horn which allows me to alter the pivot point geometry in 1/32 increments + or - Which is different from simply having an adjustable pushrod.
Having used both in the same SV ,It has much less affect than people seem to think, matter of fact, setup correctly I don't think anyone could tell you ,100 %,which plane has what controls in them . and most would be guessing
Randy
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Randy :
I will conceed that
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I guess I'll give it a try. H^^ It is close as is (1:1), just would like to get the turns more precise & consistent.
There are a ton of other issues that are more likely to hurt the turn consistency than the flap/elevator ratio. Just the tiniest error in the tipweight or rudder/leadout position will really screw it up.
Brett
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There are a ton of other issues that are more likely to hurt the turn consistency than the flap/elevator ratio. Just the tiniest error in the tipweight or rudder/leadout position will really screw it up.
Brett
Agree.. I'm aware of the LO,TW and rudder has an effect on the turns, and I've made some changes along side.
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Attached is a plot of 90 degree versus vertical horn behavior. Note the difference in response and symmetry.
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Although you included the 3D geometry, you still left out the effect of other parameters that can give either of those curves pretty much whatever shape you want.
Then there's the requirements question. Do you really want linearity or symmetry?
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Attached is a plot of 90 degree versus vertical horn behavior. Note the difference in response and symmetry.
What are the specifics on your bellcrank setup and flap horn setup..ie output distance
Randy
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That was a 4" separation of bellcrank and flap hinge; .75" horn; .5" lower horn pivot than bellcrank.
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Howard, school me again. I have the bellcrank capable of being tilted, flap horn being canted, elevator horn being canted. All points are located 3D including lateral and vertical offset of bellcrank and horns, stabilizer and elevator offset. What am I missing?
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That was a 4" separation of bellcrank and flap hinge; .75" horn; .5" lower horn pivot than bellcrank.
could this be easily shown with a 4 inch wide bellcrank, .75 inch ouput off of the bellcrank,
up to a 1.25 inch flap horn from center flap horn pivot.
elevators are 1 inch off flap horn to 1 inch at elevator horn
Regards
Randy
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Here's what I did: http://stunthanger.com/smf/index.php?topic=19644.0 I gradually figured it out over the course of this thread. There is still some stuff missing, but I don't think it's anything I care about.
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Randy, this is presuming the horizontal stabilizer is not raised relative to the wing centerline. The handle angles mentioned correspond to +/- 45 degrees at the bellcrank. I can modify it to include canted horns if you want.
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Randy, this is presuming the horizontal stabilizer is not raised relative to the wing centerline. The handle angles mentioned correspond to +/- 45 degrees at the bellcrank. I can modify it to include canted horns if you want.
Hi Tom
thanks much, those are very close, my elevator is 3/4 in. above the flap centerline over the 17.5 inches tail moment
, I would need to measure to get the angle but it is small, the flap horn rises 1.inch at the pushrod on the flap , and drops 1 inch at the elevator horn, so there is a slight down angle of the pushrod.
I used canted horns on one of my models and built the same exact one with straight horns, I could tell zero differance, both planes flew just like the other, with weight within 1/2 ounce and CG at the same place, all specs were the same.
Regards
Randy
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Here is the update with a greater range of handle movement. I assume a 5" handle and a 4" separation of bellcrank pivot and flap horn.
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I use a 4 inch handle spacing to match the 4 inch bellcrank and it has just the right amount of movement for my system, I don't know many using 5 inch spacings on their handle, that would be very fast!
I see about 10 degrees of flap/elev. movement in rounds, and not more than 30 degrees in square stuff, There are a few people that use a lot of hand movement and flap movement on slower controls to get more lift from flaps.
There are also a few people I see using large handles and slow controls to turn the more nose heavy ships.
The "feel" of the controls and handle movement , plus the "stick pressure"may account for a lot more than people think
Randy
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New data.
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The "feel" of the controls and handle movement , plus the "stick pressure"may account for a lot more than people think
Yup. I'm working on it. Well, I was until I noticed that contests were coming up.
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My spreadsheet now includes everything on your list but leadout position. Since I am working from the handle, I don't think I need it. Thanks.
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The more I read the more it sounds like the old golf ploy on the first tee: "Do you breathe in or out on your backswing?" Sometimes it is saved until a crucial shot is about to be hit............
H^^
BIG Bear
RNMM/AMM
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I'll be the first to admit that it is mainly a mental exercise ( I didn't have anything else to do with those 300+ hours, anyway). An adjustable pushrod and horns would go a long way to answering any individual question. That being said, I am starting on the Rabe rudder!
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I like to fly with very little stick pressure. I want to concentrate on the model and the shape, not how much force feedback I'm getting.
There are very model's out there setup this way.. Howard has one of them..
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I designed And built a profile with a Veco .45 once. Talk about pull.
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My spreadsheet now includes everything on your list but leadout position. Since I am working from the handle, I don't think I need it. Thanks.
I think the ciphering will show that you do.
Also, I think one should look at the rigid stuff in the airplane as one problem and the handle geometry as another. There's a spring between them. Then Randy's issue can be addressed.
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Good points. I'll keep working.
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I like to fly with very little stick pressure. I want to concentrate on the model and the shape, not how much force feedback I'm getting.
There are very model's out there setup this way.. Howard has one of them..
I also fly with a small amount of "stick pressure" however it is near impossible to fly without stick pressure, You simply cannot keep the plane on track in the rounds and other maneuvers with corners are very very hard to come out of flat.
I setup several ships with as little stick pressure as I could get, by running rearward CGs and pulling the hande overhang way back to my hand. These just go off at angles that you seem to have no control over...sort of like driving a car in reverse at 60 mph.
Then just by adding overhang to the handle the planes would come back and groove, turn flat, come out of corners flat and at 90 degrees, and track in the rounds without trying to tighten up by themselves...marked improvement.
Also with the extremely low pressure setups wind was impossible to fly in, the plane were just too hard to keep on track and fly thru corners with proper exits.
The power steering feel made it too hard to neutralize controls after the end of the maneuvers and in the corners or intersections.
I will also say that some who have told me their planes had no stick pressure...when I flew them ,they all had much more than I fly with.
Stick pressure ,when setup right will have just enough to sort of self neutralize the plane, and as we all know if it is too heavy on the pressure (ie too much overhang) you cannot turn the ship in high winds, and this is the cause of many flying into Terra firma.
Randy
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Randy ; How I deal with stick pressure is well know, and differs vastly from rearward CG, line overhang or any of that. In actual fact my setup is probably very close to yours in handel setup and CG location.
The main difference is I'm running Boost tabs which vastly reduce the force feedback from the Flaps. By reducing this your not fighting the airpressure forcing the flap in the opposite way, which is linked to the Bellcrank which is linked to the lines, which is linked to my handle.
I've flown back to back flights with them active and not active a noticable difference. - I've let severeal people fly my ships in the past and the overall comments are that its strange : Your handle feeling reduces like you have no line tension, but you have tons of pull - its quite unique.
Not for everyone by anymeans : I've flown Top 5 models and they perform excellent - Its just a feel thing, and personal preferance, I flew last year without them, I think in wind it helps more than without.
Again just personal preferance.
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Hi PJ
When I am setup to fly, I do not use a CG rear of what my planes show, I run them on the CG, I only moved to a very far aft CG to test and see how much you can cut the handle stick pressure, also this has nothing to do with line tension, I can get it so there is little to none...not a good thing.
So when the plane is setup for competition use it is not setup that way, I have a small amount of stick pressure to help in the rounds and help keep the corners flat when coming out of the corner, I know about the boost tabs.
Randy