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Flying Characteristics: Viper Q-500 Pulling up in Turn Number 1:

Q-500 Racing Discuss AMA 428, AMA 424, and any other variants of Quickie 500 racing

Flying Characteristics: Viper Q-500 Pulling up in Turn Number 1:

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Old 04-25-2008, 07:42 PM
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Electriceddie
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Default Flying Characteristics: Viper Q-500 Pulling up in Turn Number 1:

Hi Guys,

I have a question, that I am pretty shure I know the answer, but I need someone to bounce ideas off of.

I was test flying my Viper Q-500 and heading into the wind practicing like on the course.

I was heading into the wind, going towards pylon one .

When I pulled fairly hard around the pylon, she pulled up.

That tells me she probably needs a littl nose weight. - Correct?

I always forget this one - Adding weight to underneath of the low or high wing. (The old Quarter taped under the wing trick), but why and whats the test for each wing.

I know you guys all know it, I just went brain dead and can't remember, so please help me out, why and under which wing and the reason , again. OK?

Thanks Ahead for your patience

Ed




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Old 04-25-2008, 08:12 PM
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daven
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Default RE: Flying Characteristics: Viper Q-500 Pulling up in Turn Number 1:

If your plane is at 90 degrees to the ground and you pull full up and it rolls up out of the turn, you need low (left) wing tip weight.

If it is a small amount you can mix Elevator (master) to Aileron (Slave) to counteract it. That is my preference, but it does add additional drag.
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Old 04-25-2008, 11:34 PM
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Default RE: Flying Characteristics: Viper Q-500 Pulling up in Turn Number 1:

Make sure your rudder trim is good by pulling a couple of big loops to make sure it tracks straight. When the rudder trim is good start adding quarters to the left wing. I prefer dollars my self. Do the loops big because out of balance to the right will effect loops too especially if they are tight.

Denis
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Old 04-26-2008, 01:50 AM
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Kevin Matney
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Default RE: Flying Characteristics: Viper Q-500 Pulling up in Turn Number 1:

I like the loop deal first then, just keep working on CG,move the battery forward a little at at a time.
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Old 04-26-2008, 06:40 AM
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Ed Smith
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Default RE: Flying Characteristics: Viper Q-500 Pulling up in Turn Number 1:

Do as Dave says, left wing tip weight. If the balance point is moved forward the the turn radius will increase. Most racers set up the airplane on the tail heavy side of the CG range to get a sharp turn around Pylon 1.

Note! "On the tail heavy side" not "Tail heavy"

Ed S
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Old 04-26-2008, 10:04 AM
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Bill Vargas
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Default RE: Flying Characteristics: Viper Q-500 Pulling up in Turn Number 1:

You may also want to try, for CG purposes, flying it inverted. If you can let go of the stick while flying up-right straight and level and then flicking over to inverted, with the same result, your CG is about as good as it gets. If the plane dives while inverted, move the battery back,,, visa versa for a climb. Its also good have equal throws on the tail surfaces too [sm=shades_smile.gif]


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Old 04-26-2008, 11:39 AM
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Default RE: Flying Characteristics: Viper Q-500 Pulling up in Turn Number 1:

about 90% of all the planes I see at the races have left wing tip weight.

I like Bill's suggestion of rolling inverted and checking the cg that way. If you get the cg so the plane flys level both upright and inverted , the plane won't drift toward the canapy when you roll up for the turn at #1

You should read Dave Normans speed secrets at the top of this forum. He has a lot of great tips for trimming there!!
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Old 04-26-2008, 12:25 PM
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Default RE: Flying Characteristics: Viper Q-500 Pulling up in Turn Number 1:

I like knife edge flight to get the fore and aft cg right. In knife edge flight release the stick. If the plane bends in toward the top move the cg aft until the plane flys straight. If it bends toward the gear it's tail heavy. If you are flying 424 you can stand to be a little nose heavy but not for 428. Lateral balance normally costs me 2 to 3 metal bucks, quarters for you cheap skates.

Denis
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Old 04-26-2008, 12:52 PM
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Default RE: Flying Characteristics: Viper Q-500 Pulling up in Turn Number 1:

Lead tape from a golf pro shop is thinner, just peel and stick. They use it to weight club heads.
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Old 04-26-2008, 02:31 PM
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Default RE: Flying Characteristics: Viper Q-500 Pulling up in Turn Number 1:

I like knife edge flight to get the fore and aft cg right. In knife edge flight release the stick. If the plane bends in toward the top move the cg aft until the plane flys straight. If it bends toward the gear it's tail heavy.
If the above happens there are two adjustments to be made. Shift the balance point AND retrim the elevator.

Ed S
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Old 04-26-2008, 03:58 PM
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Default RE: Flying Characteristics: Viper Q-500 Pulling up in Turn Number 1:

Hi Guys,

Thanks for all of the replies so far. But I am a bit confused and maybe someone could give a bit more detail on is this.

In Knife egde flight: Why or how, is it aerodynamically correct or what is the aerodynamic principle that is being employed when a Tail heavy plane makes the bottom of the plane tuck in (towards the direction of the gear). What about being nose heavy and the plane if it pulls up (towards the canopy)?

Also where can Dave Normans Speed secrets be found?

Thanks again

Ed
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Old 04-26-2008, 04:23 PM
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Default RE: Flying Characteristics: Viper Q-500 Pulling up in Turn Number 1:

In knife edge, a tail heavy airplane will drift towards the bottom because of the down-elevator trim component that's being used to keep it from climbing during level flight. The opposite is true for nose heavy (up trim causes it to go towards the top). Although that's not to say that "any" well trimmed airplane will fly straight in knife edge, it's generally true with pylon racers and aerobatic airplanes.


I trim different than anybody has mentioned on this thread.

First I trim for straight and level flight, and then I put it on the course and see what it's doing. The first thing I watch is what it's doing in the turns, then I watch the straights.

If it's climbing or diving through the turn, you need to make sure it's a "roll" or a "yaw" that's causing the climb. 95% of time it's a roll, although some airplanes do have a yaw component (particularly if the effective vertical tail area is too small...or if the V tails don't have equal throws). If it's a roll, I use tip weight to correct it (change, golf club tape, whatever you have..but I prefer the tape as it's not as thick). I've only had a couple Q40's have a yaw, and I used a couple of percent of rudder mixed with elevator to correct it. The Proud Bird that Jim Allen and myself fly did it when we first started flying it. I added about half an inch to the top of the fin when we re-did the mold and corrected the yaw issue. It's now available from Fly Fast Composites (www.flyfastcomposites.com).

I fine-tune the CG based simply on flying the course. I don't worry about inverted flight, ect. Personally I don't like my airplanes to go "straight" on the course, I like them to come in slightly on the course, while rolled up about 60 degrees. If it's coming in too much for me, I move the CG back slightly, or I move it forward if it's flying too straight on the straights.

After any adjustments, I then go back and make sure the airplane will fly straight and level. You should get the airplane to fly the course correctly...AND be able to fly straight and level.

I find that if I fly the straights too straight, I'm in the turn too much and loose too much speed (you have to make a full 180 degree turn, where I'm probably in a turn 160 degrees or so)...The longer you're pulling elevator, the more you're slowing down. Hense, slower lap times, and losing heats. Another by-product of not going dead straight is it's easier to make corrections if you come out of a turn too early or too late. If I'm too late getting off the elevator in a turn, I roll out more, and go straighter down the straightaway, if I'm too early letting off elevator, I leave it banked up more and arc the straight more. I only have to adjust how much aileron I use, and minimize the total control movements. The more control movements you make, the slower you go, especially with elevator movements.

Something else I watch for is adverse yaw with aileron input, and adjust aileron differential to get it close. I don't worry about getting it perfect, but it's got to be close. I've found that most shoulder wing Q500's really should have about 30% more "up" aileron travel than "down". Q40's tend to take a bit less, but most of them can use some differential as well. Without the differential, they may be pulled off heading as you're rolling up for the turn. If the airplane is not rolling up correctly, you're going to be fighting it more.

I believe you need to have the airplane fly straight and level so that when you do have to make a correction (which everybody has to do), you're only trying to get the airplane back to where you need it, rather than fight an airplane that's not only out of position, but now trying to something else because it's only trimmed for on the course.
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Old 04-26-2008, 04:29 PM
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Default RE: Flying Characteristics: Viper Q-500 Pulling up in Turn Number 1:

Thanks for all of the replies so far. But I am a bit confused and maybe someone could give a bit more detail on is this.
Let us start at the beginning. We will assume the incidences are correct.

Balance the airplane at the recomended point. Fly the airplane. If up trim is needed for level flight it is likely the airplane is nose heavy. Roll it inverted. It is still nose heavy, the up trim will now be down trim while inverted. The nose will drop really fast. This will confirm the nose heavy condition. Move the balance point rearward and retrim the elevator. If nothing is changed, while on knife edge, nose heavy and carrying up trim the airplane will come in on the #1 pylon. This will also confirm the nose heavy condition.

All of the above will be reversed if the airplane is tail heavy.

It can take 15-20 flights to get a racer close to racing trim.

Ed S
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Old 04-26-2008, 04:36 PM
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Default RE: Flying Characteristics: Viper Q-500 Pulling up in Turn Number 1:

Dead on Gary!
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Old 04-28-2008, 03:19 PM
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Default RE: Flying Characteristics: Viper Q-500 Pulling up in Turn Number 1:

Hi!
Before you do anything else...Are you sure you have balanced the plane axially !?
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Old 04-28-2008, 04:38 PM
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Lewis S.
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Default RE: Flying Characteristics: Viper Q-500 Pulling up in Turn Number 1:

Hi Eddie,
This is Lewis. I assume you are using sport servos on the Vtail. Check to make sure you are getting the exact same amount of throw on both sides. If the lower V-tail half is getting more throw up, the plane will climb in the turn. Also try the lower wing wieght.

Are you going to Hadley MA on Sunday? Rich and I are going to the polo field on Saturday to check out the planes. If you still have a permit there may you might want to meet us there.

Lewis
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