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Improving roll ability on my GP Big Stik 60

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Improving roll ability on my GP Big Stik 60

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Old 02-17-2019, 08:35 AM
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karolh
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Default Improving roll ability on my GP Big Stik 60

Flying my '93' vintage GP Big Stik 60 with it's narrow and scalloped edged strip ailerons I have never been able to achieve satisfactory axial rolls. Now seeing the improved Hangar 9 Big Sticks with their bigger ailerons and good roll ability I am wondering if by increasing the size (area) of my Stik's ailerons it would improve it's ability to roll better.
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Old 02-17-2019, 04:43 PM
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The first question that I have is are you talking about the speed in which the airplane rolls? That really and as speed decays on an upline and you start loosing some aileron authority is about the only thing that the aileron cord is going to affect. To obtain really good axial rolls requires that the airplane be set up correctly at multiple points. It will require some measuring, changing of the wing incidence and most likely a CG change. It will also require a number of test flights. I of course would be more then happy to get into greater detail if you want. I only ask that if I take the time to do so that you are ready to give these things a try.
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Old 02-17-2019, 05:46 PM
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Originally Posted by speedracerntrixie View Post
The first question that I have is are you talking about the speed in which the airplane rolls? That really and as speed decays on an upline and you start loosing some aileron authority is about the only thing that the aileron cord is going to affect. To obtain really good axial rolls requires that the airplane be set up correctly at multiple points. It will require some measuring, changing of the wing incidence and most likely a CG change. It will also require a number of test flights. I of course would be more then happy to get into greater detail if you want. I only ask that if I take the time to do so that you are ready to give these things a try.
Thanks for your response to my query. My Stik's engine, wing and horiz. stab. incidence are currently set at 0.00 deg. with a CG so that inverted flight is almost hands off requiring only a tad of forward stick for level flight but it does roll very slowly. I am quite aware that it's design is not along normal aerobatic lines but I would just like it to roll a bit better than it does, plus the Zenoah G20 engine gives it very good vertical performance. I am quite willing to try any suggestion you may offer as long as it does not include any radical changes as other than this issue it's a very nice, no bad habits plane to fly.

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Old 02-17-2019, 06:03 PM
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Ok, let's adress the ailerons first. Have you measured the throws to make sure the travel is exactly the same for both ailerons up and down? I'm going to assume no. Most guys don't. The first step will be to measure them and adjust them so both ailerons have the exact same travel going upward. Then adjust them so that they have the same travel downward except you want 3/32" less downward movement then upward. This is referred to as aileron differential. It is needed because the aileron deflecting down generates more lift and drag then the upward aileron looses lift and produces drag. The result is when aileron is applied the airplane wants to yaw opposite of the roll direction and pitch up slightly. Second step is to add 1/16" positive wing incidence. The symmetrical airfoil must have some positive AOA in order to generate lift. With a zero zero setting you must add some up trim and you are flying the entire airplane at a positive AOA. That little bit of up trim screws up anything that is not upright level flight. Adding the positive wing incidence will require the CG be moved just a tad forward. Maybe 3/16". The next change would be to add right thrust to the engine if it is not already there. A total of 2 degrees should be fine. This is done to offset the engine torque that wants to constantly pull the airplane to the left.
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Old 02-17-2019, 06:18 PM
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The model already has aileron differential to the tune of 3/16" less down travel and 1.5 deg. of engine right thrust. I will increase the wing incidence as suggested and do a test flight and see how it goes.
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Old 02-17-2019, 06:25 PM
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3/16 is a bit much on differential. It could be part of your problem. Please keep in mind that these are a set of parameters, doing just one will not result in much of a change.
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Old 02-17-2019, 06:33 PM
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Will change the 3/16" to your suggested 3/32". Thanks.
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Old 02-18-2019, 01:44 AM
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I don't think you can say how much differential to put in independent of how many degrees of aileron throw the plane has. Instead, starting with equal up and down movement, pull up to a 45 deg up-line and apply full right aileron. If the plane walks to the right, you have too much down on the left aileron. Conversely, if the plane walks to the left, you have too much up on the right aileron. Repeat the exercise for a left roll.

Also, if you have not sealed the aileron hinge line, doing so can help increase your roll authority.
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Old 02-18-2019, 04:22 AM
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Originally Posted by RBACONS View Post
I don't think you can say how much differential to put in independent of how many degrees of aileron throw the plane has. Instead, starting with equal up and down movement, pull up to a 45 deg up-line and apply full right aileron. If the plane walks to the right, you have too much down on the left aileron. Conversely, if the plane walks to the left, you have too much up on the right aileron. Repeat the exercise for a left roll.

Also, if you have not sealed the aileron hinge line, doing so can help increase your roll authority.
This sounds like a very logical approach, and yes my ailerons are sealed.
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Old 02-18-2019, 04:48 AM
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Good call on sealing the hinge line. For an airplane of that wing area and relitivly small ailerons the 3/32" differential is going to be pretty darned close. You are correct that in order to get it spot on is going to require some flight tests, I mentioned that in my first post.
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Old 02-18-2019, 06:50 AM
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I too recognize that the ailerons are indeed quite small when referenced with modern day designs and that Is why I posted about enlarging them for hopefully increased aileron authority.
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Old 02-18-2019, 05:33 PM
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More roll authority is one thing and roll precision is something else.
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Old 02-19-2019, 06:03 AM
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I do not associate precision flying with Stiks so I guess what I really want to do is to improve it's roll authority as mine is a very slow roller.
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Old 02-19-2019, 04:39 PM
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A well set up Stik will hold its own. In his very early days Chip Hyde flew Pattern with a Stik. As far a roll authority goes, even the smallish ailerons should give you some pretty rapid roll rate unless the aileron servo(s) are not up to the task. You may want to share some farther details about your setup.
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Old 02-20-2019, 05:44 AM
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Originally Posted by speedracerntrixie View Post

A well set up Stik will hold its own. In his very early days Chip Hyde flew Pattern with a Stik. As far a roll authority goes, even the smallish ailerons should give you some pretty rapid roll rate unless the aileron servo(s) are not up to the task. You may want to share some farther details about your setup.
My Stik has been modded a bit and includes dual digital aileron servos rated at 83.0 oz on @ 0.17 secs. on 6.0 volts. The rudder and vert. stab have been enlarged by approx.15%.
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Old 02-20-2019, 09:02 AM
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What are you using for RX and servo power? How long are your servo arms? How long are your control horns? Seperate channel per servo or Y? What is your aileron deflection?
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Old 02-20-2019, 09:53 AM
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Originally Posted by speedracerntrixie View Post
What are you using for RX and servo power? How long are your servo arms? How long are your control horns? Seperate channel per servo or Y? What is your aileron deflection?
Rx and servo power = Life 6.6v 1600 mA battery
Servo arms = 21/32" c/c
Control arms = 1" from surface to c/ pivot point
Seperate channel per servo
Aileron deflections:
Up = 1/2"
Down = 3/8"
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Old 02-20-2019, 11:22 AM
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Looks like you could safely with some aluminum servo arm increase the servo arm to 1 and get more throw. That is provided you have throw maxed out in the TX. Also if you have dialed in s bunch of expo it will seem to slow rate down a bit. .18 servo speed is a bit on the sluggish side as well.
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Old 02-20-2019, 12:30 PM
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Will check on the availability of 1" arms to fit my servos.
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Old 02-21-2019, 05:24 PM
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Originally Posted by speedracerntrixie View Post
Looks like you could safely with some aluminum servo arm increase the servo arm to 1 and get more throw. That is provided you have throw maxed out in the TX. Also if you have dialed in a bunch of expo it will seem to slow rate down a bit. .18 servo speed is a bit on the sluggish side as well.
You suggested in one of your earlier posts of increasing the wing positive incident by 1/16", what would that equate to in degrees, about 1.5 degrees ?
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Old 02-21-2019, 06:57 PM
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More like .75 degrees. The test for this is to trim the airplane to fly level at full throttle and pull to an upline. If the airplane pulls towards its back it will need more positive. If it tucks towards the gear, it has too much. Once the wing incidence, CG , engine thrust and elevator trim are in sync the airplane will do a straight upline and will fly at either 1/2 throttle or full throttle with zero trim change.
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Old 02-22-2019, 04:35 AM
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Originally Posted by speedracerntrixie View Post
More like .75 degrees. The test for this is to trim the airplane to fly level at full throttle and pull to an upline. If the airplane pulls towards its back it will need more positive. If it tucks towards the gear, it has too much. Once the wing incidence, CG , engine thrust and elevator trim are in sync the airplane will do a straight upline and will fly at either 1/2 throttle or full throttle with zero trim change.
Will do this test the next time I go flying. No flying this weekend as it is extremely windy.
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Old 02-22-2019, 07:38 AM
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Here in California we have had rain every weekend for what seems like months. I haven't flown since December 30. I'm sure some of these trimming techniques will improve the performance of your airplane. They are derived from what I have learned by competing in IMAC and pattern. Going through the complete process of trimming a model is a rather long process that requires many test flights and small adjustments but well worth the efforts when done.
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Old 02-22-2019, 10:56 AM
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You maybe wondering that after having my model for so long why just now I am so interested in getting it to fly as best as possible. I have always been just a weekend sport flier and still am, but recently the bug to get ALL my models to fly as best as possible has bitten me. My other gas models, Carl Goldberg Extra 300L and a scratch built 69" span Extra profile using a pair of Redwing MX 11 wings are both fairly well trimmed and fly very well.

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Old 02-22-2019, 03:57 PM
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Not really, I went a couple decades of flying before I really started paying attention to a proper setup and trimming. As long as you are having fun and the airplane meets your expectations then it's all good. When ready you started asking questions so I say " good on you "!
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