Wright Stuff B

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JasperKota
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Re: Wider Turns

Postby JasperKota » Thu Feb 22, 2018 8:00 pm

Nesh wrote:If your plane is making very short turns. How do you make it do wider turns?

Depends on the method you're using to turn the plane. If you're tilting the stabilizer, tilt it less, if you're tilting the rudder/vertical stabilizer straighten those out. If your propeller is slightly angled, angle it less.
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Re: Wright Stuff B

Postby jgrischow1 » Sat Mar 17, 2018 11:55 pm

So we just got back from Regionals and have had an odd pattern lately. Many of our flights do decent, ~1:20 range. Many flights have kind of an upward trajectory and then start dropping into a slow, shallow, nosedive after a while, like a tilted ring/donut shape, and then hit or skim on the ground. Can't figure out why as we don't see any difference between the OK flights and the bad ones except for after launch. ~7.02 g, .080 rubber, winds/torque close to breaking. Any help appreciated.

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Re: Wright Stuff B

Postby Polar » Tue Mar 20, 2018 3:28 pm

jgrischow1 wrote:So we just got back from Regionals and have had an odd pattern lately. Many of our flights do decent, ~1:20 range. Many flights have kind of an upward trajectory and then start dropping into a slow, shallow, nosedive after a while, like a tilted ring/donut shape, and then hit or skim on the ground. Can't figure out why as we don't see any difference between the OK flights and the bad ones except for after launch. ~7.02 g, .080 rubber, winds/torque close to breaking. Any help appreciated.


The fact that it is nosediving may mean that the plane doesn't have enough lift to sustain itself. How fast is it ascending at the beginning? If it isn't ascending steeply, you may want to adjust the wings or something to give it extra lift so it can sustain the descent.
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Re: Wright Stuff B

Postby Crtomir » Tue Mar 20, 2018 5:04 pm

jgrischow1 wrote:So we just got back from Regionals and have had an odd pattern lately. Many of our flights do decent, ~1:20 range. Many flights have kind of an upward trajectory and then start dropping into a slow, shallow, nosedive after a while, like a tilted ring/donut shape, and then hit or skim on the ground. Can't figure out why as we don't see any difference between the OK flights and the bad ones except for after launch. ~7.02 g, .080 rubber, winds/torque close to breaking. Any help appreciated.


We see that exact same behavior sometimes too. You need to check if your wing is warped. Assuming that your are flying in a left-turn circle (counter clockwise as seen from above), you want the left wing to have slightly more angle of attack than the right wing. By left, I mean the side pointing in to the circle. You can break your wing slightly on the front left side and then re-glue it to have a little bit of an upward direction so that you get slightly more lift on the left side than the right side. This should help balance your plane when flying in a left-turn circle.

Also, pay close attention to your stabilizer. Your stabilizer should be flat or slightly positive angle of attack. If your stabilizer is aimed downward a little (negative angle of attack), it won't always have the effect you want and the effect will change with different plane speeds. Often that is the reason a plane turns nicely when climbing (high speed), but straightens out when descending (low speed). If your stabilizer has a negative angle of attack, change it to a positive angle of attack. That will, in-turn, cause you to nose dive at first, so you need to move the wing more forward on the motor stick and also maybe increase the angle of attack of your wing, but I would try just moving the wing forward 3-4 cm first. Better to stall first and work back than to nose dive first and break your propeller.

So check your wing for warping, check your stabilizer for warping, and check your stabilizer for a positive angle of attack.

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Re: Wright Stuff B

Postby jgrischow1 » Thu Mar 22, 2018 11:30 am

Crtomir wrote:
jgrischow1 wrote:So we just got back from Regionals and have had an odd pattern lately. Many of our flights do decent, ~1:20 range. Many flights have kind of an upward trajectory and then start dropping into a slow, shallow, nosedive after a while, like a tilted ring/donut shape, and then hit or skim on the ground. Can't figure out why as we don't see any difference between the OK flights and the bad ones except for after launch. ~7.02 g, .080 rubber, winds/torque close to breaking. Any help appreciated.


We see that exact same behavior sometimes too. You need to check if your wing is warped. Assuming that your are flying in a left-turn circle (counter clockwise as seen from above), you want the left wing to have slightly more angle of attack than the right wing. By left, I mean the side pointing in to the circle. You can break your wing slightly on the front left side and then re-glue it to have a little bit of an upward direction so that you get slightly more lift on the left side than the right side. This should help balance your plane when flying in a left-turn circle.

Also, pay close attention to your stabilizer. Your stabilizer should be flat or slightly positive angle of attack. If your stabilizer is aimed downward a little (negative angle of attack), it won't always have the effect you want and the effect will change with different plane speeds. Often that is the reason a plane turns nicely when climbing (high speed), but straightens out when descending (low speed). If your stabilizer has a negative angle of attack, change it to a positive angle of attack. That will, in-turn, cause you to nose dive at first, so you need to move the wing more forward on the motor stick and also maybe increase the angle of attack of your wing, but I would try just moving the wing forward 3-4 cm first. Better to stall first and work back than to nose dive first and break your propeller.

So check your wing for warping, check your stabilizer for warping, and check your stabilizer for a positive angle of attack.


Thanks! We will work on that.

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Re: Wright Stuff B

Postby bjt4888 » Fri Mar 23, 2018 12:38 am

Jgrischow,

The flight attitude you are describing is most likely due to inadequate decalage angle. This is the angular difference between the wing and stabilizer incidence angles. This year’s WS design requires about 3.5 degrees of decalage. This can be achieved if the stabilizer incidence is zero degrees (leading edge distance vertical distance from a reference line like the top edge of the motor stick is the same as the trailing edge distance from the same reference line) and the wing incidence is leading edge 1/4” higher than the than the trailing edge from the same reference line (again the fuselage top edge).

This decalage angle will only work though if the other five or six typical trim settings are correct. The other settings, of course, are: center of gravity at about 1.75” forward of the wing TE, left wing washin set to about 1/16” to 1/8”, stabilizer tilt about 2 degrees, tailboom offset for left turn about 2 degrees, thrustline (prop shaft) angled left about 2 degrees and left wing offset about 1/2”.

Use a good propeller like the Ikara symmetrical trimmed. Tie up a 18.5” (or more) motor and wind in 2,800 turns, or more. Back off enough turns to match the ceiling height and fly for 2:30+ in a typical gym.

Brian T.

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Re: Wright Stuff B

Postby jgrischow1 » Fri Mar 23, 2018 2:39 am

bjt4888 wrote:Jgrischow,

The flight attitude you are describing is most likely due to inadequate decalage angle. This is the angular difference between the wing and stabilizer incidence angles. This year’s WS design requires about 3.5 degrees of decalage. This can be achieved if the stabilizer incidence is zero degrees (leading edge distance vertical distance from a reference line like the top edge of the motor stick is the same as the trailing edge distance from the same reference line) and the wing incidence is leading edge 1/4” higher than the than the trailing edge from the same reference line (again the fuselage top edge).

This decalage angle will only work though if the other five or six typical trim settings are correct. The other settings, of course, are: center of gravity at about 1.75” forward of the wing TE, left wing washin set to about 1/16” to 1/8”, stabilizer tilt about 2 degrees, tailboom offset for left turn about 2 degrees, thrustline (prop shaft) angled left about 2 degrees and left wing offset about 1/2”.

Use a good propeller like the Ikara symmetrical trimmed. Tie up a 18.5” (or more) motor and wind in 2,800 turns, or more. Back off enough turns to match the ceiling height and fly for 2:30+ in a typical gym.

Brian T.


Thanks for your reply. You obviously know a lot more than I do, but why does this flight pattern only happen sometimes, and other times we get decent flights, with no noticeable difference in settings?

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Re: Wright Stuff B

Postby bjt4888 » Fri Mar 23, 2018 3:09 am

Probably because your airplane’s static stability margin is inadequate. If you supply more data in your next message, I can run the numbers using a design spreadsheet.

Send this: wing and stabilizer width (chord) and length (span), CG location relative to the wing TE, tail moment arm and nose moment arm length (distances from the wing LE and the nose and distance between the wing TE and the stabilizer LE), wing incidence in inches and stabilizer incidence in inches.

Yes, I’ve been flying free flight model airplanes competitively (and reading philosophy) for over 50 year’s.

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Re: Wright Stuff B

Postby pbjay » Mon Mar 26, 2018 9:19 pm

What is a good time to shoot for when flying your glider? In states, our glider flew for 9-10 seconds and we finished with 19th place.
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Re: Wright Stuff B

Postby jgrischow1 » Fri Mar 30, 2018 4:15 pm

bjt4888 wrote:Probably because your airplane’s static stability margin is inadequate. If you supply more data in your next message, I can run the numbers using a design spreadsheet.

Send this: wing and stabilizer width (chord) and length (span), CG location relative to the wing TE, tail moment arm and nose moment arm length (distances from the wing LE and the nose and distance between the wing TE and the stabilizer LE), wing incidence in inches and stabilizer incidence in inches.

Yes, I’ve been flying free flight model airplanes competitively (and reading philosophy) for over 50 year’s.

Brian T.
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Forgive the lateness of my reply.

Wing Chord: 9.7 cm
Stab Chord: 6.7 cm
Wing Span: 39.1 cm
Stab Span: 19.7 cm
CG: 4 cm behind wing TE
distance from the wing LE and the nose: 11 cm
distance between the wing TE and the stabilizer LE: 41.2 cm
wing incidence in inches: 5/16
stabilizer incidence in inches: 0

Thank you.

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Re: Wright Stuff B

Postby bjt4888 » Fri Mar 30, 2018 8:04 pm

Jgri,

Good job supplying data. Adding up all of the linear fuselagr dimensions supplied your airplane fuselage (including tailboom) is 68.6 cm long, or 27 inches long. This seems very long. Are all of your references to LE and TE correct?

Also, a CG 4 cm behind the TE ( trailing edge) of the wing is very far back from other designs.

Is this your own design?

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Re: Wright Stuff B

Postby jgrischow1 » Fri Mar 30, 2018 8:19 pm

bjt4888 wrote:Jgri,

Good job supplying data. Adding up all of the linear fuselagr dimensions supplied your airplane fuselage (including tailboom) is 68.6 cm long, or 27 inches long. This seems very long. Are all of your references to LE and TE correct?

Also, a CG 4 cm behind the TE ( trailing edge) of the wing is very far back from other designs.

Is this your own design?

Brian T



Measurements are correct. CG has always been pretty far back on our planes relative to what instructions/designs say. Not sure why. My kids are probably using too much glue somewhere.

Design is based off of WLSguy's plans from the Centerville Clinic. Kids follow it as best they can, but probably made some mistakes along the way.

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Re: Wright Stuff B

Postby bjt4888 » Fri Mar 30, 2018 8:21 pm

Jgri,

Sorry, in addition to a response to my question above, I need your airplanes overall weight and I need to know if you have any clay ballast added to the airplane to bring it up to the 7 gram minimum. And, if ballast is used, please indicate where exactly it is attached ( ex. 1 cm back from the nose on the fuselage).

Also, what type of propeller and nose bearing are you using exactly and, if you can weigh the propeller, or propeller/nose bearing and send me the weight, that would be helpful.

Brian T

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Re: Wright Stuff B

Postby bjt4888 » Sat Mar 31, 2018 12:46 am

Jgri,

Sorry, last questions, I promise. Length of the motor stick and length of the tail boom.

Once I have the info, I’ll plug it into the design spreadsheet and be able to give you some useful feedback.

Brian T

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Re: Wright Stuff B

Postby jgrischow1 » Tue Apr 03, 2018 11:09 pm

bjt4888 wrote:Jgri,

Sorry, last questions, I promise. Length of the motor stick and length of the tail boom.

Once I have the info, I’ll plug it into the design spreadsheet and be able to give you some useful feedback.

Brian T


Motor stick is 34.9 cm. Tail boom is 35.1 cm. They are glued together with a 1.5 cm overlap.

bjt4888 wrote:Jgri,

Sorry, in addition to a response to my question above, I need your airplanes overall weight and I need to know if you have any clay ballast added to the airplane to bring it up to the 7 gram minimum. And, if ballast is used, please indicate where exactly it is attached ( ex. 1 cm back from the nose on the fuselage).

Also, what type of propeller and nose bearing are you using exactly and, if you can weigh the propeller, or propeller/nose bearing and send me the weight, that would be helpful.

Brian T


Plane weighs 7.10 g right now. Not sure why; they usually have it at 7.02 ish. They probably re-glued something. I will advise them to take some clay off.

Yes, they use clay ballast. It is right at the CG, so 4 cm behind the TE.

Prop is standard Ikara 15 cm trimmed to 14. Nose/bearing/hook is from FFM. Total weight is .85 g.


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