Design

[artysophia]

so im using the freedom flight models and the highest time i've gotten so far is 2:10 my plane is climbing, but not very high at all. also, it has a jerky descent. advice or ideas?

[retired1]

Add a lot of information for a decent reply-turns, band length and width. torque if you have it, weight and any thing else..
It sounds like you are approaching a stall in the glide. Read their instructions again on how to adjust.

[InfiniCuber]

So i have been building and built a new plane with a full wingspan and stabilizer. I used to have a 44 cm wingspan and 24 cm stabilizer. Both have the max wing chords. When I first tested my new full design, I got way to much life or something, but the model kept stalling, and no matter where i moved clay or how much i put on, the same thing happened. I used the freedom flight kit and modified it to my design, essentially making the same stabilizer but using the wing parts to separate ribs to my liking and then making it dihedral. I went from getting flights of 1:15 consistently to like 8 seconds. So I put my old wings on the new body with new stab and I've gotten my times up to 1:30 consistently. No lift problem, nothing really. But i want the full one to work, as it has a larger wing area and therefore should increase my times a bit. Any ideas?

[InfiniCuber]

Here is a new design topic for discussion - the bonus wing for state competition, which has a 7 cm chord.

Our team has usually qualified for states, so we decided to start with the 7 cm wing. Our best time under a 19' ceiling is 3:09. But recently, we built a wing with 8 cm chord. Same fuselage, prop, rubber, and the best time is 3:28. Well, the math is pretty easy; this is almost exactly a 10% difference in times. So for us at this point, the chord bonus seems to be a wash.

Just wondering if anyone else has experience with the bonus wing. And also this question: if the times with and without bonus are essentially the same, is there any reason to prefer one over the other. Obviously, we will use the wider one for Regional competition, but is there any other benefit to a larger or smaller wing chord, other than what is shown by the stopwatch?

Dave D.

How are you even getting such high times?? :O

[torqueburner]

so im using the freedom flight models and the highest time i've gotten so far is 2:10 my plane is climbing, but not very high at all. also, it has a jerky descent. advice or ideas?

I wonder if your motorstick is bowing. This would decrease the decalage, which would reduce the lift, which would reduce the climb. (Not necessarily a bad thing if you are flying in a low ceiling.) Then as the motor unwinds, the stick straightens out, and the decalage increases. If there is enough bend, you have a situation where there is too little lift at the beginning of the flight and too much later on.

Dave. D.

[calgoddard]

The wing with the smaller chord will save you some weight, but that is not an issue with a liberal 8 gram minimum weight in WS.

In general, a wing with a higher aspect ratio will be more efficient. However, in WS you are increasing wing loading if you opt for the smaller wing, since you will always use max the wing span permitted under the rules. Whether the wing chord bonus is large enough to make it worth it comes down to the stop watch.

I used to think the wing chord bonus was not worth all the effort. Then, when Nationals were held at the Armory at the University of Illinois one year, a team that put up a 5 minute flight without any bonus was beaten (and won the silver medal) by a team that had an airplane that qualified for the wing chord bonus and won the gold medal. There is a YouTube video of the second place flight. I am not sure you would get a similar result in a low ceiling flying venue.

[jander14indoor]

So i have been building and built a new plane with a full wingspan and stabilizer. I used to have a 44 cm wingspan and 24 cm stabilizer. Both have the max wing chords. When I first tested my new full design, I got way to much life or something, but the model kept stalling, and no matter where i moved clay or how much i put on, the same thing happened. I used the freedom flight kit and modified it to my design, essentially making the same stabilizer but using the wing parts to separate ribs to my liking and then making it dihedral. I went from getting flights of 1:15 consistently to like 8 seconds. So I put my old wings on the new body with new stab and I've gotten my times up to 1:30 consistently. No lift problem, nothing really. But i want the full one to work, as it has a larger wing area and therefore should increase my times a bit. Any ideas?

You don't mention mass, I assume you are close to 8 gm. I also assume trim settings are same, left wing wash in of about 1/8 inch, stab tilt, left side high, 1/2 inch or so, tail boom bent for left turn, prop angled nose down and left a couple of degrees each. Oh, and wing and tail similar angles of attack.

I suspect you are powerstalling. If so, moving the cg won't help. Bowing motorstick typically causes a dive initially, not a climb, when first launched, if it doesn't hit the floor it may start climbing as the torque drops off and the stick straightens bringing the tail up. And since it flies with the basic wing, seems unlikely.

Lets eliminate center of balance or trim stalls first. With the new wings, rubber on the motor, and not wound, or only wound enough to keep it slightly tight on the motor stick, launch straight and level about shoulder height or slightly higher. Don't throw it hard or anything, the idea is to get it to normal gliding speed. Your plane should glide in your normal left term slowly to the floor. If its shows any tendency to point its nose up and stall, move the CG forward SLIGHTLY until the tendency just goes away. If it drops fast, move the cg back until you start seeing stall and move it forward again. I assume you are flying with the wing trailing slightly high (0-4 mm) and stab trailing edge slightly high (0-2 mm)

If it is test gliding OK, start winding, but for now, DON'T wind hard. Wind to maybe 50% of the turns you did previously. How'd it behave? I'd expect maybe a short, slow climb then descend or slower descent than glide test. Increase 10%, try again. Repeat. If at some point you start pulling nose high on launch and then stalling, you are powerstalling. You need more down thrust in your prop. If you already have 2-4 degrees of down thrust, you need to try a smaller (thinner) motor. You have more power than your plane needs. And this makes sense if you are winding same as for the smaller wing. A bigger wing, same mass, needs less power to fly, giving you the opportunity to use longer skinnier motors for more turns and more time.

What is happening with the larger wing is you DO have too much lift or your current prop/motor combination. At launch you have enough power to fly fast enough that your plane has more lift than needed to balance gravity. Nose climbs, more lift, more climb until you are so high an angle of attack that you may look like you are hanging on the prop. But power is dropping off as the motor unwinds and eventually you can't maintain the climb and stall. IF you are lucky you may not hit the floor and start flying normally. If not, you get that short flight you are seeing.

Hope that helps, be confident a bigger wing (same overall mass, that's important) CAN be trimmed to fly longer than a smaller wing.

Regards,
Jeff Anderson
Livonia, MI

[nxtscholar]

To the more experienced fliers out there, I was wondering if any tried a swept wing design. I know that in actual aerodynamics, swept wings are used over straight wings under extremely high speeds i.e. supersonic, but would a swept wing design have any benefit for an indoor free flight model?

[InfiniCuber]

So i have been building and built a new plane with a full wingspan and stabilizer. I used to have a 44 cm wingspan and 24 cm stabilizer. Both have the max wing chords. When I first tested my new full design, I got way to much life or something, but the model kept stalling, and no matter where i moved clay or how much i put on, the same thing happened. I used the freedom flight kit and modified it to my design, essentially making the same stabilizer but using the wing parts to separate ribs to my liking and then making it dihedral. I went from getting flights of 1:15 consistently to like 8 seconds. So I put my old wings on the new body with new stab and I've gotten my times up to 1:30 consistently. No lift problem, nothing really. But i want the full one to work, as it has a larger wing area and therefore should increase my times a bit. Any ideas?

You don't mention mass, I assume you are close to 8 gm. I also assume trim settings are same, left wing wash in of about 1/8 inch, stab tilt, left side high, 1/2 inch or so, tail boom bent for left turn, prop angled nose down and left a couple of degrees each. Oh, and wing and tail similar angles of attack.

I suspect you are powerstalling. If so, moving the cg won't help. Bowing motorstick typically causes a dive initially, not a climb, when first launched, if it doesn't hit the floor it may start climbing as the torque drops off and the stick straightens bringing the tail up. And since it flies with the basic wing, seems unlikely.

Lets eliminate center of balance or trim stalls first. With the new wings, rubber on the motor, and not wound, or only wound enough to keep it slightly tight on the motor stick, launch straight and level about shoulder height or slightly higher. Don't throw it hard or anything, the idea is to get it to normal gliding speed. Your plane should glide in your normal left term slowly to the floor. If its shows any tendency to point its nose up and stall, move the CG forward SLIGHTLY until the tendency just goes away. If it drops fast, move the cg back until you start seeing stall and move it forward again. I assume you are flying with the wing trailing slightly high (0-4 mm) and stab trailing edge slightly high (0-2 mm)

If it is test gliding OK, start winding, but for now, DON'T wind hard. Wind to maybe 50% of the turns you did previously. How'd it behave? I'd expect maybe a short, slow climb then descend or slower descent than glide test. Increase 10%, try again. Repeat. If at some point you start pulling nose high on launch and then stalling, you are powerstalling. You need more down thrust in your prop. If you already have 2-4 degrees of down thrust, you need to try a smaller (thinner) motor. You have more power than your plane needs. And this makes sense if you are winding same as for the smaller wing. A bigger wing, same mass, needs less power to fly, giving you the opportunity to use longer skinnier motors for more turns and more time.

What is happening with the larger wing is you DO have too much lift or your current prop/motor combination. At launch you have enough power to fly fast enough that your plane has more lift than needed to balance gravity. Nose climbs, more lift, more climb until you are so high an angle of attack that you may look like you are hanging on the prop. But power is dropping off as the motor unwinds and eventually you can't maintain the climb and stall. IF you are lucky you may not hit the floor and start flying normally. If not, you get that short flight you are seeing.

Hope that helps, be confident a bigger wing (same overall mass, that's important) CAN be trimmed to fly longer than a smaller wing.

Regards,
Jeff Anderson
Livonia, MI

Ok, thank you very much! I tried changing the angle of attack, it seemed to work better, but the plane seems to turn right instead of left, and I made sure i made it pretty identical to the older, smaller wing (obviously the new one is larger). Also I tried thinner rubber and a larger, flaring prop, and it seemed to be a bit better. But all your info was VERY helpful, so thank you!

[jander14indoor]

If you are turning right instead of left, something isn't right on your basic trim.

Jeff Anderson
Livonia, MI