Wright Stuff C

[lechassin]

There's no replacement for the gym, but a big basement or a large school hallway is useful. We trim our planes in several stages (we use a full motor or a partial motor as has been described in this thread):

1) Initial setup. This year for our bipes, we do not accept anything over 8 grams, set the CG at no more than 24mm from the leading edge, wing incidence shimmed to 2-3mm going right and 4-6mm going left, stab and prop neutral, rudder 5-6mm either way.

2) Test glides with simulated motor weight: gentle push at face level, the motor stick angle should match the plane's descent path and fly for about 20 feet, and it should carve about 1/4 circle (landing 90 degrees off the initial direction). Tweak rudder and CG to get those things.

3) Lightly powered flights (1/2 wound motors) should carve the same path, neither hitting the ceiling nor descending. Motor stick should stay flat or slightly nose up without bobbling. Tweak incidence and CG to get that. I don't have a scientific way to do that, it seems like an art. maybe someone will chime in with better advice.

4) Motor almost out of knots should still have noticeably better flight path than the glide, and even though the plane descends, the motor stick stays flat (does not point down). Tweak CG to get those things and finalize turn radius (we shoot for a 30 foot circle).

5) Outdoor Launch tests (NO wind and a large space or else anticipate losing planes in a trees.,.): wind the motor to launch torque (not initial torque with de-winding), this is easier on the motor and will produce short flights, but with full anticipated launch power, so the launch behavior will be accurate. Estimate altitude and tweak launch torque accordingly. This year most people are having trouble with power stalls or dives, see previous posts to resolve.

6) Get to the gym and confirm altitiude (launch torque).

With these steps, by the time we get to the gym, the plane is mostly trimmed and will fly pretty well right away, so the session is devoted to trying to gain flight time, and is not spent just getting the plane to fly.

[scioly2345]

Hi,
- So I know it’s pretty mid season to have built a Freedom flight kit and started to test it, but I just started flying mine and the turns (clockwise and counterclockwise) are there but there’s minimal power and like not any lift, but it’s a stable flight (and it’s a slow flight which is very good), and also I built it as a biplane.
- Some things I tried without changing rubber band size to create more power and lift is play around with the adjustable wing posts up and down in the red tubes, but that leads to either the no lift steady slow flight, or a stalling flight where it’ll climb, then it won’t have enough power to stay up and the whole plane just falls straight to the ground.
- I also lifted the adjustable pin in the horizontal stabilizer (the one used to change directions) up and down so the stab can assist in the lift, but that usually only helps with the clockwise flight because if I lift the pin in the back the stab leans in the direction that only favors the right or clockwise turn.
- I started with the .065” rubber, but should I try to change either the amount of winds or go to the thicker rubber band for more power?
- (Btw, I LOVE the carbon fiber thing for this kit’s prop). ITS SO DURABLE.
Thanks everyone.

[lechassin]

After you verify good basic construction (unflexing motor stick, flat, unwarped surfaces, prop runs true, etc...) post up some basic parameters like CG location, wing incidence, stab incidence, number of winds and torque initially and after de-winding for launch, prop specs (number of, size of, and angle of the blades).

Some close up pics of the plane and narrated video of the flights (listing parameters listed above), would be very helpful slso.

[calgoddard]

In the previous post lechassin brought up an important point.

I have previously given the following advice on this forum but for some reason it is rarely followed.

If you are having trouble trimming your airplane and seek advice from experts who post on this forum please post a link to a YouTube video of one of your airplane’s flights that exhibits the undesired behavior. Almost everyone has a cell phone these days and can easily take a video and post it to YouTube.

Verbal descriptions of a flight by novices often do not accurately convey the dynamics of a flight.
Here’s a hypothetical example. “When I launch my airplane it starts to climb, and then it just stalls and slides backwards onto the floor.” The airplane could be perfectly fine, but it was just launched at too high of an elevation angle (nose too high). This improper launch would typically be readily visible in a video.

In addition, information such as model weight without rubber, CG location, LE incidence, rudder offset, rubber motor length and weight, torque at launch, etc. would greatly facilitate analysis and advice from experts. If you observe an expert at a flying session giving advice, the expert will almost always hold the student’s airplane and look carefully for warps, wash-in, misalignment, and other relationships of the flying surfaces. In addition, the expert will often examine the thrust angle and manually flex the motor stick to check for adequate stiffness. Unfortunately, these types of physical inspections cannot be done remotely. However, the physical relationship of the components of the air frame can often be indirectly assessed by watching a video of a flight. For example, if the airplane descends at high launch torque but after 15 seconds it begins to climb normally, this behavior probably indicates that the motor stick is bending and producing unwanted positive stab incidence at high torque.

Moreover, some close up still photos of parts of the air frame would also be helpful.

lechassin, I am very impressed by the results you and your son have achieved. Keep up the good work. Good luck at your competition.

[lechassin]

lechassin, I am very impressed by the results you and your son have achieved. Keep up the good work. Good luck at your competition.

Thank you Sir.

The plan is for Luke to wind and launch exactly as we've practiced. With "normal" HVAC he should climb to 20' and get 1'30" both ways, and without HVAC, 25' and 1'45" both ways. He's late home from school, I think he's in the gym re-trimming the back-up plane that I messed with (*fingers crossed*).

Edit: the backup plane is now trimmed the same as the primary, so it was indeed the extra 0.3 grams of repairs that messed things up. I'm glad for that because I couldn't understand why the backup plane needed 1 mm more incidence to cruise (ergo more drag). The backup plane's prop blades are 0.001" thicker and they don't flare as much, so the plane climbs a bit higher and runs out of knots a foot off the ground before landing. We're going to leave things as-is for now but after the invitational there may be improvement with a slightly longer motor. 1'35" to 1'49" depending on HVAC. The backup plane may become the primary plane for regionals.

He did forget to set the rudder once and launched into the wall (again...) so we are definitely making a checklist for this weekend.

[lechassin]

I'm so excited for Luke that I'm posting even though it's still early in the day. I didn't go, mainly to avoid stressing him out with last-minute advice, but I was anxiously awaiting an update. It was a whirlwind pace: he called just after 10:00 and was already done with WS and Boomilever. He kept his composure and performed well, which is really good.

He was expecting a 35' ceiling, but that's the actual roof. Reasonably safe height is 20', which is lower than we've practiced at. He didn't miss a beat, and did some test flights with the backup plane to learn the venue. The slightly thicker prop (less flaring) was hauling the plane into the rafters even at torques below 0.25 in.oz, ergo way too much de-winding. We haven't tested much with thinner rubber so he switched to the primary plane (the prop flares more). He lowered the launch torques from 0.3 to 0.25 going left, and from 0.27 to 0.23 going right. As soon as he was comfortable with his proximity to obstacles, he just put everything away until his official flights.

He had to switch gears right away and do Boomilever. He used his heavier one and got the 5kg bonus, efficiency with the bonus=1227. We're not sure where that will put him today, but this was his first time and he just wanted to see how it all goes. He's reserving the 1439 Boomilever for regionals and will use it if he can't make a better one before then.

As soon as that was done, he got called to do his official flights, and they went perfectly: juuust under the obstacles, 1'38" right and 1'47" left at 20'. These are equivalent to the 1'50"-ish flights we get in our gym at 25' so we're really happy; it means he wound the motor well, set the shim and rudder correctly, etc... Again, I don't know where he will place, but what matters to me is that it all came together as planned, even with some mild challenges.

Now is a good time to repeat a big "Thank You!" for all of the great info we've gotten in this thread.

[xiangyu]

I'm so excited for Luke that I'm posting even though it's still early in the day. I didn't go, mainly to avoid stressing him out with last-minute advice, but I was anxiously awaiting an update. It was a whirlwind pace: he called just after 10:00 and was already done with WS and Boomilever. He kept his composure and performed well, which is really good.

He was expecting a 35' ceiling, but that's the actual roof. Reasonably safe height is 20', which is lower than we've practiced at. He didn't miss a beat, and did some test flights with the backup plane to learn the venue. The slightly thicker prop (less flaring) was hauling the plane into the rafters even at torques below 0.25 in.oz, ergo way too much de-winding. We haven't tested much with thinner rubber so he switched to the primary plane (the prop flares more). He lowered the launch torques from 0.3 to 0.25 going left, and from 0.27 to 0.23 going right. As soon as he was comfortable with his proximity to obstacles, he just put everything away until his official flights.

He had to switch gears right away and do Boomilever. He used his heavier one and got the 5kg bonus, efficiency with the bonus=1227. We're not sure where that will put him today, but this was his first time and he just wanted to see how it all goes. He's reserving the 1439 Boomilever for regionals and will use it if he can't make a better one before then.

As soon as that was done, he got called to do his official flights, and they went perfectly: juuust under the obstacles, 1'38" right and 1'47" left at 20'. These are equivalent to the 1'50"-ish flights we get in our gym at 25' so we're really happy; it means he wound the motor well, set the shim and rudder correctly, etc... Again, I don't know where he will place, but what matters to me is that it all came together as planned, even with some mild challenges.

Now is a good time to repeat a big "Thank You!" for all of the great info we've gotten in this thread.

Mr. Chassin,

Wow that is awesome! Congrats to you and your son! Thank YOU for your guidance and contributions!

I'm testing my plane again tomorrow. It's been kind of frustrating since I haven't made much progress since my last invitational, still at around 1:30. I am now using a bi-plane design that I made and during its first flights last week it got 1:30 so fingers crossed tomorrow I'll finally make some progress.

Xiangyu

[bjt4888]

Eric,

Congrats to Luke. Excellent critical thinking under pressure!

Our next invitational has a 12 ft ceiling.

Brian T

[lechassin]

Xiangyu,

Thanks for the kudos. Luke called from the return bus: he got 1st in class and 1st overall for WS and 1st in class/2nd overall for Boomilever. He did not know by what margins or how much others may have held back, but he seemed happy. He also seemed satisfied with the rest of his team, there was even some talk that they might get to State. We'll have to wait and see, of course.

1'30" is great, especially if your ceiling is 25' or less with HVAC running. It's what we still get on many flights so you're not far off. Any flight we get above 1'50" involves some element of luck so I don't think of those as reproducible (yet). Are you running two blades or three?

[lechassin]

Congrats to Luke. Excellent critical thinking under pressure!

Our next invitational has a 12 ft ceiling.

Brian T

Thank you Sir!

12ft, ouch! We would need a whole new plane/prop/motor to cope with that.