Flight Trimming

leetx
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Re: Flight Trimming

Postby leetx » March 3rd, 2010, 11:15 pm

Thanks jander, carney, WSM for your inputs. I did a little more poking around the internet, especially at the Yahoo Indoor Construction Group.

I noted that there are differences in opinion among the "experts". Some like flying nose up, with thrust in line with motorstick and hence up. Others don't like this and prefer nose level and thrust level during flight.

There were a couple of reasons cited by the proponents of nose up flying. First, when the nose is up during cruise and descent, the propeller slows down, and this contributes to a longer flight. Second, others have noted that if the nose is not up during cruise, the plane will take a small dive and lose altitude when cruise power is used up. The common static set up to achieve nose up flying is to set the wing level with motor or slightly positive and have the stab slightly negative wrt the motor stick.

In two of our planes, even though the wings and stab incidences are both positive relative to the motor stick, they cruise slightly nose up. These two fly nose up and have very smooth transitions from cruise to descent.

In a third plane, the wing and stab incidences are more significantly positive, and the plane cruises with the motor stick level. I have noticed that this plane suffers a 3' level drop (a small dive) at the end of cruise.

However, the proponent of level thrust, level motor stick flying is a current world record holder. (The proponents of the nose-up school are also world record holders.)

What's to make all this? One, use your stop watch and measure your trim by time. Discussing theory and other people's opinions/experiences is useful, but make enough measurements yourself so that you can better understand the theory. Continue to question, experiment, and analyze.

Have fun.

leetx
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Re: Flight Trimming

Postby jcollier » March 4th, 2010, 2:58 am

What makes this event so interesting is that every plane / wing / etc. is an entity of its own. My son's best time last year was with a plane that flew nose up and was fighting for altitude every second. Our high school coach likes planes to fly like that. When I help John Clapp at states, he often comments on planes flying and clearly favors more level flight. Yesterday my son was doing trim flights and the plane looked like it was low on power. He lowered wing incidence 1mm at a time and the height increased and trim times went from less than a min. to 1.25. The other plane was literally just the opposite! :shock: As jander said a few times, the event just begins when the student finishes building the plane. :)

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Re: Flight Trimming

Postby StampingKid » March 5th, 2010, 7:08 am

Regional tomorrow. Flying Freedom Flights with broad blade which has large rear stab and works best on a rearward cg. Pea-sized mass on end of tail stick gets good cg. Placing that on top of rudder should move the cg back a bit but hard to tell as I have only been able to get good reading on cg by balancing plane upside down. I have gym time tonight. Any thoughts on whether placing it that high will adversely effect flight? It would be more prominent there--larger mass as opposed to sandwiched on tailstick and would also be more offset to left.
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Re: Flight Trimming

Postby StampingKid » March 22nd, 2010, 7:04 am

J.Collier write
What makes this event so interesting is that every plane / wing / etc. is an entity of its own.
That makes me think that I still have both my planes from last year. And they are built to this year's rules. I am going to get them out of moth balls and check their static set up and bring them to my next practice. I will not be nearly as nervous about banging them against the rafters. It will be neat to see if I have gotten better as a flyer. I may even see about building a wing to the state bonus, though I doubt it.
I WILL RETURN TO PHILMONT IN JULY!
07 Reg 1st BLG, 3rd WV.
08 Reg 1st Twr, 2nd BLG
State 1st Twr
09 Reg 1st WS, PSL and Crave the Wave, 2nd Robo-X, EB
State 1st EB, 3rd WS
10 Reg 1st EB, PSL, 2nd WS, Disease Det., 3rd Traj.
State 1st EB, PSL, 2nd WS, 3rd Disease Det.

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illusionist
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Re: Flight Trimming

Postby illusionist » March 24th, 2010, 2:00 pm

What is an ideal location for the cg?
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eta150
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Re: Flight Trimming

Postby eta150 » March 24th, 2010, 6:55 pm

Depends on wing size, I think it's been mentioned several time in the Wright stuff board.
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Re: Flight Trimming

Postby StampingKid » March 25th, 2010, 10:06 am

Depends upon the stab size too So ideal is based upon the individual plane. I think this year with the limits on chord size it is more rearward. But as someone noted each plane is an entity unto itself. The Freedom Flight developer noted that it flew preliminarily well up to .75 inch rearward in his design plans. But two experienced coaches/mentors on this forum noted .25-.50 inch and even at the rearpost for this same plane. As Jeff Anderson has noted building the plane is only a small part of this event. Your practice will determine ideal for your plane..
I WILL RETURN TO PHILMONT IN JULY!
07 Reg 1st BLG, 3rd WV.
08 Reg 1st Twr, 2nd BLG
State 1st Twr
09 Reg 1st WS, PSL and Crave the Wave, 2nd Robo-X, EB
State 1st EB, 3rd WS
10 Reg 1st EB, PSL, 2nd WS, Disease Det., 3rd Traj.
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eta150
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Re: Flight Trimming

Postby eta150 » March 25th, 2010, 3:23 pm

Due to repairs (most notably on my destroyed tail), my plane has gained .10~.15g. Would this weight gain result in the ~10 sec. I've lost from my flights? I'm rebuilding the tail from scratch to cut weight regardless, but I was wondering if that small weight gain should have caused this change.
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Re: Flight Trimming

Postby calgoddard » March 25th, 2010, 3:41 pm

Assuming your 2010 Wright Stuff plane was flying around three minutes in a low ceiling height, i.e approximately 22 feet, and 0.10 to .15 grams of weight was then added to the plane, it is reasonable to assume that this extra weight could result in flights about 5 - 10 seconds shorter, all other factors being constant. This is why Jeff Anderson and others are continually recommending that students fly a plane that just meets the 7.0 gram minimum weight.

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eta150
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Re: Flight Trimming

Postby eta150 » March 25th, 2010, 3:44 pm

Yeah, that sounds about right. Thanks!
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Littleboy
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Re: Flight Trimming

Postby Littleboy » March 27th, 2010, 4:56 am

Does anyone know how tall the gym will be for MI state?

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Re: Flight Trimming

Postby jander14indoor » March 27th, 2010, 8:38 pm

Assuming its flown in the usual gym, which I expect, about 24 ft or so at the center peak, 20 ft at the sides. That's to the bottom of the rafters. Not open girder rafters, but solid I-beam rafters, I think. Some lights and ceiling fans, spaced enough not to be too much problem. I seem to remember they replaced the hanging lights with flush ceiling fluorescents improving the site for WS, but that may have been the other gym we use when there are two flying events. Floor space is generous enough to fly multiple official flights, but we seldom do, though we may interlace teams t get all 48 teams in. Two teams flying officials at one time, but only one in the air at a time. At some times of day there is drift, but I'm going to leave that to you to figure out.

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Re: Flight Trimming

Postby StampingKid » March 30th, 2010, 4:04 pm

4 weeks until state. Moving from low humidity winter to spring showers. My bridges I store in turkey roaster bags with silica crystals. Should I worry about my planes? My first concern for them is not breaking them. But their static set up is so précise that I also want to avoid warping the wing or stab especially in an adverse direction. And do I need to be aware of any adjustments for the rubber size if we have rain on the day of the competition? When we fought running vents last year we used bigger rubber. Is 100 percent humidity going to call for a similar adjustment?
I WILL RETURN TO PHILMONT IN JULY!
07 Reg 1st BLG, 3rd WV.
08 Reg 1st Twr, 2nd BLG
State 1st Twr
09 Reg 1st WS, PSL and Crave the Wave, 2nd Robo-X, EB
State 1st EB, 3rd WS
10 Reg 1st EB, PSL, 2nd WS, Disease Det., 3rd Traj.
State 1st EB, PSL, 2nd WS, 3rd Disease Det.

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Draylon Fogg
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Re: Flight Trimming

Postby Draylon Fogg » March 31st, 2010, 3:23 pm

Moisture adds weight, but also flexibility, so it just depends on where your planes are trimmed at, but there might be some call for adjustment when you get there.
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Re: Flight Trimming

Postby bd123 » April 3rd, 2010, 11:55 am

My plane initally climbs really fast (while stalling), at a very high angle untill it gets close to the ceiling about 18ft. It then levels out and then decends. Is this normal? I feel that if the ascent is slower it would be better.

My plane is 7.0grams. Around .102 ish rubber, 45(15) winds, 1.4-1.5g. Fairly large wind chord. An ok number of winds left. The front of the wing is 1/8" higher than the back. Center of gravity is around the middle of the wing.


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