Flight Trimming

jander14indoor
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Flight Trimming

Postby jander14indoor » August 6th, 2009, 3:21 pm

Since we have a dedicated board for WS now, I thought it might help to organize by kicking off topics around the typical WS questions. Content of string to be driven by subject line (I hope).

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Re: Flight Trimming

Postby blue cobra » August 26th, 2009, 4:20 pm

What are some things that can be done to make the most out of very limited gym time?
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Re: Flight Trimming

Postby GitItWright » August 27th, 2009, 5:48 pm

Go in with a plan. Even with limited gym times, following a plan will reduce the damage to the airplane.

1) For basic trim scenarios, have a visual list of which aerodynamic changes will cause the airplane to react in what way. IE.. if the trailing edge of the left wing is lower than the leading edge and... the trailing edge of the right wing is higher than the leading edge, the airplane has more lift on the left wing and the airplane will have roll tendencies to the right... There are many more so you need get put that in order, first.

2) For pushing the performance envelope to the extreme (and, incidently, may mean that you begin "flogging the airframe") try using the half motors method that allows a full flight profile without flying the general max flight time. If applied correctly a 3 minute airplane (one that has actually done 3 minutes!) wil fly 1-1/2 minutes yet all the nuances will still be demonstrated throughout the flight and you may trim accordingly within a tight schedule.

3) Improve you're personal performance. Invite the administration (principle, vice-principle) to see how you are organized for testing. Demonstrate how you proceed through this laboratory setting following scientific process. If you are sincere without being demanding, they may just go to bat for you and get more time available.

Good Luck.
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Re: Flight Trimming

Postby jander14indoor » August 29th, 2009, 4:23 am

blue cobra wrote:What are some things that can be done to make the most out of very limited gym time?

Agree wholeheartedly with Get It Wright on need for plan. But if you are new, what's that plan look like?

Start with a plane that is set up carefully to a known, correct static condition.
For a fairly conventional plane (and if you are starting you should be flying a fairly conventional design) most are close to flying correctly with the following set up.
Balance point should be at rear wing post for say a 10 cm chord wing to last years rules. 1-2 cm if front of rear post for a 12-15 cm wing. 2-4 cm behind wing for a 5 cm bonus wing.
Wing level with motor stick (I use top of motor stick for my consistent reference on angle of attack) fore and aft. Offset about 1-2 cm to left. Right wing level fore and aft with motor stick, left wing washed in (leading edge high) about 1/8th inch.
Prop should be pointing SLIGHTLY (2 degrees or so) left and down.
Tail should be flat with respect to itself. Tilted slightly with respect to wing so left tip is higher than right. Tail boom should be offset to left about 1-2 cm at very end from line of motor stick. Leading edge of tail should be 2-4 mm lower than trailing edge with respect to wing level (or again, top of motor stick).
CHECK THESE THINGS BEFORE EVERY FLIGHT! The exact settings may change based on your data, but there's a reason pilots use checklists!

Start your first flights with just enough winds to turn the prop smartly, say a couple of hundred turns. You are essentially going to glide test the plane. Launch at shoulder height and observe plane. You are looking for a steady, slowly descending flight with a left turn. Here's where that list of trim scenarios mentioned is useful. If the plane stalls, what do you do, etc.

Once you get that nice steady turn and slow descent, start adding turns. Watch for weird changes in behavior, typically means you've broken something, you went to extreme on some setting at an earlier step, or your plane is too floppy. Correct small errors in behavior with small adjustments before moving on. Change one thing a a time! Again, a list of trim scenarios and how to correct is useful here. If no big problems, by the time you get to 1200 turns or so (depending on rubber width and prop pitch) should should be climbing nicely to the ceiling, circling a few times, and descending slowly.

With that you should be able to get to 1.5 to 2 minute flights fairly quickly.

Jeff Anderson
Livonia, MI

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Re: Flight Trimming

Postby blue cobra » September 13th, 2009, 3:12 pm

Thanks. Gym time (or lack thereof) can be so frustrating! We submit the paper work to get our few hours a year, and we get what we ask for. However, 50% of the time I arrive at our pre-scheduled time to find it occupied by sports teams that should be outside anyhow.
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Re: Flight Trimming

Postby jander14indoor » September 14th, 2009, 3:41 am

Make sure your coaches are with you and kick their a....s out. You contracted for the time, its yours. they just need to have it pointed out to them. You go to the school and have as much right as they do to the space.

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Re: Flight Trimming

Postby wiitard827 » September 15th, 2009, 3:48 pm

I am looking to buy the Leading edge 2010 plane for use in the devision B wright stuff event. does anyone know where i could buy this plane?

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Re: Flight Trimming

Postby jander14indoor » September 18th, 2009, 5:37 am

The Leading Edge design hasn't been available as a kit for a couple of years. Old plans are around the internet as a starting point, but you'll need to modify them to this years rules.

The Finny-09 design (available on the Yahoo group Indoor_Construction) has many of the features that made the Leading Edge superior and is to last years rules so it will need less modification to meet this years rules.

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Re: Flight Trimming

Postby mg » February 1st, 2010, 5:14 pm

I have a nicely trimmed plane with a thin ikara prop that climbs to the ceiling in a small 21ft gym. At high torque and winds I usually hit the ceiling 2-3 times. I tried thinner rubber but can't get long flight times. Would decreasing the pitch of the prop help stay off the ceiling? If I change the pitch does the plane need to be retrimmed? Last year I used a broad ikara prop, and this seemed to help keep it fron the ceiling. If I changed to a broad prop would I have to readjust the plane (move wings, center of gravity or angle of attack)?
Thanks for the help,
MG

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Re: Flight Trimming

Postby blue cobra » February 1st, 2010, 5:40 pm

I would say to keep it off the ceiling lower your wing AoA very slightly. Some of the more experienced people may be able to help more.
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Re: Flight Trimming

Postby eta150 » February 2nd, 2010, 8:18 am

I believe the Leading Edge is available this year as designed by Cezar Banks. It's available from the A2Z corp store and Turner Toys (in limited quantities).
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Re: Flight Trimming

Postby leetx » February 9th, 2010, 9:04 am

from last year, jander14indoor wrote:

Yet another (for small changes) is to warp or bend the tail boom using heat (typically your breath).

For large changes you may need to crack and reglue the tail boom. Nice feature, once you get it right, it stays. Bad feature, can add a lot of weight cracking and regluing if you take a lot of changes to get to the right place.


Can you elaborate a little on the "crack and glue"? First, what do you mean by "crack"? I would also like to know the kind of glue you use and how you apply the glue to secure the position after the crack.

I have bent the tail boom using my breath for what I think are fairly large changes, such as resulting in a 5mm + change at the end of the tail boom. I have noticed that over time, the tail boom tends to bend itself back toward the old position, not back to the old position but enough to significantly affect flight.

Thank you.

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Re: Flight Trimming

Postby jander14indoor » February 9th, 2010, 2:28 pm

Yeah, that's the problem with bending with breath, tends not to be permanent.

'crack' is a nice way to say BREAK it, but not too much.

Two approaches, depending on size and hardness of stick.
First, cut about halfway through where you want to crack the stick, then gently flex it at that point, just enough to crack the fibers, but not enough to cause a seperation. Note, you can get complicated bend directions this way by angling your cut if needed. Then apply thin superglue to the crack while holding the stick at the desired position and hit it with accelerator. WIth practice, you can do this on your own, but extra hands can help early on. One cracks and holds the stick in the desired orientation, while the partner applies glue and setter.
To keep from using too much glue, I use a precision micro superglue applicator, two pins stuck through a stick that come together at a point. This lets you pick up small amounts of superglue from a puddle of a drop or two and apply it to a joint, Done carefully, little weight gain. The kink or bend you put in the stick this way is permanent.
Specific example, I want to bend the back of the tail boom around to the left. Cut around halfway through on the right side, perpendicular to the stick. Crack gently till angle is reached. Apply glue to lock.
If you want to bend it up, cut on the bottom.
If you want it left AND up, an angled cut on the right side (or bottom) will do both at once, but you need to figure it out thinking of the cut as a hinge.

Second isn't much different, just skips the cut. Use your fingernails to localize pressure for crack and again, don't overdo it. A little less controlled, but ends stronger as more fibers are continuous across the joint than the half cut.

Hope that's clear, let me know if not.

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Re: Flight Trimming

Postby leetx » February 9th, 2010, 3:59 pm

jander14indoor wrote:
'crack' is a nice way to say BREAK it, but not too much.

Two approaches, depending on size and hardness of stick. [snipped]


Wow, that is really interesting and not what I expected. I'm glad I asked. I expected you to say to glue inside the cut and to bend to the side of the cut. I think this is because I use acetone-based glue and not CA. I am not experienced with CA, not yet at least. I've read your article on using gglue and will try it out CA. Expect additional questions under the "building technique" topic. :-) Thank you.

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Accelerator for Cyanoacrylate (CA)

Postby calgoddard » February 9th, 2010, 11:30 pm

Sometimes Super Glue (Trademark), otherwise known as cyanoacrylate (CA), will not set up. It may have absorbed too much water over time. The temperature may be too low.

Builders are tempted to use commercial accelerators to get the CA to cure.

May I suggest you look at the Material Data Saftey sheet (MSDS) for the CA accelerator you are considering.

You may decide to use something else. One of my mentors taught me to use household baking soda instead. Just a little sprinkle will usually cause the CA to harden rapdily. Use a small paint brush with stiff bristles to wisk away excess baking soda after the glue joint has set up. Baking soda is totally harmless - heck it is meant for human consunption in cakes, etc.

Of course CA should only be used for quick repairs in Wright Stuff because of the significant weight that can be added. Also, a CA joint is difficult to undo, unless you use a commercial de-bonder, and again, read the MSDS and decide if you really want to use that product.

Remember that CA will bond very poorly to a joint previously bonded with CA. Also CA, particularly the very thin formulations, will only work for a relativley perfect joint, i.e. one that has little or no gap that must be spanned by the adhesive. The tighter the fit between the two wood pieces, the less glue you can use and the stronger the joint will be.

Cezar Banks taught me the bend-but-don't break technique that can be used to advantage by breathing on the tail boom and coaxing it the way you want it to go. Do it over several inches and you will have far less risk of breaking your tail boom. If the tail boom should snap, don't fret, just glue 1/32" sheet gussets about one-half inch long on either side of the tail boom, spanning the fracture. You will gain no more than about .05 grams if you do it properly.


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