Flight Trimming

[jander14indoor]

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).

[blue cobra]

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

[GitItWright]

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.

[jander14indoor]

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

[blue cobra]

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.

[jander14indoor]

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.

Jeff Anderson
Livonia, MI

[wiitard827]

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?

[jander14indoor]

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.

Jeff Anderson
Livonia, MI

[mg]

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

[blue cobra]

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.