Flight Times

[jcollier]

The rules have made the state and national wing a little more interesting this year. Last year, my son's first good plane wanted to rocket out of the gym, so I thought it might be worth the effort for him to try the bonus wing. Comparing best flights, he would have needed about a 50% bonus to make it worthwhile. I would think a well constructed and trimmed, 7 gram Freedom Flights or Leading Edge plane would be pretty tough to beat with a bonus wing. If I was going to try, I would try a similar reduction in stab cord, but keep the max span.

[jander14indoor]

That is what I was thinking, but I technically don't need the same amount of lift (because of the bonus), and I think (correct me if I'm wrong) that the relationship between wing area and lift isn't linear, and I should be able to get enough lift if I use different level of curve. I also don't know how much more time I can get out of a 2:50 + plane.

Actually the relation between lift and area is linear. BUT, its not that simple. The relation between SPEED and lift isn't linear, its squared. So to lift the same 8.5 gm with a wing half the size, you need to go sqrt(2) faster or 1.44. But you aren't finished there. You have to consider drag. It also follows speed as a square, so it will take twice the energy (1.44 squared) to fly at 1.44 speed increase. SO, as a first order approximation, you'll fly half the time on half the wing.

Of course the trouble is, who's to say that you have to stop at a 15 cm wing? Why not 16 cm, or 17? Then the bonus is less than half the competing wing. Of course low aspect ratio wings tend to have higher drag than high aspect ration. Enough? Ahh, that's why its an experiment.

If a competitor knows the answer, don't expect a straight answer. Your fellow SO students are nice and all, but...

And as a mentor, well, that's an exercise left for the student...

Jeff Anderson
Livonia, MI

[mg]

Hi!
I won MN state tornament yesterday. It was a rough day. My plane flies three minutes, and my practice flights were 2:35 all day. When it came time for the event I used a .093 rubber band thinking it was a .088. I over wound the rubberband, and crashed my first flight. I then relized the rubber band mistake and wound the .088 less only getting a 2:08. To my suprise I won by 3 seconds. See you at nationals!!

[jcollier]

Congratulations! Now you get to fly in that great big space.

[jcollier]

Middle Eastern PA Regionals tomorrow. I will be supervisor for WS. Hope we get a bunch of planes that can fly well this year.

[hammy]

Right now me and my partner are getting about 1:32 at the most making some new ajustments though.

[sydneenicole902]

most times in our regional competions are like 1:20. This year WS at Auburn was in like a regular room. If was so bad we placed 9th with only 12 seconds because most of the planes crashed. In our school gym we can get like 2 minutes without going into the rafters.

[jcollier]

Well, the words for the day at our regionals was power stall! A few teams that are going to States had impressive trim flights, then had fairly major problems with their official flights. The winning time was 2.06.6. If Wright Stuff was not rotating out of the lineup, I think I would see if I could invest in Freedom Flights kits. Saw a whole bunch of them today.

[illusionist]

I am getting around 1:30 with my plane. it has a 38.5 cm wingspan and 11 cm chord, 19 cm tailspan, 6 cm tailchord, 3/32 inch rubber motor, and a 20 cm ikra prop. Any suggestions on improving my times? the flight path is very stable and it flies in smooth circles. I am putting in 800 turns. Please help!

[jander14indoor]

I am getting around 1:30 with my plane. it has a 38.5 cm wingspan and 11 cm chord, 19 cm tailspan, 6 cm tailchord, 3/32 inch rubber motor, and a 20 cm ikra prop. Any suggestions on improving my times? the flight path is very stable and it flies in smooth circles. I am putting in 800 turns. Please help!

You didn't say what your plane weighs? If you aren't close to 7.0 gms, that's the first thing, lose weight.

If weights OK, try more turns, so long as the motors don't break, you may be near the limit, but I don't think so. If you are banging the ceiling, wind more and then back off till you stop hitting the ceiling.

If no turns left on landing, thinner rubber or more turns on this rubber.

Try raising the leading edge of the wing or the trailing edge of the tail till you start stalling on descent, then back off a little. Then rematch rubber and prop.

Where's your cg, if not at the rear wing post, or behind, move it back, readjust the wing and stab to stop stalling, and then rematch rubber and prop.

Take and review data every step of the way. Try to repeat each setting twice to make sure some other anomaly didn't mess up the result. Go with what the data says. Be careful about changing too many things at once unless you have someone who can guide you in Design of Experiments (DOE). Note, DOE is NOT experimental method, its a mathematically efficient and correct way of varying multiple factors at once and sorting out the true effects. The basic math to execute DOEs are within a middle school student's capability, theory and correct application will be more of a stretch.

Jeff Anderson
Livonia, MI