Wright Stuff B

[jander14indoor]

Others have already answered your specific questions. And has been suggested, review the other Wright Stuff threads on this site, and the SO wiki.

BUT, Wright Stuff has to be one of the MOST documented and supported SO events on the web.

I'd like to strongly point you to the National webpage for this event: http://soinc.org/wright_stuff_b That page points you to just a few of the sources for help on the event, spend some time studying them. Those links include answers to many of your questions, detailed step-by-step instructions for building a competitive WS plane (to prior year rules, but the techniques that lead to success haven't changed), sources, etc.

Jeff Anderson
Livonia, MI

[bob3443]

From my rear hook to my front hook the distance is 9 inches. so i'm using 18in. of rubber. i have tan super sport 1/16in. i was wondering how many winds do you think i can get without breaking the rubber. i was browsing through websites and i read somewhere than 3/32in. rubber can get about 127 turns per inch, so i'm assuming i can get about 1800 turns?
i'm not sure how much it weighs i don't have a scale at home so i'm bringing it to school tomorrow.

also on the rules it says you can use o-rings on the motor, does it have to be rubber?? please help, thanks!!!!!!

[jander14indoor]

From my rear hook to my front hook the distance is 9 inches. so i'm using 18in. of rubber. i have tan super sport 1/16in. i was wondering how many winds do you think i can get without breaking the rubber. i was browsing through websites and i read somewhere than 3/32in. rubber can get about 127 turns per inch, so i'm assuming i can get about 1800 turns?
i'm not sure how much it weighs i don't have a scale at home so i'm bringing it to school tomorrow.

also on the rules it says you can use o-rings on the motor, does it have to be rubber?? please help, thanks!!!!!!

From memory, 1.5 gm of 3/32 rubber is much longer than 18 inches. Use 1.5 gm of rubber, not 18 inches. There's NO reason your rubber loop should match the hook to hook distance, in general it doesn't. Max wt of rubber is critical. Rubber mass is fuel. Use a full tank. Rubber thickness is horsepower, match it to your plane and site, adjust length accordingly to use full 1.5 gm

Al long as you lube the motor that many turns should be OK. Probably more. Make up some short test motors and test them to find out for sure.

Go back and reread the rules on the o-rings, it says what they can be made of. (hint, I don't use rubber o-rings)

Jeff Anderson
Livonia, MI

[carneyf1d]

i used to use rubber o rings...but they didnt do anything. o rings are supposed to provide easy transport from winder to plane, and since the rubber rings twisted, they were as hard as the rubber band to get off.
Number of winds also greatly depends on the batch of rubber you have. i used around 1/8 by .030 a while back, not sure why it was so thin, but you usually can expect around 120(15) winds. on the other hand, if you get some awesome rubber like 3/02, you can expect 165-175 (15) winds. also take into account that i had 2 grams rubber, not 1.5

[noob]

I got 5th place bolth times!

[carneyf1d]

what were your times?

[planesarefun52]

Does anyone know if there is a signifigant "penalty" in flight time if you use the state bonus 6.5 cm instead of a larger 12-13cm wing chord?

[bob3443]

No there's no penalty, you won't loose points. but if you do it during states you'll get extra points.

[smartkid222]

i think he's asking if using a smaller wing cord will hurt times (the plane will not stay in the air as long) as compared to a longer wing chord. hence the quotes on "penalty", I think.
I assume it would make flight times less, but that's why the bonus is there, for you to decide which is more beneficiary to you, the bonus, or the extra flight time you'll get with a longer wing chord. I don't know how significant it will be though.

[carneyf1d]

stall speed for an aircraft is sqrt([2*weight]/(rho*S*Cl)) where rho is air density, S is wing area, and Cl is lift coefficient. If you fly at stall speed, your endurance will be nearly maximized. To do this you can increase your wing area, S, to lower your stall speed. However there is also a term AR with is the aspect ratio, equal to b^2/S. Where b is the chord length, and S is again the wing area. When you increase the chord area, the aspect ratio grows exponentially, and since drag is related directly to AR, the bigger the AR the greater the drag.
So basically all that math means there is a trade off. Increase the chord and it helps in one way hurts the other, but decrease it and it helps in another way and hurts the other. Play around with different chord lengths and see which gives you the best time.