Design

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Re: Design

Post by Toms_42 » March 16th, 2015, 11:43 am

nxtscholar wrote:Have you tried using a helium filled balloon to retrieve it?
That would have been smarter... we used a huge pole. Unfortunately, the prop was REALLY stuck in there, so in the process of getting it down the tailboom broke off of the fuselage and somehow managed to get wedged in the light. We recovered the wing and fuselage intact though.
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Re: Design

Post by Less_Incidence » March 17th, 2015, 4:41 pm

It's funny how WS planes always manage to wedge themselves into places as firmly as they possibly can.
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Re: Design

Post by Chris_L » April 29th, 2015, 2:00 pm

For people using small rubber cross sections, how many winds do you end your flights with? Just wondering because I end all of my flights with maybe 15 to 20 turns with a thicker rubber bands.
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Re: Design

Post by bernard » April 29th, 2015, 2:07 pm

Chris_L wrote:For people using small rubber cross sections, how many winds do you end your flights with? Just wondering because I end all of my flights with maybe 15 to 20 turns with a thicker rubber bands.
By 15 to 20 turns, is that turns on a geared winder or turns in the rubber? I fly on 0.094" and I think for some flights I was pretty much out of winds (in the motor) when it landed. I'll probably be flying Friday so I'll try thinner rubber and let you know how it goes.
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Re: Design

Post by Chris_L » April 29th, 2015, 2:10 pm

By 15 to 20 turns, is that turns on a geared winder or turns in the rubber? I fly on 0.094" and I think for some flights I was pretty much out of winds (in the motor) when it landed.
15 to 20 meaning turns in the rubber...and yea..that's pretty much the same with me...I was just wondering how much do the people with the thinner rubber use?
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Re: Design

Post by Less_Incidence » April 29th, 2015, 2:31 pm

To the question about thin cross sections and turns left - I use .081 rubber and usually land with about a full row of knots in the motor - that's 150ish turns. I wind between 1800 and 2050 depending on how broken-in the motor is.

However, my plane's best flight was on a piece of .077 rubber (Basically thick pennyplane rubber) that I wound to something like 2400 turns and landed with about 400 left. I've found that using a thin piece of rubber and landing with lots of turns left has given me my best times - I switched from .094 to .087 and instantly improved by 30 seconds, then from .087 to .081 and instantly improved another 25. Different people have had different results though.
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Re: Design

Post by bernard » April 29th, 2015, 2:36 pm

With thinner rubber, my plane doesn't climb as high. Do you have any suggestions for improving that? Should I play again with prop pitch and incidence when I switch to thinner rubber?
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Re: Design

Post by Chris_L » April 29th, 2015, 3:01 pm

To the question about thin cross sections and turns left - I use .081 rubber and usually land with about a full row of knots in the motor - that's 150ish turns. I wind between 1800 and 2050 depending on how broken-in the motor is.

However, my plane's best flight was on a piece of .077 rubber (Basically thick pennyplane rubber) that I wound to something like 2400 turns and landed with about 400 left. I've found that using a thin piece of rubber and landing with lots of turns left has given me my best times - I switched from .094 to .087 and instantly improved by 30 seconds, then from .087 to .081 and instantly improved another 25. Different people have had different results though.
What are your flight times? and at what height?
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Re: Design

Post by Less_Incidence » April 29th, 2015, 3:08 pm

Bernard:

I've found that prop pitch is the biggest factor in climb, much more so than wing incidence. I fly a prop with a very, very low effective pitch - it's a flaring Ikara with the small bit of material on the back of the blades cut off, and also sanded on a flat surface rather than on a round soda can so that the blades were flattened slightly in the sanding process. I don't have a pitch gauge so I couldn't give you a number (and Ikara props don't follow helical pitch anyways), but generally a lower pitch prop will provide a better climb with thinner rubber. The trade off is that a low-pitch prop will run at a higher RPM than an equivalent high-pitch prop, but I believe that the large blade area of the Ikara combined with the flaring property and the thin, low-torque rubber makes up for this.

On another note, I think I mentioned this earlier in this thread, but I made a modification to the Freedom Flight plane that involved making the tail boom drop downward so that the rudder sat about 2 1/4" below the motor stick. After I did that, I stopped having problems with the plane stalling on descent and it gained that nice efficient nose-up attitude throughout the whole flight that probably helped conserve turns on the thin rubber as well. Probably more a function of the slight change in tail incidence than of the stab height relative to the wing, but whatever I did definitely worked.

Chris_L:

The best flight my plane has done with .081 Tan SS was a 3:07 in a 22' gym, and that was a no-touch (barely). I made a strip of February 1999 Tan II rubber in .077 and the plane did 3:26 in the same gym. When I go to USIC in June and fly in the 35' auditorium there, I think I can get near four minutes. I really wish I could fly in the 60' site at nationals... Unfortunately my school's team didn't qualify. We never do... *sigh*
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Re: Design

Post by DoctaDave » April 29th, 2015, 10:10 pm

Do you know why dropping the tail prevents stalls on descents? just curious how what affects it.

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