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Hi-Performance and Sailplanes RC hotliners, electric pylon racers, F5B, F5D, sailplanes and gliders

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Old 01-05-2013, 05:15 PM   #1
cyclops2
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Default Light wind Wing Loading ?

I need to know if 8 ounces per square foot is considered a good weight for a scale U2 to be flown up to height with a fixed blade pusher prop and then glided around.

The motor / battery can run for a 1/2 hr at WOT.
Thrust is 11 oz. & 40 mph prop speed.
RTF weight is 21 oz.
W A is 2.5 S F
W S is 66"

Thanks
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Old 01-05-2013, 07:01 PM   #2
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That is a cubic wing loading of around 5.1 which is very light for a trainer or on the heavy side for a pure glider. In short, it should fly just fine with your power set up.

It's never too late to have a happy childhood.
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Old 01-05-2013, 07:39 PM   #3
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Smile Late childhood

What does cubic wing loading affect. Compared to ounces per square foot ?
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Old 01-05-2013, 09:13 PM   #4
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Cubic wing loading takes into account the size of a plane and is a number that gives a guide to the way the plane will 'feel' in flight.

Conventional wing loading is ok but of limited use unless you take into account the size of the plane. For instance a 8oz/sq ft loaded ultra micro would 'feel' like a flying brick to fly, but the same wing loading on a giant scale would fly like a feather. Cubic loading is an attempt to come up with a guide that works for any scale.
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Old 01-05-2013, 09:30 PM   #5
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Default Thank you.

I am unable to use cubic loading..............I am a terrible pilot.

So I never can rate a plane other than ........I did not crash. Perfect flight.

It also explains why I always build very light when in doubt.

The student pilot in my AT-6 has his arms crossed in front of his face.

Thank you.
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Old 01-05-2013, 10:20 PM   #6
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Cy, I doubt your a terrible pilot....flying a U2 EDF....

Just in my short time of rc'ing, IMHO I think it would be a fair floater maybe a little bit fast on landing. I seen your posts on rcg.com...Are you thinking about a long motor shaft or a power pod?


cr
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Old 01-05-2013, 10:47 PM   #7
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High CR

I have some Hyperion 12 mm diameter 5980 KV & 7 : 1 gearboxes with APC E 7 x 6 props & a 800 mahr 3 cell. It is on a 3 mm stick. So I would mount the stick to a very thin drilled out plywood plate in the tail duct. It balances on the COG with using up to a 2200 mahr pack.

I thought gliders were super simple. Turns out they require as much thought as a powered plane.

The 2200 would be for the winder days. Would have to discharge it each day though.

Rich
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Old 01-05-2013, 11:15 PM   #8
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Ummmm....e-Gliders are simple as you make em!!!

cr
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Old 01-06-2013, 01:11 AM   #9
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Found this....might help you confirm your figures...

cr


http://www.flyrc.com/index.php/wing-load-calculator/
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Old 01-06-2013, 04:47 AM   #10
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Originally Posted by cyclops2 View Post
High CR

I have some Hyperion 12 mm diameter 5980 KV & 7 : 1 gearboxes with APC E 7 x 6 props & a 800 mahr 3 cell. It is on a 3 mm stick. So I would mount the stick to a very thin drilled out plywood plate in the tail duct. It balances on the COG with using up to a 2200 mahr pack.

I thought gliders were super simple. Turns out they require as much thought as a powered plane.

The 2200 would be for the winder days. Would have to discharge it each day though.

Rich
Hi Rich You might like this motor a little better being direct drive, they are inexpensive and very powerful, and might save you some weight, with a 3 cell and 7x6 prop, they will give you over 20oz of thrust, they can be pushed a lot, i run them at over 20 amps and they love it, this motor has very thick windings in them, and you cant beat the price $6.32 your 5980KV motor being geared down 7 to 1 is equall to a 850kv direct drive motor and that wont give you very much thrust or speed, hope that helps, Chellie

http://www.hobbyking.com/hobbyking/s...idProduct=5430

here is my friend Kosk flying his plane with this 1800kv motor and a 7x6 apc prop on 3 cells.


I may be getting Older, But I Refuse to grow Up I am Having to much Fun to Grow Up LOL
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Old 01-06-2013, 09:42 AM   #11
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Originally Posted by cyclops2 View Post
I thought gliders were super simple. Turns out they require as much thought as a powered plane.
Err.. this IS a powered plane is it not? You want it to be a glider then what's the prop and motor doing in it
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Old 01-06-2013, 02:00 PM   #12
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I originally was going to build this 2nd U2 as a non-powered glider. Then I find that there are no glider people in the area where the 2 of us will be flying.
So

Power to climb high enough several times. 2 old 75ers doing this the first time.
I designed updated drives in industry. So I quickly learned to have a machine run on paper first & at least 2 alternate ways to complete the project.

Thank you all for building some confidence into the plane.

The motor G B & 3 mm stick combo weighs .8 oz. The whole mount & installed will not exceed 1.1 oz. Adding weight that far back gets to be dicy balancing with a 400 to 800 mahr battery in the nose. Tried it.


Rich


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Old 02-05-2013, 01:24 AM   #13
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cyclops2
Was there a reason why you chose to have it as a tail mounted pusher rather than a nose mounted tractor?
Spreading the masses to the fuselage extremes can have an impact on the aerodynamic stability damping and the loss of prop wash does alter the control effectiveness.

My extreme duration plane (Span 48" weight 14.5oz RTF with a 5000mAh 2s) is a pusher but wing mounted to keep the masses more concentrated.
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