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Old Sep 19, 2003, 10:32 PM
The devils playground
Tasmania's Avatar
Island of Tasmania
Joined Apr 2003
799 Posts
just to keep on topic heres another low pass from this morning coming out of the trees, if it ever hits any of these 80 feet high eucalypt trees its going to be history for my moth I recon.

Doug I PM'd you . duno if you have it ?

and Tom, the money's in the post honest...

Taz
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Old Sep 19, 2003, 10:34 PM
an earth bound misfit, I
Basketcase's Avatar
St. Pete, Florida
Joined Sep 2001
9,429 Posts
Taz, I think adding slats or making the wing more undercambered would have essentially the same effect. The indoor rubber powered planes are ultralight and fly with hugely undercambered wings at very very slow speeds.

A key point is the huge power plant you mentioned. If you add more power to the TM, say a 300, it will climb like the proverbial homesick angel.


Dooms Day, how many hours are on the motor? The symptoms you are describing sound like it might be the beginning of the end. If you have more than 10 hours or so you may want to try a new motor.

Usually when they go bad it is so gradual at first that you think it might be your imagination, or maybe the batteries, or anything but the motor. Usually it'll keep getting worse and worse until it won't stay in the air anymore. Once in a while it'll keep flying until it just quits altogether, but that's pretty rare.

Some last much longer and some last quite a bit less. 8.4 volts will wear it out faster than 7.2, and 6 NiMH cells really don't get it. Most people count the NiMH's as more like 1.1 volts under load so that's more like 7.7 volts instead of 8.4. Most folks feel the extra power of 7 cells is worth the slightly reduced motor life.


Taz, here's a pic for you, our local group flying field is outlined. My house is 2-1/2 miles south east of this park.

BC
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Old Sep 19, 2003, 10:45 PM
Non Practicing A&P Tech
dulcelife's Avatar
Tampa, Florida, United States
Joined Aug 2003
2,330 Posts
Taz:

Try the higher pitch propellers and see if you get a speed increase with the dually.

I certainly noticed a difference with the cut down 9080. There are a lot of variables with the chopped prop. For example the chopped prop has more area to it which should in theory provide more thrust in addition to the higher top speed a higher pitch is suppose to provide assuming available power.

But, another factor is that increased area is at the cost of prop weight which in my chop prop case is 2gr heavier than a stock 9070. And if that were not enough there's the increased drag at the prop tips caused by my bruta chopping job.

All in all, I think a well designed/tapered 9080 prop would be a very interesting prop to play with indeed. Whatever the case I like the choppy and the whole exercise of searching for a speed increase at whatever trade-off, with the stock IPS.

Of course all this will go out the window as soon as I receive my two GWS 100C motors at least for a good while. The challenge will be devising a motors mount to accommodate both the IPS and 100C motors so I can play with both.

Here is a pic of the two props and the approximate difference in area:



Luis~
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Old Sep 19, 2003, 10:46 PM
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Island of Tasmania
Joined Apr 2003
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Great pic BC and nice lake at the park too, have you landed the moth on the island yet ? you wouldnt want to be in those houses on the inlet though, if the sea decided to rise a few feet they'd be underwater wouldnt they ?

BC when you say "undercambered" wings, is that the actual curve of the wing, like the moth? what if you just put slats on without increasing the engine power, would it let it fly slower and climb steeper? I dont really want it to go any faster but I'd like it to fly slower without stalling ?
Taz
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Old Sep 19, 2003, 10:54 PM
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Tasmania's Avatar
Island of Tasmania
Joined Apr 2003
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nice pic Luis, showing the 2 props, wow there is a big difference, I weighed mine again and its up to 9.3oz from 8.7 now with the dualies, i recon its the extra weight that stops it pulling 6 loops. I dunno.. theres a lot to be said for keeping it light with the stock ips and 9x7 i recon.. I will try the 1080 again and also the 1180 I have, but i have noticed that my flying time with the dual is less now, with the single i easy got 45 mins , with the dual the most ive got is 30 mins, usually 20 mins, but that was battling wind a bit today, so its is really hard to compare these props and stuff unless you get the ideal stable conditions, which really i havent since getting the dual.

Taz
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Old Sep 19, 2003, 10:54 PM
The devils playground
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Island of Tasmania
Joined Apr 2003
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Oh! and Luis thanks for posting the pic of that printed chart that was great too
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Old Sep 19, 2003, 11:00 PM
Burnin' holes in the sky!
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Gilbert, AZ
Joined May 2003
2,848 Posts
Man, hot thread! Can anyone say Part 4?

Taz- Slats on a model, especially one with already heavily undercambered wings is usually not a good idea. It's pretty funny, there was a guy at my glow field that built a plane with all the high lift devices, in an attempt to make it STOL. Flaps, slats, the dimensions, etc. The added weight of all that stuff made it take off in maybe a foot shorter of an area than a normal plane, and had terrible deadstick characteristics, and generally didn't fly all that good. The model really has to be quite a bit bigger for them to work, without making it too heavy. Probably at least ~80" wingspan. BTW These were servo actuated. Making that stuff permanent would not be a good idea, since it would add so much drag, you would have to cruise around at way higher throttle than normal. Feel free to experiment, though I doubt the first GWS Tiger Moth out of R&D flew good.

Dan
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Old Sep 19, 2003, 11:09 PM
The devils playground
Tasmania's Avatar
Island of Tasmania
Joined Apr 2003
799 Posts
Skypyro, thanks for the info Dan, yes that makes sense, just the slightest aditional weight seems to make a difference to the moth, I guess GWS must have done a lot of home work to get it just right like this. I might experiment with another plane, I have a spare aerobird fuse wing and guts, I thought about turning it into a bi plane . I might just put some spoilers on the front now. trouble is I'm having so much fun with the moth i havent flown my other planes for a while.

Taz
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Old Sep 19, 2003, 11:14 PM
Non Practicing A&P Tech
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Tampa, Florida, United States
Joined Aug 2003
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I've tossed around the idea of a Firestick XL after I'm done playing with the stock Pico Stick.

Basket:

Got my directions to your neck of the woods. Now I hope it doesn't rain or something else.

Night all

Luis~
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Old Sep 19, 2003, 11:18 PM
an earth bound misfit, I
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St. Pete, Florida
Joined Sep 2001
9,429 Posts
Taz, the undercambered in wings refers to the way the underside curves up into the wing. Normal wings, even those on the STOL are flat bottomed, or for aerobatic planes symetrical with the same airfoil shape on both the top and bottom.

We really need somebody who can explain it better than I can, but if you extended the wing area would lower the wing loading and increase the drag so would result in slower speed. Everything is a compromisen, to increase any one attribute you have to give up on something else.

The barrier island in the background is Treasure Island, Florida and only a few feet above sea level. You're right, if we have a major hurricane here the whole thing will turn into a nice clean sandbar again. The highest elvation in the entire state is 345 feet and that is way up near southern Alabama, the highest point in the peninnsula is 184 feet. Makes it tough to do any slope soaring.

BC
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Old Sep 19, 2003, 11:26 PM
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Tasmania's Avatar
Island of Tasmania
Joined Apr 2003
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BC , thanks for the info, i understand now, the undercamber thing, yes Ive studied some of the earobatic planes at the airshows here and they have the same shape top and bottom. I think I'll get a book on aerodynamics and do some studying, great hobby this

ok on being a few feet above sea level too, yes it would make it difficult to slope soar., I guess you could thermal though. here we are lucky living on the most mountainous island in the world, microclimates everywhere. good for slope soaring if you tie yourself to a tree just in case

Taz
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Old Sep 19, 2003, 11:34 PM
Burnin' holes in the sky!
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Gilbert, AZ
Joined May 2003
2,848 Posts
Yes, what BC is saying is totally correct, except one thing. There are far more airfoils than you make it sound. There are, in fact, several hundred thousand known airfoils, with some having the most ludicrous shapes you would think of, but fly great. I wish someone could describe it better too, I would just make it seem like insane rambling

Dan
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Old Sep 20, 2003, 01:04 AM
AllAloneInSpaceAndTime
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Canada, ON, Guelph
Joined Apr 2003
2,389 Posts
Gotta start part 4!!! Holy Moses!

Link: http://www.rcgroups.com/forums/showt...hreadid=152366


Corey

And thanks Genovia. But I'm sure the thread wouldn't be nearly as long (or as interesting not to mention full of great info.) if I had written the whole 1100+ posts by myself. Thanks all. See you in part 4.
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Old Sep 20, 2003, 01:37 AM
Leave me alone!
Martin Hunter's Avatar
Kamloops, BC, Canada
Joined Feb 2002
15,106 Posts
Keep the great info coming, guys. Thanks for starting part 4 in the above link (http://www.rcgroups.com/forums/showt...hreadid=152366). I'm closing this one

Martin
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