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Old Jun 04, 2004, 11:14 AM
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New Boston, Texas, United States
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Best prop for speed on GWS 350?

I have a scratchbuilt Earl Stahl P-40 converted at 36" ws and weighing 16 onces. I have tried several props but dont seem to be able to get the speed I need to do some maneuvers ie a good loop. I have a C gear box on it and am running 9.6 1000mah nihm. Can any of you guys tell me what the optimum prop would be on this combo?

Jim
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Old Jun 04, 2004, 02:35 PM
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First of all great job! Thats a beautiful plane.

I think a GWS 9x7SF will be as good as it gets.

When you can get a Himax 2025-4200 Brushless, a 3S LiPo pack around 1500Mah, a Castle Phoenix 25 and an APC 10x7SF on your gearbox. It will scream, Have unlimited vertical and fly for 20 minutes!
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Old Jun 04, 2004, 03:09 PM
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Another possible is APC 8x8E. It will be faster but not climb as well, nor loop as well...maybe.
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Old Jun 04, 2004, 04:55 PM
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Thanks for the replys guys. I haven't even tried the 9070 prop on the 350 yet. I had tried the 1080, 1047, and the 1060. Just checked the GWS site and dah. Those props are listed as high thrust but for high speed I should use the 9070. I will try it tonight and see what happens. I tried the 1047 prop last night. It is listed as the one with the most thrust and it was probably the worst as far as performance goes. Just goes to show that static thrust is not a good indicator of what the performance of an airplane will be. I have learned that the P-40 needs speed to perform. Speed also equals climb on this plane. Thrust alone wont cut it. The prop of the above that gave me the best performance was the 1060 but not to the point I was satisfied.

Jim
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Old Jun 04, 2004, 05:58 PM
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I flew a stock Formosa for a few weeks with the setup you have(thats that it comes with). The 9x7 SF props is down on thrust but up on speed a little over the 10x6. The 9x7 prop will make a sound that sounds like flutter at high speed...its ok...but it freaked me out the first few time it did it. It caused by the blades flexing/occilating and loosing pitch.

Regaedless you will have ot fly to conserve energy. To steep a climb and you will have to turn ot levle out to avoid a stall. The brushless setup elminated that though!
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Old Jun 04, 2004, 06:16 PM
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Thaks Adrian.

The Himax is not in the budget right now but I am going to try that 9070 this evening to see what it will do. I actually had it mounted last night and took it off to put on the 1047. Big mistake. It was flying so slow that I brought it in after only a minute or two.

Jim
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Old Jun 04, 2004, 06:59 PM
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If your budget can stretch to 3s LIPO and a geared 400 try 3.5:1 or thereabouts and APC 8x8 prop. The heavier motor will help balance the lighter cells, and it ought to have rocket ship performance.
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Old Jun 05, 2004, 10:27 PM
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Thanks for all the help guys. Lipos are probably next in line. Just seem to enjoy bulding too much to spend the money on equipment.

Flew with the 9070 last night. It was the best flight I have had with this plane. Had to dial in a little down elevator to keep the nose down as she had a tendency now to want to climb into a stall with the added speed of the 9070. Best of all I got several large graceful loops. This was a first for this airplane. Would not loop from level but with a shallow dive to pick up speed, she flew all the way through it without any stalling at the top. I was so excited.

Adrian, I did also experience the prop flutter you were talking about. I put her into a strafing run and man did that thing make a noise. I am sure that this thing would be outstanding on a brushless and lipos but I will be content with it the way it is for now.

Jim
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Old Jun 05, 2004, 10:44 PM
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I've found that the APC Thin Electric props give the best combination of speed and thrust. Either the 9x6 or 10x7 ought to give you the flight performance you're looking for in a warbird. Take a close look at the construction and profile of the Thin Electric props, and you'll see that they're quite different from the typical slow flyer props.
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Old Jun 06, 2004, 07:54 AM
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Jima, lovely P40! I built a Stahl Hurricane a while back for FF rubber, now I wish I'd use basswood stringers so I could convert it to RC - one day.

Today I discovered something quite startling - GWS EPS350's! Yesterday I maidened a home made foamie P47, 32" span 20oz (!) AUW with 7.2V sp400 1.85:1 on 3S1P ET1200 and an APC-E 8x6 prop. Sort of flew, but not like something drawing 8.5A should. So I wanted to put my Hacker B2012L in it (had it lying around unemployed) and decided I needed about 5.5:1 to drive the 8x6. Bought an EPS350 5.33:1 and as I didn't have a 2.3mm reamer handy for the pinion, I decided to try the original motor. Awsome! Draws about 7.5A, is 40grams lighter than before, has heaps more thrust than before and flies the plane superbly, plenty of speed, great aerobatic performance. I used to swear by my 7.2V SP400 direct drive on an APC 5.7x3 with 3S lipos, but this outperforms it, draws much less current, delivers more thrust (handlaunching is much easier) and the big prop sounds cool. I'm wrapped!

Stu (very happy after my first fly in months!)
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Old Jun 06, 2004, 02:22 PM
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Thanks guys.

I have an APC 9x6SF prop laying around. Think I may try it if weather holds this evening. Dont think I can use a shorter prop as the spinner is so large on the nose of this baby there would hardly be any prop sticking out.

I would be interested to see how long the 350 holds up to 3s lipos.

Jim
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Old Jun 06, 2004, 07:53 PM
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So would I. Safer option than a grotty 7.2v 400 is a 6v 400 at about 7A, that ROCKS. At 8.5A its obscene.

AND it will last too.
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Old Jun 06, 2004, 10:26 PM
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Flew it this evening with the APC 9x6 SF prop. Better even than the GWS 9070. Climb and top speed was better. No prop flutter. I had to dial in a couple of clicks of down elevator to keep it from climbing into a stall. Even found myself cutting back on the trottle a couple of times. First time I was able to do an Immelmann. If the 350 could handle a 3S lipo it would probably be about as good as it gets without going brushless. Changing to a DD 400 would require too much surgery to mount it now. After my Strutter is finished, I will modify the spinner to fit the APC prop.

Jim
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Old Jun 07, 2004, 04:13 AM
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..yes, but you should be able to slot on a geared one with GSW 400 box.

But if it flies like it outta, who wants to mess with such a gorgeous creation?
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Old Jun 07, 2004, 04:56 AM
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Kalamaki, Greece
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My experiences with a 350 C gearbox on an e-starter with khan 1050 NiMh @ 8.4V:
Doesn't fly properly with anything else than a gws 1080 (around 7-8 amps at static tests). The strange thing is that on gws site, it does not recommend the 1080, instead it suggess 9070 which as I found out (almost the hard way) struggles to get the plane up in the air. The 1080 makes it climb almost vertical.
After a while I found out that most of the other flyers in the field I go to, also fly the 350 C with 1080 ignoring gws's recommendations.
I guess that you need to experiment to find the best combo.
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