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WorldModelsP51/YS91AC/apc11x12 - 8/20/2002 3:34:33 AM   
DKjens



Posts: 2085
Joined: 2/10/2002
From: Pasadena, CA, USA
Status: offline 		I had one of these setups before, but with an apc14x10. It didn't sound fast, but was when flying with other planes. I sold it, but now I bought another. This one, with the apc11x12 is faster I think, I just worry about the engine. My YS91AC turns this prop at 11.3K on the ground, so it may get to 12k in the air. I am wondering for how long this engine will stay together, and I should probably get an apc12x12.
DKjens
       Post #: 1

WorldModelsP51/YS91AC/apc11x12 - 8/20/2002 6:18:12 AM   
Cyclic Hardover



Posts: 7190
Joined: 5/7/2002
From: New Mexico, USA
Status: offline 		Here is my WM .40 size P-51. I am running a ST G90 and a Pitts underneath. I started with a 12/8 apc. Went to a 12/10. The magic prop turned out to be a 12/9 apc. I get around 100mph with this and it is smoooooooth. A .91 four stroke would also be very awesome too. The 12/12 or maybe 13/10 would be a good area to start. The one area I was using as a judge on my prop selection was my climb out after a high speed pass. The 12/8 was not problem. So I thought I want more prop and went to a 12/10. Speed was good but climb out was very poor. 12/9 brought it all together.

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Retired Army Aviator - Excuse Me! You sold me a hair with a cake around it!

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WorldModelsP51/YS91AC/apc11x12 - 8/22/2002 6:30:48 AM   
RyanG


 

Posts: 28
Joined: 3/21/2002
From: Los Angeles
Status: offline 		About 10 guys at my field fly 40 size warbirds with ys .91 They are all spinning 13x8 and getting about 12,000 on the ground with ys 20/20 fuel. They clock their planes at about 140 and go up for a split S until you can't see them anymore.

(in reply to DKjens)
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140 mph - 8/23/2002 8:52:54 AM   
bugsiegel



Posts: 568
Joined: 12/30/2001
From: brooklyn, NY, USA
Status: offline 		can a ys .91 turn 18500 out of a dive

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speed - 8/23/2002 6:36:12 PM   
jlong34016


 

Posts: 365
Joined: 4/14/2002
From: columbus, OR,
Status: offline 		unless you have clocked or radar gunned a plane these guesses are really meaningless. Everyone thought my DD was really going fast too. Radar gun 115. A trainer was doing 85 at the same time. The smaller the plane the faster it looks.

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Re: speed - 8/23/2002 7:44:23 PM   
maverick



Posts: 1575
Joined: 11/29/2001
From: Alameda, CA, USA
Status: offline 		[QUOTE]Originally posted by jlong34016
unless you have clocked or radar gunned a plane these guesses are really meaningless.[/QUOTE]

Where do you get the radar gun from? How much are they?

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Maverick: "Too close for missiles, I'm switching to guns!"

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radar gun - 8/23/2002 11:56:58 PM   
bugsiegel



Posts: 568
Joined: 12/30/2001
From: brooklyn, NY, USA
Status: offline 		stay away from the 99.00 ebay job. to get any kind of reading off that gun you have to be almost directly in line and real close to the passing plane. way too dangerous. we had one at the club. we wound up putting it back on ebay for a 15.00 loss.

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radar gun - 8/24/2002 4:30:29 AM   
jlong34016


 

Posts: 365
Joined: 4/14/2002
From: columbus, OR,
Status: offline 		I got mine off the internet. There are many to chose from. I went with an expensive one that reads to 300 mph and has good enough sensitivity so a normal pass down center of runway is easily detected. Mine is from Astro Products. Cost 850.00. But there are several that read to 200 mph for under 200.

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Astro products. - 8/24/2002 4:32:31 AM   
jlong34016


 

Posts: 365
Joined: 4/14/2002
From: columbus, OR,
Status: offline 		[url]www.astroproducts.net[/url]

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WorldModelsP51/YS91AC/apc11x12 - 8/24/2002 5:56:35 AM   
maverick



Posts: 1575
Joined: 11/29/2001
From: Alameda, CA, USA
Status: offline 		Thanks for the tips on the speed radars guys! It is not something I have ever looked at before so had no idea where to start.

_____________________________

Maverick: "Too close for missiles, I'm switching to guns!"

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       Post #: 10

Update - 8/25/2002 2:16:20 AM   
DKjens



Posts: 2085
Joined: 2/10/2002
From: Pasadena, CA, USA
Status: offline 		Bought an apc12x12 yesterday, and flew it today. My YS91AC turned the apc12x12 at 9700 on the ground. It didn't seem as fast in the air, but I feel better (engine health wise) with this prop. With the 12x12 it may unload to 10700 - 11k in the air, with the 11x12 it may unload to 12300 - 12500 in the air, or what do you think. When does valve float start taking place in a YS91AC, and how big is the chance of valves hitting piston top, or other internal no nos?
DKjens

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WorldModelsP51/YS91AC/apc11x12 - 10/4/2002 1:09:59 AM   
AeroD79



Posts: 105
Joined: 5/9/2002
From: Placentia, CA, USA
Status: offline 		WHere did you get your WM ARF mustang from?
Also do you think Saito 100 would do better than YS91?

Btw im the person who I was flying the BLUE mustang at Whittier Narrows...I decided not to move to hawaii ...so im planning to get back my planes together..

(in reply to DKjens)
       Post #: 12

Re: Update - 10/4/2002 1:38:39 AM   
BernieG


 

Posts: 283
Joined: 8/26/2002
From: Broken Arrow, OK, USA
Status: offline 		[QUOTE]Originally posted by DKjens
Bought an apc12x12 yesterday, and flew it today. My YS91AC turned the apc12x12 at 9700 on the ground. It didn't seem as fast in the air, but I feel better (engine health wise) with this prop. With the 12x12 it may unload to 10700 - 11k in the air, with the 11x12 it may unload to 12300 - 12500 in the air, or what do you think. When does valve float start taking place in a YS91AC, and how big is the chance of valves hitting piston top, or other internal no nos?
DKjens [/QUOTE]

You can't evaluate precisely how much an engine "unload" in flight (which is not as much true for a 4 stroke than for a 2 stroke anyway), just as it's very difficult to evaluate how efficient/inefficient a given propeller is. So, for the sake of discussion, let's say both parameters nullify each other. What is interesting, is the comparison. You say your engine reach 11.7 thousands rPm on the ground with a 11*12, and 9.7 thousandd RPM with the 12*12. Let's see: 12 inch per rotation 11300 times a minute => 140400 inches per minute, or 8 424 000 inches per hour, which is 132.95 mph.

Now, the same 12 inches per 9700 => 110.22 mph. Knowing that the wider prop is more efficient than the smaller one, I would bet that a radar reading would read about 100, maybe 105 mph with either prop ! (Airplane drag does not change with the prop...) BTW, this estimation assume an extremely aerodynamically clean airplane....

So I would certainly go for the prop which is the more efficient and is not going to wear your engine too fast.

Bernard

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Re: Re: Update - 10/4/2002 1:41:50 AM   
BernieG


 

Posts: 283
Joined: 8/26/2002
From: Broken Arrow, OK, USA
Status: offline 		[QUOTE]Originally posted by BernieG
BTW, this estimation assume an extremely aerodynamically clean airplane....[/QUOTE]

What I mean is, just the fact to not have doors to close properly the openings when the gear is up take easily 5 to 8 miles from the top speed ! Those planes ARE NOT aerodynamically clean, all the control horns are exposed to the airflow, etc....

Bernard

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       Post #: 14

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