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All Forums >> RC Airplanes >> 3D Flying! >> Sach 4.2 3D Prop at 6,500 ft???
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Sach 4.2 3D Prop at 6,500 ft??? - 12/16/2012 9:10 PM   
USAFA RC Club


 

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Hello All,

On one of our 3D competition planes we are running a Ralph Cunningham Sach 4.2 (69cc). The guys on the team can't come to an agreement as to which prop to purchase for the plane, so we were wondering what you guys had in mind.

Again, reminder that the aim is to 3D with the aircraft and the Air Force Academy is roughly 6,500 feet in altitude. As of now we have a spare 20x12 to get it in the air, but I don't think that's the right prop for the Sach.

Thanks!

Cadet Tyler V Brennan
United States Air Force Academy


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RE: Sach 4.2 3D Prop at 6,500 ft??? - 12/17/2012 1:35 PM   
sensei



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Status: offline 		What kind of airplane?
What scale?
What does the engine weigh?
Finally what is the all up weight of the airplane?

Bob

< Message edited by sensei -- 12/17/2012 4:32 PM >

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RE: Sach 4.2 3D Prop at 6,500 ft??? - 12/17/2012 2:41 PM   
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Status: offline 		he said it's a Sbach .. asumeing he wants to fly 3D


not sure what engine your runing that's 69cc but my guess you'd be aroud 25 x10 xoar or 26 x10 .. need engine type to look up it's prop chart

for a example DA 60 sweet prop is mez 24X10 your cc is some what close to the DA but your motor might have differnt porting and compression so that will change things a littel



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RE: Sach 4.2 3D Prop at 6,500 ft??? - 12/17/2012 4:31 PM   
sensei



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quote:

ORIGINAL: zacharyR

he said it's a Sbach .. asumeing he wants to fly 3D


not sure what engine your runing that's 69cc but my guess you'd be aroud 25 x10 xoar or 26 x10 .. need engine type to look up it's prop chart

for a example DA 60 sweet prop is mez 24X10 your cc is some what close to the DA but your motor might have differnt porting and compression so that will change things a littel



I take it you did not read and understand all of his post... He stated that he intends to fly 3D with whatever aircraft it is, however the Sack's power plant is by today's standard heavy and not as powerful, so I thought with a little of his airplane information we might be able to lead him in an educated direction.

Bob

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RE: Sach 4.2 3D Prop at 6,500 ft??? - 12/17/2012 4:32 PM   
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Status: offline 		Flying a Lanier Extra 87, looking at coming in at around 19-20 pounds ish. And the engine is a Sach... not flying an Sbach lol Think the weight of the engine is approx. 5 pounds.

Really just wondering what you guys thought would be the best prop for the engine at altitude.

Thanks!

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RE: Sach 4.2 3D Prop at 6,500 ft??? - 12/17/2012 4:56 PM   
sensei



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Status: offline 		The manufacture claims a 24x10 is a good prop for that engine. Those old Lanier 1/4 Extra's came out between 22 and 28 lbs. unless you placed the airplane on a radical diet and the Sack's 4.2 with exhaust, ignition, and battery are close to 6 lbs. So your at 6,500 ft and want to perform 3D. I hope you come out as light as you stated or you may be disappointed.

Bob

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RE: Sach 4.2 3D Prop at 6,500 ft??? - 12/17/2012 5:08 PM   
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Status: offline 		I was thinking a 24x10 as well. And this article http://www.rcuniverse.com/magazine/article_display.cfm?article_id=611 has it with a DA-50 at 17 1/4 lbs. They ran Nimh and I will have Lipos. Trying to offset the weight of the Sach as much as possible. The DA comes in at 3 pounds, so I think a fly weight of 20 with the Sach is reasonable.

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RE: Sach 4.2 3D Prop at 6,500 ft??? - 12/17/2012 6:42 PM   
sensei



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Status: offline 		I do wish you the very best in your effort.

Bob

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RE: Sach 4.2 3D Prop at 6,500 ft??? - 12/18/2012 12:52 AM   
airraptor


 

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Status: offline 		I dont think that plane will 3D very well by itself let alone with that engine installed.

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RE: Sach 4.2 3D Prop at 6,500 ft??? - 12/18/2012 2:50 AM   
USAFA RC Club


 

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Status: offline 		Guess we'll see what our guys can do with it

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RE: Sach 4.2 3D Prop at 6,500 ft??? - 12/18/2012 4:04 PM   
wyo69cowboy



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Status: offline 		Hope to see some video of how it goes!

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RE: Sach 4.2 3D Prop at 6,500 ft??? - 12/18/2012 4:32 PM   
USAFA RC Club


 

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Status: offline 		Starting with a Menz 24x10. Will see how it goes and let you all know.

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