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| De Muth prop http://t18.net/thorpforum/viewtopic.php?f=35&t=7692 |
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| Author: | James Grahn [ Wed Apr 01, 2015 1:27 am ] |
| Post subject: | Re: De Muth prop |
I agree you are in the ball park. I get 2200 at 2500msl. I'd have to calculate DA. But it's usually 22 to 2250rpm. I have the same engine and prop. Cubes |
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| Author: | fytrplt [ Wed Apr 01, 2015 7:06 am ] |
| Post subject: | Re: De Muth prop |
Les, Before getting too excited, make sure the tach is calibrated. Mechanical tachs are notorious for lying. With these highly twisted props, static RPM will be lower than we are used to. The true test will come as you reach full throttle red line (2700) at 8500' standard day. Your rebuilt engine will also need to break in before it develops full HP. |
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| Author: | Rich Brazell [ Wed Apr 01, 2015 6:54 pm ] |
| Post subject: | Re: De Muth prop |
DM 68 x 79 with 0-360 A2A . 2400 rpm is all I get . Static and in flight (maybe 2450 rpm on a good day ?) .  I run it at 2400 RPM all day . Averages out to 7.5-8.0 gph . Came from Aero Sport Power and put out 2700 rpm during test run before shipping . My AD prop appears to have a metal leading edge . Ran a magnet across it and BOOM !  RB 
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| Author: | jrevens [ Thu Apr 02, 2015 12:50 am ] |
| Post subject: | Re: De Muth prop |
I have a 68x75 AD prop also. O-320-D2A, 160 hp. Will turn up to approximately 2800 rpm full-throttle at 7500' msl. Electronic tach. Fuel burn at that altitude & 2550 rpm gives me 180 mph TAS, with average fuel burn between 6.5 & 7 gph. Could probably use another inch of pitch. |
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| Author: | ljkrume [ Thu Apr 02, 2015 8:02 am ] |
| Post subject: | Re: De Muth prop |
Thanks guys, good info. I'll see about another way to measure rpm. So with 2000 static would you try a takeoff? Les. |
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| Author: | mattst18 [ Thu Apr 02, 2015 10:09 am ] |
| Post subject: | Re: De Muth prop |
How long is your runway? If you have plenty of length (4000+ for first flight) then yes. If you are not airborn and climbing like a home sick angel by 2000' I will be supprised. I don't have an AD prop and 150hp but my static RPM is only 2000-2100. Just my $.02 and I am not near as experianced as the others on this list so it is probably only worth half that. 
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| Author: | thorpdrvr [ Thu Apr 02, 2015 1:19 pm ] |
| Post subject: | Re: De Muth prop |
As mentioned earlier, verify your rpm with another method. An electronic prop tach works well. My mechanical tach shows about 50 - 75 rpm slower than actual rpm. At your somewhat high field elevation, and maybe higher density altitude if temp is above standard, you will probably have to lean some to reach max power. Probably goes without saying, but best to tie the tail down when doing full power run-ups and fiddling with other stuff. At 2000 rpm, you should get up just fine and then you can check it in-flight to determine if prop is over pitched or engine is not producing full power. Since other guys are using the same prop on 320's with a good match, I think your in good shape. Bernie Fried N18XS |
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| Author: | ljkrume [ Thu Apr 02, 2015 1:59 pm ] |
| Post subject: | Re: De Muth prop |
Great! Thanks again guys. I feel a lot better about trying it out. Yes I did tie it down and leaned it. I heard it may be possible to nose over during a run up; don't know if there's truth to that (?). Matt, told you earlier I'd be there to visit someday when I'm in the air. My brother is a stones throw from the airport. Les Krumel Albuquerque |
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| Author: | mattst18 [ Thu Apr 02, 2015 2:10 pm ] |
| Post subject: | Re: De Muth prop |
Sounds great Les, if the weather cooperates, and I can get my wife to agree to the stop, we may stop in an visit you on the way to Sedona. It would be either Saturday the 11th or Sunday the 12th. Are you going to be around? Maybe flying off your 40 hours... ? |
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| Author: | mattst18 [ Thu Apr 02, 2015 2:18 pm ] |
| Post subject: | Re: De Muth prop |
Oh, what is your airport identifier? |
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| Author: | ljkrume [ Thu Apr 02, 2015 2:50 pm ] |
| Post subject: | Re: De Muth prop |
Always glad to have visitors. Maybe you and your wife would like want to overnight with us in our mountain 'chateau'. I'm at 0E0 (Moriarty - not be confused with OEO), and you can bring it inside to hangar 5. My wife and I will be driving to Sedona on the 17th. Les. |
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| Author: | Rich Brazell [ Thu Apr 02, 2015 2:58 pm ] |
| Post subject: | Re: De Muth prop |
Just my 4 bits , but I would like to know what the engine is really going to produce for T/O before that first test flight . It just may be something that was over looked (besides a faulty tach) . Like is the throttle really fully open ? RB
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| Author: | mattst18 [ Thu Apr 02, 2015 4:23 pm ] |
| Post subject: | Re: De Muth prop |
Les, I sent you a PM. |
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| Author: | James Grahn [ Thu Apr 02, 2015 9:08 pm ] |
| Post subject: | Re: De Muth prop |
Les, You have plenty of runway at 0E0. When test flying, do a good run up for proper lean, then go for it. If you are not airborne by the 2 board, chop the throttle and stop on the runway. If you can land on a 2K runway, you can certainly stop on that much remaining. Cubez |
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