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APC Prop Constants...

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Old 09-09-2012, 04:32 AM
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Default APC Prop Constants...

I'm trying to get some realistic numbers from Pé's prop power spreadsheet but I cannot find all of the prop constants figures. Most of the sites I've found thus far only list APC's Electric props. I am using props from 9x4 up to 13x8 and I am sure that the prop constant changes from prop to prop, so... Does anyone have a list or know where to find a list of APC's Sport series prop constants? (C2 mold)

I searched the forum here and didnt find much that helped, and google didnt help much either. I'm kind-of at a loss.
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Old 09-10-2012, 03:43 AM
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Default RE: APC Prop Constants...

Some electric sites list the 1000 rpm watt value. Whilst APC are very constant in their production techniques, their prop power demand across sizes tends to vary considerably.
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Old 09-10-2012, 12:05 PM
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Default RE: APC Prop Constants...


ORIGINAL: pe reivers

Some electric sites list the 1000 rpm watt value. Whilst APC are very constant in their production techniques, their prop power demand across sizes tends to vary considerably.
I've noticed that some props have a prop constant of .90 and others as high as 1.4 depending on what site you're on. Do you have any idea if a more complete list is available for the fuel powered props?
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Old 09-10-2012, 01:23 PM
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Default RE: APC Prop Constants...

If I had that list, I would have converted it. Take what you can get, and search for what you need.
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Old 09-10-2012, 02:02 PM
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Default RE: APC Prop Constants...


ORIGINAL: pe reivers

If I had that list, I would have converted it. Take what you can get, and search for what you need.
Thats what I've been doing. Pardon my ignorance, but how exactly does one determine the prop constant, anyway?
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Old 09-10-2012, 05:00 PM
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Default RE: APC Prop Constants...

Look up NASA dryden (sp) research. there was a guy in here that tested many props and posted the results.

The prop calcs dont do much except for playing around with numbers on the computer. lol i have found better use of time trying props in the air. plus you get some time in.
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Old 09-10-2012, 05:50 PM
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Default RE: APC Prop Constants...

ORIGINAL: airraptor

Look up NASA dryden (sp) research. there was a guy in here that tested many props and posted the results.

The prop calcs dont do much except for playing around with numbers on the computer. lol i have found better use of time trying props in the air. plus you get some time in.
I'm going to start calling you Professor from now on. You always seem to know better.

The whole point of this is to be able to compare a couple of my engines to determine where they make the best power. Two engines can turn a given prop at the same RPM, but one could be making half the power it should be and needs to be run on a different prop. It may not be accurate to .00000001%, but I dont need it to be. Just a ball park is fine.

The Dryden Research site doesnt have much pertinent information that relates to the topic of this thread.
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Old 09-10-2012, 08:56 PM
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Default RE: APC Prop Constants...

Geez i will look it up for you.
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Old 09-10-2012, 08:58 PM
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Default RE: APC Prop Constants...

Ok here is the first result of my search on the net.

http://www.ae.illinois.edu/m-selig/props/propDB.html

http://soar.wichita.edu/dspace/bitst...773/t05031.pdf

http://dc.library.okstate.edu/cdm/si...id/2757/rec/14

https://netfiles.uiuc.edu/kotwani2/w...apers/FMFP.pdf

http://etd.auburn.edu/etd/bitstream/...pdf?sequence=1

this should be enough reading for you for now. It will explain how the constants were derived. Use this data to set up the calc with different props. then use a known prop in the calc on a engine that will run that prop at that rpm. then base other props on the same engine to get a general idea what the contant should be for that prop. this will work on any prop close to the same rpm as the "known" prop.
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Old 09-11-2012, 02:13 AM
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Default RE: APC Prop Constants...

ORIGINAL: airraptor

Ok here is the first result of my search on the net.

http://www.ae.illinois.edu/m-selig/props/propDB.html

http://soar.wichita.edu/dspace/bitst...773/t05031.pdf

http://dc.library.okstate.edu/cdm/si...id/2757/rec/14

https://netfiles.uiuc.edu/kotwani2/w...apers/FMFP.pdf

http://etd.auburn.edu/etd/bitstream/...pdf?sequence=1

this should be enough reading for you for now. It will explain how the constants were derived. Use this data to set up the calc with different props. then use a known prop in the calc on a engine that will run that prop at that rpm. then base other props on the same engine to get a general idea what the contant should be for that prop. this will work on any prop close to the same rpm as the ''known'' prop.
I came across most of those pages last night. I understand how the data is collected. Now to find the right data (prop constant) that works in Pé's spreadsheet.

Thanks for your time.
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Old 09-11-2012, 03:16 AM
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Default RE: APC Prop Constants...

You can find APC & APCW constants on this [link=http://personal.osi.hu/fuzesisz/strc_eng/index.htm]STATIC THRUST CALCULATOR[/link]

Click on the propeller type tab & a drop down menu will appear.
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Old 09-11-2012, 03:36 AM
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Default RE: APC Prop Constants...


ORIGINAL: SrTelemaster150

You can find APC & APCW constants on this [link=http://personal.osi.hu/fuzesisz/strc_eng/index.htm]STATIC THRUST CALCULATOR[/link]

Click on the propeller type tab & a drop down menu will appear.
Thank you. I'll check that out when I get off work.
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Old 09-11-2012, 04:23 AM
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Default RE: APC Prop Constants...

If you know your engine's HP/RPM profile you can also get some insight into which propeller to chose W/this [link=http://personal.osi.hu/fuzesisz/opc_eng/index.html]OTIMAL PROPELLER CALCULATOR[/link]

Both of these calculators are only good for comparison as DA & other conditions can vary results. Hiowever, I have found the results to very consistant W/my Saito single & twin cylinder 4-strokes.
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Old 09-11-2012, 04:43 AM
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Default RE: APC Prop Constants...

That is a nice and easy to use calculator. However, the quite limited prop constants of the Hungarian web calculator do not match the real world feed back that I use. A lot of work still has to be done here.
The http://www.ae.illinois.edu/m-selig/props/propDB.html database has excellent numbers, which oo require a lot of work to convert the mean static Cp numbers of different props into the pitch entry of my calculator, which is pretty much rule of thumb for ease of use.
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Old 09-11-2012, 09:29 AM
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Default RE: APC Prop Constants...


ORIGINAL: pe reivers

That is a nice and easy to use calculator. However, the quite limited prop constants of the Hungarian web calculator do not match the real world feed back that I use. A lot of work still has to be done here.
The http://www.ae.illinois.edu/m-selig/props/propDB.html database has excellent numbers, which oo require a lot of work to convert the mean static Cp numbers of different props into the pitch entry of my calculator, which is pretty much rule of thumb for ease of use.

None of those work for me as the smallest prop I use is a 15X5, the largest is 22X8.
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Old 09-11-2012, 12:06 PM
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Default RE: APC Prop Constants...

My calculator works regardless of prop size OR fluid medium, even water! Just adjust the proper parameters.
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Old 09-11-2012, 01:17 PM
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Default RE: APC Prop Constants...

Pe have you tested your calc by running those props in your calc with an electric motor at certain rpm leves to see if the HP is the same readings? All the brushless motors you can measure how effiecient it is running and the amout of power applied to the prop. this will tell you how close it is.
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Old 09-11-2012, 01:20 PM
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No, I did not, but two universities did that in wind tunnels. My calculator proved up to 2% pessimistic in it's predictions, which is well within technical accuracy.
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Old 09-11-2012, 03:19 PM
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Default RE: APC Prop Constants...

ORIGINAL: pe reivers

No, I did not, but two universities did that in wind tunnels. My calculator proved up to 2% pessimistic in it's predictions, which is well within technical accuracy.
Thus my reasoning for using your prop power calculator spreadsheet versus any other application. Its been well documented in its popularity, so it must be good.

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