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Prop diameter

  • William Holloway
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1 week 2 days ago #16935 by William Holloway
William Holloway created the topic: Prop diameter
Will changing my 3 bladed Warp Drive prop on a pusher from 66" to 68" improve my cruise speed.

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  • Bill Hertzel
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1 week 2 days ago #16937 by Bill Hertzel
Bill Hertzel replied the topic: Prop diameter
What Engine? What Plane? What is your WOT Engine Speed? What is your cruise Speed?

Your Speed at cruise is all about Power.
If your current WOT at Cruise is anything other than 5500rpm, you need to adjust the prop that you already have First.

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1 week 2 days ago - 1 week 2 days ago #16939 by Roger Lee
Roger Lee replied the topic: Prop diameter
Hi William,
2" isn't going to make much of a noticeable difference and I wouldn't go to a 70".
I did find that a sweet spot for a balanced all around prop rpm was 5600-5650 for the ground adjustable guys.. This gave a good balance between climb, cruise, fuel economy and engine temps. More rpm gave you a better climb prop, but it then suffered a tad in cruise and fuel. Anything under 5500 max rpm WOT in level flight is a waste of climb, cruise, fuel and increased engine temps.

I did a big prop research project about 7 years ago. I tested 14 different props of different diameters, flex (stiffer vs more flex) and different shapes.
My research was different from any prop Mfg in the US and maybe the world. I had 4 aircraft of all the same make and model and were even Mfg within a couple months of each other. Actually I had 8 of the same, but only used the 4. We take off side by side in pairs and I was the only one setting them up for control of the max rpm. Setting up testing and doing all flight maneuvers side by side shows much more than just guess work if you only flew one at a time and under different conditions for each. It compares each prop to the exact same flight conditions at the same time that I set up for take off, cruise and time of day conditions.
Bottom line is most prop Mfg's will tell you they have the best thing since sliced bread, but they all really perform close to the same. Will a 68" do better than a 64", for the most part yes.

I will say this about the Warp. In cruise it flew the same speed as others at the same rpm, but suffered a lot in climb compared to others. This is due to the flat straight blade design I'm sure. I experienced this big time on my own CTSW once compared to others. Warp is a good dirt field type prop and holds up well to nicks, but isn't so great if you hit something really solid and transmit that shock to the engine. A light composite might not hold up as well to rocks, but is a lot nicer to the engine if you strike something solid.

I used to be a Warp fan, but after all the testing I've moved on.

p.s.
I sent my results of this research to the prop companies. Funny no one wanted to publish the results. I guess they just didn't want to look like all the other prop Mfg's. :)

Roger Lee
LSRM-A & Rotax Instructor & Rotax IRC
Tucson, AZ Ryan Airfield (KRYN)
520-574-1080 Home (TRY HOME FIRST)
520-349-7056 Cell
Last Edit: 1 week 2 days ago by Roger Lee.
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  • Genival Pacheco
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1 week 2 days ago #16946 by Genival Pacheco
Genival Pacheco replied the topic: Prop diameter
Hi Roger

It seems that the results of your survey are very interesting. You should show to us here.

Let me ask you another question regarding the number of the propeller blades.

What are the pros and cons of a 2 or 3 blades propeller both equaly configured to max. eficiency?

Regards

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1 week 2 days ago #16949 by Roger Lee
Roger Lee replied the topic: Prop diameter
2 vs 3 blade didn't make any difference flying, but the static rpm on the ground during setup was quite different. The 2 blades have a wider more pronounced frequency through the aircraft hull where the 3 blade had a narrower frequency and felt smoother. Props I tested were 64" to 70" 2 and 3 blade.

Roger Lee
LSRM-A & Rotax Instructor & Rotax IRC
Tucson, AZ Ryan Airfield (KRYN)
520-574-1080 Home (TRY HOME FIRST)
520-349-7056 Cell

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1 week 2 days ago #16953 by Garth Handlon
Garth Handlon replied the topic: Prop diameter
Question: When you are talking 5500 WOT speed are you talking engine 912, 914 or 582. I fly a 582 and have it set WOT of 6500. Would my take off and cruise benefit from a reset to 5500. Thanks

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  • Bill Hertzel
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1 week 1 day ago #16957 by Bill Hertzel
Bill Hertzel replied the topic: Prop diameter
The 5500-5600 rpm recommendation is for the Rotax 900 series of engines.
5500 would mean a short life for your 2-stroke.

Your 582 makes max power at 6500rpm.
The 912 series makes max power at 5800rpm which is also the 5 minute Red Line speed.
5600 rpm is the continuous max rpm.

That is why we asked the original poster what engine he has.

William, Where did you go?

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1 week 1 day ago #16958 by Garth Handlon
Garth Handlon replied the topic: Prop diameter
That's what I thought but needed to ask. Thanks

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  • Genival Pacheco
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1 week 1 day ago - 1 week 3 hours ago #16960 by Genival Pacheco
Genival Pacheco replied the topic: Prop diameter
Tanks Roger,

As I understand regarding performance either one of the PROPELLERS is fine.
What is not clear to me is regarding the gear box and plane structure.
because of the vibration as you mentioned it seems that the 3 blade is better.
Last Edit: 1 week 3 hours ago by Genival Pacheco.

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1 week 1 day ago #16964 by Roger Lee
Roger Lee replied the topic: Prop diameter
Sorry I thought you were talking about the 912 series. propping the 582 properly is the right thing to do also. There are no good qualities that come from over pitching.
I think many could help themselves just by getting a dynamic balance on their props/aircraft.
When I flew Gyros and helicopters we always balanced the blades.

Roger Lee
LSRM-A & Rotax Instructor & Rotax IRC
Tucson, AZ Ryan Airfield (KRYN)
520-574-1080 Home (TRY HOME FIRST)
520-349-7056 Cell

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  • William Holloway
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1 week 2 hours ago #16986 by William Holloway
William Holloway replied the topic: Prop diameter
I have been away for a while, in my original post I was speaking about a 912 engine.

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6 days 9 hours ago #16988 by David Nana
David Nana replied the topic: Prop diameter
please any one explain the life of prop? it depends on no of.years ot running hours?

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4 days 13 hours ago #17000 by Roger Lee
Roger Lee replied the topic: Prop diameter
Sometimes both and on condition at annuals checking for delamination, nicks and cracks.
Some props do have a flight time inspection based on flight hours. For instance a Neuform prop is 1500 flight hours and then an authorized service center must inspect it.

Roger Lee
LSRM-A & Rotax Instructor & Rotax IRC
Tucson, AZ Ryan Airfield (KRYN)
520-574-1080 Home (TRY HOME FIRST)
520-349-7056 Cell
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4 days 1 hour ago #17003 by Ken Ryan
Ken Ryan replied the topic: Prop diameter
Kiev says 8 years for the blades, 15 years for the hub.

http://kievprop.com/products_eng.html
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4 days 58 minutes ago #17004 by David Nana
David Nana replied the topic: Prop diameter
Expire life prop caused RPM DROP,
ITS PRACTICALLY DONE.

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