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E-Props ...who has first hand experience with these


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Gday, Finally the results of testing the EProp in comparison to Bolly and Kool (Luga), using manifold pressure to set engine power exactly equal for each. Once again surprising results that

First tests with the variable pitch propeller     

All CSU (I gather thats what your commenting on Bruce) are expensive. I personally dont think they are worth the cost for the performance for our type of aircraft.   Posted above is the std

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I meant to post this the other day...prop comparison..left is the Eprop then a Bolly then a Warpdrive

 

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Bolly and Warpdrive propellers are clearly much 'chunkier' than Eprops.

 

However, the additional length of the Eprops could be a bit of an issue with off-field aircraft like the Savannah.

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No those are the short props they are 68 inch from memory The Eprop is the recommended size it is the DUR-3-175-C4-T which is just under 69 inches . The hub diameter is where the difference is in the overal diameter. The bolly I had on the girlfriend was the 72inch but in actual it was a 70 inch

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I am not sure if Danny has one in his aircraft. Dont really need one unless you have a CS prop or turbo. Interesting is the setup...initial blade setting is 25.1 deg and on the ground the prop should be pitched to produce 5500 rpm on the ground...certainly different to most other props. We will know by the aircraft performance..so it will be a objective view but the Sav is such a draggy aircraft but super consistant in speeds and take off and climb numbers..will see if there is a change

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Props are a bit like dresses - length, cut, etc changes with the fashion - always being (re) invented.

 

I am perplexed - Rotax 912/914 have relativly (to LyCon & Jab) slow revving props. Without any training / verifiable knowledge, it would seem to me that broader/paddle like props would likely be the best in this application BUT here we have a long thin skinny thing doing the job.

 

Perhaps this is why 3 blades are recommended and set to quite a course pitch.

 

On another allied point - do broader blades make for quitter operation ?

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One of the big plusses about the Eprop is apparently everyone says its a lot quieter than any other prop..also less vibrations produced as well.

 

The thin blade at the tip givees you slip on takeoff so you can develop all the horsepower of the engine...this is what I am told...I am not across this indepth theory..the main part of the blade has quite a undercamber and a good constant helix in it...All I can say is it must work as they are certainly stirring thepot in Europe and there literally are hundreds of reviews posted by people who have changed to them and I havent seen one review that says they would not change it back to anything they had..some see a big speed improvemt some not so much but they all say its far quieter and less vibration and also comment that the gearbox doesnt clunk at start and especially shutdown..the whole prop/ hub and spinner only weight 2.5kg...the bolly with the extension and spinner on the Sav is 6.5kg. The normal blades have a lot of drag apparently due to their width..this being so thin in width makes a big difference

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One of the big plusses about the Eprop is apparently everyone says its a lot quieter than any other prop..also less vibrations produced as well.

 

The thin blade at the tip givees you slip on takeoff so you can develop all the horsepower of the engine...this is what I am told...I am not across this indepth theory..the main part of the blade has quite a undercamber and a good constant helix in it...All I can say is it must work as they are certainly stirring thepot in Europe and there literally are hundreds of reviews posted by people who have changed to them and I havent seen one review that says they would not change it back to anything they had..some see a big speed improvemt some not so much but they all say its far quieter and less vibration and also comment that the gearbox doesnt clunk at start and especially shutdown..the whole prop/ hub and spinner only weight 2.5kg...the bolly with the extension and spinner on the Sav is 6.5kg. The normal blades have a lot of drag apparently due to their width..this being so thin in width makes a big difference

 

Something I haven't yet read, but expect to be true, is that with the thinner Eprops blades a plane would glide a significant distance further in the event of an engine failure (compared to the broader propellers).

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For anyone setting or checking propeller pitch the clinometer app on a phone is really quick and accurate.

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I use it all the time, great app and very accurate

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I don't know what they're comparing them with in Europe, but I have a 70" Bolly prop and I'm very happy with it.

I have it pitched very accurately, not with a digital protractor, but with a DIY laser projecting from blade to floor. It's a simple system, as accurate as you choose to make it and entirely reliable. At my prop height, 1 degree of pitch = 22mm of light movement on the floor. When last checked all blades were within a 2mm band.

 

I chose this method as I have reservations about some of the cheap digital measuring devices we now have: just because something reads to 0.1degree does not mean it is actually accurate to that. Further, when you try to dig back, there is often no published spec giving accuracy and repeatability..........

 

I have virtually no vibration and it doesn't start or stop with a clunk either.

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Yep, bit of exaggeration there: usually I get a clean stop by pulling to slow idle and switching the mags off in succession. Occasionally I do get a clonk. The only time I get them on start is if I fumble it.

I expect the later engines are easier on starts and stops, with the (crude but improved) ignition retard, and the gearbox slipper clutch.

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The blade on the right is a KIEV..

Last year, on a CH601 HDS (short/taper wings) with an ULS engine.

We went from a Warp Drive 68'', to a Kiev #263 ( 1710mm 67.3'' ) to an E-props Durandal 100

We saw better performance from WD to Kiev and from Kiev to E-props , similar numbers..but the E-props runs smoother , and have a less inertia than the Kiev .

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Less prop inertia has to be a benefit for what you are discussing. You don't want flywheel effect downstream of a gearbox. Cut from the lowest idle speed you can but don't sit there all day doing it.. Nev

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Just got back from the airfield. I will cobble together the video I have taken and post it to Youtube and post it here.

The weather bureau was just looking out the window again..supposed to be fine today...yeah NOT...been raining and showering all morning. So things were delayed and we only made 1 flight with 2 laps of the airfield between rain...was only spitting slightly

The video will show assembly and first running.

Danny has had an issue he has been chasing for a long long time of vibrations when running. He changed his 120mm alu extension 2 weeks ago and checked everything and used my Dynavibe to get it the best he could. He had some success in getting it better but still was enough to annoy him badly.

I should have filmed him after he got back from the very short flight.

The book says to start at 25.1 deg of pitch and to run the engine on the ground and adjust your pitch to reach 5500 rpm. So the 25.1 deg is the initial starting point.

The Savannah is hampered by a crap muffler and we have known for a long time we can not get all the horsepower from the 912ULS due to this fact. This fix is on its way now with different exhaust systems..this is relevant to this prop in an important way.

I set the pitch to 24.9 deg to cater for this loss of HP. The ground run produces just over 5400 rpm.. you can see this in the video

Interesting on this first run up after it he commented that thr aircraft was not bucking around and the skins were not being buffeted like they usually are when doing ground runs at full power which with the Bolly you had to pitch for about 5200rpm on the ground to get 5600 WOT in flight. Also depending on your climb angle the engine rpm would be different..shallow climb would be about 5300 pm and a steeper climb of about 60kts would give about 5150 to 5200 rpm

 

This prop makes this very different it is now like a constant speed prop

 

On takeoff he had 5400 and on climb it did not change it stayed there. The engine could deliver all the horsepower. He climbed at 60 kts and was going up at 1500 ft/min. on the downwind run he was WOT and it was 5400 rpm where he was level or pushing the nose down.

Watching the takeoff it certainly was shorter than normal..not by a big amount but certainly shorter and he also confirmed this. Top speed was about the same or maybe 1 or 2 kts better

 

We can not rely on these numbers as really we need to wait for better weather to start to put this prop through its paces but initially it looks really good.

The biggest difference that had him beaming a big smile was no more vibrations..all gone. Says its now like an electric motor or turbine it is so smooth..he couldnt believe it.

The acceleration of the engine is almost instant as well. Infact he thought that on takeoff he may have had a little cavitation but that was because he pushed the throttle too fast as the engine now performs so well, he didnt feed the throttle on.

 

The first thing he said when he got out of the aircraft was that he was now flying a different plane...he couldnt believe the change...how could the prop make it so much better.

The aircraft did not get the same buffeting as the other props..this has to do with the design and the way the blades load the power of the engine in its flow dynamics of the thrust lines. Even on the ground when you do your run ups the Savs buck and move a lot and the skins shake from the prop wash..it wasnt only his but mine did as well. It is very different now and at a higher RPM now as well.

 

Performance number we will still have to do some more testing but initial runs ....very impressive. 2 other guys were there as well..they were very impressed as well. Roger wants to try it on his Spirit now as well. He is keen and he doesnt need any extension

 

The only thing I have to see about is the spinner is not exactly centred it may have about 2mm or so run out at the very point but I am sure we will get that sorted but its not any biggie or will affect the results

 

Mark

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The smoothness is all good but some of the performance may be due to cold weather and a high over the place. I guess some of your anxiety has dissipated. Often people fiddle with Props and don't get much for the effort.. The previous one was a ridiculous weight.. With a reduction that's not say 2:1 (even) you may get a harmonic that comes and goes (as if you have more than one motor) but less noticeable.. Nev

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Yes Nev its a cool day and about 100% humidity so not a good day to get reliable test results. So hopefully next weekend we can do a lot more. But initially it looks to be really good. Being able to use all the horsepower now is a good thing..it seems to be like a poor mans constant speed prop by what we are seeing. Still need to try different pitch etc and I am going to get that slight run out of the spinner sorted. Danny is super happy just by fixing all the vibrations he has not been able to egt rid of at all. He has changed engine mount rubbers to a slightly less duro changed alu spacers changed props all will lots of attention to dynamic balancing and could never get rid of it. Now its super smooth..and the rpm operation is certainly different. We didnt expect a lot of speed improvement purely because the Sav is such a high drag aircraft but the really interesting thing is the now not buffeting like the other props did around the airframe. It is very noticable. You can see on the video at the 5400 rpm run ups the Sav normally bucks around like crazy on the ground when tied down... this didnt happen so there is a definate difference in the flow pattern from the prop. The video is uploading to Youtube now

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The boundary layer must be better. The normal fixed pitch probably has too high an angle of attack static, (no forward speed) at least on some parts of the blade(s) Nev

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The helix on the prop is quite different to any other props I have seen...I am no expert at all of course. I am told that the small size of the tip section allows for slippage and because the main part of the blade is also not as wide but does have a lot of pitch and undercamber this allows the prop to deliver the horsepower easier and a lot more....certainly seems to do so. But its not anything I know of...results is what I go on and so far its pretty impressive so far on what little time we have had to play with the prop

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