Author Topic: propellor testing results (Read 2573 times)

Mark Scarborough · « **on:** October 01, 2008, 11:11:23 PM »

Well I have been doing some experiments with props. Initially I started with Rev up 12 x 7 props. I pitched them to a true 6 pitch which is what the apc e 12x6 prop measures. Except at the root where it is slightly less than that, 5.7 or 5.8 pitch. I have the numbers. starting from the tip moving in toward the root, the numbers as measured on my prather pitch gauge are, 6, 6, 6, 6.,5.8,5.7,5.7,5.7,5.7. there appears to be a very small amount of Phillips entry on the blade leading edge, and towards the root there is some under camber, mostly at the root.
the props i modified basically mimic the pitch of the apc. I prepped three. I used different blade profiles based on past experiments with wet engines. Basic premise, develop the pitch desired, then thin the blades to where they feel "right" for flex at the tips. normally this ends up being about .090 thick at the tips, and about .120 at the third blade area. They are finished with two coats of epoxy, it is brushed on, and I rub them in while wearing latex gloves then wipe the excess off, letting it cure between coats.
Prop A this blade shape is similar to the scimitar shape of a standard apc prop, at least with proportion towards the tip. Normally I start with a prop an inch or so bigger than the desired finished size then I can more accurately replicate the sweep of the leading edge
Prop B basically a standard shape from the Rev up after re pitching.
Prop C this prop has a slightly steeper pitch, it is 6.7, the root is about the same, this prop also has a slight amount of undercamber.
I went flying Saturday and compared these three props with the APC in flight. I did use the eagle tree data recorder but based on the results in flight I haven't really explored the data as it basically was of minor important. I will follow up later with the flight data, suffice it to say, I was not impressed, my lap times were about .4 to .6 sec a lap slower. After talking to Pat Johnston at length, we concluded that perhaps the Phillips entry might be what was throwing the results off. Also Todd Ryan and I talked since he was there for the testing as well. His opinion was that my leading edge was to sharp.

I have posted the graphs from today's static tests without having really digested the data yet. My procedure was to run 30 sec runs at 9200 rpm while the airframe was restrained.
the first run was just as I flew it
second run, I softened the leading edge and formed a small radius
third run, I sanded a small phillips entry area into the leading edge. This is slightly less than 1/8 inch wide, and sweeps towards the top or face of the blade about 3/32" This is about as close to the apc entry angle that I could replicate.

so here are the graphs,,

The next step will be to take them out and fly them to get a feel how the variations in current draw correlate to actuall flight power.

Mark Scarborough · « **Reply #1 on:** October 01, 2008, 11:15:21 PM »

split them into a couple posts, it didnt like all of them at once,,,
feel free to comment on what you see, I am still digesting the information but thought I would share it with you anyway and post my thoughts after i have digested it for a day or so.

Alan Hahn · « **Reply #2 on:** October 02, 2008, 08:23:21 AM »

Mark,

I am dubious about pitches, especially as they pertain to the APC TE 12-6. Right now I am flying my Nobler with the APC TE 12-6 with the ESC set at 8000 rpm. If you calculate "pitch speed" it would say the maximum speed is 45 mph, but my lap time(5.1s) and circle radius (~62ft) tell me I am flying at 51 mph, or faster than pitchspeed. I use to think that pitchspeed was the maximum (no-drag airframe) speed you could obtain.

This says to me that there is more to the thrust of a prop than the pitch you can measure on a Prather Pitch gauge. I am not sure whether the discrepancy is how we measure pitch of a pretty under-cambered prop, or whether the prop might be deforming (increasing its effective pitch) in flight.

So here is what I would do (if I were you!). Setup your plane to fly with the APC (like you like it to fly) and measure the power you use. Then setup the plane with one of the wood props , adjust the rpm to fly the plane as you like and make the same power measurement. The one with the lowest power usage wins!

I know it takes a fair amount of time to do this, not to mention trying to keep the weather parameters close enough so that the comparison is sensible. Just as a comment, windy weather will use less power than a calm day! That's one reason why I haven't done more testing on props. Basically I have stayed with the APC TE series, but have gone to the largest diameter prop that I can fit on the Nobler.

I haven't played much with pitch in the 12" sizes since I am already running my setup at too low a rpm for my battery/motor kV. I could try the 12-8 with my 3014 725kV motor and see how that would work out (the 8000 rpm of the 12-6 was just a bit too high for that kV-4s battery combo).

Since the contest season is over here, maybe I'll do that, just to see whether a 12-8 prop at lower rpm is more efficient than with the 12-6 prop at a higher rpm. And keeps the overhead maneuvers feeling good. It will probably still take a week of good weather to be able to make some type of definitive statement.

Mark Scarborough · « **Reply #3 on:** October 02, 2008, 08:59:15 AM »

Alan,
good observations, and not far from where I was thinking. I too have come to realiize there is something I am missing. I plan on doing just as you suggested with the wood props. I too have wondered if somehow the APC was flexing in flight adding effective pitch ? I find it interesting that I need to turn over 1000 rpm more than you to get the desired flight speed. Although my all up flight weight is much higher than yours so that is in part the answer to that. There is also the potential that the static load really wont have any direct correlation to the in flight performance. This series of tests was basically to see if there were any marked differences in the variations of the leading edge, now I will fly them and see what changes it made in the flight characturistics if any are detectable.
I think the next true step will be to attempt to recreate the APC prop as accuratly as possible in wood. I to think there is some dynamic thing going on that I have overlooked. Its all basically and educational experiment at this point. I have a combination that flies great with the APC, though an airframe that was a bit lighter, ok a LOT lighter , would make me much happier. I have enough power, but the airplane is not as happy as it could be carrying that much weight.
At this point this is a development process. IN all honesty, sometimes the "failures" teach more than the success do. In this case, the fact that My magical custom wood props did not perform the way I anticipated leads me to further investigation that hopefully will help me to understand better what is actually going on. Oh for a high def ultra high speed camara that weighs like an ounce so we could mount it on the plane when it flies lol.
At this point I am not sure where I will end up. I have had great success with wood props on my wet engines. However, wet engines tend to self regulate to the actual pitch to some extent thereby clouding the results. In our case with the RPM govenor, it becomes a much moreaccurate way to get direct feedback from what we are doing,, Or should I say what I am doing. Not sure who else is out there torturing themselves to play with wood props like I am? Worst case scenario, I hope that when I get to the natural end point of this experiment, I will have gained some insight into the variables inherant in the props we use and why they act the way they do. I simply do not accept that its a "black " art. There are most certainly quantifiable variables that we can control. hence my experiments, and I hope others may find them interesting as well.
I am anxious to hear if you have any luck with your tests as well.
THanks as always for the feedback.

Dennis Toth · « **Reply #4 on:** October 08, 2008, 11:46:18 AM »

Mark,

I have also done some work comparing the APC E 12X6 (I repitch via heating and twisting to 4.7") to wood props. So far based on flying at a fixed rpm of 8800 rpm the closest to the APC E 12x4.7 is a Top Flite Power Tip 12x6. The Power Tip has a considerable philips entry and pulls quit strongly. I have tested a RevUp 11.5x5 (the old ST 46 standard) and it just didn't have any bit. I found some 7" pitch Zingers and they were just about the same as the APC E. It seems that the APC E 12x4.7 has about 1.5" of additional effective pitch vs a flat back at the same rpm. The PT's seems to have about 1" additional effective pitch over a flat back. One thing that is very different with electrics is the flight rpm. With wet power the engine unloads 500 - 800 rpm after release, our electrics hold the set rpm and back off the power. This makes comparing props a lot easier but different. For us as Alan stated the prop that pulls the ship at the correct speed and uses the lowest current is the better fit most of the time but we do need to check how it pulls through the up top maneuvers. This is were compromise comes in and it can be a little subjective as to how confortable one is with the line tension delivered. I am working with some thinned out Zingers cut down from a 13"x6 to 12.5 x6 to get a little wider blade and will see how it compares.

Best, Dennis

Mark Scarborough · « **Reply #5 on:** October 08, 2008, 01:23:31 PM »

Dennis, thanks for the comments,, all info is good
On your wood props, do you do anything to them , thin the blades, repitch, ?
I have found that typically, at least on wet engines, the blades on most wood props are to thick and leading edges to blunt to perform well. If you are interested next time I do a prop rework I will take pictures of the process.

Jim Oliver · « **Reply #6 on:** October 09, 2008, 06:34:25 PM »

Hey Mark,

Not doing E power, but interested in the prop rework for sure---please post!!

Thanks,
Jim

Dennis Toth · « **Reply #7 on:** October 12, 2008, 09:03:52 AM »

Mark,

Flew this weekend and tested some wood props against the APC E 12x5.5 (repitched from 6). My ship has 595 sq in, medium thickness (16%) wing a weights in at 58 oz. I use an AXI 2826/10 motor and a 4S1P 3875mah battery. Originally I had the ship set up with less power and 5oz more A123 battery. with this setup I used 62.5' lines C to C. That first setup used an APC E 11.5 x 5.5 (cut down 12X6) and would do a 5.0 lap time. Over the past month I switched to the lighter LiPoly battery and stronger motor and a full 12" diameter APCE prop. The first few lights were with the 62.5' lines and with the 5.5" pitch and were at 4.8 sec lap time for 5min 40sec flight time pulling around 2650mah from the battery pack. To take advantage of the new found power and battery capacity I tried 66.5' lines, this resulted in 5.3 lap time which for my taste was just a tad slow. I then reduced the line Length to 64.5' and increased the pitch to 5.8". That seems like the right line length for this ship but the pitch increase kicked the speed up to 4.9 sec laps. I have now brought the pitch down to 5.65" and expect to hit 5.0 lap time.

Now comparing the APC E 12 x 5.5 to the wood props, on the 66.5' lines the Top Flight 12x6 (stock except for balancing) was a disappointment with a lap time of 5.4 sec compared to the 5.3 of the APCE. The new TF's don't seem to have the same amount of philips entry and the machining is sub par. I also tried a Zinger 13x6 cut to 12.5x6 (stock except for balance), WOW did this prop pull. Even with the square leading edge and thick trailing edge it had a lap time of 4.9sec on the 66.5' lines, only problem is the current draw (static test) for this prop is 20% higher (48 amps) then the APC and TF (37 amps) which is to much for my battery (10C rating). I might try to work the Zinger blade to thin it and smooth the leading edge and thin the trailing edge and see what happens to the current draw.

One thing you might want to keep track of when you test your props is the current draw. It seems you can tell a lot from this as far as prop pulling power at specific pitch, more current more pulling power. It will be interesting to see how your results compare, please post.

Best, Dennis

Alan Hahn · « **Reply #8 on:** October 12, 2008, 09:40:30 AM »

I find it interesting to see what seems to float everyones boats! I like to play with motors, and you guys love props. Now we need to pull it all together for the ultimate!

Mark Scarborough · « **Reply #9 on:** October 13, 2008, 08:40:34 AM »

Well bad news for me, My testing program may have hit a snag. I took my EP-40 to the Fall FOllies this weekend, Intending to fly it in competition again, and to do my next phase flight testing for my props. Regreatably after my first flight friday afternoon, when I landed my battery was much warmer than I am used to, and the flight shut off seemed to come up against the LVC. I did some examination, it appears I may have lost a bearing in my motor which will have possibly rendered my previous tests somewhat inacurate. I am not sure when it started going, this was a used motor when I bought it that was supposedly only ran a few times. However no way to know how hard it was run. So now I need to find another motor. I may look into something that is wound for a bit higher KV. I really have liked running props in the 4 to 6 inch pitch range, as measured on the gauge. Still not sure.
Does anybody know if you can get inside the AXI motors to check the bearings. When I spin my prop, it makes a definite whirring ratcheting sound that wasnt there before. There is also some telltale black and metallic dust on the cooling openings which may be an indicator as well
FWIW I was running my baseline setup that normally barely heats the batteries.

Mike Anderson · « **Reply #10 on:** October 13, 2008, 09:02:17 AM »

It sounds as if the magnets are hitting the stator -- a bad bearing could be the cause of this, or anything else that allows the shaft to whip in flight - I've had it happen just having the prop go through a "resonance" RPM, where there is a bit of vibration that smooths out as it gets to higher RPM. It only takes one time, and there can be enough whip to allow the magnets to strike the stator and either chip or get knocked loose.

I would advise that you pull this apart before you try to run it again and determine that all is running square and true. (Scorpion motors with the large rear "bell housing" bearing were very prone to this when they first came out. Part of the problem is mounting the motor "firewall" style, with the wires at the rear. Part of the problem MAY also be traced to heavy props - lowers the resonant frequency into our RPM range. I don't like to run "gas" props, for this reason, though I know that many have used them without trouble. I really prefer to stick with the "E" props.)

Best of luck --

Mike A

Mark Scarborough · « **Reply #11 on:** October 13, 2008, 09:25:29 AM »

Mike, thats almost what I suspected. Now my question, do you know how to get inside this beasty,there aint no head bolts,, lol,,

Alan Hahn · « **Reply #12 on:** October 13, 2008, 01:15:22 PM »

Mark,
All you need to do is to remove the circlip (or whatever it is called). Then carefully pull the two halves apart. The magnets really pull the two pieces together but steady force will do the job.

Then if you replace the bearing, be careful when you put the two halves back together. That same magnetic pull on the stator can get away from you and if it does, the bearing can get clobbered when they click together.

Mark Scarborough · « **Reply #13 on:** October 13, 2008, 01:17:13 PM »

Thanks Alan

Dennis Toth · « **Reply #14 on:** October 19, 2008, 05:09:55 PM »

Guys,

Did some interesting prop test yesterday on the Excitation (600 sq, 58oz). The base test prop is an APCE 12x6 repitched to 5.8", set at 9000rpm (fixed rpm mode on CC45). On 63.5' C to C the lap time is 4.8 sec. This was a bit fast so I set up three props to test, another 12X6 APCE repitched to 5.65", a 12x6 Top Flite PT and a 13x6 Top Flite PT cut to 12". All are set at 9000 rpm. The big winner was the Top Flite 13x6 cut down to 12", it had a lap time of 5.0 and very strong up top tension, it also pulled the most static current at 43 amps, pulled 2950 mah out of the 3850 pack. The big loser was the Top Flite stock 12x6 at 5.3 lap time. The other very good performer was the APCE 12x 5.65 it had a lap of 5.05 (2696mah from pack) and was pretty strong up top but not as good as the cut down 13x6 TF. It seems that the wider blade of the cut down 13x6 TF gave a little better up top. I have done some work on the cut down prop to thin the thickness and hope to reduce the amps but maintain the pulling power of the additional blade width. Last prop I tested was a cut down and repitched APCE 13x6 to 12x5.8. This gave very very strong pull and a lap time of 4.8 sec. I did not put in a full pattern with this only a 1min test flight. I will reduce the pitch and do some amp tests next and hopefully do some flight tests this week.

Best, Dennis

Mark Scarborough · « **Reply #15 on:** October 19, 2008, 07:47:34 PM »

Good information Dennis,,
keep up the good work . Alas, my motor woes were not as simple as a bearing. I got the motor apart and have lost two magnets. Aparantly I was told that my AXI is one of the older ones that was prone to this problem. I have a Hacker that was loaned to me by a local RC flier to try. On paper it looks comparable, though perhaps a bit stronger,, right now just looking to mount a venturi on it,, oh wait, that wont work lol,,
Just kidding guys,,
I am working the mounting out , its a bit larger case than the AXI so my mount wont work asa is. I think I will be able to reverse the mount and put new inserts in the mount rails so that it will still work.
More info as I progress,,

NED-088 · « **Reply #16 on:** October 23, 2008, 06:33:28 AM »

With all this focussing on lap-times, did you guys actually measure speed (or better: speed variations) during the manoeuvres?
Because that defines quality of flight to me.
I've been flying planes in the past that flew around 5.0 laps (max. lines, of course) yet nearly fell from the sky in a vertical eight. And also planes that went 5.5 while almost pulling your arm off during the second corner of the hourglass.....
I'm not happy with either situation, but having flown competitions with electric power for over 2 years now, I've optimized the standard set-up to a point where it flies (near) perfect in (near) perfect weather (WCh 2006) but still becomes a dog in rough circumstances. (WCh 2008 comes to mind

)
So we're searching for ways to maintain speed when flying against the wind (a governor effectively shuts down then).
It's amazing to find that it took us about 6 weeks back in 2006 to get the set-up to work at 95% of it's potential and that the remaining 5% are keeping us busy for over 2 years now....

About the props: I found only 2 types suitable: APC-E and Graupner CAM, the latter being my preferred ones up to now, but that might change.
All (wood) props, developed originally for IC, gave a lot less efficiency, more power consumption for a given thrust.
After one afternoon of flying and one afternoon of benchtesting we chucked them all....

Mark Scarborough · « **Reply #17 on:** October 23, 2008, 08:41:11 AM »

Of course you are correct about line tension, and manueverability. However lap times is a way to get in the ballpark. I did note one interesting thing with the P-40 and the APC 12x6E prop, I was initially flying .2 sec slower times and had equal line tension overhead at the slow times, and this with an airframe that was 5 oz heavier than it was as a wet airframe. Goes to speak of what you refer,, its not all about line tension, but the ability of the drivetrain to maintain thrust and speed. I believe that with the electric I was not loosing as much airspeed in the manuevers as I did with the wet motor. That would accomadate for a portion of the difference.
As to wood props, I would agree almost completely that stock wood props are not suitable for our application, however It believe with a bit of work that wood props will also prove suitable, if you are of a mind to spend a bit of time on them.
However as stated many times, repeatability is one issue. Of course, if you dont dink your prop then you dont need a backup,, lol

Alan Hahn · « **Reply #18 on:** October 23, 2008, 08:47:12 AM »

Somewhere in some post

in this forum I posted my data recorder from a flight. The data included an airspeed indicator. I'll try to find the particular post. added later---here is the link---it includes the propeller calculations as I talk about below

http://stunthanger.com/smf/index.php?topic=7574.0

What the data showed me was that in one of my square maneuvers, the airspeed was dropping until the plane reached nominally 45 degrees or so (there was also an altimeter---but to be honest, there was something flakey about the way the altimeter is working--as well as its resolution.

The conclusion I came to was that:
1) Most of us have no clue what the airplane speed is in flight---we fly by feel
2) Unless something fancy was going to be added to the speed control (like an rpm boost in a square maneuver), the best insurance against loss of line tension was a good propeller. The characteristic to be desired is a prop whose thrust, at a constant rpm, increases rapidly as airspeed decreases. I also posted on a propeller thread in this forum, some calculations done with "PropCalc" with just this idea in mind. The conclusion there was to put the largest diameter prop on that you can take off (and land!) with. That's why I am using a 12-6 APC on my 44oz Nobler. It seems to fly well.

NED-088 · « **Reply #19 on:** October 23, 2008, 03:20:01 PM »

Indeed, a better adapted prop gives less loss of speed, hence a more constant line tension through the manoeuvres.

To illustrate: The change from 12x6 with Kontronik Jazz 55 to 12,5 x 6 with MGM 4416 made my loops so much rounder as compared to how they were with the first setup. The Kontronik has a slow governor that doesn't compensate for lost airspeed anywhere near the way the MGM does. The larger prop puts this improved governor response to work.

But we should realize that we're talking rotation, degrees per second here, groundspeed , not airspeed.

In dead air these would be the same, but when the windspeed increases, you'll need to manipulate the airspeed through the pattern to keep your groundspeed constant.

Manoeuverability also depends on airspeed. Less airspeed, less turning power for a given control input. So you want to keep your airspeed constant.

In the end we'll have to compromise between these effects. Like we did (to a certain degree) with IC engines. Time to put the cherry on the cake and make the perfect electric powertrain.... Igor and Paul are the closest at this very moment, I think....

So I'm digging myself a way through all this thinking......

Meanwhile the field testing continues, but suffering from the weather deteriorating quickly now.

Dennis Toth · « **Reply #20 on:** October 24, 2008, 12:58:05 PM »

Guys,

I agree that constant maneuvering speed is the goal. Actually I think that re-acceleration is very important in prop performance. To that end I have been starting with lap time and feel, then looking at maneuver line tension. I have been trying to set the prop to the largest diameter that keeps the current draw within the battery capability. Diameter is king for line tension and square tip props also add up top tension. I have found for my ship that the APCE 12x6 and 13x6 props, cut and repitched to the 12x 4.6 size have very strong pulling at around 39amp. I also found that the wood props seem to be about 1.5 inch less effective pitch then the APCE's but if the pitch is increased to match the effective pitch (i.e. use a 7") they work also. Blade width also seems to be a big factor in up top line tension, the trick is to get the largest diameter widest blade that the motor / battery will allow and still stay in governor control range. Once you top that out if the ship is slowing down you need more motor/battery.

Best, Dennis

Dennis Toth · « **Reply #21 on:** October 27, 2008, 10:18:10 AM »

Guys,

Weekend update - As an old girlfriend of my flying partner use to say " length is OK but thickness counts too" ! This holds true with props also. Did some flight tests on the modified Top Flite 13x6 cut to 12x6 that was very strong in its stock airfoil thickness but it pulled 43.4 amps. In an effort to reduce the amp draw I maintained the wide width blade shape but thinned the airfoil (only the high point back, no change to the philips entry) about 15%. This dropped the current draw to 38 amps (@ 9000rpm set point) but the flight test was a surprise, increasing the lap time from 5.0 to 5.35. I also tested the cut down APCE 13x6.5 set up as 12x4.5, this prop was very strong with a lap time of 4.8 but current draw was high at 47 amps (I repitched to 4.25 and current dropped to 41 amps, need to test fly). This prop has lots of undercamber so the effective pitch is around 1.5" higher then the flat back measured pitch. Bottom line is that airfoil thickness and or undercamber have a major impact on the effective pitch of the prop. One other variable that needs to be looked at is air density as it varies with temperature.

Most of my flying has been at 75F in the early morning. As it gets hotter we may need to either add diameter or rpm to compensate, with cooler days ahead props that were weak in the summer may turn out to be great. This may be the one disadvantage of our dead one speed type run. With wet power as the conditions change the engine will to some degree adjust it "Unloaded" rpm and mask the efficiency loss of the prop. This is why some people were able to run one needle setting for the whole year. For ECL we may need to have several props adjusted for temperature or multiple ESC's with rpm set points for different temps (the new Ztron ESP with the rpm pot seems like a great option). Is there any way we could have a simple inexpensive programing chip that could be set to different rpms from the main setup program that could be simply plugged in at the field to change the rpm set point? That would be a neat option.

Best, Dennis

Mark Scarborough · « **Reply #22 on:** October 27, 2008, 10:50:41 AM »

Dennis, good info all! I will digest more thouroughly when I get home, they kinda frown on to much time on this at work ya know?
as for the chip , yes something like a MSD ignition rev limiter would be interesting, However, The new Ztron with the pot is REAKLLY slick. I have one and you just tach it like you do a glow motor, there is a plus or minus 500 rpm range which should cover all you may need for air density variations. I would think that in lower density air, stepping the rpm up to compensate should still keep your current draw approximatly the same since the load on the prop is reduced (hence the need for increased rpm) I am still in a state of no test, working on converting from the AXI to the Hacker motor, on hold now for the gold bullet connectors to make the connection from speed control to motor. then my testing will hopefully resume,, till the weather lets go anyway,,

Dennis Toth · « **Reply #23 on:** November 02, 2008, 11:10:10 AM »

Guys,

Did some additional prop flight tests today and basically confirmed what the first tests showed that thickness plays a major part in thrust for flat back ECL props. I tried to take some of the props that had poor performace and added undercamber. Since the blade was fairly thin I couldn't get to much under camber but it did help but when compared to the full thickness prop it was still less thrust. What was interesting was that the APCE 12x5.65 (repitched 12x6) was very strong in the wind and pulled the lowest amps (33.5amps @ 9000rpm). The Top Flite Power Tip 13x6 cut to 11 7/8 x6 was the second strongest but pulled 41amps and matched the APCE for lap time at 5.0sec (66ft C to C), it did however seem to wind up a little more the the 12" APCE. The last test was the cut down APCE 13x6 cut to 12" repitched to 5.6. This prop is very strong but still has to much pitch producing 4.8 lap time and pulling 44amps. I have recalculated the needed pitch for this prop and reduced it to 5.4" and hope to test fly later this week. For now the APCE 12x6 pitched to 5.65" is my base prop.

Question, what is the effect of lower rpm on with higher pitch on thrust? To use the stock APCE 12x6 the rpm for my ship would need to be reduce to around 8500rpm. Has anyone compared lower pitch higher rpm to higher pitch lower rpm?

My sense is that as with any airfoil it is happier at the higher speed and should accelerate out of a corner back to flight speed a little quicker. But the change is only about 5% in rpm so this might not really show up.

Best, Dennis

Alan Hahn · « **Reply #24 on:** November 02, 2008, 12:44:51 PM »

I'm flying at 7950 rpm with the APC 12-6TE and am very happy with performance. No windup in moderate winds (up to 10mph--yeh, I'm a wimp!) that I notice. I have yet to notice the governor hitting 0 Amps in a dive in a wind, so the motor is still having to put power in to keep rpm constant. So I claim that there is still braking power left to have.

I am not too sure where all our prop folklore comes from. Since we are running on governor mode, I believe that most of what we "believe" about props is at best an illusion.

From what I have looked at from prop simulations, there is no way you can keep constant airspeed in a climb, even a 1000 rpm boost gives a thrust increase less than 1/2 mg---the vertical force of gravity when the nose goes vertical. To some extent the level lap speed we fly is such that the lost airspeed in a climb isn't enough to make the vertical maneuvers feel too uncomfortable.

Author Topic: propellor testing results (Read 2573 times)

Alan Hahn

Alan Hahn

Alan Hahn

Alan Hahn

Alan Hahn