Author Topic: APC 12-6EP vs 13-4.5EP (Read 2701 times)

Mike Scholtes · « **on:** December 15, 2010, 10:59:16 PM »

The two props that seem most appropriate and widely used for stunters in the 650-680 inch range seems to be the APC 12-6EP and the 13-4.5EP. I have tried both on my E-Legacy and both work well, but I am running about 1000 rpm or more higher than what lots of guys are reporting with these props, around 10,500 to 10,800 to produce 5.2 laps on 65' lines. AXi 2826-10, various batteries (experimenting) in the 4S 3000 to 3900 range. We are putting about 2600 back in after a full pattern and 6 min 15 sec run.

So, is one of these props proving to be superior to the other, in models this size? What are the more experienced E people learning? Does one produce better drive, better corners, better overheads, and so on?

Both props have worked what seems really well for me but I would like to know what non-newbies are thinking.

Larry Wong · « **Reply #1 on:** December 16, 2010, 06:26:57 AM »

Mike: it seams that the higher RPM works better in the wind and has less wine up, but uses more battery, the lower RPM works good with less wind,others have just preference with RPM gain.more than anything is size of battery for weight .

Crist Rigotti · « **Reply #2 on:** December 16, 2010, 06:44:17 AM »

Shouldn't the pitch depend on what rpm you want to run your motor, especially if you are going with the 75% rule? You would use the correct pitch that gives you the desired lap times on the desired line length on 75% of max rpm for your motor and battery combination.

Dennis Toth · « **Reply #3 on:** December 16, 2010, 08:36:19 AM »

Mike,
The stock APCE 12x6P seems to be a bit lower in actual pitch vs the tractor prop and will require more rpm. I have been re-pitching to the pitch needed to get the lap time @ my fixed rpm (9000). What amp load are you pulling? Seems like you getting really good electron mileage.

Best, DennisT

Paul Walker · « **Reply #4 on:** December 16, 2010, 09:17:05 AM »

I have been using the 13 * 4.5 for the last year. I launch at 9500 rpm, for about a 5.3 lap on 67' ctc. Plane weighs ~60 ounces, and is 650 in^2.

I built a special prop pitch gage for it since it is a pusher. It said 4.5, and that is what it measured. However, there is significant undercamber to the cross section of the blade. This would make it seem like more than 4.5" of pitch. This is what I was doing with my carbon IC props for many years anyway.

If you have to launch at 10500 with the 4.5 pusher, something is not like my prop (which I measured). You might try another 13*4.5 to see if it works the same.

BTW, is your wing REAL thick, and requires LOTS of power to fly??? Is this plane very large? Something must require the power your are dialing in!

Paul Walker

Mike Scholtes · « **Reply #5 on:** December 16, 2010, 10:15:16 AM »

In reply to Paul (and thanks for the insight) the Legacy is about 680" with a moderately thick wing (but not like the TP or Strega, probably about 20%) with a quite rounded LE. I am at 60 oz or so depending on the battery in use. My pal Larry Wong is like the WalMart of batteries and has loaned me a variety to try out. Oddly, I need about the same rpm (close to 11,000) to get the same lap time (5.2) with both the 12-6 and 13-4.5. I do have three of the 13-4.5 so will try a different one.

One factor is that some of the folks reporting around 9000 rpm with these props to get appropriate lap times are using Pletty motors, which I understand are more efficient than the AXi.

Is there anything wrong, per se, in running an electric motor close to 11,000 with props in this size range? The AXi is rear mounted. While we're at it, is there any advantage to using 4S vs 5S batteries with a 920kv motor, in terms of ma consumed or any other parameter?

Wynn Robins · « **Reply #6 on:** December 16, 2010, 12:04:04 PM »

I've run both props on my kit built legacy - I found that the plane turns a LOT sharper with the 12x6 versus the 13x4.5

Jason Greer · « **Reply #7 on:** December 16, 2010, 02:13:09 PM »

You may have already done this, but if not you might try verifying with a tachometer that the actual rpm matches your esc or timer target with both props.

Paul Walker · « **Reply #8 on:** December 16, 2010, 05:03:08 PM »

Quote from: Jason Greer on December 16, 2010, 02:13:09 PM

You may have already done this, but if not you might try verifying with a tachometer that the actual rpm matches your esc or timer target with both props.

This is a great point. I assumed you were measuring the rpm, as opposed to what was programmed into the timer.

Q: How ARE you measuring the rpm?

Paul

Larry Wong · « **Reply #9 on:** December 16, 2010, 05:40:25 PM »

Great point we were using the programmer, I guess we will have to use both tach's to get an true RPM. Should have thought of that I did it on my own planes, must be a senior moment

Dennis Adamisin · « **Reply #10 on:** December 16, 2010, 08:24:07 PM »

Quote from: Wynn Robins on December 16, 2010, 12:04:04 PM

I've run both props on my kit built legacy - I found that the plane turns a LOT sharper with the 12x6 versus the 13x4.5

Try clipping the 13" to 12", add some RPM and you are good to go - and you keep the advantage of the low pitch.

Mike Scholtes · « **Reply #11 on:** December 16, 2010, 08:37:59 PM »

To Paul and all: I have to admit I did not pull out my tach to see what we are really getting; I figured the rpm was set by the timer without any need for adjustment. But it sounds like I better actually tach it. If I can't fly this weekend I will at least run it up in the garage (yea! electric!) and see what we get.

To Dennis: have you clipped the 13-4.5 and gotten good results? Must be, or else you wouldn't be suggesting it. I have enough of this prop (and Larry has 12 more) to sacrifice one to see what happens.

Dennis Adamisin · « **Reply #12 on:** December 17, 2010, 05:12:41 AM »

Quote from: Mike Scholtes on December 16, 2010, 08:37:59 PM

To Dennis: have you clipped the 13-4.5 and gotten good results? Must be, or else you wouldn't be suggesting it. I have enough of this prop (and Larry has 12 more) to sacrifice one to see what happens.

Yup. Using it on the Pathfinder test sled with Arrowind 2820; roughly 56 oz (depends on which pack) on 63' lines tuning 9600 RPM (in Set RPM mode) to fly at 5.3 sec.

Will Hubin · « **Reply #13 on:** December 17, 2010, 09:40:56 PM »

Recalling a previous thread on the change Castle Creations made with firmware versions later than 3.20, the High RPM calibration was then started at 20% throttle rather than 10%, so if you're using CC firmware after 3.20, you will have to dial in a higher prop RPM to get a lower tach value. In the latest version of the FM-9 Programmer, I've replaced the 1/2A Hacker calibration with the one that corresponds with this later firmware. This might explain any RPM discrepancy that shows up here. (I can send the latest microcontroller for the FM-9 for $5; it is easily replaced because it is socketed.) Of course, the main thing is to be able to get reproducible lap times and performance.

Mike Scholtes · « **Reply #14 on:** December 18, 2010, 12:06:56 AM »

Aha! I am using the newest CC software (3.27) and latest firmware (3.23) loaded into the PH-45. The FM-9 was about two months old, so this may explain the seeming disparity. Will just sent me a new FM-9 (which took the program instructions from the field programmer instantly) but I have not run it in the model yet. I will do that over the weekend but probably just a garage test due to inclement weather.

Shameless plug: We nearly all use Will's products, but this is an appropriate place and time to acknowledge Will's exemplary customer service and willingness to go to great lengths to make all this stuff work together and explain how to make it happen. I had a new FM-9 in my mailbox in NorCal three days after mentioning that I thought I was having a problem with my first one. No charge, not even postage. Great guy, great products. Let's make sure he can keep buying 100LL for his Decathlon.

Dennis Adamisin · « **Reply #15 on:** December 18, 2010, 05:27:32 AM »

Quote from: Mike Scholtes on December 18, 2010, 12:06:56 AM

Shameless plug: We nearly all use Will's products, but this is an appropriate place and time to acknowledge Will's exemplary customer service and willingness to go to great lengths to make all this stuff work together and explain how to make it happen. I had a new FM-9 in my mailbox in NorCal three days after mentioning that I thought I was having a problem with my first one. No charge, not even postage. Great guy, great products. Let's make sure he can keep buying 100LL for his Decathlon.

I'd like to add my appreciation for Wil Hubin to Mike's. Will keeps evolving his products to make them ever more friendly to use. He is extremely helpful and supportive as well as knowlegable about different products that his timers interface with. Most of all he is a very nice guy and good person to deal with.

As evidenced by his Contest Reports he is also a pretty darned good photographer & writer too!

Crist Rigotti · « **Reply #16 on:** December 18, 2010, 11:47:05 AM »

Ditto to what Dennis said.

John Cralley · « **Reply #17 on:** December 18, 2010, 03:42:53 PM »

Will is a gem and even though we have never met I consider him a good friend!! He has been very supportive of my fumbling attempts to work out timer issues.

John

Mike Scholtes · « **Reply #18 on:** December 19, 2010, 11:51:39 PM »

Larry and I ran the Elegacy in the driveway today and sure enough the prop rpm did not match the rpm set in the timer. So, reprogrammed the PH45 to Gov High and set 11000 in all three "head speed" boxes (still not sure this is needed). We eventually got the motor rpm to match the timer rpm. We now have 9200 in both the timer and real motor rpm. Now, back to the field next weekend (assuming the flood has subsided; high tide and storm surge nearly had us in the Bay) to try it in the air, and get back to experimenting with the 12-6 and 13-4.5 now that we are sure about rpm. Will also try a clipped 13-4.5 (to a 12) per Dennis' suggestion. We will report back as more data is collected.

Dennis Adamisin · « **Reply #19 on:** December 23, 2010, 08:32:10 PM »

Quote from: Mike Scholtes on December 19, 2010, 11:51:39 PM

Larry and I ran the Elegacy in the driveway today and sure enough the prop rpm did not match the rpm set in the timer. So, reprogrammed the PH45 to Gov High and set 11000 in all three "head speed" boxes (still not sure this is needed). We eventually got the motor rpm to match the timer rpm. We now have 9200 in both the timer and real motor rpm. Now, back to the field next weekend (assuming the flood has subsided; high tide and storm surge nearly had us in the Bay) to try it in the air, and get back to experimenting with the 12-6 and 13-4.5 now that we are sure about rpm. Will also try a clipped 13-4.5 (to a 12) per Dennis' suggestion. We will report back as more data is collected.

Hi Mike
One more suggestion: instead of "High gov or Low gov, I have had nothing but good luck using the "Set RPM" mode. Instead of trying to interpret the signal from the timer, Set RPM regulates the motor speed based on the what the ESC is sending and sensing. The motor & ESC is a far more accurate tach than the hand-held unit will ever be, and you will know exactly what speed the ESC is trying to sustain. You fill in those three boxes with the RPM's you want to see and can call them up using the timer to select RPM 1, 2 or 3

The only downside is that if you want to change any of the RPM's you have ptrogramed you need a PC - meaning a laptop if you change at the field. The good news is that you usually can home in on your prefer3ed speed within just a couple flights - and not worry about it anymore.

I think you are going to run the 12x6 around 8800 RPM so I would suggest programming in 8600, 8800, and 9000 RPM Fly a short flight at each RPM and see if you are geting what you need.

After you get you RPM set for the 12x6, add about 1000-1200 RPM for the 12x4.5 and give it another go, refining the RPM again...

Mike Scholtes · « **Reply #20 on:** December 23, 2010, 10:23:38 PM »

Hi Dennis:

Thanks for the clarification. I am still struggling to understand the relationship among the various CC modes, and then how the FM-9 interacts with those modes and settings. It will become clear with some experimentation. I will try your suggestion about setting rpm in the ESC, and then sequencing through them using the Hubin hand held programmer. We have 110V at the field and a nice picnic table area to set up the computer on, so that is no problem. I have the CC software in the computer.

I trimmed and balanced a 13 into a 12 x 4.5, giving it kinda squarish tips as close as I could to APC shape. Our little electric community is growing and we are learning as we go, GREATLY aided by the wonderful advice available on this forum. Thanks to all for the benefit of your experience.

As a side item, how are your Turnigy motors holding up? I have a 4250 650kv mounted in the China Clipper, maybe will be flyable by Spring.

Dennis Adamisin · « **Reply #21 on:** December 24, 2010, 06:30:00 AM »

Hi Mike
Keep in touch if you have any questions about the "Set RPM" mode. Once you get it setup it will seem clearer. In practice I strive to make the MIDDLE setting my "normal" then set the others at +100 and -100 RPM versus the middle. That way I can tweak it up or down as conditions require and know I am getting exactly the increment I want. I think this is golden.

I never had any problems with the Turnigy's - aside from one that crashed! I recently installed on of the red& blue series 3639's into a retrofit that needed a unique physical sized motor.

However, on the whole, while working on the Turnkey Electric Packages for Brodak I came to really respect the Arrowind motors. They are IMO the best outrunners made, on par with the Scorpions. They are physically a bit larger and heavier but that seems to have all gone into the structure of the motor. Very accurate on kv, rum perfectly smooth and quiet. We've also been working with Arrowind on a motor for the new EF-1 pylon racing class and it is proving to be the fastest and coolest running motor tested so far - but that is another story...

Mike Scholtes · « **Reply #22 on:** December 26, 2010, 09:37:40 PM »

We flew the Elegacy again today, with Set RPM selected in "governor mode" and 8600, 8800, and 9000 as the three settings. Using the 12-6EP and the middle setting selected using the Hubin programmer on the FM9 the motor appeared to sag on verticals or surge somewhat. Lap times were 5.3 on 65' lines so rpm was probably about 9000. Larry and I decided to reprogram the ESC back to Gov High, and entered 9000 in all three "rpm" boxes. We entered 9800 as the selected rpm in the FM9 programmer. We tached it at 9000 on the ground at full power after spool up. This produced 5.3 laps again, so it must have been turning 9000 when in "Set PRM" mode. Maybe I need to get the newest version of the FM9 that apparently allows you to dial in the rpm you want, and actually get that rpm.

I did not try the clipped 12-4.5EP today but will give it a test next weekend or on New Years.

Weather today was blue skies, 60 degrees, light winds. Tee shirt weather in December!

Dennis Adamisin · « **Reply #23 on:** December 27, 2010, 09:07:31 AM »

Not a big surprise there, the 12x6 would tend to "lug". BTW, in Set RPM mode, make sure you also have the Gov Gain set in the LOW or MEDIUM settings, it should help the responsiveness.