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Old 04-21-2014, 01:31 PM   #1501
patroller
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Absolutely noting dumb about any of you questions. There are a couple threads about tuning gas engines that helped me. I read as much as I could before I started with my first gas airplane engine (VVRC 40). Use the carb settings that VV set for you already when they started the engine. I did not notice much of a break in other that just a bit more power and smoother on the idle. No change in sound that I could hear.

As you know electric planes tend to be very reliable. In contrast gas engines can take some tweaking before the risk of a dead stick is acceptable. This is especially true if the idle is set a bit too low or you are just not an expert yet in tuning them. I know I am not and wound up with about 3 or 4 dead stick landings on my plane before I got everything sorted out. My problem was I was about 1 full turn to rich due the "expert" help of somebody at the local field. I am now real close to the factory settings and it runs great. I would keep things up high until you are confident. This plane lands easily without power if you are high enough. If you are 10 feet above the runway, well then good luck! I did some tumbles on my plane early on, but certainly not on the deck. My dead stick's were when I attempted hammerhead turns or other maneuvers at idle.

I essentially broke my engine in up in the sky. Overheating the engine on the ground does not make any sense to me. Fire it up and if the engine sounds good and is not hesitating on the advance from idle and is running smooth on the high end, and lastly the idle is set right, put it up in the sky. I varied the throttle for the first flights and avoided going to full throttle for more than brief periods of time. At 1/2 throttle the engine will haul this plane around the sky quite nicely. Towards the 4th or 5th tank I started pushing the throttle a little harder.

Good luck and have some fun.
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Old 04-21-2014, 04:46 PM   #1502
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I'm afraid I've already crashed my first attempt at this plane. I hate it when that happens! The good news is I'm almost finished with my second attempt, and with a spare fuselage, and other salvageable parts from the wreckage, I'll turn the wreckage into a backup plane.

One thing I wanted to add was that the new plane has a longer engine cowling. No more custom standoffs! I used the stock standoffs that came with the eme-35 and there's only a 1/8" gap to the spinner. There's been some discussion about that, and maybe EF got the message.

With a backup plane, I'll need a second engine. You guys running the VVRC engine seem to be using the same props I've tried on the EME-35, ie the Xoar 20x8 and Falcon 20x9. It wasn't exacting science, but I was getting between 6800 and 7000 with either of these props. For 75% more money to spin the same prop, tell me you guys are spinning it a whole lot faster. Otherwise this EME engine is looking pretty good.
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Old 04-21-2014, 08:00 PM   #1503
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Sorry to hear about your calamity. Why did the plane crash if you don't mind me asking?

The VVRC 40 will turn a 21x8 prop without a problem. Probably as fast as your EME on a 20". I also recall that it was lighter as well. The only other engine I would personally consider is the DA35. But if I was considering that option I would wait for the first hands on reports. There is a reason that even guys on this thread who have gone through a couple different engines on this plane have settled on the 40 twin. It is a perfect fit for this plane.
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Old 04-21-2014, 09:11 PM   #1504
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Thanks a ton patroller that information is certainly very very useful , and inspires confidence. Yup my engine is at almost factory setting, my buddy only richened it a bit for me , so i think it is exactly the way you described it. The throttle was very smooth and you are right i was only about 50-60% throttle and less most of the time in my first 4 flight. I have 2 different idle settings, one at ~2100 for in the air flying and one ~1700 on ground. This seems to be helping me. When i land i use the low idle and in the air use the little high idle. I am guessing based on the description my engine may already be broken in, i will pay close attention next time i fly. many thanks again for the info, i will search for the engine tuning threads and try to read up more . It's a different Gasser world out there and fun . I love the fact that i can haul the plane in the sky for double the time i would on my electrics. Will look at setting up Smoke in future.


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Old 04-21-2014, 09:21 PM   #1505
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Sorry to hear that dldeuce , i took everyone's advice on VVRC and i am not disappointed , agreed it is a bit on the high side for anyone outside of the US ( shipping is a bit high), but i think it is well worth the price and a lot of my friends are considering it here in singapore.
I am getting about ~6800 - 6900 RPM on the high side and low end is about ~1700 i can go lesser and it still runs fine. What i loved about this engine is the smooth throttle transition and i did not even set any throttle curve, just lowered the RPM at mid stick a little by setting 50% to 45% to make it linear and it worked well for the first 4 flights i had. I am loving it and thankful to the people on the thread for the invaluable info. Also PM'd joe he helped as well.


With your Xoar you may get a little less see the review here and the tested props by Joe.
http://www.3drcforums.com/content.ph...cc-Twin-Engine


After the DLE 30 debacle i did not think twice and bought VVRC twins immediately. If you are not on a budget go for it else EME 35 should work out well too based on the info i received earlier on the thread.


HTH


Quote: Originally Posted by dldeuce
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I'm afraid I've already crashed my first attempt at this plane. I hate it when that happens! The good news is I'm almost finished with my second attempt, and with a spare fuselage, and other salvageable parts from the wreckage, I'll turn the wreckage into a backup plane.

One thing I wanted to add was that the new plane has a longer engine cowling. No more custom standoffs! I used the stock standoffs that came with the eme-35 and there's only a 1/8" gap to the spinner. There's been some discussion about that, and maybe EF got the message.

With a backup plane, I'll need a second engine. You guys running the VVRC engine seem to be using the same props I've tried on the EME-35, ie the Xoar 20x8 and Falcon 20x9. It wasn't exacting science, but I was getting between 6800 and 7000 with either of these props. For 75% more money to spin the same prop, tell me you guys are spinning it a whole lot faster. Otherwise this EME engine is looking pretty good.
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Old 04-21-2014, 09:34 PM   #1506
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Quote: Originally Posted by patroller
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Sorry to hear about your calamity. Why did the plane crash if you don't mind me asking?
Some kind of radio problem. I couldn't find the problem. I've gotten rid of the ibec and split up the batteries for ignition and radio. I'm also suspicious of how I connected a Futaba RPM telemetry sensor to the ignition RPM output. The sensor worked, but I didn't realize I was also interconnecting the battery leads between ignition and radio. I'm going to try the sensor with just ground and signal, but no battery. Then I'm going to test the crap out of it, and hope for the best, unless I get any better ideas.

Quote:
The VVRC 40 will turn a 21x8 prop without a problem. Probably as fast as your EME on a 20. I also recall that it was lighter as well.
I've scanned through some threads, and I haven't seen numbers on the 20x8 and 20x9 props that look a whole lot different than what I'm getting now. What I'm looking for is some direct comparisons on the same props.

Quote:
There is a reason that even guys on this thread who have gone through a couple different engines on this plane have settled on the 40 twin. It is a perfect fit for this plane.
It's sure not the 75% higher cost or the 3.6 oz of extra weight, from the distributor specs. I have an open mind, but I just haven't seen higher performance numbers on the same props.
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Old 04-21-2014, 09:49 PM   #1507
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Quote: Originally Posted by iamamit
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I am getting about ~6800 - 6900 RPM on the high side and low end is about ~1700 i can go lesser and it still runs fine.
Which prop?

Quote:
With your Xoar you may get a little less see the review here and the tested props by Joe.
http://www.3drcforums.com/content.ph...cc-Twin-Engine
They didn't test the 20x8 or 20x9 props, and that's all I've had to compare with. Like I said, I've searched today, and folks are putting numbers out there between 6800 and 7000 for the 20x9 and 20x8 props, which is right in the ball park of what I was getting with the 35cc.
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Old 04-21-2014, 10:16 PM   #1508
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As I understand it there are differences between twin engines and single that make direct comparisons more difficult. A twin usually has more torque or power but is not able to spin quite as fast as a similar sized single. The result is the twin will push a larger prop better.

In the case of the VVRC 40 I am able to push a Vess 21a or a Mej 21x8 at 6850rpm's. I have not measure mine lately but I would not be surprised if it is even better now. As far as I remember the recommendations for this engine is to keep rpm's on the ground under 7000. My experience with a 20x8 xoar prop was less than optimal. I could hear the prop ripping through the air at full throttle and the prop would not unload very well when I got off the gas. It only stayed on the plane for about two days. If I were to try another 20" prop I would increase the pitch to 10 or look for a stronger prop than I had.
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Old 04-22-2014, 12:13 AM   #1509
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Having put in ridiculous amounts of time and fuel on the 40cc twins I can chime in on average peak RPM'S as follows. Keep in mind these are measured with an RCEXL tach plugged directly into the lead off the ignition ON THE GROUND on well broken in engines. Running Stihl HP Ultra synthetic at 40:1.

Hover CF 20x8 - 75-7600RPM (high but not too high, great all around prop)
Falcon CF 20x8 - 77-7800RPM (SUPER fast spool up and waaaaay to high an RPM...)
Falcon CF 20x9 - 71-7200RPM (great all around prop with lots of top end speed, punches out with good authority still)
Xoar/VVRC 20x8 - 73-7500RPM (most economical, throttle response is quick but not as snappy as carbon fiber)

I don't want to try a higher pitch 20" prop as the landing speed will be too ridiculous. Waiting on Falcon to release a 21x8 as I believe this will be the perfect combo of quick spool up due to the lower pitch as well as increased airflow over the surfaces when "low and slow." If anyone has a Mejzlik 21x8 laying around I'd be more than happy to test it out!!!
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Old 04-22-2014, 03:58 AM   #1510
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Am using Vess20B.


Quote: Originally Posted by dldeuce
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Which prop?

They didn't test the 20x8 or 20x9 props, and that's all I've had to compare with. Like I said, I've searched today, and folks are putting numbers out there between 6800 and 7000 for the 20x9 and 20x8 props, which is right in the ball park of what I was getting with the 35cc.
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Old 04-22-2014, 05:39 AM   #1511
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I have this airplane, and i have some interesting telemetry data for you all:
date of flight: 3/22/14
Engine: DLE 35 cc with bowman ring/reed block mods
Fuel / oil mix: 40 to 1 redline, 91 octane
altitude: 200 feet
ambient temperature: 75
prop size: 20 x 8 falcon
air frame: 78" extreme flight extra 300
radio system: Jeti

data:
1. high temp during flight (not after landing): 252
2. temp range 213 - 252 F
3. rpm range 3540 - 8760
4. rpm max during flight 8760
5. rpm max on the ground 7980
6. Rx voltage 8.40 at begin of flight, 8.19 at end of flight (2s lipo, TB, 1250 Mah each, times 2 batts)
7. Rx voltage minimum during flight 8.06 v

supatim, i bet you are getting over 8000 rpm on that VVRC 40 twin, you just do not know it. i was surprised to see that in the air, it got over 800 more RPM than on the ground.

if you can, get yourself some telemetry data sensors (green tree or spectrum) and log your data. you will be surprised to see what your airplane is doing.
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Old 04-22-2014, 06:48 AM   #1512
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Quote: Originally Posted by iamamit
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Am using Vess20B.
So what is your landing speed like with the 20B?
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Old 04-22-2014, 09:12 AM   #1513
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Quote: Originally Posted by supatimhanstine
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Having put in ridiculous amounts of time and fuel on the 40cc twins I can chime in on average peak RPM'S as follows. Keep in mind these are measured with an RCEXL tach plugged directly into the lead off the ignition ON THE GROUND on well broken in engines. Running Stihl HP Ultra synthetic at 40:1.

Hover CF 20x8 - 75-7600RPM (high but not too high, great all around prop)
Falcon CF 20x8 - 77-7800RPM (SUPER fast spool up and waaaaay to high an RPM...)
Falcon CF 20x9 - 71-7200RPM (great all around prop with lots of top end speed, punches out with good authority still)
Xoar/VVRC 20x8 - 73-7500RPM (most economical, throttle response is quick but not as snappy as carbon fiber)

I don't want to try a higher pitch 20" prop as the landing speed will be too ridiculous. Waiting on Falcon to release a 21x8 as I believe this will be the perfect combo of quick spool up due to the lower pitch as well as increased airflow over the surfaces when "low and slow." If anyone has a Mejzlik 21x8 laying around I'd be more than happy to test it out!!!
On the Falcon 20x9, I was getting about 6800 to 7000 on the ground. I didn't spend too much time before the plane crashed with the xoar 20x8. Those numbers are a little higher as well. Sure would be nice if they were a little higher still!
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Old 04-23-2014, 01:06 AM   #1514
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Quote: Originally Posted by Ohio AV8TOR
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So what is your landing speed like with the 20B?


For the 4 Flights i had it was certainly not very slow like my PA planes, but was fairly manageable and easy, i reduced the idle to about 1700 for landing and worked fantastic. It Floated nicely and did not stall or got sucked in to the ground as i have seen with other planes.
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Old 04-23-2014, 06:47 AM   #1515
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Quote: Originally Posted by iamamit
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i reduced the idle to about 1700 for landing and worked fantastic.
Thanks, good info as I am thinking of starting out with a 20B
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