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Old Jun 02, 2011, 01:42 PM
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Jocke's Avatar
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Originally Posted by super_nova View Post
Since I know a lot of electric flyers have been following this thread, whats the general consensus on 3 blade props? From what I understand, they are used on gas engines because they are less efficient, hence produce less rpms and less noise because the tips don't break the sound barrier [as easily]. But that sounds to me like an obvious no for electric when we're trying to maximize efficiency.

Just curious for the sake of conversation There's been a bit of discussion on the noise issue with the larger 2 blade props, and noise concerns in general lately.
I often use 3 blade on my larger planes, at a lower RPM im having a hard time to see that they are less efficient, what i like about a good 3 blade prop is, less torques/ prop disc effect, easier to fly "clean". Better acceleration, much much better braking effect on the downlines, less noise, better looks, and the RPM compared to a 2 blade that loads the motor same, dont produce less rpm, with a good 3 blade you get similar or higher rpm thanks to the less diameter and "mass" to swing.

I have had a few planes and setups where i have tryed Mejzlik 2 blade compared to 3 bade... and many times i feel much happier using the 3 blade prop and stick with that.
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Old Jun 02, 2011, 01:49 PM
The Eh Team
Ottawa, Ontario, Canada
Joined Aug 2000
954 Posts
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Originally Posted by Jocke View Post
I often use 3 blade on my larger planes, at a lower RPM im having a hard time to see that they are less efficient, what i like about a good 3 blade prop is, less torques/ prop disc effect, easier to fly "clean". Better acceleration, much much better braking effect on the downlines, less noise, better looks, and the RPM compared to a 2 blade that loads the motor same, dont produce less rpm, with a good 3 blade you get similar or higher rpm thanks to the less diameter and "mass" to swing.

I have had a few planes and setups where i have tryed Mejzlik 2 blade compared to 3 bade... and many times i feel much happier using the 3 blade prop and stick with that.
I would have thought that the pitch speed would be dramatically lower than with a 2 blade prop (simply because of the available prop selection of course, because one could always use a three blade that had a smaller diameter/greater pitch if it was available). How do you find that impacts the flight performance? I'm assuming you would be using something like the 27x12 thin three blade?
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Old Jun 02, 2011, 02:38 PM
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Joined Dec 2001
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Same pitch and same or higher RPM, speed is no problem. I have used the 27x12" TH 3blade, but also some regular 3blade from Mejzlik, and i find the "N" version to work very good also like the 29x12" N 3 blade on 10-16kw setups. Many times just becas of the great brake effect and less diameter i go with the 3blade instead of a 2 blade prop. On smaler planes i like the Aeronaut 3 blade folding props.

A big prop is good and efficient, specialy on paper and theory, but in reality a big prop can have a bad effect on a aerobatic plane and its flying performance, thats my experience.
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Old Jun 02, 2011, 03:01 PM
Jason
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United States, SC, Rock Hill
Joined Jun 2004
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What motors have you used a 27x12 3blade on? Mike from Hacker is the one who recommended the 29x12 for me with the a100-10 instead of a -8 and smaller prop. I have a feeling its going to draw a lot and I intend to limit my throttle end point to avoid unnecessary use. So I could probably swing a 27x12 3blade on my setup and see similar results to the 29x12. Unfortunately its quite the price to swallow for testing though on those props! Eric, its too bad we are so far apart, we could order one and have a testing day.

Looks like I'm going to be able to get out and fly tomorrow, so I'm going to work all evening on the final things left on my plane and maiden it tomorrow. Should have some numbers to share after that.
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Old Jun 02, 2011, 03:40 PM
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The 27X12" 3blade was my favorit on the Predator 30 on 14-15s setups. The 3 blade 29X12" N 3 blade was best for the PR37 on 14s, today i am using a smaler plane and a 12s setup with 30x13"EVO L prop and will soon try a 31x12" version. Im using a 3blade 24x12" on a Terminator on 10s and.

I have been flying the H9 Beast for a friend, and after som testing of 2 and 3 blade wood and carbon, we found the 29x12"N 3blade to be best for that plane.
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Old Jun 02, 2011, 09:24 PM
Team Hacker
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Vancouver BC Canada
Joined Jul 2006
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Originally Posted by super_nova View Post
What motors have you used a 27x12 3blade on? Mike from Hacker is the one who recommended the 29x12 for me with the a100-10 instead of a -8 and smaller prop. I have a feeling its going to draw a lot and I intend to limit my throttle end point to avoid unnecessary use. So I could probably swing a 27x12 3blade on my setup and see similar results to the 29x12. Unfortunately its quite the price to swallow for testing though on those props! Eric, its too bad we are so far apart, we could order one and have a testing day.

Looks like I'm going to be able to get out and fly tomorrow, so I'm going to work all evening on the final things left on my plane and maiden it tomorrow. Should have some numbers to share after that.
I found that the Xoar 27x10 (2 blade) provided plenty of power on the A100-10. I would think that a 29x12 would be way too much.

Good luck on the maiden.
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Old Jun 02, 2011, 09:30 PM
Barefoot Birkinsomething
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United States, CA, Hayward
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Originally Posted by Geoff Dryer View Post
I found that the Xoar 27x10 (2 blade) provided plenty of power on the A100-10. I would think that a 29x12 would be way too much.

Good luck on the maiden.
andrew jesky for a 104 slick on 12s with a 29x12 on the a100-10. i think im going to try a 27x14
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Old Jun 02, 2011, 09:31 PM
Jason
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United States, SC, Rock Hill
Joined Jun 2004
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Well the maiden is not happening now. Had my boss, who is also in the hobby, come over after work to help me finish up in time for tomorrow. With about half an hour of day light left, we took it out the back yard and set it all up for some basic testing and esc programming (running a CC ICE 160HV as was recommended by a lot of guys flying the hacker a100s).

Motor of course is turning backwards. So we hook up the programmer, update the firmware on the speed control, set up all the basic settings which have been recommended (outrunner mode, low timing, low acceleration, soft start, reversed the motor), and save it to the speed control. Disconnected the programmer and re-armed the plane. Start advancing the throttle maybe a total 6 clicks, prop is spinning... and then we see a large spark out of the speed control and then nothing.

We tried connecting the esc to the programmer again but it wouldn't register. So we brought it all inside. Removed the prop. Triple checked all connections and values. All my batteries were sitting at a storage charge of 3.8v so the speed control was seeing 45.7 in total. Everything triple checked fine, so we hooked it up to the programmer again. After a couple tries, it registered the speed controller, which had reset half its settings. Was able to set them back up but still no go on power.

So I'm pretty sure the speed control is fried. I just have no idea why. I'm going to call Castle tomorrow and hopefully they will replace it for me. I'm just going to be looking at several weeks turn around time to get a replacement up here to Canada I'm sure. Maybe I'll just pick up another esc and use that one as a backup.

As if my summer and winter haven't been busy enough. I was finally going to be able to fly and now this.
Jason
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Old Jun 02, 2011, 09:52 PM
Jason
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Yeah I talked to Andrew a bit about his setup a couple months ago, since its the same one Hacker recommended to me. Seeing as Andrew is a Hacker sponsored pilot, I guess that makes sense they would recommend it

He's happy with it and likes the constant speed of the large prop. I also brought up the weight issue since I would be flying 15Ah instead of the 10Ah he was using and he didn't think the plane would notice it much. I got the same response from Ben at 3DHS, their 103" extra will handle the weight no problem and it won't hurt for IMAC flying. Of course they want to sell me their product, but I also trust them not to give recommendations that would reflect poorly on their planes either.

I know the 29x12 will be way more power than a 27x10, but I don't intend to use that full power. With end point adjustments and a throttle curve, I can still setup a nice power band without going into extremes I would think...assuming I ever get in the air...
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Old Jun 02, 2011, 10:00 PM
Barefoot Birkinsomething
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United States, CA, Hayward
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Originally Posted by super_nova View Post
Yeah I talked to Andrew a bit about his setup a couple months ago, since its the same one Hacker recommended to me. Seeing as Andrew is a Hacker sponsored pilot, I guess that makes sense they would recommend it

He's happy with it and likes the constant speed of the large prop. I also brought up the weight issue since I would be flying 15Ah instead of the 10Ah he was using and he didn't think the plane would notice it much. I got the same response from Ben at 3DHS, their 103" extra will handle the weight no problem and it won't hurt for IMAC flying. Of course they want to sell me their product, but I also trust them not to give recommendations that would reflect poorly on their planes either.

I know the 29x12 will be way more power than a 27x10, but I don't intend to use that full power. With end point adjustments and a throttle curve, I can still setup a nice power band without going into extremes I would think...assuming I ever get in the air...
i know the feeling man....i have to move in a few weeks, and my 104 slick is soooo close to being ready. have to wait for a few funds for the motor/prop, and waiting on vinyl to get here so i can finish her up. im so ready to fly this bad boy!
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Old Jun 03, 2011, 09:59 AM
Jason
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United States, SC, Rock Hill
Joined Jun 2004
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I just got off the phone with Castle support. They said it sounds like a problem with the speed controller and it sounds like its most likely dead. They told me to mail it in, and it will be replaced under warranty. If they have it in stock, they will get the replacement mailed to me the same day or next day after they receive mine. At least they are good about that. And it looks like I'll be able to grab a backup one in the meantime from a fellow Canadian pilot who has offered to sell me one. So if that deal works out, maybe I'll be able to maiden next Friday...At least now I'll have a spare ESC in case anything like this happens again. Probably a good idea for contests anyways.
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Old Jun 03, 2011, 10:21 AM
Team Hacker
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Vancouver BC Canada
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Originally Posted by super_nova View Post
I just got off the phone with Castle support. They said it sounds like a problem with the speed controller and it sounds like its most likely dead. They told me to mail it in, and it will be replaced under warranty. If they have it in stock, they will get the replacement mailed to me the same day or next day after they receive mine. At least they are good about that. And it looks like I'll be able to grab a backup one in the meantime from a fellow Canadian pilot who has offered to sell me one. So if that deal works out, maybe I'll be able to maiden next Friday...At least now I'll have a spare ESC in case anything like this happens again. Probably a good idea for contests anyways.
Better that it failed before the first flight instead of during!
I had a ESC fail during the maiden of my 33% Sukhoi. thank goodness I had a lot of altitude at the time.
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Old Jun 03, 2011, 02:28 PM
Jason
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Joined Jun 2004
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How would I calculate what rpm a certain length prop is going to start ripping at? Is there a simple way to calculate it, or is more complicated then that? I found on online calculator, but it didn't seem very accurate.

Edit: Also, any tips for lightening a setup. I'm going to remove some wood from the motor box and see about shortening some of my battery lines to get rid of any needless weight there. Using 6 batteries means 6 series harnesses which is lot of weight in 10awg wire...

I've heard titanium axels and lighter wheels are a good option, anything else?
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Old Jun 03, 2011, 11:15 PM
Team Hacker
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Vancouver BC Canada
Joined Jul 2006
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Originally Posted by super_nova View Post
How would I calculate what rpm a certain length prop is going to start ripping at? Is there a simple way to calculate it, or is more complicated then that? I found on online calculator, but it didn't seem very accurate.

Edit: Also, any tips for lightening a setup. I'm going to remove some wood from the motor box and see about shortening some of my battery lines to get rid of any needless weight there. Using 6 batteries means 6 series harnesses which is lot of weight in 10awg wire...

I've heard titanium axels and lighter wheels are a good option, anything else?
- Replace the aluminum with a carbon fiber wing tube (also much stronger).
- No wheel pants.
- Other than that it is kind of hard to remove wood without damaging the covering.
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Old Jun 05, 2011, 08:14 PM
The Eh Team
Ottawa, Ontario, Canada
Joined Aug 2000
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- Replace the aluminum with a carbon fiber wing tube (also much stronger).
- No wheel pants.
- Other than that it is kind of hard to remove wood without damaging the covering.
+cf landing gear
.. and use smaller rx batts than recommended for gas; servos are not trying to stabilize control surfaces against engine-induced vibration. I use 6% per flight on twin 1600mAh 2S lipos; one could easily go a bit smaller yet e.g. two 1300mAh packs. I'm running hitec digitals all 'round. Flying electrics it's no big deal to recharge your rc battery every few flights. And, flying electric we're in there checking all the cells on the main packs anyway and it's no trouble to check all the cells on the rx packs before and after every flight so any unusual power consumption would be noticed right away. I don't think I've ever flown more than four flights without recharging so that extra capacity is just along for the ride.

I removed wood from the motor box too but the wood is so light it made no discernable difference. The main reason we need to do that is to ensure airflow back through the fuselage for cooling.
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