Extreme Speed Prop Planes Discuss the need for speed with fast prop planes (Screamin Demon, Diamond Dust, Shrikes or any REAL sound breakin'''' plane)

speed prop??

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Old 10-15-2011, 04:36 AM
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James c harrell
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Default speed prop??

I am attempting to use a Hobbico Electristar outrunner motor on a canard pusher plane I am putting together. It is advertised as a .46 Eq. and is between 850-1000 Kv. I am useing a 4s battery and the motor is rated at a 11-7 prop. I need to go down in prop diameter and am looking at 9 preferably and 10 in. max diameter. My first thought was a 9-9 as the older, and wiser, guys in my club say to try and use a "Square" number prop for speed. So I went and bought a 9-9 and a 8-8 prop and have tested the 8-8. The motor pulls the 8-8 with no problem but I am not sure it has enough pull, or push in my case. I want to wait to get hold af an amp meter to make sure of the amp draw befor I put the 9-9 on. Just thought I would ask for some size advice from the ones that know. That would be you guys!! Thanks.
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Old 10-15-2011, 07:07 AM
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Default RE: speed prop??

I did a little testing on this thing. Let me add to start with that I am useing a 80A ESC.Results I have so far are:


9-9 APC prop, 4s 2200 Mah.
Volts-(At WOT)- 14.6
Amps-29.2
RPM- 9300

8-8 APC prop, 4s 2200 Mah.
Volts-14.7
Amps-20.3
rpm- 9900

10-6 Master Aiscrew, (GAS PROP) 4s 2200 Mah
Volts-14.7
Amps-20.3
RPM-9800

The 9-9 was noticeably more powerful but I think I can handle more. I need to find out what kind of Amperage the motor can handle. I am not anywhere close to the max amps of the ESC. You guys think I could move to a 10-10??
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Old 10-15-2011, 01:06 PM
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Default RE: speed prop??

james you have couple of problems here.

First is too small of a prop.
Second is to small a battery pack
third battery pack is only a 4 cell pack should be a six cell for speed.


if on that small battery then run a 10x10 to keep the amps down.

If still want to run only a 4 cell pack then go with more MAH and run a 12x12 prop http://www3.towerhobbies.com/cgi-bin...?&I=LXHAP9&P=0


If you really want some speed need to run a 6 cell pack of around 4000 MAh and a 9x9 or 10x10 prop.

Your electric motor is 800 Kv. your 4S pack with no prop the motor will only spin to 12,800 rpm. put a prop on it and looking at around 8,500-9,000 rpm
run the smae motor on a 6S battery and the motor will have a no load speed of 19,300. run that 10x10 at 14,000 rpm and be close to 130 mph.
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Old 10-15-2011, 01:53 PM
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Default RE: speed prop??

Thing with the bigger battery is the weight. I weigh 45.5 oz now with the 4s 2200. The weight on the kit was listed at 18-46 oz. I think the lighter weight is for the slope soarer version. By the way it is a Sig Tri-Star kit. I put in a few mods to add strength. I was thinking of a bigger prop but hadn't even dreamed of swinging a 12-12. Ought to be worth a try though!
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Old 11-02-2011, 02:21 PM
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Default RE: speed prop??

You have a really large electric motor on a light weight plane. can you post some pics and give some specs on the plane?

also run some electric props to get a bit more thrust at the low rpm you are running.
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