PDA

View Full Version : oversquare props...where..?


watt_the?!
10-31-2005, 06:33 AM
anyhone know where over square props can be purchased?

i.e. 4x6, 4x7, 4x8, 5x8 etc etc...

timocharis
10-31-2005, 10:19 PM
Theoretically they're a bad idea. Does anyone make them?

Dave

Jason T
11-01-2005, 03:21 AM
I know I have seen over square ones close to those sizes but for now I can only find some that go over square at 7" diameter at APC's website:
http://www.apcprop.com/cgi-bin/store/agora.cgi?maxp=1000&ppinc=6a&product=+

*****edit*****
Okay, I found more over square props from a different website:
http://www.ecubedrc.com/propsandadaptors.htm

watt_the?!
11-01-2005, 04:58 AM
i see a 5,25 x 6.25 there!

Jason T
11-01-2005, 12:01 PM
Unfortunately, I do not know where to get the smaller diameter ones you mentioned.

fdix
11-01-2005, 02:30 PM
RFM carbon folding props come in over square sizes. Smallest over square size is 12,75x13 tough.

watt_the?!
11-02-2005, 01:13 AM
Unfortunately, I do not know where to get the smaller diameter ones you mentioned.

no these are good!

Tim

roccobro
11-02-2005, 07:52 AM
What is this for? :D

Justin

watt_the?!
11-02-2005, 09:22 AM
just for some help for another poster and his stryker....its in the delta wing forum.

nothing top secret...

Matt Kirsch
11-02-2005, 12:44 PM
Anybody know the technical issues behind why oversquare props are bad? I'm curious.

rcers
11-02-2005, 02:43 PM
Anybody know the technical issues behind why oversquare props are bad? I'm curious.

Nothing bad about them, you just need to understand that the prop will remain stalled at low speed. But man when they come "on the step" it is a sight to behold.

Good for fast slippery ships. Bad for others.

In fact in e-flight I have learned that I use the highest pitch props I can for 90% of my planes. I like being able to throttle back and maintain some speed.

Mike

watt_the?!
11-02-2005, 05:39 PM
soemthing to do with the reynolds number and the function of the diameter and the pitch ratio where approx 2:1 is best and anything less than that is approaching ''bad''..hence 1:1 is not good and less again is ''very bad''.
unless you're a pylon racer of course.

mrfx2001
12-03-2005, 03:07 AM
I had a flat-out that lasted 9 flights. This is not my kind of flying. I now have a rim fire and all the running gear and was wondering what to do with it. While kicking around the garage I unearthed an electric flyer that I built in 1983 during my first divorce. (Therapy) The model was meant for speed 480 and a load of NiCad’s. The aircraft name is Fast Eddie. I picked it up at the Toledo model show that year. (Back in the days of the ARENA) It has a 7.75” cord and 36” of span. The thickness is 3/4” and was built very light. The aircraft was meant for speed as the kit clamed 100 mph in dive. (It will do it too.) I put the Rim fire on it and balanced so that the battery could be changed without affecting the balance. Propped 9-6 E the aircraft flies like an open .15 combat ship.
(Now that’s my kind of flying.) Power is from a 3 cell 6xx ma. LIPO. Not having a feel for electric motor to ci. Disp equalities, could someone offer up if I have the model propped correctly for the rim fire. The rim fire is plenty of motor and may perform better with another prop. I am thinking that an above square prop might be better.
Fred

timocharis
12-03-2005, 06:18 PM
Fred,

I don't own one of those motors, but the 3s specs list 8x6 tops in the "speed" prop department. They're probably right, too. The motor is designed to be 'thrusty' rather than 'speedy' at 1000Kv, but there's no reason to let that stop you. Going from 9x6 to 8x6 should lower the current draw a bit while giving more top end. Might be worth trying an 8x8E, but I have my doubts about it giving an improvement. I'd think something along the lines of a 7x7 or better would be nice, but have no idea where to get one.

If you like speed, something in the 7x6 range is worth a shot, though with that low Kv it might not happen. You never know 'til you try, though.

Dave

watt_the?!
12-03-2005, 10:31 PM
the 8 x8 will be faster...no doubt...but far less thrusty.

timocharis
12-04-2005, 05:02 AM
Tim, I'm not so sure it would be faster (though I'd like to hear one way or the other). My experience in the 1000Kv area is, you push the motor a bit too hard with too much pitch and it actually slows down. Or at least, that's been my experience.


Dave

watt_the?!
12-04-2005, 05:57 AM
itll be faster...the load increase by an inch of pitch is minor and doesnt result in much of a drop in voltage, whereas the change in diameter does...4 fold...

if the battery and motor are optimised, then v drop will not be an issue, and it comes down to the translation of power which is absorbed by thrust and pitch speed...diameter and pitch.

Azarr
01-02-2006, 06:39 PM
In the "E" series, there are several square props i.e. 4.75 x 4.75 and 5 x 5, 8x8, 9x9, 10x10 and 12x12. There are only two oversquare, 4.7 x 5.5 and 5.25 x 6.25. There are a bunch available in the glow "sport" series and "racing" series, but they are significantly heavier.

I have all the APC "E" and "Slow Fly" props in stock from 4.1" - 27"

Azarr
www.ecubedrc.com (http://www.ecubedrc.com)