Propellers?

GallopingGhostler wrote:Don't know exactly where I read it, may even have been a posted by 1/2A Nut on either RC Groups or RC Universe. The post mentioned success using Bullnose props. The post mentioned that they were sturdy enough for 1/2A engine use. I don't know if they would be suitable for aggressive use like on a high nitro fueled .049+ Tee Dee, but am considering getting them for reed valve and possibly Medallion use.

Seeing these have a 4.5 pitch,  I have always used  5x3 props on my cox .049  Reedies, and they perform well.  Is the 4.5 pitch going to slow the rpms down and slow my 1/2A's down? Would the 4x4.5 prop be better?

oldguy wrote:Seeing these have a 4.5 pitch,  I have always used 5x3 props on my cox .049 Reedies, and they perform well. Is the 4.5 pitch going to slow the rpms down and slow my 1/2A's down? Would the 4x4.5 prop be better?

I used the example so folks would know what a Bullnose prop looks like, but not as specifics for any particular engine. I can't speak whether suitable for the Killer Bee and ultra high performance reed valves because I don't have them.

I have found that for maximum performance on moderate nitro fuels (i.e., 15% up to 25%), I've had good luck with standard 6x3 props with Babe Bee, Golden Bee, Black Widow and R/C Bee (Sure Start piston cylinder set). At sea level some 30 years ago, I found little difference between a 5.25x4 and 6x3 Top Flite white nylon prop (the one with the red letters and stripes silk screening.) As such, I used them interchangeably.

I've used 5.25x4 props and yes they will work, but found that at elevation, they produce less thrust than a 6x3. Some years back when I was living in Gallup NM at 6,500 ft. elevation, the 5x4 props barely pulled my Q-Tee along, struggling for altitude. As soon as I propped engine with a 6x3, it flew with decent speed and had a decent climb. This mirrors Peter Chinn's observation that a 6x3 is an optimal prop to use, within peak horsepower band.

Of course, with higher nitro, high compression glow heads, the paradigm may shift to 5 inch props as being more advantageous. Those who are high performance speed fliers would know. I don't, because I've never gone there before.

GallopingGhostler wrote:

oldguy wrote:Seeing these have a 4.5 pitch,  I have always used 5x3 props on my cox .049 Reedies, and they perform well. Is the 4.5 pitch going to slow the rpms down and slow my 1/2A's down? Would the 4x4.5 prop be better?

I used the example so folks would know what a Bullnose prop looks like, but not as specifics for any particular engine. I can't speak whether suitable for the Killer Bee and ultra high performance reed valves because I don't have them.

I have found that for maximum performance on moderate nitro fuels (i.e., 15% up to 25%), I've had good luck with standard 6x3 props with Babe Bee, Golden Bee, Black Widow and R/C Bee (Sure Start piston cylinder set). At sea level some 30 years ago, I found little difference between a 5.25x4 and 6x3 Top Flite white nylon prop (the one with the red letters and stripes silk screening.) As such, I used them interchangeably.

I've used 5.25x4 props and yes they will work, but found that at elevation, they produce less thrust than a 6x3. Some years back when I was living in Gallup NM at 6,500 ft. elevation, the 5x4 props barely pulled my Q-Tee along, struggling for altitude. As soon as I propped engine with a 6x3, it flew with decent speed and had a decent climb. This mirrors Peter Chinn's observation that a 6x3 is an optimal prop to use, within peak horsepower band.

Of course, with higher nitro, high compression glow heads, the paradigm may shift to 5 inch props as being more advantageous. Those who are high performance speed fliers would know. I don't, because I've never gone there before.

That's all I needed to hear as I thought that 4.5 pitch is to much for my reed valve engines, it won't let them rev up. thanks.

Reed engine bench test for speed, just an example I have many other tests
and flight vids to give you the best possible prop per plane / engine type.



Published on Oct 14, 2017

Cox Killer Bee Frame / TD .049 Cylinder -24,740 / HQ 4x4.5
Best peak 24,740 / 7.1oz thrust / 106 mph pitch speed / 93.3w
Nelson plug / 25% nitro / HQ Carbon 4x4.5 prop
SPI cylinder

Here is a linc to the old thread on Dal Props being used on IC engines

https://www.coxengineforum.com/t11371-can-these-be-used-for-glow-power#145083