More prop testing

[JG3]

The real difference that I was wanting to test this time was the static thrust. Previous testing had found that static thrust gives no real indication of cruise or climb performance. But of course it does make a difference in short takeoff performance. That initial thrust makes a big difference in how quickly the aircraft gets rolling and up to flying speed. With the popularity these days of seeking impressive STOL performance that could be significant.

 

So I purchased a digital load cell and set up a ‘stump pull’ arrangement to give all props equal conditions.  The differences in ‘grunt’ are significant, as detailed in the full test results at https://www.stolspeed.com/nid/46

 

This time also testing a couple of new scimitar-shaped props from Meglin, being imported from the Ukraine by https://www.bushaero.com.au

 

[rodgerc]

Ah the D-block “stump” with it’s hi-vis extension for dills like yours truly who cut the corner. 
 

Interesting results, as usual, thanks JG. 

[APenNameAndThatA]

You have gone to a huge amount of effort. What motivates you? 

[APenNameAndThatA]

I noticed you had a testimonial about VG’s and a Foxbat. IIRC, the factory tried VG’s but ditched them because they messed up the stall characteristics. Thoughts? 

[JG3]

On 11/01/2022 at 9:25 PM, APenNameAndThatA said:

You have gone to a huge amount of effort. What motivates you? 

Good question. I started out many years ago hoping to discover the very best prop. Was surprised to find initial testing showed all props tested were pretty much equal. Eventually tested 11 different props and same results. I'm annoyed by hearing claims that I can tell aren't based on credible testing. Then it became an obsession as more and more repeat testing proved results over and over again.  Fascinating results from an engineering aspect, but I'm sick of bolting and unbolting props! One more report to come from testing already done regarding the difference between pitching to 5800 or 5500 rpm WOT, but then I'm absolutely done with prop testing...... After all that, I'm still flying the same prop that I started with 11 years ago, and wouldn't change for anything.......

[spacesailor]

Did you try the ' SCIMITAR ' Prop. 

IT IS RUMORED, to give an extra degree or two of pitch after takeoff.

spacesailor

Edited January 13, 2022 by spacesailor
Missed word

[JG3]

On 11/01/2022 at 9:31 PM, APenNameAndThatA said:

I noticed you had a testimonial about VG’s and a Foxbat. IIRC, the factory tried VG’s but ditched them because they messed up the stall characteristics. Thoughts? 

The results quoted in the testimonial by the Foxbat owner at https://www.stolspeed.com/a22-fox-bat are pretty much what I would predict for that wing. If the factory got bad stall effects then what did they do wrong in the installation to generate that effect? Most likely placing the VGs too far back on the airfoil.... Also it's typical for manufacturers to not want to recognize that such simple mods can improve their products.