Go figure.... 11x4 and 11x4 are not the same.

[Paul Taylor]

OK here is one for you…..

Went flying with Arlan this afternoon to blow the dust off my planes before our fun fly tomorrow. I put up the Twister and it seemed a little fast, so we started swapping props.
Arlan had a Zinger that he had re-pitched. It was a 12 something and he cut it and pitched it to 11x4. We put it on the Twister and it was the magic prop. Very nice flight.
At the end of my flight he said he had to go pickup his son, and as he got in the truck I ran out of fuel. The prop stopped at the bottom, and I cracked the prop on landing.
Dang!
I went to my props and pulled out an stock 11x4 Zinger. I did not touch the needle, pulled out my stooge and launched. Very sad flight. The bladeds on Arlan’s cut down prop were a little wider. Sure hate I popped the prop.
The FF 10.5x4.5 just would not pull my porker of a Twister. Spent the rest of the afternoon in search of a prop.

We will see how it goes tomorrow.
 

[Alan Hahn]

Paul,
I would simply take a look at the broken re-pitched Zinger and your Zinger.
#1: Is your Zinger stock? If so, look at those blunt leading and trailing edges. I bet a lot of engine horsepower is wasted right there. I bet that "repitched" Zinger at least had nice and smooth edges.
#2: As you mentioned, the repitched Zinger originally was a 12 inch prop. There is a lot more blade area on a 12" than a 11", even when you cut the 12" to an 11". Repitching---you didn't mention which way the pitching went, I guess the pitching went up to ~4.5". I wonder what your stock Zinger real pitch (not the stamped number!) was.
I have spent some time playing with the Zinger 11 to 12 inch prop "kit". You should try too. It is a cheap way to spend a non-flying afternoon!

[Jim Thomerson]

Irritating story.  I took a Zinger 11 x 5 and made a beautiful prop out of it, undercambered, thinned, better airfoil, etc.  Tried it out and was well pleased with the results.  Now for the irritating part.  I then tried an unmodified Zinger 11 x 5 "prop kit".  It preformed just as well as my wonder prop. Bah, Humbug!

[Phil Spillman]

Most recently, about 1.5 months ago, I acquired a new MAS Series 3 11 X 4 prop to try on my ARF Nobler with B-40 for power. Prior to this I had been happy with the TF Power Point 11 X 4 props on this set up. Once I added the Sr.3 MAS I experienced a quantum leap forward in performance! I am now usnig this prop on this set up exclusively! I do clean off the flash, balance if necessary and sand smooth if needed. Really makes my engine happy!  Phil Spillman

[Chris Brainard]

The best tool I have found for thinning wood props is a cabinet scraper. Takes a little effort to learn to sharpen one, but once you do and learn to use it, it is extremely easy to thin a prop and maintain control of how much material is removed. Normally, the first thing I do is check to make sure the prop blades are equal length, followed by balancing. Next, check pitch. If adjustment to pitch is needed I shade the back of the blade with a pencil so that I can monitor progress. This is where the cabinet scraper really comes in handy. I can count how many "strokes" I shave off each blade with the cabinet scraper. Typically, I'll count 20 strokes off each blade and then check for balance. Very rarely will the prop need any additional shaving to be in balance. With a good sharp scraper it takes about 15 - 20 minutes to thin, repitch and balance a prop. The scraper also very quickly removes the factory finish and can reshape the leading edge. After scraping, 320 grit followed by 400 grit sandpaper prepares the surface for a new finish. Note that this works on wood props. APC and fiberglass or carbon fiber props will quickly dull a cabinet scraper.
Chris