stunthanger.com

Electric Stunt => Gettin all AMP'ed up! => Topic started by: Bob Reeves on August 01, 2011, 01:25:10 PM

Title: Reverse pich props pitch measuring?
Post by: Bob Reeves on August 01, 2011, 01:25:10 PM: So how are you guys measuring reverse pitch props, or are you?
One of these days I will have a Saito running backwards with a reverse pitch prop and my pitch gauge no workie HB~>

Neber mind, just found this thread..
http://stunthanger.com/smf/index.php?topic=12669.0
Title: Re: Reverse pich props pitch measuring?
Post by: BillLee on August 01, 2011, 03:31:47 PM: Use a mirror?

Put the prop on the gauge backwards?

;D
Title: Re: Reverse pich props pitch measuring?
Post by: Dave Adamisin on August 01, 2011, 06:14:04 PM: I took the scale off my Prather and scanned it. I brought the image into Paint Shop Pro and mirrored it. I then printed it off on the laser printer, cut it out roughly and rubber cemented it to the back of the scale. Trimmed it to the edges of the scale. Then I bolted the arm through the scale into a nylok nut. Then I bolted the scale back on backwards. The numbers are backward but it's functional.
Title: Re: Reverse pich props pitch measuring?
Post by: Darkstar1 on August 02, 2011, 07:45:03 AM: Dave here's another thread about the Prather gauge
http://stunthanger.com/smf/index.php?topic=15276.msg138793#msg138793
Title: Re: Reverse pich props pitch measuring?
Post by: Dave Adamisin on August 02, 2011, 09:21:01 AM: Quote from: darkstar1 on August 02, 2011, 07:45:03 AM
Dave here's another thread about the Prather gauge
http://stunthanger.com/smf/index.php?topic=15276.msg138793#msg138793

Hmmm.... I need to finish up the job and drill the extra holes..... The next issue is how we address the under-camber/cuff issue. The cuff on the electric props makes accurate pitch measurements problematic. What is the actual angle of attack of a "cuffed" airfoil??
Title: Re: Reverse pich props pitch measuring?
Post by: Darkstar1 on August 02, 2011, 10:21:21 AM: Dave
Did U get my PM about those new props yet? If so I need your Address again.
Title: Re: Reverse pich props pitch measuring?
Post by: Allan Perret on August 02, 2011, 10:26:25 AM: OK, whats a cuff ?
Title: Re: Reverse pich props pitch measuring?
Post by: Dennis Adamisin on August 02, 2011, 03:54:19 PM: Quote from: darkstar1 on August 02, 2011, 10:21:21 AM
Dave
Did U get my PM about those new props yet? If so I need your Address again.

Uhh, Dave didn't get your PM, but I did!
Title: Re: Reverse pich props pitch measuring?
Post by: Dave Adamisin on August 02, 2011, 06:30:28 PM: Quote from: Allan Perret on August 02, 2011, 10:26:25 AM
OK, whats a cuff ?

That roll at the bottom of your pants......... Actually it's the somewhat exagerated undercamber at the first few stations of most of APC's E props. Because of the "curl/cuff" along the trailing edge of the prop, the flat blade of the pitch gauge spans the camber. The airfoil of the prop looks more like a glider wing than the usual flat bottom or hollowed/cambered blade that's becomming more popular on wet systems.
Title: Re: Reverse pich props pitch measuring?
Post by: Allan Perret on August 03, 2011, 08:51:16 AM: If its only on the first few stations should not be an issue as far as measuring pitch.
Title: Re: Reverse pich props pitch measuring?
Post by: Dave Adamisin on August 03, 2011, 10:42:37 AM: Quote from: Allan Perret on August 03, 2011, 08:51:16 AM
If its only on the first few stations should not be an issue as far as measuring pitch.

You are probably right. I have always asked questions when I see things I don't know and understand. The question I have about the exagerated curve in the botttom side of the prop is it's relevence to my data. I was in testing for about 20 years and I know that other people look at what I chose to call data. If I missed something in my method it could influence conclusions based on the numbers. In the real world it is probably not important as long as the prop performs to your liking. In the case of the cuff/deep-camber on the E props, spanning the camber with the flat blade of the pitch gauge has the effect of inflating the pitch number compared to a flat bottom blade. When I don't know an answer I count on someone who knows to become involved. It was a method that worked well in my career in engineering. People usually like to help and share what they know. It keeps this blog rolling nicely......