Pitch is measured...

[chunk t]

I know what pitch is, I have a pitch gauge I've used. But I know I'm not doing it correctly

here's what I do -

1. I begin by locating 65% of the length of the trailing edge of a blade and make that my referance point to begin from.

2. As I take pitch measurements, working my way toward the front of the prop, I don't change my distance from the hub. (Each measurement is at 65% relative to the trailing edge.)

3. Obviously by some point (4th or 5th measurement) my readings are nolonger being taken in the mid-section of the blade but at the edge; and I never get a reading on the tongue.

Can someone tell me the correct way to measure pitch on a blade.

chunk t

 

[RodneyPierce]

I know what pitch is, I have a pitch gauge I've used. But I know I'm not doing it correctly

here's what I do -

1. I begin by locating 65% of the length of the trailing edge of a blade and make that my referance point to begin from.

2. As I take pitch measurements, working my way toward the front of the prop, I don't change my distance from the hub. (Each measurement is at 65% relative to the trailing edge.)

3. Obviously by some point (4th or 5th measurement) my readings are nolonger being taken in the mid-section of the blade but at the edge; and I never get a reading on the tongue.

Can someone tell me the correct way to measure pitch on a blade.

chunk t

I would also like to know this! Thanks guys

 

[Dan_Cousin]

Since no one else answered, I'd throw in a penny or two.

The 65% out is for measuring pitch at the trailing edge only. The thought is that this is where the prop is doing most of the work against the water. As you move forward on the prop towards the tongue you lose blade as you have noticed.

The natural solution is the reduce the pointer location from the 65% to a smaller % so the pointer hits the lobe.

It may be to my disadvantage but I don't profile the props much passed the trailing edge and a quicl measurement of the tongue to get a estimate of pitch progression. You can look at a X400 series prop and a 1400 series prop and see that the pitch progression is much higher in the X series props than the 1400 series. I have seen gains by flattening the progression on rigger props.

 

[Jim Allen]

I know what pitch is, I have a pitch gauge I've used. But I know I'm not doing it correctly

here's what I do -

1. I begin by locating 65% of the length of the trailing edge of a blade and make that my referance point to begin from.

2. As I take pitch measurements, working my way toward the front of the prop, I don't change my distance from the hub. (Each measurement is at 65% relative to the trailing edge.)

3. Obviously by some point (4th or 5th measurement) my readings are nolonger being taken in the mid-section of the blade but at the edge; and I never get a reading on the tongue.

Can someone tell me the correct way to measure pitch on a blade.

chunk t

Chunk T,

I'm not excatly sure what is meant by "the tongue". With that in mind, whatever device is used to measure the pitch should be capable of measuring the entire blade surface from leading edge to trailing edge & at any distance from the hub. This device should measure the pitch directly, without any unnecessary calculations, that may cause errors. Keep in mind that the propeller blades used by most model boaters are of the progressive pitch type & not of the constant pitch type used by tether boaters such as Ed Kalfus many years ago. Progressive pitch blades or blades with "camber", start with a low pitch at the leading edge which progressively increases to the trailing edge. The pitch number assigned to this type of blade is the average pitch over the entire blade. To accurately measure progressive pitch amounts when comparing two or more blades requires that some type of dial indicator should be mounted to the pitch measuring device.

It should be notied that for any desired pitch , there is only one true helical pitch to be found at any desired distance from the hub. Since the root of our blades are permantly fastened to the propeller hub, it is impossible to make more than one true helicial pitch propeller from any one casting.

Jim

 

[chunk t]

Jim,

Tongue - The lobe at the front of the blade; like on a stock X440 for example.

chunk t

 

[Jim Allen]

Jim,

Tongue - The lobe at the front of the blade; like on a stock X440 for example.

chunk t

Okay, I understand. The pitch gage must be able to measure the whole blade surface, at any radius. The Kalfus type gage will do this, even on a blade like the 1667.