Prop talk

[Whitebear]

I keep hearing folks talking about prop pitch in degrees. I'm really fascinated by this apparent shift in terminology. I'm really curious, Have manufacturers have given up the SAE standard of measuring pitch in inches?

When I was propping my old DD Buicks I ordered a 70X44 which meant it was a 70 inch long blade and it would move forward in a non slip medium (theoretical) 44 inches.

I keep envisioning that when ya pitch one in degrees ya gotta make darned sure the hub is perfectly vertical or your clingometer you use to measure the degrees pitch with will give an incorrect reading.

Am I all wet here or has the technology and industry make a shift in standards?

Scotty

 

[jdotson]

I speak of degrees because when I set my composite blades, I have to use an angle finder and check each tip at a common location to be sure they are all set properly. I don't always have the hub perfectly level as long as I set the tips on the same degree at a single check point. It's not as confusing as this just sounded!! :shock:

 

[Whitebear]

I understand perfectly what you just said. Your just making sure they are all set the same relative to each other. Your not looking for an absolute spec for comparison to another boat.

Thats valid and nothing wrong with that. Im just curious since nearly everyone is talking degrees now days at least in discussion here Just seemed like there was confusion, maybe mine at that

Scotty

 

[Anonymous]

The actual "pitch" is built into the blade at the factory, but the blades can be adjusted within a certain range and the easiest way to compare that is in degrees, measured at the tips.

It would be difficult for the enthusiast to measure the change in "pitch in inches" when adjusting their prop, but with an angle finder, it's a snap to set the degrees the same.

 

[cntry141iq]

WhiteBear: I refer to degrees because on my whirlwind props they have degree marks etched into the hub that you line up the seam in the prop with. They have them marked in increments of one(1) I don't know if it is truly dgrees or just their terms. I have always in the past referred to it as inches of twist meaning like you said .. how far will the prop move or the air from the prop move in one rotation in a perfect world. There does exist somewhere a chart that converts one into the other .. I think stan is familiar with it.

 

[Whitebear]

The relative indications of a clingometer make sense to me as was stated above. But ya cant compare from one boat to another unless both have an absolute vertical hub because ones 46 degrees may be anothers 40 degrees if they dont have a common zero reference.

I see whats going on now, its the adjustable pitch props that have it going this way as a shortcut. And its completely valid for comparisons even as long as there is a common reference. Otherwise its only valid between blades on the same prop.

Im glad I started this thread, I see whats going on now.

Scotty

 

[Anonymous]

Bingo Scotty