How do I convert pitch of a Grim prop?

[Meniscus]

LMAO! I know, I know. I figured I'd get heckled, but I did get some good insight. Thanks everyone.

And for the record, I'm a Rum drinker

[785boats]

Here's my take on it.
If you know the pitch ratio & the diameter you can work out the pitch. It's the diameter multiplied by the pitch ratio.

1) An Octura X440 has a pitch ratio of 1.4 & a diameter of 40mm.
1.4 x 40mm = 56mm pitch.

2) An Octura X640 has a pitch ratio of 1.6 & a diameter of 40mm.
1.6 x 40mm = 74mm pitch.

If you know the pitch & the diameter you can work out the pitch ratio. It's the pitch divided by the diameter.

1) A Grimracer 40 x 52 prop has a diameter of 40mm & a pitch of 52mm.
52mm divided by 40mm = 1.3 pitch ratio.

2) A Grim racer 40 x 57 prop has a diameter of 40mm & a pitch of 57mm.
57mm divided by 40mm = 1.42 pitch ratio.
Does that help?

Maybe someone could answer a question for me.
How do you tell the prop size, pitch or pitch ratio from the Prather ident numbers? They seem to bear no relationship to the actual prop statistics. Or am I missing something here.
Cheers.
Paul

[egneg]

I can't answer how the numbers work for Prather props so I use this chart.

http://www.offshoreelectrics.com/propeller-chart.php

[785boats]

Thanks man.
I thought there'd be a table somewhere.
Much appreciated.
Paul.

[egneg]

I found the information but to correct myself it was meant to quantify prop cupping and not progressive pitch. Even though it is not directly on subject it may help some folks if I can get it to load as it is a PDF file.

I am sorry but It won't let me upload - if you want it send a PM with email addy and I will send it to you.

[Meniscus]

Here's my take on it.
If you know the pitch ratio & the diameter you can work out the pitch. It's the diameter multiplied by the pitch ratio.

1) An Octura X440 has a pitch ratio of 1.4 & a diameter of 40mm.
1.4 x 40mm = 56mm pitch.

2) An Octura X640 has a pitch ratio of 1.6 & a diameter of 40mm.
1.6 x 40mm = 74mm pitch.

If you know the pitch & the diameter you can work out the pitch ratio. It's the pitch divided by the diameter.

1) A Grimracer 40 x 52 prop has a diameter of 40mm & a pitch of 52mm.
52mm divided by 40mm = 1.3 pitch ratio.

2) A Grim racer 40 x 57 prop has a diameter of 40mm & a pitch of 57mm.
57mm divided by 40mm = 1.42 pitch ratio.
Does that help?

Maybe someone could answer a question for me.
How do you tell the prop size, pitch or pitch ratio from the Prather ident numbers? They seem to bear no relationship to the actual prop statistics. Or am I missing something here.
Cheers.
Paul

That makes sense. I just couldn't get my head wrapped around going the other way with the Grim props. LOL