Props (again)

With or without gears

On what pack?

Terry-

The canonical way to determine the the power absorbtion capacity of a prop at a given radius is to use the expression for the prop geometry factor known as solidity. I'm too lazy to try and write it out using only the ASCII character set, so here is an alternate way that involves less strain on the brain:

Use Barry Hobson's Thrust/HP calculator, which you can download free from

Using the calculator determine the HP at the desired rpm for the baseline 2-blade prop. Then set the # blades to 3, and iterate on the diameter until you get the same figure for power absorbed.

Abel

A typical, and admittedly crude way to do this has been to reduce diameter by one inch as a starting point when going from 2 to 3 blades. More analytical methods as suggested are likely better, but it is a starting point. Thus without further effort my first kick at the cat would be 8-6.

The message from Abel Pranger contains these words:

Hi Abe, cant get that link to happen as it is with Virgin.net and all their setup has changed now they have bought out Blueyonder and rearranged all the websites,

regards, Terry

Just tried this one, it worked:

Abel

The message from Abel Pranger contains these words:

Hi Abel, downloaded OK thanks, will have a play with it a bit later as it is only 1.45 a.m here...............;-) may go get me a nice glass of Scotch (12 year old single malt of course) to help me think...

regards, Terry

Aye, a splendid idea. I may have a wee dram meself.

Abel