[Andy b]

There's a lot of good talk over your side of the pond about Michigan wheel apollo props.
so I thought i'd better give one a spin....

hopefully the weather will hold for this weekend.

I'l report back on my findings

[ColoradoDiablo]

Ahh , your gonna hate it Andy!
What pitch did you end up getting?

[mikeyt]

I have that prop in a 4 blade - 20" pitch configuration and like it. The 3 blade version might actually be the very worst performing prop in the world.... just sayin'

[Andy b]

I wanted a prop for when I've got a loaded boat.

The 22' Viper (4800rpm/53mph) I spin when i'm out with just me or me and my kid on board bogs down above 3800 if im loaded (not surprising)
The 19' Lazer II was the worst prop I could have tried.
Bow lift was crazy and it fort against the tabs making the boat almost hop at high speeds! Felt like it might heel/toe stuff at any time.
The steering became vague, almost too the point of non responsive and the boat felt like it had lost grip on the water feeling floaty underneath you!

The 21' Lazer II on the other hand was ok just nothing special!

The 21' Michigan wheel match is a good all round prop on my boat

This Apollo is 14 1/4x19.
I know i'l have to be careful about over revving it but looking at the blades they look like they will have plenty of grip, the rake angle is quite shallow, presents a lot of blade to the water.
And it has a nice amount of cupping on the trailing edge for grip.

I don't pull toys or boards so I don't feel the need for a 4 blader but maybe if I like how this prop feels I might invest in a nice 20' 4 blader as my general use prop

[Andy b]

10% slip is what i'm getting on the 22' Viper

[gahooligan]

Curiosity gets the best if me. What is prop slip? Is it like lost efficency or something?

[mikeyt]

This info from the Merc Prop Slip calculator site: Slip is the most misunderstood of all propeller terms, probably because it sounds like something undesirable. Slip is not a measure of propeller efficiency. Rather, slip is the difference between actual and theoretical travel resulting from a necessary propeller blade angle of attack. If the blade had no angle of attack, there would be no slip; but, of course, there would be no positive and negative pressure created on the blades and, therefore, there would be no thrust.

I did also read a scientific explanation which involved Newton's laws but it made my head hurt....

[Andy b]

Originally Posted by mikeyt

This info from the Merc Prop Slip calculator site: Slip is the most misunderstood of all propeller terms, probably because it sounds like something undesirable. Slip is not a measure of propeller efficiency. Rather, slip is the difference between actual and theoretical travel resulting from a necessary propeller blade angle of attack. If the blade had no angle of attack, there would be no slip; but, of course, there would be no positive and negative pressure created on the blades and, therefore, there would be no thrust.

I did also read a scientific explanation which involved Newton's laws but it made my head hurt....

Yeah what he said.....lol

Basically water is not a solid and as the prop blade moves through it it does not just cut a path though it but creates high and low pressure either side if the blade.
Without slip the resistance against the blade would be too great and not a lot would happen.
Of course to much slip is also a bad thing.
This is when cavitation/ventilation occurs.

The trick is to get the balance right so that the prop is acting at maximum efficiency.
This is not a fixed number as it varies from one boat/setup too another.....

there are websites that can explain it a lot better than I have, but I hope you get the idea

[rhinoz]

Originally Posted by mikeyt

This info from the Merc Prop Slip calculator site: Slip is the most misunderstood of all propeller terms, probably because it sounds like something undesirable. Slip is not a measure of propeller efficiency. Rather, slip is the difference between actual and theoretical travel resulting from a necessary propeller blade angle of attack. If the blade had no angle of attack, there would be no slip; but, of course, there would be no positive and negative pressure created on the blades and, therefore, there would be no thrust.

I did also read a scientific explanation which involved Newton's laws but it made my head hurt....

Took the words right out of my mouth!!

[Andy b]

How's them numbers then

The BS o-meter was reading 47/50mph pitot (STW)
The GPS was reading 47's (SOG)

I knew it was going to be down on speed, but only by a couple mph
fantastic prop though.... the boat was a joy to drive in what I would describe as moderate condition