through hub / over hub

[Foolish]

apart from the obvious can someone explain the difference between an over hub cleaver and a through hub one ?

[Renegade]

Over hub cleavers are designed to run with the exhaust gases venting the prop for getting on to the plane. the gases help the prop to slip.
I am not 100% on this bit but once up on the plane i am led to believe that over hub props are designed to run higher and more blade area breaks the surface (surface piercing props). this is how the slip is given when planing.

I may be wrong and im sure i will be corrected.

[motorvator]

As is always the case what was the difference 30 years ago to what the difference is now is not quite the same due to advancements in prop design.

Well, let's see: First the earth cooled. And, then the dinosaurs came, but they got too big and fat, so they all died, and they turned into oil. And, then the Arabs came and they bought Mercedes Benzes. And, Prince Charles started wearing all of Lady Di's clothes. I couldn't believe it, he took her best summer dress out of the closet, and put it on, and went to town.

As I remember things, initially solid hub were used where there was no exhaust through hub as they present the most effective blade area. then someone found you could use a higher pitch by surface piercing, the bottom of prop being the most effective.

Then they started using them on through hub exhaust which again showed that the exhaust gasses could be used to allow a high pitch prop to release and rev.

Then some bright spark took a through hub prop and drilled holes in the hub to get the same effect.

Within all of this advancements were made in design of cavitation rings, anti vent etc which changed the charateristics of props again.

And of course because the enquiring human brain is what it is, through all of this development people would put a vented prop on a non through hub exhaust and vice versa just to see what happened.

It's probably best just to accept they are different ok.

You'll get far more enjoyment in investigating whether the motive effect of the prop comes from pulling or pushing, or easier still, whether god really exists

[Mrs Motivator]

What about when you wear my clothes then!! I have seen you many a time going through the panty draw.

There is a nice article by Jimboat on propellors that expalins all the theory it was a free download but that might have changed. a through hub will also have the effect of extending the effective length of the gear case giving a reduce risk of blowout & improved handling but it's all trial and error as to what suits best. Oh kerry those thongs dont suit love as I said trial & error as to what suits best there are some bin liners in the cupboard xxx

[grandmas denture]

Originally Posted by motorvator

And, then the Arabs came and they bought Mercedes Benzes.

... at first they bought cowleys ford

[Foolish]

Originally Posted by motorvator

As is always the case what was the difference 30 years ago to what the difference is now is not quite the same due to advancements in prop design.

Well, let's see: First the earth cooled. And, then the dinosaurs came, but they got too big and fat, so they all died, and they turned into oil. And, then the Arabs came and they bought Mercedes Benzes. And, Prince Charles started wearing all of Lady Di's clothes. I couldn't believe it, he took her best summer dress out of the closet, and put it on, and went to town.

As I remember things, initially solid hub were used where there was no exhaust through hub as they present the most effective blade area. then someone found you could use a higher pitch by surface piercing, the bottom of prop being the most effective.

Then they started using them on through hub exhaust which again showed that the exhaust gasses could be used to allow a high pitch prop to release and rev.

Then some bright spark took a through hub prop and drilled holes in the hub to get the same effect.

Within all of this advancements were made in design of cavitation rings, anti vent etc which changed the charateristics of props again.

And of course because the enquiring human brain is what it is, through all of this development people would put a vented prop on a non through hub exhaust and vice versa just to see what happened.

It's probably best just to accept they are different ok.

You'll get far more enjoyment in investigating whether the motive effect of the prop comes from pulling or pushing, or easier still, whether god really exists

So glad i asked all as clear as mud now

[motorvator]

Our job here is done

[Renegade]

Props are not know as the dark art for nothing!

[stormin177]

Originally Posted by motorvator

As is always the case what was the difference 30 years ago to what the difference is now is not quite the same due to advancements in prop design.

Well, let's see: First the earth cooled. And, then the dinosaurs came, but they got too big and fat, so they all died, and they turned into oil. And, then the Arabs came and they bought Mercedes Benzes. And, Prince Charles started wearing all of Lady Di's clothes. I couldn't believe it, he took her best summer dress out of the closet, and put it on, and went to town.

As I remember things, initially solid hub were used where there was no exhaust through hub as they present the most effective blade area. then someone found you could use a higher pitch by surface piercing, the bottom of prop being the most effective.

Then they started using them on through hub exhaust which again showed that the exhaust gasses could be used to allow a high pitch prop to release and rev.

Then some bright spark took a through hub prop and drilled holes in the hub to get the same effect.

Within all of this advancements were made in design of cavitation rings, anti vent etc which changed the charateristics of props again.

And of course because the enquiring human brain is what it is, through all of this development people would put a vented prop on a non through hub exhaust and vice versa just to see what happened.

It's probably best just to accept they are different ok.

You'll get far more enjoyment in investigating whether the motive effect of the prop comes from pulling or pushing, or easier still, whether god really exists

Very good but you forgot the bit about Cleaver props are designed to lift the stern of the boat as well, that's why they work well on a twin with one counter rotation underwater unit