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On Mon, 07 Jun 2004 12:33:32 GMT, (Steven Shelikoff) wrote:

snip

My two cents of fooling...

Original post has been:

We have an inboard and, of course, the prop shaft exits the hull at an
angle. I just drove by a similar (but different brand) of boat and it
appears it's prop shaft comes out at less of an angle. My first though it
that a angle that gives a more push forward and less push "up" would be more
efficient. Is that about right??

Unless specific requirement or prototype or testing purpose... the "angle" of the propeller shaft is usually "drawn" by
the boat Designer in compliance with hull shape, engine + transmission + flexible coupling + thrust bearing box + grease
box + personal opinion regarding what is better or what is not.

Many times Marine engines are "marinerized" truck or tractor or car ones.

This means else that original automotive Oil Pan has been replaced with a larger and higher one, so the "centerline" of
engine is a lot higher than automotive one.

To obtain a "straight" line from engine to propeller you "have" to make an "angle",

This angle is depending from overall dimensions of the driveline and how much free space you need aboard.

It has been done by Boat Designer using his acknowledge, choice and interests.

If angle is "too wide" engine becomes "too tilted" and you will have lubricating problems...

if angle is "too horizontal" you waste a lot of payload space...

Angle is depending else from rated propeller Outer Diameter...

So it is depending from Boat design.

The Question If is better a more or a less angle... it is "relative" and it involves personal opinions, like Political
opinion: Each one has its one.

....Submarines have horizontal straight driveline...

....Twin Engine boats have contro-rotating propellers... with any angle...

....Venetian Gondola has a straight side on RH and a curved side on LH... to go straight forward with one single oar...

No heavy or deeply mathematics... only "space" matters...

Hope this may clarify something...

(of course there are "specifically" engineered drivelines, but it is not true regarding cheap or commercial boats...)

This is my opinion, no war flames please.

Regards,

WinXP

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