HEY I am merely the messenger. That's what the leading prop rebuilder in
the US told me 15 years ago. I have no reason to doubt him.

--
Steve Barker

for the spam bots:






"trainfan1" wrote in message
et...
Steve Barker wrote:
The reason for the step-down recommendation is because the aluminum
flexes

Prove it.

Rob

and looses some pitch. Stainless does not.

It's not MY theory, and it's not theory. thanks for the input. I remember
now why I left this group 3 years ago.

--
Steve Barker

for the spam bots:






"Josh Assing" wrote in message
...
On Sat, 9 Jun 2007 07:31:36 -0500, "Steve Barker"

wrote:

The reason for the step-down recommendation is because the aluminum flexes
and looses some pitch. Stainless does not.


flexes - I think that's generally accepted; but flexes to the point of
loosing
2" of pitch? I find that hard to believe.

On this theory; I'm giong to be way under propped as I had a SS 19 and I
went to
an aluminum 17; so on your theory; this will be like a 15 pitch SS....

Steve Barker wrote:
HEY I am merely the messenger. That's what the leading prop rebuilder in
the US told me 15 years ago. I have no reason to doubt him.


It's an old wives's tale.

Try to duplicate your aluminum prop "flexing" in your shop and report
back with the results.

AND, there is always a prop rebuilder better than your guy. Or my guy.
"Leading prop rebuilder" is a pretty brash & open-ended statement.

Rob

Steve Barker wrote:
It's not MY theory, and it's not theory. thanks for the input. I remember
now why I left this group 3 years ago.


Steve, it's not even not theory.

You're disseminating false information, that's all.

Rob

oh really? well take it or leave it then. why would a person put out false
information if they didn't work for the government?


--
Steve Barker

for the spam bots:






"trainfan1" wrote in message
...
Steve Barker wrote:
It's not MY theory, and it's not theory. thanks for the input. I
remember now why I left this group 3 years ago.


Steve, it's not even not theory.

You're disseminating false information, that's all.

Rob

well he serves just about the entire Midwest. I rekon that says something
for his work.

--
Steve Barker

for the spam bots:






"trainfan1" wrote in message
...
Steve Barker wrote:
HEY I am merely the messenger. That's what the leading prop rebuilder in
the US told me 15 years ago. I have no reason to doubt him.


It's an old wives's tale.

Try to duplicate your aluminum prop "flexing" in your shop and report back
with the results.

AND, there is always a prop rebuilder better than your guy. Or my guy.
"Leading prop rebuilder" is a pretty brash & open-ended statement.

Rob

On Sat, 9 Jun 2007 20:25:03 -0500, "Steve Barker"
wrote:

It's not MY theory, and it's not theory. thanks for the input. I remember
now why I left this group 3 years ago.

Dang you take things way too personally -- you're the one that brought up that
if flexes that much.

sorry to have gotten your panties in a bunch

"Steve Barker" wrote in message
...
HEY I am merely the messenger. That's what the leading prop rebuilder in
the US told me 15 years ago. I have no reason to doubt him.

--
Steve Barker

for the spam bots:






"trainfan1" wrote in message
et...
Steve Barker wrote:
The reason for the step-down recommendation is because the aluminum
flexes

Prove it.

Rob

and looses some pitch. Stainless does not.




I doubt everything anybody tells me until I prove it to myself. I can't
believe you just believe what people tell you!

ps: Based on that, cavitation and boiling won't happen as much if you use a
stainless steel prop either..... well, that's a bad example cause its partly
true since those issues are caused by bent props, nicks etc.

On Sat, 9 Jun 2007 22:08:13 -0500, "Steve Barker"
wrote:

well he serves just about the entire Midwest. I rekon that says something
for his work.

I saw a bunch of high speed film one time of different types of props
and the engineering professor's film illustrated that they don't
"flex" as much as "vibrate". The more tuning the props went through
(like for roundness, blade weight and shape, leading edge rounding
[you'd be surprised at what that does to a marine prop]), the less the
vibration.

I asked several prop machinists including the guy over at Ocean State
who does a lot of prop work in New England (including big wheels for
cruisers/fishing trawlers, etc.) - they all pretty much said the same
thing - not enough to matter in the sense that a aluminum prop warps
enough under load to change pitch.

The consensus seems to be that the real difference is weight, shape
and more material related issues - stainless props are more uniform
and balanced than aluminum, they are tougher and less prone to nicks
and gouges from minor debris and, in general, don't degrade in salt
water as fast as aluminum.

For fresh water use, there really isn't much of a difference besides
looks.

As to thre blade/four blade - I've noticed a heck of a difference
between three and four blade props of the same size and pitch. I'm
firmly in the four blade camp.

Gene Kearns wrote:
On Sat, 09 Jun 2007 14:48:33 -0400, trainfan1 penned the following
well considered thoughts to the readers of rec.boats:

Steve Barker wrote:
The reason for the step-down recommendation is because the aluminum flexes
Prove it.

Both do, but aluminum will bend up to about 4 times as much.....

Check the values for "modulus of elasticity:"

http://www.engineersedge.com/manufac...ous_metals.htm
http://www.engineersedge.com/manufac...ous_metals.htm

The chart you are referencing gives (-------), or -0- for shear modulus
of elasticity on cast aluminum alloys until brass is introduced. There
is some tension, of course(as in an application as fastening hardware).

Aluminum alloy props are very rigid & brittle as the chart shows.

Rob


and looses some pitch. Stainless does not.