Polished -vs- Satin Finish: My Results...
 

Darin(Houston Propellor Servivce) and everyone, It was a beautiful weekend to test and the results are in!

A satin-finished prop, in this case, is FASTER.

History:
The Contest - http://pub47.ezboard.com/fteambajama...icID=122.topic

The First Test - http://pub47.ezboard.com/fteambajama...icID=137.topic

Pictures after Finishing - http://offshoreonly.com/forums/showt...threadid=48726


The test conditions for my original factory Mirage Plus 23P were:
Temperature: 82*F
Humidity: 80% Relative
Pressure: 29.90 In HG
Winds: Calm, 5-10knots
Tides: High, little movement
Load: 1/2 tank Fuel, 2 people
WOT MAX Speed: 65.4mph


The conditions yesterday with the satin-finished prop were:
Temperature: 84*F
Humidity: 80% Relative
Pressure: 30.00 In HG
Winds: Calm, 5-10knots
Tides: Incoming, Almost High, moderate movement
Load: 1/2 tank Fuel, The Same 2 people
WOT MAX Speed: 66.1mph


This time, I also made two runs(similar to the first time) to get an average to cancel out any wind or tide effects. The only difference is that I ran East-to-West and vice-versa because the tides were incoming(running north) and the wind was southerly(heading north).

I felt that with those two factors, the speeds would be innacurate if I ran north or south.

In any event, the speeds were identical this time, going both directions.

I would conclude, based on my speeds, slightly higher temps and an identical load, that a satin-finished prop is faster.

i have been down this road many times...THE ONLY way to tell is actually change the finish of the same exact prop and conduct all testing on a AC dynamometer in controlled environment using exactly all the same parameters...

i have to ask...same prop or different props??
were they at the very least computer scanned and documented?

due to creating stress-risers with a satin finish...i personally recommend polishing....but hey what do i know

Joe,
It was the same prop. It was run stock first, refinished and then run again.

I realize, It's not the absolute most scientific test, but it is what I was able to record.

As for the specifics on what was precisely done to the prop, you'd have to ask Darin. From what I can tell, it's completely unaltered except for refinishing.

I realize that 0.7 mph can be attirbuted to many different things, but the conditions were pretty darn close.

As far as stress risers, a mild stainless like that with which props are made from, the fatigue stress cracking isn't as severe as other more brittle metals. But, you've definately got a valid point.

good reply BD!...but bravos and hydos use very a different SS material....you would be very surprised to see how many blades come apart...granted no so much on 23's as say 30's and above....

keep up the good work!

good Job all!!!!!!!!!!Prop was satin finished only removing the polished finish using a pb-80 grit compound on a sisal cotton wheel! a couple of passes and done!!!!!!!!! the edges of the prop were not touched nor anything other than the finish/good question Joey.Thanks again Baja Daze EXCELLENT JOB!!!!!!!!!!!!!!!!!!
Darin

Thanks guys. It was fun and a neat learning experience. :)

I tested mine last weekend as well, but I'll start another thread so I can post whore..:D :D

Nice job Nick!!!

:D:D

Saw your post.

Good to see similar results on two different boats with two different style props.