I don't see many cats out of the water as there aren't many in the PNW. I can see your point relating to hull draft
and position of the prop and rudder
, although your hulls are much more narrow than a multihull
there are two of them and two rudders, props etc. Would be a very intricate calculation for parasitic drag indeed.
"I think this entire line of conversation might be called a red herring. We are talking propeller drag here, not hull design."
I think you're incorrect in that assumption. You believe the effect of the spinning vs. fixed propeller is limited to itself where others are considering the possability of downstream effects bassed on what previous designers have stated.
"Short of performing one of the above, there really doesn't seem to any point in telling us that all these tests are flat wrong and your opinion is correct, is there?
Or am I missing something?"
You are missing something. No one is disputing the results of MainSail
, or anyone elses functional test. They clearly show that a free wheeling prop in our pitch
range has less drag than when fixed. That, for all practical purposes can taken as fact. What a small group of us are trying to discover is A) Why have naval architects in the past stated that it will still slow the boat, and B) Is there any validity to their claim. Members of this forum have given testimonials, with emphisis, that thier boats are slower when the prop is not alowed to free wheel
, and with no reason to doubt them, one would have to accept that A and B are not conlcusive or all inclusive. There could be multiple reasons for this, either their data was far more applicable to earlier hull shapes fitting the raceing trends and rules in that time period, or, they were simply wrong for what ever reasons, but since most of these designers are no longer around, getting that information from the horses mouth would be difficult at best.
"It's only those reciting the old wives tales that seem to disagree."
"Or, just sail your boat with fixed props and then freewheel them and come on back here and let us know what you've discovered about your boat."
Did just that last Saturday. Wind
was 15 to 20 Knts. and a little gusty. We had choppy conditions ranging from 1 to 3 ft as we were going to windward. I only had GPS
to give boat speed over ground, which was not a stable means for indicating speed. Readings were never smooth enough to be reliable for any length of time so my result are far from conclusive on any side of the argument. Even averaging the speed over time was not stable enough to give creedance to fixed or free wheeling. On a beam reach, we were hitting 7.5 knts. intermittently regardless of prop state, but that's so close to hull speed
that the induced drag of wave making resistance far overshodows the small difference the prop would make given the insensitive speed indication and the abundance of power from the sails
. Next time I'm out and conditions are more conducive to accurate data I will log some numbers and post again. I just want to know the whole story.