Hi, Henry. I think your analysis may be correct. The region where the "ratio" goes down would appear to be where drag is increasing. Once you get past these speeds, the "slippage" may be decreasing. Of course, as you have observed, fuel economy will still decrease as RPM increase, simply due to the increasing amount of fuel being delivered for combustion. Best regards, D C "Mac" Macdonald m/v Another Adventure (1995 Carver 355 ACMY) Grand Lake - Oklahoma over this ----Original Message Follows---- From: HClews@aol.com Reply-To: Power Catamaran List <power-catamaran@lists.samurai.com> To: power-catamaran@lists.samurai.com Subject: [PCW] Sno' Dog performance Date: Wed, 2 Aug 2006 11:43:29 EDT Mac, I too, found your table interesting. Seems to me, this ratio gives an indication of how much the propeller is "slipping". In other words, if there were a direct coupling, as in a car for example, this ratio would remain constant (at least in a given gear). The fact that it varies shows the amount of slippage which, I assume, is an indication of "how hard the prop is working". Not very scientific, but seems intuitively correct to me. Henry aboard Sno' Dog In a message dated 8/2/2006 6:48:43 A.M. Eastern Daylight Time, k2gkk@hotmail.com writes: Hi, Bob. I have no idea as to why the performance of Henry Clew's PDQ 34 seems to be so linear. I am just mathematically inclined and I noticed an apparent linearity. I just used a calculator to check out the extent of linearity and decided to share it with the group. I would say that the linearity indicates a happy marriage of design elements, whether intentional or accidental. In any event, I would say that the linearity in 'Sno Dog's performance is highly desirable. Mac in Oklahoma City _______________________________________________ Power-Catamaran Mailing List