Hi Don, I had the same question a while back and received the following reply from Ken Abrahams. -----Original Message----- From: Ken Abrahams [mailto:abrahams@structurex.net] Sent: Fri 7/11/2003 7:52 AM To: Randy Graves; For and about MontgomerySailboats Cc: Subject: Re: M_Boats: PHRF Rating for M15? Here is a way to calculate PHRF if no rating is available. From the Portsmouth Tables the following conversion is given: Portsmouth = PHRF/6 +55 This converts to: PHRF = (Portsmouth - 55) X 6 Monty 15 is 108.1 Portsmouth and this converts to 318.6 PHRF. Ken Abrahams Monty 15, Petite Fleur Lake Charles, La ----- Original Message ----- From: Randy Graves <mailto:RandyG@cite.nic.edu> To: For and about Montgomery Sailboats <mailto:montgomery_boats@mailman.xmission.com> Sent: Thursday, July 10, 2003 1:26 PM Subject: M_Boats: PHRF Rating for M15? Can someone tell me the PHRF rating for the M-15? I searched the archives and found suggested numbers for the M-23 and M-17 but none for the M-15. Any help is appreciated! Thank you, Randy Graves M-15 #407 -----Original Message----- From: Ludlow, Don [mailto:LudlowD@BEK.com] Sent: Mon 9/22/2003 5:32 AM To: 'montgomery_boats@mailman.xmission.com' Cc: Subject: M_Boats: RE: M-15 PHRF Number montgomery_boats Digest, Vol 7, Issue 27 Hi all: I've searched the archives and haven't found a PHRF number for the M-15. I did find some formulas though. The archives list the PHRF number for the M-17 as 295. Since the M-15 hull has about the same lines (scaled down), I thought I could work out a ratio. The rating velocity is given as 3600 / (PHRF + 500) which works out at 4.26 knots for the M-17. The theoretical M-17 hull speed is 1.34 x Sq rt of the LWL (15.8') or 5.33 knots. Thus the PHRF rating speed is 4.26/5.33 or 80% of the hull speed. Applying this to the M-15, I get a hull speed of 4.87S knot based on a LWL of 13.25'. 80% of this gives a PHRF rating speed of 3.90 knots. Backing into the formula above, this gives a PHRF number for the M-15 of 373. Any comments? Don Ludlow M-15 # 620 Sweet Dream Ludlowd@bek.com