Calypso's headsails were also cut for a furler with the higher foot, now about 18" off the deck.
We still get a significant "speed bubble" in the main at the mid to upper wind range for the light and heavy #1s. The bubble shows up 6' to 25' (off the deck) on the mainsail. From my miss-spent youth crewing with serious race programs I expect there to be an advantage to the deck sweeper type headsails, more so for the early IOR type sail plans with big fore triangles and smaller mainsails. The engineers may reference something about an end plate effect. Over the last 10 years of club racing Calypso with roller furling headsails we see a significant decrease in performance at the low end of the wind range, especially in acceleration. Side by side with another C&C 43 that had newer, non-furling headsails Calypso was left in the dust as the wind built from calm to 5 knots. Once the TWS was above 7 knots the speed difference was much less but the newer sails still pointed higher. After reading about your +6 per mile for the roller furler I need to take a close look at the PHRF-NW book and re-file Calypso's data. We are still using the old IMS/IOR type measurements. Martin Calypso 1971 C&C 43 Seattle -----Original Message----- From: CnC-List [mailto:cnc-list-boun...@cnc-list.com] On Behalf Of Dennis C. via CnC-List Sent: Wednesday, May 07, 2014 5:51 AM To: cnc-list@cnc-list.com Subject: Stus-List Technical sail discussion I recently re-filed my PHRF certificate to get +6 seconds for a roller furler. Subsequently, I just had the luff my Mylar/Kevlar 155 cut down to fit on the furler. My sail maker cut a bunch off the foot. I was chatting about losing the sail area with one of the really good sailors in the club. He said it may actually be a good thing that the foot is higher off the deck. He said with the older narrow IOR designs, deck sweeper genoas may cause the slot to be less efficient. Might increase the bubble in the main. In my simplistic mind I kinda see where he's coming from. The slot gets restricted at the deck by the cabin. The lower part of the air flow would get pushed upward into the bottom of the main. A higher foot allows some flow to escape and keep the air flow lines smooth in the lower slot. Does this make sense? Dennis C. Touché 35-1 #83 MandevilleLA Sent from my iPhone _______________________________________________ This List is provided by the C&C Photo Album http://www.cncphotoalbum.com CnC-List@cnc-list.com _______________________________________________ This List is provided by the C&C Photo Album http://www.cncphotoalbum.com CnC-List@cnc-list.com
