Re: Stus-List Technical sail discussion
Joel and Dennis, If you really want to understand the how of why of sail aerodynamics, I would suggest reading the book the art and science of sails by Tom Whidden. He thoroughly debunks the Bernouli theory as applied to sails. His theory is quite complex but well explained in the book and has nothing to do with pressure diferential of the Bernouli theory, but end plate effect is very important. James S/V Delaney 1976 CC 38 Oriental, NC - Original Message - From: Joel Aronson via CnC-List To: Dennis C. ; cnc-list@cnc-list.com Sent: Wednesday, May 07, 2014 8:59 AM Subject: Re: Stus-List Technical sail discussion Dennis, My limited understanding of aerodynamics is that if the foot is not on the dock then the higher pressure is allowed to leak under the foot to the low pressure side, diminishing lift. That's why they now have tips on airplane wings. If the cabin causes upward deflection, that may be more than offset by maintaining the pressure differential. But either way, you are +6 sec./mile! Joel 35/3 Annapolis On Wed, May 7, 2014 at 8:51 AM, Dennis C. via CnC-List cnc-list@cnc-list.com wrote: 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 sailmaker cut a bunch off the foot. I was chatting about loosing 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 CC Photo Album http://www.cncphotoalbum.com CnC-List@cnc-list.com -- Joel 301 541 8551 -- ___ This List is provided by the CC Photo Album http://www.cncphotoalbum.com CnC-List@cnc-list.com ___ This List is provided by the CC Photo Album http://www.cncphotoalbum.com CnC-List@cnc-list.com
Re: Stus-List Technical sail discussion
The end plate effect is very real. I learned that long ago when windsurfing, if you can setup your sail so you can rake the sail back and the foot touches the board, you add power.. You can feel the acceleration immediately. Especially in winds below 15 knots. As the wind builds above that, everyone starts to achieve hull speed and the nuances of sail theory and fine trim are less critical. This leads me to believe that sails made for light winds should be fuller and deck sweepers and sails made for higher wind areas, should be flatter and high cut. My 2 cents. Chuck Resolute 1990 CC 34R Atlantic City, NJ - Original Message - From: CNC boat owners, cnc-list cnc-list@cnc-list.com To: CNC boat owners, cnc-list cnc-list@cnc-list.com Sent: Thursday, May 8, 2014 5:08:47 PM Subject: Re: Stus-List Technical sail discussion Joel and Dennis, If you really want to understand the how of why of sail aerodynamics, I would suggest reading the book the art and science of sails by Tom Whidden. He thoroughly debunks the Bernouli theory as applied to sails. His theory is quite complex but well explained in the book and has nothing to do with pressure diferential of the Bernouli theory, but end plate effect is very important. James S/V Delaney 1976 CC 38 Oriental, NC - Original Message - From: Joel Aronson via CnC-List To: Dennis C. ; cnc-list@cnc-list.com Sent: Wednesday, May 07, 2014 8:59 AM Subject: Re: Stus-List Technical sail discussion Dennis, My limited understanding of aerodynamics is that if the foot is not on the dock then the higher pressure is allowed to leak under the foot to the low pressure side, diminishing lift. That's why they now have tips on airplane wings. If the cabin causes upward deflection, that may be more than offset by maintaining the pressure differential. But either way, you are +6 sec./mile! Joel 35/3 Annapolis On Wed, May 7, 2014 at 8:51 AM, Dennis C. via CnC-List cnc-list@cnc-list.com wrote: blockquote 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 sailmaker cut a bunch off the foot. I was chatting about loosing 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 CC Photo Album http://www.cncphotoalbum.com CnC-List@cnc-list.com -- Joel 301 541 8551 ___ This List is provided by the CC Photo Album http://www.cncphotoalbum.com CnC-List@cnc-list.com /blockquote ___ This List is provided by the CC Photo Album http://www.cncphotoalbum.com CnC-List@cnc-list.com ___ This List is provided by the CC Photo Album http://www.cncphotoalbum.com CnC-List@cnc-list.com
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 sailmaker cut a bunch off the foot. I was chatting about loosing 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 CC Photo Album http://www.cncphotoalbum.com CnC-List@cnc-list.com
Re: Stus-List Technical sail discussion
Dennis, My limited understanding of aerodynamics is that if the foot is not on the dock then the higher pressure is allowed to leak under the foot to the low pressure side, diminishing lift. That's why they now have tips on airplane wings. If the cabin causes upward deflection, that may be more than offset by maintaining the pressure differential. But either way, you are +6 sec./mile! Joel 35/3 Annapolis On Wed, May 7, 2014 at 8:51 AM, Dennis C. via CnC-List cnc-list@cnc-list.com wrote: 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 sailmaker cut a bunch off the foot. I was chatting about loosing 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 CC Photo Album http://www.cncphotoalbum.com CnC-List@cnc-list.com -- Joel 301 541 8551 ___ This List is provided by the CC Photo Album http://www.cncphotoalbum.com CnC-List@cnc-list.com
Re: Stus-List Technical sail discussion
Dennis: Now if you want another 9 secondsditch the spinnaker pole and declare “no pole” and go straight to your ASYM…Ron C. From: CnC-List [mailto:cnc-list-boun...@cnc-list.com] On Behalf Of Joel Aronson via CnC-List Sent: Wednesday, May 07, 2014 8:59 AM To: Dennis C.; cnc-list@cnc-list.com Subject: Re: Stus-List Technical sail discussion Dennis, My limited understanding of aerodynamics is that if the foot is not on the dock then the higher pressure is allowed to leak under the foot to the low pressure side, diminishing lift. That's why they now have tips on airplane wings. If the cabin causes upward deflection, that may be more than offset by maintaining the pressure differential. But either way, you are +6 sec./mile! Joel 35/3 Annapolis On Wed, May 7, 2014 at 8:51 AM, Dennis C. via CnC-List cnc-list@cnc-list.com mailto:cnc-list@cnc-list.com wrote: 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 sailmaker cut a bunch off the foot. I was chatting about loosing 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 CC Photo Album http://www.cncphotoalbum.com CnC-List@cnc-list.com mailto:CnC-List@cnc-list.com -- Joel 301 541 8551 ___ This List is provided by the CC Photo Album http://www.cncphotoalbum.com CnC-List@cnc-list.com
Re: Stus-List Technical sail discussion
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 CC 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 CC 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 CC Photo Album http://www.cncphotoalbum.com CnC-List@cnc-list.com ___ This List is provided by the CC Photo Album http://www.cncphotoalbum.com CnC-List@cnc-list.com
Re: Stus-List Technical sail discussion
Martin, end plate effect is what I was thinking about. The deck is the end plate for a sweeper. Joel On Wed, May 7, 2014 at 1:32 PM, Martin DeYoung via CnC-List cnc-list@cnc-list.com wrote: 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 CC 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 CC 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 CC Photo Album http://www.cncphotoalbum.com CnC-List@cnc-list.com ___ This List is provided by the CC Photo Album http://www.cncphotoalbum.com CnC-List@cnc-list.com -- Joel 301 541 8551 ___ This List is provided by the CC Photo Album http://www.cncphotoalbum.com CnC-List@cnc-list.com
Re: Stus-List Technical sail discussion
I don't know about your PHRF area, but Chesapeake requires that the furler drum is above deck AND you have the UV patch (heavy cloth) on both the foot and leach of the sail. Then you get the six seconds. Gary - Original Message - From: Martin DeYoung via CnC-List cnc-list@cnc-list.com To: Dennis C. capt...@gmail.com; cnc-list@cnc-list.com Sent: Wednesday, May 07, 2014 1:32 PM Subject: Re: Stus-List Technical sail discussion 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 CC 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 CC 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 CC Photo Album http://www.cncphotoalbum.com CnC-List@cnc-list.com ___ This List is provided by the CC Photo Album http://www.cncphotoalbum.com CnC-List@cnc-list.com ___ This List is provided by the CC Photo Album http://www.cncphotoalbum.com CnC-List@cnc-list.com
Re: Stus-List Technical sail discussion
Thought a furler was 3 seconds, not 6? Have to check our PHRF site. Less area but the higher foot makes it easier to skirt over the lifelines, too. When ours gets caught, I have the crew tension the sheet and I tap the lifelines from the wheel and the sail rolls right inside, and they fine tune accordingly. Chuck Resolute 1990 CC 34R Atlantic City, NJ - Original Message - From: CNC boat owners, cnc-list cnc-list@cnc-list.com To: CNC boat owners, cnc-list cnc-list@cnc-list.com Sent: Wednesday, May 7, 2014 8:51:27 AM 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 sailmaker cut a bunch off the foot. I was chatting about loosing 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 CC Photo Album http://www.cncphotoalbum.com CnC-List@cnc-list.com ___ This List is provided by the CC Photo Album http://www.cncphotoalbum.com CnC-List@cnc-list.com
Re: Stus-List Technical sail discussion
Gary, You are right about the above deck furler. I'm in the Gulf Yachting Association (gya.org) Here's the rule: The PHRF committee may allow +6 seconds per mile in rating for a roller furling headsail and +12 seconds for an optional IN-MAST roller furling mainsail. Boats must have a SA/DSPL less than 20.01 and an inboard or saildrive (non-retractable) engine to be eligible for credit(s). The attached form must be submitted to receive this credit. 1. Uses a working roller furling headsail attached to an above deck mounted roller furling system. Roller furling headsails must be tacked above the drum and may be interchangeable with other working roller furling headsails while racing. Possible +6 seconds! 2. Uses an optional working Roller Furling in-mast mainsail, which may have no more than 5 vertical battens and that the roach of the sail does not extend past the backstay (or a line from the top of the mast to the deck edge of the transom if a back stay is not standard on the boat) and is furled vertically by rolling rather than flaking. Possible +12 seconds! 3. For the Roller Furling Headsail credit the boat must have a sail area/displacement of less than 20.01. This value (SA/DSPL) is based on the following formula: SA/DSPL = SA / (DSPL/64)^2/3. Sail area and displacement values will be based on the standard dimensions published for the boat class by US Sailing ( http://offshore.ussailing.org/phrf) “Critical dimensions” using 100% of the foretriangle and 100% mainsail and mizzen sail area. 4. Each boat has to apply for this credit individually, and the committee reserves the right to refuse the credit(s) to boats that they deem to be more racing than cruising. (Refer to GYA-PHRF.com for a copy of the form) 5. Will notify the PHRF Committee of any changes made to the above items. Touche's SA/DSPL is 20.0 Dennis C. Touche' 35-1 #83 Mandeville, LA On Wed, May 7, 2014 at 2:30 PM, Gary Nylander via CnC-List cnc-list@cnc-list.com wrote: I don't know about your PHRF area, but Chesapeake requires that the furler drum is above deck AND you have the UV patch (heavy cloth) on both the foot and leach of the sail. Then you get the six seconds. Gary - Original Message - From: Martin DeYoung via CnC-List cnc-list@cnc-list.com To: Dennis C. capt...@gmail.com; cnc-list@cnc-list.com Sent: Wednesday, May 07, 2014 1:32 PM Subject: Re: Stus-List Technical sail discussion 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 CC 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 CC 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 CC Photo Album http://www.cncphotoalbum.com CnC-List@cnc-list.com
