Sharkskin anyone? more on Bottoms

OK, If laminar flow is so good why to sharks have sand paper skin? And why do swimmers go faster in sharkskin simulated suits? I've heard the sharkskin holds the boundary layer of water to the hull so that you just have water to water friction which is less than water to hull surface friction...or something like that. Jerry. BTW I can see that certain Mexican or Hungarian slime would actually like hot pepper in their bottom paint. --- On Fri, 2/27/09, glen thorpe <gl… [at] yahoo.com> wrote: From: glen thorpe <gl… [at] yahoo.com> Subject: Re: [Cal_Boats] Re:Getting a smoothe bah-um, pepper in the paint, was which Bottom Pain To: Ca… [at] yahoogroups.com Date: Friday, February 27, 2009, 8:06 AM Cayenne pepper added to your bottom paint also voids the paint warranty for what thats worth. --- On Fri, 2/27/09, Alfred Poor <apoor@bellatlantic. net> wrote: From: Alfred Poor <apoor@bellatlantic. net> Subject: [Cal_Boats] Re:Getting a smoothe bah-um, pepper in the paint, was which Bottom Pain To: Cal_Boats@yahoogrou ps.com Date: Friday, February 27, 2009, 5:44 AM Jerry suggested: > Oh yeah, I've heard that some people add Cayenne Pepper (I dont know how much) to the paint to keep the slime from growing, it works like SR supposedly. That was debunked in a “Practical Sailor” issue last fall. It’s best to keep the cayenne pepper on your food (or in your ginger beer) and off your bottom. Alfred Poor 1973 Tartan 34C #288 “Jambalaya”

Well, you answered your own question! I have often thought that the reason the sanding in the direction of water flow works is to keep water in the scratches that does bind to the hull moving in the same direction that the water going by is moving. So, you would have water bound to the hull in the very, very small scratches made by 600 or 1000 grit sand paper (or bronze wool as the case may be) moving slowly down the boat and water that the boat is passing through moving against the water bound in the scratches. So the boat is moving on a water to water boundary that is constantly being refreshed at a rate that is slower than the boat speed, but is still much faster than if the water was bound to the hull in a constricted form -- ie scratches running against the direction of flow. That is why the wax didn't work -- the water never bonded to the hull and, in fact, creating a turbulent hull to water boundary. In addition, you would generate micro-turbulence as the water bound to the hull on a burnished boat moved aft and had to jump the ridges of the cross-flow scratches if you sanded perpendicular to the flow. Of course, there comes a point where the sailor's skill level might just make this whole discussion moot should they foul someone and have to do spins! And rough weather sailing also negates laminar flow and brings skill in boat handling way to the forefront. But, if you have ever sat in an open cockpit boat on Lake Pontchartrain in August (98 degrees with 99% humidity) with a 3 - 5 knot "breeze" then you will truly see the value of laminar flow in getting the heck off the lake and in the swimming pool with a cold beer as fast as possible! Don Dutton, Cal 33-2, "Quantum Evolution" PS I think the toughness of the shark's skin far outweighs his need to move smoothly through the water! After all, I'm old enough to remember the shark-skin toed shoes my mother made me wear in grade school since they would far and away outlast shoes with cow hide toes. Man they were ugly! "Twenty Years from now, you will be more disappointed by the things you didn't do than by the things you did do. So throw off the bowlines. Sail away from the safe harbor. Catch the trade winds in your sails. Explore. Dream. Discover." ........Mark Twain From: Gerald Sobel <so… [at] yahoo.com> To: Ca… [at] yahoogroups.com Sent: Friday, February 27, 2009 9:13:12 AM Subject: [Cal_Boats] Sharkskin anyone? more on Bottoms OK, If laminar flow is so good why to sharks have sand paper skin? And why do swimmers go faster in sharkskin simulated suits? I've heard the sharkskin holds the boundary layer of water to the hull so that you just have water to water friction which is less than water to hull surface friction...or something like that. Jerry. BTW I can see that certain Mexican or Hungarian slime would actually like hot pepper in their bottom paint. --- On Fri, 2/27/09, glen thorpe <glenhove2@yahoo. com> wrote: From: glen thorpe <glenhove2@yahoo. com> Subject: Re: [Cal_Boats] Re:Getting a smoothe bah-um, pepper in the paint, was which Bottom Pain To: Cal_Boats@yahoogrou ps.com Date: Friday, February 27, 2009, 8:06 AM Cayenne pepper added to your bottom paint also voids the paint warranty for what thats worth. --- On Fri, 2/27/09, Alfred Poor <apoor@bellatlantic. net> wrote: From: Alfred Poor <apoor@bellatlantic. net> Subject: [Cal_Boats] Re:Getting a smoothe bah-um, pepper in the paint, was which Bottom Pain To: Cal_Boats@yahoogrou ps.com Date: Friday, February 27, 2009, 5:44 AM Jerry suggested: >Oh yeah, I've heard that some people add Cayenne Pepper (I dont know how much) to the paint to keep the slime from growing, it works like SR supposedly. That was debunked in a “Practical Sailor” issue last fall. It’s best to keep the cayenne pepper on your food (or in your ginger beer) and off your bottom. Alfred Poor 1973 Tartan 34C #288 “Jambalaya”

Many factors create problems with boats moving through water. At least 3 friction factors immediately come to mind. I'm not a naval (navel) architect, so excuse my non-technical descriptions. 1. Turbulence 2. Shear 3. Load Turbulence can come from basic hull design, where laminar flow is disrupted, rough bottoms, rudders, keels, struts, through hulls, propellers, fishing lines. Shear is where the water bonds to the hull surface, and while moving must peel away to reduce friction. "Load" is exiting and re-entering the water (hobby horsing), as the hull is driven deeper, load increases, and as you exit load decreases. It can also include excessive rudder movement "at the wrong time" to brake the movement. So there are some things that you can do to improved the world, some active and some passive. I think the "Shark skin" concepts had two functions, I recall the there were two skins, one dimpled like a golf ball, the other like hairs, laying down. The Golf ball solution was to improve the boundary layer separation (shear), the hair solution worked like a ratchet, if the boat tried to move backwards, like in a wave, the hairs stood up, and created an anti slip action, possibly also an improved shear function. So to fix turbulence problems make the water flow as smoothly as possible. (folding props, inset through hulls, clean bottoms, proper NACA foils, minimized obstacles and hollow spots) Shear also shares some of the same solutions as turbulence, hydrodynamic surfaces that shed, probably smooth, and paints or coatings that minimize laminar shearing forces. Load can be reduced by efforts to keep the boat from "entering and exiting" the water, staying at a level plane. Proper sail selection, weight at ends, overall boat weight, crew positions, proper steering around waves. 0.02 dEmO Cayenne makes my bottom bothered. From: Ca… [at] yahoogroups.com [mailto:Ca… [at] yahoogroups.com] On Behalf Of Gerald Sobel Sent: Friday, February 27, 2009 9:13 AM To: Ca… [at] yahoogroups.com Subject: [Cal_Boats] Sharkskin anyone? more on Bottoms OK, If laminar flow is so good why to sharks have sand paper skin? And why do swimmers go faster in sharkskin simulated suits? I've heard the sharkskin holds the boundary layer of water to the hull so that you just have water to water friction which is less than water to hull surface friction...or something like that. Jerry. BTW I can see that certain Mexican or Hungarian slime would actually like hot pepper in their bottom paint. --- On Fri, 2/27/09, glen thorpe <gl… [at] yahoo.com> wrote: From: glen thorpe <gl… [at] yahoo.com> Subject: Re: [Cal_Boats] Re:Getting a smoothe bah-um, pepper in the paint, was which Bottom Pain To: Ca… [at] yahoogroups.com Date: Friday, February 27, 2009, 8:06 AM Cayenne pepper added to your bottom paint also voids the paint warranty for what thats worth. --- On Fri, 2/27/09, Alfred Poor <apoor@bellatlantic. net> wrote: From: Alfred Poor <apoor@bellatlantic. net> Subject: [Cal_Boats] Re:Getting a smoothe bah-um, pepper in the paint, was which Bottom Pain To: Cal_Boats@yahoogrou ps.com Date: Friday, February 27, 2009, 5:44 AM Jerry suggested: > Oh yeah, I've heard that some people add Cayenne Pepper (I dont know how much) to the paint to keep the slime from growing, it works like SR supposedly. That was debunked in a "Practical Sailor" issue last fall. It's best to keep the cayenne pepper on your food (or in your ginger beer) and off your bottom. Alfred Poor 1973 Tartan 34C #288 "Jambalaya"

--- In Ca… [at] yahoogroups.com, <timmothy.lessley@...> wrote: > > Many factors create problems with boats moving through water. > > At least 3 friction factors immediately come to mind. I'm not a naval (navel) architect, so excuse my non-technical descriptions. > > 1. Turbulence > 2. Shear > 3. Load > > Turbulence can come from basic hull design, where laminar flow is disrupted, rough bottoms, rudders, keels, struts, through hulls, propellers, fishing lines. > > Shear is where the water bonds to the hull surface, and while moving must peel away to reduce friction. > A few more thoughts on drag and turbulence. http://www.aerospaceweb.org/question/aerodynamics/q0215.shtml More on vortex generators on sailboats: http://www.patentstorm.us/patents/5058837/description.html There was a fad for a while of releasing a slippery fluid at the bow to reduce drag but it was quickly banned. Mike Kennedy Conquest Cal 40 # 96

They were using sharkskin plastic coating for a while in the Americas Cup. One of the best racing sailors in Annapolis years ago would always roller on his bottom paint in a just-so stroke and pattern. He was not just cheap. He maintained that the roughness was like the shark skin for water-on-water flow. The fact was that the guy was such a good driver and tactician that the bottom stuff didn't matter much. I've also heard that experiments with sprayed-on teflon were not successful in speed enhancement. Too smooth. I have been a Baltoplate user. Burnishing and all. Baby's butt. However, we had a really hot summer a couple years ago, and the anti-fouling was padoodle. Cheers Charlie From: Ca… [at] yahoogroups.com [mailto:Ca… [at] yahoogroups.com] On Behalf Of mtkennedy1 Sent: Friday, February 27, 2009 3:37 PM To: Ca… [at] yahoogroups.com Subject: [Cal_Boats] Re: Sharkskin anyone? more on Bottoms --- In Ca… [at] yahoogroups.com, <timmothy.lessley@...> wrote: > > Many factors create problems with boats moving through water. > > At least 3 friction factors immediately come to mind. I'm not a naval (navel) architect, so excuse my non-technical descriptions. > > 1. Turbulence > 2. Shear > 3. Load > > Turbulence can come from basic hull design, where laminar flow is disrupted, rough bottoms, rudders, keels, struts, through hulls, propellers, fishing lines. > > Shear is where the water bonds to the hull surface, and while moving must peel away to reduce friction. > A few more thoughts on drag and turbulence. http://www.aerospaceweb.org/question/aerodynamics/q0215.shtml More on vortex generators on sailboats: http://www.patentstorm.us/patents/5058837/description.html There was a fad for a while of releasing a slippery fluid at the bow to reduce drag but it was quickly banned. Mike Kennedy Conquest Cal 40 # 96 ------------------------------------ Yahoo! Groups Links

I agree with Charlie and Mike... bottom paint smoothness is probably a false holygrail. The interaction between sheer and laminar flow layers seems to be a complicated situation- and smoothness doesn't always promote speed. Aerodynamics has quite a bit of information on this topic (aero and hydro or both fluid dynamics at heart). Well in aero they have found that golf ball dimples really create good conditions for the best interaction between sheer and laminar layers of flow. The dimples create small localized turbulance, or mini swirls. Then these mini swirls serve as a lubricant or bearing over which the laminar flow layer can pass faster... basically on top of a small cushion of air. Anyway that's one phenominom in aero-fluid dynamic as best I understand it. Similar things probably happen with water to some extent or more. But the performance gains between a medium smooth and super smooth bottom paint job are probably very minimal. I would spend you time, money and effort on new crisp sails, fine tuning your rig, really fine tuning your rig, and practicing your tactics. Cris From: "Husar, Charlie [USA]" <hu… [at] bah.com> To: Ca… [at] yahoogroups.com Sent: Friday, February 27, 2009 12:44:52 PM Subject: [Cal_Boats] My Bottom They were using sharkskin plastic coating for a while in the Americas Cup. One of the best racing sailors in Annapolis years ago would always roller on his bottom paint in a just-so stroke and pattern. He was not just cheap. He maintained that the roughness was like the shark skin for water-on-water flow. The fact was that the guy was such a good driver and tactician that the bottom stuff didn't matter much. I've also heard that experiments with sprayed-on teflon were not successful in speed enhancement. Too smooth. I have been a Baltoplate user. Burnishing and all. Baby's butt. However, we had a really hot summer a couple years ago, and the anti-fouling was padoodle. Cheers Charlie From: Cal_Boats@yahoogrou ps.com [mailto:Cal_Boats@yahoogrou ps.com] On Behalf Of mtkennedy1 Sent: Friday, February 27, 2009 3:37 PM To: Cal_Boats@yahoogrou ps.com Subject: [Cal_Boats] Re: Sharkskin anyone? more on Bottoms --- In Cal_Boats@yahoogrou ps.com, <timmothy.lessley@ ...> wrote: > > Many factors create problems with boats moving through water. > > At least 3 friction factors immediately come to mind. I'm not a naval (navel) architect, so excuse my non-technical descriptions. > > 1. Turbulence > 2. Shear > 3. Load > > Turbulence can come from basic hull design, where laminar flow is disrupted, rough bottoms, rudders, keels, struts, through hulls, propellers, fishing lines. > > Shear is where the water bonds to the hull surface, and while moving must peel away to reduce friction. > A few more thoughts on drag and turbulence. http://www.aerospac eweb.org/ question/ aerodynamics/ q0215.shtml More on vortex generators on sailboats: http://www.patentst orm.us/patents/ 5058837/descript ion.html There was a fad for a while of releasing a slippery fluid at the bow to reduce drag but it was quickly banned. Mike Kennedy Conquest Cal 40 # 96 ------------ --------- --------- ------ Yahoo! Groups Links

I thought I read somewhere about some experimental boat that had some sort of bubbler things at the bow, or possibly at the front of the keel for this very reason; though perhaps it was a failed experiment, hence why I never heard of it again. It made me think about it for awhile, to be sure, but it seems like trying to make a perpetual motion machine - feasible in hypothesis / ridiculous and impossible in the real world... or something like that. I figured that if you deliberately add bubbles at the bow, there's even more turbulence and the hull would end up sinking further and slowing more... but then that whole "ball bearing" effect may come into play, and that just boggles my tiny inebriated mind further than it's design specs allow! From: Whirled Peas <wh… [at] yahoo.com> To: Ca… [at] yahoogroups.com Sent: Friday, February 27, 2009 4:53:18 PM Subject: Re: [Cal_Boats] My Bottom I agree with Charlie and Mike... bottom paint smoothness is probably a false holygrail. The interaction between sheer and laminar flow layers seems to be a complicated situation- and smoothness doesn't always promote speed. Aerodynamics has quite a bit of information on this topic (aero and hydro or both fluid dynamics at heart). Well in aero they have found that golf ball dimples really create good conditions for the best interaction between sheer and laminar layers of flow. The dimples create small localized turbulance, or mini swirls. Then these mini swirls serve as a lubricant or bearing over which the laminar flow layer can pass faster... basically on top of a small cushion of air. Anyway that's one phenominom in aero-fluid dynamic as best I understand it. Similar things probably happen with water to some extent or more. But the performance gains between a medium smooth and super smooth bottom paint job are probably very minimal. I would spend you time, money and effort on new crisp sails, fine tuning your rig, really fine tuning your rig, and practicing your tactics. Cris From: "Husar, Charlie [USA]" <husar_charlie@ bah.com> To: Cal_Boats@yahoogrou ps.com Sent: Friday, February 27, 2009 12:44:52 PM Subject: [Cal_Boats] My Bottom They were using sharkskin plastic coating for a while in the Americas Cup. One of the best racing sailors in Annapolis years ago would always roller on his bottom paint in a just-so stroke and pattern. He was not just cheap. He maintained that the roughness was like the shark skin for water-on-water flow. The fact was that the guy was such a good driver and tactician that the bottom stuff didn't matter much. I've also heard that experiments with sprayed-on teflon were not successful in speed enhancement. Too smooth. I have been a Baltoplate user. Burnishing and all. Baby's butt. However, we had a really hot summer a couple years ago, and the anti-fouling was padoodle. Cheers Charlie From: Cal_Boats@yahoogrou ps.com [mailto:Cal_Boats@yahoogrou ps.com] On Behalf Of mtkennedy1 Sent: Friday, February 27, 2009 3:37 PM To: Cal_Boats@yahoogrou ps.com Subject: [Cal_Boats] Re: Sharkskin anyone? more on Bottoms --- In Cal_Boats@yahoogrou ps.com, <timmothy.lessley@ ...> wrote: > > Many factors create problems with boats moving through water. > > At least 3 friction factors immediately come to mind. I'm not a naval (navel) architect, so excuse my non-technical descriptions. > > 1. Turbulence > 2. Shear > 3. Load > > Turbulence can come from basic hull design, where laminar flow is disrupted, rough bottoms, rudders, keels, struts, through hulls, propellers, fishing lines. > > Shear is where the water bonds to the hull surface, and while moving must peel away to reduce friction. > A few more thoughts on drag and turbulence. http://www.aerospaceweb.org/question/aerodynamics/q0215.shtml More on vortex generators on sailboats: http://www.patentstorm.us/patents/5058837/description.html There was a fad for a while of releasing a slippery fluid at the bow to reduce drag but it was quickly banned. Mike Kennedy Conquest Cal 40 # 96 ------------ --------- --------- ------ Yahoo! Groups Links

Hi, All. We had the 1970s joke about "pumping polymers" (I think Mike mentioned this). Boat had disguised a hose a line hanging over the bow into the water from which they were pumping "slick" liquids. As Mike points out, it was banned. It is amazing how far some will go to replace talent with deviousness. Some folks think their boat is slow or their rating is bad when, in fact, their driving and tactics are not as good as some other guys. Typically that "slow" boat would be a lot "faster" in the hands of a more talented person, often simply due to how the touch of how the person drives the boat. One well placed tack in a shift makes up for a lot of the "speed" stuff. A clean bottom sure is a good thing, but the paint item is often overrated. Among Olympic champions and pros who have similar high grade talents, I'm sure all the little things truly do add up. OK, off my soap box. Cheers Charlie From: Ca… [at] yahoogroups.com [mailto:Ca… [at] yahoogroups.com] On Behalf Of Lord Nougat Sent: Saturday, February 28, 2009 1:18 AM To: Ca… [at] yahoogroups.com Subject: Re: [Cal_Boats] My Bottom I thought I read somewhere about some experimental boat that had some sort of bubbler things at the bow, or possibly at the front of the keel for this very reason; though perhaps it was a failed experiment, hence why I never heard of it again. It made me think about it for awhile, to be sure, but it seems like trying to make a perpetual motion machine - feasible in hypothesis / ridiculous and impossible in the real world... or something like that. I figured that if you deliberately add bubbles at the bow, there's even more turbulence and the hull would end up sinking further and slowing more... but then that whole "ball bearing" effect may come into play, and that just boggles my tiny inebriated mind further than it's design specs allow! From: Whirled Peas <wh… [at] yahoo.com> To: Ca… [at] yahoogroups.com Sent: Friday, February 27, 2009 4:53:18 PM Subject: Re: [Cal_Boats] My Bottom I agree with Charlie and Mike... bottom paint smoothness is probably a false holygrail. The interaction between sheer and laminar flow layers seems to be a complicated situation- and smoothness doesn't always promote speed. Aerodynamics has quite a bit of information on this topic (aero and hydro or both fluid dynamics at heart). Well in aero they have found that golf ball dimples really create good conditions for the best interaction between sheer and laminar layers of flow. The dimples create small localized turbulance, or mini swirls. Then these mini swirls serve as a lubricant or bearing over which the laminar flow layer can pass faster... basically on top of a small cushion of air. Anyway that's one phenominom in aero-fluid dynamic as best I understand it. Similar things probably happen with water to some extent or more. But the performance gains between a medium smooth and super smooth bottom paint job are probably very minimal. I would spend you time, money and effort on new crisp sails, fine tuning your rig, really fine tuning your rig, and practicing your tactics. Cris From: "Husar, Charlie [USA]" <husar_charlie@ bah.com> To: Cal_Boats@yahoogrou ps.com Sent: Friday, February 27, 2009 12:44:52 PM Subject: [Cal_Boats] My Bottom They were using sharkskin plastic coating for a while in the Americas Cup. One of the best racing sailors in Annapolis years ago would always roller on his bottom paint in a just-so stroke and pattern. He was not just cheap. He maintained that the roughness was like the shark skin for water-on-water flow. The fact was that the guy was such a good driver and tactician that the bottom stuff didn't matter much. I've also heard that experiments with sprayed-on teflon were not successful in speed enhancement. Too smooth. I have been a Baltoplate user. Burnishing and all. Baby's butt. However, we had a really hot summer a couple years ago, and the anti-fouling was padoodle. Cheers Charlie From: Cal_Boats@yahoogrou ps.com <mailto:Cal_Boats%40yahoogroups.com> [mailto:Cal_Boats@yahoogrou ps.com <mailto:Cal_Boats%40yahoogroups.com> ] On Behalf Of mtkennedy1 Sent: Friday, February 27, 2009 3:37 PM To: Cal_Boats@yahoogrou ps.com <mailto:Cal_Boats%40yahoogroups.com> Subject: [Cal_Boats] Re: Sharkskin anyone? more on Bottoms --- In Cal_Boats@yahoogrou ps.com <mailto:Cal_Boats%40yahoogroups.com> , <timmothy.lessley@ ...> wrote: > > Many factors create problems with boats moving through water. > > At least 3 friction factors immediately come to mind. I'm not a naval (navel) architect, so excuse my non-technical descriptions. > > 1. Turbulence > 2. Shear > 3. Load > > Turbulence can come from basic hull design, where laminar flow is disrupted, rough bottoms, rudders, keels, struts, through hulls, propellers, fishing lines. > > Shear is where the water bonds to the hull surface, and while moving must peel away to reduce friction. > A few more thoughts on drag and turbulence. http://www.aerospaceweb.org/question/aerodynamics/q0215.shtml More on vortex generators on sailboats: http://www.patentstorm.us/patents/5058837/description.html There was a fad for a while of releasing a slippery fluid at the bow to reduce drag but it was quickly banned. Mike Kennedy Conquest Cal 40 # 96 ------------ --------- --------- ------ Yahoo! Groups Links

Also I have read that they are studying the shapes of whale fins. They say the irregular shapes help the whale move with less drag and better lifting properties through the water. If I remember they said the irregularity causes eddies that propells the whale. Maybe the shape of a keel and rudder will eventually be modified to resemble a whale fin. Greg P36-2 ----- Original Message ----- From: Gerald Sobel To: Ca… [at] yahoogroups.com Sent: Friday, February 27, 2009 12:13 PM Subject: [Cal_Boats] Sharkskin anyone? more on Bottoms OK, If laminar flow is so good why to sharks have sand paper skin? And why do swimmers go faster in sharkskin simulated suits? I've heard the sharkskin holds the boundary layer of water to the hull so that you just have water to water friction which is less than water to hull surface friction...or something like that. Jerry. BTW I can see that certain Mexican or Hungarian slime would actually like hot pepper in their bottom paint. --- On Fri, 2/27/09, glen thorpe <gl… [at] yahoo.com> wrote: From: glen thorpe <gl… [at] yahoo.com> Subject: Re: [Cal_Boats] Re:Getting a smoothe bah-um, pepper in the paint, was which Bottom Pain To: Ca… [at] yahoogroups.com Date: Friday, February 27, 2009, 8:06 AM Cayenne pepper added to your bottom paint also voids the paint warranty for what thats worth. --- On Fri, 2/27/09, Alfred Poor <apoor@bellatlantic. net> wrote: From: Alfred Poor <apoor@bellatlantic. net> Subject: [Cal_Boats] Re:Getting a smoothe bah-um, pepper in the paint, was which Bottom Pain To: Cal_Boats@yahoogrou ps.com Date: Friday, February 27, 2009, 5:44 AM Jerry suggested: > Oh yeah, I've heard that some people add Cayenne Pepper (I dont know how much) to the paint to keep the slime from growing, it works like SR supposedly. That was debunked in a “Practical Sailor” issue last fall. It’s best to keep the cayenne pepper on your food (or in your ginger beer) and off your bottom. Alfred Poor 1973 Tartan 34C #288 “Jambalaya” ------------------------------------------------------------------------------ No virus found in this incoming message. Checked by AVG. Version: 7.5.557 / Virus Database: 270.11.3 - Release Date: 2/22/2009 12:00 AM

Along the dimple/sharkskin line of thought, I seem to recall one year during the Americas Cup some discussion of this topic. Purposely creating dimples or bumps on the surface of the boat to increase speeds through the water. But it was a long time ago. I believe the races were still held in Newport. Read S. Howarth Moorestown, New Jersey rs… [at] yahoo.com From: mtkennedy1 <mt… [at] cox.net> To: Ca… [at] yahoogroups.com Sent: Friday, February 27, 2009 12:36:52 PM Subject: [Cal_Boats] Re: Sharkskin anyone? more on Bottoms --- In Cal_Boats@yahoogrou ps.com, <timmothy.lessley@ ...> wrote: > > Many factors create problems with boats moving through water. > > At least 3 friction factors immediately come to mind. I'm not a naval (navel) architect, so excuse my non-technical descriptions. > > 1. Turbulence > 2. Shear > 3. Load > > Turbulence can come from basic hull design, where laminar flow is disrupted, rough bottoms, rudders, keels, struts, through hulls, propellers, fishing lines. > > Shear is where the water bonds to the hull surface, and while moving must peel away to reduce friction. > A few more thoughts on drag and turbulence. http://www.aerospac eweb.org/ question/ aerodynamics/ q0215.shtml More on vortex generators on sailboats: http://www.patentst orm.us/patents/ 5058837/descript ion.html There was a fad for a while of releasing a slippery fluid at the bow to reduce drag but it was quickly banned. Mike Kennedy Conquest Cal 40 # 96

On Feb 28, 2009, at 5:36 AM, Husar, Charlie [USA] wrote: > > Hi, All. We had the 1970s joke about "pumping polymers" (I think > Mike mentioned this). Boat had disguised a hose a line hanging over > the bow into the water from which they were pumping "slick" > liquids. As Mike points out, it was banned. It is amazing how far > some will go to replace talent with deviousness. Some folks think > their boat is slow or their rating is bad when, in fact, their > driving and tactics are not as good as some other guys. Typically > that "slow" boat would be a lot "faster" in the hands of a more > talented person, often simply due to how the touch of how the person > drives the boat. One well placed tack in a shift makes up for a lot > of the "speed" stuff. A clean bottom sure is a good thing, but the > paint item is often overrated. Among Olympic champions and pros who > have similar high grade talents, I'm sure all the little things > truly do add up. OK, off my soap box. > > Cheers > Charlie > > Somebody earlier mentioned wax on the bottom. That is really slow. You want it to "wet" as much as possible. That attaches the boundary layer, which is what is fast. Wax prevents wetting and the boundary layer will not attach. For dry sailed boats, sanding down to 600 grit is what makes them fast. Mike Kennedy Conquest Cal 40 # 96 >

a little bubbly in the cockpit makes you think you are sailing faster/better! Reggie To: Ca… [at] yahoogroups.com From: lo… [at] yahoo.com Date: Fri, 27 Feb 2009 22:18:02 -0800 Subject: Re: [Cal_Boats] My Bottom I thought I read somewhere about some experimental boat that had some sort of bubbler things at the bow, or possibly at the front of the keel for this very reason; though perhaps it was a failed experiment, hence why I never heard of it again. It made me think about it for awhile, to be sure, but it seems like trying to make a perpetual motion machine - feasible in hypothesis / ridiculous and impossible in the real world... or something like that. I figured that if you deliberately add bubbles at the bow, there's even more turbulence and the hull would end up sinking further and slowing more... but then that whole "ball bearing" effect may come into play, and that just boggles my tiny inebriated mind further than it's design specs allow! From: Whirled Peas <wh… [at] yahoo.com> To: Ca… [at] yahoogroups.com Sent: Friday, February 27, 2009 4:53:18 PM Subject: Re: [Cal_Boats] My Bottom I agree with Charlie and Mike... bottom paint smoothness is probably a false holygrail. The interaction between sheer and laminar flow layers seems to be a complicated situation- and smoothness doesn't always promote speed. Aerodynamics has quite a bit of information on this topic (aero and hydro or both fluid dynamics at heart). Well in aero they have found that golf ball dimples really create good conditions for the best interaction between sheer and laminar layers of flow. The dimples create small localized turbulance, or mini swirls. Then these mini swirls serve as a lubricant or bearing over which the laminar flow layer can pass faster... basically on top of a small cushion of air. Anyway that's one phenominom in aero-fluid dynamic as best I understand it. Similar things probably happen with water to some extent or more. But the performance gains between a medium smooth and super smooth bottom paint job are probably very minimal. I would spend you time, money and effort on new crisp sails, fine tuning your rig, really fine tuning your rig, and practicing your tactics. Cris From: "Husar, Charlie [USA]" <husar_charlie@ bah.com> To: Cal_Boats@yahoogrou ps.com Sent: Friday, February 27, 2009 12:44:52 PM Subject: [Cal_Boats] My Bottom They were using sharkskin plastic coating for a while in the Americas Cup. One of the best racing sailors in Annapolis years ago would always roller on his bottom paint in a just-so stroke and pattern. He was not just cheap. He maintained that the roughness was like the shark skin for water-on-water flow. The fact was that the guy was such a good driver and tactician that the bottom stuff didn't matter much. I've also heard that experiments with sprayed-on teflon were not successful in speed enhancement. Too smooth. I have been a Baltoplate user. Burnishing and all. Baby's butt. However, we had a really hot summer a couple years ago, and the anti-fouling was padoodle. Cheers Charlie From: Cal_Boats@yahoogrou ps.com [mailto:Cal_Boats@yahoogrou ps.com] On Behalf Of mtkennedy1 Sent: Friday, February 27, 2009 3:37 PM To: Cal_Boats@yahoogrou ps.com Subject: [Cal_Boats] Re: Sharkskin anyone? more on Bottoms --- In Cal_Boats@yahoogrou ps.com, <timmothy.lessley@ ...> wrote: > > Many factors create problems with boats moving through water. > > At least 3 friction factors immediately come to mind. I'm not a naval (navel) architect, so excuse my non-technical descriptions. > > 1. Turbulence > 2. Shear > 3. Load > > Turbulence can come from basic hull design, where laminar flow is disrupted, rough bottoms, rudders, keels, struts, through hulls, propellers, fishing lines. > > Shear is where the water bonds to the hull surface, and while moving must peel away to reduce friction. > A few more thoughts on drag and turbulence. http://www.aerospaceweb.org/question/aerodynamics/q0215.shtml More on vortex generators on sailboats: http://www.patentstorm.us/patents/5058837/description.html There was a fad for a while of releasing a slippery fluid at the bow to reduce drag but it was quickly banned. Mike Kennedy Conquest Cal 40 # 96 ------------ --------- --------- ------ Yahoo! Groups Links