Stus-List Re: Burnished bottom paint
There is some chatter amongst some designers of Catamarans, like Crowther and the Gunboat, but I can’t find any pix. From: dwight veinot via CnC-List [mailto:cnc-list@cnc-list.com] Sent: Wednesday, December 01, 2021 4:42 PM To: Stus-List Cc: dwight veinot Subject: Stus-List Re: Burnished bottom paint So a deleterious effect despite the increased WLL On Wed, Dec 1, 2021 at 5:25 PM Bill Coleman via CnC-List wrote: Found this in Sailing Anarchy – Back to the drawing board. Bulbous bows are designed to "cancel" out the hull's bow wave by inducing their own wave set that has the same frequency, but opposite phase, thereby reducing wave making resistance. To make this work, the boat's speed has be within a very tight specified range and the amplitude of the pitching moment has be relatively small to keep the bulb at the proper depth. Neither of these conditions can be met on a small-ish hull form. The additional wetted surface and form drag eats you up. Was tried in the 70's on 6 Meters and flopped horribly. From: dwight veinot via CnC-List [mailto:cnc-list@cnc-list.com] Sent: Wednesday, December 01, 2021 4:14 PM To: Stus-List Cc: dwight veinot Subject: Stus-List Re: Burnished bottom paint Would a bulbous bow below the waterline help On Tue, Nov 30, 2021 at 9:31 PM schiller via CnC-List wrote: No, but we did add "turbulators" to the tail section of the GBU-24 Bunker Buster Guided Bomb to break up the boundary layer between the bomb body and the wing section, causing turbulent flow over the wings. Neil Schiller 1983 C&C #5-3, #028, "Grace" Whitehall, Michigan On 11/30/2021 6:05 PM, Graham Collins via CnC-List wrote: Indeed. You don't see dimples on the wings of aircraft, for a good reason... Graham Collins CS 36T On 2021-11-30 3:50 p.m., Dreuge via CnC-List wrote: On Nov 30, 2021, at 1:47 PM, Doug via CnC-List wrote: This is the reason golf balls have dimples. Aides in better flight, less resistance. Yes (if spinning) and No (as it adds lateral resistance). Going with a smooth surface is the overall best approach as it promotes smooth laminar flow. There are times when a ruff surface helps maintain laminar flow. For example, the dimples on a golf ball create a thin turbulent layer which drags air and helps keep the lamina flow closer to the surface behind the ball. The dimples add resistance to the flow but reduces the air wake behind the ball which reduces the overall drag force. The laminar flow around a smooth ball does not wrap around the back of the ball as well and leaves a larger wake. The larger the wake, the larger the drag. I think it would be foolish to add dimples or an orange peel bottom, unless you have the resources to model and measure the effect for a particular boat. Maybe adding some aft ruffness as the hull as turns inward, but this will strongly depend on the individual hull shape and likely have a positive effect at high water speeds (and a negative effect at low). Of course, a great way to reduce one's wake is to foil. Most may recall that dimples of a spinning golf ball help in another and bigger way by providing lift(i.e. aids in better flight). The spinning dimples drag air towards incoming flow and drag air away from the flow on the opposite side causing a high/low pressure difference (i.e. lateral lift force). This latter effect has not yet been exploited by sailors. Who knows, maybe we’ll see a spinning belted keel in the future driven by Kiwi’s pedal power. - Paul E. 1981 C&C Landfall 38 S/V Johanna Rose Fort Walton Beach, FL http://svjohannarose.blogspot.com/ Thanks to all of the subscribers that contributed to the list to help with the costs involved. If you want to show your support to the list - use PayPal to send contribution -- https://www.paypal.me/stumurray Thanks - Stu Thanks to all of the subscribers that contributed to the list to help with the costs involved. If you want to show your support to the list - use PayPal to send contribution -- https://www.paypal.me/stumurray Thanks - Stu Thanks to all of the subscribers that contributed to the list to help with the costs involved. If you want to show your support to the list - use PayPal to send contribution -- https://www.paypal.me/stumurray Thanks - Stu -- Sent from Gmail Mobile Thanks to all of the subscribers that contributed to the list to help with the costs involved. If you want to show your support to the list - use PayPal to send contribution -- https://www.paypal.me/stumurray Thanks - Stu -- Sent from Gmail Mobile Thanks to all of the subscribers that contributed to the list to help with the costs involved. If you want to show your support to the list - use PayPal to send contribution -- https://www.paypal.me/stumurray Thanks - Stu
Stus-List Re: Burnished bottom paint
So a deleterious effect despite the increased WLL On Wed, Dec 1, 2021 at 5:25 PM Bill Coleman via CnC-List < cnc-list@cnc-list.com> wrote: > Found this in Sailing Anarchy – > > Back to the drawing board. > > Bulbous bows are designed to "cancel" out the hull's bow wave by inducing > their own wave set that has the same frequency, but opposite phase, thereby > reducing wave making resistance. > > > > To make this work, the boat's speed has be within a very tight specified > range and the amplitude of the pitching moment has be relatively small to > keep the bulb at the proper depth. > > > > Neither of these conditions can be met on a small-ish hull form. The > additional wetted surface and form drag eats you up. > > > > Was tried in the 70's on 6 Meters and flopped horribly. > > > > > > *From:* dwight veinot via CnC-List [mailto:cnc-list@cnc-list.com] > *Sent:* Wednesday, December 01, 2021 4:14 PM > *To:* Stus-List > *Cc:* dwight veinot > *Subject:* Stus-List Re: Burnished bottom paint > > > > Would a bulbous bow below the waterline help > > > > On Tue, Nov 30, 2021 at 9:31 PM schiller via CnC-List < > cnc-list@cnc-list.com> wrote: > > No, but we did add "turbulators" to the tail section of the GBU-24 Bunker > Buster Guided Bomb to break up the boundary layer between the bomb body and > the wing section, causing turbulent flow over the wings. > > Neil Schiller > 1983 C&C #5-3, #028, "Grace" > Whitehall, Michigan > > On 11/30/2021 6:05 PM, Graham Collins via CnC-List wrote: > > Indeed. You don't see dimples on the wings of aircraft, for a good > reason... > > Graham Collins > > CS 36T > > On 2021-11-30 3:50 p.m., Dreuge via CnC-List wrote: > > > > On Nov 30, 2021, at 1:47 PM, Doug via CnC-List > wrote: > > > > This is the reason golf balls have dimples. Aides in better flight, less > resistance. > > > > > > > > > > Yes (if spinning) and No (as it adds lateral resistance). > > > > Going with a smooth surface is the overall best approach as it promotes > smooth laminar flow. There are times when a ruff surface helps maintain > laminar flow. For example, the dimples on a golf ball create a thin > turbulent layer which drags air and helps keep the lamina flow closer to > the surface behind the ball. The dimples add resistance to the flow but > reduces the air wake behind the ball which reduces the overall drag force. > The laminar flow around a smooth ball does not wrap around the back of the > ball as well and leaves a larger wake. The larger the wake, the larger the > drag. > > > > I think it would be foolish to add dimples or an orange peel bottom, > unless you have the resources to model and measure the effect for a > particular boat. Maybe adding some aft ruffness as the hull as turns > inward, but this will strongly depend on the individual hull shape and > likely have a positive effect at high water speeds (and a negative effect > at low). Of course, a great way to reduce one's wake is to foil. > > > > Most may recall that dimples of a spinning golf ball help in another and > bigger way by providing lift(i.e. aids in better flight). The spinning > dimples drag air towards incoming flow and drag air away from the flow on > the opposite side causing a high/low pressure difference (i.e. lateral > lift force). This latter effect has not yet been exploited by sailors. > Who knows, maybe we’ll see a spinning belted keel in the future driven by > Kiwi’s pedal power. > > > > > > - > Paul E. > > 1981 C&C Landfall 38 > S/V Johanna Rose > Fort Walton Beach, FL > > > > http://svjohannarose.blogspot.com/ > > > > > > > > > > Thanks to all of the subscribers that contributed to the list to help with > the costs involved. If you want to show your support to the list - use > PayPal to send contribution -- https://www.paypal.me/stumurray Thanks - Stu > > > > Thanks to all of the subscribers that contributed to the list to help with > the costs involved. If you want to show your support to the list - use > PayPal to send contribution -- https://www.paypal.me/stumurray Thanks - Stu > > > > Thanks to all of the subscribers that contributed to the list to help with > the costs involved. If you want to show your support to the list - use > PayPal to send contribution -- https://www.paypal.me/stumurray Thanks > - Stu > > -- > > Sent from Gmail Mobile > Thanks to all of the subscribers that contributed to the list to help with > the costs involved. If you want to show your support to the list - use > PayPal to send contribution -- https://www.paypal.me/stumurray Thanks > - Stu -- Sent from Gmail Mobile Thanks to all of the subscribers that contributed to the list to help with the costs involved. If you want to show your support to the list - use PayPal to send contribution -- https://www.paypal.me/stumurray Thanks - Stu
Stus-List Re: Burnished bottom paint
Found this in Sailing Anarchy – Back to the drawing board. Bulbous bows are designed to "cancel" out the hull's bow wave by inducing their own wave set that has the same frequency, but opposite phase, thereby reducing wave making resistance. To make this work, the boat's speed has be within a very tight specified range and the amplitude of the pitching moment has be relatively small to keep the bulb at the proper depth. Neither of these conditions can be met on a small-ish hull form. The additional wetted surface and form drag eats you up. Was tried in the 70's on 6 Meters and flopped horribly. From: dwight veinot via CnC-List [mailto:cnc-list@cnc-list.com] Sent: Wednesday, December 01, 2021 4:14 PM To: Stus-List Cc: dwight veinot Subject: Stus-List Re: Burnished bottom paint Would a bulbous bow below the waterline help On Tue, Nov 30, 2021 at 9:31 PM schiller via CnC-List wrote: No, but we did add "turbulators" to the tail section of the GBU-24 Bunker Buster Guided Bomb to break up the boundary layer between the bomb body and the wing section, causing turbulent flow over the wings. Neil Schiller 1983 C&C #5-3, #028, "Grace" Whitehall, Michigan On 11/30/2021 6:05 PM, Graham Collins via CnC-List wrote: Indeed. You don't see dimples on the wings of aircraft, for a good reason... Graham Collins CS 36T On 2021-11-30 3:50 p.m., Dreuge via CnC-List wrote: On Nov 30, 2021, at 1:47 PM, Doug via CnC-List wrote: This is the reason golf balls have dimples. Aides in better flight, less resistance. Yes (if spinning) and No (as it adds lateral resistance). Going with a smooth surface is the overall best approach as it promotes smooth laminar flow. There are times when a ruff surface helps maintain laminar flow. For example, the dimples on a golf ball create a thin turbulent layer which drags air and helps keep the lamina flow closer to the surface behind the ball. The dimples add resistance to the flow but reduces the air wake behind the ball which reduces the overall drag force. The laminar flow around a smooth ball does not wrap around the back of the ball as well and leaves a larger wake. The larger the wake, the larger the drag. I think it would be foolish to add dimples or an orange peel bottom, unless you have the resources to model and measure the effect for a particular boat. Maybe adding some aft ruffness as the hull as turns inward, but this will strongly depend on the individual hull shape and likely have a positive effect at high water speeds (and a negative effect at low). Of course, a great way to reduce one's wake is to foil. Most may recall that dimples of a spinning golf ball help in another and bigger way by providing lift(i.e. aids in better flight). The spinning dimples drag air towards incoming flow and drag air away from the flow on the opposite side causing a high/low pressure difference (i.e. lateral lift force). This latter effect has not yet been exploited by sailors. Who knows, maybe we’ll see a spinning belted keel in the future driven by Kiwi’s pedal power. - Paul E. 1981 C&C Landfall 38 S/V Johanna Rose Fort Walton Beach, FL http://svjohannarose.blogspot.com/ Thanks to all of the subscribers that contributed to the list to help with the costs involved. If you want to show your support to the list - use PayPal to send contribution -- https://www.paypal.me/stumurray Thanks - Stu Thanks to all of the subscribers that contributed to the list to help with the costs involved. If you want to show your support to the list - use PayPal to send contribution -- https://www.paypal.me/stumurray Thanks - Stu Thanks to all of the subscribers that contributed to the list to help with the costs involved. If you want to show your support to the list - use PayPal to send contribution -- https://www.paypal.me/stumurray Thanks - Stu -- Sent from Gmail Mobile Thanks to all of the subscribers that contributed to the list to help with the costs involved. If you want to show your support to the list - use PayPal to send contribution -- https://www.paypal.me/stumurray Thanks - Stu
Stus-List Re: Burnished bottom paint
Would a bulbous bow below the waterline help On Tue, Nov 30, 2021 at 9:31 PM schiller via CnC-List wrote: > No, but we did add "turbulators" to the tail section of the GBU-24 Bunker > Buster Guided Bomb to break up the boundary layer between the bomb body and > the wing section, causing turbulent flow over the wings. > > Neil Schiller > 1983 C&C #5-3, #028, "Grace" > Whitehall, Michigan > > On 11/30/2021 6:05 PM, Graham Collins via CnC-List wrote: > > Indeed. You don't see dimples on the wings of aircraft, for a good > reason... > > Graham Collins > CS 36T > > On 2021-11-30 3:50 p.m., Dreuge via CnC-List wrote: > > > On Nov 30, 2021, at 1:47 PM, Doug via CnC-List > wrote: > > This is the reason golf balls have dimples. Aides in better flight, less > resistance. > > > > > Yes (if spinning) and No (as it adds lateral resistance). > > Going with a smooth surface is the overall best approach as it promotes > smooth laminar flow. There are times when a ruff surface helps maintain > laminar flow. For example, the dimples on a golf ball create a thin > turbulent layer which drags air and helps keep the lamina flow closer to > the surface behind the ball. The dimples add resistance to the flow but > reduces the air wake behind the ball which reduces the overall drag force. > The laminar flow around a smooth ball does not wrap around the back of the > ball as well and leaves a larger wake. The larger the wake, the larger the > drag. > > I think it would be foolish to add dimples or an orange peel bottom, > unless you have the resources to model and measure the effect for a > particular boat. Maybe adding some aft ruffness as the hull as turns > inward, but this will strongly depend on the individual hull shape and > likely have a positive effect at high water speeds (and a negative effect > at low). Of course, a great way to reduce one's wake is to foil. > > Most may recall that dimples of a spinning golf ball help in another and > bigger way by providing lift(i.e. aids in better flight). The spinning > dimples drag air towards incoming flow and drag air away from the flow on > the opposite side causing a high/low pressure difference (i.e. lateral > lift force). This latter effect has not yet been exploited by sailors. > Who knows, maybe we’ll see a spinning belted keel in the future driven by > Kiwi’s pedal power. > > > - > Paul E. > 1981 C&C Landfall 38 > S/V Johanna Rose > Fort Walton Beach, FL > > http://svjohannarose.blogspot.com/ > > > > > > Thanks to all of the subscribers that contributed to the list to help with > the costs involved. If you want to show your support to the list - use > PayPal to send contribution -- https://www.paypal.me/stumurray Thanks - Stu > > > Thanks to all of the subscribers that contributed to the list to help with > the costs involved. If you want to show your support to the list - use > PayPal to send contribution -- https://www.paypal.me/stumurray Thanks - Stu > > > Thanks to all of the subscribers that contributed to the list to help with > the costs involved. If you want to show your support to the list - use > PayPal to send contribution -- https://www.paypal.me/stumurray Thanks > - Stu -- Sent from Gmail Mobile Thanks to all of the subscribers that contributed to the list to help with the costs involved. If you want to show your support to the list - use PayPal to send contribution -- https://www.paypal.me/stumurray Thanks - Stu
Stus-List Re: Burnished bottom paint
No, but we did add "turbulators" to the tail section of the GBU-24 Bunker Buster Guided Bomb to break up the boundary layer between the bomb body and the wing section, causing turbulent flow over the wings. Neil Schiller 1983 C&C #5-3, #028, "Grace" Whitehall, Michigan On 11/30/2021 6:05 PM, Graham Collins via CnC-List wrote: Indeed. You don't see dimples on the wings of aircraft, for a good reason... Graham Collins CS 36T On 2021-11-30 3:50 p.m., Dreuge via CnC-List wrote: On Nov 30, 2021, at 1:47 PM, Doug via CnC-List wrote: This is the reason golf balls have dimples. Aides in better flight, less resistance. Yes (if spinning) and No (as it adds lateral resistance). Going with a smooth surface is the overall best approach as it promotes smooth laminar flow. There are times when a ruff surface helps maintain laminar flow. For example, the dimples on a golf ball create a thin turbulent layer which drags air and helps keep the lamina flow closer to the surface behind the ball. The dimples add resistance to the flow but reduces the air wake behind the ball which reduces the overall drag force. The laminar flow around a smooth ball does not wrap around the back of the ball as well and leaves a larger wake. The larger the wake, the larger the drag. I think it would be foolish to add dimples or an orange peel bottom, unless you have the resources to model and measure the effect for a particular boat. Maybe adding some aft ruffness as the hull as turns inward, but this will strongly depend on the individual hull shape and likely have a positive effect at high water speeds (and a negative effect at low). Of course, a great way to reduce one's wake is to foil. Most may recall that dimples of a spinning golf ball help in another and bigger way by providing lift(i.e. aids in better flight). The spinning dimples drag air towards incoming flow and drag air away from the flow on the opposite side causing a high/low pressure difference (i.e. lateral lift force). This latter effect has not yet been exploited by sailors. Who knows, maybe we’ll see a spinning belted keel in the future driven by Kiwi’s pedal power. - Paul E. 1981 C&C Landfall 38 S/V Johanna Rose Fort Walton Beach, FL http://svjohannarose.blogspot.com/ Thanks to all of the subscribers that contributed to the list to help with the costs involved. If you want to show your support to the list - use PayPal to send contribution --https://www.paypal.me/stumurray Thanks - Stu Thanks to all of the subscribers that contributed to the list to help with the costs involved. If you want to show your support to the list - use PayPal to send contribution -- https://www.paypal.me/stumurray Thanks - Stu Thanks to all of the subscribers that contributed to the list to help with the costs involved. If you want to show your support to the list - use PayPal to send contribution -- https://www.paypal.me/stumurray Thanks - Stu
Stus-List Re: Burnished bottom paint
Indeed. You don't see dimples on the wings of aircraft, for a good reason... Graham Collins CS 36T On 2021-11-30 3:50 p.m., Dreuge via CnC-List wrote: On Nov 30, 2021, at 1:47 PM, Doug via CnC-List wrote: This is the reason golf balls have dimples. Aides in better flight, less resistance. Yes (if spinning) and No (as it adds lateral resistance). Going with a smooth surface is the overall best approach as it promotes smooth laminar flow. There are times when a ruff surface helps maintain laminar flow. For example, the dimples on a golf ball create a thin turbulent layer which drags air and helps keep the lamina flow closer to the surface behind the ball. The dimples add resistance to the flow but reduces the air wake behind the ball which reduces the overall drag force. The laminar flow around a smooth ball does not wrap around the back of the ball as well and leaves a larger wake. The larger the wake, the larger the drag. I think it would be foolish to add dimples or an orange peel bottom, unless you have the resources to model and measure the effect for a particular boat. Maybe adding some aft ruffness as the hull as turns inward, but this will strongly depend on the individual hull shape and likely have a positive effect at high water speeds (and a negative effect at low). Of course, a great way to reduce one's wake is to foil. Most may recall that dimples of a spinning golf ball help in another and bigger way by providing lift(i.e. aids in better flight). The spinning dimples drag air towards incoming flow and drag air away from the flow on the opposite side causing a high/low pressure difference (i.e. lateral lift force). This latter effect has not yet been exploited by sailors. Who knows, maybe we’ll see a spinning belted keel in the future driven by Kiwi’s pedal power. - Paul E. 1981 C&C Landfall 38 S/V Johanna Rose Fort Walton Beach, FL http://svjohannarose.blogspot.com/ Thanks to all of the subscribers that contributed to the list to help with the costs involved. If you want to show your support to the list - use PayPal to send contribution --https://www.paypal.me/stumurray Thanks - StuThanks to all of the subscribers that contributed to the list to help with the costs involved. If you want to show your support to the list - use PayPal to send contribution -- https://www.paypal.me/stumurray Thanks - Stu
Stus-List Re: Burnished bottom paint
> On Nov 30, 2021, at 1:47 PM, Doug via CnC-List wrote: > > This is the reason golf balls have dimples. Aides in better flight, less > resistance. > > > Yes (if spinning) and No (as it adds lateral resistance). Going with a smooth surface is the overall best approach as it promotes smooth laminar flow. There are times when a ruff surface helps maintain laminar flow. For example, the dimples on a golf ball create a thin turbulent layer which drags air and helps keep the lamina flow closer to the surface behind the ball. The dimples add resistance to the flow but reduces the air wake behind the ball which reduces the overall drag force. The laminar flow around a smooth ball does not wrap around the back of the ball as well and leaves a larger wake. The larger the wake, the larger the drag. I think it would be foolish to add dimples or an orange peel bottom, unless you have the resources to model and measure the effect for a particular boat. Maybe adding some aft ruffness as the hull as turns inward, but this will strongly depend on the individual hull shape and likely have a positive effect at high water speeds (and a negative effect at low). Of course, a great way to reduce one's wake is to foil. Most may recall that dimples of a spinning golf ball help in another and bigger way by providing lift(i.e. aids in better flight). The spinning dimples drag air towards incoming flow and drag air away from the flow on the opposite side causing a high/low pressure difference (i.e. lateral lift force). This latter effect has not yet been exploited by sailors. Who knows, maybe we’ll see a spinning belted keel in the future driven by Kiwi’s pedal power. - Paul E. 1981 C&C Landfall 38 S/V Johanna Rose Fort Walton Beach, FL http://svjohannarose.blogspot.com/ Thanks to all of the subscribers that contributed to the list to help with the costs involved. If you want to show your support to the list - use PayPal to send contribution -- https://www.paypal.me/stumurray Thanks - Stu
Stus-List Re: Burnished bottom paint
This is the reason golf balls have dimples. Aides in better flight, less resistance. Doug Mountjoy sv Rebecca Leah C & C Landfall 39Port Orchard Yacht Club Port Orchard, WA Thanks to all of the subscribers that contributed to the list to help with the costs involved. If you want to show your support to the list - use PayPal to send contribution -- https://www.paypal.me/stumurray Thanks - Stu
Stus-List Re: Burnished bottom paint
Dave, I use Interlux VC Offshore for my race boat, j-24 and Interlux micron WA on my cruising boat, a 36-1, Talisman, (Which is about three boats behind you at your winter yard.) Both boats sit in the Mystic River. I did an original spray job on the 24 three years ago and now just do a touch up roll and tip and then wet sand down to 1000. I have burnished with steel wool in the past but really do not think it gets it much better than the 1000 grit. Usually, the mistakes we make above water more than cancel out anything bottom related! I just made the switch to the Micron on the 36 and while it is not designed to be a race bottom paint I really like it. Easy water-based cleanup and covers great and pretty good protection. I have found that VC Offshore and Baltoplate seem to be the primary racing paints used around here and the antifouling characteristics are not that great. I need to scrub weekly for wed night races and if I am doing a sat regatta it will need it again. A lot of locals are using Petit Vivid as well. It is a harder paint than the ablatives. Not sure if you can actually burnish it. Practical Sailor has done some good paint review tests but they are not evaluating speed. Good luck! John McCrea Mystic, CT Talisman 1979-36-1 Cluster Duck J24 From: David Knecht via CnC-List Sent: Tuesday, November 30, 2021 12:46 PM To: CnC CnC discussion list Cc: David Knecht Subject: Stus-List Burnished bottom paint I have been considering what kind of bottom paint to use in the future and it seems that most racers have a very hard/smooth/burnished bottom on their boats. So, I was wondering if there is data to support that this is important. One reason for asking is that in addition to being a sailor, I am also a cyclist. A few years ago, the hypothesis that was accepted by all cyclists, including pro teams, was that thin, high pressure tires were the fastest. Then someone actually did the experimental science, and found that wider, lower pressure tires were actually as fast or faster. Counterintuitive, but data trumps intuition, and that is why we should test obvious and intuitive assumptions. So my question is, has anyone seen actual experimental data on comparing different smoothnesses and type of bottom paint vs. boat speed under controlled conditions? Thanks- Dave S/V Aries 1990 C&C 34+ New London, CT Thanks to all of the subscribers that contributed to the list to help with the costs involved. If you want to show your support to the list - use PayPal to send contribution -- https://www.paypal.me/stumurray Thanks - Stu
