Re: [bolger] Re: Wasps and Speed
The transonic area rule relates to the formation of shocks, which is a phenomenon related to the compressibility of air. Since water is incompressible for all purposes related to the topic of this community, there's no direct analogy. That does not mean that it's not something worth exploring; just that if it works it will be through some other (possibly even related) mechanism.
-p
-p
On Fri, Sep 25, 2009 at 2:30 PM, Fred Schumacher<fredschum@...>wrote:Water has a higher Reynolds Number than air, so constant area rule effects would happen at lower speeds. I've thought that wasp waisting a box keel at a wing keel attachment area would be worth trying. There are underwater flow issues we don't understand well. Fin keels placed aft of the underwater center of pressure can reduce drag and raise hull speed. Bolger was a very intuitive thinker and he may have been on to something that there just wasn't enough time to develop. That's for us to do.FredOn Thu, Sep 24, 2009 at 6:12 PM, graeme19121984<graeme19121984@...>wrote:Yes Jon, I don't 'see' it either, except that the Pacific proa hulls with the "dimple" actually are faster, and PCB thought "wasp-waisting" (whatever that actually looks like) worth trying. Theoretically, fast swimming fish, dolphins, etc, should not be able to swim as fast as they do on the power they have. Fish are soft bodied, subs currently have to be hard.
In the MAIB write-up of the Col Hasler design I recall PB&F mention something like how the box keel shifts displacement and frees the hull from bogging down in its own waves, mid-body. You would think that introducing a waist to a box keel would increase the displacement shifting, and that it just may grant more speed. No doubt there'd have to be some trade-offs, some to do with increasing flow along the keel. What if that flow lowered pressure and decreased the drag of eddying flow under the keel?
I know, there's a lot of 'what ifs', but...?
Graeme
--- Inbolger@yahoogroups.com, "adventures_in_astrophotography" <jon@...> wrote:
> I don't see where the shape would improve the flow around a boat hull, but I could see it used in an attempt to get a flatter displacement curve. I'm not sure the benefit would be worth the trouble. Note that the fastest submarines and fish are all streamlined teardrop shapes. One might expect evolution to produce a different shape if it would provide an advantage.
>
> Jon
>
Water has a higher Reynolds Number than air, so constant area rule effects would happen at lower speeds. I've thought that wasp waisting a box keel at a wing keel attachment area would be worth trying. There are underwater flow issues we don't understand well. Fin keels placed aft of the underwater center of pressure can reduce drag and raise hull speed. Bolger was a very intuitive thinker and he may have been on to something that there just wasn't enough time to develop. That's for us to do.
Fred
On Thu, Sep 24, 2009 at 6:12 PM, graeme19121984<graeme19121984@...>wrote:Yes Jon, I don't 'see' it either, except that the Pacific proa hulls with the "dimple" actually are faster, and PCB thought "wasp-waisting" (whatever that actually looks like) worth trying. Theoretically, fast swimming fish, dolphins, etc, should not be able to swim as fast as they do on the power they have. Fish are soft bodied, subs currently have to be hard.
In the MAIB write-up of the Col Hasler design I recall PB&F mention something like how the box keel shifts displacement and frees the hull from bogging down in its own waves, mid-body. You would think that introducing a waist to a box keel would increase the displacement shifting, and that it just may grant more speed. No doubt there'd have to be some trade-offs, some to do with increasing flow along the keel. What if that flow lowered pressure and decreased the drag of eddying flow under the keel?
I know, there's a lot of 'what ifs', but...?
Graeme
--- Inbolger@yahoogroups.com, "adventures_in_astrophotography" <jon@...> wrote:
> I don't see where the shape would improve the flow around a boat hull, but I could see it used in an attempt to get a flatter displacement curve. I'm not sure the benefit would be worth the trouble. Note that the fastest submarines and fish are all streamlined teardrop shapes. One might expect evolution to produce a different shape if it would provide an advantage.
>
> Jon
>
Yes Jon, I don't 'see' it either, except that the Pacific proa hulls with the "dimple" actually are faster, and PCB thought "wasp-waisting" (whatever that actually looks like) worth trying. Theoretically, fast swimming fish, dolphins, etc, should not be able to swim as fast as they do on the power they have. Fish are soft bodied, subs currently have to be hard.
In the MAIB write-up of the Col Hasler design I recall PB&F mention something like how the box keel shifts displacement and frees the hull from bogging down in its own waves, mid-body. You would think that introducing a waist to a box keel would increase the displacement shifting, and that it just may grant more speed. No doubt there'd have to be some trade-offs, some to do with increasing flow along the keel. What if that flow lowered pressure and decreased the drag of eddying flow under the keel?
I know, there's a lot of 'what ifs', but...?
Graeme
In the MAIB write-up of the Col Hasler design I recall PB&F mention something like how the box keel shifts displacement and frees the hull from bogging down in its own waves, mid-body. You would think that introducing a waist to a box keel would increase the displacement shifting, and that it just may grant more speed. No doubt there'd have to be some trade-offs, some to do with increasing flow along the keel. What if that flow lowered pressure and decreased the drag of eddying flow under the keel?
I know, there's a lot of 'what ifs', but...?
Graeme
--- Inbolger@yahoogroups.com, "adventures_in_astrophotography" <jon@...> wrote:
> I don't see where the shape would improve the flow around a boat hull, but I could see it used in an attempt to get a flatter displacement curve. I'm not sure the benefit would be worth the trouble. Note that the fastest submarines and fish are all streamlined teardrop shapes. One might expect evolution to produce a different shape if it would provide an advantage.
>
> Jon
>
The car shape is sometimes called a banana car. It is
mostly for aero efficiency, to lower the coefficient of friction. These cars
will also generally have the underside of the vehicle smoothed. The wheel
well/fender/tire is a high pressure area. The banana gives a low pressure area
between the front and rear wheels. The shape is basically a fairing for the
wheels. These cars will also have a chin spoiler to limit the turbulence/drag on
the underbody.
MylesJ
Agreed. Hollows underwater are slow.
On Thu, Sep 24, 2009 at 9:45 AM, adventures_in_astrophotography<jon@...>wrote:Graeme and Gene,
Controlled supersonic flight was not possible until the application of the "coke-bottle" area rule. During WWII, pilots in high speed dives approaching near-sonic speeds encountered tremendous buffeting and loss of control. Following WWII, more than one aircraft with enough jet thrust to reach the transonic boundary broke apart in mid-air due to its inability to break cleanly through the supersonic shock front. Even when the planes didn't break up, the experiences of Chuck Yeager and others in the early X-plane development program showed that aircraft would become completely uncontrollable as they attempted to break the shock front. There are some specatcular films from these test flights. It took some real stones to fly those things.
> My limited understanding of the 'why and how' of the "coke-bottle" shape in the trans-sonic aircraft is as you describe. The sudden volume increase caused by the wing roots at the fuselage cause drag, and the fuselage waisting has been used to reduce that volume increase.
I don't see where the shape would improve the flow around a boat hull, but I could see it used in an attempt to get a flatter displacement curve. I'm not sure the benefit would be worth the trouble. Note that the fastest submarines and fish are all streamlined teardrop shapes. One might expect evolution to produce a different shape if it would provide an advantage.
Jon
Graeme and Gene,
I don't see where the shape would improve the flow around a boat hull, but I could see it used in an attempt to get a flatter displacement curve. I'm not sure the benefit would be worth the trouble. Note that the fastest submarines and fish are all streamlined teardrop shapes. One might expect evolution to produce a different shape if it would provide an advantage.
Jon
> My limited understanding of the 'why and how' of the "coke-bottle" shape in the trans-sonic aircraft is as you describe. The sudden volume increase caused by the wing roots at the fuselage cause drag, and the fuselage waisting has been used to reduce that volume increase.Controlled supersonic flight was not possible until the application of the "coke-bottle" area rule. During WWII, pilots in high speed dives approaching near-sonic speeds encountered tremendous buffeting and loss of control. Following WWII, more than one aircraft with enough jet thrust to reach the transonic boundary broke apart in mid-air due to its inability to break cleanly through the supersonic shock front. Even when the planes didn't break up, the experiences of Chuck Yeager and others in the early X-plane development program showed that aircraft would become completely uncontrollable as they attempted to break the shock front. There are some specatcular films from these test flights. It took some real stones to fly those things.
I don't see where the shape would improve the flow around a boat hull, but I could see it used in an attempt to get a flatter displacement curve. I'm not sure the benefit would be worth the trouble. Note that the fastest submarines and fish are all streamlined teardrop shapes. One might expect evolution to produce a different shape if it would provide an advantage.
Jon
Gene, I too find it hard to follow!
My limited understanding of the 'why and how' of the "coke-bottle" shape in the trans-sonic aircraft is as you describe. The sudden volume increase caused by the wing roots at the fuselage cause drag, and the fuselage waisting has been used to reduce that volume increase.
Perhaps that may transfer to the problem in boat design of the root of a fin keel, especially on a racing boat. However, I can see some large differences between the aircraft and boat in that the aircraft fuselage from the nose back is (mostly, usually) a straight tube whereas the boat hull is a swelling convex shape. I understand fin keel roots have been the subject of much racing design attention, yet I don't believe I've seen hull waisting or "coke-bottling" in the solutions presented so far. I think the box keel, being full length and adding greatly to the hull volume, like having a canoe stuck under a boat of similar length, likely has a different effect on the water flow to that of the relatively suddenly introduced shorter chord fin keel.
BTW I've noticed sometimes that the mid-body skirts on racing cars (and some pretend street models) are wasp-waisted. Presumably on the race car this is for more than looks, and is used to streamline airflow. Importantly here, perhaps it's also meant to lower air pressure and stick the car harder to the tar? -- Not what you'd want in a boat.
The straight, parallel-sided, box keel might lessen the overall curved hull "suck-down" Bernouli effect (of lower fluid pressure with increasing velocity). It may also cheat Newton's third law of motion (the water flow-path is turned by the convex hull, the reaction sinks the hull deeper). Would "coke-bottling", wasp-waisting, or maybe just a little "dimpling" of the box keel turn Newton's third law to advantage - the reaction being then to act to lift the hull?
Graeme
My limited understanding of the 'why and how' of the "coke-bottle" shape in the trans-sonic aircraft is as you describe. The sudden volume increase caused by the wing roots at the fuselage cause drag, and the fuselage waisting has been used to reduce that volume increase.
Perhaps that may transfer to the problem in boat design of the root of a fin keel, especially on a racing boat. However, I can see some large differences between the aircraft and boat in that the aircraft fuselage from the nose back is (mostly, usually) a straight tube whereas the boat hull is a swelling convex shape. I understand fin keel roots have been the subject of much racing design attention, yet I don't believe I've seen hull waisting or "coke-bottling" in the solutions presented so far. I think the box keel, being full length and adding greatly to the hull volume, like having a canoe stuck under a boat of similar length, likely has a different effect on the water flow to that of the relatively suddenly introduced shorter chord fin keel.
BTW I've noticed sometimes that the mid-body skirts on racing cars (and some pretend street models) are wasp-waisted. Presumably on the race car this is for more than looks, and is used to streamline airflow. Importantly here, perhaps it's also meant to lower air pressure and stick the car harder to the tar? -- Not what you'd want in a boat.
The straight, parallel-sided, box keel might lessen the overall curved hull "suck-down" Bernouli effect (of lower fluid pressure with increasing velocity). It may also cheat Newton's third law of motion (the water flow-path is turned by the convex hull, the reaction sinks the hull deeper). Would "coke-bottling", wasp-waisting, or maybe just a little "dimpling" of the box keel turn Newton's third law to advantage - the reaction being then to act to lift the hull?
Graeme
--- Inbolger@yahoogroups.com, Gene Tehansky <goldranger02-boats@...> wrote:
>
> Graeme,
> I read in the distant past that on aircraft, the coke bottle shape was
> done so that the aircraft would have a more constant cross sectional
> area. Slice down vertically across the aircraft and measure the area,
> first near the nose then moving back then through the winged portion
> of the aircraft. The wings add area therefore the body is reduced in
> that area to maintain a constant. I'm not sure but this might only be
> an issue for supersonic speeds.
>
> I also recall something about dolphins or sharks doing something to
> their skin to reduce friction. It might have been rippling or
> something like that.
>
> If this is all just silly talk press the delete button, I have not
> been following this thread very closely.
>
> Sincerely,
> Gene T.
You're correct that the area rule (the cause for the wasp-waisted form of early jet fighters) was for supersonic speeds. It's therefore not directly applicable to boats, since water flow isn't compressible at any reasonable speed.
-p
-p
On Wed, Sep 23, 2009 at 4:03 PM, Gene Tehansky<goldranger02-boats@...>wrote:
Graeme,I read in the distant past that on aircraft, the coke bottle shape was done so that the aircraft would have a more constant cross sectional area. Slice down vertically across the aircraft and measure the area, first near the nose then moving back then through the winged portion of the aircraft. The wings add area therefore the body is reduced in that area to maintain a constant. I'm not sure but this might only be an issue for supersonic speeds.I also recall something about dolphins or sharks doing something to their skin to reduce friction. It might have been rippling or something like that.If this is all just silly talk press the delete button, I have not been following this thread very closely.Sincerely,Gene T.On 23 Sep, 2009, at 6:42 PM, graeme19121984 wrote:> I meant to ask the group a few questions about this, but was in a rush yeterday. So:-.
As _30-Odd Boats_ was published in 1982, 27 years ago, and Phil had been proceeding on this line of development for around 25 years up to then (p.123), did any designs with the next developmental progressions of a wasp-waist 'veed' sponson get built? How'd they go?
Would the effects of wasp-waisting (or "dimpling") transfer to a box-keel sponson? And that under a sharpie type?
How does wasp-waisting work better to shift displacement to the ends and grant higher speed? I can immediately see how the parallel sided sponson cancels or reduces the "suck-down" Bernouli effect amidships of a typically swelling hull shape, but how does introducing a convex curve to the sponson amidships improve things over the straight and parallel sided? Either curve means a longer flow path, means higher flow velocity in way of the curve, means lower pressure there, means sinking lower, means bigger wave-making, means slower, doesn't it? What else is at play that I don't see?
Graeme
> I meant to ask the group a few questions about this, but was in a rush yeterday. So:As _30-Odd Boats_ was published in 1982, 27 years ago, and Phil had been proceeding on this line of development for around 25 years up to then (p.123), did any designs with the next developmental progressions of a wasp-waist 'veed-box' keel get built? How'd they go?
Would the effects of wasp-waisting (or "dimpling") transfer to a square-box keel? And that under a sharpie type sponson hull?
How does wasp-waisting the keel work better to shift displacement to the hull ends and grant higher speed? I can immediately see how the parallel sided keel cancels or reduces the "suck-down" Bernouli effect amidships of a typically swelling shape, but how does introducing a convex curve to the keel amidships improve things over the straight and parallel sided? Either curve means a longer flow path, means higher flow velocity in way of the curve, means lower pressure there, means sinking lower, means bigger wave-making, means slower, doesn't it? What else is at play that I don't see?
Graeme
--- Inbolger@yahoogroups.com, "graeme19121984" <graeme19121984@...> wrote:
>
> From 'QUEST' (Chapter 18, 30-ODD):
>
> "I'd finally awakened to the conclusion that keels like this one give a much better distribution of displacement if they have parallel sides for most of their length, with the fairing just at the ends. If it's faired in a smooth sweep from end to end, like a canoe, as I used to do it, the ends are so sharp that there's no useful volume there. It took me about 25 years, averaging about one design of this type per year, to arrive at this conclusion. Having got that far, I thought that if a parallel mid-body was good, perhaps a wasp-waisted shape would be better, but when I designed a vessel that way, the owner took fright and abandoned the project, so I haven't had a chance to try it yet."
>
> Dead towed fish, and dolphins - Super/subsonic aeroplane wingroots - Soth Pacific Kirribati proa hull "dimples", etc:
>
>http://harmenhielkema.blogspot.com/2009/04/hull-asymmetry.html
>
> Re speed:http://groups.yahoo.com/group/proa_file/message/23634
>
> Kirribatis got it empirically. Recall the story of the traditional Carribean canoe forefoot and hulls like Cartopper? Phil seems to have gotten to an understanding of nature's properties, first again, independently, via thought and fantastic abilities of observation, imagination, and vision.
>
> Graeme
>
--- Inbolger@yahoogroups.com, "graeme19121984" <graeme19121984@...> wrote:
>
> From 'QUEST' (Chapter 18, 30-ODD):
>
> "I'd finally awakened to the conclusion that keels like this one give a much better distribution of displacement if they have parallel sides for most of their length, with the fairing just at the ends. If it's faired in a smooth sweep from end to end, like a canoe, as I used to do it, the ends are so sharp that there's no useful volume there. It took me about 25 years, averaging about one design of this type per year, to arrive at this conclusion. Having got that far, I thought that if a parallel mid-body was good, perhaps a wasp-waisted shape would be better, but when I designed a vessel that way, the owner took fright and abandoned the project, so I haven't had a chance to try it yet."
>
> Dead towed fish, and dolphins - Super/subsonic aeroplane wingroots - Soth Pacific Kirribati proa hull "dimples", etc:
>
>http://harmenhielkema.blogspot.com/2009/04/hull-asymmetry.html
>
> Re speed:http://groups.yahoo.com/group/proa_file/message/23634
>
> Kirribatis got it empirically. Recall the story of the traditional Carribean canoe forefoot and hulls like Cartopper? Phil seems to have gotten to an understanding of nature's properties, first again, independently, via thought and fantastic abilities of observation, imagination, and vision.
>
> Graeme
>
Graeme,
I read in the distant past that on aircraft, the coke bottle shape was done so that the aircraft would have a more constant cross sectional area. Slice down vertically across the aircraft and measure the area, first near the nose then moving back then through the winged portion of the aircraft. The wings add area therefore the body is reduced in that area to maintain a constant. I'm not sure but this might only be an issue for supersonic speeds.
I also recall something about dolphins or sharks doing something to their skin to reduce friction. It might have been rippling or something like that.
If this is all just silly talk press the delete button, I have not been following this thread very closely.
Sincerely,
Gene T.
On 23 Sep, 2009, at 6:42 PM, graeme19121984 wrote:
> I meant to ask the group a few questions about this, but was in a rush yeterday. So:
As _30-Odd Boats_ was published in 1982, 27 years ago, and Phil had been proceeding on this line of development for around 25 years up to then (p.123), did any designs with the next developmental progressions of a wasp-waist 'veed' sponson get built? How'd they go?
Would the effects of wasp-waisting (or "dimpling") transfer to a box-keel sponson? And that under a sharpie type?
How does wasp-waisting work better to shift displacement to the ends and grant higher speed? I can immediately see how the parallel sided sponson cancels or reduces the "suck-down" Bernouli effect amidships of a typically swelling hull shape, but how does introducing a convex curve to the sponson amidships improve things over the straight and parallel sided? Either curve means a longer flow path, means higher flow velocity in way of the curve, means lower pressure there, means sinking lower, means bigger wave-making, means slower, doesn't it? What else is at play that I don't see?
Graeme
-.
From 'QUEST' (Chapter 18, 30-ODD):
"I'd finally awakened to the conclusion that keels like this one give a much better distribution of displacement if they have parallel sides for most of their length, with the fairing just at the ends. If it's faired in a smooth sweep from end to end, like a canoe, as I used to do it, the ends are so sharp that there's no useful volume there. It took me about 25 years, averaging about one design of this type per year, to arrive at this conclusion. Having got that far, I thought that if a parallel mid-body was good, perhaps a wasp-waisted shape would be better, but when I designed a vessel that way, the owner took fright and abandoned the project, so I haven't had a chance to try it yet."
Dead towed fish, and dolphins - Super/subsonic aeroplane wingroots - Soth Pacific Kirribati proa hull "dimples", etc:
http://harmenhielkema.blogspot.com/2009/04/hull-asymmetry.html
Re speed:http://groups.yahoo.com/group/proa_file/message/23634
Kirribatis got it empirically. Recall the story of the traditional Carribean canoe forefoot and hulls like Cartopper? Phil seems to have gotten to an understanding of nature's properties, first again, independently, via thought and fantastic abilities of observation, imagination, and vision.
Graeme
"I'd finally awakened to the conclusion that keels like this one give a much better distribution of displacement if they have parallel sides for most of their length, with the fairing just at the ends. If it's faired in a smooth sweep from end to end, like a canoe, as I used to do it, the ends are so sharp that there's no useful volume there. It took me about 25 years, averaging about one design of this type per year, to arrive at this conclusion. Having got that far, I thought that if a parallel mid-body was good, perhaps a wasp-waisted shape would be better, but when I designed a vessel that way, the owner took fright and abandoned the project, so I haven't had a chance to try it yet."
Dead towed fish, and dolphins - Super/subsonic aeroplane wingroots - Soth Pacific Kirribati proa hull "dimples", etc:
http://harmenhielkema.blogspot.com/2009/04/hull-asymmetry.html
Re speed:http://groups.yahoo.com/group/proa_file/message/23634
Kirribatis got it empirically. Recall the story of the traditional Carribean canoe forefoot and hulls like Cartopper? Phil seems to have gotten to an understanding of nature's properties, first again, independently, via thought and fantastic abilities of observation, imagination, and vision.
Graeme