Re: does water flow around or under boat hulls?

On the other hand if upright and deep bellied, then Bernouli will see the water flow under to the region of higher speed, lower pressure. Therefore note how, for even the light displacement flat-bottomed, sharp-bowed, chined boats eg from CWS through Cj and JB to Jinni, double-ended, flared or plumb sided, in the bodyplan the chine line bisects the angle between bottom and topsides from somewhere around midships, and sometimes thence all the way aft. This is the section of most/all of the swelling displacement in proper trim (as someone earlier noted PCB typically placed COB approx 60% aft...) and so has relatively higher water flow speeds. In proper trim the low bows of these boats are just above the load waterline but gain much clearance with heeling. Nevertheless the boats float/sail mostly on those immersed equally curved sections much further aft. Bernouli still sucks there, but more equally, so helping to minimise cross chine flow. The features are apparent in numerous boats drawn by PCB's mentor, Chapelle. If trimmed bow down, cross chine flow near their flat, sharp bow creates high drag eddies underneath which not only slow, but have the moment to turn the boat and induce added high drag from the compensating rudder. The cross chine flow induced drag at such a bow is much worse in waves as the verticle movement increases the relatve water flow speed amplifying the issue. PCB likened such a bow, any immersed narrow bow, to sailing a wineglass sterned boat flat-out backwards.

--- Inbolger@yahoogroups.com, "Peter" <pvanderwaart@...> wrote:
>
>
> > I think Phil realized water flows under the hull.
>
> Yes. In the discussion quoted, he is only interested in the flow over the chines. Of course, it's great if the water is neatly divided by the chine, but that can't be arranged all the time. In his view, it was important that the flow be from under the boat to the side as much as possible.
>
> Water being incompressible, it's pretty clear that water is going to be pushed to the side, somehow, somewhere.
>

> water flows under the hull, not around the hull.

It's relative of course. Being massive, the water stays more or less still.

It moves briefly out of the way, and then returns to position, as the
hull passes through the water.

On Sat, Jan 1, 2011 at 7:30 PM,Susanne@...
<philbolger@...> wrote:

> There is one more most serious project here in town that depends on this office for success but should also (at last) result in reasonably serious fiscal returns. I'll will report when it is on solid ground.

Best wishes right back at you Susanne!

Looking in my mailbox daily for the MAIB AS-34 report.

Hmmm, intriguing hint at a "most serious project". Guessing now, is
it a sustainable fisheries boat yard located on Gloucester Harbor?

--- Inbolger@yahoogroups.com, "Susanne@..." <philbolger@...> wrote:

>
> This message seems to gotten lost in YAHOO world somehow.
> So I re-post it some 11 hours later:
>
> "Good Morning on this first day of 2011. I wish you all a good year.
>
> I would like to thank you for your continuing interest in Phil's and our work.
> I hope that the re-establishment of the monthly Design-column in MAIB keeps feeding your curiosity and engagement in our thinking on boats, how to use them, and where to build them. Note this month's feature on the preliminary design of "AS-34". Next month will be an update from the world of fisheries-policy and the working waterfront of Gloucester, essentially a summary of 2 projects of 2010 that I faced myself devoting serious time to, even though I already had an urgent agenda to tend to both in private matters and business, primarily of course securing and enhancing the legacy of Phil Bolger. One motivating factor in the constructive engagement of these two issues was the further broadening of relative relevance of Phil Bolger's thinking both on local level and in the discourse amongst high-level experts.
>
> As Bruce Hallman alerted you to already, Phil Bolger & Friends was invited late February '10 to give a presentation at the first international conference on "Energy Use in Fisheries" in Seattle, Nov. 14-17,'10, sponsored by NOAA (National Oceanographic and Atmospheric Administration) - a branch of the US government, the WORLD BANK and the UN-FAO (U.N. Fisheries and Agriculture Organization). Experts from 18 nations offered perspectives, with me amongst them (quite unexpectedly). MAIB will feature my report on it. It was and remains gratifying indeed to put Phil's and my work into that forum of discussion. That high-level recognition of the fundamental legitimacy of our perspective should contribute to the likelihood of at last getting craft built and tested across 4-seasons.
>
> The other project is directly related to the viability of this Port and its working and pleasure-fleets as we see $4/gal looming on the horizon. When we first raised the issue of accelerating fuel-cost in 2002-03 crude oil was around the low-20s per barrel. Now it has gone past $90 while many of us are still mired in the Great Recession. JP MORGAN speculates about $120 by 2011-12. We've got to be prepared for significantly higher liquid energy-cost in whatever area of life and work we can do something about.
>
> For March MAIB there will be another design feature.
>
>
> I want to thank the 'keepers' of this Forum and its many steady and casual contributors. In no particular order and addressing you all, I want to thank for instance Bruce Hallman for his efforts to put the 2-D line-art work into more appealing yet visuals, Long for the calender (he sent me one) with beautiful photos not in this archive, Massimo for the stirring video and reports on his IDAHO-project (I linked the YouTube footage to others), and the various authors of key-threads on small and large technical and functional issues along with the many progress-reports and photos on on-going and completed boat-building projects.
>
> During the dark year+ after Phil's death, I did and do draw sustenance from quietly reading your discussions. And I know I should have added to them more than I did. But I am still metering my energies for various daily demands restructuring this existence without my love, mentor, co-conspirator, companion. I constantly miss his presence and find myself often in need of 'the other hand' which is no more. So I draw energy and satisfaction from this Forum, major events (for me) such as Seattle and the knowledge that we did together and now I do try to address issues that seemed to us in need of tending, despite at times fiscal and emotional expenditures not agreed to by our CPA or always supportable by our emotional balance.
>
> There is one more most serious project here in town that depends on this office for success but should also (at last) result in reasonably serious fiscal returns. I'll will report when it is on solid ground.
>
> May this New Year present us all with opportunities and successes, health and balance in our lives, and perhaps a chance to add to the serious and joyful progress in our families and communities.
>
> Susanne Altenburger
> Phil Bolger&Friends, Inc."
>

Happy New Year to you, Susanne. Best of luck in the coming year. Your recent article in MAIB, on the Matsue Traveler Study, was a great insight into how a design is developed. Also thought the resulting design would be a great cruiser on any ocean.
Best wishes, Walter Baron

I like the idea of a removable cabin. My initial thoughts were to thicken the bottom from 3/8 to 1/2 or even 3/4 inch which would do away with the bottom stringers (except for a skeg). I thought those stringers hurt rowing, and the thicker bottom would put weight where it's needed. The hull sides would be reduced from 3/8 to 1/4 but the gunnel strips would be doubled (or maybe tripled) instead of a single layer. That in turn might allow a temporary instead of permanent center frame, would free up the interior. The deck would extend back to the mast and the raised birdwatcher cabin would be only aft of the mast to save weight. The leeboard would have to be pivoting instead of fixed because of Florida's abundant shallow water and it would be impossible to get at a fixed one from inside the cabin. An internal off-centerboard a la birdwatcher might be an alternative, but the Zephyr interior might be too narrow to make that practical. If the raised cabin could be broken down and carried aboard for short intervals, then the boat could probably be rowed at least short disances in strong winds, such as bucking the breeze in some of Florida Bay's narrow channels. Hopefully it could keep the original double reefable lateen rig with the same mast, but that rig might be too low for the cabin. A very intriguing concept.

Gary

--- Inbolger@yahoogroups.com, "Susanne@..." <philbolger@...> wrote:
>
> I'd just follow the BIRDWATCHER-approach, or add a shorter version stopping at fore and aft decks. Sitting headroom on a cushion will define your house-height. This will add weight to a very light hull. So I'd make it like a pick-up truck cab, bolted on to the hull-structure for easy changing of the mind - or just day-sailing versus cruising. Two port and starboard half-pieces should be easy. Based on 12-foot or just 8-foot length. Beyond paper-trials, without glass-investment, just sailing with that frame might reveal ergonomics not anticipated for modest up-front cost. Looking at the pointed-ends sharpie hulls between >20' ZEPHYR and 31' NAVEL JELLY there might be a sweet combination for a 'Challenge'-capable cruiser for little money, light weight but long waterline and ample tandem sleeping space for a 2-some crew.
> ----- Original Message -----
> From: gary
> To:bolger@yahoogroups.com
> Sent: Sunday, January 02, 2011 12:26 AM
> Subject: [bolger] Re: (Lost) New Years Greetings
>
>
>
> Happy New Year, Susanne. Great to hear from you as always.
>
> I really enjoyed the writeup of the AS34 in MAIB, and am looking forward to the promised followup of the AS39.
>
> Planned future projects include an expedition version of a June Bug and building another lengthened version of the "Cartoon 40" catboat, but with a Birdwatcher-type cabin. And if you've ever got the time, I'd like to pick your brain about the suggestion you once made about adding a Birdwatcher cabin to a Zephyr. That could be a fascinating minimal expedition/beachcruising craft.
>
> The reports from February symposium should be fascinating -- we seem to be heading to an inevitable and permanent state of high gas prices and it will be interesting to see if we've learned anything . . .
>
> Gary Blankenship
>

I'd just follow the BIRDWATCHER-approach, or add a shorter version stopping at fore and aft decks. Sitting headroom on a cushion will define your house-height. This will add weight to a very light hull. So I'd make it like a pick-up truck cab, bolted on to the hull-structure for easy changing of the mind - or just day-sailing versus cruising. Two port and starboard half-pieces should be easy. Based on 12-foot or just 8-foot length. Beyond paper-trials, without glass-investment, just sailing with that frame might reveal ergonomics not anticipated for modest up-front cost. Looking at the pointed-ends sharpie hulls between >20' ZEPHYR and 31' NAVEL JELLY there might be a sweet combination for a 'Challenge'-capable cruiser for little money, light weight but long waterline and ample tandem sleeping space for a 2-some crew.

----- Original Message -----
From:gary
To:bolger@yahoogroups.com
Sent:Sunday, January 02, 2011 12:26 AM
Subject:[bolger] Re: (Lost) New Years Greetings

Happy New Year, Susanne. Great to hear from you as always.

I really enjoyed the writeup of the AS34 in MAIB, and am looking forward to the promised followup of the AS39.

Planned future projects include an expedition version of a June Bug and building another lengthened version of the "Cartoon 40" catboat, but with a Birdwatcher-type cabin. And if you've ever got the time, I'd like to pick your brain about the suggestion you once made about adding a Birdwatcher cabin to a Zephyr. That could be a fascinating minimal expedition/beachcruising craft.

The reports from February symposium should be fascinating -- we seem to be heading to an inevitable and permanent state of high gas prices and it will be interesting to see if we've learned anything . . .

Gary Blankenship

--- Inbolger@yahoogroups.com, "Susanne@..." <philbolger@...> wrote:
>
> This message seems to gotten lost in YAHOO world somehow.
> So I re-post it some 11 hours later:
>
> "Good Morning on this first day of 2011. I wish you all a good year.
>
> I would like to thank you for your continuing interest in Phil's and our work.
> I hope that the re-establishment of the monthly Design-column in MAIB keeps feeding your curiosity and engagement in our thinking on boats, how to use them, and where to build them. Note this month's feature on the preliminary design of "AS-34". Next month will be an update from the world of fisheries-policy and the working waterfront of Gloucester, essentially a summary of 2 projects of 2010 that I faced myself devoting serious time to, even though I already had an urgent agenda to tend to both in private matters and business, primarily of course securing and enhancing the legacy of Phil Bolger. One motivating factor in the constructive engagement of these two issues was the further broadening of relative relevance of Phil Bolger's thinking both on local level and in the discourse amongst high-level experts.
>
> As Bruce Hallman alerted you to already, Phil Bolger & Friends was invited late February '10 to give a presentation at the first international conference on "Energy Use in Fisheries" in Seattle, Nov. 14-17,'10, sponsored by NOAA (National Oceanographic and Atmospheric Administration) - a branch of the US government, the WORLD BANK and the UN-FAO (U.N. Fisheries and Agriculture Organization). Experts from 18 nations offered perspectives, with me amongst them (quite unexpectedly). MAIB will feature my report on it. It was and remains gratifying indeed to put Phil's and my work into that forum of discussion. That high-level recognition of the fundamental legitimacy of our perspective should contribute to the likelihood of at last getting craft built and tested across 4-seasons.
>
> The other project is directly related to the viability of this Port and its working and pleasure-fleets as we see $4/gal looming on the horizon. When we first raised the issue of accelerating fuel-cost in 2002-03 crude oil was around the low-20s per barrel. Now it has gone past $90 while many of us are still mired in the Great Recession. JP MORGAN speculates about $120 by 2011-12. We've got to be prepared for significantly higher liquid energy-cost in whatever area of life and work we can do something about.
>
> For March MAIB there will be another design feature.
>
>
> I want to thank the 'keepers' of this Forum and its many steady and casual contributors. In no particular order and addressing you all, I want to thank for instance Bruce Hallman for his efforts to put the 2-D line-art work into more appealing yet visuals, Long for the calender (he sent me one) with beautiful photos not in this archive, Massimo for the stirring video and reports on his IDAHO-project (I linked the YouTube footage to others), and the various authors of key-threads on small and large technical and functional issues along with the many progress-reports and photos on on-going and completed boat-building projects.
>
> During the dark year+ after Phil's death, I did and do draw sustenance from quietly reading your discussions. And I know I should have added to them more than I did. But I am still metering my energies for various daily demands restructuring this existence without my love, mentor, co-conspirator, companion. I constantly miss his presence and find myself often in need of 'the other hand' which is no more. So I draw energy and satisfaction from this Forum, major events (for me) such as Seattle and the knowledge that we did together and now I do try to address issues that seemed to us in need of tending, despite at times fiscal and emotional expenditures not agreed to by our CPA or always supportable by our emotional balance.
>
> There is one more most serious project here in town that depends on this office for success but should also (at last) result in reasonably serious fiscal returns. I'll will report when it is on solid ground.
>
> May this New Year present us all with opportunities and successes, health and balance in our lives, and perhaps a chance to add to the serious and joyful progress in our families and communities.
>
> Susanne Altenburger
> Phil Bolger&Friends, Inc."
>

Simple answer: The answer differs with displacement and planing boats. A displacement boat moves through the water causing the water to flow around the hull. Planing boats rise up more or less on top of the water and so the water passes mostly underneath when planing.

David

--- Inbolger@yahoogroups.com, "jhess314" <j.hess@...> wrote:
>
> First, a MAJOR caveat -- I am NOT a naval engineer. The following is offered only for the sake of discussion:
>
> Many boat designers, Phil Bolger included, seem to think that water flows around a hull more or less parallel to the waterlines. So in Bolger's description of water flow around a sharpie hull, which Bruce posted below, the water that comes in contact with the bow of the boat is thrown off to the sides.
>
> However, some boat designers claim to have extensive empirical evidence which shows that most of the water flow goes under the hull, not around the hull, and so mostly follows the buttock lines of a hull.
>
> Following is a link to a rather long discussion about how water flows around the hull of canoes and kayaks. The relevant posts are those made by John Winters. John Winters is a well known canoe and kayak designer. However, he refers to naval design literature to support his point that most water flows under the hull, not around the hull.
>
>http://www.paddlewise.net/topics/boatdesign/pro-conswede.html
>
> Peace and Good Will towards (this) Man :)
> John
>
> --- Inbolger@yahoogroups.com, Bruce Hallman <hallman@> wrote:
> >
> > I just stumbled on this text written by PCB in 1984 speaking about the
> > classic sharpie "Presto".
> > It is on-topic I think with the recent discussion of hard chine side curvature.
> >
> >
> > SBJ #35, March 1984 PCB:
> >
> > First about sharpies: A sharp bowed boat
> > has to have more curve in her sides in
> > plan view than she does in her bottom
> > profile. If the stem cuts the water, the
> > sides push the water out more than the
> > bottom pushes it down. This builds up
> > more water pressure against the sides
> > than it does against the bottom. The
> > water runs from the high-pressure area
> > to the low-pressure area; if it has to get
> > around the sharp corner of the chine as
> > it does so, it breaks into great turbulent
> > eddies - producing high drag and
> > sometimes wild steering. These eddies
> > reduce the pressure under the bottom
> > still more; the bow tends to drop and
> > you get worse eddies - and a vicious
> > cycle. This is why sharpies are poor
> > sailors in a chop, especially when
> > there's more sea than wind.
> > The wider the sharpie is for her
> > length, the blunter her bow angle has
> > to be. Blunter bows result -in a greater
> > difference between the sides and the
> > bottom and so, more turbulence. To
> > minimize this effect"a big sharpie has
> > to be long for her breadth. A well designed
> > sharpie carries her bottom high forward,
> > to meet the water mostly
> > with her bottom. But when she heels,
> > the forward chine still digs in. A very
> > small sharpie, that can be sailed flat by
> > using live ballast, can be wider for her
> > length. Large boat or small, the high,
> > sloping bottom forward is horribly
> > noisy and bumpy at anchor and anytime
> > the boat isn't sharply heeled.
> >
>

Happy New Year, Susanne. Great to hear from you as always.

I really enjoyed the writeup of the AS34 in MAIB, and am looking forward to the promised followup of the AS39.

Planned future projects include an expedition version of a June Bug and building another lengthened version of the "Cartoon 40" catboat, but with a Birdwatcher-type cabin. And if you've ever got the time, I'd like to pick your brain about the suggestion you once made about adding a Birdwatcher cabin to a Zephyr. That could be a fascinating minimal expedition/beachcruising craft.

The reports from February symposium should be fascinating -- we seem to be heading to an inevitable and permanent state of high gas prices and it will be interesting to see if we've learned anything . . .

Gary Blankenship

--- Inbolger@yahoogroups.com, "Susanne@..." <philbolger@...> wrote:
>
> This message seems to gotten lost in YAHOO world somehow.
> So I re-post it some 11 hours later:
>
> "Good Morning on this first day of 2011. I wish you all a good year.
>
> I would like to thank you for your continuing interest in Phil's and our work.
> I hope that the re-establishment of the monthly Design-column in MAIB keeps feeding your curiosity and engagement in our thinking on boats, how to use them, and where to build them. Note this month's feature on the preliminary design of "AS-34". Next month will be an update from the world of fisheries-policy and the working waterfront of Gloucester, essentially a summary of 2 projects of 2010 that I faced myself devoting serious time to, even though I already had an urgent agenda to tend to both in private matters and business, primarily of course securing and enhancing the legacy of Phil Bolger. One motivating factor in the constructive engagement of these two issues was the further broadening of relative relevance of Phil Bolger's thinking both on local level and in the discourse amongst high-level experts.
>
> As Bruce Hallman alerted you to already, Phil Bolger & Friends was invited late February '10 to give a presentation at the first international conference on "Energy Use in Fisheries" in Seattle, Nov. 14-17,'10, sponsored by NOAA (National Oceanographic and Atmospheric Administration) - a branch of the US government, the WORLD BANK and the UN-FAO (U.N. Fisheries and Agriculture Organization). Experts from 18 nations offered perspectives, with me amongst them (quite unexpectedly). MAIB will feature my report on it. It was and remains gratifying indeed to put Phil's and my work into that forum of discussion. That high-level recognition of the fundamental legitimacy of our perspective should contribute to the likelihood of at last getting craft built and tested across 4-seasons.
>
> The other project is directly related to the viability of this Port and its working and pleasure-fleets as we see $4/gal looming on the horizon. When we first raised the issue of accelerating fuel-cost in 2002-03 crude oil was around the low-20s per barrel. Now it has gone past $90 while many of us are still mired in the Great Recession. JP MORGAN speculates about $120 by 2011-12. We've got to be prepared for significantly higher liquid energy-cost in whatever area of life and work we can do something about.
>
> For March MAIB there will be another design feature.
>
>
> I want to thank the 'keepers' of this Forum and its many steady and casual contributors. In no particular order and addressing you all, I want to thank for instance Bruce Hallman for his efforts to put the 2-D line-art work into more appealing yet visuals, Long for the calender (he sent me one) with beautiful photos not in this archive, Massimo for the stirring video and reports on his IDAHO-project (I linked the YouTube footage to others), and the various authors of key-threads on small and large technical and functional issues along with the many progress-reports and photos on on-going and completed boat-building projects.
>
> During the dark year+ after Phil's death, I did and do draw sustenance from quietly reading your discussions. And I know I should have added to them more than I did. But I am still metering my energies for various daily demands restructuring this existence without my love, mentor, co-conspirator, companion. I constantly miss his presence and find myself often in need of 'the other hand' which is no more. So I draw energy and satisfaction from this Forum, major events (for me) such as Seattle and the knowledge that we did together and now I do try to address issues that seemed to us in need of tending, despite at times fiscal and emotional expenditures not agreed to by our CPA or always supportable by our emotional balance.
>
> There is one more most serious project here in town that depends on this office for success but should also (at last) result in reasonably serious fiscal returns. I'll will report when it is on solid ground.
>
> May this New Year present us all with opportunities and successes, health and balance in our lives, and perhaps a chance to add to the serious and joyful progress in our families and communities.
>
> Susanne Altenburger
> Phil Bolger&Friends, Inc."
>

Well said, Suzanne, thanks for the update, and best New Year's Wishes to you and Phil's continued legacy.
And I trust this confirms that Yahoo is still in s.o.p. mode,
Dave

--- Inbolger@yahoogroups.com, "Susanne@..." <philbolger@...> wrote:
>
> This message seems to gotten lost in YAHOO world somehow.
> So I re-post it some 11 hours later:
>
> "Good Morning on this first day of 2011. I wish you all a good year.
>
> I would like to thank you for your continuing interest in Phil's and our work.
> I hope that the re-establishment of the monthly Design-column in MAIB keeps feeding your curiosity and engagement in our thinking on boats, how to use them, and where to build them. Note this month's feature on the preliminary design of "AS-34". Next month will be an update from the world of fisheries-policy and the working waterfront of Gloucester, essentially a summary of 2 projects of 2010 that I faced myself devoting serious time to, even though I already had an urgent agenda to tend to both in private matters and business, primarily of course securing and enhancing the legacy of Phil Bolger. One motivating factor in the constructive engagement of these two issues was the further broadening of relative relevance of Phil Bolger's thinking both on local level and in the discourse amongst high-level experts.
>
> As Bruce Hallman alerted you to already, Phil Bolger & Friends was invited late February '10 to give a presentation at the first international conference on "Energy Use in Fisheries" in Seattle, Nov. 14-17,'10, sponsored by NOAA (National Oceanographic and Atmospheric Administration) - a branch of the US government, the WORLD BANK and the UN-FAO (U.N. Fisheries and Agriculture Organization). Experts from 18 nations offered perspectives, with me amongst them (quite unexpectedly). MAIB will feature my report on it. It was and remains gratifying indeed to put Phil's and my work into that forum of discussion. That high-level recognition of the fundamental legitimacy of our perspective should contribute to the likelihood of at last getting craft built and tested across 4-seasons.
>
> The other project is directly related to the viability of this Port and its working and pleasure-fleets as we see $4/gal looming on the horizon. When we first raised the issue of accelerating fuel-cost in 2002-03 crude oil was around the low-20s per barrel. Now it has gone past $90 while many of us are still mired in the Great Recession. JP MORGAN speculates about $120 by 2011-12. We've got to be prepared for significantly higher liquid energy-cost in whatever area of life and work we can do something about.
>
> For March MAIB there will be another design feature.
>
>
> I want to thank the 'keepers' of this Forum and its many steady and casual contributors. In no particular order and addressing you all, I want to thank for instance Bruce Hallman for his efforts to put the 2-D line-art work into more appealing yet visuals, Long for the calender (he sent me one) with beautiful photos not in this archive, Massimo for the stirring video and reports on his IDAHO-project (I linked the YouTube footage to others), and the various authors of key-threads on small and large technical and functional issues along with the many progress-reports and photos on on-going and completed boat-building projects.
>
> During the dark year+ after Phil's death, I did and do draw sustenance from quietly reading your discussions. And I know I should have added to them more than I did. But I am still metering my energies for various daily demands restructuring this existence without my love, mentor, co-conspirator, companion. I constantly miss his presence and find myself often in need of 'the other hand' which is no more. So I draw energy and satisfaction from this Forum, major events (for me) such as Seattle and the knowledge that we did together and now I do try to address issues that seemed to us in need of tending, despite at times fiscal and emotional expenditures not agreed to by our CPA or always supportable by our emotional balance.
>
> There is one more most serious project here in town that depends on this office for success but should also (at last) result in reasonably serious fiscal returns. I'll will report when it is on solid ground.
>
> May this New Year present us all with opportunities and successes, health and balance in our lives, and perhaps a chance to add to the serious and joyful progress in our families and communities.
>
> Susanne Altenburger
> Phil Bolger&Friends, Inc."
>

This message seems to gotten lost in YAHOO world somehow.

So I re-post it some 11 hours later:

"Good Morning on this first day of 2011. I wish you all a good year.

I would like to thank you for your continuing interest in Phil's and our work.

I hope that the re-establishment of the monthly Design-column in MAIB keeps feeding your curiosity and engagement in our thinking on boats, how to use them, and where to build them. Note this month's feature on the preliminary design of "AS-34". Next month will be an update from the world of fisheries-policy and the working waterfront of Gloucester, essentially a summary of 2 projects of 2010 that I faced myself devoting serious time to, even though I already had an urgent agenda to tend to both in private matters and business, primarily of course securing and enhancing the legacy of Phil Bolger. One motivating factor in the constructive engagement of these two issues was the further broadening of relative relevance of Phil Bolger's thinking both on local level and in the discourse amongst high-level experts.

As Bruce Hallman alerted you to already, Phil Bolger & Friends was invited late February'10 to give a presentation at the first international conference on "Energy Use in Fisheries" in Seattle, Nov. 14-17,'10, sponsored by NOAA (National Oceanographic and Atmospheric Administration) - a branch of the US government, the WORLD BANK and the UN-FAO (U.N. Fisheries and Agriculture Organization). Experts from 18 nations offered perspectives, with me amongst them (quite unexpectedly). MAIB will feature my report on it. It was and remains gratifying indeed to put Phil's and my work into that forum of discussion. That high-level recognition of the fundamental legitimacy of our perspective should contribute to the likelihood of at last getting craft built and tested across 4-seasons.

The other project is directly related to the viability of this Port and its working and pleasure-fleets as we see $4/gal looming on the horizon. When we first raised the issue of accelerating fuel-cost in 2002-03 crude oil was around the low-20s per barrel. Now it has gone past $90 while many of us are still mired in the Great Recession. JP MORGAN speculates about $120 by 2011-12. We've got to be prepared for significantly higher liquid energy-cost in whatever area of life and work we can do something about.

For March MAIB there will be another design feature.

I want to thank the 'keepers' of this Forum and its many steady and casual contributors. In no particular order and addressing you all, I want to thank for instance Bruce Hallman for his efforts to put the 2-D line-art work into more appealing yet visuals, Long for the calender (he sent me one) with beautiful photos not in this archive, Massimo for the stirring video and reports on his IDAHO-project (I linked the YouTube footage to others), and the various authors of key-threads on small and large technical and functional issues along with the many progress-reports and photos on on-going and completed boat-building projects.

During the dark year+ after Phil's death, I did and do draw sustenance from quietly reading your discussions. And I know I should have added to them more than I did. But I am still metering my energies for various daily demands restructuring this existence without my love, mentor, co-conspirator, companion. I constantly miss his presence and find myself often in need of 'the other hand' which is no more. So I draw energy and satisfaction from this Forum, major events (for me) such as Seattle and the knowledge that we did together and now I do try to address issues that seemed to us in need of tending, despite at times fiscal and emotional expenditures not agreed to by our CPA or always supportable by our emotional balance.

There is one more most serious project here in town that depends on this office for success but should also (at last) result in reasonably serious fiscal returns. I'll will report when it is on solid ground.

May this New Year present us all with opportunities and successes, health and balance in our lives, and perhaps a chance to add to the serious and joyful progress in our families and communities.

Susanne Altenburger

Phil Bolger&Friends, Inc."

No offense, Lance, but your insistence over a few different forums (Woodenboat and this one) that Black Skimmer is slow is starting to make me a little nuts... It's not that it matters what you believe, it's that you keep repeating it as if it's just a fact, and I feel a little protective of Bolger.

The boat is KNOWN for not being slow! Mike O'Brien I believe will vouch for the sailing qualities of the boat, and so will a lot of other people. Check out the comments from the guy who had Nexus build him one. His boat is a performer. Mine, built by me, sails built by me as well, as I've attested in this forum and woodenboat, outsailed a Soling being competently sailed and with decent looking sails, to windward in smooth water one day. I also used to race it in the local handicap races, and while it was no bullet to windward "outside" in the big water, it was very capable and competitive on a reach with any boat near its size, and downwind was just plain quick, passing 40 footers with ease. Please--just at least put in a disclaimer or something--that YOUR skimmer may be slow, others definitely don't agree. There are so many factors in these boats--the sail cut among other things, leeboard alignment, bottom cleanliness, and the guy at the helm, even the mast design on Skimmer is detailed down to the last 1/16 of an inch and I believe that radical taper really has something to do with the ability of the boat to stand up. So... it may be a crude shape, but it's a very subtle boat all in all.

thanks you for listening. Back to regularly sheduled, non-controversial discussions

--- Inbolger@yahoogroups.com, "lancefgunderson" <lancefgunderson@...> wrote:
>
>
>
> --- Inbolger@yahoogroups.com, Bruce Hallman <hallman@> wrote:
> >
> > I just stumbled on this text written by PCB in 1984 speaking about the
> > classic sharpie "Presto".
> > It is on-topic I think with the recent discussion of hard chine side curvature.
> >
> >
> > SBJ #35, March 1984 PCB:
> >
> > First about sharpies: A sharp bowed boat
> > has to have more curve in her sides in
> > plan view than she does in her bottom
> > profile. If the stem cuts the water, the
> > sides push the water out more than the
> > bottom pushes it down. This builds up
> > more water pressure against the sides
> > than it does against the bottom. The
> > water runs from the high-pressure area
> > to the low-pressure area; if it has to get
> > around the sharp corner of the chine as
> > it does so, it breaks into great turbulent
> > eddies - producing high drag and
> > sometimes wild steering. These eddies
> > reduce the pressure under the bottom
> > still more; the bow tends to drop and
> > you get worse eddies - and a vicious
> > cycle. This is why sharpies are poor
> > sailors in a chop, especially when
> > there's more sea than wind.
> > The wider the sharpie is for her
> > length, the blunter her bow angle has
> > to be. Blunter bows result -in a greater
> > difference between the sides and the
> > bottom and so, more turbulence. To
> > minimize this effect"a big sharpie has
> > to be long for her breadth. A well designed
> > sharpie carries her bottom high forward,
> > to meet the water mostly
> > with her bottom. But when she heels,
> > the forward chine still digs in. A very
> > small sharpie, that can be sailed flat by
> > using live ballast, can be wider for her
> > length. Large boat or small, the high,
> > sloping bottom forward is horribly
> > noisy and bumpy at anchor and anytime
> > the boat isn't sharply heeled.
> >
> All of that certainly applies to the Black Skimmer, and explains why they are so slow. PCB also wrote that an experienced builder should tackle a more refined shape than the sharpie. I still like sharpies though.
>

I'm also not a naval (or any other kind of) engineer. What follows comes
from what I've read from those who are. Caution is advised.

What's being described in those comments is how the bluntness of the
sides in the bow section results in greater impact pressure than the
bottom has and, as a result, the water flows from the higher pressure
area of the sides to the lower pressure area of the bottom creating
eddies as it crosses over the sharp chine. This contributes to the "wild
steering".

Those comments are describing the flow at the bow section. From what
I've read, that's a problem not limited to traditional sharpies. Any
boat with a deep forefoot is vulnerable to having the bow dig in and
broach the boat. My uninformed take on PCB's comment here is that
traditional sharpies are more vulnerable to this than other designs and
their relatively deep forefoot is at the heart of it. Adding rocker gets
the bow away from the water and is going to be a help regardless of the
eddy situation. But the eddies make it worse by reducing the pressure at
the bottom which pulls the bow down even further. The added rocker helps
even if the "equal curves" paradigm isn't precisely followed (as it's
not on some of the "box" designs, I found).

And that's only the beginning of what's involved. Not mentioned in those
comments is that, in general, we spend more time sailing with the wind
somewhere ahead of the beam which means the boat is traveling in some
degree of yaw due to leeway. Close-hauled that may be anywhere from 3 to
10 deg, depending on the boat (less when reaching). To the extent that
we're going sideways like that, the geometry of equal curves is going
out the window--the cuves are only equal in the fore-aft direction.
Intuitively, it seems some significant amount of flow is forced down
under the boat. This is seen in photos taken of the hull in that
situation showing a large vortex being thrown off. There's definitely an
amount of vertical flow to the water around the hull.

.--- Inbolger@yahoogroups.com, Fred Schumacher <fredschum@...> wrote:

>
> On Sat, Jan 1, 2011 at 9:15 AM, jhess314 j.hess@... wrote:
>
> >
> >
> > First, a MAJOR caveat -- I am NOT a naval engineer. The following is
> > offered only for the sake of discussion:
> >
> > Many boat designers, Phil Bolger included, seem to think that water

flows

> > around a hull more or less parallel to the waterlines. So in

Bolger's

> > description of water flow around a sharpie hull, which Bruce posted

below,

> > the water that comes in contact with the bow of the boat is thrown

off to

> > the sides.
> >
> I think Phil realized water flows under the hull. He discusses it in

some of

> his writings, about water being displaced down against the

incompressible

> depths. It is why he came up with his equal curves in plan and profile
> paradigm, and why a sharpie needs to meet the water with her bottom.

If he

> thought water only flows around the hull, then there would be no need

> worry about chine eddies (i.e. vortexes). He said most sharpies steer

wildly

> because their shape forces most water around the sides, due to their

high

> beam to draft ratio. Bolger's sharpies are deep bellied.
>
> fred s.
>

> I think Phil realized water flows under the hull.

Yes. In the discussion quoted, he is only interested in the flow over the chines. Of course, it's great if the water is neatly divided by the chine, but that can't be arranged all the time. In his view, it was important that the flow be from under the boat to the side as much as possible.

Water being incompressible, it's pretty clear that water is going to be pushed to the side, somehow, somewhere.

On Sat, Jan 1, 2011 at 9:15 AM, jhess314<j.hess@...>wrote:
First, a MAJOR caveat -- I am NOT a naval engineer. The following is offered only for the sake of discussion:

Many boat designers, Phil Bolger included, seem to think that water flows around a hull more or less parallel to the waterlines. So in Bolger's description of water flow around a sharpie hull, which Bruce posted below, the water that comes in contact with the bow of the boat is thrown off to the sides.
I think Phil realized water flows under the hull. He discusses it in some of his writings, about water being displaced down against the incompressible depths. It is why he came up with his equal curves in plan and profile paradigm, and why a sharpie needs to meet the water with her bottom. If he thought water only flows around the hull, then there would be no need to worry about chine eddies (i.e. vortexes). He said most sharpies steer wildly because their shape forces most water around the sides, due to their high beam to draft ratio. Bolger's sharpies are deep bellied.
fred s.

First, a MAJOR caveat -- I am NOT a naval engineer. The following is offered only for the sake of discussion:

Many boat designers, Phil Bolger included, seem to think that water flows around a hull more or less parallel to the waterlines. So in Bolger's description of water flow around a sharpie hull, which Bruce posted below, the water that comes in contact with the bow of the boat is thrown off to the sides.

However, some boat designers claim to have extensive empirical evidence which shows that most of the water flow goes under the hull, not around the hull, and so mostly follows the buttock lines of a hull.

Following is a link to a rather long discussion about how water flows around the hull of canoes and kayaks. The relevant posts are those made by John Winters. John Winters is a well known canoe and kayak designer. However, he refers to naval design literature to support his point that most water flows under the hull, not around the hull.

http://www.paddlewise.net/topics/boatdesign/pro-conswede.html

Peace and Good Will towards (this) Man :)
John

--- Inbolger@yahoogroups.com, Bruce Hallman <hallman@...> wrote:
>
> I just stumbled on this text written by PCB in 1984 speaking about the
> classic sharpie "Presto".
> It is on-topic I think with the recent discussion of hard chine side curvature.
>
>
> SBJ #35, March 1984 PCB:
>
> First about sharpies: A sharp bowed boat
> has to have more curve in her sides in
> plan view than she does in her bottom
> profile. If the stem cuts the water, the
> sides push the water out more than the
> bottom pushes it down. This builds up
> more water pressure against the sides
> than it does against the bottom. The
> water runs from the high-pressure area
> to the low-pressure area; if it has to get
> around the sharp corner of the chine as
> it does so, it breaks into great turbulent
> eddies - producing high drag and
> sometimes wild steering. These eddies
> reduce the pressure under the bottom
> still more; the bow tends to drop and
> you get worse eddies - and a vicious
> cycle. This is why sharpies are poor
> sailors in a chop, especially when
> there's more sea than wind.
> The wider the sharpie is for her
> length, the blunter her bow angle has
> to be. Blunter bows result -in a greater
> difference between the sides and the
> bottom and so, more turbulence. To
> minimize this effect"a big sharpie has
> to be long for her breadth. A well designed
> sharpie carries her bottom high forward,
> to meet the water mostly
> with her bottom. But when she heels,
> the forward chine still digs in. A very
> small sharpie, that can be sailed flat by
> using live ballast, can be wider for her
> length. Large boat or small, the high,
> sloping bottom forward is horribly
> noisy and bumpy at anchor and anytime
> the boat isn't sharply heeled.
>

On Fri, Dec 31, 2010 at 7:52 AM, cecbell <cecbell@...> wrote:

>
>
>
> For those who don't have a collection of SBJs to reference, those exact
> comments are in BWAOM under the write-up of the Presto Cruiser.

Yes, I had forgotten. About half of the articles from Small Boat
Journal were edited or simply copied to become chapters the book
_Boats with an Open Mind_.

It is probably the case that a number of books could be edited
together from articles published post-1994 in MAIB.

For those who don't have a collection of SBJs to reference, those exact
comments are in BWAOM under the write-up of the Presto Cruiser.

--- Inbolger@yahoogroups.com, Fred Schumacher <fredschum@...> wrote:
>
> On Thu, Dec 30, 2010 at 3:51 PM, Bruce Hallman hallman@... wrote:
>
> >
> >
> > I just stumbled on this text written by PCB in 1984 speaking about
the
> > classic sharpie "Presto".
> > It is on-topic I think with the recent discussion of hard chine side
> > curvature.
> >
>
> Thanks Bruce for posting the source of Phil's musings on chine eddies.
I was
> thinking about that article when I wrote about chine eddies but
couldn't
> remember where Phil had talked about it. I have most of the old SBJs
and
> will have to look it up, but I can already picture the page in my
mind.
>
> Phil's Advanced Sharpies are a direct result of his thinking about
chine
> eddies, or hydrodynamics as a "sea of peas." Brilliant thinkers are
able to
> simplify complex problems and visualize solutions. That's Phil, the
Master
> of Parsimony. Or as William of Ockham said: "non sunt multiplicanda
entia
> praeter necessitatem."
>
> fred s.
>

On Thu, Dec 30, 2010 at 3:51 PM, Bruce Hallman<hallman@...>wrote:
I just stumbled on this text written by PCB in 1984 speaking about the
classic sharpie "Presto".
It is on-topic I think with the recent discussion of hard chine side curvature.

Thanks Bruce for posting the source of Phil's musings on chine eddies. I was thinking about that article when I wrote about chine eddies but couldn't remember where Phil had talked about it. I have most of the old SBJs and will have to look it up, but I can already picture the page in my mind.

Phil's Advanced Sharpies are a direct result of his thinking about chine eddies, or hydrodynamics as a "sea of peas." Brilliant thinkers are able to simplify complex problems and visualize solutions. That's Phil, the Master of Parsimony. Or as William of Ockham said: "non sunt multiplicanda entia praeter necessitatem."

fred s.

--- Inbolger@yahoogroups.com, Bruce Hallman <hallman@...> wrote:

>
> I just stumbled on this text written by PCB in 1984 speaking about the
> classic sharpie "Presto".
> It is on-topic I think with the recent discussion of hard chine side curvature.
>
>
> SBJ #35, March 1984 PCB:
>
> First about sharpies: A sharp bowed boat
> has to have more curve in her sides in
> plan view than she does in her bottom
> profile. If the stem cuts the water, the
> sides push the water out more than the
> bottom pushes it down. This builds up
> more water pressure against the sides
> than it does against the bottom. The
> water runs from the high-pressure area
> to the low-pressure area; if it has to get
> around the sharp corner of the chine as
> it does so, it breaks into great turbulent
> eddies - producing high drag and
> sometimes wild steering. These eddies
> reduce the pressure under the bottom
> still more; the bow tends to drop and
> you get worse eddies - and a vicious
> cycle. This is why sharpies are poor
> sailors in a chop, especially when
> there's more sea than wind.
> The wider the sharpie is for her
> length, the blunter her bow angle has
> to be. Blunter bows result -in a greater
> difference between the sides and the
> bottom and so, more turbulence. To
> minimize this effect"a big sharpie has
> to be long for her breadth. A well designed
> sharpie carries her bottom high forward,
> to meet the water mostly
> with her bottom. But when she heels,
> the forward chine still digs in. A very
> small sharpie, that can be sailed flat by
> using live ballast, can be wider for her
> length. Large boat or small, the high,
> sloping bottom forward is horribly
> noisy and bumpy at anchor and anytime
> the boat isn't sharply heeled.
>

All of that certainly applies to the Black Skimmer, and explains why they are so slow. PCB also wrote that an experienced builder should tackle a more refined shape than the sharpie. I still like sharpies though.

I just stumbled on this text written by PCB in 1984 speaking about the
classic sharpie "Presto".
It is on-topic I think with the recent discussion of hard chine side curvature.

SBJ #35, March 1984 PCB:

First about sharpies: A sharp bowed boat
has to have more curve in her sides in
plan view than she does in her bottom
profile. If the stem cuts the water, the
sides push the water out more than the
bottom pushes it down. This builds up
more water pressure against the sides
than it does against the bottom. The
water runs from the high-pressure area
to the low-pressure area; if it has to get
around the sharp corner of the chine as
it does so, it breaks into great turbulent
eddies - producing high drag and
sometimes wild steering. These eddies
reduce the pressure under the bottom
still more; the bow tends to drop and
you get worse eddies - and a vicious
cycle. This is why sharpies are poor
sailors in a chop, especially when
there's more sea than wind.
The wider the sharpie is for her
length, the blunter her bow angle has
to be. Blunter bows result -in a greater
difference between the sides and the
bottom and so, more turbulence. To
minimize this effect"a big sharpie has
to be long for her breadth. A well designed
sharpie carries her bottom high forward,
to meet the water mostly
with her bottom. But when she heels,
the forward chine still digs in. A very
small sharpie, that can be sailed flat by
using live ballast, can be wider for her
length. Large boat or small, the high,
sloping bottom forward is horribly
noisy and bumpy at anchor and anytime
the boat isn't sharply heeled.