Re: confusion,
> JM wrote an article or two on it as I recall..."One must remember that the advantage of the swept (up)(sailing)
hull is probably no real advantage since it happens at an extreme
trim that only a land lubber would accept." "I was afraid of
that. Only about 16 pounds drag at 5 knots, less again than the
sailing hull. Well, I don't believe it. What else can I
say." "Well, Bolger is right again - you have to build two real
hulls and test. Then I'll believe it." - Jim Michalak.
http://www.jimsboats.com/2007/15jul07.htm
http://www.jimsboats.com/2007/15aug07.htm
Graeme
--- Inbolger@yahoogroups.com, "graeme19121984" <graeme19121984@...> wrote:
>
>
>
>
>
>
> No need to go into just why that shape is... leave that mixed-up critic to wallow. Now, if they'd been referencing waste disposal barges that carry the stuff, & similar ...or subs, then they'd still be mixed up somewhat -- but it might be worth a try explaining it to 'em ;-D
>
> Search Jim Michalak's newsletter a year or so back. Someone built one of his larger cabined shanty/scow designs; not a particularly light boat either; and meant for small outboard power. They did not build to plan. They did what Bolger mentions for the brick stern, and reported it as being ok under sail. JM wrote an article or two on it as I recall. He analysed it in various ways (Savitsky et al, etc, Hullforms), and it more or less confounded him as the models predominantly confirmed better performance from the flat-run/square-transomed not-to-plan bottom. Conventional knowledge says it just never should!
>
> There are a number of possible factors that working jointly and seperately may allow this bottom to deliver the performance on low power. Some might be: trim, heel, WLL, water depth, prismatic form, depth to beam ratio, wetted planing surface, and PCB's (Hickman?) "hover" effect.
>
> I suspect the design envelope for these factors to work optimally is a tight one, yet a sub-optimal design may still surprise as I believe PCB mused on by his comment about the altered Brick stern increase in capacity. "Capacity" not so much in the sense of 'displacement', but also in the sense of 'capacity to perform' (here on the same light displacement), or by stretching the original envelope.
>
> Graeme
>
>
>
> --- Inbolger@yahoogroups.com, John Bell <yonderman@> wrote:
> >
> > The designer was chided "Even a turd is pointy at both ends..."
> >
> > Submerged transoms create a lot of turbulence and therefore drag. Sailboats
> > suffer a lot when there's a lot of drag. Build it as designed, or better yet
> > build a PDR!
> >
> > On Fri, Jan 1, 2010 at 9:23 PM, Christopher C. Wetherill <
> > wetherillc@> wrote:
> >
> > >
> > >
> > > I do not recall the name or the year, but there was a contender to defend
> > > the America's cup in the '70s that had a flat stern below the water line.
> > > The idea was that the effective water line was thereby longer than the
> > > actual. It failed miserably. I think it only works when the hull planes.
> > >
> > > V/R
> > > Chris
> > >
> > >
> > >
> > > Mark Albanese wrote:
> > >
> > >
> > >
> > > Morten Olesen at Boatplans.dk used to show a couple of sailboat cruisers
> > > with square sterns, though they weren't so successful that he still promotes
> > > them.
> > >
> > > It would be hard to gauge a difference in speed at Brick's scale. The
> > > regular stern is rockered so high the boat will surely feel steadier with it
> > > run back. For sailing, the regular shape is prudent, not to say traditional.
> > > For power alone or as a tiny motorsailer, straight back is sure to work.
> > >
> > > Mark
> > >
> > >
> > > On Jan 1, 2010, at 3:59 PM, Robert wrote:
> > >
> > >
> > > It is uncertain to me that if the bottom were run back to a perfectly
> > > rectangular stern(with the bottom of the transom in the water), as to
> > > whether the sailing performance of the Brick would be degraded. I agree that
> > > the capacity will be increased because of the increased wetted surface. Is
> > > he suggesting that this could be done with no degradation to the boat's
> > > sailing ability?
> > >
> > > I have never seen a sailboat where the transom sits in the water, as a
> > > fishing boat does. The aft part of the hull is always tapered upward to the
> > > transom, and the transom is out of the water. There must be a reason why.
> > > but I can't imagine why.
> > >
> > > Would someone clarify this for me? Thanks.
> > >
> > > Robert
> > > Niagara Falls, Ontario
>
No need to go into just why that shape is... leave that mixed-up critic to wallow. Now, if they'd been referencing waste disposal barges that carry the stuff, & similar ...or subs, then they'd still be mixed up somewhat -- but it might be worth a try explaining it to 'em ;-D
Search Jim Michalak's newsletter a year or so back. Someone built one of his larger cabined shanty/scow designs; not a particularly light boat either; and meant for small outboard power. They did not build to plan. They did what Bolger mentions for the brick stern, and reported it as being ok under sail. JM wrote an article or two on it as I recall. He analysed it in various ways (Savitsky et al, etc, Hullforms), and it more or less confounded him as the models predominantly confirmed better performance from the flat-run/square-transomed not-to-plan bottom. Conventional knowledge says it just never should!
There are a number of possible factors that working jointly and seperately may allow this bottom to deliver the performance on low power. Some might be: trim, heel, WLL, water depth, prismatic form, depth to beam ratio, wetted planing surface, and PCB's (Hickman?) "hover" effect.
I suspect the design envelope for these factors to work optimally is a tight one, yet a sub-optimal design may still surprise as I believe PCB mused on by his comment about the altered Brick stern increase in capacity. "Capacity" not so much in the sense of 'displacement', but also in the sense of 'capacity to perform' (here on the same light displacement), or by stretching the original envelope.
Graeme
Search Jim Michalak's newsletter a year or so back. Someone built one of his larger cabined shanty/scow designs; not a particularly light boat either; and meant for small outboard power. They did not build to plan. They did what Bolger mentions for the brick stern, and reported it as being ok under sail. JM wrote an article or two on it as I recall. He analysed it in various ways (Savitsky et al, etc, Hullforms), and it more or less confounded him as the models predominantly confirmed better performance from the flat-run/square-transomed not-to-plan bottom. Conventional knowledge says it just never should!
There are a number of possible factors that working jointly and seperately may allow this bottom to deliver the performance on low power. Some might be: trim, heel, WLL, water depth, prismatic form, depth to beam ratio, wetted planing surface, and PCB's (Hickman?) "hover" effect.
I suspect the design envelope for these factors to work optimally is a tight one, yet a sub-optimal design may still surprise as I believe PCB mused on by his comment about the altered Brick stern increase in capacity. "Capacity" not so much in the sense of 'displacement', but also in the sense of 'capacity to perform' (here on the same light displacement), or by stretching the original envelope.
Graeme
--- Inbolger@yahoogroups.com, John Bell <yonderman@...> wrote:
>
> The designer was chided "Even a turd is pointy at both ends..."
>
> Submerged transoms create a lot of turbulence and therefore drag. Sailboats
> suffer a lot when there's a lot of drag. Build it as designed, or better yet
> build a PDR!
>
> On Fri, Jan 1, 2010 at 9:23 PM, Christopher C. Wetherill <
> wetherillc@...> wrote:
>
> >
> >
> > I do not recall the name or the year, but there was a contender to defend
> > the America's cup in the '70s that had a flat stern below the water line.
> > The idea was that the effective water line was thereby longer than the
> > actual. It failed miserably. I think it only works when the hull planes.
> >
> > V/R
> > Chris
> >
> >
> >
> > Mark Albanese wrote:
> >
> >
> >
> > Morten Olesen at Boatplans.dk used to show a couple of sailboat cruisers
> > with square sterns, though they weren't so successful that he still promotes
> > them.
> >
> > It would be hard to gauge a difference in speed at Brick's scale. The
> > regular stern is rockered so high the boat will surely feel steadier with it
> > run back. For sailing, the regular shape is prudent, not to say traditional.
> > For power alone or as a tiny motorsailer, straight back is sure to work.
> >
> > Mark
> >
> >
> > On Jan 1, 2010, at 3:59 PM, Robert wrote:
> >
> >
> > It is uncertain to me that if the bottom were run back to a perfectly
> > rectangular stern(with the bottom of the transom in the water), as to
> > whether the sailing performance of the Brick would be degraded. I agree that
> > the capacity will be increased because of the increased wetted surface. Is
> > he suggesting that this could be done with no degradation to the boat's
> > sailing ability?
> >
> > I have never seen a sailboat where the transom sits in the water, as a
> > fishing boat does. The aft part of the hull is always tapered upward to the
> > transom, and the transom is out of the water. There must be a reason why.
> > but I can't imagine why.
> >
> > Would someone clarify this for me? Thanks.
> >
> > Robert
> > Niagara Falls, Ontario
On Fri, Jan 1, 2010 at 10:59 PM, John Bell<yonderman@...>wrote:
Submerged transoms create a lot of turbulence and therefore drag.
When a boat is heeled, even a curved bottom can put part of the transom below the waterline. "Yachty" racers have long overhangs to cheat on the rules and avoid sticking the transom underwater. I think Phil would have anticipated that a Brick with a straight bottom at the stern would be sailed a bit down by the bow so as to raise the transom and keep it from creating too much turbulence. Turbulence is a problem at low length/speed ratios and light winds where thrust is small. At high length/speed ratios, leaving part of the transom underwater would be a help, keeping the boat from squatting and developing a huge bow wave that it will attempt to climb over. A Brick with a straight bottom aft would also have a longer waterline length when lightly loaded, which would allow for a small increase (about 1/5 knot) in top speed on such a short boat as Brick.
Fred
The designer was chided "Even a turd is pointy at both ends..."
Submerged transoms create a lot of turbulence and therefore drag. Sailboats suffer a lot when there's a lot of drag. Build it as designed, or better yet build a PDR!
Submerged transoms create a lot of turbulence and therefore drag. Sailboats suffer a lot when there's a lot of drag. Build it as designed, or better yet build a PDR!
On Fri, Jan 1, 2010 at 9:23 PM, Christopher C. Wetherill<wetherillc@...>wrote:I do not recall the name or the year, but there was a contender to defend the America's cup in the '70s that had a flat stern below the water line. The idea was that the effective water line was thereby longer than the actual. It failed miserably. I think it only works when the hull planes.
V/R
Chris
Mark Albanese wrote:
Morten Olesen at Boatplans.dk used to show a couple of sailboat cruisers with square sterns, though they weren't so successful that he still promotes them.It would be hard to gauge a difference in speed at Brick's scale. The regular stern is rockered so high the boat will surely feel steadier with it run back. For sailing, the regular shape is prudent, not to say traditional. For power alone or as a tiny motorsailer, straight back is sure to work.MarkOn Jan 1, 2010, at 3:59 PM, Robert wrote:
It is uncertain to me that if the bottom were run back to a perfectly rectangular stern(with the bottom of the transom in the water), as to whether the sailing performance of the Brick would be degraded. I agree that the capacity will be increased because of the increased wetted surface. Is he suggesting that this could be done with no degradation to the boat's sailing ability?
I have never seen a sailboat where the transom sits in the water, as a fishing boat does. The aft part of the hull is always tapered upward to the transom, and the transom is out of the water. There must be a reason why. but I can't imagine why.
Would someone clarify this for me? Thanks.
Robert
Niagara Falls, Ontario
V/R
Chris
Mark Albanese wrote:
Morten Olesen at Boatplans.dk used to show a couple of sailboat cruisers with square sterns, though they weren't so successful that he still promotes them.It would be hard to gauge a difference in speed at Brick's scale. The regular stern is rockered so high the boat will surely feel steadier with it run back. For sailing, the regular shape is prudent, not to say traditional. For power alone or as a tiny motorsailer, straight back is sure to work.MarkOn Jan 1, 2010, at 3:59 PM, Robert wrote:
It is uncertain to me that if the bottom were run back to a perfectly rectangular stern(with the bottom of the transom in the water), as to whether the sailing performance of the Brick would be degraded. I agree that the capacity will be increased because of the increased wetted surface. Is he suggesting that this could be done with no degradation to the boat's sailing ability?
I have never seen a sailboat where the transom sits in the water, as a fishing boat does. The aft part of the hull is always tapered upward to the transom, and the transom is out of the water. There must be a reason why. but I can't imagine why.
Would someone clarify this for me? Thanks.
Robert
Niagara Falls, Ontario
Morten Olesen at Boatplans.dk used to show a couple of sailboat cruisers with square sterns, though they weren't so successful that he still promotes them.
It would be hard to gauge a difference in speed at Brick's scale. The regular stern is rockered so high the boat will surely feel steadier with it run back. For sailing, the regular shape is prudent, not to say traditional. For power alone or as a tiny motorsailer, straight back is sure to work.
Mark
On Jan 1, 2010, at 3:59 PM, Robert wrote:
It is uncertain to me that if the bottom were run back to a perfectly rectangular stern(with the bottom of the transom in the water), as to whether the sailing performance of the Brick would be degraded. I agree that the capacity will be increased because of the increased wetted surface. Is he suggesting that this could be done with no degradation to the boat's sailing ability?
I have never seen a sailboat where the transom sits in the water, as a fishing boat does. The aft part of the hull is always tapered upward to the transom, and the transom is out of the water. There must be a reason why. but I can't imagine why.
Would someone clarify this for me? Thanks.
Robert
Niagara Falls, Ontario
Hi, Everyone,
Please disregard the previous attempt at a posting. Yahoo interrupted my message with a request about sharing, when I pressed 'no thanks', it sent the beginning of my message.
In 'Boats with an open mind', Mister Bolger, in his description of the Brick, srites, and I quote ". Rounding or tapering takes away volume; the boat settles deeper in the water and makes deeper, steeper waves. It's possible that running the bottom straight back to a perfectly rectangular stern would increase capacity more than resistance."
It is uncertain to me that if the bottom were run back to a perfectly rectangular stern(with the bottom of the transom in the water), as to whether the sailing performance of the Brick would be degraded. I agree that the capacity will be increased because of the increased wetted surface. Is he suggesting that this could be done with no degradation to the boat's sailing ability?
I have never seen a sailboat where the transom sits in the water, as a fishing boat does. The aft part of the hull is always tapered upward to the transom, and the transom is out of the water. There must be a reason why. but I can't imagine why.
Would someone clarify this for me? Thanks.
Robert
Niagara Falls, Ontario
Please disregard the previous attempt at a posting. Yahoo interrupted my message with a request about sharing, when I pressed 'no thanks', it sent the beginning of my message.
In 'Boats with an open mind', Mister Bolger, in his description of the Brick, srites, and I quote ". Rounding or tapering takes away volume; the boat settles deeper in the water and makes deeper, steeper waves. It's possible that running the bottom straight back to a perfectly rectangular stern would increase capacity more than resistance."
It is uncertain to me that if the bottom were run back to a perfectly rectangular stern(with the bottom of the transom in the water), as to whether the sailing performance of the Brick would be degraded. I agree that the capacity will be increased because of the increased wetted surface. Is he suggesting that this could be done with no degradation to the boat's sailing ability?
I have never seen a sailboat where the transom sits in the water, as a fishing boat does. The aft part of the hull is always tapered upward to the transom, and the transom is out of the water. There must be a reason why. but I can't imagine why.
Would someone clarify this for me? Thanks.
Robert
Niagara Falls, Ontario