Actively variable deadrise
 

"Frogwatch" wrote in message
...
On Mar 20, 1:29 pm, John H wrote:
On Fri, 20 Mar 2009 12:25:30 -0400, HK wrote:
Jim Willemin wrote:
HK wrote in
:

Jim Willemin wrote:
Frogwatch wrote in
news:571e39b1-f812-459a-b9e6-
:

It seems that deadrise has a radical effect on the ability of a
boat
to get on plane quickly and thus use less fuel. More deadrise
makes
a boat punch through waves better but increases draft and reduces
fuel economy in smaller seas. I assume that variable deadrise has
been tried. Of course there are boats that try to use hull shape
to
accomodate varying conditions but not too successfully.
My Tolman has about 10 degree deadrise and is very light so is very
fuel efficient but pounds a lot in chop so I have to slow down to
about 12 kts. Why not some mechanism that would consist of another
outer variable hull layer that would be hinged at the chines
allowing the keel portion to move downward to increase deadrise.
It
would have a flexible stiff plastic piece at the front to keep
water
out of the area between the two hulls. Is this simply too complex
for too little benefit?

Having pondered this for a couple of days, I am struck by the
problem
of changing the area of the floor between the keel and the chine.
This might be tractable near the transom (overlapping leaves,
perhaps, kinda like a 'sliding lapstrake' construction), but as you
get near the stem you gotta worry about major changes in geometry as
well as area. I imagine a really clever designer could do it. I
suppose the question is where in the hull would variable deadrise be
most effective in the transition to planing? That might make an
interesting thesis for someone...

Bring a lifejacket.

I was thinking more of models in a wavetank. But seriously: where in
the hull is deadrise most important to achieving planing status? Is
it
in the forward third, the midships third, or the aft third? Since
planing is essentially the result of climbing one's own bow wake, or
the
wave whose wavelength is equal to your waterline length, my hunch is
that the geometry near the stem is probably most significant in
acheiving planing. But there has to be some kind of optimum - it
seems
to me that a flatiron skiff, say, would take more energy to achieve
planing mode than a runabout of identical length. So if the critical
region is in the forward third of the hull, where major changes in
both
hull geometry and hull area occur as you mess with deadrise, it seems
to
me probably not worth the effort.

Deadrise isn't important in achieving planing status: a flat-bottomed
boat will plane just fine. The more deadrise, the more power it takes to
get a boat up on plane.

...therefore, deadrise *is* important in achieving planing status. The
more deadrise, the more difficult to achieve plane.

I've been reading about "variable deadrise" hulls where the deadrise
changes as one goes from center of the keel area toward the chines.
The pictures all show a series of areas with reduced deadrise toward
the chines. Why not make this a continuous change? I am not sure
what the advantage would be however one can imagine a large deadrise
range at the bow area going to significantly less at transom.
Why does a hard chine boat ride diff from one with rounded chines?

Hard chine probably gives the boat more bottom width. On river jet boats
the difference between a 6'6" bottom width and a 7' width makes a tremendous
difference in planeing speed. Plus the draft on plane. Maybe an equivalent
to less dead rise while starting would be some wings that spread when at
moving in flat water and tucked in while in rough water.

Actively variable deadrise
 

On Mar 20, 7:18 pm, "Calif Bill" wrote:
"Frogwatch" wrote in message

...



On Mar 20, 1:29 pm, John H wrote:
On Fri, 20 Mar 2009 12:25:30 -0400, HK wrote:
Jim Willemin wrote:
HK wrote in
:

Jim Willemin wrote:
Frogwatch wrote in
news:571e39b1-f812-459a-b9e6-
:

It seems that deadrise has a radical effect on the ability of a
boat
to get on plane quickly and thus use less fuel. More deadrise
makes
a boat punch through waves better but increases draft and reduces
fuel economy in smaller seas. I assume that variable deadrise has
been tried. Of course there are boats that try to use hull shape
to
accomodate varying conditions but not too successfully.
My Tolman has about 10 degree deadrise and is very light so is very
fuel efficient but pounds a lot in chop so I have to slow down to
about 12 kts. Why not some mechanism that would consist of another
outer variable hull layer that would be hinged at the chines
allowing the keel portion to move downward to increase deadrise.
It
would have a flexible stiff plastic piece at the front to keep
water
out of the area between the two hulls. Is this simply too complex
for too little benefit?

Having pondered this for a couple of days, I am struck by the
problem
of changing the area of the floor between the keel and the chine.
This might be tractable near the transom (overlapping leaves,
perhaps, kinda like a 'sliding lapstrake' construction), but as you
get near the stem you gotta worry about major changes in geometry as
well as area. I imagine a really clever designer could do it. I
suppose the question is where in the hull would variable deadrise be
most effective in the transition to planing? That might make an
interesting thesis for someone...

Bring a lifejacket.

I was thinking more of models in a wavetank. But seriously: where in
the hull is deadrise most important to achieving planing status? Is
it
in the forward third, the midships third, or the aft third? Since
planing is essentially the result of climbing one's own bow wake, or
the
wave whose wavelength is equal to your waterline length, my hunch is
that the geometry near the stem is probably most significant in
acheiving planing. But there has to be some kind of optimum - it
seems
to me that a flatiron skiff, say, would take more energy to achieve
planing mode than a runabout of identical length. So if the critical
region is in the forward third of the hull, where major changes in
both
hull geometry and hull area occur as you mess with deadrise, it seems
to
me probably not worth the effort.

Deadrise isn't important in achieving planing status: a flat-bottomed
boat will plane just fine. The more deadrise, the more power it takes to
get a boat up on plane.

...therefore, deadrise *is* important in achieving planing status. The
more deadrise, the more difficult to achieve plane.

I've been reading about "variable deadrise" hulls where the deadrise
changes as one goes from center of the keel area toward the chines.
The pictures all show a series of areas with reduced deadrise toward
the chines. Why not make this a continuous change? I am not sure
what the advantage would be however one can imagine a large deadrise
range at the bow area going to significantly less at transom.
Why does a hard chine boat ride diff from one with rounded chines?

Hard chine probably gives the boat more bottom width. On river jet boats
the difference between a 6'6" bottom width and a 7' width makes a tremendous
difference in planeing speed. Plus the draft on plane. Maybe an equivalent
to less dead rise while starting would be some wings that spread when at
moving in flat water and tucked in while in rough water.

Thanks Harry, even makes sense.

Actively variable deadrise
 

On Fri, 20 Mar 2009 16:25:42 -0700 (PDT), Frogwatch
wrote:

On Mar 20, 7:18 pm, "Calif Bill" wrote:
"Frogwatch" wrote in message

...



On Mar 20, 1:29 pm, John H wrote:
On Fri, 20 Mar 2009 12:25:30 -0400, HK wrote:
Jim Willemin wrote:
HK wrote in
:

Jim Willemin wrote:
Frogwatch wrote in
news:571e39b1-f812-459a-b9e6-
:

It seems that deadrise has a radical effect on the ability of a
boat
to get on plane quickly and thus use less fuel. More deadrise
makes
a boat punch through waves better but increases draft and reduces
fuel economy in smaller seas. I assume that variable deadrise has
been tried. Of course there are boats that try to use hull shape
to
accomodate varying conditions but not too successfully.
My Tolman has about 10 degree deadrise and is very light so is very
fuel efficient but pounds a lot in chop so I have to slow down to
about 12 kts. Why not some mechanism that would consist of another
outer variable hull layer that would be hinged at the chines
allowing the keel portion to move downward to increase deadrise.
It
would have a flexible stiff plastic piece at the front to keep
water
out of the area between the two hulls. Is this simply too complex
for too little benefit?

Having pondered this for a couple of days, I am struck by the
problem
of changing the area of the floor between the keel and the chine.
This might be tractable near the transom (overlapping leaves,
perhaps, kinda like a 'sliding lapstrake' construction), but as you
get near the stem you gotta worry about major changes in geometry as
well as area. I imagine a really clever designer could do it. I
suppose the question is where in the hull would variable deadrise be
most effective in the transition to planing? That might make an
interesting thesis for someone...

Bring a lifejacket.

I was thinking more of models in a wavetank. But seriously: where in
the hull is deadrise most important to achieving planing status? Is
it
in the forward third, the midships third, or the aft third? Since
planing is essentially the result of climbing one's own bow wake, or
the
wave whose wavelength is equal to your waterline length, my hunch is
that the geometry near the stem is probably most significant in
acheiving planing. But there has to be some kind of optimum - it
seems
to me that a flatiron skiff, say, would take more energy to achieve
planing mode than a runabout of identical length. So if the critical
region is in the forward third of the hull, where major changes in
both
hull geometry and hull area occur as you mess with deadrise, it seems
to
me probably not worth the effort.

Deadrise isn't important in achieving planing status: a flat-bottomed
boat will plane just fine. The more deadrise, the more power it takes to
get a boat up on plane.

...therefore, deadrise *is* important in achieving planing status. The
more deadrise, the more difficult to achieve plane.

I've been reading about "variable deadrise" hulls where the deadrise
changes as one goes from center of the keel area toward the chines.
The pictures all show a series of areas with reduced deadrise toward
the chines. Why not make this a continuous change? I am not sure
what the advantage would be however one can imagine a large deadrise
range at the bow area going to significantly less at transom.
Why does a hard chine boat ride diff from one with rounded chines?

Hard chine probably gives the boat more bottom width. On river jet boats
the difference between a 6'6" bottom width and a 7' width makes a tremendous
difference in planeing speed. Plus the draft on plane. Maybe an equivalent
to less dead rise while starting would be some wings that spread when at
moving in flat water and tucked in while in rough water.

Thanks Harry, even makes sense.

For the record. That wisdom did not come from Harry.

Actively variable deadrise
 

On Mar 20, 10:25*am, "Don White" wrote:
wrote in message

...
On Mar 19, 5:24 pm, "Don White" wrote:





"Vic Smith" wrote in message

.. .

Not bad when you consider it took Edward G. Robinson 606 tries before
he arrived at the "magic bullet" cure for syphilis.
Killed a lot of people doing it too.


--Vic

So it's not a good idea for JohnnyPrepH to lubricate/winterize his
outboards
cylinders with WD-40?

Cylinders don't have bearings, idiot.

************************************************

I didn't say they did jackass.- Hide quoted text -

- Show quoted text -

Oh, I take it you didn't understand the sentence you quoted,
then......
Here is what was said:
"Just like WD-40 is still killing bearings."

To which you idiotically replied....

So it's not a good idea for JohnnyPrepH to lubricate/winterize his
outboards cylinders with WD-40?

So......why did you make such a statement directly replying to a
statement about....BEARINGS?

Actively variable deadrise
 

wrote in message
...
On Mar 20, 10:25 am, "Don White" wrote:
wrote in message

...
On Mar 19, 5:24 pm, "Don White" wrote:





"Vic Smith" wrote in message

.. .

Not bad when you consider it took Edward G. Robinson 606 tries before
he arrived at the "magic bullet" cure for syphilis.
Killed a lot of people doing it too.


--Vic

So it's not a good idea for JohnnyPrepH to lubricate/winterize his
outboards
cylinders with WD-40?

Cylinders don't have bearings, idiot.

************************************************

I didn't say they did jackass.- Hide quoted text -

- Show quoted text -

Oh, I take it you didn't understand the sentence you quoted,
then......
Here is what was said:
"Just like WD-40 is still killing bearings."

To which you idiotically replied....

So it's not a good idea for JohnnyPrepH to lubricate/winterize his
outboards cylinders with WD-40?

So......why did you make such a statement directly replying to a
statement about....BEARINGS?

************************************************** *

For the sake of the children.......quit growin' & smokin' that Georgia Bud!

Actively variable deadrise
 

On Mar 21, 12:28*pm, "Don White" wrote:
wrote in message

...
On Mar 20, 10:25 am, "Don White" wrote:





wrote in message

....
On Mar 19, 5:24 pm, "Don White" wrote:

"Vic Smith" wrote in message

.. .

Not bad when you consider it took Edward G. Robinson 606 tries before
he arrived at the "magic bullet" cure for syphilis.
Killed a lot of people doing it too.

--Vic

So it's not a good idea for JohnnyPrepH to lubricate/winterize his
outboards
cylinders with WD-40?

Cylinders don't have bearings, idiot.

************************************************

I didn't say they did jackass.- Hide quoted text -

- Show quoted text -

Oh, I take it you didn't understand the sentence you quoted,
then......
Here is what was said:
*"Just like WD-40 is still killing bearings."

To which you idiotically replied....

So it's not a good idea for JohnnyPrepH to lubricate/winterize his
outboards cylinders with WD-40?

So......why did you make such a statement directly replying to a
statement about....BEARINGS?

************************************************** *

For the sake of the children.......quit growin' & smokin' that Georgia Bud!- Hide quoted text -

- Show quoted text -

What on earth are you babbling about now? You've learned from your
lover/master/clone Harry how to deflect with idiotic comments when
someone shows just how stupid you are. Or do you have some mental
incapacity that makes you wander off on different tangents, not being
able to keep on the topic at hand?

Actively variable deadrise
 

wrote in message
...
On Mar 21, 12:28 pm, "Don White" wrote:
wrote in message

...
On Mar 20, 10:25 am, "Don White" wrote:





wrote in message

...
On Mar 19, 5:24 pm, "Don White" wrote:

"Vic Smith" wrote in message

.. .

Not bad when you consider it took Edward G. Robinson 606 tries
before
he arrived at the "magic bullet" cure for syphilis.
Killed a lot of people doing it too.

--Vic

So it's not a good idea for JohnnyPrepH to lubricate/winterize his
outboards
cylinders with WD-40?

Cylinders don't have bearings, idiot.

************************************************

I didn't say they did jackass.- Hide quoted text -

- Show quoted text -

Oh, I take it you didn't understand the sentence you quoted,
then......
Here is what was said:
"Just like WD-40 is still killing bearings."

To which you idiotically replied....

So it's not a good idea for JohnnyPrepH to lubricate/winterize his
outboards cylinders with WD-40?

So......why did you make such a statement directly replying to a
statement about....BEARINGS?

************************************************** *

For the sake of the children.......quit growin' & smokin' that Georgia
Bud!- Hide quoted text -

- Show quoted text -

What on earth are you babbling about now? You've learned from your
lover/master/clone Harry how to deflect with idiotic comments when
someone shows just how stupid you are. Or do you have some mental
incapacity that makes you wander off on different tangents, not being
able to keep on the topic at hand?

************************************

Not at all. I just deal with the facts as they are revealed to me.
Drop the weed...for the kids!

Actively variable deadrise
 

On Mar 21, 1:27*pm, "Don White" wrote:
wrote in message

...
On Mar 21, 12:28 pm, "Don White" wrote:





wrote in message

....
On Mar 20, 10:25 am, "Don White" wrote:

wrote in message

....
On Mar 19, 5:24 pm, "Don White" wrote:

"Vic Smith" wrote in message

.. .

Not bad when you consider it took Edward G. Robinson 606 tries
before
he arrived at the "magic bullet" cure for syphilis.
Killed a lot of people doing it too.

--Vic

So it's not a good idea for JohnnyPrepH to lubricate/winterize his
outboards
cylinders with WD-40?

Cylinders don't have bearings, idiot.

************************************************

I didn't say they did jackass.- Hide quoted text -

- Show quoted text -

Oh, I take it you didn't understand the sentence you quoted,
then......
Here is what was said:
"Just like WD-40 is still killing bearings."

To which you idiotically replied....

So it's not a good idea for JohnnyPrepH to lubricate/winterize his
outboards cylinders with WD-40?

So......why did you make such a statement directly replying to a
statement about....BEARINGS?

************************************************** *

For the sake of the children.......quit growin' & smokin' that Georgia
Bud!- Hide quoted text -

- Show quoted text -

What on earth are you babbling about now? You've learned from your
lover/master/clone Harry how to deflect with idiotic comments when
someone shows just how stupid you are. Or do you have some mental
incapacity that makes you wander off on different tangents, not being
able to keep on the topic at hand?

************************************

Not at all. I just deal with the facts as they are revealed to me.
Drop the weed...for the kids!- Hide quoted text -

- Show quoted text -

Well, then, give me the facts. WHAT WEED, dummy? What "facts" were
"revealed" to you? By whom? Who told you I smoke "grow and smoke"
ANYTHING? We'll see how good you do with "facts"......

Actively variable deadrise
 

- Show quoted text -

In theory the concept of mechanically variable deadrise should work
but in practice the complexity is too much of an obstacle in a small
boat so it makes more sense to have a different boat design for
different conditions and/or operational parameters. In a larger craft
the objective is more easily achieved with designs such as SWATH,
catamarans, or hydrofoils. Current high speed ferries are good
examples, and the Russians have built some neat hydrofoils .

I took the Westlawn course for my own entertainment and while much of
the facts and figures that I learned have been lost most of the
concepts are still clear. A couple of points… At rest your boat stays
above the surface of the water because of the hull’s buoyancy and by
virtue of its static displacement. Once you start moving your hull
will generate a series of waves in the medium that it is floating in.
At a point called hull speed your boat will be traveling in a trough
between the bow wave and the stern wave. As you increase speed further
the bow will rise as it attempts to climb the bow wave and at some
point Newton’s Third Law will kick in and the action of the water
meeting you hull surface will result in a equal reaction that will
lift the hull of your boat. Then, at some point the flow of water
against the hull will separate from one stream flowing under your hull
into two, one flowing under the hull and another flowing forward of
the hull as spray. This is the stagnation point, the point where
maximum lift is generated. Any water striking the hull at this point
is converted into 100 percent lift. Anything forward is wasted as
spray and anything aft will act on the rear planing surface and affect
the angle of attack. As speed increases the stagnation point will move
aft and at the same time the CG of the hull will move up. (BTW, This
is where trim tabs come in. They can be used to adjust the trimming
force and thus the angle of attack, but they will not create lift…).
Eventually the weight of your boat is no longer being supported by the
displacement of water but by the dynamic force of the water striking
its planing surface. A perfectly flat bottom means that the lift is
vertical. A vee bottom wastes a percentage of the energy as spray
deflected to the side.

If any of the above makes sense then it would seem that we would need
to adjust the deadrise at the stagnation point to avoid pounding. The
problem is that with any small boat running in a sea this point moves
fore and aft on the hull due to the waves that it encounters. Most
modern hulls deal with this by having a sharper vee at the bow and
less dead rise at the stern so I guess the answer to your original
question is that your radical idea has already been incorporated into
almost every hull design! In reality we know that every hull is a
compromise and the overall deadrise is always a tradeoff between sea
keeping and efficiency. I know that Seacraft for one advertised
variable deadrise as being a change in angle from keel to chine but in
normal marine architects language this is a term that refers to the
variation in dead rise angle measured at different points from bow to
stern. Constant dead rise hulls are referred to as Monohedron versus a
variable dead rise called a warped plane. Warped planes have their
limits as far as how much you can “warp” them before you trade off
performance especially if we are talking “Miami Vice” type boats.

Lobster boats or Downeast designs stretch the warped plane idea. They
have a very sharp entry forward but an almost flat bottom aft. This
limits their performance but it is the main reason for their famed
ride. Round bilges and full keels have nothing to do with it.

Steve P.

Actively variable deadrise
 

On Mar 21, 7:22 pm, Monkey Butler wrote:
- Show quoted text -

In theory the concept of mechanically variable deadrise should work
but in practice the complexity is too much of an obstacle in a small
boat so it makes more sense to have a different boat design for
different conditions and/or operational parameters. In a larger craft
the objective is more easily achieved with designs such as SWATH,
catamarans, or hydrofoils. Current high speed ferries are good
examples, and the Russians have built some neat hydrofoils .

I took the Westlawn course for my own entertainment and while much of
the facts and figures that I learned have been lost most of the
concepts are still clear. A couple of points… At rest your boat stays
above the surface of the water because of the hull’s buoyancy and by
virtue of its static displacement. Once you start moving your hull
will generate a series of waves in the medium that it is floating in.
At a point called hull speed your boat will be traveling in a trough
between the bow wave and the stern wave. As you increase speed further
the bow will rise as it attempts to climb the bow wave and at some
point Newton’s Third Law will kick in and the action of the water
meeting you hull surface will result in a equal reaction that will
lift the hull of your boat. Then, at some point the flow of water
against the hull will separate from one stream flowing under your hull
into two, one flowing under the hull and another flowing forward of
the hull as spray. This is the stagnation point, the point where
maximum lift is generated. Any water striking the hull at this point
is converted into 100 percent lift. Anything forward is wasted as
spray and anything aft will act on the rear planing surface and affect
the angle of attack. As speed increases the stagnation point will move
aft and at the same time the CG of the hull will move up. (BTW, This
is where trim tabs come in. They can be used to adjust the trimming
force and thus the angle of attack, but they will not create lift…).
Eventually the weight of your boat is no longer being supported by the
displacement of water but by the dynamic force of the water striking
its planing surface. A perfectly flat bottom means that the lift is
vertical. A vee bottom wastes a percentage of the energy as spray
deflected to the side.

If any of the above makes sense then it would seem that we would need
to adjust the deadrise at the stagnation point to avoid pounding. The
problem is that with any small boat running in a sea this point moves
fore and aft on the hull due to the waves that it encounters. Most
modern hulls deal with this by having a sharper vee at the bow and
less dead rise at the stern so I guess the answer to your original
question is that your radical idea has already been incorporated into
almost every hull design! In reality we know that every hull is a
compromise and the overall deadrise is always a tradeoff between sea
keeping and efficiency. I know that Seacraft for one advertised
variable deadrise as being a change in angle from keel to chine but in
normal marine architects language this is a term that refers to the
variation in dead rise angle measured at different points from bow to
stern. Constant dead rise hulls are referred to as Monohedron versus a
variable dead rise called a warped plane. Warped planes have their
limits as far as how much you can “warp” them before you trade off
performance especially if we are talking “Miami Vice” type boats.

Lobster boats or Downeast designs stretch the warped plane idea. They
have a very sharp entry forward but an almost flat bottom aft. This
limits their performance but it is the main reason for their famed
ride. Round bilges and full keels have nothing to do with it.

Steve P.

Steve:

Ok, I got most of that, but, why does a boat make a stern wave?