On Thu, 10 Dec 2009 19:02:23 -0700, "Bob La Londe"
wrote:

"Bruce In Bangkok" wrote in message


I suppose the most logical question is "why". Yes, you can bend
aluminum at a sharper angle and have a less radiused bend by thinning
the aluminum at the fold line but what is the necessity for this
fabrication?

I'm not sure what you mean by a "racing pad" but I can't see any
correlation between sharp and speed. Unless you mean that the hard
chines have a sharp edge whereby they are more effective in combating
lateral forces?

On certain types of boats there is a narrow "pad" along the keel about a
foot wide. This will vary based on design, weight, and over all size of the
boat. At high speeds the boat is running mostly on this pad. Far be it
from me to explain the dynamics of it, (I'm just parroting what the speed
junkies say here) but there are a couple things that can improve speed. I
certainly do not know all the design characteristics that contribute to
optimum design, but one of them is supposed to be the sharpness of the edge
of this pad. Perhaps it has something to due with the way it sheds water or
breaks the surface tension of the water. Another is a rough rather than
smooth finish to the bottom of the pad. That most definitely has to do with
breaking the surface tension of the water. Like a shark skin bathing suit
or the finish on certain high tech racing sail boats.

I agree, that if one is determined to use this sort of bend that one
can probably design something that necessitates it but it is doubtful
that it is really necessary.

Well, obviously if the goal does not involve eeking 1 more MPH out of your
hull's top speed there's no point. LOL. Pun intended.

In addition, I do not believe that, providing you are talking about
lengths usually found in boat building, say chine logs, that run the
length of the boat that warping will not be a problem.

I think it would be much less of a problem than with two separate pieces
joined to make the same edge.

You say you can
see some warping in a 3 ft. piece... What about 45 ft. chines on a
sail boat?

Ah, see. Now I know you didn't understand what I wrote. I saw that kind of
warping in pieces that long that were welded together to form the edge. Not
in a single piece thinned and folded. Big difference. My apologies for not
being clear. When you start with one piece that is bent to form an angle
its going to be much more rigid than two pieces stuck together. The
remaining metal that holds the two legs of the angle together will not allow
them to expand and contract at different rates due to vagaries in welding
technique. I was mostly trying to point out that after I had completed my
initial work pieces I experimented some to see what else worked and how it
worked.

My assessment, for whatever it is worth,

Its worth a lot. If I do not look at ideas from a different point of view I
can't see what's wrong with them or how to make them better. It forces me
to engage my brain.

is that "your" system is
certainly viable and, depending on the size of the weld bead, may even
be stronger then a simple bend, however... It takes more time to make
and will be more costly as well as offering more chances of error in
manufacture then alternate methods.

Like? Roller bending? Edge welding two pieces? Braking?

Well, I don't know what you can do with roller bending, but they use it to
put longitudinal creases in sheet for strength. Not sure how it would apply
in this case anyway. I guess it might be an alternative way to make my
thinned and folded edge instead of the brute force method I used before. It
might make doing this more practical on longer pieces.

Edge welding. No way. To do an ideal corner weld you have to weld it
twice. I covered that. Most commercial mass production builders don't, but
a lot of their boats crack too. Weld, back chip, weld.

Braking? Well see this one is arguable. A brake is a tried and true
method. It works and its fast. If you can afford one big enough to do the
job. At this time I can't. It will definitely not make a bend as sharp as
the process I describe.

I can setup a built rig to bend "thinned" metal. I am sure the weld will be
better than two pieces edge welded in less time. IN GENERAL... There is
some grey area about the actual deep corner of the inside of the bend. I
guess to resolve that I would need to weld up some more pieces and then
slice it up to see if I get those corner voids I fear. If it gets a void in
it then there is a very thin bit of aluminum on the outside which could
break through easily. Not an issue for one outing or even a dozen, but it
could create a pocket that could trap water. We know about trapped water
and aluminum over time. Big potential problem.

The ability to perform the process is not in question. The reason is in
question depending on your goals.

My reason for considering the idea is building an aluminum boat that will
out run a glass boat in the same size class. ie to take advantage of the
weight savings with out throwing them away on hull shape.

My biggest concern would be the stresses on this very sharp hard point.

A hard point (as I am sure you already know) is a corner, turn, or bend in
the design of a boat or other structure that may concentrate the stress from
external forces due to a fast or abrupt change in shape. That's why we
often see stress cracks in the gel coat of glass boats in the corners of the
top cap. Its also why we see cracks at the weld in the back corner of a lot
of older Trackers and some other boats or at the front corners of square jon
boats. (HAZ and alloy selection not withstanding.)

I wish that you could point me at a url showing this "speed pad" as I
can't seem to visualize it, nor can I find more then the words, i.e.,
has a speed pad. I am somewhat familiar with the hulls of both three
point hulls (the old speed boat hulls with the sponsons) and more
modern open ocean racing stuff, but the speed pad defeats me

True that corners can be stress risers, or hard points, but simply
having a sharp corner does not cause cracking, it simply provides a
location where, assuming that the item is incorrectly designed,
stresses will concentrate. So, if you have an item that is not
designed to resist the forces applied to it a sharp corner will be the
likely location for deformation to occur.

Again, as I previously wrote, if you want to use a bent/welded
structure then you will certainly be able to design a need for it :-)

Cheers,

Bruce
(bruceinbangkokatgmaildotcom)

"Bruce In Bangkok" wrote in message
...

I wish that you could point me at a url showing this "speed pad" as I
can't seem to visualize it, nor can I find more then the words, i.e.,
has a speed pad. I am somewhat familiar with the hulls of both three
point hulls (the old speed boat hulls with the sponsons) and more
modern open ocean racing stuff, but the speed pad defeats me


Most modern high performance fiberglass bass boats made today have a pad
style bottom atleast to some degree. Fast Cat (tunnel) and a few shallow V
and pocket tunnel flats boats being the exceptions.

http://www.bwbmag.com/output.cfm?id=1122481 "When we think of a bass boat,
we typically envision a modified V hull, with a pad bottom, and more often
than not, an extended transom/built-in jackplate. Pretty cool stuff, right?
"

Kinda goes to the argument that it's a pretty common thing if that's what
"we typically envision."

Here is an aluminum one, but I do not like their design. Most are flatter,
although a lot of Rangers have a semi V pad like that. I mostly do not like
the sandwiched or layer construction for aluminum as it can trap water.
Their V pad might be the most efficient design for some setups, or possibley
the best compromise: http://www.freepatentsonline.com/6666162.html

Here is a picture of the inside the hull for one under construction. The
outside view would be much more defined.
http://media.photobucket.com/image/b...lassonhull.jpg

I am finding that there is an amazing dearth of pictures online of the
bottom of bass boats. I am finding myself headed out to the shop to take
pictures of the bottom of my Basscat.

Here is a view from the transom:
http://www.yumabassman.com/pictures/shelf-001.gif

And here is another from underneath. I played with the colors and the
contrast so that you could see it's a fairly long structure on the bottom of
the boat. About half the length of the boat.
http://www.yumabassman.com/pictures/shelf-002.gif

The boat in the last two pictures is not particularly fast as bass boats in
this size class go. Its being pushed by a factory stock Mercury 250 Pro XS
that dynos out at about 260-270 prop shaft horsepower depending on
elevation, temperature, humidity, etc. It's a 20 foot 4 inch fiberglass
boat and it weighs about 3000 lbs give or take depending on fuel, livewells,
gear, driver, and passengers, etc. I have GPSed it at 74+ MPH (statute
miles) with a pretty good load. With this particular boat I have been able
to average 60+ in 3 foot chop for a 30+ mile run in a tournament. There are
guys running a slightly different prop getting 78-79 out of this same hull
with what we call a "full tournament load." I picked the prop that gave me
the better hole shot. I also have a sloppy hydraulic jack plate on this
boat which I need to replace. I imagine it complicates my high speed
driving a bit. Similar lighter boats the same size will run high 80s and
there are a few pushing the century mark. I'm talking production 20 foot
class fiberglass "modified V" pad bottom boats with a factory configuration
250 Pro XS motor. Not a hot rodded motor or a blue printed hull.

Allison I am sure has several semi custom 20' glass composite pad Vs that
will break 100 MPH in his stable running similar horsepower. He holds
enough world records. He doesn't like the new 3 liter motors much though.
Too heavy for his favorite boats.

I am most definitely not grasping at some obscure concept as you seem to
imply. Skeeter, Ranger, Triton, Champion, Procraft, Nitro, Allison, Bullet,
Gambler, Blazer, Bass Cat, Hydrasports, etc all use a modified V pad bottom
design in some form. It is not a new concept. Its been around for atleast
25 years that I know of first hand. Our first pad bottom boat was a 20'
Hydrasport back in the mid 1980s. We ran an Evirnrude 235 race motor on it,
we never had the nerve to find out how fast it would go. It was fast
enough.

To my knowledge none of the manufacturers make a production boat with super
sharp edges on the pad because they would wear off quickly in typical use,
and the edges would break easily compared to a rounded corner.

The only thing that might be in question is my belief from the hearsay of
professional boat builders and speed junkies that a sharp edge on the pad
can somehow improve top speed. I've certainly seen the hulls that have been
flipped over and trued up and the pads with the razor sharp corners.

A single sheet stamped and formed might be able to achieve all that
wonderfulness. The only stamp formed aluminum boat I am aware of the is the
Tracker Avalanche and it is discontinued. I also think it as not a pad
bottom, and it was welded right down the keel to join two piece. LOL. So
much for wonderfulness.

Yeah, I threw of non supporting side information in there, but I think it
makes for a more interesting read.

"Bob La Londe" wrote in message
...

I was looking at something else entirely when I ran across this.
http://www.allisonboats.com/skid_planer.php

He's hawking his lifting plate, but you can clearly see the pad on the rear
of the boat in the pictures.

On Fri, 11 Dec 2009 20:44:31 -0700, "Bob La Londe"
wrote:

"Bruce In Bangkok" wrote in message
.. .

I wish that you could point me at a url showing this "speed pad" as I
can't seem to visualize it, nor can I find more then the words, i.e.,
has a speed pad. I am somewhat familiar with the hulls of both three
point hulls (the old speed boat hulls with the sponsons) and more
modern open ocean racing stuff, but the speed pad defeats me


Most modern high performance fiberglass bass boats made today have a pad
style bottom atleast to some degree. Fast Cat (tunnel) and a few shallow V
and pocket tunnel flats boats being the exceptions.

http://www.bwbmag.com/output.cfm?id=1122481 "When we think of a bass boat,
we typically envision a modified V hull, with a pad bottom, and more often
than not, an extended transom/built-in jackplate. Pretty cool stuff, right?
"

Kinda goes to the argument that it's a pretty common thing if that's what
"we typically envision."

Here is an aluminum one, but I do not like their design. Most are flatter,
although a lot of Rangers have a semi V pad like that. I mostly do not like
the sandwiched or layer construction for aluminum as it can trap water.
Their V pad might be the most efficient design for some setups, or possibley
the best compromise: http://www.freepatentsonline.com/6666162.html

Here is a picture of the inside the hull for one under construction. The
outside view would be much more defined.
http://media.photobucket.com/image/b...lassonhull.jpg

I am finding that there is an amazing dearth of pictures online of the
bottom of bass boats. I am finding myself headed out to the shop to take
pictures of the bottom of my Basscat.

Here is a view from the transom:
http://www.yumabassman.com/pictures/shelf-001.gif

O.K. I see what you are talking about now. Essentially a flat bottomed
boat once you reach the optimum speed.

Cheers,

Bruce
(bruceinbangkokatgmaildotcom)

"Bruce In Bangkok" wrote in message
...
On Fri, 11 Dec 2009 20:44:31 -0700, "Bob La Londe"
wrote:

"Bruce In Bangkok" wrote in message
. ..

I wish that you could point me at a url showing this "speed pad" as I
can't seem to visualize it, nor can I find more then the words, i.e.,
has a speed pad. I am somewhat familiar with the hulls of both three
point hulls (the old speed boat hulls with the sponsons) and more
modern open ocean racing stuff, but the speed pad defeats me


Most modern high performance fiberglass bass boats made today have a pad
style bottom atleast to some degree. Fast Cat (tunnel) and a few shallow
V
and pocket tunnel flats boats being the exceptions.

http://www.bwbmag.com/output.cfm?id=1122481 "When we think of a bass
boat,
we typically envision a modified V hull, with a pad bottom, and more often
than not, an extended transom/built-in jackplate. Pretty cool stuff,
right?
"

Kinda goes to the argument that it's a pretty common thing if that's what
"we typically envision."

Here is an aluminum one, but I do not like their design. Most are
flatter,
although a lot of Rangers have a semi V pad like that. I mostly do not
like
the sandwiched or layer construction for aluminum as it can trap water.
Their V pad might be the most efficient design for some setups, or
possibley
the best compromise: http://www.freepatentsonline.com/6666162.html

Here is a picture of the inside the hull for one under construction. The
outside view would be much more defined.
http://media.photobucket.com/image/b...lassonhull.jpg

I am finding that there is an amazing dearth of pictures online of the
bottom of bass boats. I am finding myself headed out to the shop to take
pictures of the bottom of my Basscat.

Here is a view from the transom:
http://www.yumabassman.com/pictures/shelf-001.gif

O.K. I see what you are talking about now. Essentially a flat bottomed
boat once you reach the optimum speed.


Essentially. Yes. A narrow flat bottom boat. Low resistance and tends to
put motive force towards going forward rather than up. Speed and power
available being major factors of course.

I do not have the math skills or the engineering background to explain it
all, but I think it works like this. The narrow pad creates less resistance
than a V of similar surface area within the displacement envelope primarily,
but not exclusively because of the surface tension of the water. There are
other other forces such as angle of pressure, total pressure against forward
movement etc. The idea is the boat comes up and then flattens out. The
edge of the pad will break the surface tension of the water and shed the
water much more quickly than than a straight V will, and it will have less
surface area touching the water than a shallower V design or than a flat
bottom boat. More of the extra power is used to push the boat forward
rather than to lift the boat out of the water. I discovered this first hand
when I went from a 225 (around 215-220 HP) to a 250 Pro XS (260-270 HP) on
the boat I pictured. At 70+ I need less trim angle than I did at 68 (WOT)
with the old motor.

This has been bouncing around in my head as well since you forced me to
think a little more. The reason I think a sharp edge is more efficient is
basically the same as why a pad is more efficient at optimum speeds. The
sharper edge will break the surface tension and shed water weight and reduce
resistance much sooner than a rounded edge. The average boater will never
notice the difference, but guys who are always running on the ragged edge
(oxymoron not intended) and looking for the best performing prop to run
right at redline will notice the extra 1 or 2 miles per hour.

The difference is certainly much less than the simple large gains from a pad
style bottom vs a V bottom.

There are a lot of dynamics involved. Some can be engineered away, but
since I am not an engineer I have to visualize and maybe experiment.

** Thought I better throw this in: **
Chine walk can be deadly scary in such a boat if not properly setup or if
driven by somebody who hasn't taken the time to learn to drive their rig.
The biggest safety move for anybody else reading this is to SLOW DOWN
gradually. A sudden loss of throttle can be almost as dangerous.
Especially in traffic in a busy system. Increase power (like I did) and

Bob La Londe
www.YumaBassMan.com

"Bob La Londe" wrote in message
...
** Thought I better throw this in: **
Chine walk can be deadly scary in such a boat if not properly setup or if
driven by somebody who hasn't taken the time to learn to drive their rig.
The biggest safety move for anybody else reading this is to SLOW DOWN
gradually. A sudden loss of throttle can be almost as dangerous.
Especially in traffic in a busy system. Increase power (like I did) and
...

.... and it's a whole new rig to learn how to drive.



Bob La Londe
www.YumaBassMan.com

On Sat, 12 Dec 2009 14:01:13 -0700, "Bob La Londe"
wrote:

"Bruce In Bangkok" wrote in message
.. .
On Fri, 11 Dec 2009 20:44:31 -0700, "Bob La Londe"
wrote:

"Bruce In Bangkok" wrote in message
...

I wish that you could point me at a url showing this "speed pad" as I
can't seem to visualize it, nor can I find more then the words, i.e.,
has a speed pad. I am somewhat familiar with the hulls of both three
point hulls (the old speed boat hulls with the sponsons) and more
modern open ocean racing stuff, but the speed pad defeats me


Most modern high performance fiberglass bass boats made today have a pad
style bottom atleast to some degree. Fast Cat (tunnel) and a few shallow
V
and pocket tunnel flats boats being the exceptions.

http://www.bwbmag.com/output.cfm?id=1122481 "When we think of a bass
boat,
we typically envision a modified V hull, with a pad bottom, and more often
than not, an extended transom/built-in jackplate. Pretty cool stuff,
right?
"

Kinda goes to the argument that it's a pretty common thing if that's what
"we typically envision."

Here is an aluminum one, but I do not like their design. Most are
flatter,
although a lot of Rangers have a semi V pad like that. I mostly do not
like
the sandwiched or layer construction for aluminum as it can trap water.
Their V pad might be the most efficient design for some setups, or
possibley
the best compromise: http://www.freepatentsonline.com/6666162.html

Here is a picture of the inside the hull for one under construction. The
outside view would be much more defined.
http://media.photobucket.com/image/b...lassonhull.jpg

I am finding that there is an amazing dearth of pictures online of the
bottom of bass boats. I am finding myself headed out to the shop to take
pictures of the bottom of my Basscat.

Here is a view from the transom:
http://www.yumabassman.com/pictures/shelf-001.gif

O.K. I see what you are talking about now. Essentially a flat bottomed
boat once you reach the optimum speed.


Essentially. Yes. A narrow flat bottom boat. Low resistance and tends to
put motive force towards going forward rather than up. Speed and power
available being major factors of course.

I do not have the math skills or the engineering background to explain it
all, but I think it works like this. The narrow pad creates less resistance
than a V of similar surface area within the displacement envelope primarily,
but not exclusively because of the surface tension of the water. There are
other other forces such as angle of pressure, total pressure against forward
movement etc. The idea is the boat comes up and then flattens out. The
edge of the pad will break the surface tension of the water and shed the
water much more quickly than than a straight V will, and it will have less
surface area touching the water than a shallower V design or than a flat
bottom boat. More of the extra power is used to push the boat forward
rather than to lift the boat out of the water. I discovered this first hand
when I went from a 225 (around 215-220 HP) to a 250 Pro XS (260-270 HP) on
the boat I pictured. At 70+ I need less trim angle than I did at 68 (WOT)
with the old motor.

As speed increases water pressure against the bottom of the boat
increases and increases lift (if that is what you want to term the
force acting against the bottom of the boat). If "X" lifting force is
applied to a flat surface, at 90 degrees to the force, the entire
force is applied to the surface at 90 degrees to the surface. If the
same force is applied to a surface at other then 90 degrees only a
part of the force will be applied at 90 degrees to the surface. Thus
the same lift, derived from forward speed,applied to a vee hull will
result in less force being applied to raise the boat "up" then if the
same lifting force applied to a flat surface.

This has been bouncing around in my head as well since you forced me to
think a little more. The reason I think a sharp edge is more efficient is
basically the same as why a pad is more efficient at optimum speeds. The
sharper edge will break the surface tension and shed water weight and reduce
resistance much sooner than a rounded edge. The average boater will never
notice the difference, but guys who are always running on the ragged edge
(oxymoron not intended) and looking for the best performing prop to run
right at redline will notice the extra 1 or 2 miles per hour.

Rather then "surface tension" I suspect (if the effect is not large)
that it is simply a matter of surface area. Exactly the same reason
that the small flat bottom is faster then a vee. At any speed it would
take more "lift" to raise an inclined (vee) surface then one at right
angles to the force, thus any rounded corner would act much the same
as the vee, for that portion of the pad, and reduce total lifting
force, by some percentage.

However.... I have read that the multiple, sharp edged, chine designs
actually increase speed because the sharp edged chines increase the
amount of air that is trapped and forced to flow under the boat but
whether that works to decrease drag by reducing the viscosity of the
water or by reducing the wetted area I don't know.

The difference is certainly much less than the simple large gains from a pad
style bottom vs a V bottom.

That is a simple to demonstrate. Hold your hand out of the window of a
moving auto. If you hold your hand flat there is a large force applied
to the hand. Turn your hand on edge and there is little force applied.

There are a lot of dynamics involved. Some can be engineered away, but
since I am not an engineer I have to visualize and maybe experiment.

** Thought I better throw this in: **
Chine walk can be deadly scary in such a boat if not properly setup or if
driven by somebody who hasn't taken the time to learn to drive their rig.
The biggest safety move for anybody else reading this is to SLOW DOWN
gradually. A sudden loss of throttle can be almost as dangerous.
Especially in traffic in a busy system. Increase power (like I did) and

Bob La Londe
www.YumaBassMan.com

Cheers,

Bruce
(bruceinbangkokatgmaildotcom)

"Bruce In Bangkok" wrote in message
...
On Sat, 12 Dec 2009 14:01:13 -0700, "Bob La Londe"
wrote:
This has been bouncing around in my head as well since you forced me to
think a little more. The reason I think a sharp edge is more efficient is
basically the same as why a pad is more efficient at optimum speeds. The
sharper edge will break the surface tension and shed water weight and
reduce
resistance much sooner than a rounded edge. The average boater will never
notice the difference, but guys who are always running on the ragged edge
(oxymoron not intended) and looking for the best performing prop to run
right at redline will notice the extra 1 or 2 miles per hour.

Rather then "surface tension" I suspect (if the effect is not large)
that it is simply a matter of surface area. Exactly the same reason
that the small flat bottom is faster then a vee. At any speed it would
take more "lift" to raise an inclined (vee) surface then one at right
angles to the force, thus any rounded corner would act much the same
as the vee, for that portion of the pad, and reduce total lifting
force, by some percentage.

That is certainly part of the equation now that I think about it. Surface
tension has an affect as well. I'm sure the answer is not one dimensional.


However.... I have read that the multiple, sharp edged, chine designs
actually increase speed because the sharp edged chines increase the
amount of air that is trapped and forced to flow under the boat but
whether that works to decrease drag by reducing the viscosity of the
water or by reducing the wetted area I don't know.

That could be both.

Air cushion is definitely a factor in many designs but I am not sure that it's
the primary factor in multiple chines. Seems I read somewhere that multiple
chines was to increase lift at various speeds until the boat is at optimum
cruising speed. Basically the multiple chines help it come out of the hole
faster. I seem to recall and I think you mentioned it in passing earlier in
this thread that it also helps with stability and steering control. If you
have ever run a flat bottom boat that is adequately powered I'm sure you
know that it planes out almost immediately. The way it was explained to me
is that multiple chines are a compromise. Gives you more lift like a flat
bottom, but as they come out of the water they cease to create drag.

Now I'm tempted to start a whole new thread on air cushion designs.
Tunnels. Twin tunnels. The big M shape of the front 1/3 to 1/2 of many of
those modified V-Pad bottom boats. We could talk about lift, cavitation,
kiting, Miss Budweiser doing end over end flips, LOL. My experience with
tunnels is more limited, but I did have a Baker Custom Boats twin tunnel for
a few years. Awesome ride in light chop.

I think we can both agree that the less boat you have in the water (in
general) the faster it will go.

** Thought I better throw this in: **
Chine walk can be deadly scary in such a boat if not properly setup or if
driven by somebody who hasn't taken the time to learn to drive their rig.
The biggest safety move for anybody else reading this is to SLOW DOWN
gradually. A sudden loss of throttle can be almost as dangerous.
Especially in traffic in a busy system. Increase power (like I did) and
it's a whole new rig to learn to drive.

Left that last bit in because it bears repeating.

Bob La Londe
www.YumaBassMan.com

"Bruce In Bangkok" wrote in message
...
On Sat, 12 Dec 2009 14:01:13 -0700, "Bob La Londe"
wrote:

"Bruce In Bangkok" wrote in message
. ..
On Fri, 11 Dec 2009 20:44:31 -0700, "Bob La Londe"
wrote:

"Bruce In Bangkok" wrote in message
m...

I wish that you could point me at a url showing this "speed pad" as I
can't seem to visualize it, nor can I find more then the words, i.e.,
has a speed pad. I am somewhat familiar with the hulls of both three
point hulls (the old speed boat hulls with the sponsons) and more
modern open ocean racing stuff, but the speed pad defeats me


Most modern high performance fiberglass bass boats made today have a pad
style bottom atleast to some degree. Fast Cat (tunnel) and a few
shallow
V
and pocket tunnel flats boats being the exceptions.

http://www.bwbmag.com/output.cfm?id=1122481 "When we think of a bass
boat,
we typically envision a modified V hull, with a pad bottom, and more
often
than not, an extended transom/built-in jackplate. Pretty cool stuff,
right?
"

Kinda goes to the argument that it's a pretty common thing if that's
what
"we typically envision."

Here is an aluminum one, but I do not like their design. Most are
flatter,
although a lot of Rangers have a semi V pad like that. I mostly do not
like
the sandwiched or layer construction for aluminum as it can trap water.
Their V pad might be the most efficient design for some setups, or
possibley
the best compromise: http://www.freepatentsonline.com/6666162.html

Here is a picture of the inside the hull for one under construction.
The
outside view would be much more defined.
http://media.photobucket.com/image/b...lassonhull.jpg

I am finding that there is an amazing dearth of pictures online of the
bottom of bass boats. I am finding myself headed out to the shop to
take
pictures of the bottom of my Basscat.

Here is a view from the transom:
http://www.yumabassman.com/pictures/shelf-001.gif

O.K. I see what you are talking about now. Essentially a flat bottomed
boat once you reach the optimum speed.


Essentially. Yes. A narrow flat bottom boat. Low resistance and tends
to
put motive force towards going forward rather than up. Speed and power
available being major factors of course.

I do not have the math skills or the engineering background to explain it
all, but I think it works like this. The narrow pad creates less
resistance
than a V of similar surface area within the displacement envelope
primarily,
but not exclusively because of the surface tension of the water. There
are
other other forces such as angle of pressure, total pressure against
forward
movement etc. The idea is the boat comes up and then flattens out. The
edge of the pad will break the surface tension of the water and shed the
water much more quickly than than a straight V will, and it will have less
surface area touching the water than a shallower V design or than a flat
bottom boat. More of the extra power is used to push the boat forward
rather than to lift the boat out of the water. I discovered this first
hand
when I went from a 225 (around 215-220 HP) to a 250 Pro XS (260-270 HP) on
the boat I pictured. At 70+ I need less trim angle than I did at 68
(WOT)
with the old motor.

As speed increases water pressure against the bottom of the boat
increases and increases lift (if that is what you want to term the
force acting against the bottom of the boat). If "X" lifting force is
applied to a flat surface, at 90 degrees to the force, the entire
force is applied to the surface at 90 degrees to the surface. If the
same force is applied to a surface at other then 90 degrees only a
part of the force will be applied at 90 degrees to the surface. Thus
the same lift, derived from forward speed,applied to a vee hull will
result in less force being applied to raise the boat "up" then if the
same lifting force applied to a flat surface.

This has been bouncing around in my head as well since you forced me to
think a little more. The reason I think a sharp edge is more efficient is
basically the same as why a pad is more efficient at optimum speeds. The
sharper edge will break the surface tension and shed water weight and
reduce
resistance much sooner than a rounded edge. The average boater will never
notice the difference, but guys who are always running on the ragged edge
(oxymoron not intended) and looking for the best performing prop to run
right at redline will notice the extra 1 or 2 miles per hour.

Rather then "surface tension" I suspect (if the effect is not large)
that it is simply a matter of surface area. Exactly the same reason
that the small flat bottom is faster then a vee. At any speed it would
take more "lift" to raise an inclined (vee) surface then one at right
angles to the force, thus any rounded corner would act much the same
as the vee, for that portion of the pad, and reduce total lifting
force, by some percentage.

However.... I have read that the multiple, sharp edged, chine designs
actually increase speed because the sharp edged chines increase the
amount of air that is trapped and forced to flow under the boat but
whether that works to decrease drag by reducing the viscosity of the
water or by reducing the wetted area I don't know.

Several designs do trap air by a number of methods. One you see that is
fairly common is that they make the front portion of the boat in a big
rounded M if you were to cut it in cross section about 1/3 back. My Bass
cat kinda has that look also. Lots of boats do. It certainly works well
towards eliminating spray over the bow. The guys at Basscat have even
warned me that excessive trim can cause the boat to kite with a net effect
similar to chine walk. This is caused by air though rather than the falling
off due to balance or prop torque like regular chine walk.

I am sure multiple chines do something as lots of designers use them. I
always thought it was for stability and steering control at various speeds.
Also to increase lift at a particular speed from the flat bottom of the
individual chines. I suppose they could trap some air also, but I don't
think that is the primary reason for them.

There are some tunnel hull designs that do a much better job of providing
air cushion. One I had the chance to play with for a couple years was a
Baker twin tunnel made by Baker Custom Boats. It was another 20 footer but
only had an EFI 200 on it. It would consistently run right at 65 GPS
**regardless of the load (within reason)**. The basic setup was about 500
pounds heavier than my Basscat. Since the Basscat was originally powered
with a much more modern 225 and only ran 3-5 MPH faster that is saying
something. Can't really compare since I put the bigger motor on the kitten
now. The big problem with tunnels is the extra weight and lost flotation
for similar durability of construction. No big deal when you are running
flat out, but makes a difference when sitting still and fishing or running
water to rough to run flat out. None of the boats I have direct experience
with are paper thin, shave every ounce, race boats.

I wish I still had the Baker for the sake of this conversation, because if I
recall correctly the center hull/deflector also was kind of a pad design.
It was the best handling boat I have ever driven at speed. It steered like
a car at any speed above idle.

As a side note. The tunnel hull took light chop a lot smoother at speed
than any of the pad bottom modified Vs, but when it gets rough the pad-V can
slow down a little and run like a V hull. The tunnel has to stay on the
high end of its speed range and run wave top to wave top hoping not to spear
one, or find safe harbor.

Everything is a compromise.

Anyway... I guess its time to start doing some basic math and figuring out
the weight of my theoretical sharp pad aluminum pad-v. LOL. Who knows. I
might build it someday.

Its late. I know I'm gonna look at this post tommorrow and wonder... what
was I thinking. LOL.

Bob La Londe
www.YumaBassMan.com

In article , says...

"Bruce In Bangkok" wrote in message
...
On Sat, 12 Dec 2009 14:01:13 -0700, "Bob La Londe"
wrote:

"Bruce In Bangkok" wrote in message
. ..
On Fri, 11 Dec 2009 20:44:31 -0700, "Bob La Londe"
wrote:

"Bruce In Bangkok" wrote in message
m...

I wish that you could point me at a url showing this "speed pad" as I
can't seem to visualize it, nor can I find more then the words, i.e.,
has a speed pad. I am somewhat familiar with the hulls of both three
point hulls (the old speed boat hulls with the sponsons) and more
modern open ocean racing stuff, but the speed pad defeats me


Most modern high performance fiberglass bass boats made today have a pad
style bottom atleast to some degree. Fast Cat (tunnel) and a few
shallow
V
and pocket tunnel flats boats being the exceptions.

http://www.bwbmag.com/output.cfm?id=1122481 "When we think of a bass
boat,
we typically envision a modified V hull, with a pad bottom, and more
often
than not, an extended transom/built-in jackplate. Pretty cool stuff,
right?
"

Kinda goes to the argument that it's a pretty common thing if that's
what
"we typically envision."

Here is an aluminum one, but I do not like their design. Most are
flatter,
although a lot of Rangers have a semi V pad like that. I mostly do not
like
the sandwiched or layer construction for aluminum as it can trap water.
Their V pad might be the most efficient design for some setups, or
possibley
the best compromise: http://www.freepatentsonline.com/6666162.html

Here is a picture of the inside the hull for one under construction.
The
outside view would be much more defined.
http://media.photobucket.com/image/b...lassonhull.jpg

I am finding that there is an amazing dearth of pictures online of the
bottom of bass boats. I am finding myself headed out to the shop to
take
pictures of the bottom of my Basscat.

Here is a view from the transom:
http://www.yumabassman.com/pictures/shelf-001.gif

O.K. I see what you are talking about now. Essentially a flat bottomed
boat once you reach the optimum speed.


Essentially. Yes. A narrow flat bottom boat. Low resistance and tends
to
put motive force towards going forward rather than up. Speed and power
available being major factors of course.

I do not have the math skills or the engineering background to explain it
all, but I think it works like this. The narrow pad creates less
resistance
than a V of similar surface area within the displacement envelope
primarily,
but not exclusively because of the surface tension of the water. There
are
other other forces such as angle of pressure, total pressure against
forward
movement etc. The idea is the boat comes up and then flattens out. The
edge of the pad will break the surface tension of the water and shed the
water much more quickly than than a straight V will, and it will have less
surface area touching the water than a shallower V design or than a flat
bottom boat. More of the extra power is used to push the boat forward
rather than to lift the boat out of the water. I discovered this first
hand
when I went from a 225 (around 215-220 HP) to a 250 Pro XS (260-270 HP) on
the boat I pictured. At 70+ I need less trim angle than I did at 68
(WOT)
with the old motor.

As speed increases water pressure against the bottom of the boat
increases and increases lift (if that is what you want to term the
force acting against the bottom of the boat). If "X" lifting force is
applied to a flat surface, at 90 degrees to the force, the entire
force is applied to the surface at 90 degrees to the surface. If the
same force is applied to a surface at other then 90 degrees only a
part of the force will be applied at 90 degrees to the surface. Thus
the same lift, derived from forward speed,applied to a vee hull will
result in less force being applied to raise the boat "up" then if the
same lifting force applied to a flat surface.

This has been bouncing around in my head as well since you forced me to
think a little more. The reason I think a sharp edge is more efficient is
basically the same as why a pad is more efficient at optimum speeds. The
sharper edge will break the surface tension and shed water weight and
reduce
resistance much sooner than a rounded edge. The average boater will never
notice the difference, but guys who are always running on the ragged edge
(oxymoron not intended) and looking for the best performing prop to run
right at redline will notice the extra 1 or 2 miles per hour.

Rather then "surface tension" I suspect (if the effect is not large)
that it is simply a matter of surface area. Exactly the same reason
that the small flat bottom is faster then a vee. At any speed it would
take more "lift" to raise an inclined (vee) surface then one at right
angles to the force, thus any rounded corner would act much the same
as the vee, for that portion of the pad, and reduce total lifting
force, by some percentage.

However.... I have read that the multiple, sharp edged, chine designs
actually increase speed because the sharp edged chines increase the
amount of air that is trapped and forced to flow under the boat but
whether that works to decrease drag by reducing the viscosity of the
water or by reducing the wetted area I don't know.

Several designs do trap air by a number of methods. One you see that is
fairly common is that they make the front portion of the boat in a big
rounded M if you were to cut it in cross section about 1/3 back. My Bass
cat kinda has that look also. Lots of boats do. It certainly works well
towards eliminating spray over the bow. The guys at Basscat have even
warned me that excessive trim can cause the boat to kite with a net effect
similar to chine walk. This is caused by air though rather than the falling
off due to balance or prop torque like regular chine walk.

I am sure multiple chines do something as lots of designers use them. I
always thought it was for stability and steering control at various speeds.
Also to increase lift at a particular speed from the flat bottom of the
individual chines. I suppose they could trap some air also, but I don't
think that is the primary reason for them.

There are some tunnel hull designs that do a much better job of providing
air cushion. One I had the chance to play with for a couple years was a
Baker twin tunnel made by Baker Custom Boats. It was another 20 footer but
only had an EFI 200 on it. It would consistently run right at 65 GPS
**regardless of the load (within reason)**. The basic setup was about 500
pounds heavier than my Basscat. Since the Basscat was originally powered
with a much more modern 225 and only ran 3-5 MPH faster that is saying
something. Can't really compare since I put the bigger motor on the kitten
now. The big problem with tunnels is the extra weight and lost flotation
for similar durability of construction. No big deal when you are running
flat out, but makes a difference when sitting still and fishing or running
water to rough to run flat out. None of the boats I have direct experience
with are paper thin, shave every ounce, race boats.

I wish I still had the Baker for the sake of this conversation, because if I
recall correctly the center hull/deflector also was kind of a pad design.
It was the best handling boat I have ever driven at speed. It steered like
a car at any speed above idle.

As a side note. The tunnel hull took light chop a lot smoother at speed
than any of the pad bottom modified Vs, but when it gets rough the pad-V can
slow down a little and run like a V hull. The tunnel has to stay on the
high end of its speed range and run wave top to wave top hoping not to spear
one, or find safe harbor.

Everything is a compromise.

Anyway... I guess its time to start doing some basic math and figuring out
the weight of my theoretical sharp pad aluminum pad-v. LOL. Who knows. I
might build it someday.

Its late. I know I'm gonna look at this post tommorrow and wonder... what
was I thinking. LOL.

Bob La Londe
www.YumaBassMan.com



The article I read years ago studied the air that runs along the dozens
of chines on the old Viking ships. The theory was that as the boat moved
through the water, air bubbles would get trapped along the angles formed
by the lap strake type construction.