## peas

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• Most of you will have seen this already. http://apci.net/~michalak/ If not, do check it out. In particular, if you ve heard me rambling about the seas of
Message 1 of 3 , Apr 1, 2000
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Most of you will have seen this already. http://apci.net/~michalak/

If not, do check it out.

In particular, if you've heard me rambling about the 'seas of peas' theory
in the past, and wondered what on Earth I was gibbering about, this is an
opportunity to find out more.

And any ideas why these boats should be so fast? Could it be that the old
speed/length rule just doesn't apply, and these boats plane or semi plane in
a very smooth way that's actually not at all obvious when it happens?

Cheers,

Gav
• This may be heresy..... I would like to see (or hear) the Bolger sharpie-shape theory discussed in its most complete form. Bolger is capable of both subtle
Message 2 of 3 , Apr 3, 2000
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This may be heresy.....

I would like to see (or hear) the Bolger sharpie-shape theory
discussed in its most complete form. Bolger is capable of both subtle
thought and pedantic simplification, so I am reluctant take issue
with him based on the short, simple explanations that he has put in
articles.

However...

The proposition that the curve of the sides (i.e. angle of entry of
the side) should match the curve of the bottom (i.e. angle of entry
of the bottom) BECAUSE then the bottom pushes water down equally as
the sides push water out seems to me to be flawed. Water under the
boat is constrained because water can not be compressed. Water on the
side of the boat can be forced upward. It seems to me that the Bolger
Box form leads to higher pressure under the boat than on the sides.

According to the Bolger Theory, this is desireable because it means
water passes around the chine only in the bottom-to-side direction
and not in the higher drag side-to-bottom direction.

I do believe that he has proved on the water that the Bolger Box
makes a superior boat in practice.

Now, the question of why Bolger Boxes can be capable of high speeds.
(Not that I believe in an 8kt Micro.) I think it is because of
Bolger's oft repeated observation that a shallow boat can not make a
deep wave. I will have to post my complete line of thought sometime,
but the jist is this:

The forward part of a boat depresses the water surface. As the boat
goes by, water pressure pushes the surface back to the equilibrium
level. (This pressure is set by the density of water, and is
independant of boat length and speed.) If the water is not pushed up
quickly enough to support the aft section of the boat, the stern
falls, the boat gets out of trim and resistance increases. The boat
has reached 'hull speed.' If the water is pushed up quickly, the boat
stays in trim, resistance does not rise, and the boat can accelerate.

It seems obvious that shorter the distance the water is displaced,
the quicker it can rise to support the stern of the boat, and the
faster the boat can go before it reaches hull speed. The Square Boats
displace the surface about the smallest amount of any shape of boat,
which may explain why they can generate unexpectedly high top speeds.

Peter
• This may be heresy..... I would like to see (or hear) the Bolger sharpie-shape theory discussed in its most complete form. Bolger is capable of both subtle
Message 3 of 3 , Apr 3, 2000
• 0 Attachment
This may be heresy.....

I would like to see (or hear) the Bolger sharpie-shape theory
discussed in its most complete form. Bolger is capable of both subtle
thought and pedantic simplification, so I am reluctant take issue
with him based on the short, simple explanations that he has put in
articles.

However...

The proposition that the curve of the sides (i.e. angle of entry of
the side) should match the curve of the bottom (i.e. angle of entry
of the bottom) BECAUSE then the bottom pushes water down equally as
the sides push water out seems to me to be flawed. Water under the
boat is constrained because water can not be compressed. Water on the
side of the boat can be forced upward. It seems to me that the Bolger
Box form leads to higher pressure under the boat than on the sides.

According to the Bolger Theory, this is desireable because it means
water passes around the chine only in the bottom-to-side direction
and not in the higher drag side-to-bottom direction.

I do believe that he has proved on the water that the Bolger Box
makes a superior boat in practice.

Now, the question of why Bolger Boxes can be capable of high speeds.
(Not that I believe in an 8kt Micro.) I think it is because of
Bolger's oft repeated observation that a shallow boat can not make a
deep wave. I will have to post my complete line of thought sometime,
but the jist is this:

The forward part of a boat depresses the water surface. As the boat
goes by, water pressure pushes the surface back to the equilibrium
level. (This pressure is set by the density of water, and is
independant of boat length and speed.) If the water is not pushed up
quickly enough to support the aft section of the boat, the stern
falls, the boat gets out of trim and resistance increases. The boat
has reached 'hull speed.' If the water is pushed up quickly, the boat
stays in trim, resistance does not rise, and the boat can accelerate.

It seems obvious that shorter the distance the water is displaced,
the quicker it can rise to support the stern of the boat, and the
faster the boat can go before it reaches hull speed. The Square Boats
displace the surface about the smallest amount of any shape of boat,
which may explain why they can generate unexpectedly high top speeds.

Peter
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