## Re: [Michalak] Re: Twin Leeboards

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• Graeme..... I do not understand it at all yet, but, the guy seems to have studied it inside out....today s Duckworks Mag.
Message 1 of 28 , Apr 1, 2013
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Graeme..... I do not understand it at all yet, but, the guy seems to have studied it inside out....today's Duckworks Mag. http://www.duckworksmagazine.com/13/howto/propulsion/index.htm#.UVmryr4o5LM appears to be calculating a way for the underwater foils....specifically the leeboard....to produce propulsion.....???? I will not comment until I can understand....grok..
JIB
---------- Original Message ----------
From: "graeme" <graeme19121984@...>
To: Michalak@yahoogroups.com
Subject: [Michalak] Re: Twin Leeboards
Date: Mon, 01 Apr 2013 06:49:07 -0000

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd">

It can take a lot of concentration to visualise how the angle of toe-in changes as those leeboards are appropriately raked from aft to fully down to suit the point of sail. Probably a model would help.

One thing not shown there is that the mount faces slope sort of wedge or cam-like... think of a short wide solid cylinder - a thick round block. Ok? To make a leeboard mount that changes the relative toe-in through a 0 to 2 or 4deg angle with rotation up or down from being parallel with the boat longitudinal centreline slice the block in half to make two round blocks only slope the slice a little. When the two blocks are rotated relative to each other the two inner sloping mating faces then will cause the outer block faces to change angle. The blocks don't have to necessarily be round. The original Dutch way I believe is to have that "slope" shaped by carving it into the top of the leeboard mounting face - not a lot of trouble considering how well the rest of the board is similarly shaped by carving. I've seen drawings of the block type mounts though, one attached to the side and it's mate to the leeboard. The pin or shaft, like the hole for the shaft, goes through the lot in a straight line (board, blocks, side, plank) that in plan and elevation views is straight but of course in end elevation view (body plan) for the Dutch boat types it has an angle normal (90deg right angle) to the slope of the tumblehome plank.

http://www.duckworksbbs.com/media/books/barend/index.htm

http://www.punterwerf.nl/

Graeme

--- In Michalak@yahoogroups.com, "jhargrovewright2@..." <jhargrovewright2@...> wrote:
> Life is good.Thank you for re orienting me to the leeboard tow in/out and the canting of the Dutch boats. You linked to a great site http://www.duckworksmagazine.com/01/articles/leeboards/index.htm You and he have convinced me " boards must have camber, caster and toe-in ".
> It took me a long time today to get through your post and the links. You have made me rethink the whole question. My canoe will be even better, thanks! JIB

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• Did you notice the date, John? On Mon, Apr 1, 2013 at 10:53 AM, jhargrovewright2@juno.com
Message 2 of 28 , Apr 1, 2013
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Did you notice the date, John?

On Mon, Apr 1, 2013 at 10:53 AM, jhargrovewright2@... <
jhargrovewright2@...> wrote:

> Graeme..... I do not understand it at all yet, but, the guy seems to have
> studied it inside out....today's Duckworks Mag.
> http://www.duckworksmagazine.com/13/howto/propulsion/index.htm#.UVmryr4o5LMappears to be calculating a way for the underwater foils....specifically
> the leeboard....to produce propulsion.....???? I will not comment until I
> can understand....grok..
> JIB
>

[Non-text portions of this message have been removed]
• Anders, I am not sure I understand the question....it is today s article in Duckworks Mag. Did you try the link? JIB ... From: Anders Bjorklund
Message 3 of 28 , Apr 1, 2013
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Anders, I am not sure I understand the question....it is today's article in Duckworks Mag. Did you try the link? JIB

---------- Original Message ----------
From: Anders Bjorklund <andersbjorklund5@...>
To: Michalak <Michalak@yahoogroups.com>
Subject: Re: [Michalak] Re: Twin Leeboards
Date: Mon, 1 Apr 2013 18:22:15 -0500

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd">
Did you notice the date, John?

On Mon, Apr 1, 2013 at 10:53 AM, jhargrovewright2@... <
jhargrovewright2@...> wrote:

> Graeme..... I do not understand it at all yet, but, the guy seems to have
> studied it inside out....today's Duckworks Mag.
> http://www.duckworksmagazine.com/13/howto/propulsion/index.htm#.UVmryr4o5LMappears to be calculating a way for the underwater foils....specifically
> the leeboard....to produce propulsion.....???? I will not comment until I
> can understand....grok..
> JIB
>

[Non-text portions of this message have been removed]

[Non-text portions of this message have been removed]
• 50% smoke
Message 4 of 28 , Apr 1, 2013
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50% smoke

--- In Michalak@yahoogroups.com, "jhargrovewright2@..."
> Graeme..... I do not understand it at all yet, but, the guy seems to have studied it inside out....
• The date of today s Duckworks article? April 1? No one noticed? On Mon, Apr 1, 2013 at 8:53 PM, jhargrovewright2@juno.com
Message 5 of 28 , Apr 1, 2013
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The date of today's Duckworks article? April 1? No one noticed?

On Mon, Apr 1, 2013 at 8:53 PM, jhargrovewright2@... <
jhargrovewright2@...> wrote:

> Anders, I am not sure I understand the question....it is today's article
> in Duckworks Mag. Did you try the link? JIB

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• Ha !! It s April 2 already here obscured by the smoke haze fazed.
Message 6 of 28 , Apr 1, 2013
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Ha !! It's April 2 already here obscured by the smoke haze fazed.

--- In Michalak@yahoogroups.com, Anders Bjorklund <andersbjorklund5@...> wrote:
>
> The date of today's Duckworks article? April 1? No one noticed?
• Anders, Thanks, you saved me some time. I was very busy yesterday so I printed it out so that I could read and study it....because I could not follow it. I
Message 7 of 28 , Apr 2, 2013
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Anders, Thanks, you saved me some time. I was very busy yesterday so I printed it out so that I could read and study it....because I could not follow it. I can study something difficult much easier if it is on paper. I picked it up this morning while fresh, to read it...... and realized I HAD BEEN HAD! JOKE ON ME. On the yahoo proa group there are a couple of members that are very hard to follow and have a lot of education and training in aerodynamics, engineering......so I save it and print it out then read and re read until it makes sense..... Dyslexia is a curse and a blessing. JIB
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd"> The date of today's Duckworks article? April 1? No one noticed?

On Mon, Apr 1, 2013 at 8:53 PM, jhargrovewright2@... <
jhargrovewright2@...> wrote:

> Anders, I am not sure I understand the question....it is today's article
> in Duckworks Mag. Did you try the link? JIB

[Non-text portions of this message have been removed]

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• I had twin air-foiled lee boards on my PCB Black Skimmer, i used the pivots that Phil used on Black Gauntlet with 1 degree toe-in. I also added a bow dagger
Message 8 of 28 , Apr 4, 2013
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I had twin air-foiled lee boards on my PCB Black Skimmer, i used the pivots
that Phil used on Black Gauntlet with 1 degree toe-in. I also added a bow
dagger board for beating in shallow water. She pointed very high so long as
i sailed her as flat as possible. Tim P Anderson Swamp Dwelling Boat
Builder

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• Tim Anderson... I admire the Black Skimmer and the information. What swamp do you reside in? Can you add any comments experience with the bow dagger board.
Message 9 of 28 , Apr 4, 2013
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Tim Anderson... I admire the Black Skimmer and the information. What swamp do you reside in? Can you add any comments experience with the bow dagger board. That is an unusual place for a foil and I wonder how and why Bolger came up with that arrangement. Any info would be appreciated. JIB

---------- Original Message ----------
From: Tim Anderson <naturalist71261@...>
To: Michalak@yahoogroups.com
Subject: [Michalak] Re: Twin Leeboards
Date: Thu, 4 Apr 2013 15:47:55 -0500

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd">
I had twin air-foiled lee boards on my PCB Black Skimmer, i used the pivots
that Phil used on Black Gauntlet with 1 degree toe-in. I also added a bow
dagger board for beating in shallow water. She pointed very high so long as
i sailed her as flat as possible. Tim P Anderson Swamp Dwelling Boat
Builder

[Non-text portions of this message have been removed]

[Non-text portions of this message have been removed]
• I had a Dovekie with a bow centerboard. It worked fine in shallow water. It somewhat offset the lee helm which developed when I reefed. However, if you are in
Message 10 of 28 , Apr 4, 2013
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I had a Dovekie with a bow centerboard. It worked fine in shallow water. It
somewhat offset the lee helm which developed when I reefed. However, if you
are in the habit of heading up in a puff, be aware that the bow centerboard
will resist heading up-best to ease the sheet.

JohnT

_____

From: Michalak@yahoogroups.com [mailto:Michalak@yahoogroups.com] On Behalf
Of jhargrovewright2@...
Sent: Thursday, April 04, 2013 6:18 PM
To: Michalak@yahoogroups.com
Subject: Re: [Michalak] Re: Twin Leeboards

Tim Anderson... I admire the Black Skimmer and the information. What swamp
do you reside in? Can you add any comments experience with the bow dagger
board. That is an unusual place for a foil and I wonder how and why Bolger
came up with that arrangement. Any info would be appreciated. JIB

---------- Original Message ----------
From: Tim Anderson <naturalist71261@...
<mailto:naturalist71261%40gmail.com> >
To: Michalak@yahoogroups.com <mailto:Michalak%40yahoogroups.com>
Subject: [Michalak] Re: Twin Leeboards
Date: Thu, 4 Apr 2013 15:47:55 -0500

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN"
"http://www.w3.org/TR/html4/strict.dtd">
I had twin air-foiled lee boards on my PCB Black Skimmer, i used the pivots
that Phil used on Black Gauntlet with 1 degree toe-in. I also added a bow
dagger board for beating in shallow water. She pointed very high so long as
i sailed her as flat as possible. Tim P Anderson Swamp Dwelling Boat
Builder

[Non-text portions of this message have been removed]

[Non-text portions of this message have been removed]

[Non-text portions of this message have been removed]
• Jim drew a design called Eisbox that had a bow centreboard installed in the free-flooding bow well as an option. There is a cartoon in the files section. The
Message 11 of 28 , Apr 5, 2013
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Jim drew a design called "Eisbox" that had a bow centreboard installed
in the free-flooding bow well as an option. There is a cartoon in the
files section.

The idea was to lower it enough in shallow water to help prevent lee
helm as the leeboard was raised. Very simple to add as you don't have to
free-flooding well, so it can be a very shallow rectangular box open at
the top. The board is in the shape of a quarter circle about 18" in
diameter. Just needs some weight added so it stays down and a control
at the bow and then back to the helm to raise it to the desired height
and locked into a jam cleat.

Eisbox has a 5 ft. deep leeboard so as it is raised in shallows will
quite likely introduce lee helm and spoil upwind capability. So as the
leeboard is raised you lower the bow board and hopefully maintain a
neutral balance at the helm by adjusting both boards as you go along.
The only thing is that you are restricted to 6" draft on Eisbox as it
has a skeg ahead of the inboard rudder to protect it - which Jim doesn't
like all that much - but the fellow who commissioned it insisted on as
he wanted the OB to be mounted on the centreline. It was intended to
motor more than sail in the purpose he wanted a boat for. He wanted to
motor out offshore to fish when the winds were normally too low to sail
and sail back home when the on-shore breeze arose in the afternoon.

So a fellow like JIB might be interested in this information if used in
hull with less draft than Eisbox and likes to sail in the shallows?

Nels

--- In Michalak@yahoogroups.com, "John Trussell" <jtrussell2@...> wrote:
>
> I had a Dovekie with a bow centerboard. It worked fine in shallow
water. It
> somewhat offset the lee helm which developed when I reefed. However,
if you
> are in the habit of heading up in a puff, be aware that the bow
centerboard
> will resist heading up-best to ease the sheet.
>
>
>
> JohnT
>
>
>

[Non-text portions of this message have been removed]
• Nels, I was not familiar with Eisbox. Interesting boat. I did not find any info on the bow centerboard but have thought about the effects/uses that it might
Message 12 of 28 , Apr 6, 2013
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Nels, I was not familiar with Eisbox. Interesting boat. I did not find any info on the bow centerboard but have thought about the effects/uses that it might have. I think I understand the purpose and function balancing the boat in shallow water....Clever. I prefer to set up my boats with significant weather helm and rely on the rudder for a good portion of the LR.... I am just as careful building the rudder as the leeboard. I may do a centerboard again but, that is not on the list yet... Thanks for the information. That bow centerboard device has long been a mystery to me. Thanks, you have expanded my understanding of the sailboat, again.,,, I do love to sail in shallow water. At the Texas200 a couple of years ago in my Laguna....I stood on the bow of the boat....in the shade of the forward sail and followed the Matagorda Bay shore in 6" to 1' water sneaking up on the fish and other creature of the shallows. Interesting was that in displacement mode in 5"-6" the boat created a significant breaking 1/4 wave following off the transom. I was running directly down wind (10 mph) and did not have the push needed to plane. JIB
--------------
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd"> Jim drew a design called "Eisbox" that had a bow centreboard installed
in the free-flooding bow well as an option. There is a cartoon in the
files section.

The idea was to lower it enough in shallow water to help prevent lee
helm as the leeboard was raised. Very simple to add as you don't have to
free-flooding well, so it can be a very shallow rectangular box open at
the top. The board is in the shape of a quarter circle about 18" in
diameter. Just needs some weight added so it stays down and a control
at the bow and then back to the helm to raise it to the desired height
and locked into a jam cleat.

Eisbox has a 5 ft. deep leeboard so as it is raised in shallows will
quite likely introduce lee helm and spoil upwind capability. So as the
leeboard is raised you lower the bow board and hopefully maintain a
neutral balance at the helm by adjusting both boards as you go along.
The only thing is that you are restricted to 6" draft on Eisbox as it
has a skeg ahead of the inboard rudder to protect it - which Jim doesn't
like all that much - but the fellow who commissioned it insisted on as
he wanted the OB to be mounted on the centreline. It was intended to
motor more than sail in the purpose he wanted a boat for. He wanted to
motor out offshore to fish when the winds were normally too low to sail
and sail back home when the on-shore breeze arose in the afternoon.

So a fellow like JIB might be interested in this information if used in
hull with less draft than Eisbox and likes to sail in the shallows?

Nels

--- In Michalak@yahoogroups.com, "John Trussell" <jtrussell2@...> wrote:
>
> I had a Dovekie with a bow centerboard. It worked fine in shallow
water. It
> somewhat offset the lee helm which developed when I reefed. However,
if you
> are in the habit of heading up in a puff, be aware that the bow
centerboard
> will resist heading up-best to ease the sheet.
>
>
>
> JohnT
>
>
>

[Non-text portions of this message have been removed]

[Non-text portions of this message have been removed]
• As well as Dovekie and Black Skimmer Bolger added a bow board to his Whalewatcher for the same reasons - to help with helm balance. Bolger also tried to
Message 13 of 28 , Apr 6, 2013
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As well as Dovekie and Black Skimmer Bolger added a bow board to his
Whalewatcher for the same reasons - to help with helm balance.

Bolger also tried to develop a bow steering design, based I think on ice
boats? So a bow board you could adjust a bit to port or starboard would
probably be interesting like toed in or out with leeboards. I think the
control mechanisms quickly become complicated for the small gains in
performance. I think at planing speeds a bow board should be raised.

Nels
--- In Michalak@yahoogroups.com, "jhargrovewright2@..."
<jhargrovewright2@...> wrote:
>
> Nels, I was not familiar with Eisbox. Interesting boat. I did not
find any info on the bow centerboard but have thought about the
effects/uses that it might have. I think I understand the purpose and
function balancing the boat in shallow water....Clever. I prefer to
set up my boats with significant weather helm and rely on the rudder for
a good portion of the LR.... I am just as careful building the rudder
as the leeboard. I may do a centerboard again but, that is not on the
list yet... Thanks for the information. That bow centerboard device
has long been a mystery to me. Thanks, you have expanded my
understanding of the sailboat, again.,,, I do love to sail in shallow
water. At the Texas200 a couple of years ago in my Laguna....I stood on
the bow of the boat....in the shade of the forward sail and followed the
Matagorda Bay shore in 6" to 1' water sneaking up on the fish and other
creature of the shallows. Interesting was that in displacement mode in
5"-6" the boat created a significant breaking 1/4 wave following off the
transom. I was running directly down wind (10 mph) and did not have the
push needed to plane. JIB

[Non-text portions of this message have been removed]
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