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• I was reading Bolger s essay on the Sprit Rig and the final sentence reads: It s usually wise to use no lead on the center of the sail area ahead of the
Jun 16 1 of 5
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I was reading Bolger's essay on the Sprit Rig and the final sentence
reads:

"It's usually wise to use no lead on the center of the sail area ahead
of the quarter-chord of the lateral plane, at least if the lateral plane
is a well-defined fin like a centerboard or leeboard."

I think I know what lead means but have no idea what "the quarter-chord
of the lateral plane" means.

Nels

[Non-text portions of this message have been removed]
• Nels, Chord on an airfoil section is the leading-edge-to-trailing-edge distance.  The quarter-chord line on an airfoil surface is a line along the span that
Jun 16 1 of 5
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Nels,

Chord on an airfoil section is the leading-edge-to-trailing-edge distance.  The quarter-chord line on an airfoil surface is a line along the span that is 25% of the chord aft of the leading edge.  So on an untapered leeboard that is 12" wide the quarter chord line would be 3" aft of the leading edge and parallel to both the LE and the TE.  The quarter-chord line corresponds to the theoretical center of lift.

Bolger is saying that on a boat with a very shallow hull (such as a canoe or sharpie) where the bulk of the effective lateral plane is in a well-defined foil such as a leeboard, one can disregard the hull and consider just the leeboard for determining leeboard location vs the rig.  This is very close to Michalak's practice of (if I recall correctly) lining up the LE of the leeboard with the center of area of the rig.

-- Sam

________________________________
From: prairiedog2332 <nelsarv@...>
To: Michalak@yahoogroups.com
Sent: Sunday, June 16, 2013 11:47 AM
Subject: [Michalak] Translation Please

I was reading Bolger's essay on the Sprit Rig and the final sentence
reads:

"It's usually wise to use no lead on the center of the sail area ahead
of the quarter-chord of the lateral plane, at least if the lateral plane
is a well-defined fin like a centerboard or leeboard."

I think I know what lead means but have no idea what "the quarter-chord
of the lateral plane" means.

Nels

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

[Non-text portions of this message have been removed]
• here i am speculating: the quarter chord of a 12 wide centerboard (assuming a vertical board) would be 3 , so dont put the ce forward of 3 behind the
Jun 16 1 of 5
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here i am speculating: the quarter chord of a 12" wide centerboard (assuming a vertical board) would be 3" , so dont put the ce forward of 3"
behind the leading edge of said board. or suffer lee helm. just speculating : )

To: Michalak@yahoogroups.com
From: nelsarv@...
Date: Sun, 16 Jun 2013 15:47:03 +0000
Subject: [Michalak] Translation Please

I was reading Bolger's essay on the Sprit Rig and the final sentence
reads:

"It's usually wise to use no lead on the center of the sail area ahead
of the quarter-chord of the lateral plane, at least if the lateral plane
is a well-defined fin like a centerboard or leeboard."

I think I know what lead means but have no idea what "the quarter-chord
of the lateral plane" means.

Nels

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

[Non-text portions of this message have been removed]
• Thanks Dan and Sam! Somehow I expected it to be far more complicated that that:-) Why can t those navel architects say what they mean in plain English? (Just
Jun 17 1 of 5
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Thanks Dan and Sam!
Somehow I expected it to be far more complicated that that:-) Why can't
those navel architects say what they mean in plain English? (Just
kidding Sam)

Bolger does seem to also suggest that a boomless sail has more of a
tendency towards weather helm than one with a boom and a sprit sail is
generally boomless, so perhaps why the CE or mast should be a bit
further aft. His essays on the sprit rig are important reading in my
opinion as that rig attracts a lot of interest for a small hull designed
for paddling or rowing.

Nels

--- In Michalak@yahoogroups.com, daniel brown wrote:
>
> here i am speculating: the quarter chord of a 12" wide centerboard
(assuming a vertical board) would be 3" , so dont put the ce forward of
3"
> behind the leading edge of said board. or suffer lee helm. just
speculating : )
>
>
>
> To: Michalak@yahoogroups.com
> From: nelsarv@...
> Date: Sun, 16 Jun 2013 15:47:03 +0000
> Subject: [Michalak] Translation Please
>
>
>
>
>

[Non-text portions of this message have been removed]
• thank YOU nels, you have been a great source of info on many subjects over the past many months To: Michalak@yahoogroups.com From: nelsarv@hotmail.com Date:
Jun 17 1 of 5
View Source
thank YOU nels, you have been a great source of info on many subjects over the past many months

To: Michalak@yahoogroups.com
From: nelsarv@...
Date: Mon, 17 Jun 2013 15:27:03 +0000
Subject: [Michalak] Re: Translation Please

Thanks Dan and Sam!
Somehow I expected it to be far more complicated that that:-) Why can't
those navel architects say what they mean in plain English? (Just
kidding Sam)

Bolger does seem to also suggest that a boomless sail has more of a
tendency towards weather helm than one with a boom and a sprit sail is
generally boomless, so perhaps why the CE or mast should be a bit
further aft. His essays on the sprit rig are important reading in my
opinion as that rig attracts a lot of interest for a small hull designed
for paddling or rowing.

Nels

--- In Michalak@yahoogroups.com, daniel brown wrote:
>
> here i am speculating: the quarter chord of a 12" wide centerboard
(assuming a vertical board) would be 3" , so dont put the ce forward of
3"
> behind the leading edge of said board. or suffer lee helm. just
speculating : )
>
>
>
> To: Michalak@yahoogroups.com
> From: nelsarv@...
> Date: Sun, 16 Jun 2013 15:47:03 +0000
> Subject: [Michalak] Translation Please
>
>
>
>
>

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

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