RE: [bolger] Re: OOPS! (CK 17 - gross error)
Thanks Peter, that makes it a bit clearer. So, a little CE lead
actually is neutral at some point of sailing. Any other ideas out
there?
Bill
-----Original Message-----
From:pvanderw@...[mailto:pvanderw@...]
Sent: Friday, October 12, 2001 1:28 PM
To:bolger@yahoogroups.com
Subject: [bolger] Re: OOPS! (CK 17 - gross error)
completely accurate, but I think it guides the thinking in the
correct direction.
First, we assume that the force created by the sail is perpendicular
to the sail itself. So, for example, if the sail was trimmed in
amidships, the force is at 90 degrees to the centerline. It won't
make the boat go forward, and if the CE is ahead of the CLR, it will
produce lee helm.
Second, if we let the sail out to a normal, sailing-to-windward
position with the boom say 10 degrees out to the side. The vector
force of the sail now had a forward component that can drive the
boat, but the line of action of the force crosses the centerline aft
of where it did in the first example. Perhaps right through the CLR
for a neutral helm.
Greater weather helm is generated if the sail is let out farther, or
if the boat is allowed to heel.
Peter
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[Non-text portions of this message have been removed]
actually is neutral at some point of sailing. Any other ideas out
there?
Bill
-----Original Message-----
From:pvanderw@...[mailto:pvanderw@...]
Sent: Friday, October 12, 2001 1:28 PM
To:bolger@yahoogroups.com
Subject: [bolger] Re: OOPS! (CK 17 - gross error)
> But, that said, how exactly does having the CE lead the CLR produceLet me offer the following explanation. I am not sure that it is
> desirable weather helm? Doesn't it? Shouldn't it?
completely accurate, but I think it guides the thinking in the
correct direction.
First, we assume that the force created by the sail is perpendicular
to the sail itself. So, for example, if the sail was trimmed in
amidships, the force is at 90 degrees to the centerline. It won't
make the boat go forward, and if the CE is ahead of the CLR, it will
produce lee helm.
Second, if we let the sail out to a normal, sailing-to-windward
position with the boom say 10 degrees out to the side. The vector
force of the sail now had a forward component that can drive the
boat, but the line of action of the force crosses the centerline aft
of where it did in the first example. Perhaps right through the CLR
for a neutral helm.
Greater weather helm is generated if the sail is let out farther, or
if the boat is allowed to heel.
Peter
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ADVERTISEMENT
<http://rd.yahoo.com/M=168643.1620686.3205344.1261774/D=egroupweb/S=1705
065791:HM/A=816901/R=5/*http://www.overstock.com/cgi-bin/d2.cgi?cid=1297
3>
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065791:HM/A=816901/R=6/*http://www.overstock.com/cgi-bin/d2.cgi?cid=1297
3>
Bolger rules!!!
- no cursing, flaming, trolling, spamming, or flogging dead horses
- pls take "personals" off-list, stay on topic, and punctuate
- add your comments at the TOP and SIGN your posts, snip all you like
- To order plans: Mr. Philip C. Bolger, P.O. Box 1209, Gloucester, MA,
01930, Fax: (978) 282-1349
- Unsubscribe:bolger-unsubscribe@yahoogroups.com
Your use of Yahoo! Groups is subject to the Yahoo! Terms of Service
<http://docs.yahoo.com/info/terms/> .
[Non-text portions of this message have been removed]
> But, that said, how exactly does having the CE lead the CLR produceLet me offer the following explanation. I am not sure that it is
> desirable weather helm? Doesn't it? Shouldn't it?
completely accurate, but I think it guides the thinking in the
correct direction.
First, we assume that the force created by the sail is perpendicular
to the sail itself. So, for example, if the sail was trimmed in
amidships, the force is at 90 degrees to the centerline. It won't
make the boat go forward, and if the CE is ahead of the CLR, it will
produce lee helm.
Second, if we let the sail out to a normal, sailing-to-windward
position with the boom say 10 degrees out to the side. The vector
force of the sail now had a forward component that can drive the
boat, but the line of action of the force crosses the centerline aft
of where it did in the first example. Perhaps right through the CLR
for a neutral helm.
Greater weather helm is generated if the sail is let out farther, or
if the boat is allowed to heel.
Peter
Yikes, now Im not sure what really happens with CE and CLR. I thought
(first mistake?) a boat needs a light weather helm that increases along
with wind speed. After the comments about the CK17, I see some others
may also share my confusion about why a _sailplan CE_ leads the _board +
hull CLR_. I do realize this designer knows exactly what hes doing.
But, that said, how exactly does having the CE lead the CLR produce
desirable weather helm? Doesnt it? Shouldnt it? Your kind
correction of my favorite misconceptions will be very much appreciated.
Then I can decide on a good location for a daggerboard on my 20 cat
ketch sharpie, and, I hope, avoid too much rework.
I went to the net to get some advice, which I found at
http://home.clara.net/gmatkin/therules.htm(thanks to Gavin Atkin).
Heres a summary of the opinions on balance, (as they relate to cat
ketch sharpies):
* CE should be right over CLR or an inch or two ahead - John F
Sutton
* CE should lead CLR by 12-14 % LWL (centerboard craft) - John
Teale
* 7-11 % lead (shoal full-ended centreboarders), + moveable
mast - Norman L Skene; and also:
CE of a boomless sail is some way aft of the drawn position - Skene?
* 11-14 % lead (ketch) - Dave Gerr
* CE over CLR ( flat-bottomed boats) - Jim Michalak
* 7 % lead conventional sloop) - L Francis Herreshoff, and
also:
as boat heels, depending on bow sharpness, water-flow from leeway may
turn bow to wind.
a wide shallow boat will tend to head up to the wind on heeling.
Increasing draft in a sail moves the effective centre aft.
a divided sail plans effective centre of effort moves less.
My sincere thanks to you all. -Bill
-----Original Message-----
From:wmrpage@...[mailto:wmrpage@...]
Sent: Wednesday, October 10, 2001 8:28 PM
To:bolger@yahoogroups.com
Subject: [bolger] OOPS! (CK 17 - gross error)
I see that I goofed on positioning the vertical when calculating the
position of the CE - on correction, the intersection with the LWL is
a bit more than 1' ahead of the leading edge of the daggerboard,
close enough to the 12% lead from CLR cited by Peter, given the crude
procedure.
[Non-text portions of this message have been removed]
(first mistake?) a boat needs a light weather helm that increases along
with wind speed. After the comments about the CK17, I see some others
may also share my confusion about why a _sailplan CE_ leads the _board +
hull CLR_. I do realize this designer knows exactly what hes doing.
But, that said, how exactly does having the CE lead the CLR produce
desirable weather helm? Doesnt it? Shouldnt it? Your kind
correction of my favorite misconceptions will be very much appreciated.
Then I can decide on a good location for a daggerboard on my 20 cat
ketch sharpie, and, I hope, avoid too much rework.
I went to the net to get some advice, which I found at
http://home.clara.net/gmatkin/therules.htm(thanks to Gavin Atkin).
Heres a summary of the opinions on balance, (as they relate to cat
ketch sharpies):
* CE should be right over CLR or an inch or two ahead - John F
Sutton
* CE should lead CLR by 12-14 % LWL (centerboard craft) - John
Teale
* 7-11 % lead (shoal full-ended centreboarders), + moveable
mast - Norman L Skene; and also:
CE of a boomless sail is some way aft of the drawn position - Skene?
* 11-14 % lead (ketch) - Dave Gerr
* CE over CLR ( flat-bottomed boats) - Jim Michalak
* 7 % lead conventional sloop) - L Francis Herreshoff, and
also:
as boat heels, depending on bow sharpness, water-flow from leeway may
turn bow to wind.
a wide shallow boat will tend to head up to the wind on heeling.
Increasing draft in a sail moves the effective centre aft.
a divided sail plans effective centre of effort moves less.
My sincere thanks to you all. -Bill
-----Original Message-----
From:wmrpage@...[mailto:wmrpage@...]
Sent: Wednesday, October 10, 2001 8:28 PM
To:bolger@yahoogroups.com
Subject: [bolger] OOPS! (CK 17 - gross error)
I see that I goofed on positioning the vertical when calculating the
position of the CE - on correction, the intersection with the LWL is
a bit more than 1' ahead of the leading edge of the daggerboard,
close enough to the 12% lead from CLR cited by Peter, given the crude
procedure.
[Non-text portions of this message have been removed]
I see that I goofed on positioning the vertical when calculating the
position of the CE - on correction, the intersection with the LWL is
a bit more than 1' ahead of the leading edge of the daggerboard,
close enough to the 12% lead from CLR cited by Peter, given the crude
procedure.
position of the CE - on correction, the intersection with the LWL is
a bit more than 1' ahead of the leading edge of the daggerboard,
close enough to the 12% lead from CLR cited by Peter, given the crude
procedure.