RE: [bolger] CE/CLR (was OOOPS!)
Hi Bill, thanks for all the efforts. I would do the exercise leaving
out the rudder, but including the underbody, on the assumption that the
rudders job is to step in _afterwards_ to take over the situation.
What do you get then? I know, I could give it a shot, which I may.
Thanks again. Bill Kreamer
-----Original Message-----
From:wmrpage@...[mailto:wmrpage@...]
Sent: Monday, October 15, 2001 3:28 PM
To:bolger@yahoogroups.com
Subject: [bolger] CE/CLR (was OOOPS!)
Hmmm! Quite a range of advice from professionals on CE/CLR! I guess
this is why one shouldn't try this at home!
Anyway, I've recalculated the CE on the CK 17, with more attention
and fewer distractions. I think have the CE located more-or-less
accurately this time, and it is as about as far forward as I had
expected when I first cast the Mark I eyeball over the profile. After
giving the matter a little thought, I realize that I haven't a clue
as to how to locate the CLR, but I don't see how the location I draw
could possibly be a mere 12% ahead of the CLR. I'm soliciting
thoughts, corrrections, etc. on this.
I located the two CE's in the fashion shown in Michalak's May 15,
1999 newsletter and elsewhere. (i.e. the intersection of lines from
the head, clew and tack drawn to the mid-points of the foot, luff and
leech respectively). I calculated sail area by dividing each sail
into two right trianges with a common side connecting the clew to the
mast. Calculated total sail area was 121 ft. sq. v. 118 ft. sq. per
specifications, which seemed an acceptable margin of error to me.
(either that or a bunch of errors serendiptiously cancelled each
other out). Area of the mainsail calculated out to 2/3 total sail
area. I drew a line connecting the two CE points and measured back
1/3 of its length aft from the mainsail CE. (i got this back-asswards
on my first effort.) A line perpendicular to the waterline through
that point falls 2 ft. forward of the leading edge of the
daggerboard. (The line connecting the two CE's is not parallel to the
waterline, as the mizzen CE is slightly lower than that of the main,
but if it is better practice to measure the fore and aft distance
parallel to the waterline, the location of the combined CE would only
be 1-2" further aft.) I find a measured waterline of 16.5'; 12% of
16.5' = 2' - but does the CLR coincide with the leading edge of the
daggerboard??
On my first rather hurried attempt at this I assumed I could neglect
the area of the hull below the waterline on the theory that it was
shallow and flat and would have a negligible effect on lateral
resistance. I also (unconsciously) assumed that I could neglect the
area of the rudder. I treated the apparent mid-point of the
daggerboard as the CLR. On my revised drawing, this gives a "lead" of
16%. However, reflecting on Bolger's "St. Valerie" design, with its
small board and humungous rudder, I'm not sure that the rudder area
can be neglected. A crude attempt at calculating the combined CLR of
the board and rudder gives CLR location approximately 3.5' aft of the
leading edge of the board, for an incredible 33% "lead"! I next made
a rather feeble attempt at trying to determine a combined CLR for the
hull, board and rudder combined by attempting to balance a cut-out of
the underwater profile. This proved to be a rather subjective
exercise as performed by me. It did seem to indicate a shift of
calulate CLR to a point somewhat aft of the trailing edge of the
board. Chopping off the rudder moved it forward somewhat, somewhere
within the area of the board, I think, but technical difficulties
(flimsy cut-out, shaky hands, weak eyes)precluded arriving at any
definite conclusion. Anyone care to critique this exercise?
Ciao for Niao,
Bill in MN
(e-mail in haste, repent at leisure - I do it all the time!)
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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]
out the rudder, but including the underbody, on the assumption that the
rudders job is to step in _afterwards_ to take over the situation.
What do you get then? I know, I could give it a shot, which I may.
Thanks again. Bill Kreamer
-----Original Message-----
From:wmrpage@...[mailto:wmrpage@...]
Sent: Monday, October 15, 2001 3:28 PM
To:bolger@yahoogroups.com
Subject: [bolger] CE/CLR (was OOOPS!)
Hmmm! Quite a range of advice from professionals on CE/CLR! I guess
this is why one shouldn't try this at home!
Anyway, I've recalculated the CE on the CK 17, with more attention
and fewer distractions. I think have the CE located more-or-less
accurately this time, and it is as about as far forward as I had
expected when I first cast the Mark I eyeball over the profile. After
giving the matter a little thought, I realize that I haven't a clue
as to how to locate the CLR, but I don't see how the location I draw
could possibly be a mere 12% ahead of the CLR. I'm soliciting
thoughts, corrrections, etc. on this.
I located the two CE's in the fashion shown in Michalak's May 15,
1999 newsletter and elsewhere. (i.e. the intersection of lines from
the head, clew and tack drawn to the mid-points of the foot, luff and
leech respectively). I calculated sail area by dividing each sail
into two right trianges with a common side connecting the clew to the
mast. Calculated total sail area was 121 ft. sq. v. 118 ft. sq. per
specifications, which seemed an acceptable margin of error to me.
(either that or a bunch of errors serendiptiously cancelled each
other out). Area of the mainsail calculated out to 2/3 total sail
area. I drew a line connecting the two CE points and measured back
1/3 of its length aft from the mainsail CE. (i got this back-asswards
on my first effort.) A line perpendicular to the waterline through
that point falls 2 ft. forward of the leading edge of the
daggerboard. (The line connecting the two CE's is not parallel to the
waterline, as the mizzen CE is slightly lower than that of the main,
but if it is better practice to measure the fore and aft distance
parallel to the waterline, the location of the combined CE would only
be 1-2" further aft.) I find a measured waterline of 16.5'; 12% of
16.5' = 2' - but does the CLR coincide with the leading edge of the
daggerboard??
On my first rather hurried attempt at this I assumed I could neglect
the area of the hull below the waterline on the theory that it was
shallow and flat and would have a negligible effect on lateral
resistance. I also (unconsciously) assumed that I could neglect the
area of the rudder. I treated the apparent mid-point of the
daggerboard as the CLR. On my revised drawing, this gives a "lead" of
16%. However, reflecting on Bolger's "St. Valerie" design, with its
small board and humungous rudder, I'm not sure that the rudder area
can be neglected. A crude attempt at calculating the combined CLR of
the board and rudder gives CLR location approximately 3.5' aft of the
leading edge of the board, for an incredible 33% "lead"! I next made
a rather feeble attempt at trying to determine a combined CLR for the
hull, board and rudder combined by attempting to balance a cut-out of
the underwater profile. This proved to be a rather subjective
exercise as performed by me. It did seem to indicate a shift of
calulate CLR to a point somewhat aft of the trailing edge of the
board. Chopping off the rudder moved it forward somewhat, somewhere
within the area of the board, I think, but technical difficulties
(flimsy cut-out, shaky hands, weak eyes)precluded arriving at any
definite conclusion. Anyone care to critique this exercise?
Ciao for Niao,
Bill in MN
(e-mail in haste, repent at leisure - I do it all the time!)
Yahoo! Groups Sponsor
ADVERTISEMENT
<http://rd.yahoo.com/M=168643.1620686.3205344.1261774/D=egroupweb/S=1705
065791:HM/A=816903/R=2/*http://shop.store.yahoo.com/cgi-bin/clink?overst
ock3+shopping:dmad/M=168643.1620686.3205344.1261774/D=egroupweb/S=170506
5791:HM/A=816903/R=3/10031755%20>
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ock3+shopping:dmad/M=168643.1620686.3205344.1261774/D=egroupweb/S=170506
5791:HM/A=816903/R=5/10031755%20>
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]
Hi Bill
To me, your sail area calculations sound reliable. Why not use the same
'divide and conquer' approach for the CLR?
FWIW, Ted Brewer suggests including half of the rudder are in the CLR
calculation. (His 'Understanding boat design' offers a plausible explanation
for the requirement for lead, BTW).
John Teale ( in 'How to design a boat' ) includes the entire rudder area in
his CLR.
These are pretty eminent sources, and if I read them correctly, they
disagree by a sizeable amount :)
It seems logical to me that rudder area should be included as part of the
lateral plane - Mr Bolger (in BWAOM) makes a few references to the
experiments and learning process that has led to designs like the St
Valerie (from recollection, the essays on Dart, Cartopper)
Cheers
Derek
To me, your sail area calculations sound reliable. Why not use the same
'divide and conquer' approach for the CLR?
FWIW, Ted Brewer suggests including half of the rudder are in the CLR
calculation. (His 'Understanding boat design' offers a plausible explanation
for the requirement for lead, BTW).
John Teale ( in 'How to design a boat' ) includes the entire rudder area in
his CLR.
These are pretty eminent sources, and if I read them correctly, they
disagree by a sizeable amount :)
It seems logical to me that rudder area should be included as part of the
lateral plane - Mr Bolger (in BWAOM) makes a few references to the
experiments and learning process that has led to designs like the St
Valerie (from recollection, the essays on Dart, Cartopper)
Cheers
Derek
Hmmm! Quite a range of advice from professionals on CE/CLR! I guess
this is why one shouldn't try this at home!
Anyway, I've recalculated the CE on the CK 17, with more attention
and fewer distractions. I think have the CE located more-or-less
accurately this time, and it is as about as far forward as I had
expected when I first cast the Mark I eyeball over the profile. After
giving the matter a little thought, I realize that I haven't a clue
as to how to locate the CLR, but I don't see how the location I draw
could possibly be a mere 12% ahead of the CLR. I'm soliciting
thoughts, corrrections, etc. on this.
I located the two CE's in the fashion shown in Michalak's May 15,
1999 newsletter and elsewhere. (i.e. the intersection of lines from
the head, clew and tack drawn to the mid-points of the foot, luff and
leech respectively). I calculated sail area by dividing each sail
into two right trianges with a common side connecting the clew to the
mast. Calculated total sail area was 121 ft. sq. v. 118 ft. sq. per
specifications, which seemed an acceptable margin of error to me.
(either that or a bunch of errors serendiptiously cancelled each
other out). Area of the mainsail calculated out to 2/3 total sail
area. I drew a line connecting the two CE points and measured back
1/3 of its length aft from the mainsail CE. (i got this back-asswards
on my first effort.) A line perpendicular to the waterline through
that point falls 2 ft. forward of the leading edge of the
daggerboard. (The line connecting the two CE's is not parallel to the
waterline, as the mizzen CE is slightly lower than that of the main,
but if it is better practice to measure the fore and aft distance
parallel to the waterline, the location of the combined CE would only
be 1-2" further aft.) I find a measured waterline of 16.5'; 12% of
16.5' = 2' - but does the CLR coincide with the leading edge of the
daggerboard??
On my first rather hurried attempt at this I assumed I could neglect
the area of the hull below the waterline on the theory that it was
shallow and flat and would have a negligible effect on lateral
resistance. I also (unconsciously) assumed that I could neglect the
area of the rudder. I treated the apparent mid-point of the
daggerboard as the CLR. On my revised drawing, this gives a "lead" of
16%. However, reflecting on Bolger's "St. Valerie" design, with its
small board and humungous rudder, I'm not sure that the rudder area
can be neglected. A crude attempt at calculating the combined CLR of
the board and rudder gives CLR location approximately 3.5' aft of the
leading edge of the board, for an incredible 33% "lead"! I next made
a rather feeble attempt at trying to determine a combined CLR for the
hull, board and rudder combined by attempting to balance a cut-out of
the underwater profile. This proved to be a rather subjective
exercise as performed by me. It did seem to indicate a shift of
calulate CLR to a point somewhat aft of the trailing edge of the
board. Chopping off the rudder moved it forward somewhat, somewhere
within the area of the board, I think, but technical difficulties
(flimsy cut-out, shaky hands, weak eyes)precluded arriving at any
definite conclusion. Anyone care to critique this exercise?
Ciao for Niao,
Bill in MN
(e-mail in haste, repent at leisure - I do it all the time!)
this is why one shouldn't try this at home!
Anyway, I've recalculated the CE on the CK 17, with more attention
and fewer distractions. I think have the CE located more-or-less
accurately this time, and it is as about as far forward as I had
expected when I first cast the Mark I eyeball over the profile. After
giving the matter a little thought, I realize that I haven't a clue
as to how to locate the CLR, but I don't see how the location I draw
could possibly be a mere 12% ahead of the CLR. I'm soliciting
thoughts, corrrections, etc. on this.
I located the two CE's in the fashion shown in Michalak's May 15,
1999 newsletter and elsewhere. (i.e. the intersection of lines from
the head, clew and tack drawn to the mid-points of the foot, luff and
leech respectively). I calculated sail area by dividing each sail
into two right trianges with a common side connecting the clew to the
mast. Calculated total sail area was 121 ft. sq. v. 118 ft. sq. per
specifications, which seemed an acceptable margin of error to me.
(either that or a bunch of errors serendiptiously cancelled each
other out). Area of the mainsail calculated out to 2/3 total sail
area. I drew a line connecting the two CE points and measured back
1/3 of its length aft from the mainsail CE. (i got this back-asswards
on my first effort.) A line perpendicular to the waterline through
that point falls 2 ft. forward of the leading edge of the
daggerboard. (The line connecting the two CE's is not parallel to the
waterline, as the mizzen CE is slightly lower than that of the main,
but if it is better practice to measure the fore and aft distance
parallel to the waterline, the location of the combined CE would only
be 1-2" further aft.) I find a measured waterline of 16.5'; 12% of
16.5' = 2' - but does the CLR coincide with the leading edge of the
daggerboard??
On my first rather hurried attempt at this I assumed I could neglect
the area of the hull below the waterline on the theory that it was
shallow and flat and would have a negligible effect on lateral
resistance. I also (unconsciously) assumed that I could neglect the
area of the rudder. I treated the apparent mid-point of the
daggerboard as the CLR. On my revised drawing, this gives a "lead" of
16%. However, reflecting on Bolger's "St. Valerie" design, with its
small board and humungous rudder, I'm not sure that the rudder area
can be neglected. A crude attempt at calculating the combined CLR of
the board and rudder gives CLR location approximately 3.5' aft of the
leading edge of the board, for an incredible 33% "lead"! I next made
a rather feeble attempt at trying to determine a combined CLR for the
hull, board and rudder combined by attempting to balance a cut-out of
the underwater profile. This proved to be a rather subjective
exercise as performed by me. It did seem to indicate a shift of
calulate CLR to a point somewhat aft of the trailing edge of the
board. Chopping off the rudder moved it forward somewhat, somewhere
within the area of the board, I think, but technical difficulties
(flimsy cut-out, shaky hands, weak eyes)precluded arriving at any
definite conclusion. Anyone care to critique this exercise?
Ciao for Niao,
Bill in MN
(e-mail in haste, repent at leisure - I do it all the time!)