*** Jib size or Main/Foretriangle Ratio ***

If very theoretically 1 (equally large) must be the best. It lowers
(vertically) the CE to minimum and the shortest possible mast is needed.

1. What says that the main should be bigger?

2.Some boats have M/F-ratios of 4. That seems really stupid.

3. Is a self tacking jib a matter of importance when regarding the
M/F-ratio?



Morgan O.

Morgan O says:

1. What says that the main should be bigger?

Nothing really, but it has been found over many years that you are able to
"change gears" more efficiently this way. Reef main first, then drop a size of
headsail, then reef main again, then remove headsail completely, then reef main
again, then bare-pole in the least dangerous direction ;-) With a really
large jib, your first "gear change" involves removing the largest sail on the
boat.

2.Some boats have M/F-ratios of 4. That seems really stupid.

From someone who obviously has little knowledge of sailplans, why do you use
the word "stupid?" Do you really mean "I don't understand?"

3. Is a self tacking jib a matter of importance when regarding the
M/F-ratio?

Not necessarily

I suggest you find a book called "Sail Power", by Wally Ross, and look into
these things deeper.

Steve
Stephen C. Baker - Yacht Designer
http://members.aol.com/SailDesign/pr...cbweb/home.htm

On 14 Oct 2004 10:06:15 GMT, Stephen Baker wrote:

Morgan O says:

1. What says that the main should be bigger?

Nothing really, but it has been found over many years that you are able to
"change gears" more efficiently this way. Reef main first, then drop a size of
headsail, then reef main again, then remove headsail completely, then reef main
again, then bare-pole in the least dangerous direction ;-) With a really
large jib, your first "gear change" involves removing the largest sail on the
boat.

2.Some boats have M/F-ratios of 4. That seems really stupid.

From someone who obviously has little knowledge of sailplans, why do you use
the word "stupid?" Do you really mean "I don't understand?"

;o) ...that's one wya to see it.

I have dwelled over different riggs quite a while... and the real benefit of
a Bermuda Sloop is that you get 2 high ratio sails still with a low
positioned CE.

Making a small jib you could just as well use a Bermuda Cat (no jib).


3. Is a self tacking jib a matter of importance when regarding the
M/F-ratio?

Not necessarily

I get a little tiered of those who call themselves designers and only whant
people to buy books or get stuffed...

Usenet is for debateing facts, knowledge and gossip, and to those who
don't like that, try stopping it!

But it's probably true, if everyone, always, only threw book titels at each
other it would most likely die fast enough.


Morgan O.

On 14 Oct 2004 10:06:15 GMT, ospam (Stephen Baker)
wrote:

I suggest you find a book called "Sail Power", by Wally Ross, and look into
these things deeper.

Damn, I was lucky the day I found a used copy of that book! Was there
ever a sequel, second edition or more recent book that matches it for
clarity and sheer depth?

I totally rethought my sail trim due to Ross's work, and now get a lot
more out of my cruising.

R.

There are 35 copies available on alibris.com, from $6.75
A good book.

rhys wrote:

On 14 Oct 2004 10:06:15 GMT, ospam (Stephen Baker)
wrote:

I suggest you find a book called "Sail Power", by Wally Ross, and look into
these things deeper.

Damn, I was lucky the day I found a used copy of that book! Was there
ever a sequel, second edition or more recent book that matches it for
clarity and sheer depth?

I totally rethought my sail trim due to Ross's work, and now get a lot
more out of my cruising.

R.

Morgan Ohlson wrote:
I have dwelled over different riggs quite a while... and the real benefit of
a Bermuda Sloop is that you get 2 high ratio sails still with a low
positioned CE.

???

The higher the aspect ratio of the sails, the higher the CE.

However, a higher CE is not really a problem on a small crew-ballasted
boat. The difference is trivial. OTOH, high aspect ratio rigs have a
number of drawbacks for small boats... they require a bit more fancy
engineering, a somewhat more complex & more stressed rig, and they don't
work as well in light air. Then in heavy air, you reef and pay a penalty
in windage for the length of unused spar.


Making a small jib you could just as well use a Bermuda Cat (no jib).

Not necessarily. A small jib is helpful in several ways, including going
to windward, handling the boat in a chop, and helping the boat maneuver.




3. Is a self tacking jib a matter of importance when regarding the
M/F-ratio?

Not necessarily


I get a little tiered of those who call themselves designers and only whant
people to buy books or get stuffed...

???


Usenet is for debateing facts, knowledge and gossip, and to those who
don't like that, try stopping it!

Morgan, you're in the position of asking for free advice, and getting
huffy because you don't like what you're told. Seems to me you're still
coming out ahead in any cost/benefit analysis here... why the attitude?

FWIW I don't like self tacking jibs except on racing boats where you're
likely to be very busy with other more important tasks. Self tacking
adds rigging & clutter that a cruiser would probably be better off
without. Plus, no self tacking sheeting arrangement sheets the sail
effectively for a wide range of courses, for example you can have it set
up for going cloe-hauled (the most common arrangement) and it's all but
useless on a reach... when a racing boat would be setting a spinnaker
anyway, but you probably wouldn't be.

Fresh Breezes- Doug King

On Thu, 14 Oct 2004 12:53:59 -0400, DSK wrote:

Morgan Ohlson wrote:
I have dwelled over different riggs quite a while... and the real benefit of
a Bermuda Sloop is that you get 2 high ratio sails still with a low
positioned CE.

???

The higher the aspect ratio of the sails, the higher the CE.

Naturally, but CE fall when dividing the total area on two sails. The
minimum CE is when M/F = 1

.... I think....

If a Gaff sloop is compared to a Bermuda Sloop they will have almost the
same low CE if the Bermuda have M/F = 1 (Gaff generally considered to
have a very low CE)


/.../
OTOH, high aspect ratio rigs have a
number of drawbacks for small boats... they require a bit more fancy
engineering,

???


a somewhat more complex & more stressed rig,

Taller mast???
CG rais???


and they don't
work as well in light air.

Transformed CE hight into more area is preferred in lite air??? (Typical low
ratio Gaff)


Then in heavy air, you reef and pay a penalty
in windage for the length of unused spar.

A bermuda M/F = 1 keeps the CE as low as possible (for that type) and keeps
the mast as low as possible.

What wou write is definitely right, but your quick jumps doesn't make sense.
No rig can be optimized for all occations anyway. What can be done is to
avoid silly arrangements with the rig choosen.

A Bermuda Sloop, and basicly all sloops should have a M/F ~1 since
everything else fast incease other backsides.


Making a small jib you could just as well use a Bermuda Cat (no jib).

Not necessarily. A small jib is helpful in several ways, including going
to windward, handling the boat in a chop, and helping the boat maneuver.

Explain how a very small jib will improve on a decreased Cat. (same total
area and both correctly balanced to CLA)

The cat...
- can have a high (acceptable high) ratio too.
- is easier to handle.
- Less rigging.
- CG fall almost zero thanks to a small jib

The small jib will not motivate it's existence (work etc.) compared to a Cat
incl. the jib area.

/.../
FWIW I don't like self tacking jibs except on racing boats where you're
likely to be very busy with other more important tasks. Self tacking
adds rigging & clutter that a cruiser would probably be better off
without. Plus, no self tacking sheeting arrangement sheets the sail
effectively for a wide range of courses, for example you can have it set
up for going cloe-hauled (the most common arrangement) and it's all but
useless on a reach... when a racing boat would be setting a spinnaker
anyway, but you probably wouldn't be.

"going cloe-hauled (the most common arrangement)" ? sorry, don't
understand.

A self tacking boom arrangement attract me most. Someone called it "old
Petrus boom".


Morgan O.

Morgan O says:

I get a little tiered of those who call themselves designers and only whant
people to buy books or get stuffed...

If you'd like to pay the $50 per hour consultation fee that I usually charge
(and get), then I would be happy to entertain all your questions at great
length ;-)
However, if you are looking for free-ish info, then the book is as good as it
gets.

Steve "gives small freebies, but has to make a living..."
Stephen C. Baker - Yacht Designer
http://members.aol.com/SailDesign/pr...cbweb/home.htm

Morgan O says:

The
minimum CE is when M/F = 1

Actually, geometrically speaking, it doesn't matter what the Main/Foretriangle
ratio is - the CE is always at 1/3 of the height of the triangle. THis works
for catboats and genoa-only boats.

Steve

Morgan Ohlson wrote:
Naturally, but CE fall when dividing the total area on two sails. The
minimum CE is when M/F = 1

... I think....

No, you could make the foot much longer than the luff... if you
wanted... and that would have a marginally lower CE. It would look
rather strange though.



If a Gaff sloop is compared to a Bermuda Sloop they will have almost the
same low CE if the Bermuda have M/F = 1 (Gaff generally considered to
have a very low CE)

Yes, but some gaff sails have a higher aspect ratio than that.


/.../

OTOH, high aspect ratio rigs have a
number of drawbacks for small boats... they require a bit more fancy
engineering,


???

In order to gain any benefits from the higher aspect ratio, the sail has
to be more carefully designed & made, the mast has to be longer & shaped
for less turbulence over the forward part of the sail, etc etc. A high
aspect ratio sail is a (relatively) high tech tool. You did not see high
aspect ratio sails back in the old days because they did not have the
engineering nore the materials to make them stand and get the benefit.


a somewhat more complex & more stressed rig,


Taller mast???
CG rais???

Yes but there will also be more compression on the mast, more tension on
the shrouds, greater loads on all parts of the rig. Greater loads on the
hull too including heeling moment.


What wou write is definitely right, but your quick jumps doesn't make sense.

OK, that's why I'm back trying to explain a little better. I am not a
good explainer, sorry.

No rig can be optimized for all occations anyway. What can be done is to
avoid silly arrangements with the rig choosen.

Yes, that is very true.


A Bermuda Sloop, and basicly all sloops should have a M/F ~1 since
everything else fast incease other backsides.

That depends on your goals. A lot of very practical sloops seem to to
have a luff/foot of about 1.5 ~ 1.8 sometimes more. Of course there are
those with shorter rigs & longer booms, many of them sail well too. It's
a question of getting the right sail area, the right foils, and putting
them in the right place on the hull.




Making a small jib you could just as well use a Bermuda Cat (no jib).

Not necessarily. A small jib is helpful in several ways, including going
to windward, handling the boat in a chop, and helping the boat maneuver.


Explain how a very small jib will improve on a decreased Cat. (same total
area and both correctly balanced to CLA)

Why insist on keeping area constant? Are you designing your boat to a
rating rule? It's true that as the jib gets smaller relative to the
mainsail, the overall rig efficiency... in most conditions... tends to
go down. So you make the whole rig a little bigger.

My point is that jib can help very much under some conditions (for
example, helping the flow across the lee side of the lower portion of a
low aspect mainsail), it's handy for maneuvering, it looks nice, and it
helps stave off boredom. It does add to the cost though.



FWIW I don't like self tacking jibs except on racing boats where you're
likely to be very busy with other more important tasks. Self tacking
adds rigging & clutter that a cruiser would probably be better off
without. Plus, no self tacking sheeting arrangement sheets the sail
effectively for a wide range of courses, for example you can have it set
up for going cloe-hauled (the most common arrangement) and it's all but
useless on a reach... when a racing boat would be setting a spinnaker
anyway, but you probably wouldn't be.


"going cloe-hauled (the most common arrangement)" ? sorry, don't
understand.

If you set up the self-tacking jib so that it can be trimmed to be most
effective when close hauled, it will not be anywhere near as effective
on other points of sail. This doesn't seem to bother some people.


A self tacking boom arrangement attract me most. Someone called it "old
Petrus boom".

Never heard of that. Anyway, I hope this helps.

DSK