Correct. Whatever the rig, if you have it mounted on a barge, or the land,
you have a big problem. If. however, it's on a boat that will turn over. the
force needed to turn it over is a strong as the rig needs to be. Find a
sparmaker or an engineer.

"Wayne.B" wrote:

On 21 Oct 2004 17:01:27 -0700,
(peterMelbourneAustralia) wrote:
From my days sailing windrush catamarans, I am a littel worried that
the 82mm diameter might not be enough. I know circular section is not
high performance but that is not of concern. I am keen on this section
because it is new, made of high grade metal, from a professional and
failry cheap, $250 Australian.

I intend to go cruising, thus needs to be able of withstanding strong
winds. Have every intention of reefing when gets blowy. 23ft proa
weighs 200kg unladen.

Will/should 82mm diameter be sufficent?

========================================

You really need to consult with an experienced spar maker. One of my
old sailboats was once dismasted and I was surprised to learn that the
key engineering variable is not sail area or wind speed; instead it is
righting moment.

On Fri, 22 Oct 2004 04:46:23 GMT, Jim Conlin wrote:

Correct. Whatever the rig, if you have it mounted on a barge, or the land,
you have a big problem.
"Wayne.B" wrote:

On 21 Oct 2004 17:01:27 -0700,
(peterMelbourneAustralia) wrote:
========================================

You really need to consult with an experienced spar maker.

You could look up on boats with the aproximately the same righting momentum,
and add some mariginals.

For stable boats the wind is crucial since it adds as v^2. So you must put
in "your maximum weather" and this part you usually don't know for other
boat modells... and your rig maker will probably ask...??? ...yes! you!

WANTED! Straight, approximative momentum formula suitable for 1 hull dinghy
(no transformation C's added).

I found a momentum formula more suited for cat's (I think):
http://www.bijlard.demon.nl/page20.html
(part of the stability number)


Morgan O.

Morgan O says:

For stable boats the wind is crucial since it adds as v^2.

For any boat, the stability (righting moment) is the only thing you need. Wind
is actually immaterial except for the small forces added by side-loading of the
spar by the main.

Steve

On 22 Oct 2004 20:52:21 GMT, Stephen Baker wrote:

Morgan O says:

For stable boats the wind is crucial since it adds as v^2.

For any boat, the stability (righting moment) is the only thing you need. Wind
is actually immaterial except for the small forces added by side-loading of the
spar by the main.

Steve

It actually depends on the size of the rig and the momentum. The rig can be
undersized!!! ...and then it's the momentum that doesn't matter!

Since you don't know his boat, you can't say for shure ..and that's why I
didn't.


Morgan O.

Morgan O says:

It actually depends on the size of the rig and the momentum. The rig can be
undersized!!! ...and then it's the momentum that doesn't matter!

Morgan, for someone who professes to know little about the subject, I can only
say that you are accurate - you know little.

Since you don't know his boat, you can't say for shure ..and that's why I
didn't.

When you have designed boats that have raced around the world, and come home
with their rigs intact, then come back and tell me I'm wrong. Until then,
either buy the book I recommended to you, and read up on the subject, or be
quiet and stop giving out potentially dangerous information with no knowledge
of the subject.

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

On 23 Oct 2004 16:01:42 GMT, Stephen Baker wrote:

you know little.

I don't like people to give faulty advice anyhow. I just liked to give a
hint to PeterM.A about that.

...but I will not fall to your standards of attacking...

....explained this way...

If you have a rig in solid concrete, which would matter the most to the rig?
A) wind speed?
B) the momentum of the solid concrete?

take care... hope you understand something new now!



Morgan O.

Morgan says:

If you have a rig in solid concrete, which would matter the most to the rig?
A) wind speed?
B) the momentum of the solid concrete?


If you had a boat with infinite righting moment, it would be dry land, not a
boat. Not an apple, just another orange...

..but I will not fall to your standards of attacking...

not attacking, Morgan, just quoting you at the beginning of this series of
threads.

Steve "plonk!"

On Sat, 23 Oct 2004 16:58:02 GMT, Morgan Ohlson
wrote:

On 23 Oct 2004 16:01:42 GMT, Stephen Baker wrote:

you know little.

I don't like people to give faulty advice anyhow. I just liked to give a
hint to PeterM.A about that.

..but I will not fall to your standards of attacking...

...explained this way...

If you have a rig in solid concrete, which would matter the most to the rig?
A) wind speed?
B) the momentum of the solid concrete?

take care... hope you understand something new now!



Morgan O.

You are absolutely right. If the rig were mounted in concrete the
important force would result from wind velocity and sail area.

However -- we are discussing a rig installed on a BOAT and the
important force is righting moment.

i.e., in the case you are discussing the mast is fixed and therefore
the effective area of the sail is constant. In the case of a spar
mounted on a movable base, i.e., a boat, the spar moves and therefore
the effective area of the sail changes with changes in wind velocity,
thus the important figure is the force opposing the spar movement, the
righting moment.

Most people who have any knowledge of boats understand this fact
instinctively.




Cheers,

Bruce
(k4556atinetdotcodotth)