On Sun, 21 Nov 2004 12:18:14 -0800, Love a Sheep wrote:

I am learning to sail and have a few questions. I understand that the
sails can act either as an airofoil (lile an aircraft wing) or like a
parachute where the wind simply blows the sail directly. My question
is this. If the wind is ahead of the beam ie we are sailing windward
then I expect that the airofoil principle must always hold there
otherwise we would be sailing backwards!

However, if the wind is aft of the beam on say the starboard side then
surely we have a choice where to set the sails ie they can be on the
starboard side (ie the boom is pointing to the starboard side) where
they act as an airofoil or on the port side where they act as a
'parachute' - is this right or am I missing something. If so which is
best?

Thanks

You've already got a lot of good answers. I'll just point out one more
thing which is that the two sails on a boat interact. That is, even when
the wind is aft of abeam, the wind flowing over the main may be dead abeam
or so, because the jib or spinnaker changes the direction of flow.

--Mac

On Mon, 22 Nov 2004 04:02:33 GMT, Mac wrote:

On Sun, 21 Nov 2004 12:18:14 -0800, Love a Sheep wrote:

I am learning to sail and have a few questions. I understand that the
sails can act either as an airofoil (lile an aircraft wing) or like a
parachute where the wind simply blows the sail directly. My question
is this. If the wind is ahead of the beam ie we are sailing windward
then I expect that the airofoil principle must always hold there
otherwise we would be sailing backwards!

However, if the wind is aft of the beam on say the starboard side then
surely we have a choice where to set the sails ie they can be on the
starboard side (ie the boom is pointing to the starboard side) where
they act as an airofoil or on the port side where they act as a
'parachute' - is this right or am I missing something. If so which is
best?

I misread your question before my previous answer, which therefore
made no sense. I thought you were asking about the transition between
drawing and stalling. The boom would be to port in either case with
the wind on starboard.

As the wind goes aft, the boom must be let out farther to maintain
flow. The mast is the leading edge.

When the wind is really aft, you would square the sail to the wind,
letting it stall. Then the drag of the sail is pushing the boat.

If you understand this so far, the real question becomes "Is there a
wind angle where the boat will go faster stalled than drawing, even
without the boom or sail hitting the rigging?

That is the question I was answering before, and it is not what you
actually asked.




Rodney Myrvaagnes J36 Gjo/a


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