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

Very perceptive. However, when off the wind on most boats, the
rigging disallows the positioning of the sails to act as an airfoil.

CN

"Love a Sheep" wrote in message om...
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

On 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

Using the aerofoil analogy, the mast edge of the main sail and the
forward stay edge of the jib would be the leading edges, so I don't
follow that if the wind is from abaft starboard, why you would want
the boom out to starboard.

Brian W

On 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?

You're on track, but you've also to think about true wind and apparent
wind.....


Cheers!

Remco

On 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!

True

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?

No. If the wind is from starboard, and abaft the beam, the sails will
not normally stay out to starboard, as the sheets are rigged to pull
the boom (and jib) into the boat.

It is possible with the wind very nearly dead astern to have the main
and jib on opposite sides - this usually works best with the wind
slightly to the same side as the boom. This is called "sailing by the
lee", and will lead to an accidental jibe if you let the wind get too
far to the same side as the boom (then you will find out why it is
called a boom :-( )


--
Peter Bennett, VE7CEI
peterbb4 (at) interchange.ubc.ca
new newsgroup users info : http://vancouver-webpages.com/nnq
GPS and NMEA info: http://vancouver-webpages.com/peter
Vancouver Power Squadron: http://vancouver.powersquadron.ca

"Peter Bennett" wrote in message
news.com...
On 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!

True

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?

No. If the wind is from starboard, and abaft the beam, the sails will
not normally stay out to starboard, as the sheets are rigged to pull
the boom (and jib) into the boat.

It is possible with the wind very nearly dead astern to have the main
and jib on opposite sides - this usually works best with the wind
slightly to the same side as the boom. This is called "sailing by the
lee", and will lead to an accidental jibe if you let the wind get too
far to the same side as the boom (then you will find out why it is
called a boom :-( )

For either the slow, stupid, or stunned, it's called the boom boom.

Using the sail's trailing edge as a leading edge is problematic.
They will not be efficient this way - tantamount to running an
airplane wing backwards.

Letting them out on the port side however would work provided
you could let them out that far without fouling the rigging.

CN


"Love a Sheep" wrote in message om...
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

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

(Love a Sheep) wrote in message . com...
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
Once the wind if aft of the beam the generally accepted rule if to
have the boom at right angles to the wind. Likewise when you pole out
the headsail.

(Love a Sheep) wrote in message . com...
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 can't really put both of your sails to what in your description
would be the windward side of the boat...well, not effectively at
least. here's why....

Unless you're sailing dead downwind (wing and wing, or by the lee, as
mentioned - boom toward the VERY slight widward side, also as
mentioned) you'll notice that no matter how far out you let your sails
when on an actual port or starboard tack, you're always going to have
the airfoil effect, not a parachute effect. Watch your telltails,
you'll see the wind moving across the sails, leading edge to trailng
edge. In your case, if the wind was from starboard, even fairly
significantly abaft the beam, you would still sail on starboard tack,
sails trimmed out to port. Once this becomes impossibly, it's either
time to jibe, or go wing and wing.

To relate this to a plane, think about the apparent wind when they
slow down to land and they 'set' the flaps to create much more 'belly'
in the wing to maintain that lift as the wind direction changes
(remember, apparent wind...of course, they're still going forward,
but the plane wants to fall, so the wind direction is now coming from
further under the wing, less in front of it, so they have to adjust,
just like you do) But there's no way a wing will act as a parachute on
a plane, it's still an airfoil. Same thing you're doing with your
sails. The difference is in the fact that a plane can also adjust it's
apparent wind direction by adjusting its speed. But the adjustments
are based on the same principle. If the plane went too slow, it would
fall of course, luckily, we don't have to worry about that, and when
the wind is directly behind us (i.e. the minimal amount of apparent
wind) - we CAN use the parachute effect. but it's only in that
scenario.

how's that for a long drawn out explanation! Sorry for the verbose
detail...hope it made even a bit of sense!

P.S. And yes, be careful sailing downwind wing and wing...accidental
jibes are not your friend. if you're going to do it for long, pole
out, and rig preventers, especially in rolly seas.

Good luck!

Capt. Rob Welling
Sarasota, FL