Mast rake is the angle from vertical, fore and aft. In other words,
when you are looking at the boat from exactly abeam. Increasing mast
rake helps pointing but as always, there's a trade-off. Increased mast
rake hurts off-wind performance and also hurts light air performance.

I happen to the think that mast rake is often overdone. Having worked
at tuning bunches of different one-design boats, it's all too easy to
just lengthen the forestay, and see a slight improvement in pointing
as the answer to my prayers when it really doesn't help me at the
finish line. In fact, several times I have said to the crew "Let's
start all over from scratch, stand the mast up straight, and begin
raking it little by little to find what we need." And wow! Suddenly
the boat is moving like it should be!

An exception is the Hobie 16. Because the rudders are the most
effective part of the underwater foil, getting the sail area as far
aft, over the rudders, as possible, makes the boat go to windward much
much better. It also makes the boat easier to tack, which can be a
major factor. The limiting factor in mast rake here is that the boom
drags on the aft cross beam, and most Hobie 16 racers sail with it
there.

Remember too that the mast is a long lever... if you make a millimeter
adjustment at deck level, the top of the mast will move a lot further.
I think this is why so many people overdo it.

Mast bend.... bending the mast fore-and-aft will pull the mainsail
flatter along the leading edge, and if everything else stays the same,
will also open up the leach. Many keelboats are tuned so that
increasing backstay tension bends the mast, with masthead rigs this
depends on either a babystay or adjusting lowers; with a frac rig the
backstay will bend the upper mast. To get fancy, some boats have
running backstay and/or checkstays which limit how much the mast bends
at some particular point. To depower the sail, bending the upper mast
will help. Bending the lower mast will flatten the largest part of the
main (remember the cunningham may need to be re-adjusted) and also
have the same effect as increasing rake.

Remember too that any time you increase tension aft on the mast, with
the backstay, running back, or even the leach of the mainsail, the
luff of the jib is going to also be affected. Everything is connected
to everything else, this is why it is important to *small* tuning
adjustments until you are sure what the overall result will be.

BTW getting back to the subject of weatherliness, I walked around the
docks at our marina yesterday (yes we went down to the boat on a
weekday) and looked sheet tracks. Only about 25% of the boats had
headsail sheeting arrangements that looked reasonably efficient. Most
productions boats had half-measures designed partially for sailing and
partially for cost control and partially to keep the crew from
stubbing their toes.

Fresh Breezes- Doug King

Remember too that any time you increase tension aft on the mast, with
the backstay, running back, or even the leach of the mainsail, the
luff of the jib is going to also be affected.

Oh my!

RB

Remember too that the mast is a long lever... if you make a millimeter
adjustment at deck level, the top of the mast will move a lot further.
I think this is why so many people overdo it.


Holy leaping toads!

RB

Increased mast
rake hurts off-wind performance and also hurts light air performance.



Wowzer rats! Really?


RB

Bobsprit wrote:

Increased mast
rake hurts off-wind performance and also hurts light air performance.

Wowzer rats! Really?

RB

Well Bob, those were three really useful and informative comments.

Now explain to us exactly how increased rake causes a deterioration in
downwind performance and what can be done to offset this, (without removing
the rake). No google.

Ready, set,, go!

Now I know some of you will want to jump in here and answer, don't, let
Bob come up with the answers himself!

Cheers
Marty

Martin Baxter wrote:


Well Bob, those were three really useful and informative comments.

Now explain to us exactly how increased rake causes a deterioration in
downwind performance and what can be done to offset this, (without removing
the rake). No google.

Ready, set,, go!

Now I know some of you will want to jump in here and answer, don't, let
Bob come up with the answers himself!

I know, I know!! Mount an anchor on the companionway hatch cover!

This has been proven to increase downwind speed every time, regardless of mast
rake!

DSK

DSK wrote:

Martin Baxter wrote:


Well Bob, those were three really useful and informative comments.

Now explain to us exactly how increased rake causes a deterioration in
downwind performance and what can be done to offset this, (without removing
the rake). No google.

Ready, set,, go!

Now I know some of you will want to jump in here and answer, don't, let
Bob come up with the answers himself!

I know, I know!! Mount an anchor on the companionway hatch cover!

This has been proven to increase downwind speed every time, regardless of mast
rake!

DSK

Jeeze Doug, I asked you not to help! ;-0~

Cheers
Marty

Chrome anchor nitwit. That's the only one that'll work!

"DSK" wrote in message
...
Martin Baxter wrote:


Well Bob, those were three really useful and informative comments.

Now explain to us exactly how increased rake causes a deterioration in
downwind performance and what can be done to offset this, (without
removing
the rake). No google.

Ready, set,, go!

Now I know some of you will want to jump in here and answer, don't, let
Bob come up with the answers himself!

I know, I know!! Mount an anchor on the companionway hatch cover!

This has been proven to increase downwind speed every time, regardless of
mast
rake!

DSK

DSK wrote:

Mast rake is the angle from vertical, fore and aft. In other words,
when you are looking at the boat from exactly abeam. Increasing mast
rake helps pointing but as always, there's a trade-off.

Good lord he's actually gone away, read a little and learnt from my
earlier posts! Will wonders never cease! Today is a day of enlightenment
for Doug!

Hip hip Hooray!



Mast bend.... will pull the mainsail
flatter along the leading edge,

Great now he's finally got it right!

Only about 25% of the boats had
headsail sheeting arrangements that looked reasonably efficient. Most
productions boats had half-measures designed partially for sailing and
partially for cost control and partially to keep the crew from
stubbing their toes.

And how did you decide that? More self aggrandizement perhaps?

Cheers

Bobsprit wrote:

Remember too that any time you increase tension aft on the mast, with
the backstay, running back, or even the leach of the mainsail, the
luff of the jib is going to also be affected.

Oh my!



Indeed. He has an amazing capacity to reiterate that which has already
been posted.

Cheers