Nav wrote:
Young America was designed for 6 degrees trim at 10 knots boatspeed and
30 degrees heel. That's about as fast they expected to go when powered
up here.

6 degrees trim on what... the keel trim tab? That sounds like a heck of
a lot.

Bear in mind that at 30 degrees heel, the projected sail area and keel
foil area are only 85% of actual area. Hard to claim that this is when
the boats are most efficient.

Anyway, long narrow boats like the IACC class and the old 12s too tend
to sail at higher angles of heel than more normally proportioned boats.
I still think 30 degrees is a bit of an overstatement.

DSK

DSK wrote:

Nav wrote:

Young America was designed for 6 degrees trim at 10 knots boatspeed
and 30 degrees heel. That's about as fast they expected to go when
powered up here.


6 degrees trim on what... the keel trim tab? That sounds like a heck of
a lot.

Bear in mind that at 30 degrees heel, the projected sail area and keel
foil area are only 85% of actual area. Hard to claim that this is when
the boats are most efficient.


Who said anything about efficient. Powered up refers to power!

Anyway, long narrow boats like the IACC class and the old 12s too tend
to sail at higher angles of heel than more normally proportioned boats.
I still think 30 degrees is a bit of an overstatement.

Wot only a 'bit' now is it? Just yesterday you rubbished it! Doug, lots
of boats are only fully powered up at 30 (or more) degrees heel. Of
course as a dingly sailor you wouldn't know that but it's really true.

Let me paint a typical picture for you: At that 30 degrees heel the boat
is alive and really punching through waves to windward. Windspeeed is
probably about 18-20 knots with gusts to 25. The rail is getting wet
with occasional waves over the bow and it's the limit where more wind
means you'll probably have to ease the main sheet (or reduce sails) to
maintain good control and boat speed. It's a fun place to sail -powered up!

Ask any of the others -they've sailed there I'm sure!

Cheers

Anyway, long narrow boats like the IACC class and the old 12s too tend
to sail at higher angles of heel than more normally proportioned
boats. I still think 30 degrees is a bit of an overstatement.



Nav wrote:
Wot only a 'bit' now is it? Just yesterday you rubbished it! Doug, lots
of boats are only fully powered up at 30 (or more) degrees heel.

OK, I am still not sure what you mean by "powered up." It sounds to me
like you are relishing the feeling of heeling too much. It's fun, but
it's really not fast.

.... Of
course as a dingly sailor you wouldn't know that but it's really true.

Spoken like one whose experience in racing class dinghies is limited to
embarassing capsizes within 100 yards of the club dock.


Let me paint a typical picture for you: At that 30 degrees heel the boat
is alive and really punching through waves to windward.

At 30 degrees heel, the boat is heeling too much. It is "punching"
through waves because the hull presenting a set of awkward angles. Other
boats have depowered a little and are going faster.

... Windspeeed is
probably about 18-20 knots with gusts to 25. The rail is getting wet
with occasional waves over the bow and it's the limit where more wind
means you'll probably have to ease the main sheet (or reduce sails) to
maintain good control and boat speed. It's a fun place to sail -powered up!

Ask any of the others -they've sailed there I'm sure!

Sailing rail-down and driving hard is a lot of fun. But it's not the way
boats sail their best.

Personally I like spinnaker reaches with threatening wipe-outs on every
wave. But it's a rare indulgence because it isn't really the right way
to do things. In fact, in one of our 'powered up' Johnson 18 photos it
was said that it looked like we didn't know what we were doing.

Fresh Breezes- Doug King

DSK wrote:

Anyway, long narrow boats like the IACC class and the old 12s too
tend to sail at higher angles of heel than more normally proportioned
boats. I still think 30 degrees is a bit of an overstatement.




Nav wrote:
Wot only a 'bit' now is it? Just yesterday you rubbished it! Doug,
lots of boats are only fully powered up at 30 (or more) degrees heel.


OK, I am still not sure what you mean by "powered up." It sounds to me
like you are relishing the feeling of heeling too much. It's fun, but
it's really not fast.

.... Of course as a dingly sailor you wouldn't know that but it's
really true.


Spoken like one whose experience in racing class dinghies is limited to
embarassing capsizes within 100 yards of the club dock.


Let me paint a typical picture for you: At that 30 degrees heel the
boat is alive and really punching through waves to windward.


At 30 degrees heel, the boat is heeling too much. It is "punching"
through waves because the hull presenting a set of awkward angles. Other
boats have depowered a little and are going faster.

Have you done any big boat sailing or been in a race in windy
conditions? Why not read the book whose URL I posted and then come back
on it. Better yet go back to the classic literature and look at the
tests of the Gimcrack. She was fastest at 30 degrees and was no faster
at 35 degrees. That's still a correct rule of thumb for most fast
cruiser racers today.

Perhaps Donal would like to post the figs. for his boat -if he's got them?

Another slam dunk.

Cheers

Nav wrote:
Have you done any big boat sailing or been in a race in windy
conditions?

Why, of COURSE not, Navvie. Never!

But then you are a liar, so you think I must be one too...


.. Why not read the book whose URL I posted and then come back
on it.

So you're saying that you base your judgement solely on what you've read
in books?

... Better yet go back to the classic literature and look at the
tests of the Gimcrack. She was fastest at 30 degrees and was no faster
at 35 degrees. That's still a correct rule of thumb for most fast
cruiser racers today.

Not in my experience. Most boats like about 12 degrees of heel. The
Soling (a relatively narrow boat) sailors I know say their boats like
18. I would generalize to say that narrower & heavier boats like more
heel, but in cases where the keels and/or rigs get dramatically less
efficient with increased angle, it would be beneficial to take some
serious sailing tests to determine the desirable range of heel for most
conditions.

One big limiting factor is the helm. Increasing heel increases weather
helm. That has to be counteracted with the helm. A slight weather helm
is nice, a lot is bad. It's slow and it can make the boat hard to control.


Perhaps Donal would like to post the figs. for his boat -if he's got them?

Another slam dunk.

Maybe you should be less concerned with "slam dunks" and more concerned
with actual sailing? Just a suggestion.

Fresh Breezes- Doug King

DSK wrote:

Nav wrote:

Have you done any big boat sailing or been in a race in windy
conditions?


Why, of COURSE not, Navvie. Never!

Well it's good to know my suspicions were correct.


So you're saying that you base your judgement solely on what you've read
in books?

It was you that was seeking references wasn't it? Don't you like
definitive references that support my views? How strange. Perhaps you
are the sophist Jax suggested?

Cheers

DSK wrote:



Not in my experience. Most boats like about 12 degrees of heel. The
Soling (a relatively narrow boat) sailors I know say their boats like
18. I would generalize to say that narrower & heavier boats like more
heel, but in cases where the keels and/or rigs get dramatically less
efficient with increased angle, it would be beneficial to take some
serious sailing tests to determine the desirable range of heel for most
conditions.


Bluster all you like but 30 degrres for max boat speed is still quite
usual. How about a designer of the Volvo 60:

"Roll, baby, roll …
Volvo 70’s must be designed to stringent large-heel-angle stability
criteria. While a canting keel increases stability (or righting moment)
dramatically under

typical sailing conditions (say 30 degrees of heel),

its offset CG actually works against a self-righting tendency at large,
knockdown heel angles. Accordingly, Volvo 70 Rule developers have
closely examined limitations on hull displacement and beam that affect
form stability, with additional limitations on keel weight and keel
swing angles. Each yacht shall have a designer-calculated limit of
positive stability greater than 115 degrees, with appendages positioned
in a worst-case scenario. In addition, each boat must successfully
self-right from a 180-degree inversion using only manual power to
articulate the keel."

http://www.perrottidesign.com/new_Volvo_Open70.html

Cheers

DSK wrote:



... Better yet go back to the classic literature and look at the tests
of the Gimcrack. She was fastest at 30 degrees and was no faster at 35
degrees. That's still a correct rule of thumb for most fast cruiser
racers today.


Not in my experience. Most boats like about 12 degrees of heel. The
Soling (a relatively narrow boat) sailors I know say their boats like
18.


I guess you would not have overtaken the race leader -look at this:


http://www.sevenoceans.com/SoloAroun...Leg1/Day30.htm


Cheers

DSK wrote:



Not in my experience. Most boats like about 12 degrees of heel.


Aha that'll be your dinghy experience showing itself again. In a bigger
keel boat you won't come anywhere except last if you limit yourself to
12 degrees. Now, boat's don't 'like' anything. They are just imanimate
objects really. The question is, what is the most common design angle?
(I've already posted one ref. Why don't you check Barnaby 'Basica naval
archtiecture' too and you'll see it's 30 degrees.) Heeling is not by
itself a bad thing -it means that lots of power is being taken from the
wind if the boat is trimmed properly. The general idea is that provided
the heel angle is moderate (say 30 degrees) the reduction in projected
fin area is not too serious...

Cheers

DSK wrote:

Anyway, long narrow boats like the IACC class and the old 12s too
tend to sail at higher angles of heel than more normally proportioned
boats. I still think 30 degrees is a bit of an overstatement.




Nav wrote:
Wot only a 'bit' now is it? Just yesterday you rubbished it! Doug,
lots of boats are only fully powered up at 30 (or more) degrees heel.


OK, I am still not sure what you mean by "powered up." It sounds to me
like you are relishing the feeling of heeling too much. It's fun, but
it's really not fast.

Wrong again. Look at the references.

Cheers