“The starting point when dimensioning the rig is to calculate the
righting moment. It is commonly agreed that a heel angle of 30o is a
good design angle. This corresponds to a reasonably high wind strength
with the sails still generating high loads and the boat making good
speed through the water. Letting the boat heel over more....in reality
means a slower boat owing to increased resistance, with a
correspondingly smaller dynamic force.”

Principles of Yacht Design Larsson & Eliasson Adlard Coles 1994

Cheers

Nav wrote:
“The starting point when dimensioning the rig is to calculate the
righting moment. It is commonly agreed that a heel angle of 30o is a
good design angle. This corresponds to a reasonably high wind strength
with the sails still generating high loads and the boat making good
speed through the water. Letting the boat heel over more....in reality
means a slower boat owing to increased resistance, with a
correspondingly smaller dynamic force.”

Principles of Yacht Design Larsson & Eliasson Adlard Coles 1994


Funny, you picked almost the exact same words I would have

"Letting the boat heel over more....in reality means a slower boat owing
to increased resistance, with a correspondingly smaller dynamic force.”"

They're talking about stressing the rig, not best sailing efficiency.

DSK

DSK wrote:

Nav wrote:

“The starting point when dimensioning the rig is to calculate the
righting moment. It is commonly agreed that a heel angle of 30o is a
good design angle. This corresponds to a reasonably high wind strength
with the sails still generating high loads and the boat making good
speed through the water. Letting the boat heel over more....in reality
means a slower boat owing to increased resistance, with a
correspondingly smaller dynamic force.”

Principles of Yacht Design Larsson & Eliasson Adlard Coles 1994



Funny, you picked almost the exact same words I would have

"Letting the boat heel over more....in reality means a slower boat owing
to increased resistance, with a correspondingly smaller dynamic force.”"

They're talking about stressing the rig, not best sailing efficiency.


Note the _more_!!!! Now, who's talking efficiency? We were talking about
powered up! (I now accept that you may have no idea what that means).
Now define effciency for us so we can be sure that we are going to speak
the same language if you want to discuss efficiency.

Cheers

Nav wrote:
Note the _more_!!!! Now, who's talking efficiency? We were talking about
powered up! (I now accept that you may have no idea what that means).
Now define effciency for us so we can be sure that we are going to speak
the same language if you want to discuss efficiency.

I would say that "greatest sailing efficiency" could be defined as the
conditions (both weather and sail) that provided the highest VMG to
windward possible for that design.

Do the newest IACC boats go the fastest at 30 degrees of heel? That is
what you seem to be saying.

For most boats, the polars show the highest VMG in the 10 to 15 knot
wind range and sailing conditions of less than 20 degrees of heel. As I
said, narrow boats like to heel more but I'd be surprised if it were
that much more. I'm not very familiar with the last generation IACC boat
polars, maybe there are some on line.

Fresh Breezes- Doug King

"Nav" wrote in message
...
“The starting point when dimensioning the rig is to calculate the
righting moment. It is commonly agreed that a heel angle of 30o is a
good design angle. This corresponds to a reasonably high wind strength
with the sails still generating high loads and the boat making good
speed through the water.

That doesn't sound right to me.

My boat definitely performs better at a smaller angle of heel. I'd say 15 -
20o. Beyond 20o, performance begins to suffer.

Of course, some boats are designed to sail well when keeled over. Some of
the mini TransAts have keels that are adjustable sideways, *and* also have
an adjustable angle of attack!!! These keels are known as "3D" keels.



Regards


Donal
--

No nno no. You must be wrong. Doughn says it's 12 degrees heel thats best.

But seriously, I'm just quoting reference texts. As you boat is a Farr,
I suggest she'll will go faster at closer to 30 degrees heel beating
than if you ease off the sails and stand her up to just 20 degrees. Look
at your instruments. Try it and get back to me. You'll need 20 knots of
wind of course nand don't forget to lower the traveller if the helm is
getting too much.

Cheers

Donal wrote:

"Nav" wrote in message
...

“The starting point when dimensioning the rig is to calculate the
righting moment. It is commonly agreed that a heel angle of 30o is a
good design angle. This corresponds to a reasonably high wind strength
with the sails still generating high loads and the boat making good
speed through the water.


That doesn't sound right to me.

My boat definitely performs better at a smaller angle of heel. I'd say 15 -
20o. Beyond 20o, performance begins to suffer.

Of course, some boats are designed to sail well when keeled over. Some of
the mini TransAts have keels that are adjustable sideways, *and* also have
an adjustable angle of attack!!! These keels are known as "3D" keels.



Regards


Donal
--

Oz wrote:

On Wed, 4 Feb 2004 00:30:12 -0000, "Donal"
scribbled thusly:


That doesn't sound right to me.

My boat definitely performs better at a smaller angle of heel. I'd say 15 -
20o. Beyond 20o, performance begins to suffer.


Upwind?
Nah, closer to 30 than 20 I'm sure.

Then again, you've always maintained that you're a novice.
Crank it on, heel her over and balance her up.
You should nearly be able to steer her with the traveller...Honest!



No you've got it wrong Oz, just like these guys

http://www.yachtsoft.com/IMAGES/eagle1.jpg

Doug assures us that anthing over 12 degrees must be bad.

But seriously, would you say that in most cases the optimum is about
where the rail starts to get close to the water so that it's wet but to
getting greenies?

Cheers

Nav wrote:



Oz wrote:

On Wed, 4 Feb 2004 00:30:12 -0000, "Donal"
scribbled thusly:


That doesn't sound right to me.

My boat definitely performs better at a smaller angle of heel. I'd
say 15 -
20o. Beyond 20o, performance begins to suffer.



Upwind?
Nah, closer to 30 than 20 I'm sure.

Then again, you've always maintained that you're a novice.
Crank it on, heel her over and balance her up.
You should nearly be able to steer her with the traveller...Honest!



No you've got it wrong Oz, just like these guys

http://www.yachtsoft.com/IMAGES/eagle1.jpg

Doug assures us that anthing over 12 degrees must be bad.

But seriously, would you say that in most cases the optimum is about
where the rail starts to get close to the water so that it's wet but to
getting greenies?

Cheers

Damn tyo's. I mean:

But seriously, would you say that in most cases the optimum is about
where the rail starts to get close to the water so that it's wet but
not getting any greenies?


Cheers

Doug give it up. It's like pushing an overboiled noodle uphill. It's
fustrating, tedious and you know better.



"DSK" wrote in message
...
Nav wrote:
Note the _more_!!!! Now, who's talking efficiency? We were talking about
powered up! (I now accept that you may have no idea what that means).
Now define effciency for us so we can be sure that we are going to speak
the same language if you want to discuss efficiency.

I would say that "greatest sailing efficiency" could be defined as the
conditions (both weather and sail) that provided the highest VMG to
windward possible for that design.

Do the newest IACC boats go the fastest at 30 degrees of heel? That is
what you seem to be saying.

For most boats, the polars show the highest VMG in the 10 to 15 knot
wind range and sailing conditions of less than 20 degrees of heel. As I
said, narrow boats like to heel more but I'd be surprised if it were
that much more. I'm not very familiar with the last generation IACC boat
polars, maybe there are some on line.

Fresh Breezes- Doug King

Oz wrote in message ...
On Wed, 4 Feb 2004 00:30:12 -0000, "Donal"
scribbled thusly:

That doesn't sound right to me.

My boat definitely performs better at a smaller angle of heel. I'd say
15 -
20o. Beyond 20o, performance begins to suffer.

Upwind?
Nah, closer to 30 than 20 I'm sure.

Maybe. I just know that she goes faster when we reef earlier.


Then again, you've always maintained that you're a novice.
Crank it on, heel her over and balance her up.
You should nearly be able to steer her with the traveller...Honest!

We've done that a couple of times. Better than sex!! I've reported it
here. The last time, some of the crew didn't understand why 8.5 kts was so
fantastic. They pointed out that we had done 12 kts earlier in the day....
They didn't understand that we were doing 8.5 kts *into* wind - in a 33 ft
boat!




Regards


Donal
--