Evan Gatehouse wrote:
Gary wrote:

I think the stability curves are wrong. If you plug
the numbers into the formulas at US sailing you get a
much higher AVS. 110 degrees just doesn't make sense.
Not only that but the 460's keel, although seemingly a
little light, is bulbous with the weight quite low.
Something is wrong with that graph.

Gaz

I didn't find the formula at US Sailing's site but...How do
you find AVS without using a sophisticated stability program
that knows the shape of the hull?

The US Sailing formula may give an indication of ultimate
stability (the capsize screening formula) but that is a very
simple rule of thumb.

The inclining experiment data, which does determine the VCG
of the real boat, is plugged into a stability program
(GHS/Autohydro etc.) that gives the stability curve.

Robert has retired fairly recently but he should be able to
help you with your questions.

Evan Gatehouse

Thank you very much for your help. The dealer said he was
going to call Robert Harris for me regarding my concern.
If his design isn't as bad as the report suggests he'll probably
be happy to explain to me why I shouldn't worry too much
about the stability of this boat.

Evan Gatehouse wrote:
Gary wrote:

I think the stability curves are wrong. If you plug the numbers into
the formulas at US sailing you get a much higher AVS. 110 degrees
just doesn't make sense. Not only that but the 460's keel, although
seemingly a little light, is bulbous with the weight quite low.
Something is wrong with that graph.

Gaz


I didn't find the formula at US Sailing's site but...How do you find AVS
without using a sophisticated stability program that knows the shape of
the hull?

The US Sailing formula may give an indication of ultimate stability (the
capsize screening formula) but that is a very simple rule of thumb.

The inclining experiment data, which does determine the VCG of the real
boat, is plugged into a stability program (GHS/Autohydro etc.) that
gives the stability curve.

Robert has retired fairly recently but he should be able to help you
with your questions.

Evan Gatehouse
Try he http://www.sailingusa.info/keelboat.htm
Under sailing calculators in the right find angle of vanishing stability.

The problem with the inclining data is that it only takes hull shape and
weight distribution into account. It doesn't allow for things like
pilothouses or foam filled masts. I still think the curve is wrong and
Tayanas claim of an AVS of 0 is probably correct.

Gary wrote:
Evan Gatehouse wrote:

Gary wrote:

I think the stability curves are wrong. If you plug the numbers into
the formulas at US sailing you get a much higher AVS. 110 degrees
just doesn't make sense. Not only that but the 460's keel, although
seemingly a little light, is bulbous with the weight quite low.
Something is wrong with that graph.

Gaz



I didn't find the formula at US Sailing's site but...How do you find
AVS without using a sophisticated stability program that knows the
shape of the hull?

The US Sailing formula may give an indication of ultimate stability
(the capsize screening formula) but that is a very simple rule of thumb.

The inclining experiment data, which does determine the VCG of the
real boat, is plugged into a stability program (GHS/Autohydro etc.)
that gives the stability curve.

Robert has retired fairly recently but he should be able to help you
with your questions.

Evan Gatehouse

Try he http://www.sailingusa.info/keelboat.htm
Under sailing calculators in the right find angle of vanishing stability.

The problem with the inclining data is that it only takes hull shape and
weight distribution into account. It doesn't allow for things like
pilothouses or foam filled masts. I still think the curve is wrong and
Tayanas claim of an AVS of 0 is probably correct.

O.k. I'm a polite guy on usenet but you sir are totally
wrong and beginning to **** me off. I'm a naval architect.
I do this stuff for a living.

The stupid calculator only is used to give an ESTIMATE of
the AVS.

An inclining experiment establishes the VCG of the boat in a
real world test. It does NOT calculate the AVS. For that
you need software that does take into account the shape of
the hull and the pilothouse. GHS and Autohydro DO that!
You could model a foam filled mast as part of the model if
you wished. They are far more trustworthy and are accepted
by USCG for stability calculations of commercail vessels

Here's the formula from US Sailings site. Note that in the
last line, the formula says the AVS = 110 + .....

This says that the AVS is ALWAYS going to be = 110. There
are lots of boats that are 110!

From US Sailings web site:
" This formula gives an estimate of the angle of vanishing
stability or the angle the boat can heel and still right
itself. This formula does not fully take into account the
vertical position of the center of gravity (VCG)."

Screening Stability Value ( SSV ) = ( Beam 2 ) / ( BR * HD
* DV 1/3 )

BR: Ballast Ratio ( Keel Weight / Total Weight )

HD: Hull Draft

DV: The Displacement Volume in cubic meters. DV is
entered as pounds of displacement on the webpage and
converted to cubic meters by the formula:

Displacement Volume in Cubic Meters = ( Weight in
Pounds / 64 )*0.0283168

The Beam and Hull Draft in this formula are in meters.
These values are entered in feet on the webpage and are
converted to meters before SSV calculation.

Angle of Vanishing Stability approximately equals
110 + ( 400 / (SSV-10) )

Evan Gatehouse wrote:
Gary wrote:

Evan Gatehouse wrote:

Gary wrote:

I think the stability curves are wrong. If you plug the numbers
into the formulas at US sailing you get a much higher AVS. 110
degrees just doesn't make sense. Not only that but the 460's keel,
although seemingly a little light, is bulbous with the weight quite
low. Something is wrong with that graph.

Gaz




I didn't find the formula at US Sailing's site but...How do you find
AVS without using a sophisticated stability program that knows the
shape of the hull?

The US Sailing formula may give an indication of ultimate stability
(the capsize screening formula) but that is a very simple rule of thumb.

The inclining experiment data, which does determine the VCG of the
real boat, is plugged into a stability program (GHS/Autohydro etc.)
that gives the stability curve.

Robert has retired fairly recently but he should be able to help you
with your questions.

Evan Gatehouse


Try he http://www.sailingusa.info/keelboat.htm
Under sailing calculators in the right find angle of vanishing stability.

The problem with the inclining data is that it only takes hull shape
and weight distribution into account. It doesn't allow for things
like pilothouses or foam filled masts. I still think the curve is
wrong and Tayanas claim of an AVS of 0 is probably correct.


O.k. I'm a polite guy on usenet but you sir are totally wrong and
beginning to **** me off. I'm a naval architect. I do this stuff for a
living.

The stupid calculator only is used to give an ESTIMATE of the AVS.

An inclining experiment establishes the VCG of the boat in a real world
test. It does NOT calculate the AVS. For that you need software that
does take into account the shape of the hull and the pilothouse. GHS
and Autohydro DO that! You could model a foam filled mast as part of the
model if you wished. They are far more trustworthy and are accepted by
USCG for stability calculations of commercail vessels

Here's the formula from US Sailings site. Note that in the last line,
the formula says the AVS = 110 + .....

This says that the AVS is ALWAYS going to be = 110. There are lots of
boats that are 110!

From US Sailings web site:
" This formula gives an estimate of the angle of vanishing stability or
the angle the boat can heel and still right itself. This formula does
not fully take into account the vertical position of the center of
gravity (VCG)."

Screening Stability Value ( SSV ) = ( Beam 2 ) / ( BR * HD * DV 1/3 )

BR: Ballast Ratio ( Keel Weight / Total Weight )

HD: Hull Draft

DV: The Displacement Volume in cubic meters. DV is entered as
pounds of displacement on the webpage and converted to cubic meters by
the formula:

Displacement Volume in Cubic Meters = ( Weight in Pounds / 64
)*0.0283168

The Beam and Hull Draft in this formula are in meters. These values
are entered in feet on the webpage and are converted to meters before
SSV calculation.

Angle of Vanishing Stability approximately equals
110 + ( 400 / (SSV-10) )


Glad I'm getting to you Nav Arch. You do seem to have a grasp on the
above formulae but fail to explain why the boat has an AVS of 110 in the
graph and yet the designer and builder both claim it has a much greater
AVS. In fact the extremely high AVS of the Tayana Vancouver 460 is
discussed in many places around the net. There is no way the AVS is 110.

If you really are a Nav Arch and do this for a living, then do it for
us. Work out the numbers using your program and the data available and
give us your results (which are still only an estimate). As a Nav Arch
it should only take you a couple minutes. Right????

You also earlier said :
"- the ballast/displacement ratio is overly low, meaning a tender boat
with not enough stability "
A Nav Arch would know that initial stability is more than lots of
ballast. A raft has no ballast and is not tender. Wouldn't you say
that you are jumping to conclusions by not taking into account hull form
and the location of the ballast?
In other articles on the net, they also talk of the boat as "stiff" and
"stands up to her sails well".

Your turn.

Gaz

Gary wrote:
Evan Gatehouse wrote:

Gary wrote:

Evan Gatehouse wrote:

Gary wrote:

I think the stability curves are wrong. If you plug the numbers
into the formulas at US sailing you get a much higher AVS. 110
degrees just doesn't make sense. Not only that but the 460's keel,
although seemingly a little light, is bulbous with the weight quite
low. Something is wrong with that graph.

Gaz


O.k. I'm a polite guy on usenet but you sir are totally wrong and
beginning to **** me off. I'm a naval architect. I do this stuff for
a living.

The stupid calculator only is used to give an ESTIMATE of the AVS.

An inclining experiment establishes the VCG of the boat in a real
world test. It does NOT calculate the AVS. For that you need
software that does take into account the shape of the hull and the
pilothouse. GHS and Autohydro DO that! You could model a foam filled
mast as part of the model if you wished. They are far more trustworthy
and are accepted by USCG for stability calculations of commercail vessels

Gary wrote

Glad I'm getting to you Nav Arch. You do seem to have a grasp on the
above formulae but fail to explain why the boat has an AVS of 110 in the
graph and yet the designer and builder both claim it has a much greater
AVS. In fact the extremely high AVS of the Tayana Vancouver 460 is
discussed in many places around the net. There is no way the AVS is 110.

If you really are a Nav Arch and do this for a living, then do it for
us. Work out the numbers using your program and the data available and
give us your results (which are still only an estimate). As a Nav Arch
it should only take you a couple minutes. Right????

You also earlier said :
"- the ballast/displacement ratio is overly low, meaning a tender boat
with not enough stability "
A Nav Arch would know that initial stability is more than lots of
ballast. A raft has no ballast and is not tender. Wouldn't you say
that you are jumping to conclusions by not taking into account hull form
and the location of the ballast?
In other articles on the net, they also talk of the boat as "stiff" and
"stands up to her sails well".

Your turn.

Gaz
Okay, my turn again. I just googled you and see you may be a Nav Arch.
So why don't you calculate the AVS?

I am quite confident (and I am not a Nav Arch) that the boat will have a
better stability curve than is represented by the one posted.

If it doesn't, and it has an AVS of 110, I wouldn't touch it for
anything but coastal wandering. It will surprise me because the AVS
claims for the 460 are 0 degrees on all the Tayana websites and the
other Harris boats are so seaworthy.

Really though, since we are not doing the buying, this is just an
interesting discussion. No need to get ****ed off.

Gary

Gary wrote:
Okay, my turn again. I just googled you and see you may
be a Nav Arch. So why don't you calculate the AVS?

I am quite confident (and I am not a Nav Arch) that the boat
will have a better stability curve than is represented by the
one posted.

If it doesn't, and it has an AVS of 110, I wouldn't touch it
for anything but coastal wandering. It will surprise me
because the AVS claims for the 460 are 0 degrees on all the
Tayana websites and the other Harris boats are so seaworthy.

Really though, since we are not doing the buying, this is
just an interesting discussion. No need to get ****ed off.

The report including the curve was sent to me by Tayana's
engineer named Basil last Sunday (Monday in Taiwan).

"Nice to talk with you. Re AVS of Vancouver 460 is 110 degrees.
... Enclosed the report of inclining experiment total 3 pages.
The last page shown the GZ curve. Please let me know if you
have more questions."

The AVS was probably determined from the curve but I don't
know if they actually closed all the hatches and turned the
boat upside down for the inclining experiment :-)

BTW, didn't somebody recommend a Catalina (with an AVS of 105)
over this Tayana and the Beneteaus for crossing the Pacific ?

I've got this report from Tayana for the Vancouver 460 Pilot
but don't know how good it is.

http://tayana46.tripod.com/safety.htm

I have another idea.

Since this boat has a 325-gallon fuel tank and a 240-gallon
water tank and the inclining experiment was done with all
tanks half full, would I be able to significantly improve on
the stability if I fill up all the tanks for my offshore cruising ?

I can install a watermaker and solar panels so I won't have to
draw too much water and fuel from these tanks.

wrote:
Gary wrote:

Okay, my turn again. I just googled you and see you may
be a Nav Arch. So why don't you calculate the AVS?

I am quite confident (and I am not a Nav Arch) that the boat
will have a better stability curve than is represented by the
one posted.

If it doesn't, and it has an AVS of 110, I wouldn't touch it
for anything but coastal wandering. It will surprise me
because the AVS claims for the 460 are 0 degrees on all the
Tayana websites and the other Harris boats are so seaworthy.

Really though, since we are not doing the buying, this is
just an interesting discussion. No need to get ****ed off.


The report including the curve was sent to me by Tayana's
engineer named Basil last Sunday (Monday in Taiwan).

"Nice to talk with you. Re AVS of Vancouver 460 is 110 degrees.
.. Enclosed the report of inclining experiment total 3 pages.
The last page shown the GZ curve. Please let me know if you
have more questions."

The AVS was probably determined from the curve but I don't
know if they actually closed all the hatches and turned the
boat upside down for the inclining experiment :-)

BTW, didn't somebody recommend a Catalina (with an AVS of 105)
over this Tayana and the Beneteaus for crossing the Pacific ?
When they do an inclining experiment with a boat they just force it to
incline by putting weights a certain distance from the centreline and
then calculate all the numbers from that data. They don't turn the boat
over. Everything on the boat is supposed to be in normal operating
condition.

When people on this group or anywhere recommend things like the Catalina
you have to take it all with a grain of salt. Remember this is just a
news group. I could be a 12 year old.

Finally your questions, although thought provoking and the basis for
good discussion, are kind of revealing when it comes to your level of
seamanship and experience. You could probably sail just about any 46
foot modern boat just about anywhere. The differences are nuances and
margins of safety. Almost no-one buys a boat based solely on it's
stability curves. In fact the open 60s/70s currently racing around the
globe have terrible stability profiles, so much so that they have to
prove that they can right them once tipped. They are sailing in extreme
conditions on the edge of control.

As Adlard Coles often says in his "Heavy Weather Sailing" classic' it
is the skill of the crew that is the biggest factor in the safety of the
boat. (You should read it) A 30' breaking wave will capsize any poorly
handled 45 foot boat on a bad day.

Gaz

wrote:
I've got this report from Tayana for the Vancouver 460 Pilot
but don't know how good it is.

http://tayana46.tripod.com/safety.htm


I have another idea.

Since this boat has a 325-gallon fuel tank and a 240-gallon
water tank and the inclining experiment was done with all
tanks half full, would I be able to significantly improve on
the stability if I fill up all the tanks for my offshore cruising ?

I can install a watermaker and solar panels so I won't have to
draw too much water and fuel from these tanks.
I think I read that the latest 460 even has some water displacement
ballast but you should not count on fuel and water for ultimate
stability as when the survival storm happens you may not have full
tanks. If stability is a problem then the solar panels will add even
more top hamper.

I am really interested in what Mr Harris and Tayana have to say about
the stability of the 460.

Gaz

Gary wrote:
Okay, my turn again. I just googled you and see you may be a Nav Arch.

I've met Mr. Gatehouse and he is indeed a Naval Architect
and a good one.

So why don't you calculate the AVS?

Because (as he's been trying to tell you) it requires more data.


I am quite confident (and I am not a Nav Arch) that the boat will have a
better stability curve than is represented by the one posted.

Based on what? Your gut feeling?


If it doesn't, and it has an AVS of 110, I wouldn't touch it for
anything but coastal wandering.

Now here I agree. An LPOS (or AVS or whatever the TLA de
jour is) of 110 is far too low for any kind of rough weather
sailing even near coasts.

Going back a little bit

You also earlier said :
"- the ballast/displacement ratio is overly low, meaning a tender boat
with not enough stability "
A Nav Arch would know that initial stability is more than lots of
ballast.

Right, in fact the B/D ratio has little effect on *initial*
stability. But notice that in the original sentence, the
word "stability" was used, not the phrase "initial stability".

A boat can have very high initial stability and great sail
carrying power, but a very low LPOS (think scows or
catamarans). A very different type of boat can have low
initial stability and lots of ballast for lots of *reserve*
stability... ie steeply increasing righting moment at higher
angles of heel. A lot of old fashioned narrow heavy boats
are said to "heel only so far, and then stiffen up like a
rock." A boat like this can sail well at higher angles of
heel if the hull shape is fair & the rig/rudder are balanced
well. It can also have a very high LPOS yet be very
unsearthy.... think of the Twelve Meters.


... A raft has no ballast and is not tender. Wouldn't you say
that you are jumping to conclusions by not taking into account hull
form and the location of the ballast?

Umm, no... from the discussion so far, I'd say that you are
the one doing exactly that.

In other articles on the net, they also talk of the boat as "stiff"
and "stands up to her sails well".


That can easily be a function of her SA/D ratio as much as
hull form & ballast.

Fresh Breezes- Doug King