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

If anybody can understand the Righting Arms vs Heel curve and
the numbers on this web page please let me know.

The consensus here seems to be that Tayanas in general are safer
bluewater yachts but I don't know if the pilothouse makes this
Vancouver 460 less stable or more dangerous.

Thanks again for your help.

I can understand this stuff. The stability of this boat
sucks to put it politely.

I've met Robert Harris. He's a good guy who has designed
some nice boats (the Vancouver 27/42 come to mind). But
this doesn't seem like one of the better built ones.

- Angle of vanishing stability of 110 degrees is pretty low.
I wouldn't go offshore in that sort of boat. Even fat
cruising Beneteaus manage better than 115 usually.

- the displacement is really quite high but it is to be
believed because they actually calculated it based on
measured drafts

- the ballast/displacement ratio is overly low, meaning a
tender boat with not enough stability

- the calculated GM is low (not a good thing; should be 3-
3.5' min.)

- the VCG is high (not good) at 1.32' above DWL. I suspect
the pilothouse is contributing to the high VCG

- the righting arm curve is ugly. The area under the 0 part
of the curve should not be nearly the same size as the
portion above. Maybe they were not including the pilothouse
in the calculation but I think it is there (see the bump in
the curve at ~70 degrees).

Summary: probably the pilothouse has made it too top heavy
to be an ideal offshore boat. Due to the size it won't be
knocked down or rolled easily, but if it does, it will take
a lot of wave action to re-right her and she will likely to
be upside down for quite some minutes. I would look elsewhere.

Evan Gatehouse

Evan Gatehouse wrote:
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

If anybody can understand the Righting Arms vs Heel curve and
the numbers on this web page please let me know.

The consensus here seems to be that Tayanas in general are safer
bluewater yachts but I don't know if the pilothouse makes this
Vancouver 460 less stable or more dangerous.

Thanks again for your help.


I can understand this stuff. The stability of this boat sucks to put it
politely.

I've met Robert Harris. He's a good guy who has designed some nice
boats (the Vancouver 27/42 come to mind). But this doesn't seem like
one of the better built ones.

- Angle of vanishing stability of 110 degrees is pretty low. I wouldn't
go offshore in that sort of boat. Even fat cruising Beneteaus manage
better than 115 usually.

- the displacement is really quite high but it is to be believed because
they actually calculated it based on measured drafts

- the ballast/displacement ratio is overly low, meaning a tender boat
with not enough stability

- the calculated GM is low (not a good thing; should be 3- 3.5' min.)

- the VCG is high (not good) at 1.32' above DWL. I suspect the
pilothouse is contributing to the high VCG

- the righting arm curve is ugly. The area under the 0 part of the
curve should not be nearly the same size as the portion above. Maybe
they were not including the pilothouse in the calculation but I think it
is there (see the bump in the curve at ~70 degrees).

Summary: probably the pilothouse has made it too top heavy to be an
ideal offshore boat. Due to the size it won't be knocked down or rolled
easily, but if it does, it will take a lot of wave action to re-right
her and she will likely to be upside down for quite some minutes. I
would look elsewhere.

Evan Gatehouse

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

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

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