Urgent ! Can anyone understand these safety data ?
 

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.

Urgent ! Can anyone understand these safety data ?
 

Why is everything you post "Urgent!"?

Doesn't seem urgent to me; more like you don't know what you're doing,
feel you have to do it now, and don't want to do the research
yourself.

Urgent ! Can anyone understand these safety data ?
 

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.

The pilothouse likely won't make the boat any less stable than the boat
without it. In fact, if the boat was to ever go blow 90 degrees the
pilothouse would add to the righting moment with its' great buoyancy.

The Righting Arm vs Heel Curve is quite telling and disturbing. Ideally
the area under the curve when the boat is upside down is significantly
smaller than the area under the curve when the boat is right side up.
In this instance the area under the curve is fairly large indicating
that the boat is quite stable upside down. In fact it is almost as
stable upside down as it is right side up. Not great.

According to this curve the Angle of Vanishing Stability (AVS) is about
110 degrees. That is unsatisfactory. Most offshore boats are designed
with an AVS in excess of 120 degrees.

After looking around the net I would have to say that this graph of RA
vs HC is wrong. Tayana claims an AVS of 0 degrees which would make
sense given the buoyancy of the pilothouse (Provided the windows don't
break).

Check out: http://www.tayanayachts.com.tw/V460.htm

I would rather the Tayana over the Beneteau.

Urgent ! Can anyone understand these safety data ?
 

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

Urgent ! Can anyone understand these safety data ?
 

Gary 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.

The pilothouse likely won't make the boat any less stable than the boat
without it. In fact, if the boat was to ever go blow 90 degrees the
pilothouse would add to the righting moment with its' great buoyancy.

The Righting Arm vs Heel Curve is quite telling and disturbing. Ideally
the area under the curve when the boat is upside down is significantly
smaller than the area under the curve when the boat is right side up.
In this instance the area under the curve is fairly large indicating
that the boat is quite stable upside down. In fact it is almost as
stable upside down as it is right side up. Not great.

According to this curve the Angle of Vanishing Stability (AVS) is about
110 degrees. That is unsatisfactory. Most offshore boats are designed
with an AVS in excess of 120 degrees.

After looking around the net I would have to say that this graph of RA
vs HC is wrong. Tayana claims an AVS of 0 degrees which would make
sense given the buoyancy of the pilothouse (Provided the windows don't
break).

Check out: http://www.tayanayachts.com.tw/V460.htm

I would rather the Tayana over the Beneteau.

As mentioned in the other thread, the numbers and curve on my
web site were given to me by Tayana.

With the pilothouse filled with air I would also expect this boat
to have no stable state upside down. But in this case shouldn't
the AVS be 180 degrees instead of 0 ?

Urgent ! Can anyone understand these safety data ?
 

wrote:
Why is everything you post "Urgent!"?

Doesn't seem urgent to me; more like you don't know
what you're doing, feel you have to do it now, and
don't want to do the research yourself.

It's no longer urgent because I've already decided to
withdraw my offer for the Beneteau 473.

Urgent ! Can anyone understand these safety data ?
 

The broker(s) you're working with must love you.


On Tue, 06 Dec 2005 08:20:46 GMT, wrote:

It's no longer urgent because I've already decided to
withdraw my offer for the Beneteau 473.

Urgent ! Can anyone understand these safety data ?
 

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

Urgent ! Can anyone understand these safety data ?
 

wrote:
Gary 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.


The pilothouse likely won't make the boat any less stable than the boat
without it. In fact, if the boat was to ever go blow 90 degrees the
pilothouse would add to the righting moment with its' great buoyancy.

The Righting Arm vs Heel Curve is quite telling and disturbing. Ideally
the area under the curve when the boat is upside down is significantly
smaller than the area under the curve when the boat is right side up.
In this instance the area under the curve is fairly large indicating
that the boat is quite stable upside down. In fact it is almost as
stable upside down as it is right side up. Not great.

According to this curve the Angle of Vanishing Stability (AVS) is about
110 degrees. That is unsatisfactory. Most offshore boats are designed
with an AVS in excess of 120 degrees.

After looking around the net I would have to say that this graph of RA
vs HC is wrong. Tayana claims an AVS of 0 degrees which would make
sense given the buoyancy of the pilothouse (Provided the windows don't
break).

Check out: http://www.tayanayachts.com.tw/V460.htm

I would rather the Tayana over the Beneteau.


As mentioned in the other thread, the numbers and curve on my
web site were given to me by Tayana.

With the pilothouse filled with air I would also expect this boat
to have no stable state upside down. But in this case shouldn't
the AVS be 180 degrees instead of 0 ?
It doesn't really matter how you say it, as long as we both understand
that the boat will not stay upside down.

Urgent ! Can anyone understand these safety data ?
 

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

Urgent ! Can anyone understand these safety data ?
 

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.

Urgent ! Can anyone understand these safety data ?
 

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.

Urgent ! Can anyone understand these safety data ?
 

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) )

Urgent ! Can anyone understand these safety data ?
 

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

Urgent ! Can anyone understand these safety data ?
 

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

Urgent ! Can anyone understand these safety data ?
 

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 ?

Urgent ! Can anyone understand these safety data ?
 

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.

Urgent ! Can anyone understand these safety data ?
 

Urgent ! Can anyone understand these safety data ?
 

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

Urgent ! Can anyone understand these safety data ?
 

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

Urgent ! Can anyone understand these safety data ?
 

DSK wrote:
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?
No, based on the claims of Tayana of 0 degrees AVS (LOPS). Also based
on the high freeboard and massive pilothouse.


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".
In fact he used the term tender which is normally associated with
initial stability. He said the boat would be tender (tippy or lack
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.

No-one ever claimed that LOPS is the only factor determining seaworthiness.


... 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.

I am simply trying to understand how the inclining experiment can come
up with an AVS (LOPS) of 110 on a boat that claims a much greater AVS.
In the above statement, I was pointing out to Mr. Gatehouse that his
estimate of the 460 being "tender" based on the LOPS and ballast ratio
was not necessarily correct. But he should know, he sails a cat. (No
ballast)

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

Urgent ! Can anyone understand these safety data ?
 

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


Gary wrote:
I am simply trying to understand how the inclining experiment can come
up with an AVS (LOPS) of 110 on a boat that claims a much greater AVS.

Well, the incline experiment is a real world measure of
actual stability. In the absence of a test to, say maybe 100
degrees or so, I'd be inclined to consider the incline
experiment as a less certain way of finding LPOS than the
longhand method using the full lines plan.... but a far more
certain way of determining it than using the "short hand"
method based on simple ratios & a fixed input number.

AFAIK nobody ever said the Tayana had an LPOS of 110 degrees
but Evan Gatehouse was pointing out that the mathematical
formula used to derive it's claimed LPOS used 110 degrees as
a fixed input no matter what the boat or hull type.

In the above statement, I was pointing out to Mr. Gatehouse that his
estimate of the 460 being "tender" based on the LOPS and ballast ratio
was not necessarily correct. But he should know, he sails a cat. (No
ballast)


Before that, he owned & sailed & cruised a real crab
crusher. IMHO the gentleman knows that of which he speaks.

Fresh Breezes- Doug King

Urgent ! Can anyone understand these safety data ?
 

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



Gary wrote:

I am simply trying to understand how the inclining experiment can come
up with an AVS (LOPS) of 110 on a boat that claims a much greater AVS.


Well, the incline experiment is a real world measure of actual
stability. In the absence of a test to, say maybe 100 degrees or so, I'd
be inclined to consider the incline experiment as a less certain way of
finding LPOS than the longhand method using the full lines plan.... but
a far more certain way of determining it than using the "short hand"
method based on simple ratios & a fixed input number.
I am aware of how incline experiments work. I'm not sure which way is
the better to calculate AVS.

AFAIK nobody ever said the Tayana had an LPOS of 110 degrees but Evan
Gatehouse was pointing out that the mathematical formula used to derive
it's claimed LPOS used 110 degrees as a fixed input no matter what the
boat or hull type.
The original graphs posted by Popeye calculated the AVS at 110. That
was the genesis of the discussion.

In the above statement, I was pointing out to Mr. Gatehouse that his
estimate of the 460 being "tender" based on the LOPS and ballast ratio
was not necessarily correct. But he should know, he sails a cat. (No
ballast)


Before that, he owned & sailed & cruised a real crab crusher. IMHO the
gentleman knows that of which he speaks.
What's a crab crusher?

Fresh Breezes- Doug King