Can either of these types of boats, and similar voyaging boats handle a
knockdown and recover. How about a barrell roll. I'm not being sarcastic, I
want to know the facts, and, I really like both of them, they just look
awesome !> Date: Sat, 31 Mar 2007 07:17:27 +0200> From: mygoleen@gmail.com>
To: passagemaking-under-power@lists.samurai.com> Subject: Re: [PUP] Scelenes
vs Nordhavns> > Hi Bob (and all),> > You wrote:"Nordhavn has done this
brilliantly in their marketing and> advertising campaigns."> > Yes, they
certainly do and I feel that after we purchase a boat, it is our>
responsibility too to keep her in good shape and visiting the 'engine room'>
often and not only when things goes wrong, is a MUST!> > You said:"One needs
to either be able to fix them, or do without"> > Absolutely! On Goleen we keep
our engine room not only sparkling clean, if> possible, but with an eye on
everything at all times to spot signs of wear> and tear. OF COURSE, THINGS CAN
GO WRONG NO MATTER, AND NOT ONLY ON THE> ENGINE ROOM!> > On passages, we visit
the engine room very often and Chris measure> temperatures, search places for
possible leaks, fuel levels, fuel filters> and so on.> I hardly even hear
music on board when we are on a passage because I like to> hear if the engine
'sound' is the same or if it changed in any way, which is> one of the first
signs of trouble ahead, if it changes.> I do appreciate that it is difficult
for any of us, and even for the> 'engeneer's types' to know it all, but one
need to be prepared to take> action and do something on the spot and
sometimes, FAST.> > We had problems before that we didn't know how to fix it
immediately so, we> opened the manual and read' or made a phone call and
listened.> If one is prepared mentally, physically and emotionally for this
kind of> event to happen, it should be fine, and THAT is why I keep banging on
the> key on this forum that talking about HOW we cope ( and not ONLY about
'WHAT> WE DO') in adversity is important too. In the end it will be our
mental> state that will save the technical issues (and ourselves) when 'push
comes> to shave', in MY opinion.> > Just to illustrate:> On Yachting World,
April edition, 'Run down at Night', pg 80/85, Clark Beek> wrote about his
experience of his 40ft ketch Condesa been run down by> a freighter:> > > Pure
Panic paragraph:> "Let me state for the record that I am not proud of what I
did. This was> one act of pure panic.> ...I did a freestyle sprint at a
speed only possible when that sort of> adrenalin is pumping through one's
veins, tumble in a crashing bow wave,> then sprinted again. Ian (his crew)
would have been right behind me,> following my stupid lead, but because of
Hilary (his other crew was stuck> inside the vessel*) he missed his chance at
being the second human in> history to bodysurf a freighter's bow wave."*> >
And he goes on: " My most important piece of advice is this: plan to be an>
idiot. I always considered myself a pretty cool customer under fire, but> when
life and vessel were on the line I found myself functioning at about 10> per
cent of mental and physical capability. It made me re-evaluate some of> my
emergency procedures omboard because they are too complicated for a> rattle
mind."> **> You see what I mean?> > All the best and keep learning,> > Sonaia
Hermida> NH 5729> > > On 3/30/07, thataway4@cox.net thataway4@cox.net
wrote:> >> > My impression looking at 2 or 3 year old Nordhavn's vs the same
age Selene> > is that the Nordhavn ages bettter.> >> > There are some design
features including seating on the flying bridge,> > engine room access which I
like better on the Nordhavn.> >> > Any new boat will have problems. I spent
over 3 months getting issues> > repaired on a new boat last year. Further
more, with time many systems on> > boats will either wear or fail. One needs
to either be able to fix them, or> > do without. If one looks at the Nordhavn
40 around the world--there were a> > number of issues, if one studies all of
the reports from the boat and> > various people aboard.> >> > I also need to
clarify a word which may have caused some> > confusion: Scheme: " A systematic
program for obtaining some objective" is> > Webster's first
defination--Nordhavn has done this brilliantly in their> > marketing and
advertising campaigns.> >> > Bob Austin> >
_______________________________________________> >> > Passagemaking Under
Power and PUP are trademarks of Water World> > Productions, formerly known as
Trawler World Productions.> >> > To be removed from the PUP list send an email
with the> > subject "unsubscribe" (no quotes) to the link below:> >> >
mailto:passagemaking-under-power-request@lists.samurai.com> >> >
Passagemaking-Under-Power Mailing List>
_______________________________________________> > Passagemaking Under Power
and PUP are trademarks of Water World Productions, formerly known as Trawler
World Productions.> > To be removed from the PUP list send an email with the>
subject "unsubscribe" (no quotes) to the link below:> >
mailto:passagemaking-under-power-request@lists.samurai.com> >
Passagemaking-Under-Power Mailing List

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Bob:

You'd have to define "a knockdown". All boats have a "limit of positive
stability" (LPS) -- an angle of heel after which the boat loses its righting
moment and will tend to go on and roll over. Even sailboats have such a
limit, though it tends to be much larger on sailboats.

For example, my previous sailboat, a 43' J/130 had an LPS of about 130
degrees. That means that even if the mast was 40 degrees underwater, the
boat would still have righting moment to pull it back upright. After that,
the boat will probably finish going over. However, with a very high LPS, the
chances are, the boat will go right on over and right itself again because
either momentum or another wave will tend to roll the boat on over until it
reaches that positive stability limit again and right itself.

Unfortunately, very few, if any trawler style boats have LPS numbers even
approaching the values for most sailboats. I've never seen the number
published for Nordhavns, Krogens, Selens, etc.. My suspicion is that the
number is more like 45 to 60 degrees for both.

Metacentric height is one measure of stability that some of the
manufacturers do publish--you should be able to ask for the number if it
isn't published. For a definition of Metacentric height, see:
http://www.selenetrawlers.com/2008/iindex.php?O=Page&F=AU&S=4
(scroll down this page about 2/3 of the way down).

A larger metacentric height means more righting moment, and a higher limit
of positive stability, though I don't know of any direct way to convert
metacentric height to a limit of positive stability.

For the Selene 53, for example, the web site lists the metacentric height
(GM) as 4' 10-5". This means that the center of gravity of the boat is
almost 5' below the metacenter (the "hinge point" around which the boat
rolls). That's pretty good. I looked on the Nordhavn site, but couldn't find
metacentric height specified there. Perhaps it's on printed spec sheets.

Of course, it's important to recognize that we owners affect the stability
of our boats by how we load them as well. Heavy dinghys stored up high on
flybridge decks have a substantial influence as well (they obviously raise
the center of gravity, which reduces metacentric height).

The only way to make a trawler have a high LPS value is to lower its center
of gravity--either add a LOT more ballast, or more likely reduce the big
comfortable saloon/pilothouse/flybridge area. If you look at Dashew's boat
"Wind Horse" or the Diesel Duck designs, both of them have made this
tradeoff. The A/B ratio, which should also be specified by manufacturers, is
a rough measure of this. It's the ratio of area above the waterline to the
area below the waterline. The lower the A/B ratio, the lower the area of the
structure above the water. Notice that this is not a measure of the weight
above the water--just the area. On the Selene 53, the A/B ratio (again from
the web site) is 2.53.

So.....I hope that helps and not just "muddies" the water.

Mark

-----Original Message-----
From: passagemaking-under-power-bounces@lists.samurai.com
[mailto:passagemaking-under-power-bounces@lists.samurai.com] On Behalf Of
bob england
Sent: Tuesday, April 03, 2007 7:09 AM
To: Passagemaking Under Power List
Subject: Re: [PUP] Scelenes vs Nordhavns

Can either of these types of boats, and similar voyaging boats handle a
knockdown and recover. How about a barrell roll. I'm not being sarcastic, I
want to know the facts, and, I really like both of them, they just look
awesome !> Date: Sat, 31 Mar 2007 07:17:27 +0200> From: mygoleen@gmail.com>
To: passagemaking-under-power@lists.samurai.com> Subject: Re: [PUP] Scelenes
vs Nordhavns> > Hi Bob (and all),> > You wrote:"Nordhavn has done this
brilliantly in their marketing and> advertising campaigns."> > Yes, they
certainly do and I feel that after we purchase a boat, it is our>
responsibility too to keep her in good shape and visiting the 'engine room'>
often and not only when things goes wrong, is a MUST!> > You said:"One needs
to either be able to fix them, or do without"> > Absolutely! On Goleen we
keep
our engine room not only sparkling clean, if> possible, but with an eye on
everything at all times to spot signs of wear> and tear. OF COURSE, THINGS
CAN
GO WRONG NO MATTER, AND NOT ONLY ON THE> ENGINE ROOM!> > On passages, we
visit
the engine room very often and Chris measure> temperatures, search places
for
possible leaks, fuel levels, fuel filters> and so on.> I hardly even hear
music on board when we are on a passage because I like to> hear if the
engine
'sound' is the same or if it changed in any way, which is> one of the first
signs of trouble ahead, if it changes.> I do appreciate that it is difficult
for any of us, and even for the> 'engeneer's types' to know it all, but one
need to be prepared to take> action and do something on the spot and
sometimes, FAST.> > We had problems before that we didn't know how to fix it
immediately so, we> opened the manual and read' or made a phone call and
listened.> If one is prepared mentally, physically and emotionally for this
kind of> event to happen, it should be fine, and THAT is why I keep banging
on
the> key on this forum that talking about HOW we cope ( and not ONLY about
'WHAT> WE DO') in adversity is important too. In the end it will be our
mental> state that will save the technical issues (and ourselves) when 'push
comes> to shave', in MY opinion.> > Just to illustrate:> On Yachting World,
April edition, 'Run down at Night', pg 80/85, Clark Beek> wrote about his
experience of his 40ft ketch Condesa been run down by> a freighter:> > >
Pure
Panic paragraph:> "Let me state for the record that I am not proud of what
I
did. This was> one act of pure panic.> ...I did a freestyle sprint at a
speed only possible when that sort of> adrenalin is pumping through one's
veins, tumble in a crashing bow wave,> then sprinted again. Ian (his crew)
would have been right behind me,> following my stupid lead, but because of
Hilary (his other crew was stuck> inside the vessel*) he missed his chance
at
being the second human in> history to bodysurf a freighter's bow wave."*> >
And he goes on: " My most important piece of advice is this: plan to be an>
idiot. I always considered myself a pretty cool customer under fire, but>
when
life and vessel were on the line I found myself functioning at about 10> per
cent of mental and physical capability. It made me re-evaluate some of> my
emergency procedures omboard because they are too complicated for a> rattle
mind."> **> You see what I mean?> > All the best and keep learning,> >
Sonaia
Hermida> NH 5729> > > On 3/30/07, thataway4@cox.net thataway4@cox.net
wrote:> >> > My impression looking at 2 or 3 year old Nordhavn's vs the same
age Selene> > is that the Nordhavn ages bettter.> >> > There are some design
features including seating on the flying bridge,> > engine room access which
I
like better on the Nordhavn.> >> > Any new boat will have problems. I spent
over 3 months getting issues> > repaired on a new boat last year. Further
more, with time many systems on> > boats will either wear or fail. One needs
to either be able to fix them, or> > do without. If one looks at the
Nordhavn
40 around the world--there were a> > number of issues, if one studies all of
the reports from the boat and> > various people aboard.> >> > I also need to
clarify a word which may have caused some> > confusion: Scheme: " A
systematic
program for obtaining some objective" is> > Webster's first
defination--Nordhavn has done this brilliantly in their> > marketing and
advertising campaigns.> >> > Bob Austin> >
_______________________________________________> >> > Passagemaking Under
Power and PUP are trademarks of Water World> > Productions, formerly known
as
Trawler World Productions.> >> > To be removed from the PUP list send an
email
with the> > subject "unsubscribe" (no quotes) to the link below:> >> >
mailto:passagemaking-under-power-request@lists.samurai.com> >> >
Passagemaking-Under-Power Mailing List>
_______________________________________________> > Passagemaking Under Power
and PUP are trademarks of Water World Productions, formerly known as Trawler
World Productions.> > To be removed from the PUP list send an email with
the>
subject "unsubscribe" (no quotes) to the link below:> >
mailto:passagemaking-under-power-request@lists.samurai.com> >
Passagemaking-Under-Power Mailing List

i'm making a difference. Make every IM count for the cause of your choice.
Join Now.
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l
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Passagemaking Under Power and PUP are trademarks of Water World Productions,
formerly known as Trawler World Productions.

To be removed from the PUP list send an email with the
subject "unsubscribe" (no quotes) to the link below:

mailto:passagemaking-under-power-request@lists.samurai.com

Passagemaking-Under-Power Mailing List

Bob asked:  Can either of these types of boats, and similar voyaging boats
handle a
knockdown and recover?

I don't believe my 40 would survive a knock down (90 degree) roll and
"recover".  Perhaps I'm not giving the boat enough credit, but the forces
that would be at work on the superstructure, exhaust stack and mast,
windows, engine vents, contents of the interior of the boat and so forth are
scary to consider.  I guess the righting moments are there in the stability
data, but physically what would happen inside the boat is really the
concern.  Maybe someone can comment on the most extreme situations they have
encountered?

Scott Bulger, Alanui, N40II, Seattle WA

Passagemaking-Under-Power Mailing List

Recently the was a comment about positive stability angle, and a question
about the Nordhavn's.

The data for the Nordhavn 40 shows a positive stability to 145 degrees, I
don't have the data curve for the 46 or 62 but it is probably a little
higher.

Key to any boats stability is the integrity of the windows, the N-46 is
often equipped with 6 storm plates to add to the impact resistance over and
above the ~12mm glass with a 3/4" center bar.

Certainly any boater that is examining stability curves and large sea
performance will bolt down all significant interior flying objects because
at an angle of 145 degrees there will be a lot of things flying around.

Safe boating - good thinking
John Harris
N-4657

I do not know the statistics as to the stability angles of Nordhavns, or
Selenes, but will say that I am fairly certain that they are both in the top
1%, as far as safety in heavy seas, of all non-commercial power boats.

As to the issue of sail versus power, with respect to stability: I'm not
convinced that a sailboat is safer than my trawler. The ultimate issue is
safety, and my guess is that more mariners have been lost by being swept off
the deck of a sailboat, than have been lost through knock-down of
powerboats. Another thing to think about is that sailboats tend to seek the
wind whereas powerboats avoid it. I was just doing some research on best
routes to cross the Pacific and noticed a comment saying that the center of
the Pacific High should be avoided. This is certainly true if you are on a
sailboat, but as a power boater, I can tell you that a thousand miles of
flat windless water doesn't sound all that bad. My only point is that we
should try to separate "perceived safety" and "real safety". I could add to
this discussion that, from what I've personally observed, sailboats are
significantly more likely to be at sea, or in an anchorage, improperly
lighted. They are also much less likely to have modern navigation systems
such as AIS transmitters. Although statistics might imply that it can be
tougher to belly-up a sailboat, I suspect that the real stats, if they were
available, "might" show that fewer power boaters, than sailors, are lost per
mile of ocean passage.

On a semi-related topic:

I hope that this discussion segways into a discussion of heavy seas tactics.
I've bought all the books I can find on this subject, but 99% are oriented
towards sailboats, and I'm not sure the tactics are the same. I've
personally never set a drogue, or a sea anchor, and hope I never do. I have
no idea how to "heave to" in a powerboat. Thus far, I've successfully
avoided really snotty weather, but sooner or later I'm sure I'll get caught
by surprise.

Mike Maurice - as someone who runs the pacific coast regularly, is there any
particular advice you'd like to offer on this subject? The limit of my
knowledge is "don't get beam to the sea" and "it is usually smoother going
downwind than upwind". My only other rule of thumb is: "If the weather
router says not to go - don't go." Somehow, I suspect there is more to be
known on this subject....

-Ken Williams
Nordhavn68.com