I totally agree with the last paragraph on points
to consider, and disagree with other comments
reference the Manta and similar designs.  There
is no perfect solution, but in terms of how most
people use their boats 90% of the time, I think
the engine location and access of the Manta is
the best solution for boats of its size range.

The engine hatch design does not compromise the
structural integrity of the hulls at all, thats
what bulkheads are for. The corrosion noted at
the boat show was from a leaking stuffing box
that was not attended to, which could happen to
any engine installation. The Manta has water
tight bulkheads to separate the engine room from
the interior, there is no interior access as one
person intimated, in most other designs if a leak
were to develop from the shaft, it could
jeopardize the seaworthiness of the boat, not so
with the Manta design.

The access to the engines on all sides for
servicing is outstanding, engines can be pulled
in a matter of a couple of hours, and with the
engine hatch open, lighting is much better
and one can stand up, not crawl on hands and
knees. With the watertight bulkhead, fumes and
smoke are separated from the interior, and
immediate ventilation can be had by opening the
hatch.

We have owners that have cruised these boats from
Florida to Nova Scotia, Great Loop, Bahamas and
Caribbean, with 1000's of hours offshore
while accessing the engines in a variety of
conditions, and none of them would tell you they
ever felt the engine access would jeopardize the
boat,  however they will alll tell you how easy
and pleasurable engine access for service is.

Pat Reischmann
Manta Catamarans
http://www.mantacatamarans.com/

The debate rages on! Mr. Reischmann, your reply to the corrosion issue
sounds rather "Pat". The boat must have had quite a gusher judging from the
extent of the corrosion in both engine rooms, as I recall.
While I appreciate the Manta's fabulous access to the machinery,
particularly in light of the fact that most boats spend 99% of their lives
tied to a dock and 90% of their voyaging time is spent in desirable sea
conditions, when the ship ultimately hits the fan priorities become
different.
As an offshore cruiser, I cannot embrace the idea of standing on the swim
step without secure rails to grasp, waiting for the hatch to slowly open
while a cresting sea is raging around my distressed vessel. Once access is
gained to affect emergency repairs, the cavernous space is exposed to the
intrusive seas. If the stuffing box were the problem to be dealt with, then
the engine room is probably flooding and therefore ever nearer to the
waterline. The consequences, we may agree could be dire.
We can all appreciate the convenience of walk-in engine rooms, but centuries
of boat building evolution has led design away from boats open to swamping,
even if the exposure is at a time when emergency access is a nessecity.

                                 Regards, Bert Harrott

-------Original Message-------

From: Pat Reischmann
Date: 01/03/07 08:02:01
To: Power Catamaran List
Subject: [PCW] Engine-room access

I totally agree with the last paragraph on points
to consider, and disagree with other comments
reference the Manta and similar designs.  There
is no perfect solution, but in terms of how most
people use their boats 90% of the time, I think
the engine location and access of the Manta is
the best solution for boats of its size range.

The engine hatch design does not compromise the
structural integrity of the hulls at all, thats
what bulkheads are for. The corrosion noted at
the boat show was from a leaking stuffing box
that was not attended to, which could happen to
any engine installation. The Manta has water
tight bulkheads to separate the engine room from
the interior, there is no interior access as one
person intimated, in most other designs if a leak
were to develop from the shaft, it could
jeopardize the seaworthiness of the boat, not so
with the Manta design.

The access to the engines on all sides for
servicing is outstanding, engines can be pulled
in a matter of a couple of hours, and with the
engine hatch open, lighting is much better
and one can stand up, not crawl on hands and
knees. With the watertight bulkhead, fumes and
smoke are separated from the interior, and
immediate ventilation can be had by opening the
hatch.

We have owners that have cruised these boats from
Florida to Nova Scotia, Great Loop, Bahamas and
Caribbean, with 1000's of hours offshore
while accessing the engines in a variety of
conditions, and none of them would tell you they
ever felt the engine access would jeopardize the
boat,  however they will alll tell you how easy
and pleasurable engine access for service is.

Pat Reischmann
Manta Catamarans
http://www.mantacatamarans.com/

Power-Catamaran Mailing List

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I have been watching the debate on style versus function and now safety
aspects with great interest. Today I have decided to shoot my mouth off.

1. Style and function need not be mutually exclusive.  Wide side decks and
   good foredeck access are not inherently ugly, in fact to my eye a boat
   without sides decks looks boxier and uglier than one with wide side decks. I
   submit the Motorcat MC29 as a stylish boat with decently wide side decks for
   its size.  The culprit is not style, it is crowding too much interior into
   too little boat!

2. Engine room access. I think a below water engine room accessed from the
   cockpit (or worse yet the transom) is inherently dangerous. The danger can
   be somewhat reduced with a watertight bulkhead at the forward end of the
   engine compartment, but it is still inferior to access from the inside of a
   cabin. In the best of all possible worlds, a proper engine room with
   standing headroom and easy interior only access is best. Engine removal can
   be addressed with "soft" bolt in panels above the engine(s).  Engines below
   a pilothouse floor (Grand Banks etc.) are pretty safe and offer reasonable
   access in smaller boats.

I notice that the Carolina 35 is promoted as an "offshore" boat. Personally
I would never apply that description to a boat that lacks an enclosed,
bulkheaded cabin.

With regard to twin engines, I have limited experience with such vessels,
yet I have twice experienced losing both engines. Once was hitting a log,
which broke a shaft coupling, allowing the shaft to slide aft and hit the
rudder, jamming it. The other engine still worked, but with no steering it
was useless. The other case was a brand new Chris-Craft with twin V8s. Both
engines suddenly stopped in the middle of the Strait of Georgia on the
delivery trip. This turned out to be a wiring fault, which I managed to jury
rig and get operating again. This was a long time ago, and I foolishly had
neither radio nor tools on board (BAD!!).

In my opinion a single engine boat is as safe as twins, proper maintenance
and good filters being more likely when you only have one engine to rely on.
This is moot on most catamarans as the layout makes twins a given. Best of
all is a boat with sails. The engine and sails being completely independent
of each other are not too likely to both fail at the same time. I know a
number of people who use their sailboats as economical trawlers, seldom
raising the sails, but still, they are available when you need them.

If there is any vessel which lends itself to being designed as a "true
motorsailer" it is a catamaran. I envisage a fully powered (15-20 knot)
vessel with auxiliary sails which could extend range and provide "get home"
capability. All I need is a client...

Kind Regards,
Grahame Shannon
Avia Design Group Inc.

-----Original Message-----
From: Bert/Noelle Harrott [mailto:harrott@cox.net]
Sent: January 3, 2007 2:34 PM
To: Power Catamaran List
Subject: Re: [PCW] Engine-room access

The debate rages on! Mr. Reischmann, your reply to the corrosion issue
sounds rather "Pat". The boat must have had quite a gusher judging from the
extent of the corrosion in both engine rooms, as I recall.
While I appreciate the Manta's fabulous access to the machinery,
particularly in light of the fact that most boats spend 99% of their lives
tied to a dock and 90% of their voyaging time is spent in desirable sea
conditions, when the ship ultimately hits the fan priorities become
different.
As an offshore cruiser, I cannot embrace the idea of standing on the swim
step without secure rails to grasp, waiting for the hatch to slowly open
while a cresting sea is raging around my distressed vessel. Once access is
gained to affect emergency repairs, the cavernous space is exposed to the
intrusive seas. If the stuffing box were the problem to be dealt with, then
the engine room is probably flooding and therefore ever nearer to the
waterline. The consequences, we may agree could be dire.
We can all appreciate the convenience of walk-in engine rooms, but centuries
of boat building evolution has led design away from boats open to swamping,
even if the exposure is at a time when emergency access is a nessecity.

                                 Regards, Bert Harrott

-------Original Message-------

From: Pat Reischmann
Date: 01/03/07 08:02:01
To: Power Catamaran List
Subject: [PCW] Engine-room access

I totally agree with the last paragraph on points to consider, and disagree
with other comments reference the Manta and similar designs.  There is no
perfect solution, but in terms of how most people use their boats 90% of the
time, I think the engine location and access of the Manta is the best
solution for boats of its size range.

The engine hatch design does not compromise the structural integrity of the
hulls at all, thats what bulkheads are for. The corrosion noted at the boat
show was from a leaking stuffing box that was not attended to, which could
happen to any engine installation. The Manta has water tight bulkheads to
separate the engine room from the interior, there is no interior access as
one person intimated, in most other designs if a leak were to develop from
the shaft, it could jeopardize the seaworthiness of the boat, not so with
the Manta design.

The access to the engines on all sides for servicing is outstanding, engines
can be pulled in a matter of a couple of hours, and with the engine hatch
open, lighting is much better and one can stand up, not crawl on hands and
knees. With the watertight bulkhead, fumes and smoke are separated from the
interior, and immediate ventilation can be had by opening the hatch.

We have owners that have cruised these boats from Florida to Nova Scotia,
Great Loop, Bahamas and Caribbean, with 1000's of hours offshore while
accessing the engines in a variety of conditions, and none of them would
tell you they ever felt the engine access would jeopardize the boat,
however they will alll tell you how easy and pleasurable engine access for
service is.

Pat Reischmann
Manta Catamarans
http://www.mantacatamarans.com/

Power-Catamaran Mailing List

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Power-Catamaran Mailing List

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I must say that I agree with most of what Grahame Shannon is saying. Until
relatively recently most of my power boat designs were for amateur
construction, often in timber. This predicated easy building and this meant
largely flat panels and the constraints this put on the styling.This is less
true now with the use of surface modelling design tools and 5 axis milling
machines. There is certainly now no excuse for the series production boat
not to have any type styling that the client might want. It is, of course,
easier to achieve more "swoopy" styling on the larger vessels [see Pacific
Harmony on our web site] but as grahame has said the "boxiness" is usually a
function of trying to fit too much accommodation into too short a boat. This
is usually at the behest of the customers who see a longer boat as more
expensive which with the catamaran configuration is not necessarily so.

I very much agree that the catamaran lends itself to being designed as a
"true motor sailer". In fact I wrote a chapter in Rod Gibbons book saying
just this. I think this was 1983 wasn't it Rod? I have since written a
number of articles extolling the motor sailer catamaran as "the best of all
possible worlds". I did, in fact, find a client for a motor sailer and in
1984 the Cordova was born. Twenty knots under power and has reportedly
sailed at 24 knots. it now has more than 100,000 nautical miles under its
keel and is still going strong as is my belief that it is indeed the best of
all possible worlds".

regards,

Malcolm Tennant.

Malcolm Tennant Multihull Design Ltd
PO Box 60513 Titirangi,
Waitakere 0642
NEW ZEALAND

ph +64 9 817 1988
fax +64 9 817 6080

e-mail malcolm@tennantdesign.co.nz
www.tennantdesign.co.nz
www.catdesigners.com

Dear Georgs,

Here is an article I wrote on motor sailers.This discusses the catamaran as
a motor sailer. I hope it isn't too long!

MOTOR SAILERS

IT HAS LONG BEEN MY CONTENTION THAT, AS A MOTOR SAILER, THE CATAMARAN HAS
NO EQUAL. IT PROVIDES THAT MOST ELUSIVE OF QUALITIES; THE BEST OF ALL
POSSIBLE WORLDS

I wrote this back in 1983 when we were first developing our motor sailers.
However in the intervening 22 years I have not discovered anything to make
me change my mind. What has changed in that time is that there have been
tremendous developments in construction methods, materials and sail handling
techniques. This can be seen in such developments as the in the boom roller
furling and captive sheet winches. These, coupled with the continuing
computerization of a lot of sailing functions, today make the motor sailer
catamaran concept more viable than it has ever been.

Of course, in the early days of the transition from sail to power, all
vessels were motor sailers. The engines of the time were neither powerful,
nor reliable enough, to propel a vessel unaided. The steam required by the
engines was produced by coal fired boilers and it was difficult to carry
enough coal for an extended voyage and still leave space for a significant
amount of cargo, or a reasonable number of passengers.

This gradually changed with the increasing efficiency of the steam engine.
And then the advent of firstly the naptha engines, and then petrol and
diesel further hastened these changes. All these engines gradually became
more efficient and light enough to be the sole means of propulsion. But for
many years sails were still kept for emergencies. Then there was also the
allure of getting something for nothing  ie: propulsive energy from the
wind. This attribute was, and still is; along with the not to be overlooked
romance of sail, one of the major attractions of the motor sailer.

The motor sailer usually consisted of a heavy displacement sailing hull with
large engines installed to give better performance under power. The heavier
engines and the need to be able to carry more fuel necessitated the heavier
displacement. But ultimately this approach is doomed by Froudes law. Neither
the speed/length ratio nor the displacement/length ratio was high enough and
the resulting vessels did not sail particularly well and neither was their
motoring performance very efficient either. So generally the motor sailer
has, of recent years, slipped from favour and sails are now found almost
exclusively on yachts, or occasionally, in a steadying role on long-range
trawler yachts. This is unfortunate because there have been some very good
pilot house cutters designed that have quite reasonable turns of speed
under power and more than adequate sailing ability. But they did, in the
main, need to be relatively long to be successful in both roles.

So are there other approaches to this compromised performance problem that
might give a more satisfactory solution and allow reasonable performance
under both power and sail?

One approach has been to dynamically alter the underwater shape of the
sailing hull to produce more power boat like hull characteristics when
motoring. The major problem with the displacement sailing hull is that the
longitudinal rocker combined with limited speed/length ratio causes the
stern of the boat to squat under power. This severely limits the speed that
can be achieved. However if the aft buttock lines can be straightened out to
approximate those of a planning power boat then planning, or at least semi
planning, may be possible. This would then mean that higher speeds under
power were potentially achievable. This approach was tried in the UK on a
moderately sized keelboat in the 70s. Retractable planning wedges being
fitted down aft. This was reportedly reasonably successful but this hull
modification approach does not appear to have been tried again until very
recently. Just launched at the end of last year from the Pendennis Ship yard
is MITseaAH a 156 luxury yacht with the naval architecture provided by
David Pedrick. That this is a very serious attempt at designing the ultimate
in contemporary monohull motor sailers is shown by some of its parameters.
It has the afore mentioned planning flaps down aft but it also has
retractable rudders and keel. The motive power is provided by two 3,500hp
engines driving 2 x 4  bladed 1.65m diam controllable pitch propellers that
also retract partially into tunnels when sailing. The result of all this is
that it will motor at 20 knots. Faster than is usual for a sailing vessel of
this type. However MITseaAH is a luxury vessel that is hugely complex and
enormously expensive. Given that the 20 knots achieved is only approx 4 to 5
knots more than the boat would have potentially been able to achieve in
normal displacement mode with that power, on that waterline length,
MITseaAH would not seem to be the answer to achieving the successful dual
role that most people would be able to afford.

In New Zealand there has recently been unveiled a design proposal for a
monohull motor sailer that has a retractable propeller putting 800hp into
the water to achieve 20 knots under power. A huge rig promises similar
speeds under sail. This design takes an ingenious approach to the squatting
problem. On this vessel twin hydraulically canting rudders act as elevators
to control the trim and keep the waterline level when under power. However
while this does prevent squatting while under way its does not change the
fundamental hydrodynamics of the displacement hull. It still has the curved
aft buttock lines of the typical heavy displacement sailing boat.

Is it possible then to approach this from the other direction? Rather than
trying to alter the shape of the sailing hull underway, can we fit sails
onto a power  boat hull? It is possible to fit sails to a traditional
displacement power boat hull? We have seen that this is exactly what was
done in the early days of power. Currently this is often done in the guise
of a steadying sail on long range cruising power boats. But again this
approach runs up against Froudes Law which limits the performance of a
displacement hull under power and sail. However the traditional way to go
fast in a power boat without it being very long is to make it planning. So
why not fit sails to a planning hull form? This has actually been done, and
very successfully, with the 26 McGregor Powersailer. This vessel sails
well, for a trailer sailer and planes with outboard power. However, this was
a small light displacement trailer sailer and it has proven to be much more
difficult to emulate this feat with higher displacement vessels. The
planning hull form has not, so far, proven to be particularly adaptable to
the sailing role. This would appear to be largely a function of the very
large immersed transom that is characteristic of this type of hull. At
sailing speeds they have very high hull resistance and not enough speed, or
power under sail, to get onto the plane. Consequently the sailing
performance leaves a lot to be desired.  So, is this approach of using a
powerboat hull to produce a credible motor sailer worth pursuing?

If we look at a completely different power boat hull form then I believe
that the answer would appear to be yes. A sailing catamaran relatively
easily achieves higher speeds, under both power and sail, with 30 knots not
being uncommon. However, although the sailing catamaran has a higher hull
speed than a monohull, it is still ultimately governed by Froudes Law and
squatting occurs at higher speeds under power. If squatting occurred with
the sailing catamarans at these sorts of speeds then it obviously was going
to be worse in the case of a power boat using the sailing catamaran hull
shape. What is more the power boat did not have the diagonal forward loading
from the rig that tended to counteract the squatting to some extent in the
sailing vessel. To get around the squatting associated with these higher
speeds on a displacement hull form a hull shape that was different to that
of the normal sailing catamaran was needed. We early reasoned that we could
minimize the squatting by careful shaping, and placement, of the aft
buoyancy. By sweeping the hull inwards at the stern to straighten the aft
buttock lines, rather than up to the surface in the traditional manner, we
created a fully immersed canoe stern hull with no exposed drive train
appendages such as shafts and struts. This also resulted in a clean water
flow to the propellers. This shape was then enhanced by then placing a flat
section of hull over the top of the fully immersed canoe stern. This did
result in an immersed transom but one of much smaller dimensions than that
found on a planning monohull so while the increase in drag was minimal,
while the effect on squatting was maximal. This approach to a high-speed
displacement catamaran hull proved to be very successful. So when we started
looking at motor sailers in 1983 we essentially took our powerboat hull form
and fitted a rig. There was some extra reinforcing needed to take the loads
exerted by the rig but there was very little else to do. We knew that this
hull form, in the sizes we were looking at, was capable of more than 30
knots under power [ The 17.5m loa Red Diamond II was clocked by NKK at 32
knots over the measured mile] with very little change in level trim at
speed. It was really only a question of how well would it sail. Stability
was not a problem because of the inherent high initial stability of the
catamaran configuration. Our low wave making CS hull form, which we had
developed earlier in 1983, had shown exceptional efficiency as a power boat
and the parallel aft buttock lines led us to expect that it would have
exceptional sailing qualities also. In practice this has proven to be true,
as this hull has turned out to be faster than the equivalent sailing
catamaran on a reach. Windward performance is not in the racing boat class
but is certainly better than that of most cruising catamarans and could be
further enhanced by fitting centerboards if one wished. Of course you could
always turn one, or more, of the engines on!

The first boat to prove the viability of this approach to the motor sailer
was Athenea one of our Cordova designs which has now covered more than
100,000 nautical miles in the open ocean. This 18m [60] by 8.7m [28 6]
cruising boat does 15 to 18 knots under power from 2 x 150hp and has sailed
at more than 20 knots on many occasions. The 16,400kg [36,155lb]
displacement encompasses an interior that would not be out of place in a
medium sized house. This house like impression is further enhanced by the
use of domestic appliances for the fridge, freeze, dishwasher, washing
machine, air conditioning and clothes drier etc The helm is totally enclosed
and the sailing functions can all be performed from there with the help of a
couple of electric winches. All this was achieved on a motor sailer
catamaran in 1983!

Because the catamaran usually has a twin-engine installation it leads to the
possibility of some interesting sail/motor combinations. It is possible to
set a target speed and use whichever combination of sails and engines
necessary to maintain that speed. The owner of Athena set a target speed
of 12 knots. Some 20 years later he had to admit defeat as in all that time
he had only managed to average 11.8 knots! The use of feathering propellers
minimizes drag when only using one engine or sails only. If very long
distances are contemplated then controllable pitch propellers are an option
that might be considered. It has been shown [on Wildwind IV] that running on
one engine with one propeller feathered and the pitch on the other optimized
can result in a 10 to 20% reduction in fuel use at the same speed. Of
course, this also halves the engine hours and allows maintenance to be
performed on a cold engine. It would also be possible to completely automate
the motor sailer systems and leave them entirely under computer control to
achieve maximum efficiency at whatever ratio of sail to power was the most
efficient at achieving the desired performance. However controllable pitch
propellers, which would be a necessary part of such an automated system, are
expensive and their use can only be justified if you are traveling very long
distances. [Wild Wind IV is currently approaching 30,000 nm and Athena more
than 100,000 nm]

This general approach of fitting sails to our power catamarans can be
applied to all the various styles of our power catamarans. Provided the
required extra reinforcing is built into the structure and it has sufficient
beam to give the required stability under sail, any of our long-range power
cats can be fitted with a rig and achieve very respectable performance under
sail. This also means that you can motor around quite happily without the
rig if you wish. Until such time as an exorbitant increase in the price of
fuel forces a radical rethink and the fitting of a mast and sails. You could
also of course have the latest in Eurostyling in a swept up catamaran
such as Pacific Harmony that would out perform MITseaAH under sail, or
power, and also offer much more interior space and comfort for considerably
less complexity and cost.

Malcolm Tennant Multihull Design Ltd
PO Box 60513 Titirangi,
Waitakere 0642
NEW ZEALAND

ph +64 9 817 1988
fax +64 9 817 6080

e-mail malcolm@tennantdesign.co.nz
www.tennantdesign.co.nz
www.catdesigners.com