catamarans boats with bad sea

[gandalff]

hello.
I am new in this forum.
I want to know as the power catamarans of about 20 to 30 meters behave with bad weather.

I listen that the boats power catamarans do not sail very well with bad weather

he is certain that. that so it is the comfort of the catamarans for the passengers?

somebody knows a comparative study on the catamarans?

my Ingles language is not very good. I do not dominate it :rolleyes: ;)

[mackid068]

I was on a 20 ft' cat during a storm (uncovered boat...yeah....) and it was a comfortable ride despite getting wet. I'd think that such a large boat 60-90 ft would have a REALLY nice ride, even in terrible weather (stability is increased with a cat)

[gandalff]

thanks for your commentary.
I am very confused, because I listens that the catamarans with bad weather sail very badly and are very incomodos for the crew but also listens that they are very stable, I am very confused.
in catamarans ferry of fast speed says that they are little stable and they do not have comfort for the crew and passengers with bad weather

[FAST FRED]

SIZE matters , there is quite a difference between a stripped out racer and a big cruising design.

The big thing is the multihulls, cat or try are ON the water ,
as opposed to IN the water on the typical displacement boat.

A really fast multy will ride very hard like any other high speed boat , a slow cruising multi will have a more flat ride than a monohull, but weather being lifted by the surge , or rolled is more comfortable is up to you.

In a very rolly anchorage the multis are far superior to the IN the water displacement boats , as lifting is easier on the tummy than rolling.

FAST FRED

[brian eiland]

I am very confused, because I listens that the catamarans with bad weather sail very badly and are very incomodos for the crew but also listens that they are very stable, I am very confused. in catamarans ferry of fast speed says that they are little stable and they do not have comfort for the crew and passengers with bad weather

...a short excerpt from some literature I prepared for the Miami show this year addressing the motorsailer catamaran concept.....
"The sea-kindliness of multihull craft is being rediscovered every day. Continual experiences with whale watching boats, fast ferries, pleasure, commercial, and military applications are all proving the validity of the multihull form. What many people forget about a good ride in a heavy sea is that it is very much a function of weight in addition to hull shape. More weight, more robust, more form resistance it offers to moving thru the ocean, the more the sea acts to resist the vessel's progress, and thus the more uncomfortable ride, and we must slow down. A big headsea is a particular challenge. Heavy boats carry their momentum into each trough and crest in a battle with the sea, while lighter weight vessels with slender hulls slice through with less battering. Per a sign at the Naval academy, "you can out-think the ocean, but you can’t out-slug the ocean." Modern materials allow for lighter boats, and we must properly distribute the vessel's weight throughout long slender hulls. Following seas tend to pick up broad sterns and slew a vessel off to either side....broach. The catamaran hull does not require these broad sterns.

Storm survivability should be considered at the design stage for any vessel making offshore passages. Loss of power (clogged cooling or fuel filters, restricted air supply, water ingress, etc) often occurs at the most inopportune time (during a storm), and this can put the solely powered vessel at peril in short order. A vessel with a modest sailing rig could save your life, and that of vessel itself. Add a proper sea anchor installation, and I would challenge a hurricane. The catamaran planform was rated 'best in survivability' in huge breaking wave tests* carried out by Lock Crowther at the prestigious Univ of Southampton.

**Note: reference source, Lock Crowther Designs
"This work (tank testing at Southampton Univ) has indicated that the well designed catamaran is remarkably safe in breaking waves up to considerable height, even when beam on, we were unable to capsize a power catamaran yacht in the largest wave which could be generated. This corresponded to a 52' wave for a catamaran of 40' beam. Scaling this down to a typical 24' beam cruising cat means she should be O.K. in a 31' breaking beam sea. An equivalent size mono-hull power boat was easily capsized by a 25' breaking sea, and in tests with conventional yachts after the Fastnet disaster, it was found that a 40' mono-hull yacht could capsized in a 12' breaking sea"
_________________________________________
The questions of comfort of passengers and crew on hi-speed ferry service aboard these new generation multihulls has been studied quite a bit. I don't have many of the reference sites to take you to, but with some research on the web using Google, I'm sure you can find quite a number. In general the 'quicker motion' of the lighter weight multihull will affect some passengers more than others, and this is usually confined to those areas of the vessel that would be subject to those higher acceleration forces such as in the bow areas...but then these areas are generally problem areas for most persons not having much time on the water.

gandalff, Don't forget to utilize the 'search function tool' at the top of this forum...might bring up some interesting other discussions for you. And you might have those 'associates' of yours that dismiss the catamaran hull form have a look at this seaworthy trawler photo (http://www.boatdesign.net/forums/showpost.php?p=40251&postcount=17). BTW, there is a brand new power catamaran forum (http://lists.samurai.com/mailman/listinfo/power-catamaran) starting up just today

[mackid068]

Always trust Fast Fred and people with a similar amount of posts (especially if they have sound logic...unlike Mighetto, who is odd, but ok.)

[kach22i]

...Add a proper sea anchor installation, and I would challenge a hurricane.
I don't want to steal the thread, but I am not familiar with "Sea Anchors".

Also I'm reading all with the mind set of how it may apply to SES; hovercraft and solid sidewall surface effect ships....................lightness, depth of hull structure, seems to be very focused on the topic (which is good), but from what little I know can not be directly compared or applied to something just barely in contact with the normal sea surface.

Are "Sea Anchors" something all sea going lightweight craft should be traveling with?

If anyone is interested in the SES/Hovercraft topic, please take it here:
http://boatdesign.net/forums/showthread.php?t=6752

[mackid068]

Google search...............

[kach22i]

Sure, I can do a google search, just thought you might enjoy playing the expert for a newbie. :)

Kind of what I thought it would be, did not think however that it would look so much like a classic parachute. Then again I'm going off the first link that came up.

http://www.seaanchor.com/seaanchor.htm
MULTIHULLS
U.S. Sailing has recognized the value of a true Sea Anchor aboard multihulls ... in Appendix VII of ‘RECOMMENDATIONS FOR OFFSHORE SAILING." One multihull builder has stated that the introduction of large diameter parachute type Sea Anchors has made it safer for muiatihulls to cruise blue water.
http://www.seaanchor.com/assets/photos/seaanchor.jpg

[FAST FRED]

A recent discussion by NASA showed from radar maping that large waves over 82 FT!!!! are far more common than previously thought.

Their numbers in a 10 day period world wide were astounding !!

To transit an ocean in any catimiran either the vessel should be self righting , or a damn nice raft and loads of com. gear should be at least duplicated.

Cats for COSTAL has been the by word since the 60;s , although folks have cruised the word with them , frequently sucessfully , the risk is REAL of seeing the world from an overturned vessel.

For the Mud Run , (oops "Great Loop" ) they would be grand if someone needed to go a few mph faster than a monohull displacement boat , in deep water the waves can get LARGE!

FAST FRED

[yipster]

joshua slocum used a sea anchor to keep the spray pointed into the storm. after reading he had no problem riding out any storm that way i made some ropes that hook into the achor chain and modified big transom wide bench i can trow overboard as a make do sea anchor.

[yipster]

ah wait guy's, get the real sea anchor parachute!
although i made the bench sinkable with the anchor using fenders as floats, chances are in a real storm you get the whole couch and anchor flying back :eek:

[brian eiland]

To transit an ocean in any catimiran either the vessel should be self righting , or a damn nice raft and loads of com. gear should be at least duplicated.

Cats for COSTAL has been the by word since the 60;s , although folks have cruised the word with them , frequently sucessfully , the risk is REAL of seeing the world from an overturned vessel.

... in deep water the waves can get LARGE! FAST FRED

Fred, can I suggest you look again at a portion of my posting:
"The catamaran planform was rated 'best in survivability' in huge breaking wave tests* carried out by Lock Crowther at the prestigious Univ of Southampton.

**Note: reference source, Lock Crowther Designs
"This work (tank testing at Southampton Univ) has indicated that the well designed catamaran is remarkably safe in breaking waves up to considerable height, even when beam on, we were unable to capsize a power catamaran yacht in the largest wave which could be generated. This corresponded to a 52' wave for a catamaran of 40' beam. Scaling this down to a typical 24' beam cruising cat means she should be O.K. in a 31' breaking beam sea. An equivalent size mono-hull power boat was easily capsized by a 25' breaking sea, and in tests with conventional yachts after the Fastnet disaster, it was found that a 40' mono-hull yacht could capsized in a 12' breaking sea"

Then I might ask how many power vessels are self-righting? I think you might be surprised at how many of these vessels would be just as happy upside down as right side up. So does that mean we should confine these power vessel to coastal cruising and no ocean crossings?

[FAST FRED]

"Scaling this down to a typical 24' beam cruising cat means she should be O.K. in a 31' breaking beam sea. An equivalent size mono-hull power boat was easily capsized by a 25' breaking sea, and in tests with conventional yachts after the Fastnet disaster, it was found that a 40' mono-hull yacht could capsized in a 12' breaking sea"


That 24 ft wide " Cruiser" is going to have a GRAND time with an 82 ft (23M) wave.

To have a boat be self righting is not EZ but done by the USCG on a daily basis.And of course by almost every normal sail boat in the world.

Yes the deck penitrations must remain intact , but thats been done for 75 years of offshore yachting.

The Fastnet disaster was lightly built "racing" boats and many deaths came from folks going into the raft , only to have the boat keep on floating.

"40' mono-hull yacht could capsized in a 12' breaking sea"

SO ??? It would survive (perhaps with the mast intact , perhaps without) The Smeetons survived two rollovers , only lost some time building a new mast.


How many motor coastal cruisers can survive a capsize? ,

probably as many as can survive a fire below ,
with most Mfg "saving" 2c a pound with high burn cheapo resin ,
instead of what's normally used by the Navy or USCG for their own boats ,
or on any boat that can carry over 6 folks in charter service.

A cat in the OCEAN is simply waiting to meet the BIG wave,
might not happen in a lifetime , might happen today!

FAST FRED

[kach22i]

I know we are talking about sea worthyness of cat's.......but I found this interesting development in military cats.

http://www.defense-aerospace.com/cgi-bin/client/modele.pl?prod=47039&session=dae.10226982.1110406327.Qi90t8Oa9dUAACM9zBY&modele=jdc_1
"The patented SeaCoaster catamaran design features cavities in the bottom of each hull into which air is blown providing lift to the vessel, reducing resistance, and thus allowing higher speeds to be obtained. Designer-inventor Don Burg expects speeds of up to 56 knots."

[yipster]

http://www.seacoaster.com/Pleasurecraft/55.gif
how bout this SeaCoaster Pleasurecraft?
http://www.seacoaster.com/

i like that porthole design (not from an underwater explosion!) dont think the aircushions are very seaworthy tho

[kach22i]

Well if you consider this perhaps..............from one of their links:

http://www.seacoaster.com/Air-Assisted_Catamaran_Concepts/index.htm
Quote: Rough water stability was verified during tests for the Office of Naval Research. In those tests, the maximum g-forces measured during operation at 32 knots while running into 1-2 meter head seas were 0.3g's RMS. Data for a typical planing hull in similar operating conditions show acceleration forces of over 6-g's

[yipster]

dont belive everything the millitary wrap say's :rolleyes: 2 meter waves might feel like a flat tire...

they build six so i guess they know ther stuff. i was a bit turned of by a few too many claims on their site.
dont get me wrong, SES are fascinating and i'm sure within a given envellope these boats do really well.