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Go Back   SailNet Community > On Board > Boat Review and Purchase Forum > Sailboat Design and Construction > Multihull
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  #211  
Old 03-17-2014
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Re: How do you feel about catamarans?

Are you aware of such an instance of damage to the stern of a catamaran deploying a Jordan Series Drogue?

I am not saying that the concern is illegitimate, but the drogue acts to minimize the forces acting on the boat while a sea anchor tends to present shock loads. Do you agree with that part?

I remember some test video on the Jordan site or linked to by it, but I am not finding it. It shows the effect of a large breaking wave on the boat. The idea is to maintain some forward motion, but not allow the boat to surf down the wave and crash out of control. Instead, the boat continues forward with the drogue providing a retarding force increasing with the square of the speed of the boat. That allows the boat to be lifted up under the wave with the breaking wave impacting the boat as gently as possible, under the circumstances.

Here is another question. Are you aware of an unsuccessful deployment of a jordan series drogue on a catamaran? If so, I would like to read it. I remember reading that the concern about presenting the stern is common, but it never really ends up being an issue in practice.

As far as the swinging doors, what if they fit recessed into the sides of the companionway such that they did not catch or snag on passers by? I like the idea of being able to seal it up quickly. And, crew can quickly come and go minimizing the time that it is open.

I was speaking to a Jeanneau engineer at a boat show about the windows. I will see if I can get some data on their strength. Again, it is a valid concern, but let's see what the engineering data says.

Thanks.

Quote:
Originally Posted by JonEisberg View Post
Well, until a large breaking sea crashes thru those sliding glass doors, perhaps... :-) I just don't see how it's possible to make such a blanket statement, we'll just have to agree to disagree, as I see a whole lot of cats out there (monohulls, as well) with configurations aft that I wouldn't want to present to large breaking seas lying to a JSD...



Those about the only examples out there of cats using a JSD, and I wish they were a bit more specific about the particular types of boats, etc... Victor Shane's DROGUE DATA BASE, to the best of my knowledge, doesn't include a single such reference, the preferred tactic among multihullers seems to be a parachute sea anchor off the bow. I can't speak from much experience on this, having sailed on a large cat for only a period of about 10 days, but that tactic would be my first inclination if caught in heavy weather in a cat... So, I'll stick with Steve Dashew's final conclusion re the JSD:

"On the other hand, many cruising catamarans, with their aft sliding doors - would be extremely vulnerable to a boarding sea from the stern - as would any modern racing or cruising yacht with an open transom."




We'll have to agree to disagree once again, I have come to absolutely DETEST swinging companionway doors on virtually every boat I have ever run that features them... They are invariably very poorly executed, are forever snagging foul weather gear and such, and in many cases present a real danger to crew, with a great potential for causing a very serious injury...

Absolutely boggles the mind, that a major popular builder goes with something like this, what the hell are they thinking?

Obviously, they're thinking that their primary 'market' desires boats that are more like houses, than boats... Or, 'sailboats' that are more like powerboats... :-)





Never ceases to amaze, some of the stuff one sees on today's floating RVs. These doors were mounted on a continuous hinge, so were not removable... A grisly accident, just waiting to happen...







Uhhh, think again... :-) No doubt that may be the case on a boat like an Oyster, perhaps, but I think sticking these large windows in the topsides of many production boats is one of the worst trends in boatbuilding today...

A year ago, I witnessed a boat pinned against the outside of the Megadock in Charleston in a blow, her fenders literally squashed flat by the pressure to the extent that the hull was coming into contact with the dock in the vicinity of one of the picture windows (Astonishingly, placed at the point of the boat's maximum beam amidships)

The inward deflection of the hull was clearly visible, and the 'cracking/splintering' noises being produced were rather disconcerting, to say the least. The fact that this was all taking place in very close proximity to the boat's chainplates would have to give any serious sailor pause regarding the monumental stupidity of cutting such holes in the topsides of today's ordinary production boats...
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Re: How do you feel about catamarans?

I find this discussion very interesting and would like to point out the following.
In monohulls typically with a knock down the port lights on the up wind side (not the one immersed) blow out. It's the deformation of the house and internal forces that cause this. One would expect the large open houses would be exposed to similar forces by large boarding seas.
The forces generated by boarding seas can be extreme. I know of empty davits being severely bent by pooping and have had moderate boarding seas destroy well constructed dodgers. I have a JSD and hope to never use it in anger. I do not expect it to prevent damage to the aft sections of my and any other boat mono or multi if those regions are not constructed to allow for such a occurrence. I think with all due respect jzk is being over optimistic. Yes current port light glass is much stronger then in the past. Yes cored houses are much stiffer. Still, such large houses as seen on multi's will have much greater forces applied. They do not have extensive internal bulk heads spanning the large interior open spaces. Without thoughtful design I believe they are potentially subject to sufficient damage as to compromise watertight integrity allowing risk of down flooding. Returning to original question "What current multi's are safe offshore boats?"
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  #213  
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Re: How do you feel about catamarans?

It is not impossible that you could be correct and the aft exposure could be an issue.

However, again, the amazing thing about the JSD is the way that it minimizes such impact by keeping the boat going forward and allowing the wave to lift up the boat.

In other words, if you are going to be hit by a 100 mph baseball, would you rather be traveling 30mph away from it, or 30 mph towards it?

I remember seeing some great test video in a tank or something, or maybe it was just a graphical representation that demonstrated this concept.

Do you remember that catamaran that was abandoned on its maiden voyage? They took a wave from the front that stopped it in its tracks and even pushed it backwards. If I am recalling correctly, this bent the rudders and loosened the front window.

I would much rather take the punch from behind while I am moving forward away from it than be travelling into the punch or not travelling at all.

Also, keep in mind that the bigger the wave, the faster I am going to be going away from it. And, the faster I go, the more force the JSD will be applying to slow me. Seems like the optimum balance.

I also remember reading that if one is going to have a problem with a JSD, it will be from it being too strong and not letting the boat have suitable forward speed.

Anyway, does anyone know of stern issues actually caused by breaking waves with a JSD deployed?

Quote:
Originally Posted by outbound View Post
I find this discussion very interesting and would like to point out the following.
In monohulls typically with a knock down the port lights on the up wind side (not the one immersed) blow out. It's the deformation of the house and internal forces that cause this. One would expect the large open houses would be exposed to similar forces by large boarding seas.
The forces generated by boarding seas can be extreme. I know of empty davits being severely bent by pooping and have had moderate boarding seas destroy well constructed dodgers. I have a JSD and hope to never use it in anger. I do not expect it to prevent damage to the aft sections of my and any other boat mono or multi if those regions are not constructed to allow for such a occurrence. I think with all due respect jzk is being over optimistic. Yes current port light glass is much stronger then in the past. Yes cored houses are much stiffer. Still, such large houses as seen on multi's will have much greater forces applied. They do not have extensive internal bulk heads spanning the large interior open spaces. Without thoughtful design I believe they are potentially subject to sufficient damage as to compromise watertight integrity allowing risk of down flooding. Returning to original question "What current multi's are safe offshore boats?"
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Re: How do you feel about catamarans?

Had a fair amount of back and forth with the gentleman from England who builds the JSDs calculating exactly how many cones my vessel would require. He constructed a second series to attach to the first also calculated minimum weight to stick on the end. That said the device does greatly increase chance for survival and does allow you to lash the helm amidships and go below with the boat passively enduring the storm. This also increases odds you and your crew will survive. However, there are potential boarding seas and then there are breaking seas. The breaking seas I've encountered are not always predictable. Nor are they always coming the same as the rest of the wave train. Nor have they come up to the boat at the same speed as they prevailing waves -in fact usually they are travelling faster as they break. Even when surfing have been pooped. Admittedly mildly so as this occurred in a gale not a storm. Have had a prior boat completely submersed from seas boarding while hove to in a storm but nothing blew out ( other than the Sargent strips on my and my co owners pants until it was over(grin))However, although I agree with everything you've said I think the JSD does not prevent pooping by breaking seas and boats should be designed to survive such occurrences. As Jon said this is equally true for one hull or more. I just wanted to point out due to nature of design with much wider houses this is potentially more of an issue with multihull vessels.
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  #215  
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Re: How do you feel about catamarans?

Yeeha!

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Re: How do you feel about catamarans?

Wow ?what is it? I thought cruising cats were never suppose to fly a hull but it sure looks like fun.
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Re: How do you feel about catamarans?

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Yeeha!

And yet you don't like leaning? Standard cat hypocrisy.
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Re: How do you feel about catamarans?

Look at the wave angle, she's going to weather. That is the Gunboat 'Elvis' doing her thing at the Heineken regatta just past
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Re: How do you feel about catamarans?

Quote:
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Wow ?what is it? I thought cruising cats were never suppose to fly a hull but it sure looks like fun.
Not quite sure if I would call her a cruiser, but if so, she is a special type of cruiser!
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Re: How do you feel about catamarans?

really? y'all don't know about the Gunboat catamarans? Peter Johnstone, as in the same family who builds the J-boat monohulls?
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