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Old 27-03-2008, 14:49   #1
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The Ketch-Rigged Cat

I have a passion for design. This makes me spend a lot of time looking at things and tweaking them, mentally if nothing else. So I was wondering, why we donít see many ketch rigged Cats? I know there has been a tendency towards sloops for several years, but I still like to wonder.

Anyway, here is a few links which I throw out as an intellectual bagatelle. Most of these boats and therefore the designs are from the early years of modern catamaran design so you arenít going to see the next gunboat here.


.... in fact, some are pretty ugly.
Note the correlation between year and size, not that you can draw much of one with only four data points


And while we are at it:
28í 1978 (it says itís a ketch but it looks like a yawl)
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Old 27-03-2008, 15:06   #2
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The 62ft. Tahuna was for sale In St. Maarten when I bought Imagine in 2002. I believe they were asking 1million, but that may have been hearsay. I next saw the boat in Ft. Pierce on the hard in Dec.
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Old 27-03-2008, 15:06   #3
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of 04 going through a major refit?
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Old 27-03-2008, 15:27   #4
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The Chris White 63 is an interesting design. It is a rocketship, yet the ketch rig allows a mast height of less than 65' for ICW bridges.

Where to hang out though?
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Old 27-03-2008, 19:51   #5
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The 52 footer in your list was behind the house next door to me up until a few weeks ago. It may be the ugliest boat I've ever seen. The crossbeam on the bow is a wood 2X8 that may have come from Home Depot. There are so many bad things going on with that boat it's impossible to list them all.
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Old 28-03-2008, 08:21   #6
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Abaco,

I bet she was sweet sailing in her day though........
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Old 28-03-2008, 11:59   #7
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I'm not so sure. The rudders are controlled by some kind of underwater lever arm that runs between the hulls to the central steering statioin. Most Rube Goldburg thing I have ever seen. When is the last time you saw wire halyards? She's got them.
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Old 28-03-2008, 13:13   #8
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Quote:
Originally Posted by Maren View Post
I have a passion for design. This makes me spend a lot of time looking at things and tweaking them, mentally if nothing else. So I was wondering, why we donít see many ketch rigged Cats? I know there has been a tendency towards sloops for several years, but I still like to wonder.
I think it is mainly because of the advent of reliable and cheap furling systems, and the increased use of bow sprits and asymmetric kites. These are alot easier and simpler than a complete mast and boom, that adds weight at the end of the boat, and ropes that get caught in the davits/dinghy.

I think we will be seeing more unstayed rigs in the future, be it ballestrons or "normal" to further ease sail handling. Maybe even some bi-rigs but only in niche market segments, as the price will be higher than a standard aluminium extrusion.

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Old 30-03-2008, 06:57   #9
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{Sloop/Bermuda/Marconi: a single mast with a main sail on a boom and jib; both triangular-ish shaped.}

Well, I agree with your conclusion about the imminent demise of standing rigging. And I agree that dependable and affordable roller furling systems make their use more common. But that only explains the use of the furling system.

Or carrying it to the next level, why no roller furling clippers? Why donít we have the roller fuller at either end of the boom but instead either a roller system concealed within the mast or boom. Heck, why not a mast with a jib at one end and Ö jib-like main sail? In other words, the ease of use and affordability a roller furling for the jib doesnít explain the ubiquity of the other. And if were only ease, why not the Aerorig or Balanced Rig?

Why the increasing homogeny of sail plans?

I think itís due to the influence of the racing circuit, just in the same way we are seeing square headed mail sails and the use of carbon fiber, Spectra and Kevlar.

You know would know this? C.A. Marchaj.

All this ended up getting me to do a trail of web research that I canít recreate but I think this page sort of sums what I was working through.

Of course I would be interested in everyoneís comments, though it might be better to address them here.
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Old 31-05-2008, 06:25   #10
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Ketch Rig references

I believe you will find I have a real appreciation of the ketch rig myself. Have a look at a few of these postings I've made:

Ketch Rigged Catamaran by Chris White
Boat Design Forums - View Single Post - Aftmast rigs???

Brion Toss, on 'Mizzens'
Boat Design Forums - View Single Post - Aftmast rigs???

Aft-mast Origination & Justification
Boat Design Forums - View Single Post - Aftmast rigs???
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Old 31-05-2008, 11:43   #11
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Brian, interesting you bringing up Chris White's Concept 63. That boat is what I've been using so far as the base design for my next boat. I don't need/want as much "house" so doodling with some changes which should reduce weight - also have been thinking your aft-mast rig may have some advantages over the ketch rig.
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Old 31-05-2008, 15:15   #12
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Brian Eiland? Sweet! I was just going to email you.

Quote:
Originally Posted by beiland View Post
I believe you will find I have a real appreciation of the ketch rig myself. Have a look at a few of these postings I've made...
Brian,

You, know I instantly recognized your name and am really glad you posted. I was going to email you today before work ended up consuming my day. I really do like the ketch rig, but as you are the number one guy for the aft-mast rig, I would prefer to concentrate on that.

In short Iíve read most or all of the posts you wrote about the aft mast rig on boatdesign.net and one of the links I posted above is to an article of yours. However of all the threads I've found, this one along with the threads and sites it links to is, I think, a great primer on the subject.

But, letís get past the primer.

I noticed you have several times kind of skirted the issue of loads. I certainly can understand there are a lot of variables at work and that you many be loathe to address this in detail as the whole rig is relatively new and pretty much anything you put up will be set upon by everyone from recognized naval architects to the newest sailor with almost six whole hours of time on sunfish. That skepticism is fair though as no one wants to potentially risk their life on an untested piece of gear.

... Well, except for that guy Barefoot and a few others.

As you pointed out though, he didnít follow your design exactly and instead rather poorly ripped off of some of your material. But you also pointed out he did at least try the rig while others have stayed merely sat on the sidelines.

And no one really knows about that backstay either. It could have been poorly made, was a piece of salvage, used bad underlying assumptions or came down to misapplication.

The point is it's failure doesn't really tell us much. Unfortunately, the success it had prior to failure doesn't say too much either as he didn't write much about its performance only the comments it drew on its appearance.

I think general acceptance of something this new tends to go like this: The engineers trust the numbers, the daring try it out, and over time acceptance is gained from experience of those that went first. But the numbers are the lynch pin in my opinion. So I keep coming back to the question, but from three different approaches:

The Godfather Ė Have you floated this past C.A. Marchaj yet? I think he would lend a great deal of credence to the work.

Loads - The occasionally voiced concern of those that have read everything they can find on aft-masts is the crystallized thread of a Norseman backstay and the later switch to a conventional sloop rig from by Barefoot who, as pointed out above, didnít follow what you were saying in the first place. By extension, the concern is that the rigging might be sized to take the loads but the hulls couldnít or would at least need some reinforcement. And yet, this is contrary to your position that the rig would have less stress because of a lower Center of Effort. I suppose the answer is running a finite element analysis of the whole deal but I am not a Naval Architect. So Iím asking you, the chief proponent Ė Brian, what are the loads involved and have they been rigorously calculated or has this been done with an applied engineering approach?

Application & feedback Ė Do you have concrete feedback for the few folks that have implemented the aft-mast? I remember you mentioning several have contacted you on your site but most seem more out of interest rather than results of application. The feedback is, I think, critical to acceptance and would lend itself to a comparative polar diagram of the velocity at various points of sail.

Well, thatís more than enough for now. I really look forward to your input.



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Old 03-06-2008, 12:59   #13
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...... Well, except for that guy Barefoot and a few others.

As you pointed out though, he didnít follow your design exactly and instead rather poorly ripped off of some of your material. But you also pointed out he did at least try the rig while others have stayed merely sat on the sidelines.

And no one really knows about that backstay either. It could have been poorly made, was a piece of salvage, used bad underlying assumptions or came down to misapplication.

The point is it's failure doesn't really tell us much. Unfortunately, the success it had prior to failure doesn't say too much either as he didn't write much about its performance only the comments it drew on its appearance.
Hello Maren,
I'm going to have to answer your posting in several stages due a time constraint I have at the moment. So here is one portion having to do with the tri named Windwalker. I had previously looked back thru his log postings and made these following excerpts from them:

Öexcerpts from log of aftmast trimaran Windwalker
Sat, May 14:
then set sails slogging to windward close hauled heading 045į making 3-5 kts. I experimented with various sail settings, depowering the main and genny to 1/3, and finally, at about 0915, for the first time setting the three foresails together, set the jib at 1/3 also. It all balances well, all three sails are pulling nicely about 35į off the wind. Held heading all day to get a better tack to Bermuda. This is the 5th day of easterly headwinds, right on the nose and no end in sight.

Tues, May 17:
I have a lot to learn about tweaking this aft mast rig to get best performance. The helm is well balanced, nearly neutral, holding wind course unattended for as long as 24 hours. It sails well hard on the wind in light air, but as yet I HAVEN'T had an opportunity to sail it off the wind or in stiff blows.

Fri, May 20:
0600, wind E - 4-6 kts, seas 3 ft, mostly clear, high 60s. Wind veered dead E right on my nose. On stbd tack heading 045į making 5 kts northing. Swell making for a rough ride. Motored for 1/2 hour getting sails set and on heading after being hove to. Big ketch on port tack crossed my bow at 0700, distant 1/2 nm. I went on a port tack, set the heading, went below to fix another cup of coffee when WHAM ------
DisasterÖ0800ÖDismasted Norseman backstay fitting failed, crystallized in the threads. 116 miles from Bermuda - vicinity of 32į 05'N, 67į 16'W - drifting and securing what I can. All wreckage, mast and sails on board and secured by noon

Mon, May 13:
After that I will spend a few days arguing with myself about how to go about the salvage and rebuild. Most obvious right now is to re-rig as a conventional cutter, as I have most all of what is needed in hand or can be modified.

Wed, May 25:
After consideration of damages and what I have left to work with, the only option apparent is to re-rig as a conventional cutter, recutting the sails to suit. I may be able to begin next week after I make arrangements to get the mast off the boat and on land.


So it appears as though his reasoning for changing from his original aftmast configuration over to a conventional configuration was based on the materials he was left with following the incident and his insufficient funds. He never really had negative comments about the rig, in fact most were praise. And both regrettable and inexplicable, he never made any more comments about rigging subjects at all, positive or negative?? I never understood this guy.
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Old 03-06-2008, 13:08   #14
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Hi there Brian,

Very excited to hear that someone has finally decided to put your design on the water!



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Old 03-06-2008, 13:40   #15
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Quote:
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So it appears as though his reasoning for changing from his original aftmast configuration over to a conventional configuration was based on the materials he was left with following the incident and his insufficient funds. He never really had negative comments about the rig, in fact most were praise. And both regrettable and inexplicable, he never made any more comments about rigging subjects at all, positive or negative?? I never understood this guy.
I can't say I really understand him either, which is why I wrote him … but he hasn’t answered. Considering he is something like 75 or so, I can't really say I blame him. He probably has other things he wants to do with his time left on the world. Sill, I wished he had been able to shed a bit more light on the topic. Three entries for that many miles isn't very much.

As for materials on hand, that really baffled me. With the exception of the mast and the fittings (in addition to anything else he might needed to have replaced) he had all the materials needed for another aft-mast rig with no heroics needed to move the rest of the standing rigging, re-cut the sail and so on.

My surmise is he thought it was the threads, but he felt like the boy who had been thrown off the horse. Only he didn't get back on that same horse.

Looking forward to your other points ...
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