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Old 14-09-2013, 18:32   #31
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Re: Are there latitude limits for cat sailing?

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He added Kevlar to the bows and sides, and reinforced the rudder shafts."
The first part is understandable, but how do you reinforce rudder shafts without changing their dimensions and requiring a complete redesign/refit of the steering?

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Old 14-09-2013, 18:39   #32
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The first part is understandable, but how do you reinforce rudder shafts without changing their dimensions and requiring a complete redesign/refit of the steering?

Mark
Maybe reinforce the outside dimensions of the shaft tube and leave the inside dimensions as they were.
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Old 14-09-2013, 18:49   #33
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Re: Are there latitude limits for cat sailing?

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Maybe reinforce the outside dimensions of the shaft tube and leave the inside dimensions as they were.
Do you mean that opposite? Changing the OD will be a problem, where the ID is less of one (although more difficult to do).

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Old 14-09-2013, 21:07   #34
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Do you mean that opposite? Changing the OD will be a problem, where the ID is less of one (although more difficult to do).

Mark
Maybe I worded it wrong. I wasn't thinking of beefing up the actual rudder shaft, but rather the tube that supports it.
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Old 15-09-2013, 03:13   #35
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Re: Are there latitude limits for cat sailing?

Another Cat near the ice photo, Seawind 1000 in Alaska
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Old 15-09-2013, 06:44   #36
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Re: Are there latitude limits for cat sailing?

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Originally Posted by colemj View Post
The first part is understandable, but how do you reinforce rudder shafts without changing their dimensions and requiring a complete redesign/refit of the steering?

Mark
I don't know exactly what he did . . . but three possibilities come to mind.

1. I am assuming these are carbon shafts, and there are lots of grades of carbon/epoxy. In particular there are some epoxy nano resins that greatly increase laminate 'toughness'. That would be an easy upgrade.

2. It may normally be a hollow shaft, and if so there would be room within the spec dimensions to make thicker walls

3. They could have had the shaft diameters increased with correspondingly larger rudder bearings and tiller arms. That would not be all that hard or expensive. We in fact did it on Hawk, increasing the rudder shaft diameter from 4" to 5", which provides an extraordinary amount of extra strength.

Note: the owner is probably not short of funds, as he is described as a "swiss hedge fund investor". He might well have asked a NA 'what can I do to get stronger rudders' and they might well have done all three above.

With carbon rudders in the ice, I might be tempted to carry a spare, as their failure model is essentially only to explode. I think a 'cassette system' would be the most preferred solution in this case, but that's way more design and engineering change to most existing designs, and probably usually not as practical a change as the above three.

Metal rudders have much nicer failure modes (bending and denting rather than shattering) . . . . but heavy. A light carbon rudder for Hawk is about 40lbs, where as our 'ice class' aluminum one is +100lbs, so you could carry a spare carbon one and still be ahead on weight (but of course changing it in arctic waters would possible but no picnic.
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Old 15-09-2013, 08:57   #37
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Re: Are there latitude limits for cat sailing?

Recent Catanas have Kevlar on the hard points. They use Twaron which is a brand name just like Kevlar. It's basically the same stuff.
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Old 15-09-2013, 09:32   #38
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Re: Are there latitude limits for cat sailing?

Old Catanas use that also. It's not just hard points - I believe there is an entire laminate layer of it.

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Old 15-09-2013, 10:06   #39
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Re: Are there latitude limits for cat sailing?

My first choice would be a Catana - strong boats that sail well. Yes, I know they are expensive boats. The upside is that they seem to keep their value well too. Expect something like 0.4 for a +40' boat.

If I could not have a boat that I could trust 100% I would rather skip the Cape Horn part.

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Old 15-09-2013, 11:01   #40
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Re: Are there latitude limits for cat sailing?

+1 on the previous 2 posts.
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Old 15-09-2013, 11:04   #41
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Re: Are there latitude limits for cat sailing?

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Originally Posted by Sand crab View Post
Recent Catanas have Kevlar on the hard points. They use Twaron which is a brand name just like Kevlar. It's basically the same stuff.
Quote:
Originally Posted by colemj View Post
Old Catanas use that also. It's not just hard points - I believe there is an entire laminate layer of it.
Mark
A lot of boats do. The question is 'there enough for ice purposes'. In some boats the amount is just there for 'marketing purposes'. It's a hard question without straight answers from the builder (which you may only get if you are buying new) and input from an engineer.

My personal preference for taking a glass boat into ice, mentioned in a post above, are stainless plates at the cutwaters. During 'summer cruising' that's where you get real ice action on the hull, and they are not hard/expensive to add (And can be removed later).
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Old 15-09-2013, 11:29   #42
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Re: Are there latitude limits for cat sailing?

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A lot of boats do. The question is 'there enough for ice purposes'. In some boats the amount is just there for 'marketing purposes'. It's a hard question without straight answers from the builder (which you may only get if you are buying new) and input from an engineer.
I just checked the Lagoon, FP, and Leopard sites and they don't say they do. But all 3 of these sites absolutely suck on hull construction data. Who's in charge there? Anywho, I would like to know other production boats that use this.
There is a recent revived thread about a Catana 50 that had a collision with an Outremer 49 and the Catana lost. You might be right about the skimpy kevlar. Good pics!
Relying on Autopilot too much? Crashed Catana pics - Multihulls4us Forums
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Old 15-09-2013, 22:35   #43
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Re: Are there latitude limits for cat sailing?

Some of the new mono hulls advertise a Kevlar layer added into the bow section but like another poster has said, its probably 90% marketing and 10% added strength
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