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Old 28-10-2013, 01:16   #1
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Should I move my mast

HI folks,
I am in a quandry, my tri was originally rigged as a ketch. The mizzen was always in the way I didn't use it much so I removed it.
I have been told I need to move the mast and rig the boat as cutter, in order to balance the boat. So far I haven't had any problems with helm. Max wind I have sailed in so far are 30 knots gusting to 35 or so. The boom is 3 feet shorter than called out in the plan. Not sure how that happened but it wasn't me. The current mast is 40 feet. This is a rather elderly Cross 38. I have plans for a cutter rig with a mast height of 46 feet. Also I have a large Lefiel mast section that came off a cat to replace the original rig if need be., and a longer boom. Perhaps I should just rig the longer boom per the original plan.
To borrow a phrase What say you?
Rich
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Old 28-10-2013, 04:46   #2
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I have two yachts of same design. One is ketch with largish mizzen and other is cutter rigged sloop. Others have been single headsail. Mast stays in same place no matter what rig. Maybe play with sail sizes to balance the rig. Yacht design texts will give good guidance in this.
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Old 28-10-2013, 05:40   #3
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I can't speak to your particular boat, but ours was made as both ketch and cutter. The cutter version mast step is roughly 2' aft of the ketch version. Having sailed without the mizzen for a while, I found I needed the mizzen when in extremely light air and heavy wind, the middle of the range wasn't as much of a problem except for the bow diving after tacks. But that has a lot to do with the keel shape too.
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Old 28-10-2013, 07:43   #4
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Re: Should I move my mast

Short story - Leave it alone. Many Cross 38s were initially Ketch type rigs. Many have dropped the mizzen and many of those have successfully sailed the world.
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Old 28-10-2013, 08:23   #5
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Re: Should I move my mast

Are you a qualified naval architect? Do you understand all of the engineering equations, and all of the other variables, related to doing something like this?

The answer to these questions will be exactly the same as the answer to the question of whether or not you should try to completely redesign the design characteristics of your boat on your own.
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Old 28-10-2013, 08:35   #6
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Re: Should I move my mast

If the boat balances well as is, what do you expect to gain by the heroic effort of relocating the mast? That part seems a no-brainer to me!

If she seems to suffer from lack of sail area in light airs, a larger mainsail via a longer boom might well help. This should not bother the balance too much at any time, and as you then reef the larger sail down in stronger winds the sailplan will revert to something very like the original.

Adding the taller and heavier mast section might be a bit more problematical with greater mass aloft and greater stress on chainplates and standing rigging. I'd want more expert advice before going to that expense and effort.

Good luck with this interesting project.

Jim
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Old 28-10-2013, 09:14   #7
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Re: Should I move my mast

The Cross cutter rig is stepped further aft with a support post running down to the keel in the main cabin from the cabin top. Jeff Turner should be able to get you plans at Cross Multihulls. That said many a Piver ketch had the mizzen removed with no other changes and sailed fine. If you have some lee helm the longer boom would help. For balancing a storm jib you might consider a backstay staysail instead of a mizzen. The only real change I'd do besides the boom is add a removable inner forestay for a storm jib to make a double head sloop. This also works great with a spinnaker .
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Old 28-10-2013, 09:32   #8
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Re: Should I move my mast

Quote:
Originally Posted by Jim Cate View Post
If the boat balances well as is, what do you expect to gain by the heroic effort of relocating the mast?

Jim
Yep!

/Naval Arch.
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Old 28-10-2013, 10:11   #9
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Re: Should I move my mast

What Cavalier said. For the ketch the main mast is stepped on the main beam at the front end of the forward cabin. For the Cross-designed cutter version the mast is taller
(as you found out) and stepped about 3' further aft. This requires a compression post (if deck stepped) and reinforcement of the floor/keel area where the mast will be stepped. Also means moving all the chainplates, new rigging, new sails... Not a minor effort.

Our 40 (which is the 38 stretched by Norm) is the cutter version and we really like that rig. I suspect your boat would perform better with the as-designed cutter rig rather than the mizzen removed sloop, but may not be worth the effort. Take her out sailing a bunch and see what you think. I probably wouldn't, however, recommend just extending the boom, as that will significantly affect balance.

If you need plans I can probably dig up our set and copy out the relevant sections if Jeff doesn't have what you need.
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Old 28-10-2013, 11:03   #10
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Re: Should I move my mast

Qualifier: I know very little of the specific design and know enough engineering to know what I don't know without looking and calculating.

How about increasing the rake? This is common practice on some boats as a means of moving the COE and increasing lift for the bow. This could be simple, if the mast is deck stepped and depending on the step and compression post design. If keel stepped or the compression post and step would not like this, some changes will be required. This is what I would explore first. Moving the masthead as much as 2 feet aft should be conservative.

You can always lengthen the boom several feet and add a little more mast, but I would be cautious about adding more than about 2 feet of boom and about 4' of mast without a very close look at the structure.

-----

Really, you need to consult with a designer or at least a rigger and sailmaker that have been involved in such work. You will be replacing a lot of rigging and sails.

-----

Try changing the rake-only first and see what that does.
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Old 29-10-2013, 16:31   #11
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Re: Should I move my mast

If it balances and you are satisfied , leave it alone , send me the money that you save .
Many times a boat that is sailed in the trade winds will have sail area reduced by the owners , lot easier than reefing all the time . On every sail boat that I have owned and sailed in windy parts of the world , I would always remove the battens and remove the roach from the main .
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Old 30-10-2013, 22:00   #12
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Re: Should I move my mast

Leave well enough alone if she sails well in this configuration.

You will save time, money and headaches.
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Old 03-11-2013, 01:17   #13
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Re: Should I move my mast

I forgot to mention that my sails are in need of replacement and the rigging is becoming rather dated, at around ten years of age.
The suggested cutter rig was drawn by a well respected multi hull designer.
Rich
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Old 03-11-2013, 04:56   #14
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Re: Should I move my mast

Sounds like you're wanting to build a case for doin it - and nobody can stop you . But as others have said, just having some plans is not a sufficient reason for doin it. There are usually cheaper alternatives for any balance issue than a re-rig. For example, if it's more helm you're after then, as a poster above suggests, try some more rake. It can be surprising how effective (and cheap) this simple adjustment can be. Best not to rush into an expenditure you'd likely come to regret.
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Old 03-11-2013, 10:40   #15
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Re: Should I move my mast

Cruising tris can handle a large range of rigs if the combined center of effort is kept in the same location. For non tri sailors there are a few things that are different. As the boat immerses more of the lee ama (float) in stronger wind some lee helm is created so it is helpful to have the boat set up with some weather helm. Here are some tested Nicol rigs that all work on the same boat. The one they didn't offer was a cutter because the compression post would get in the way down below. The sloop was fastest, the ketch good at reaching, the yawl a better 2 masted rig to windward because of the separation between the masts and sails. Boom length quite varied and doesn't affect the balance if the C of E kept in the right place. Rig height and weight does affect pitching and should be considered carefully. Tri ketches with too much sail forward have a tendency to bury the bows hence the lower masts.
If you do go for the cutter I'd use the Norman Cross rig as it will balance with all the hulls parameters.
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