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Old 24-06-2013, 08:44   #1
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I want to move my mizzen aft.

It would be nice to move my mizzen aft 5 feet. Its in the center of the cockpit and kinda in the way. The mechanics of physically moving it are not a problem. The problem is that I dont know enough about sailing to ask the correct questions about how it will affect the boats sailability. (Is that a word?) Shes a 50 ft steel Roberts, drafts 6.5 ft, 14.5 ft beam, 5 ft freeboard.

What problems may arise if I simply move it aft, get a longer main boom, a shorter mizzen boom and sails to fit?
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Old 24-06-2013, 08:46   #2
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Re: I want to move my mizzen aft.

I'd say that if you're a naval architect and know more than your boat's original designers, you should go for it.

Otherwise, maybe get a different boat.
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Old 24-06-2013, 08:52   #3
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Re: I want to move my mizzen aft.

Yes, there are sailing reasons to not do it. For one, the larger mainsail would give you increased weather helm. For another, the chain plates for the mizzen mast would have to be moved, and this will probably involve hacking up your interior to install proper backing plates to distribute the loads, whereas, this has already been done in your vessel. Frankly, I'm with Letsgetsailing3 on this one, if you can't live with the cockpit obstruction, get a different boat, because you'd really be opening a huge can of worms with this if you start, and risk ruining the boat, too.

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Old 24-06-2013, 09:15   #4
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Re: I want to move my mizzen aft.

Am no expert (Lol!), but I think the Centre of Effort would be moved forward (Mizzen gets smaller and more irrelevant, and mainsail gets bigger).....how that would affect the boat I don't know! My guess is that if you already have a bowsprit could correct that by lopping a bit of!

Of course would also depend on how big the mizzen now is (in comparison to overall sail plan).

Maybe have a word with the designers to see what they think, or have done already (my guess is that a squillion variations already on standard for their boats).

I too have a ketch, but only 30 foot of. I have wondered what would happen if I removed the mizzen entirely and went for a longer boom with a Gaff rig! (never gonna happen, but I like pondering!).
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Old 24-06-2013, 09:23   #5
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Re: I want to move my mizzen aft.

Five feet on a 50' LOA boat is a long way! Don't do it.
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Old 24-06-2013, 09:51   #6
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Re: I want to move my mizzen aft.

So weather helm would be increased. What else? If I left it where it is and just raised the boom mount on the mizzen by 16 inches so I dont bonk my head on it would I see any sailing issues, other than a smaller sail area?
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Old 24-06-2013, 09:53   #7
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Re: I want to move my mizzen aft.

To be sure I will consult with Mr. Roberts prior to a big change like this, just thinking out loud.
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Old 24-06-2013, 09:58   #8
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Re: I want to move my mizzen aft.

Reduce the foot length on the mizzen (shrink the boom?) to compensate for the increased leverage? If it's a wooden boom you can honestly just keep hacking off the end until you get to a spot where it all works well.

If you've got the boat opened up maybe it won't be a big deal to move the chainplates around but that's something I'd give some thought to.
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Old 24-06-2013, 10:07   #9
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Re: I want to move my mizzen aft.

Quote:
Originally Posted by Matt sachs View Post
So weather helm would be increased. What else? If I left it where it is and just raised the boom mount on the mizzen by 16 inches so I dont bonk my head on it would I see any sailing issues, other than a smaller sail area?
This would likely be a less-impactual change, although by reducing your sail area aft of the centre-of-effort it will increase the tendency for your boat to develop lee helm (the opposite of weather helm). The impact of this 16" change will depend on the size of your mizzen sail. You can compensate by reducing headsail size. In general, lee helm is more dangerous.

Centre of effort diagram

It's all about balance with sail rigs. The designer (presumably) placed and sized the mizzen intentionally. A consult with the designer would be wise.
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Old 24-06-2013, 10:27   #10
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Re: I want to move my mizzen aft.

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Originally Posted by Matt sachs View Post
So weather helm would be increased. What else? If I left it where it is and just raised the boom mount on the mizzen by 16 inches so I dont bonk my head on it would I see any sailing issues, other than a smaller sail area?

That's certainly a lot less drastic, but again, if you're considering this kind of change you need to consult a naval architect. They have software and knowledge of these kinds of systems that can help you find a solution without completely screwing up the way your boat sails.
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Old 24-06-2013, 10:38   #11
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Re: I want to move my mizzen aft.

Moving mizzen mast doesn't mean your have to mess up with other sails. Just rig a lug sail or smaller mizzen with a mizzen staysail instead and CE stays in the old place..
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Old 24-06-2013, 10:58   #12
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Re: I want to move my mizzen aft.

I think raising the boom would work. You should be able to compensate with sail trim. What % of the mizzen would you be loosing? You could also consider a new battened mizzen with more roach to compensate for the lost foot area. Learning to duck would be cheaper and faster, good luck!
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Old 24-06-2013, 15:32   #13
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Re: I want to move my mizzen aft.

here is a simple question..

How does the boat sail without the mizzen raised?..

if you can get decent speed, and balance the helm, then the real cheap answer is simply to de-step the mizzen mast. problem very much solved for free.
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Old 24-06-2013, 15:49   #14
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