Mizzen uppers/lowers -- MOA

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Date Posted: - Tuesday - 03/22/11 - 8:10pm
Author: Paul M31 #106 NJ
Subject: Mizzen uppers/lowers

Perusing the many pictures under the owners group here, I note that the upper and lower shrouds seem to be connected to the center or forward rear chainplates...

with the missing back stay for the mizzen, I would think the preferred position for the upper shrouds would be the center chainplate - thus providing for swept-back spreaders and prevent the mizzen from moving forward. The forward and aft chainplates then are left for the lower mizzen shrouds and split backstay of the main mast, respectively.

Those that have the upper shrouds on the forward chainplate (parallel to the mizzen) and the lowers on the center (aft of the mizzen) - what would be the thought behind this set-up?

Am I missing something???

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Replies:

[> research -- Paul M31 #106 NJ, - Monday - 04/ 4/11 - 8:45am

Done some research and it turns out I need to swap the uppers and lowers for the mizzen so that the upper sits (like most of you have) parallel to the mast and the lower on the next chainplate aft (the middle one) - the split main backstay stays on the most aft chainplate.

This should also resolve my shroud "touching" issue - as you can see in this picture, there is contact.

With the corrected situation, however, there will be more need to use the running backstay - especially when I fly the mizzen staysail.

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[> Mizzen Chainplate Position -- Kathy Campbell Shadow M32#3, - Monday - 04/ 4/11 - 12:54pm

Paul,
I've been meaning to ask you about the mizzen mast position and where to attach the shrouds. When you had your mast positioned with the uppers attached to the middle chainplate did you check to see how much rake the mast had? I read an article by Brian Toss that talked about putting enough rake in the mizzen mast. When Shadows mizzen was up I measured about 9" rake with a plumb bob. That was with the mizzen upper attached to the forward chainplate. Shadow seemed to balance well. How did your Mariner balance with the upper shrould on the middle chainplate?
The pictures are nice.
Kathy

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[> [> Mizzen Rake -- paul M31 #106 NJ, - Monday - 04/ 4/11 - 4:49pm

As you can see in the picture, the rake of both the Main and the Mizzen is minimal... I would say perhaps 3 inches on the boom using a plumb bob - I also don't think moving the stays to their proper position will change the rake by much.

When I step the masts this year, I will see if I can induce a bit more rake - I like it to be arounf 6-7 inch on the main and around 5 or so on mizzen - too much and I am afraid to produce too much weatherhelm.

Last year the balance of the boat was minimal wetaherhelm - I'd like to see a tad more for safety.

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[> Swapped the stays back to the wrong right position -- Paul M31 #106 NJ, - Wednesday - 06/22/11 - 8:25am

After having had the stays as most of the boats on this forum, i.e. uppers parralel with the mizzen and the mizzen lowers aft, I decided to reverse them back to the wrong positions, i.e. uppers aft and lowers parallel to the mast...

Unless the triatic is supposed to be slack - pulled on only when there's force on either topping lift or from sail/mizzen sheet combo, the tip of the mizzen tends to always be pulled forward, bending the mast in that direction.

While under sail - especially with my relatively heavy load mid-mast from radar transmitter and radar reflector, the mast seems to be subject to "pumping" in mild chop.

While going down wind - especially when using the mizzen staysail, there is no "stop" on the mizzen from bending further forward, while putting huge stresses on the lower stays mounted aft (providing the only balance) - necessitating the use of a running backstay even in lighter winds (I do use one all the time in heavier winds)

All this has lead me to the conclusion that the better position for the uppers on the mizzen is on the aft chainplates.

YMMV

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[> running backstays -- Lyle Harris, - Wednesday - 06/22/11 - 12:39pm

I'd like to see a diagram/photo of running backstays for an M31.
thanks,
Lyle Harris
Greywolf M31 #42

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[> Picture Same set-up, but not my boat. -- Paul S31 #106 NJ, - Wednesday - 06/22/11 - 1:10pm

This would be on either side (the windward side) of the mizzen - connected to the same tang on top of the mizzen as the topping lift. Some have a single setup which is switched when tacking; others have one set up on each side.

Hope this helps a bit

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