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Old 12-27-2013
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mast bend problem

mast is up and straight side to side.
i'm unable to get the mast straight fore to aft above the spreaders.
it is bent forward the amount it seems like it should be aft.
i have roller furling which is hanging limp, not tight enough on the stay with the halyard tight.
yet there is no more adjustment on the split backstay turnbuckle.
i'm thinking of re stepping the mast
although since the step has only one bolthole i'm not sure if it would make a difference.
i'm also considering shortening the lowers on the backstay.
this is the first time i've raised the mast on this boat but everything seemed okay when i took it down.
any thoughts?
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Old 12-27-2013
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Re: mast bend problem

Just a "few" questions....
size of boat?
what make?
type of rig?
Compression post rotted?
are the aft chain plates pulling out?
Is the back stay proper on the mast head?
is the mast head broken. is the mast back wards? ( it has happened)
Are the lower shrouds pulling the mast fwd at the spreader height?
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Old 12-27-2013
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Re: mast bend problem

Quote:
Originally Posted by deniseO30 View Post
Just a "few" questions....
size of boat?
what make?
type of rig?
Compression post rotted?
are the aft chain plates pulling out?
Is the back stay proper on the mast head?
is the mast head broken. is the mast back wards? ( it has happened)
Are the lower shrouds pulling the mast fwd at the spreader height?
5.5 mirage
masthead rig
all fittings and rigging in good condition.
spreaders all level and raked aft correctly.
it just appears like the backstay is unable to pull the masthead back enough.
when i pull the split stays together the masthead does move aft.
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Old 12-28-2013
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Re: mast bend problem

If everything was fine before you took the mast down, then what could have changed when you put it back up? Did the forestay turnbuckle get wound out making the forestay too long? Is the backstay rigged the same as it was before? How much shroud tension do you have? If you have aft swept spreaders then shroud tension will induce bend and tighten your forestay. You say you are considering shortening the lowers...are they hanging slack? Do the uppers and lowers fasten to separate chain plates? If so, are you sure you haven't got them reversed?

It is a pretty tough thing to diagnose based on the info you provide, but you say everything "seemed" ok when you took it down. Is this boat new to you? Had you ever sailed the boat prior to taking it down?

Do you have any pics of the rig?
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Last edited by SchockT; 12-28-2013 at 02:05 AM.
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Old 12-28-2013
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Re: mast bend problem

All of the Mirage 5.5 pics I have found show spreaders are not swept aft at all, the uppers go to chainplates directly in line with the mast, and there are forward and aft lowers. Do you have a different rig from those boats?
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Old 12-28-2013
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Re: mast bend problem

Firstly, your rigg seems to be inverted. Not good for sailing. Fix it before you do anything else.

Secondly, what could be the origin of this and how to fix it? It is of course difficult to say without an inspection, much will be speculation.

Seems to be a traditional masthead, with forestay, backstay, right angled spreaders and forward and aft lowers. Mast top is however now pointing forward, but was OK before mast was unstepped. (?).

First guess would be that the lowers are not of the same length, and that the aft ones now are forward and the forward ones are aft (the forward ones is then slightly shorter than the aft ones). This forces the mast to bend somewhat back at the spreaders, leaving the mast top to go forward (due to the weight of the furler).
A small variation of this guess is that the aft lowers are too tight.
These guesses doesn't fully explain your issues with the backstay, but a bent mast is shorter than an unbent which could explain that part.

Not really sure how the backstay arrangement looks like. It is quite important that adequate tension can be applied, at a masthead this is more or less the only trimming point.

Good Luck

/J
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Old 12-28-2013
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Re: mast bend problem

Pretty boat!
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Old 12-28-2013
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Re: mast bend problem

GREETINGS EARTHLINGS; Check that the lower shrouds are the correct (Forward one forward and aft aft you get the message) this may help. AS ALWAYS GO SAFE
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Old 12-28-2013
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Re: mast bend problem

Here ya go ... probably the most comprehensive rig tuning guide available on the web: http://www.riggingandsails.com/pdf/selden-tuning.pdf

Do pay attention to the proper amount of mast 'prebend' as all sailmakers 'depend' on such to be present as this will greatly affect the shape and performance of your mainsail; correct forestay tension affecting the proper shape of the headsail.

The understanding when using such 'rig guides' is that the boat will be set up tensionwise for the typical 12-15kts of windstrength. A set up for 12-15kt. windstrength is the 'plain vanilla' starting point.
If you are seriously racing this boat then the boat should be set up 'tighter' for both higher and lower windstrengths ... but the wire should not exceed 30% when full loaded and the boat over (to about 45° heel angle) as over this value will lead to premature rig failure. For serious racing tensions you before racing (during trials and prelim. set-ups) attach a tension meter to the rig while sailing at its maximum and then then make tension corrections back at the dock, etc. Sail SHAPE is dependent on proper rig tension ... and mast 'pre-bend'.

Last edited by RichH; 12-28-2013 at 11:16 AM.
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Old 12-28-2013
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Re: mast bend problem

Is your boat on the hard or in the water? Adjustments should only be done with boat in the water. The boat can flex and change shape.
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