MERLIN ROCKET FORUM

Topic : Aligning Spreaders

The project for this winter has been to recalibrate my rig and I'm having trouble getting it to stand straight.

Superspar Carbon - Winder fixed spreaders - Winder CT hull

With no lowers on the mast is upright but has a wiggle at the spreaders.

Any tips on removing the wiggle before then centering the lowers?


Posted: 02/01/2007 17:16:03
By: Hank of Marlow
Initial thought is one spreader must be longer than the other to get a wiggle!


Posted: 02/01/2007 17:27:10
By: Alan Fuller
If they are fixed spreaders i'd be very suprised if they are assymetric.

It's more likely that the line that takes the multi-purchase from the shrouds to the kingpost has stretched more on one side than the other. I recently replaced the ones on 3602 and they have stretched about 6 inches on each side (Excel racing = dyneema).


Posted: 02/01/2007 17:32:07
By: Chris M
Yeh but!  If the shrouds move smoothly through the spreader tips, as the should do, then if one side has stretched the mast would lean to one side, granted that would effectively make the spreader asymetric so may cause a wobble, but Hank said the mast was upright.  Maybe Hank only checked fore/aft uprightness and not side to side.


Posted: 02/01/2007 17:57:40
By: Alan Fuller
No but! I've used the kite halyard to check the distance to the deck and it's within 1-2mm.

I think part of the problem is that one spreader has been repaired and may be slightly misaligned. The repair looks good but is it good enough - probably not.

Any bright ideas on how to measure it accurately?

Cheers - H


Posted: 03/01/2007 12:41:10
By: Big Hank
I would have thought if you can't detect the difference with a bit of string and ruler, then it is going to so small an error that it won't do anything.

But, here is a thought. Case one spreader, in plastercine, leave the top or bottom exposed, mould it all the way up to the mast and bracket, then use the cast to line up the other spreader, if you do it well enough you could detect all sorts of differences, angle, alignment length, twist. From the Blue Peter school of engineering.


Posted: 03/01/2007 13:27:45
By: Alan F
What way is the wiggle?

Are you doing this with teh main and jib up, or just the jib?


Posted: 03/01/2007 13:36:42
By: Alan F
The plasticine idea is intruiging Alan, if a bit time-consuming.  However a more direct approach would be to set the mast up with the shrouds out of the spreader tips and measure the deflection of each spreader from the shroud, alternatively run a piece of string from hounds to deck and measure the same  Should pick up any discrepancy.  You are looking for roughly neutral fore and aft and deflecting shroud out by about 1.5 ins IIRC.  There's a good article on the website


Posted: 04/01/2007 17:27:10
By: Andrew M
All this spreader talk and such like is why i moved to an OK haha


Posted: 04/01/2007 18:29:04
By: Russ
Yeh, that was my thoughts, but if the repair has introduced a twist of asymetric deflection, measuring with string wouldn't pick it up, but I would have thought any defect could be sighted visually if it was significant enough


Posted: 04/01/2007 20:26:20
By: Alan F
My theory is, but Hank hasn't confirmed how he is setting it up, that some how the jib halyard isn't running true down the centre of the mast, maybe because it is looped behind the main halyard, which tend to run down one side. With the tension on an the asymetric pull it could cause a wobble.


Posted: 04/01/2007 20:29:28
By: Alan F
.....where there is just as much chatter about the properties of different mast sections and measuring their bend characteristics to match sails ;)


Posted: 04/01/2007 20:30:18
By: Touche
Ahhhh Touche,

You too must visit the OK web site and see how us nerds c/w anoraks analyse mast bend charateristics to math our crispy sails. Luuuuuurvly stuff!!!


Posted: 04/01/2007 21:39:51
By: Richard Battey
Tis true, when i bought my ok i didnt realise the bullsh!3t that came with sail and mast combo's, i had only just got to terms with sreader deflection setup, rakeetc etc.


Posted: 04/01/2007 22:52:06
By: Russ
This is only with the jib up and furled - no other sails.

There is no tension in the main or spinnaker halyards.

The twisting is visible when sighting up the track. with a normal amount of rig tension (Bottom E#)

I am sure that the spreaders are the only factor inducing bend and therefore the source of the problem.

A few calls have resulted in the following advice.

Check that the line between the spreader ends is athwartships and perpendicular to the heel tenon.

Jacko and Windy both set their masts on the bench and use a spirit level up the side of the heel tenon to set it vertically.
Then put the level across the shrouds at the spreaders adjust the spreaders to match.

Jacko also suggested (like Andrew M) taking the shrouds out of the spreaders and measuring the offsets.

Tom Stewart suggested lying the both on its side with the hounds (not tip) supported. A line between the shrouds at deck and spreaders will allow the alignment to be checked.

Now I need a warm, dry and windless day to get it all sorted; bang goes the winter series then.

Tom did also suggest not worrying about it and just going sailing - sounds good to me.

Hank - the stringman


Posted: 06/01/2007 16:05:49
By: Hank
Just go sailing for now - any bad results can be blamed on this rig issue. Then sort it out in the spring (and hope the results improve!).


Posted: 07/01/2007 12:50:46
By: Mags
While b4y no means a good thing, i'd be suprised if you notice a very slight sideways bend.

By the time you've pulled the sail up and got power in it it will ve bending sideways anyway!

Sure, it needs sorting, but i wouldn't be too paranoid.


Posted: 08/01/2007 12:44:55
By: Chris Martin

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