Upper and lower spreader mal alignment

[andyhillan]

I replaced the standing rigging on my Corsair II this year but note that the cap shrouds are not running from deck to masthead in a straight line. It appears the upper spreaders are slightly swept aft causing a slight zig zag in the caps. I am not sure if this was the case prior to my re- rig - I never noticed. Wonder if anyone has had this issue and what is the remedy?
Andy H

[Jolly Roger]

I am not directly familiar with the Corsair rig, but a lot of spreaders are swept aft by about 10 degrees. My Fulmar has swept spreaders, as do lots of other boats. The reason is to introduce a slight bow in the mast to hep flatten the mainsail.

If you are not sure if your rig is tight enough you will need to be on a stiff bead and check the tension of the lee shrouds, they should remain hard. Also sight up the mast to check for any lateral bend, you may need to adjust the lowers to do this.

One other thing you should check is looking from a distance either from the bow or stern and see if both spreaders are bisecting the angle between the upper and lower sections of the cap shrouds. If the boat is floating upright then the ends of the spreaders should also be level.

Hope this answers your query.

[andyhillan]

Thanks very much for your reply. The rig is a masthead configuration with in line spreaders upper and lower. I've been looking at loads of similar rigs whilst cruising W.Scotland and Ireland this summer and invariably the cap shrouds run dead straight from deck through both spreader ends to masthead. My caps seem to be deviating aft at the level of the upper spreaders by 30 or 40mm. The rig is pretty well tensioned I think.
Andy

[Jolly Roger]

I feel a trip up the mast may be necessary to check the spreader bases. Look for any excessive gaps between the mast and fitting in case a fixing has come loose or excess play where the spreader enters the base. Also sight up the side of the mast and see if both spreader bases are in the same position on the mast. Another possiblity could be you reversed a pair of spreaders when refitted e.g. port for starboard. All of these have the potential to affect the position of the spreader ends.

[andyhillan]

thanks Roger
I think you are probably right re the mast bracket for the upper spreaders - the crane used the upper spreaders to lift the mast, and estimated the mast and rigging (in mast furler) weighed in excess of 1 tonne (1200kg approx.) - so the lifting strap may have bent or damaged the mast fitting in the process. I just wondered if any other westerlys had similar issue that might have suggested a fault from initial rig set up (unlikely I think - Westerly paid great attention to detail and their Quality Control was excellent).
Andy

[mikebuggy]

The Oceanranger uses the same rig. No relation to the Fulmar Rig. It's a stiff mast with fixed double spreaders directly across the beam. As a matter of interest, and within reason, the spreaders are reversible within each pair, although over time, pin wear may make the various holes differ slightly from side to side.
While the spreaders should be directly in line across the beam, and vertically, they do have an upward sweep of about 10 degrees. The angle is set by measuring and marking up the end clamping position while the rig is on the ground. The socket bases and pins (2 per side per spreader) make the spreaders sit exactly across the beam.
The Monel rivets on the socket bases do wear and corrode and 50% should be replaced every 10 years. Worn rivets are indicated by the socket bases not sitting firmly on the mast extrusion. Wear can also be tested by 'swigging' the shrouds fore and aft and looking for movement in the spreaders. The rivets securing fwd part of the upper spreader bases are prone to stretching often causing the fwd part of the castings to lift away from the mast. This may have occurred on this occasion.
This mast should always be lifted at a point just above midway between the spreaders. It should not be lifted by the spreader bases.
The mast can be supported by the lowers and baby-stay, plus all halyards and backstays while the shrouds are released to investigate. Although risky, it is possible to unclamp the top spreaders, and remove the base socket pins in order to work on the upper sockets with the mast in situ. (I have replaced wires and spreaders on this mast while the mast was standing a number of times). Although nerves of steel are required, and some strength and dexterity, It is possible to drill out any stretched rivets on the upper sockets and renew them while in situ. It would be more comfortable to do this from a crane or hi-lift with a proper seat. There is a technique for drilling out the old rivets. You may need advice on this. Note that monel rivets of this size are extremely expensive.
Hope all that helps.

Mike Buggy
Surveyor.

[andyhillan]

Mike - many thanks for this reply - sounds like a combination of crane trauma plus wear and tear - I will replace the upper sockets and make sure there are no expensive boats alongside me when I do! Will let you know how I get on,
Andy

[rhumlady]

Mike,

I have always seen masts lifted with a strop under the spreader base although I can't recall which ones on a double spreader rig. I can't see how else you would lift it.