Spreader angle

SvenglishTommy

SvenglishTommy

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I'm launching tomorrow and have to re-step the mast. Previously, the spreaders were horrizontal and so had a different angel to the shrouds above and below. I was reading in Calder's book that the angle of the spreaders to the shrouds should be equal above and below, rather than 90 degrees to the mast.

Does the panel agree that this is the case, and can this angle be measured and the wire holders in the spreaders tightenned before the mast is up, or does it involve aerial acrobarics and a protactor?
 
It can be done with the mast down.

1 Measure distance from mast foot to chainplate on one side.
2 Rig spreader and get accomplice to hold shroud as tight as possible with correct distance at foot of mast.
3 Angle spreader to suit and tighten spreader fixture on shroud
4 Measure distance from mast head to spreader.
5 Either repeat on other side or just measure down from mast head and fix spreader at appropriate distance.

All above is approx - but will be accurate enough.

If you are racing on the other hand...........

Donald
 
Thanks Donald, the only bit I dont get is "4 Measure distance from mast head to spreader." What am I supposed to measuring it for?

I dont race very often, the last time I did the rowing boat was left for dust and dont think spreader angle would have changed that /forums/images/graemlins/smile.gif
 
With the greatest respect an easier explanation might be:

Take the shroud and stretch it close to the mast. Mark the shroud with tape or indelible marker where the foot of the spreader is. Now swing the shroud out and clamp the spreader tip at the marked point. This will mean that you will have bisected the angle at the spreader tip as close as necessary for all rigging purposes.
 
And the reason for this is that with the spreader fixed horizontally, there is a tendency for the spreader to be pushed downwards. If the clamp holding the shroud to the end of the spreader were to slip, the spreader would slip downwards and the top of the mast would bend over and probably break. Well worth getting it right then!
 
John is absolutely right,If you use his method and you don't get a pretty accurate bisection of angle your spreaders are the wrong length!
 
Tommy's boat was obviously sailed successfully with spreaders horizontal or fixed at a suitable angle slightly above horizontal. If the construction of the spreaders especially the base is such that a load slightly off centre can be supported then the wire may be left sliding in the spreader cap and it will find it s own position.
If however the spreader is floppy in the up and down plane then it does need to be positively located on the stay wire and in the correct angle.
Obviously the angle if it is fixed must take into account the stretch of the wire as the stay is tensioned. So I would if I thought it necessary push the spreaders up to the correct angle and clamp the stay wires to it after the tension has been adjusted. In my own boat however the wire runs free in the spreader. The spreader base is fairly robust and the boat and mast relatively small. So for a larger boat or more fragile spreader base then your suggested methods are more desirable but not always of such concern.
It would be worse to have the stays fixed in a position which put undue pressure on the spreader to bend it where it don't want to go by fixing the wire in the wrong place.
good luck olewill
 
[ QUOTE ]
If the construction of the spreaders especially the base is such that a load slightly off centre can be supported then the wire may be left sliding in the spreader cap and it will find it s own position.


[/ QUOTE ] William, I don't like to argue with you, but on many boats, the spreader SHOULD NOT be left sliding in the spreader cap. On some rigs, the natural position of the spreader would be cocked at an acute angle up or down the mast and leaving the spreader tip to slide could be fatal to the rig.[ QUOTE ]
Obviously the angle if it is fixed must take into account the stretch of the wire as the stay is tensioned.

[/ QUOTE ] Do you have expecially stretchy wire in oz? On my rigging, the wire stretches a few mm when the rig is tensioned up. The proportion of stretch at the spreader is about half of this. The tips of the spreaders are raised about 250-300mm. On my 15 metres of main shroud the few mm of stretch makes no difference to the spreader angle that I am going to worry about. [ QUOTE ]
It would be worse to have the stays fixed in a position which put undue pressure on the spreader to bend it where it don't want to go by fixing the wire in the wrong place.


[/ QUOTE ] True - but most rigs which require the spreaders to be raised to bisect the angle of the shroud at the tip have spreader sockets made to allow for the correct positioning - or at least they do on most of the boats I sail.
 
High John yes I am not inclined to argue however perhaps the points I make are worthy of thought even if in many cases they are not applicable.
If the wire is to be attached to the spreader end before the mast is raised then it must be attached with some tension between the spreader and the mast top which would leave the spreader under stress upwards until the tenion can be applied from below. Which doesn't appeal much. However you may be right that it is insignificant and I must applogise that my perspective is from a small boat view. I have been involved with a larger boat with rod rigging and individual adjustments for each section of shroud and intermediate wires. But this involved adjusting from a bosuns chair.
Yes of course spreaders should be mounted and intended to remain some degrees above horizontal. Thanks olewill
 
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