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125 Discussion Forum
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Return to the Forum List  Spreaders | What every ones ideas on Spreaders ?
long or short? and why?
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| | Re: Spreaders | It always amuses me when sailors copy other boats without understanding the basics.
The 125 is relatively under powered with a soft mast. The cross trees or spreaders on the mast control mast bend and hence mainsail shape.
You need to look at the mainsail and try to achieve the correct sail shape. This will vary a lot depending on the cut of the sails and crew weight on the wire. It is quite remarkable how the pressure on the windward trapeze changes mast shape.
Read a few books and learn about sail shapes.
The length of a cross tree will control side bend, ie a long one will have the pressure from the tight windward stay pushing the mast to leeward and the top will rotate about the side stay hounds and stand up straighter. A short arm will let the mast go to windward, opening up the jib slot more with the top of the mast laying off to leeward. The sail will be flattened and less powerful.
The for and aft adjustment will limit how far the centre of the mast can move forward until restrained by the cross tree arm locking its movement. It tries to pull the side stay forward.
A lot of forward movement will result in the head of the mast going back and creating a lot of mainsail luff round. ie sail cloth is removed and the sail is flattened.
It is important to realise the forward/aft & sideways bends work simultaneously. You must balance the mainsail shape to the weight you have to sail the boat.
Smoother seas can have flatter and higher pointing sails whereas lumpy seas will require more power to drive through the slop.
Higher performance boats eg. Sharpies have an adjustable rig that is being played all the time to achieve the ideal mainsail shape. It is reasonable to expect that in a 125 you may have to adapt the mast shape to the conditions/crew prior to leaving the beach. There is no single setting. The skill is knowing how to change gears for optimum results.
A teenager who is growing rapidly, may find that the settings he sailed well with at the end of the season, is no longer ideal at the start of the next season. Only looking at the mainsail and understanding it will get the optimum result.
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| | Re: Spreaders | Dons comments are all very true.
Here are a few things to think about also:
A 125 mast is not tapered above the hounds, so reacts differently to many classes.
A 125 sails as a "pointing boat" in speeds that it wont plane in, but changes dramatically when it does pay to plane.
A 125 is a dinghy with generally a light crew on trapeze.
A 125 is not a keelboat so is looking for a little more response from the rig to help sail it.
Many 125ers use stiffeners, varying in length/materials, and this changes the sections characteristics.
I reckon the best thing you can do is talk to people about why they have their set up as they do and understand it before copying. The sailmakers who are making the good gear will also have their theories so their comments re luff rounds they cut into their mains is vital.
Ideally, your sailmaker will ask you to do a bend test on your mast so he can match it. But if you buy sails from interstate lofts you would be better to match your mast to what he/she can tell you.
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| | Re: Spreaders | have a think about the tension in the stays changing from when you dont have someone wire to when you do also. obviously the crew caries a lot of the windward stay load when they first get onto wire in marginal. (tightening the leward one conversly)
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| | Re: Spreaders | thank guys this just the type of info that i need help re-rig my mast and speader sit up
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| | Re: Spreaders | Ok..so the 125's have had the same mast and spreader setup that ALL the top boat have run for like close to 10 years.... put the up the the top.. don't try and reinvent wheel... the mast coming from different between suppliers are massive,just measure a top boat from where u are from as a start..Find a fast setting and leave it in the one spot.
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| | Re: Spreaders | actually, for the last 6 years the only boats thhat have had the same spreader height that have won is mk 2 and green out. jamie at lake maquarie and perth had his a bit higher, waterloo at paynesville had theres a bit lower and she waits for was similarly lower at adelaide
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| | Re: Spreaders | We were the first boat to move to maximum height spreaders way back in 1986. I did this to try to have more control over more of the mast, given that maximum height is about half way up the mast.
It has worked a treat ever since.
Our spreader setting was to push the stays out of their line, 50mm sideways and 30mm forward. This gave us reasonable control over sidebend and limited forward bend appropriately. This is without a stiffening tube in the mast.
With 180kg of sidestay tension, we would have about 12mm of reverse bend in the mast before we hoisted the mainsail. Once the mainsail was on the mast, This would staighten out.
As mentioned, the weight of the crew on the wire will tend to bend the mast more, mainly through the extra compression on the mast. By trying to keep our mast quite straight, we would limit that extra compression bend.
Since about seven years ago, the masts have become slightly thicker walled and stiffer. When we first used one of these, we noticed that he rig was a lot less responsive and we had to wind our spreaders back to a neutral fore and aft position to encourage a bit of 'breathing' in gusts. We no longer start with reverse bend.
There was an era with minimum height, very long spreaders, to try to control low down bend without the need of a stiffener. While this achieved it's aim, it left the rest of the mast too uncontrolled.
Jamie
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