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Masthead gear


ScarecrowR31

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Did this to my 930 about a year ago, but was having the standing riging replaced at the same time so dont know what the individual cost was. But its a pretty simple conversion small set of forward swept spreaders, with dyform wire, and a new slot and block for the masthead halyard. I now fly masthead kite and gennaker without any problems. Makes a big improvement in downind performance, and the mast hasnt fallen over yet!

 

stu

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I'm not an engineer, and generally construction projects and building stuff is definitely stuff I leave to others. I saw your rig when Redline came in after the Wine Race Stu, so I know what you are describing.

 

What I don't understand is why the forward sweptness? Intuitively my non engineering brain would think that the jumpers should be aft swept - but clearly a lot of boats have them are forward swept, and a lot of masts don't fall down. I am not trying to say everyone has it wrong. I am trying to work out why I don't understand what is happening in those sections of the masts...

 

I figure the masthead kite tries to pull the top of the mast forward and/or sideways and forward, depending on the wind angle.

 

I figure that the jumpers are trying to support the top portion of the mast... therefore my brain says you need something to stop the top of the mast pulling forward.

 

Is where my brain misses the point that as the very tip of the mast gets pulled forward the middle of the top prtion of the mast (the portion above the top spreaders) is being bent or compressed backwards and lis likely to fail backwards? Is that it? So the jumpers support the middle of the top portion from compressing? And the top mast backstay tries to prevent the tip of the mast pulling forward.

 

Is that it?

 

or is it that the tension on the jumper wires presses the jumper struts into the mast, and that therefore forward swept jumpers press BACKWARDS into the mast?

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Good question, my jumpers are slightly aft swept. Just a smidge from being inline. My mast hasn't fallen over either. My guess it it will depend on the rest of the rigging and the type of section being used. But I do know that my jumpers are an ad on as they aren't part of the original rigging pan. It's not complicated but nonetheless I wouldn't do it myself.

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Topmast backstay stops the mast falling over forwards, jumpers take care of lateral (sideways pull) and support the top mast. Swept forward means the more backstay you give it the more tension on the diamonds, swept aft and max. backstay makes em go slack...

 

EE

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I was given the option by the rigger of two methods:

 

1) Cathedral type rig where all spreaders including this new top set would be swept backwards. Comonly seen on 7/8 th fractional rigs.

2) Std forward swept set of top spreaders. (Which is what I went for with my conversion).

 

Mostly coz I spoke to a couple of other 930 owners who had done this mod, and they were happy with 2).

 

The main backstay stops the mast from tipping forward with a masthead kite up.

The jumpers stop it bending sideways when you are on more of a reach with the kite.

 

Only down side is with option 2 if you use masthead gennakers the genny tends to get hooked on the top set of fwd swept spreaders in a Gybe. I now do outside Gybes with this sail, which has solved the problem.

 

stu

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I wouldn't do it myself only because I can't weld aluminium and lack the requisite skills to make them. I have a fairly strong mast section and so perhaps forward swept aren't necessary on mine - dunno, they just work. Perhaps the slightly aft swept jumpers are in aid of inside gybing, which I do with no problems at all.

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The only issue with forward raked jumpers is that when you go up wind in a blow, you cant pull backstay on to bend the top of the rig (Bonus is forestay tension comes) but you may struggle to flatten main. And when you backstay on upwind the jumpers get tighter and the rig doesnt fall off on the breeze.

 

I had inline jumpers on mine which was mint, stiff topmast no matter where the backstay is and you can let the main right out without the top batten popping inside out. But i have just changed it to cathedral and swept aft (Note you can go swept aft without cathedral still) and i love it like that because the backstay isnt an issue. and upwind in a blow you can backstay on and the jumpers soften allowing the rig to fall off to leeward and depower. If the backstay stretches downhill etc the jumpers only get tighter and the rig locks in nicely.

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Yep what he says when I think about it, as I can use topmast backstay to flatten off the top of the main if I'm getting slightly overpowered - which is nice. Slightly aft swept gives added support to the section when going downwind - although that isn't a license to forget about topmast backstay when throwing up the big gear downwind.

 

Halyard inside or out? Inside if there's room, although you will need to modify the masthead to take a sheave, (possibly means cutting, welding, reinforcing etc) outside if you don't want to do that or the section is getting too small. Talk to a sparmaker about that.

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A question for Bart and Marshy - If you had a 930 which way would you set your jumpers up?

 

Yes vested interest question, I'm looking to need some shortly and all the options are playing with my head.

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swept forward is also a hassle for furled code 0's, halyards, kites in socks etcs they can blow into the narrow gap between the diamond and the main stays - a simple cable-tie or lashing between the two will fix this for you :)

 

EE

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For a 930 i would probably be inclined to go directly inline.

 

3 reasons:

1) No big roach mains mean you can gybe the main with backstay on alright so dont need the jumpers to support it fore and aft (I Couldnt with Mercenary which was a problem)

 

2) The 930 rig is normally pretty spindly and the more inline it is the better the sideways support without it inducing twist or other silly things into the rig when the main is pressed up on it.

 

3) you dont need it raked forward to keep the top section stiff when you pull backstay on as you have runners? And the tube wouldnt be grunty enough to ever go without them and rely on the topmast alone so why try?

 

With keeping them inline you do keep the rig exactly the same fore and aft trim wise meaning your mainsail luff curve fits and the rig has the same characteristics through the ranges pre-bend wise. Having a big panel between the top of the rig and the forestay means get all the support you can = inline.

 

The SR's have a relatively short panel so raked aft makes small boat handling (Gybing with gennakers and kites) easier without backstays hitting large roach (I dont run topmast til about 15 knots of wind with big gear on)

 

Just my 2 Cents worth :-) and how we did it on Wild Oats and that worked well!

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Hi guys has anyone put up diamonds or whatever is needed so that you can run masthead gennakers on a 3/4 rig? Whats involved and what cost? Wanted for cruising with the odd passage race- boat is a Raven 31

 

Depending on where the boat is, get a rigger down to have a look, The Raven 31's have pretty grunty sections, and the forestay is fairly high up, along with wide spreaders. Depending on the angles you may be able to do what we did with the Piedys to run masthead gear.

We ran a set of stays from the deck, through the normal spreaders and right to the top of the rig. Meant not needing Jumpers which was easier. - Note this relies on having a reasonably wide spreader base and not too long a panel from the forestay and hounds, up to the top mast, and also not having spreaders rediculously far from the top either. It all depends on what angle the stays will hit the top of the rig and how grunty the tube is.

 

The only downfall on this is if you have overlapping headsails they hit the stays sometimes.

 

That must be 4 Cents now L-) Soon i can buy me a beer!

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