Once more with feeling - Chainplate Gusset location

[jmac]

Can someone provide a copy of the chainplate gusset location drawing that Kevin Mac drew. Jray posted one for me but half of the measurements are missing. Not jray's fault, looks like a file issue. I need to crosscheck the measurements against my tacked in gussets.
I'd be eternally grateful as it would get this painful job out of the way.
Thanks

[jray]

Sent you a PM, get back to me when you get a chance.

[Chad]

Here's a jpeg of that pdf, so the fonts can't drop out:

KevsChainplates.jpg

[cstay]

Realized this was my next step and didn't know how to position everything. You guys are awesome!

[Kevin]

For the record there are many ways to think about where everything should be. There is a lot that goes into rig design.

My c-tech rig is designed to be rigged with single spreaders and 2 shrouds per side. The chain plate location is forward of the spreader tip to induce some pre-bend by default. The hounds are also above the fore stay attachment point. The combination of pre-bend of the mast and the hounds above the fore stay relationship act to lock in the top of the mast. The goal is to support the tip with a masthead kite up and only 1 set of spreaders. The result is a lighter rig and simpler tuning. The cost is some risk in heavy conditions and less control than having a second spreader and another set of shrouds. Several other factors get involved while sailing. They include the amount of luff curve built into your main, cunningham and leach tension you maintain and about 20 other things. The viper rig is very similar to this setup, only the spinnaker sheave is between the masthead the hounds. The viper class lost a few rigs a few years ago and determined the primary difficulty was cause by little luff curve and not enough rig tension to keep everything in column. Did I mention that this stuff is complicated.

This drawing assumes a 30 degree spreader angle and induces prebend by putting the chain plate forward of the spread tip by using a 26 degree angle for the chain plate location. In my build, the bearing side of the gusset, the forward side, runs right into the corner between the hull and frame 110. A couple of strings can help a lot to position them correctly on your hull. And it's all relative to your mast step location which is controlled by a maximum measurement in the rules, not a fixed location.

Cheers, and good luck.

Kevin.

[slowpoke]

Chain plates? Oh, SH*T!!!!!!!!!

[Chad]

The primary shroud induces prebend by being deflected over the lower spreader. Chainplate location and spreader length are interchangeable means of altering the amount of shroud deflection. I still think the rig would be more efficient if the chainplate was aft of f110 along the 30 degree line, all the way out next to the shear.

[micah202]

...kevin ,,thanks for that description from C-tech for a onespreader set-up--it's very 'next-step' evolution-wise,
...definitely helpful for those robust ex-viper alloy spars,,usually available for $3-500

[slowpoke]

Chad, I'm thinking of using a diamond setup like you are,so the stress of bending the mast is taken up in the mast and the shroud, and not down into the boat itself. So the first set of uppers are being used to hold the mast up, the second set, led out to the spreaders and then down, reattaching to the mast near the boom. Could you help me out and tell me more about this kind of rig?
I'm ready to put my chainplates in, too, does anyone have any suggestions for size/shape?

[Chad]

More said, and more intelligently than I could put it, here:
http://www.uk-cherub.org/doku.php/tech/rigging

The reason I'm using the diamond setup for the uppers is to 1) make it adjustable with one string since they end up together and 2) to reduce mast step compression since my rig rotates, and more pressure is more friction and makes the rotation more difficult.

I'm not completely happy with my current setup at the moment- I'm getting about half the adjustment that I want. So give me some time to get it working right before going down the same road. Otherwise, the failsafe method is just a tang and turnbuckle (or two) on the mast near the base, or a micro-purchase (see the 12:1 setup on the Swift Solo site, using Harken micro blocks, that winds up as big as your thumb or so) and cleat.

There's a drawing of Kevin's chainplate lurking around here- basically a hunk of 1/8" stainless, wide enough to get at least three turnbuckles/holes across the top, and long enough to go through the deck and overlap the bulkhead below by several inches so you can get a handful of bolts through. Think about access, and make sure you can get the bolts in their holes later in the acute angled space.