Rig Question
 

The question is relevant to a 35' steel multichined cruising yacht, 7ton, dual spreader (continuous wire) rig, about 12mt high off the deck. Cutter rig with inner forestay.

The current wires are all 5/16 (8mm) with the only exceptions being the uppers x 2 and the innerforestay x 1, that are 1/4" (6.4mm). There are 4 x lowers (2 fore & 2 aft).

The cap and upper shrouds on each side join at the bottom on a bridel plate that is pinned to the chainplate.

The question/s is this:

In a rig like this (designed 25 years ago) as we re-rig this now, would all these wires be kept the same or are there thought out there that some take a bigger load than others and so the rig dimensions can be tuned a bit by reducing some and increasing others ?

Do the lowers x 4 need to be as big a wire as the cap shrouds ?

Does the forestay or backstay take a bigger load ? Roler furler on forestay.

Some comments would be appreciated, or descriptions of similar rigs.

Changes
 

Hello,
Distribution of load among the stays is what drives rigging sizes. It sounds like your rig was spec'd (I won't say designed) when it wasn't as clear how contemporary rigs distribute loads. What you have is more suited to gaff and early Bermudian, unless of course you have a fractional rig. Lots of variables, so I would start with a look at the relevant material in the "Apprentice", or Larsson & Eliasson. The first question of rigging is: What is the load?
Fair leads,
Brion Toss

Thanks Brion

I realsie now that getting a copy of your book would have been a wise move. The re-rigging has been more involved that first thought, but that is from the perspective of ignorance rather than experience. :rolleyes:

I have taken the advice and ordered a copy of the "Riggers Apprentice".

The rig is masthead, not fractional.

The puzzel for my thinking is that triangular plate that the caps and uppers attach to, then it in turn has a pin attaching it to a chainplate. With one heavy wire, the cap at 5/16, it seems strange to have the upper sharing it when it is only 1/4". I had a look around tha bay where we moor and there is not another rig like it.

I have put some photos on this page that show the "bridle plate" for want of accurate riggers jargon. http://adams35.multiply.com/photos/album/2

Dear Ribbony,

The link plate scenario you mention is a common mistake that is perpetrated on an unsuspecting owner/builder when the mast maker is asked for a (cheaper than discontinuous) twin spreader continuous rig and the builder forgets to read the plans, which should provide the right number of chainplates for either rig, or enquire of the mast maker just how many chainplates are needed.

I have seen it often.

Picture this:-
The proud owner of, usually a self built, hard chine, steel boat arrives at the marina, (on a Friday at 3 p.m.) with his kit-form mast and rigging already loosly assembled and laid on the cabin top of the aforesaid five-year-project-yacht..

"Just step this mast and swage the lower ends for me will you?, I have got people coming for the launching tommorow and we are off to New Zealand on Wednesday!"

After a quick look at the mast and boat the question arrises" How many chainplates did you fit, you are one short each side, has someone stolen them?"

"What do you mean? cries the owner, I only built what was on the plans. I did move the starboard aft lower chainplate in a couple of feet and the compression post forward a foot so I could fit the bigger shower room my wife wanted but that wont be a problem will it?

After many heart rending conversations, delays to the owner's plans, and also after having to dissasemble and correctly re-assemble the rig, the rigger is faced (against his better judgement, but in the interests of trying to help this poor, uninformed owner/builder get some kind of rig in his boat before his family disown him), with suggesting, purely as a stop-gap solution, the sort of bodge you have ended up with, with the caveat that it should be rectified with the proper number of chainplates and the correct length stays at the earliest convenience.

Of course this rectification never comes to pass and the problem travels down the life of the boat through the ownership path until someone like yourself asks the right questions.

It is a horrible compromise. Your options are:-

1. Leave it in place. "Well, it has not caused any trouble yet" (not advised). or,

2. Install the correct number and size of new chainplates.

Somewhat in it's favour, the pin in the chainplate looks to be the larger of the three and the plates seem to be substantial.

That said, The chainplate looks small for the loads and the whole thing will rock backwards and forwards with the fluctuating loads on the two shrouds and tuning will be more involved, with the tension on one shroud directly influencing the other.

Whenever I am asked an opinion about someones chainplates I ask this question of the owner

"Would you be happy to lift your boat out of the water using only your chainplates?'
That gets them scurrying about and stabbing at a calculator, I can tell you!

If you have the heart for the job and a welder handy, get rid of the things!

Regards,
Joe Henderson.

Ah
 

Hi again,
Classic. Imagine how that link will seesaw, due to unequal loading of the two wires. Kind of throws tune out the door. And note that the lower pin is the same size as the pin for the larger wire. And that toggling is effectively disabled. And that there is a risk of shearing assorted cotters. Great bad example! Clearly, you and your boat deserve better.
Fair leads,
Brion Toss

:eek: Ouch !

A "pandoras" bridle plate !

Joe - that was a great tale. Some insight of what riggers have to contend with. A good laugh, even though it is close to home. Our vessel has no known history whatsoever, other than neglect !

Ummmmh - I can see that if we knew this 12mths ago I could have welded extra chainplates in with no real drama. The chainplates are heavy SS bar that is welded through the deck plating and extends down to the first chine bar inside. My wife last week just finished putting in all the teak linings (a big job, all plugged screws). The 3mth boat project that has taken 3 years has been a challenge for the both of us and now that we have some light at the end of the tunnel, I won't throw a spanner in, just yet (the political reality).

What to do - I guess that we should complete our re-rigging, as is. I have already cut the wire for the caps and the ends are sitting on ready for swaging today. I have not cut the 1/4" upper shrouds as yet. In the end we will have to waste those shouds if we put new chainplates in, but thats Ok in the long run if we get a better rig out of it all. After all we do want something we can depend on. I want to be able to snooze happily in rough weather (off watch) without my mind churning every known weakness in the boat.

The chainplate pin on the bottom of the link is 5/8", the pins in the turnbuckle toggles are 1/2".

After Joe's account I can visualise the scenario of the chainplates set up for a single spreader spar then a dual spreader being mounted. I think the rig is original, it is an old "sparcraft" mast.

I doubt there is much we can do short term other than replace all the pins and dye penetrene test the chainplate as we re-rigg. The chainplate is 9mm thick SS with 16.7mm of surface remaining between the pin hole and the edge of the chainplate.