rigging plate hole to edge spacing vs pin size/plate thickness

[dkenny64]

if the rigging pine is 5/8, the plate is 1/4" thick how far should the pin
edge be from the plate edge?
I recently learned my upper shrouds had 2 different pin diameters. one 5/8( like the rest of the boat). the other was 7/16.. oops..I'm changing this..I might need to change the mounting plate too..
thoughts?


-dkenny64

[billknny]

You use the words "rigging plate" and "mounting plate" for what seem to be the same part? Do you actually mean a chain plate? I don't mean to be pedantic, but these things have specific names for a purpose, so we know exactly what you are talking about.

If we are talking about chain plates, I have always used the conservative rule that double the thickness of the metal from the edge is appropriate for a pin receiver. Be sure that fork that the pin attaches to fits.

I am not sure what the issue is with your pin size... can you be more specific? Are you changing the size of the rigging wire on your lowers? Are you doing that on purpose or was it a mistake?

[dkenny64]

this is not the chain plate. but a plate used to connect the rigging to the mast. in my case at the top of the mast. the plates are bolted thru the mast near the top.
the lower shrouds use a 'T' fitting.


fyi.. because of hurricane Dorian.. I'm having to move from internal/imbedded chain plates to external. the old plates were 3/8.. the new are 1/2" thick.


the wire size is the same..it seems somewhere in the life of the boat someone changed one side but not the other..one side was 7/16 the other was 5/8.. all other pins are 5/8 on 5/16 cable.


-dkenny64

[billknny]

Ah, ok, so you are talking about mast tangs.

I would assume that the original design spec for the pins was 7/16 and somebody increased the size to 5/8 for some reason, since it is easy to go up a size with a drill, but pretty hard to go down...

Assuming those tangs are stainless steel, then 1/2 inch from the edge for the pin hole should be good.

By the way, you can find these detail--and a lot more--in Brion Toss's excellent book, "The Rigger's Apprentice" If you are doing rigging modifications of the scope you describe and you have not studied this book you are making a serious mistake.

[dkenny64]

1/2..oops there is only 3/8 left.. the rest of the pins are 5/8..ie the chainplate pins..why would the top be 7/16" ?


I just talked with my brother's father-in-law who used to design these boat..he think there should be more metal between the edge of the pin and the edge of the tang.. seems like I need to get new tangs made


thanks

[sailcrazy]

FWIW, when we re-rigged in Phuket a few years ago, all our factory-made chainplates showed signs of elongation at the pin holes (oblong holes). And we found out that some of the 5/8" holes had only 1/2" pins and a few had 3'8" pins(point load?), while some had 5/8" pins in the 5/8" holes. We re-did all the chainplates with 316 S/S, redesigned to have at least the pin diameter on each side of the pin and NLT1.5 x pin diameter between the pin and the chainplate end. And we used all new 5/8" pins in every hole! According to the rigger, that was the minn metal around a pin.....and so far, now some 7 years and 2 oceans later, we've found no issues at all with our rig.

[dkenny64]

wow..
well after 30 some years the chainplates (3/8 thick) are fine. the pins are 5/8 and 5/8 from the holes..new plates are 1/2" and 5/8" pins are 5/8" from the edge..should be good.


I going to fix the top end tangs that are 1/4" plate with the 5/8" pin only 3/8" from the edge..I checked today.. there is enough room for another 1/2" of metal from the hole edge to the plate edge..and I'm going to up the 1/4" plate to 3/8" plate..why? I'm think the cable should be the weak point.. not the other parts.. the original chainplates were 3/8".


-dkenny