chainplates: round holes vs square holes

[benjiwoodboat]

talked to three non-sailor machinists this week about my cracked SS chainplates. All of them said the same thing: you'd be better off with round holes. both chainplates had cracks at the first bolt. what are the thoughts on this? carriage bolts are nice on the lines and humans, but does it make sense to drill round holes and use hex head bolts? are there solutions im not aware of for this?

http://lh4.ggpht.com/BenEriksen/SAt6...jpg?imgmax=640

[Brian Duff]

square holes suck

make em round

your buddies are spot on

use hex heads bolts with no threaded portion bearing shear load and lightly round the upper corners of the hex head, then fully polish the bolts.


chainplates are seldom installed where lines or humans can contact them, normally ones with carriage bolts are on the outside of the hull, ie Westsail 32

[benjiwoodboat]

right, glad you agree. I have all external chainplates on my BCC, so looking for a suitable solution for hex heads.

[Quickstep192]

Could you get the clean look you want and use round holes by using button head socket cap bolts?

Here's a link to a picture. I'm not necessarily advocating buying them at Amazon, they just had the best picture. I've seen them often at car shows. They're very popular for use in antique car restoration when a polished surface is desired.

http://www.amazon.com/Stainless-Stee.../dp/B00137FGGW

[benjiwoodboat]

Quickstep, that's an interesting concept. Any thoughts from some other more experienced folks about that idea? Anyone have any personal experience on a boat with that style head?

[Brian Duff]

Sure, that bolt is used on many hans christian- as long as its a structural head and has an unthreaded shank long enough for the chainplate and hull, your fine- check out mcmaster.com for fasteners and next day delivery on the east coast.