Riveting with copper rod

[lesweeks]

I need to replace the sheer strakes which are riveted with copper bar of about 6mm (1/4"). I'm guessing that the process is essentially the same as the nails and roves for the rest of the planking except that they only have to go through the plank and a rib and have pre-formed countersunk heads.
Riveting the inside over a rove or washer I'm OK with, but how do I form the bar on the outside into a countersunk hole in the strake so that the fixing is flush. Is it formed in some way before introducing into the hole? If so, how is it done?

 

[stephenh]

In a boatyard I worked in years ago we had a 1/2" steel plate with various countersunk holes which was the former. I think you need to make / borrow one.

Copper bar is usually sold in a 'half hard' state. Quickly heat 1/2" of one end to cherry red and plunge into water. This softens the copper ( it works the other way round from iron).
With the soft end held vertically on a flat part of the above former plate hit the other end of the bar with a heavy hammer and the soft part will swell up. ( in blacksmiths parlance - 'upsetting' or 'jumping up')
When of a sufficient size drop it into the appropriate former hole (it won't drop through because of the bulb) and shape the end to the countersunk former with a ball pein hammer.
Job done...
It may well be that you are timid with your hammer strokes in which case you will work harden the copper and have to de-temper it again with heat and water as above.
I hope the above is clear - not very well put over.

Good luck

 

[lesweeks]

No, that's very clearly put, thanks. I sort of guessed that it would be something like that. As I'm a Technology teacher, all your terminology is familiar to me and I've done that sort of thing in the past but mainly with steels. I'm not adverse to a bit of 'upsetting'! I've got a suitable bit of plate, so I'll get on with making the former.
Thanks again.

 

[Peterduck]

I've always used a plumber's pipe-flaring tool for forming the heads of copper rivets or bolts. If you run a saw cut through the diameter of the hole, the resultant gap of 1mm will enable you to grip the rod better if you put the plate in a vice. As Stephen has said, be bold with your hammer initally, and once you have the general shape right, you can refine it to a nice dome with gentler taps.
Peter.

 

[old_salt]

If I may add my 2p.
When you have made your forming tool case harden it it will last longer.
I made mine from a piece of 1ins sq x 2ins drilled it though then counter sunk it at both ends so I effectively had two forming tools and split it down one side then case hardened it.
Cheers David.

 

[dcjones]

HI I am a boat builder and we use a 5/8 old bolt cut of about 1 inch below the head and drilled right threw the size of the rod and countersunk to the size of the head required, Then cut a slot up from the small end of the bolt, Place the rod in the hole with about 5/16 above the bolt head and frimley cramp in the vise, Hamer over until flush.
Regards David

 

[lesweeks]

Thanks Fellas,
This is all very useful, practical, advice; now for the sheer strake, wish me luck!