Bronze or A4 Stainless screws for Iroko Rudder

[winsbury]

I'm finally re-assembling the various bits of wood, steel and aluminium bronze that make up the rudder and skeg on my Pegasus 700 after the extremely difficult process of installing new rudder bushes. The original (large) screws that held the three main bits of iroko wood together were bronze. The screws are all buried in deep countersinks in the wood and will be covered with layers of filler, epoxy and antfoul. Since steel is a fraction of the price of getting hold of new bronze screws ( the old ones are beyond rescue ) what, if anything, is the argument for / against bronze versus steel screws in this situation ?

 

[vyv_cox]

Neither of your options. Use silicon bronze, relatively cheap but with excellent corrosion resistance. See http://www.classicmarine.co.uk/articles/metals.htm

 

[winsbury]

Brilliant !... the info on that link about stainless below the waterline answers it perfectly, thanks. Off to source some Silicon bronze screws now...

 

[tillergirl]

Try Anglia Stainless http://angliastainless-stanton.co.uk/ for your silicon bronze screws.

To commune with a fellow rudder repairer see page 18 of this http://www.eastcoastsailing.co.uk/ECS07-low.pdf

 

[winsbury]

That was a big rudder - mine is tiny by comparison but the engineering is much more complex - the three pieces of Iroko fit around a 1 inch x 1.5m welded steel tiller pin which has teflon thrust bearings sat on a cast aluminum-bronze skeg which is in turn bolted to the hull. The is only one sequence the lot can be taken apart / assembled without a) damaging anything and b) not requiring the boat to be lifted 6 feet off the ground to insert the pin up the rudder tube. Theres a half-pipe section of iroko that wraps around the steel pin and is hidden for the most part by the skeg, the old one had split and worn the old bearings away entirely which in turn had scraped 5mm of the skeg bearing seat away in an uneven dome shape. The skeg had to be taken to a local engineering firm and they made a special tool to flatten the bearing bed ( this was cheaper than the £350 to replace the skeg ) , they also turned up some new oversize ptfe bearings to take up the slack and re-welded the top of the ridder tube that someone in the distant past had hacked off in a failed attempt to do this exact job I suspect. The Iroko was ordered and I had to send to USA to get the very larger router bits required to shape the it correctly. Materials costs so far : £30, Tools £175, Engineering £100. The screws, epoxy etc will add some to the materials bill but goodness only knows what this would have cost if I'd had the boatyard do it. Theres some photos of the skeg and rudder before the work started on my other thread about repairing the Pegasus 700 if you're interested, I'll put some after shots up when its completed.

 

[tillergirl]

Umm yes, does sound complicated. Yes manhandling mine was an issue - curious centre of gravity which caused it to want to spin if you lifted it the wrong way!

PM sent.

 

[VicS]

b) not requiring the boat to be lifted 6 feet off the ground to insert the pin up the rudder tube

The usual way is to dig a 6 feet deep hole under the boat.

Boat yards are used to this and are quite happy for owners to dig big holes all over the place.

 

[winsbury]

Its at my midlands workplace on tarmac so digging a hole is not an option. I did consider lifting it with our forklift and cradle but 1.5 tonnes is well over the limit. So I plan to reassemble it on the boat, the reverse of dismantling ; its not ideal but the only way I personally have available.