Iron Fastener Sickness

[Dan Hobson]

This boat is seventy years old. It's built by old traditional Swedish methods with two steam bent copper fastened frames and then a massive sawn oak frame fastened with iron boat nails. The planks are butted at the sawn frames. The pictures here show the oval black spots around fasteners that have wasted into the surrounding wood. And this is a call for suggestions about how they might be treated.

http://www.spidsgatter.com/images/boathome/boathome-Images/37.jpg

http://www.spidsgatter.com/images/boathome/boathome-Images/36.jpg

[Ian McColgin]

Pull a fastener or two and begin probing whether this is discoloration or rot. It looks more like the former, as the latter is more likely to occur more deeply in the wood and only make a black surface when really quite extensive. I abuse a 1/2" mortissing chisel for this. Any wood that gouges out easily must go.

There may be damage in the frames but again may not be all that bad.

If the former, I'd start pulling iron and replacing with black locust trennels. If you can rig a small diameter hole say just a hair larger than the nail head, you can bore a good way down, like through the plank and into the frame, facilitating removal. If done well, these are the starter holes for the trennels, which need to go more like 2/3 into the frame.

I'd CPES everything in the way of the fastenings before bopping the trennels in.

Depending on what you have, you may need to do some planking replacement. This need not be such a horror as traditionally. Get the cauling out of the way as you shred out the bad wood. You may well be able to scarf in shortish (under 2 or 3 feet long) dutchmen or even "hidabutt" them in, which is really more like a three piece scarf to give some bearing to pull with temporary through plank bolts, all that happening between frames.

G'luck

[sdowney717]

How thick are the planks?
I think I have read here that trunnels work well on thick planks such as 1.5 inch and thicker?
Could this boat simply be refastened with 316 ring shank nails leaving the old nails in place?

If the frames are nice and thick, there would be planty of wood to nail into.

http://www.mcfeeleys.com/subcat.asp?subcat=20.13.2

[ 01-02-2006, 12:21 PM: Message edited by: sdowney717 ]

[Chan]

I don't think you will find anyone who recomends SS below the waterline. SS needs oxygen to maintain it's stainlessness:)

[sdowney717]

Under 10 to 15 degrees centigrade, 316 is extremely resistant to crevice corrosion.

A lot of work boats here are fastened with 316 ring shanked. I have seen them pull planks and the nails looked sound, but I am sure some will say something else. Has anyone ever seen 316 nails or screws crevice corrode?