How to repair double diagonal hull planks: part I

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The thought of renewing double diagonal hull planks strikes fear into the heart of many an expert in wooden boat repair. But Mark Raynes has repaired 3,300 ft of it on his antique lifeboat the MANCHESTER AND SALFORD. In this blog he explains why there’s no need to panic and gives you his top tips for getting it right. In Part II, he’ll talk you through the process step by step.

I’ve spent about 15 years now working on my old lifeboat, the MANCHESTER AND SALFORD. One of the biggest jobs was replacing the double diagonal planking. She was built in 1924 and had been, let’s say, ‘let go’, so much of the hull was completely rotten, especially around the fixings where fresh water had got in.

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There really aren’t that many people who’ve done this kind of wooden boat repair, so I often get asked for advice. As a result, I’ve noticed that double diagonal has this curious effect on people’s psyche. Many seasoned boatbuilders have a fear of it and its apparent complexity. Maybe it’s the quantity of planking that needs to be replaced (there are often about five layers of it, after all) or the fact that you don’t do any caulking.

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Having done a lot of it, I really want to reassure people how straightforward it is. I think it’s an easier wooden boat repair than a carvel hull. I honestly believe it’s something that even an amateur could do.

Why it’s so easy

First of all, you need hardly any tools for the job. You can even buy the replacement timbers pre-cut and planed if you want to, so that you can get away with using just a drill, a hammer, a chisel and an electric screwdriver.

Secondly, it’s light work. You’re typically using planks that are half an inch think and about five inches wide and because they’re going in semi-vertically they’re not very long. So unlike carvel planking, you can do it by yourself. If you’re only replacing a piece of a plank? Well that’s even easier.

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Thirdly, using epoxy (especially WEST SYSTEM® epoxy) makes it really straightforward. Plus it’ll give you a result that’s so much stronger than the original build could ever have been.

Mark’s top tips

  1. Watch out for the moisture content. Make sure all the planks are nice and dry, otherwise as soon as you apply the epoxy it goes milky and a grease forms on the surface. This reduces the strength of the bond.
  2. In the same vein, start after 10am. You want to avoid the morning dew.
  3. Don’t remove too many planks at once. I’ve seen people take out as many as thirty planks at once, but this weakens the structural integrity of the hull and can cause distortion. Concentrate on one repair at a time.
  4. Keep the repair environment warm. The average boat shed is dark and therefore not that dry. We had the MANCHESTER AND SALFORD in a polytunnel, which was a really good environment – bone dry, it can’t rain on you and the temperature is usually five degrees higher than outside. The only drawback is, on a hot day, it’s really warm inside, so you have to use different mixers with your epoxy to slow down the cure time. But we rarely have this problem in the UK!

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Click here to learn Mark’s method for replacing double diagonal hull planks step by step.

To see more of the MANCHESTER AND SALFORD, visit Mark’s website.

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