Colchide’s rudder

10 thoughts on “Colchide’s rudder”

1. Here’s an update on Colchide’s rudder. It has been in our house for over a month, laying flat on kitchen tiles. I used a dehumidifier and reduced the main stock readings from 11% damp to 7%. In the area of the crack, readings have gone from 26% down to 7% too. The photo of the crack makes it look much worse than it actually was. I filled it in the house with cataloy filler and let it go off fully. On a 12 degree, sunny day last week, I finished off the rubbing down with 400 grit wet & dry and applied some (pre-heated) Hempel Underwater Primer, thinned 10% as directed. I am now slowly building up the 4 layers of this excellent primer, with rubbing down with 400 grit wet & dry between every coat. It now looks pretty darn good. I’ll keep you posted…………..

2. Richard
   Accoya sounds interesting. I had not really come across it before and it does look like a handy material.
   I found this video about how it is fabricated interesting. https://www.youtube.com/watch?v=_ZM2njWxgxM

   It looks very expensive – has your shipwright friend experience of using it ? The other aspect for the rudder blade is resistance to bending stresses set up underway. Is it is a strong in bending as the ply/mahogany laminated rudder you have at present?
   Nick

3. Uncle Bernard used Marglass only on the hull when he built Colchide from 1959 – 1960. The wooden blade rudder was a later modification in the 1970s. I have now completely stripped the rudder of paint and it is in my house drying off over Christmas. Initial damp readings were 11% all over and I’ll keep everyone informed if the damp readings reduce. I was chatting to a boatbuilder yesterday who suggested another way of solving this whole problem:

   MAKE ANOTHER RUDDER WITH ACCOYA

   Advantages of Accoya
   50 yr above ground/25 yr in-ground warranty against rot
   Dimensionally stable (no more swelling, twisting, bowing or warping)
   Extremely hard wood, similar to mahogany Janka rating
   Longer paint life (due to decreased wood movement)
   Accepts stains and varnish well
   Non-toxic, natural wood product
   FSC certified renewable resource

   Disadvantages of Accoya

   Requires stainless fasteners
   Prone to increased blowout during milling processes
   Limited availability
   Not locally sourceable

   Comments please.

   1. Richard,
      I used accoya for Mourne Goblins toe rails it was easy to machine (better than sapelle) Arnold Lavers keep in stock I believe, cost didn’t seen excessive. My friend who is a professional joiner now uses it when ever he makes windows due to its stability

      Dom

4. Thanks for your comments Mike.

5. I think this repair needs careful consideration!

   The delamination could lead to rudder failure under load. Which would be embarrassing if not dangerous.

   I would be cautious about sheathing wood with a polyester based resin. That will not adhere well to wood whatever anyone says. The only way to reliably sheath it would be with epoxy. West is my preferred epoxy system because I find it reliable and forgiving.

   The real issue here isn’t the sheathing – it is actually repairing the delamination. To do that you need to work out what is delaminating. It it the joint between the ply and the wood? Is it within the plywood? If it is the interface between the ply and the wood then perhaps the layers can be prized apart and the joints remade. If it is within the ply then the ply needs replacing.

   Whatever you do I would discourage just glueing the crack back together and sheathing it.

   1. Thank you for your thoughts Trevor. I have over 4 months before Colchide is going back into the water, so there is no rush. My current thinking is to investigate further the crack and possible delamination. I am going away from the sheathing idea. Nick also suggested drying the rudder inside the house over the winter for a couple of months, then applying a liquid which will not allow further water penetration, then several coats of primer/undercoat/topcoat.

6. Hi Richard
   Interesting! As Mike says it would be important to understand why the gaps have appeared – what is going on in the rudder.
   Sheathing is something that can be excellent, or not so..
   The danger is that if it is breached anywhere water and rot can build up behind the sheathing before there is any external visibility of problems.

   Personally I have always avoided sheathing but carefully done, on dry wood first treated with saturating resin it can be effective. And if you adopt a varnished finish over the sheathing any issues under the sheathing will be visible…..

   A useful guide by WEST on sheathing http://www.robbins.co.uk/Pdf%20Files/sheathing_guide.pdf
   And Gurit’s SP version of the same https://www.boatpaint.co.uk/acatalog/datasheets/sp/Sheathing%20Guide.pdf

   Given the rudders age yet apparently excellent condition after decades except for the gap on the trailing edge, why not just repair the gap and then paint for a few more decades use?

   Nick

   1. Thanks for your comments Nick.

7. I reckon the rudder needs attention. Has the crack penetrated deeper – splitting the layers, in which case repairs will be extensive. Noi experience of glass fibre repairs. Did Bernard use Marglass on the rudder too. Presume Marglass is compatible with glass fibre. Good luck. Mike

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