18/03/2023 at 2:25 pm #24968WillParticipant
Hello, the mast step is rotten in my 1958 wooden boat, I need to make a replacement and am thinking about doing the mast step conversion while I am at it.
What kind of timber should I use for the new spine and mast step? It needs a short piece 20-25mm thick and another thicker piece 35-50mm thk.
It needs to be strong enough, very water resistant, durable for the next 65 years, not come from an endangered habitat, but I am not bothered about the weight!
I can source a 20mm oak plank from a builders merchants and laminate together for the thicker piece, or buy iroko or sapele online. I don’t know if ash or beech are up to it.
What would be recommended?
18/03/2023 at 2:56 pm #24971ArthurParticipant
I believe that most of the wood on my 1964 boat is mahogany. Oak is not a bad choice, but do try to source white oak, as red is more rot prone due to the cellular passages through the wood. White’s passages are encapsulated, red is like a giant straw.
18/03/2023 at 3:04 pm #24973Oliver ShawModerator
I have no doubt that other early GP14 afficionados will weigh in constructively here, but broadly I concur.
“Mahogany” was the original, but that is a broad term, covering around 400 different mahogany variants if my recollections of O Level Woodwork of 65 years ago are correct. In this case that was likely to be of a species that is now difficult to obtain.
The Robbins website, in their marine timbers section, will give you objective information on the various different marine woods available. Without looking it up, I would think that such oily woods as teak might also be worth considering.
The mast step conversion itself suggests combining with weight reduction by removing the inner slat from each of the side benches, and using that timber; but personally I would not wish to do that for reasons of seating comfort.
Whatever timber you use, it would be worth encapsulating in epoxy. I have very recently started using Smith’s CPES, and am pleased with it thus far, but my personal experience is too recent to form a long-term view. https://www.makewoodgood.co.uk/product/cpes-clear-penetrating-epoxy-sealer/?gclid=Cj0KCQjwwtWgBhDhARIsAEMcxeAF6UBaNMsCRD7sbb7URRsEKkKZ4a1vwE-yd_O6UrOYtPWraSKBefoaAkR_EALw_wcB
20/03/2023 at 12:07 pm #24974WillParticipant
Thanks both for your speedy replies!
I should have mentioned that the double side benches have previously been removed. The remaining single benches are laminated from contrasting stripes of white and red hardwood, they look great but possibly not strong enough for structural use.
Current thinking is to buy some iroko online. Still pondering if it is good idea to laminate 2x 20mm thicknesses to make up the thicker piece needed.
Thanks for the pointer to the penetrating epoxy, well worth some thought. Seems to be an epoxy that has been thinned with low-viscosity solvent. There are some strong views (both ways) on various boat and canoe building discussion sites!
Thanks again for the kind suggestions.
20/03/2023 at 12:19 pm #24975Oliver ShawModerator
Iroko is also a very highly respected boatbuilding timber.
Laminating from thinner pieces can be excellent practice, and especially if you cut the pieces out of a single strip and then turn them end for end before laminating. This reduces any tendency to warp. But I would not expect this to be necessary in this application.
Interesting the conflicting views on CPES. I presume that the low viscosity solvent is to enable it to penetrate effectively. Possibly choose CPES when penetration is needed, inclujding for priming before varnishing, but WEST (or equivalent) for strength when bonding is required.
An added point of information is that I get the impression that it is a wood-based rather than petroleum-based epoxy.
24/03/2023 at 6:13 pm #25002steve13003Participant
As noted above I always say that best source of wood for the modified mast step is to use the old thwarts, but if these have already been removed you need to look elsewhere. If you can find someone who is scrapping an old GP due to rot in the ply wood or keel they may be willing to sell you the thwarts or the center board case – these rarely rot and should be cheaper and more environmentally friendly than new timber. Looking on Ebay there are several adds selling old plywood pieces – would be worth contacting these sellers to ask if the solid timber parts are available.
I have carried out three mast step conversions using thwarts as a source, treating and fixing with SP Epoxy resins and fillers has always resulted in a strong and solid mast step
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