OK, so the diesel tanks are progressing well - the plywood arrived on Tuesday and the fibreglass stuff on Wednesday. I cut out the panels for both tanks on Tuesday afternoon, and fitted them together on Wednesday morning. In the afternoon I put thickened resin fillets in all the inside corners.This is to prevent the formation of voids in the fibreglass cladding. I had other things to see to on Thursday, but today got most of the insides of both tanks clad with chopped strand matting; there's one panel on each still to do and hopefully I shall get that done tomorrow, and make a start on the outside.
With the strengthening provided by the interior clading (the panels are only nailed together) I intend to radius all the corners and then clad the outside in woven rovings so that the plywood will be completely protected. I only bought cheap stuff with that in mind. I'm using 10mm.
As of this morning the weather forecast for next week looked a lot better so I've made provisional arrangements for craning out that afternoon, but the updated forecast this evening didn't look so good so we'll have to wait and see.

Well, things have moved on a bit since my last piece.

Firstly, I have got an estimate for the new tanks and it’s a bit more than I had hoped to pay,  particularly as I now have to find the money for an exhaust manifold as well. About £150 per tank plus about £300 for the materials. A new manifold would cost about £400.

 However, a web search and a couple of emails today have located a good second hand manifold for £100 + vat and carriage so that’s a big step forward.

 Also, since I’m happy making things out of plywood I’ve been investigating the possibility of using that for the tanks. I think 10mm ply will do, it will be lined with fibreglass with a finish of  isophthalic topcoat. I’ve taken advice from a reliable supplier (CFS Fibreglass Supplies) and they’ve said that that will be OK and that I should put on a couple of layers of 450g/m2 cloth using ordinary general purpose polyester resin and the topcoat to seal it. That way I can make all four tanks (two diesel and two water) for less than the cost of one in stainless steel. Some time ago I chatted about this possibility with a friend of mine who built his own boat a few years ago and made his tanks that way and they have not given any trouble so that is what I shall do.

An added advantage of making the tanks myself is that I can fiddle around and make them just the right size and shape for optimum use of the space. This will take more time, but it's my time, and wont really affect the amount of material very much. I'll probably make the fuel tanks first as I can then use them to store what's in the existing tanks while I take them out, and then when I've got good access to the space I can measure up for the water tanks.

I’ve already said that I will have the manifold so it just remains to place an order for the resins and get four sheets of exterior quality plywood delivered to the island. (And then wait for some quiet weather to get ‘Petra’ craned out!)