Forums: Whisstock Designs: cutting lists? New Topic Post Reply
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Posted: Jun 28th, 2014 at 10:26   |   Subject: cutting lists?
Before I order a plan, I'm trying to calculate rough total build cost. Do Whisstock include a cutting list for solid timber, or simply a list of plywood sheets? Can't find any indication on their web pages.
Posted: Jul 4th, 2014 at 11:22   |   Subject: Cutting lists - 1 & 2
Oh – it's not so bad, producing cutting lists – I'm just somewhat delinquent in that respect.

The time to do it is when one is producing the weight estimate because at that point every bit of timber (and everything else) that goes into the construction of the boat has to have its weight and centre of gravity calculated, so as to get at the weight and centre of gravity of the vessel and to be able to complete the design of the ballast keel, which is the final balancing factor in the design, and one of the few things that one has real control over.

Design 165 is not entirely finished yet and so a cutting list at the moment would be incomplete and inaccurate. And there are two build options with the boat (ply or laminated) and two versions (saloon and doghouse) and at least two rigs – so there is a lot to consider.

With solid timber I tend to stick to regular sizes – 18mm, 20mm, 25mm, 30mm, 40mm, 50mm thickness. 18mm, 20mm and 25mm are the most used. The cockpit has some 40 x 50 bearers.

You would need to saw boards at about 8mm thicker than your finished thickness. You need to air dry for at least a year with the boards in stick – be careful what timber you use for sticks else they will stain the boards with a stripe across in way of each stick. This will get you down to about 16% moisture content (MC), which is good for traditional yacht work.

16% MC is however too wet for structural wood/epoxy construction – for that you need the timber down to 12% moisture content. And that usually means kiln drying.

You can dry air-dried timber still further by storing in a warm dry workshop over a period of time and very little shrinkage will occur from 16% to 12%. Running a de-humidifier in the workshop will also help. For this purpose, it would be good to have the boards planed down nearly to finished size as you suggest. Test with a decent moisture meter to see where you are with the moisture content.

The structures of the boat are designed around using timber at 12% MC maximum, bonded with epoxy. However, for the main longitudinal laminations (the backbone, keel and deadwoods), timber at 16% would be strong enough.

For higher MC timber (12% - 16%) you should laminate using resorcinol resin glue. There should not be more that 3% MC variance in the timber components being bonded, and no timber should be more than 16%. You need closer joints and greater clamping pressure for resorcinols than for epoxies; temperature requirements are about the same – an absolute minimum of 10º (50º F), but practically speaking, a minimum of 15º (60ºF).

For other longitudinal items (shelves, carlings etc.) which are not very big section (typically 18 x 50, 18 x 35, 20 x 30), a secondary drying indoors as above, should get the timber down to 12% OK.

The thickest timber component in the boat is the aft deadwood, which is 60mm finished – but this can be built up from horizontal layers of thinner timber – say 25mm or 30mm – 60mm wide. In the ply version, this is all part of the ply-sandwich backbone, which is made from vertical layers of 12mm ply.

You can get a good handle on the quantities and sizes of solid timber required by looking at the study plans – scroll to near the bottom of the 165 web page and click the link to the study plans. Plans 165_003_001 and 165_003_002 give you profile and plan views of the longitudinal structures. These can be printed out to scale on either 11" x 17" or A3 paper, so you can scale reasonably accurately off them. Most print shops will do this quite cheaply.

Most of the transverse structures (frames, floors etc) are either laminates or ply; most of the other structures (decks, coachroof coamings, coachroof tops, cockpit etc) are ply.

The interior furniture is ply with solid framing and trim – and here you don't have to use kiln dried timber – 16% MC is OK.

Hope this helps. My apologies for the delay in replying to you.