Like Joe I've been raised around builders, so I tend to default to plank on frame which most members should be familiar with. My hulls are typically 30-40 inches long and rounded bilges (as opposed to hard chine).
For these I use:
- keels - 6mm ply
- frames - 4 mms lite ply
- stem and sterm - balsa blocks sanded to shape
- stringers - 6 x 2 mm of whatevers around at the time
- planks - 1 or 2 layers of 1.2mm birch birch ply cut to strips as needed.
Birch is a hard ply to work - literally - so I tend to use a bandsaw with a fine toothed blade to work it. the up-side is that the stuff we get here is very straightgrained, even ply with no surface flaws. Downside is that it can have a razor edge so inevitably there's a bit of blood spilled at some stage.
That all makes for a light but strong hull, which I waterproof and strengthen with Epiglass 90 and 3/4 ounce fibreglass cloth. Epiglass 90 is a two-pack epoxy resin system that was formulated specifically for the marine industry - sheathing timber boats using either synthetic or fibreglass cloths - so is purpose built for what we do, just on a larger scale. I think it was developed in New Zealand in the 1950s but should be available world-wide from most any serious hardwarehouse or ship's chandlery.
I dilute the two pot mix a little with resin thinners then paint it around the inside - I figure diluting helps the hull timbers soak up the resin.
On the outside I paint on a little diluted resin, lay up the cloth then squeegee on some full strength resin using Joe's favourite aplicator - a credit card - best use for 'em!
The first few hulls I did were a bit rough - so on goes a bit of auto body filler and then plenty of sanding back. Over time my fibreglassing has improved some, so the filling and sanding work has reduced considerably - thank goodness.
Having said all of this I'm interested in trying the option of carving hulls from extruded foam, glassing the plug and then melting out the plug with a bit of thinners or petrol (outside of course - as the resulting goo is a close approximation to napalm!).
I'm interested in double diagonal planking over a wooden plug as well - would help do away with a lot of the need for internal strengthening such as frames, etc., which means the hull has more space inside for batteries, motors, servos, rx, etc. One of my old modelling mentors gave me a few tips on this so definately something I'd like to try. I've been thinking that it would be the perfect approach for a freestyle Windermere-type steam side-paddle launch.
As for decking - a 2-3mm ply subdeck then individually planked over. Reliant was the first deck I did with margin planks and joggled decking as well - not quite as hard as I had anticipated, and the result certainly looks good for the effort.
I also did something a little different with her decks - instead of laying the decks directly on the sub-deck I started by making a former with the same deck camber as Reliant. Then cut out 0.4mm birch ply shapes (thin as paper and cuts with sharp scissors) to suit the finished deck shape, laid those up on the former, and planked onto those. Once planked I sanded everything back and laid the decks onto the hull. A tad more construction than working directly on the subdeck, and a bit of careful measuring to ensure that deck openings were accurately located, but very very easy to work on as there were no bulwarks, coamings, etc. in the way.
Spring, eh, Joe? We're getting the first few days of Autumn down here - beautiful warm days, cool evenings - just a glorious time of year!
Tony
Akl, NZ
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