Chine and bottom panels
We’ve made great progress this month, and as a result the hull skin is now complete, save for a lot of fairing – but that’s for another month! Ben Meakins reports
The first fit!
Our Secret 20 was pretty stiff and unyielding even before we fitted any plywood sides, but with the sides, chines and bottom panels in place, nothing moves in the slightest.
You may remember that last month, we installed the supporting structure for the bottom panels – stringers and bow cheek pieces – so this month our job list started with fairing everything back, installing extra supports where necessary, fine-tuning everything and installing the panels. That might not sound like much, but it meant lots of planing, scribing of panels, cutting out and a great deal of epoxy work.
The first job was to fair back the structure ready to accept the hull panels before installing chine panels, fairing these back and installing the bottom panels. The boat’s structure – both longitudinal and transverse frames, with stringers added to support the hull – forms a series of box compartments. Some of these will become lockers and others waterproof spaces.
TRIMMING BACK THE SIDE PANELS
We had stuck the side panels on before we turned the boat over, making sure the top edges were correctly aligned and planed to the level of the deck stringers. However, we’d left the lower edge oversized so that we could sight along it and ensure it made a smooth curve – much easier done with the boat upside down.
Boat duly turned, we could set to planing it off. This was complicated slightly in that the edge had to be planed in a bevel to allow the chine panels to sit flat upon the chine. We took the waste off with a Bosch electric planer, which while it appears to be a terrifying, noisy machine can be surprisingly delicate if set correctly. However, for this job we set it to maximum depth and took the angle off the side panels in this way. Half an hour and a lot of wood shavings later, the panels were planed to something near their final shape.
The next step was to plane off any
wobbles and fine-tune with a nice, long hand plane.
Using a Stanley No5 plane, we could run it along the bevelled chine stringers to plane down the edge of the plywood to match.
GluinG on extra supports at the bow
From the fourth frame aft, the hull has three faces – side, bottom and stringer – and each edge is well bonded. However, further forward, the bottom panels butt up to the side panels and must present a smooth curve. This meant that we needed to glue in some extra supports to give the panels some strength.
We cut notches in the frames to accept a piece of Douglas fir before fitting it with temporary screws. To ensure that we weren’t wasting material, or having to plane off huge amounts, we bent the timber around the frames to match the hull’s curve. To do this, we used temporary screws on two of the three frames, but used some rope and a Spanish windlass to pull the front edge in. This was remarkably effective, and once bent to shape we could epoxy it in using fillets.
With the moment where we attached the bottom panels fast approaching, we realised that it would be worth spending some time in sealing up areas that would become inaccessible or sealed. With this in mind we painted out lockers and floatation chambers with epoxy, adding fillets and filling voids in the construction.
sealinG inaccesible voids and Gaps
WEST SYSTEM had provided us with a tube of their new Six10 product, which they say ‘combines the strength, reliability and excellent physical properties of a two-part West System epoxy with point-and-shoot convenience.’ It comes ready-thickened, and as such it’s supplied in a sealant-type tube, with a special nozzle that mixes the two components.
Application is as simple as squeezing the trigger and pointing the nozzle. We used it to seal up a tricky area in the bow buoyancy tank, where a void existed between two timber components.
In consistency it’s like a sticky microfibre mix, but was easy to apply and didn’t run. We tried a few sample fillets, which came out well – but as it has less filler in than you’d usually use, you need to use more glue to achieve a good radius. It is sticky enough to form a useful fillet.
An electric planer made short work of trimming hull sides back to stringer level
The hull sides with the correct bevel planed in to match the stringers
We glued in extra timber supports for the bow panels, pulled into shape by a Spanish windlass
ABOVE The Six10 epoxy came in a cartridge with a mixer nozzle LEFT This was good for sealing hard-to-access voids and gaps BELOW Our test fillet proved good and strong when it had cured