111. Rear Subdeck Glue-Down
After two months off the job it
is great to get back to it, but a simple task is a good way to ease
myself into thinking about the boat again. The rear subdeck panels are
all cut and shaped, and screwed down temporarily, so gluing them
presents no problem except that I want to keep the hull liner and the
hull itself free of epoxy drips, not to mention the steering mechanism!
All the parts needing protection can be masked off with tape and paper, but I have to be able then to get into the compartment to scrape away any runs. Not wanting to put any strain on my neck by squeezing into this small area, I elected to glue down one panel at a time, leaving plenty of access. Only the forward central panel will require a presence inside the compartment, and it is relatively small and easy to get to.
The parts adjacent to the epoxy lines are masked off.
All the parts needing protection can be masked off with tape and paper, but I have to be able then to get into the compartment to scrape away any runs. Not wanting to put any strain on my neck by squeezing into this small area, I elected to glue down one panel at a time, leaving plenty of access. Only the forward central panel will require a presence inside the compartment, and it is relatively small and easy to get to.
The parts adjacent to the epoxy lines are masked off.
The final refinement before
gluing the panel down is to run around its perimeter testing for spring
back where it is not firmly attached to the stringers, carlings or
bulkhead top frames. Quite a few extra screws are needed to augment the
few positioning ones, which have been sufficient up to now.
After
the epoxy is laid down there are still a few gaps which have to be
filled, so it is best to use a thickened mix which can be worked in
while it is going off. The join between the subdeck and the top
frame of bulkhead E, seen above, is a case in point. The bevelling on
the frame was no spot on, so a small gap showed between the front of
the frame and the subdeck. It will be hidden behind the
athwartships segment of the coaming, so it merely needs filling, not
disguising.
The rest of the glue up is
straight forward, although there is a fair bit of absorption of the
epoxy into the end grain of the ply, so the meeting lines of subdeck
segments need a few coats for adequate filling.
Showing epoxy absorption at the gaps.
While
the starboard segment is setting I take the opportunity to remove the
screws from the port and fill the holes with epoxy plugs. It is
probably totally unnecessary because the next deck layer will cover it
all anyway, but it stops the hole from filling up with dust from the
sanding of the joints, and that will possibly allow the next layer of
resin to flow properly.
The
joints themselves are a little uneven, because of an inconsistency in
ply thickness, but a bit of sanding and filling evens them up
sufficiently for the next skin to have a smooth bed to lie on.
Thickened epoxy being used for hole and step filling.
Thickened epoxy being used for hole and step filling.
Prior
to the final removal of screws and sanding the completed rear subdeck
looks like this:
Small
gaps continue to appear as the epoxy dries, but they can be filled at
leisure, as work now progresses to the fitting of the transverse member
of the coaming.
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112.
Scribing
and Shaping the Rear Coaming
It
is now possible, with the removal of the screws from the subdeck, to
scribe the camber of the deck onto the coaming, and to trim it to
shape. But before rushing into the cutting I want to consider the
dovetail joints which will connect this piece with the side pieces. The
athwartships piece will be glued to the bulkhead behind it along its
entire length below the deck level, and the side pieces will similarly
be fixed to the carlings, (screwed and glued) right up to the meeting
with the windscreen forward, and the transverse coaming astern. So the
only function of the dovetails will be to prevent the breakdown of the
joint along its section above the deck, which is a length of about 42
mm. There is no point in having the ultra-fine pins admired in
furniture making circles, as these are too delicate to withstand any
substantial stress, so equally spaced pins and tails seem to be
indicated.
Unfortunately, we are not dealing with right angles here, so dovetail jigs will not work. They have to be cut by hand. But that means that the dimensions can be devised to fit the situation, and not vice versa. The tails will be on the transverse member, so that the pins on the side pieces can slide backwards into position between them. Using 8º slopes for the tails, and given the 20 mm. thickness of the timbers, the width of the tails in their narrowest portion will be 5.62 mm. narrower than the widest. A comfortable arrangement then will be for a single tail surmounted by a half pin above and below it, and arranged along the width of the joint above deck level. This also conforms with furniture making convention, where the joints also end in half pins. And it will make for a relatively simple and strong joint. Below deck level, the transverse member can be cut back to accommodate an oversized "pin", as the side coaming is wider than the transverse, and will actually slip in under the latter to support it.
The final consideration is the thickness of the beading which will run around the deck-to-coaming join. If the half pin and dovetail are to be visually centred above the deck, then the tail will need to extend as far above the beading as the width of the half pin.
The solution is a dovetail 22 mm. wide, with a half pin 11 mm. wide above it and an elongated pin below it, leaving a visual joint with the pin/tail line centred in its width of 22 mm. (The 22 mm. is arrived at by subtracting the thickness of the subdeck (6 mm.) and the proper deck (4 mm.) and the beading (10 mm.) from the current extension of 42 mm. above the framework). Before the transverse member is cut to the shape of its scribed line, I cut the tail at both ends, and leave a little of the outboard end width slightly proud, so that it can be planed to final shape after the joint is secured.
Unfortunately, we are not dealing with right angles here, so dovetail jigs will not work. They have to be cut by hand. But that means that the dimensions can be devised to fit the situation, and not vice versa. The tails will be on the transverse member, so that the pins on the side pieces can slide backwards into position between them. Using 8º slopes for the tails, and given the 20 mm. thickness of the timbers, the width of the tails in their narrowest portion will be 5.62 mm. narrower than the widest. A comfortable arrangement then will be for a single tail surmounted by a half pin above and below it, and arranged along the width of the joint above deck level. This also conforms with furniture making convention, where the joints also end in half pins. And it will make for a relatively simple and strong joint. Below deck level, the transverse member can be cut back to accommodate an oversized "pin", as the side coaming is wider than the transverse, and will actually slip in under the latter to support it.
The final consideration is the thickness of the beading which will run around the deck-to-coaming join. If the half pin and dovetail are to be visually centred above the deck, then the tail will need to extend as far above the beading as the width of the half pin.
The solution is a dovetail 22 mm. wide, with a half pin 11 mm. wide above it and an elongated pin below it, leaving a visual joint with the pin/tail line centred in its width of 22 mm. (The 22 mm. is arrived at by subtracting the thickness of the subdeck (6 mm.) and the proper deck (4 mm.) and the beading (10 mm.) from the current extension of 42 mm. above the framework). Before the transverse member is cut to the shape of its scribed line, I cut the tail at both ends, and leave a little of the outboard end width slightly proud, so that it can be planed to final shape after the joint is secured.
The coaming is scribed to the deck camber.
A
piece of scrap, representing the proper deck and the beading, is held
against the stern of the coaming, and the lines are drawn.
The line across the top of the beading is the midpoint of the tail. The hatched area above it is where the pin from the
side coaming will come in.
From the side view, the pin can be seen to be sloping upwards to the fore, as the coaming will do. But the dovetail will be cut parallel to the waterline, not to the coaming timber. The tail will be visibly wider forward than sternward, and vice versa for the pin.
The angle of the tail appears to be different top to bottom, but that is because of the slope of the coaming. It is actually
parallel to the waterline.
The line across the top of the beading is the midpoint of the tail. The hatched area above it is where the pin from the
side coaming will come in.
From the side view, the pin can be seen to be sloping upwards to the fore, as the coaming will do. But the dovetail will be cut parallel to the waterline, not to the coaming timber. The tail will be visibly wider forward than sternward, and vice versa for the pin.
The angle of the tail appears to be different top to bottom, but that is because of the slope of the coaming. It is actually
parallel to the waterline.
Not
owning a bandsaw, I generally shape things roughly on the table saw
first, then finish them off with spokeshaves and block planes. The
coaming member is now given this treatment, and is brought down to
within a few millimetres of its final size on the starboard side. The
cut-out for the lower, elongated pin is made so that the side coaming
will fit neatly alongside both the rear coaming and the cut-out in the
rear seat back area.
The cut tails from front and rear.
Ready for the side pieces.
113.
Introducing the Side
Coaming From the rear the dovetail can
be seen to come down to deck level. It will be half obscured by the
decking and bead later.
Rear view.
Rear view.
With the entire rear coaming
roughly shaped, but before the dovetails are cut, it is time to secure
the position of the coaming before it is lost; there is very little
timber left in contact with the decking to locate the coaming
centrally, and once the tails are cut there will be none, so before
that the coaming is screwed onto the bulkhead, so that it can be
centred again after the tails are cut.
Only this small fragment of wood is now left to centre the coaming. It will be lost when
the tail is cut.
Four screws now hold the coaming onto the bulkhead behind. They are hidden behind the seat back.
Roughly shaped, before the tails are cut.
Only this small fragment of wood is now left to centre the coaming. It will be lost when
the tail is cut.
Four screws now hold the coaming onto the bulkhead behind. They are hidden behind the seat back.
Roughly shaped, before the tails are cut.
Finally,
the dovetails are cut and the coaming is screwed back into position
against the bulkhead, ready for the side pieces to be joined to it.
The cut tails from front and rear.
Ready for the side pieces.
The
coaming timbers are in need of considerable shaping, because, although
they travel in an almost straight line from the rear seat to the top of
the windscreen when viewed from their top edges, their bottom edges
will follow the curve of the carlings. They will also be positioned in
a diagonal lie vis a vis the waterline, as the height of the windscreen
is greater than the height of the rear seat. Finally, because of the
outward curve of the carlings, the coamings will have to bow to meet
them. The plan of attack then is this:
1. To locate the uncut timbers in approximate position with the rear coaming removed, so that the side ones can be slid back against bulkhead E as far as they can go, and then to scribe the angle of the bulkhead onto the rear end of the coaming.
2. To cut the rear end of the coaming to meet the bulkhead. This has to be done in width and in thickness.
3. To scribe the top of the carling onto the coaming, and to add a second line below it, half the width of the carling away from the first.
4. To drill screw holes through along the second line.
5. To screw the coaming to the carling, starting at the rear and moving forward.
6. To scribe the front of the windscreen onto the front end of the coaming, and to cut that in width and thickness.
7. To remove the coaming and add a third line below the screw line at the required width such that the coaming will be wide enough to cover the screws in the top of the lagging boards.
8. To cut the bottom edge of the coaming to the third line.
9. To cut a groove parallel to the bottom edge on the inside of the coaming, incorporating the screw holes and deep enough to house the cockbead which will cover the screw holes.
10. To dovetail the rear end of the coaming, and slide it home against the repositioned rear coaming.
With that done on both port and starboard, the rear coaming can be glued to bulkhead E, and the side coaming dovetails can be engaged into it. Final shaping can be done and the side coamings can be glued and screwed to the carlings and the windscreen, and the cockbeading timbers added. Cut down continuations of the coaming can be applied forward of the windscreen, below deck, to cover the lagging tops, and the job is finished.
1. To locate the uncut timbers in approximate position with the rear coaming removed, so that the side ones can be slid back against bulkhead E as far as they can go, and then to scribe the angle of the bulkhead onto the rear end of the coaming.
2. To cut the rear end of the coaming to meet the bulkhead. This has to be done in width and in thickness.
3. To scribe the top of the carling onto the coaming, and to add a second line below it, half the width of the carling away from the first.
4. To drill screw holes through along the second line.
5. To screw the coaming to the carling, starting at the rear and moving forward.
6. To scribe the front of the windscreen onto the front end of the coaming, and to cut that in width and thickness.
7. To remove the coaming and add a third line below the screw line at the required width such that the coaming will be wide enough to cover the screws in the top of the lagging boards.
8. To cut the bottom edge of the coaming to the third line.
9. To cut a groove parallel to the bottom edge on the inside of the coaming, incorporating the screw holes and deep enough to house the cockbead which will cover the screw holes.
10. To dovetail the rear end of the coaming, and slide it home against the repositioned rear coaming.
With that done on both port and starboard, the rear coaming can be glued to bulkhead E, and the side coaming dovetails can be engaged into it. Final shaping can be done and the side coamings can be glued and screwed to the carlings and the windscreen, and the cockbeading timbers added. Cut down continuations of the coaming can be applied forward of the windscreen, below deck, to cover the lagging tops, and the job is finished.
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