The old slipper launches had very simple instrumentation, comprising merely a few gauges and an ignition switch. Presumably there was a switch somewhere for the navigation lights and spotlight, but it is not obvious from the pictures. The bilge pump was manual, and there would have been no refrigeration or radio. There was certainly nothing like the unsightly modern distribution panels. The Freebody reproduction launches of today have a marvellous simple elegance of dash board arrangement which it would be nice to emulate.
With the electric motor the only absolutely
necessary gauges will be an ammeter and a voltmeter, although a strong
case can be made for a battery condition gauge. Since there will be two
systems, a domestic and a motor, there should be two sets of gauges,
but a battery condition gauge will not be necessary for the domestic
system. So, you end up with five gauges, similar to the arrangement
shown left.A key start ignition will be a pleasant retro touch, and the switches could be for cabin lighting and bilge pump, both of which could bypass the distribution panel.
My adaptation of the Freebody scheme will be to have an opening door below the instrument panel, which will reveal the modern electrics and fuses. So, a sloping board will come away from the dash bulkhead, like the one left, but will need to slope back in to meet the bulkhead at cabin sole level, because the lifting segment of the sole which reveals the shaft seal has to be immediately accessible. What I will not have is the gear stick. My motor controller can be mounted at the side as seen in the shot below, right.
The small chrome control on the extreme left
of the picture is, I believe, a throttle lever. With the general layout of the dash settled I can give some more detailed consideration to the electrical connections. The gauges and buttons are all very well, but the guts of the system will be the out of sight switch panel. With such a simple boat as a slipper launch I cannot see any advantage in having innumerable circuit breakers rather than fuses in the system. The likelihood of a navigation light or some other device shorting is low, given the care I am taking with conduits etc., so a simple fuse box will be an economical alternative to the more expensive distribution panels with breakers. The devices which need a circuit and their typical current requirements are:
- navigation
lights 5 amps total
- spotlight
10
amps
- cockpit
lights 3.5 amps
- horn
1.5
amps
- bilge
pump
2.5
amps
- bilge
blower 2.5
amps
- refrigerator
4
amps
- stereo
1
amp
The old ugly, and new inconvenient switch panels.
The question of what amperage to allow in the fuses is crucial. The function of the first fuses (or breakers) in the circuit is not to protect the appliance at the end of the circuit, but rather the wire leading to it. If the wire is rated for an amperage close to the current actually drawn by the appliance, and there is a short, then the wire can rapidly overheat and start a fire, in theory. So the fuse should blow well before the wire's tolerance is reached. Clearly, the fuse then should be rated at the amperage of the wire, not the device, although the wire must be rated at least as high as the device. Some circuits will then have a second protective fuse rated for the device further down the circuit
In Ariadne's case, the wire is rated at 15 amps (and I calculate that it would tolerate 20 amps), whereas most of the devices will only draw a maximum of 5 amps, so 10 amp fuses for the wire would be perfectly acceptable, with perhaps a second 5 amp fuse down the line.
Now, it is quite possible to go totally over the top with protection here. Many books would recommend breakers on each battery box, a main breaker for the domestic circuit, plus a sub-main breaker for the distribution panel, and individual breakers or fuses for each downstream circuit after the panel. (The main breaker protects the appliances which bypass the distribution panel, as well as the panel itself). I feel that a simple electrical system such as I am building does not need to be so elaborate. For example, if say the bilge pump bypasses the distribution panel, and is protected by its own in-line fuse, what is the point of having a main breaker as well as a sub-main breaker when the only other bypassing devices might be cabin lights?
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66. The Permanent Windscreen
The windscreen mock-up, which
was done in September '07 allowed me to make certain of all the angles
to be cut on the real thing. Now, with some 1 inch Fijian mahogany to
work with I am starting by cutting the central post with an oversized
32 mm. thick
piece, which is just enough to produce a 19 mm. edge after the required
angles are cut on it. The "glass" will be 6 mm. thick, so the
frame members containing it should be at least 18 mm. Since the coaming
is going to be 19 mm. that seems like a good thickness for the screen
frame too. But that only means that the lateral and bottom frame pieces
will be 19 mm. The central post, because of its vertex, has to be
thicker at 32 mm.
The angles of the dummy centre post are first drawn onto the mahogany piece which will form the permanent member, and then they are reproduced on the table saw. The width of the central post is not critical, but the thickness of its side is, because it must match the thickness of the bottom frame pieces. So, the cuts along the side can be adjusted, taking shavings off until their thickness is just right.
The newly cut centre post (left) and its cradle (right).
The coaming can be represented by a piece of scrap cut 19 mm. thick, and attached to the carling near the point where the bottom screen frame meets it. That allows the off-vertical angle of the lateral screen member to be taken off the scrap, and that, in turn, gives the angle of cut across the width of the outer end of the bottom frame. The lateral frame pieces are rebated to accept the coaming, and then fixed to the bottom frame by mortice and tenon.
Mortice and tenon also fix the bottom frame to the central post, but only after the post has been attached to the stubby deck stringers which support it. That is ultimately achieved by gluing the floating tenon into the bottom of the post and screwing and gluing it between the stringers, but for now it sits there held by friction.
When the post is fixed, the bottom frames are added, and they should line up exactly with the bottom of the coaming. If they do, the forward deck line is scribed onto them for shaping, and they are curved on their upper edges to parallel that line. They are then ready for gluing. If there is any discrepancy in the height of the bottom frames vis a vis the coaming, it is better to have them a little deep rather than shallow. Too deep can be accommodated by widening the coaming, but too shallow cannot, as it will reveal the carling underneath if the coaming is reduced in width.
Finally the lateral frame members can be put in. If there is a tight fit between them and the mock coaming it may be sufficient pressure for clamping, but, if not, some wedged clamps will have to be devised.
The lateral frames are added. All vertical members are left overlength.
The angles of the dummy centre post are first drawn onto the mahogany piece which will form the permanent member, and then they are reproduced on the table saw. The width of the central post is not critical, but the thickness of its side is, because it must match the thickness of the bottom frame pieces. So, the cuts along the side can be adjusted, taking shavings off until their thickness is just right.
The newly cut centre post (left) and its cradle (right).
Once the central post is cut it
is necessary to build a cradle for it to hold it down so that a groove
can be morticed
into it, dead centre, for its joint with the support peg. It is a good
idea to leave the groove shallow enough to allow screws to be
driven into the peg later from the rear of the post, and for them to be
covered by plugs. But you also have to allow enough meat for the peg to
gain a good gluing surface. Epoxy here will be an absolute necessity.
The centre post peg slots in between the short stringers.
The central post is left long until after the other parts of the frame are fitted. The finial on top of the post will be shaped after
the grooves for the windscreen are cut.
In order to establish the
width of the bottom frame, a temporary deck is clamped in place over
the stringers at the level of the windscreen, and a wire is run from
the central post to the carling. At its furthest point from the deck it
is 20 mm. away, so 20 mm. is added to the 30 mm. I reckon will be
necessary over the top of the stringers to allow for the deck (10mm.),
fillet and reveal (20 mm.). That leaves a total width of 140 mm.
required, and a glass retaining groove of about 30 mm. will have to be
cut to accommodate the eventual curve in the bottom frame.
It is also a good idea to cut the glass retaining grooves in all frame pieces at the same time, with the same setting on the saw fence, so the next job is to dimension the bottom and side frame pieces. That needs the coaming to make an appearance.
The centre post peg slots in between the short stringers.
The central post is left long until after the other parts of the frame are fitted. The finial on top of the post will be shaped after
the grooves for the windscreen are cut.
The wire shows the
extra width needed.
It is also a good idea to cut the glass retaining grooves in all frame pieces at the same time, with the same setting on the saw fence, so the next job is to dimension the bottom and side frame pieces. That needs the coaming to make an appearance.
The coaming can be represented by a piece of scrap cut 19 mm. thick, and attached to the carling near the point where the bottom screen frame meets it. That allows the off-vertical angle of the lateral screen member to be taken off the scrap, and that, in turn, gives the angle of cut across the width of the outer end of the bottom frame. The lateral frame pieces are rebated to accept the coaming, and then fixed to the bottom frame by mortice and tenon.
Mortice and tenon also fix the bottom frame to the central post, but only after the post has been attached to the stubby deck stringers which support it. That is ultimately achieved by gluing the floating tenon into the bottom of the post and screwing and gluing it between the stringers, but for now it sits there held by friction.
Here, the bottom
frames are only temporarily attached to the central post with biscuits.
The angles of the side frames can now be marked onto them, and cut on
the table saw.
The representations of coaming and lateral frame are fixed in position so that the bottom to lateral frame joint can be created.
The representations of coaming and lateral frame are fixed in position so that the bottom to lateral frame joint can be created.
When the post is fixed, the bottom frames are added, and they should line up exactly with the bottom of the coaming. If they do, the forward deck line is scribed onto them for shaping, and they are curved on their upper edges to parallel that line. They are then ready for gluing. If there is any discrepancy in the height of the bottom frames vis a vis the coaming, it is better to have them a little deep rather than shallow. Too deep can be accommodated by widening the coaming, but too shallow cannot, as it will reveal the carling underneath if the coaming is reduced in width.
Finally the lateral frame members can be put in. If there is a tight fit between them and the mock coaming it may be sufficient pressure for clamping, but, if not, some wedged clamps will have to be devised.
The lateral frames are added. All vertical members are left overlength.
The finished
joinery, ready for shaping to the deck camber.
Top of PageThe frame can now be scribed to
the deck camber plus 30 mm. and shaped, but first the glass retaining
groove has to be cut into the bottom frame piece while its top edge is
still straight. Then, the vertical members can be cut to the right
height, and the finials on top of them can be carved out. When the
frame is reassembled and glued into position I will put some sheets of
6 mm. ply into the window spaces to strengthen the structure, which
would otherwise be a bit vulnerable to damage as work on the boat
progresses. But it is necessary to have the windscreen in position now,
because the next step, the planning for the steering column, involves
the bottom screen frame as a support for the column.
Once the steering column
location is worked out, the shaping of the windscreen can start. The
finials are first cut onto a stencil, and then transferred to the
screen posts.
The finials on the posts are outlined from stencils.
The finials on the posts are outlined from stencils.
Then, the camber of the deck is
transferred to the bottom frames and they are shaped 30 mm. above it to
conform with the decking and the fillet and reveal which will later be
their visible components from outside the boat. Finally, the deck
stringer extensions are snugged up to the bottom frames and screwed to
the stringers in preparation for their gluing in position.
Once planed and checked with a batten for fairness, the extensions are glued in, along with a shim on the sheer clamp which corresponds with the one which was necessary on the other side.
Before cutting the finial on the posts I have taken a look at the projected height of the coaming by using a suspended batten. Once satisfied with the height, I moved the finial stencil and redrew its outline. The width of the coaming at the level of the windscreen is 225 mm. With a bit of luck I might be able to find a 10 or 12 inch board and cut it diagonally to make two coamings. Otherwise, if two have to be joined together to make up the width it would be nice to hide the joint with the cockbead which will later be applied over the coaming to conceal its screws into the carlings.
The width of the coaming is being estimated with the use of a batten.
Before the screen members can be glued together they have to be shaped. The finials are a signature part of this boat, and can only really be done by hand unless you have a shaper made up for the job, which is hardly an economic proposition. So, coping saw, files and sandpaper get a fairly good line which can be fine tuned once the screen is fixed in place.
The finials on the windscreen posts.
After shaping, the
bottom frames parallel the deck camber (left), and the stringer
extensions are screwed on (right).
The extensions will
now be planed down to the stringer level and the structure is ready for
the application of the subdeck.
Once planed and checked with a batten for fairness, the extensions are glued in, along with a shim on the sheer clamp which corresponds with the one which was necessary on the other side.
Before cutting the finial on the posts I have taken a look at the projected height of the coaming by using a suspended batten. Once satisfied with the height, I moved the finial stencil and redrew its outline. The width of the coaming at the level of the windscreen is 225 mm. With a bit of luck I might be able to find a 10 or 12 inch board and cut it diagonally to make two coamings. Otherwise, if two have to be joined together to make up the width it would be nice to hide the joint with the cockbead which will later be applied over the coaming to conceal its screws into the carlings.
The width of the coaming is being estimated with the use of a batten.
Before the screen members can be glued together they have to be shaped. The finials are a signature part of this boat, and can only really be done by hand unless you have a shaper made up for the job, which is hardly an economic proposition. So, coping saw, files and sandpaper get a fairly good line which can be fine tuned once the screen is fixed in place.
The finials on the windscreen posts.
Having determined
the position of the spotlight handle, which will penetrate the deck in
front of the windscreen, and pass down into the cockpit, the first of
two bolts can be drilled through the central stringers and the
windscreen support peg.
For jobs like this, which would
have been better thought out and drilled for beforehand, but which
occur to the builder too late, there is a wonderful
device I happened across which compensates for belated thoughts. It
only has
a non-keyed chuck, so sometimes slips, but is nevertheless a life
saver. In the tight spot above it was the only way to proceed.
The right angle drill chuck attachment...a winner.
The right angle drill chuck attachment...a winner.
The finished windscreen can now
be removed from the deck stringers and put aside out of harm's way.
The "free" steering wheel which came with the Teleflex steering system, is a disgusting black plastic number whose consignment to the trash is only being delayed until I have extracted its metal parts, because they are designed to mesh with the tapered shaft of the helm, and they will be useful when transposed onto a decent looking column.
The front and back of the free wheel.
The column supports which are attached to the windscreen and the dash bulkhead, will, therefore, be nothing more than fixations, as there will be no turning parts in contact with them. In fact, the one on the bulkhead might be a purely decorative face plate concealing an epoxy plug around the column as it disappears into the helm mounting box.
So, all that remains to be worked out is how to attach the helm's shaft to the steering shaft. It is supposed to be tightened into the wheel by a nut and washer, but that cannot be done to attach a second shaft. Instead, it may be necessary to add a hollow taper onto the end of the long shaft, and bolt it onto the helm shaft, just as the tiller is bolted onto the rudder stock. That should work. But if it does there will be no room for the bezel, as can be seen below.
With the bezel attached there is almost no room between the keyway and the bezel itself. With the bezel off, however, there is
plenty of room.
The bronze coloured bolts seen above will be fully wound down when the helm is fitted, and if the aluminium posts which house the screws from the bezel get in the way they can be removed. There seems to be no need for the bezel, which only serves a cosmetic function when it is mounted in a visible location. As this part of the mechanism will be in the motor compartment out of view the bezel can be dispensed with, allowing the shaft extension adequate space for attachment. (If it were deemed necessary to retain the bezel, a larger hole could always be bored into it anyway.
In the end it was decided that the best solution was to turn down a steel rod to be 3/4", but that a hollow taper would be bored into one end where the original thickness was retained. The thickness was to be sufficient to allow it to form a sleeve which would fit well over the taper on the helm and beyond, making enough room for grub screws to pass through its wall and into dimples punched into the helm shaft behind the taper. The grub screws would prevent the long column from being pulled away from the helm, and the original key mechanism would enable the turning of the wheel and helm. My propeller shaft suppliers, D H Porter of Parramatta, were able to produce the parts in quick time.
In order to find a comfortable
position for the wheel, I mocked up a wheel and column with a seat in
place. This helps to determine the length of the column and its angle
with the bulkhead. Once that angle is determined, the dimensions of the
helm mounting box can be laid out
68. The Helm Mounting Box
The angle at which the steering column passes through the bulkhead could not be pre-determined. It required some facsimile of the seating and windscreen to be in position. So it was not possible to order a helm with the 10° or 20° wedges which can be supplied with it. Instead, I want to attach to the forward side of the dash bulkhead an angled box to which the helm mount can be fixed, and which will allow the helm to meet the column in a perfectly straight line. Naturally, the mounting plate will be perpendicular to the column, and the angle at which its plane meets the bulkhead will be the reciprocal of the angle at which the column meets the bulkhead.
The box needs to be strong enough to stand the force transmitted by the rudder to the helm via the steering cable and the rack, and it needs to allow the rack to be twisted away from horizontal in order to allow the cable to run at the best angle to its conduit, preventing too sudden a change of direction. (The mount itself allows 20° of twist to be made in either direction). The minimum radius of curvature of the cable should be 8".
It also needs to be out of the way of battery housings and electrical cabling.
The actual mounting plate of the box is constructed of two pieces of 9 mm. ply glued together. The dimensions are given in the templates which accompany the helm. In this case I am using 180 mm. x 180 mm. This plate will be screwed on to the four box sides which will be attached to the bulklhead. Because of the need to be able to get a tool onto the bolt heads, which are holding the helm onto the metal mounting plate, the top and bottom of the box must remain removable, so they too will be screwed onto the box sides. Clearly the sides are the major force resisting components of the box, and they need to be thick enough to get a good purchase on the bulkhead.
The templates for the mounting plate (left), and the plate bearing component of the mounting box being
laminated (right).
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The angle at which the steering column passes through the bulkhead could not be pre-determined. It required some facsimile of the seating and windscreen to be in position. So it was not possible to order a helm with the 10° or 20° wedges which can be supplied with it. Instead, I want to attach to the forward side of the dash bulkhead an angled box to which the helm mount can be fixed, and which will allow the helm to meet the column in a perfectly straight line. Naturally, the mounting plate will be perpendicular to the column, and the angle at which its plane meets the bulkhead will be the reciprocal of the angle at which the column meets the bulkhead.
The box needs to be strong enough to stand the force transmitted by the rudder to the helm via the steering cable and the rack, and it needs to allow the rack to be twisted away from horizontal in order to allow the cable to run at the best angle to its conduit, preventing too sudden a change of direction. (The mount itself allows 20° of twist to be made in either direction). The minimum radius of curvature of the cable should be 8".
It also needs to be out of the way of battery housings and electrical cabling.
The actual mounting plate of the box is constructed of two pieces of 9 mm. ply glued together. The dimensions are given in the templates which accompany the helm. In this case I am using 180 mm. x 180 mm. This plate will be screwed on to the four box sides which will be attached to the bulklhead. Because of the need to be able to get a tool onto the bolt heads, which are holding the helm onto the metal mounting plate, the top and bottom of the box must remain removable, so they too will be screwed onto the box sides. Clearly the sides are the major force resisting components of the box, and they need to be thick enough to get a good purchase on the bulkhead.
The templates for the mounting plate (left), and the plate bearing component of the mounting box being
laminated (right).
Very soon I will need to be
getting into the motor compartment for the next stage of construction,
so before attaching the mounting box I remove the deck stringers and
motor for easy access. The motor bearers are not yet glued down, so
this seems like a good time to get started with that as well.
The foredeck structures are removed for access.
The foredeck structures are removed for access.
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69. Odd Jobs
The propeller has arrived and
has been fitted to the shaft. It is a little smaller than I had hoped,
as it was made at 12.5" instead of 320 mm., but it will do the job. And
the tiller is ready to be fitted to the rudder stock.
I have to arrange some help
lifting again to get the rudder into the boat, and then out again after
marking so that a flat can be filed onto it to seat the bolts from the
tiller's collar. The skeg still needs to be manufactured too, but its
precise measurements cannot be taken until the rudder, or a dummy, is
in
place in the rudder tube.
Meanwhile, the rear deck hatch
is being covered with its ply subdeck
for fitting into the rear deck.
The spotlight I have acquired is
a 1949 model which runs a 6 volt 36 watt system. To operate this on a
12 volt system requires a high power 1 ohm resistor, or a similar
volatge reducing mechanism, which generates a lot of heat. An
alternative is to change the light to operate a 12 volt 36 watt globe,
and that is what I have done. (Not that it is easy to find these old
light bulbs. I have been able to source mine from Tim Hodgekiss at Vintage Motor Spares).
The original was a single contact one, which presumably
allowed the current to pass through the body of the light housing to
the boat cabin, or some other path to earth. A double contact one would
be preferable for my purposes, but that would be asking a lot of
replacement parts, which are even more difficult to find. So I rewired
the light to take two cables, one to the single contact, and the other
to a point on the housing which goes back to the negative bus board.
The contact with the electrical system is made via a deck mounted
waterproof plug. Although it is not a perfect system, at least there is
no need to use the light in the case of an electrical short, so there
will be no inevitable damaging current leakage.
The rewired spotlight.
With the arrival of some younger
muscle at Christmas time I was able to lift the back of the boat far
enough to allow the ruddder to be inserted. With a false skeg and
button bearing in place the projection of the rudder stock through the
tube into the rudder compartment could be marked, and the rudder again
withdrawn for a flat to be filed onto it for the bedding of the tiller
set screws.
Representing the
skeg, a piece of ply projects back from the keel, and a 5 mm. addition
allows for the button bearing.
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Problems shows higher resolution shots as well.