The winch on the trailer needs
something to fasten to in the form of a bow eye, and this can be
attached to the stem, but inside the forward compartment the stem meets
a thinned section of hull where the flat was planed onto. Further
inside that is a fillet of epoxy, and then the
longitudinal girder, which is composed of 9 mm. ply. These hardly
constitute a solid grip for a screw eye, even if it is epoxy bedded.
It would be nice to be able to provide a solid hardwood fillet inside the bow to take the force of the winch, but the acute angle at which the hull sides meet at the bow make working there very difficult. It is impossible even to get a tool in there. Had I thought of this earlier I would have cut a bite out of the girder before it was positioned, but it is too late for that now.
The right angle attachment I found for my electric drill gives me an idea that a flexible attachment might serve to cut a hole in the girder, but the problem still remains that the distance from the outside of the stem to the point at which a flat might be able to be carved into the epoxy fillet inside the bow is about 70 mm. which is a long stretch for a U bolt.
(Added to that, the location of the screws which
hold the stem onto the
hull is now concealed under the outer layer of the stem, and it would
be just my luck to find one with the U bolt).
However,
there are bolted bow eyes with 100 mm. reaches, and this may
be the answer. The same problem applies regarding the hidden screws,
but
if I am able to get past that I will be able to drill into the girder
far enough to allow me to create a flat in it to support the nut and
washer which form part of the eye.
In the end I was lucky with the screws and was just able to get a nut and washer on. The whole lot will be epoxied into place now.
The bow eye and the cavity created for its nut and washer.
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The pump I have chosen is a small Rule pump of 500 GPH capacity, which is garishly coloured to proclaim its country of origin. Thankfully, it will be concealed under the sole. Apart from the fact that it was on special at the time I bought it, the availability of a bracket to hold it appealed to me. I can screw the bracket to one of the floors or longitudinal floor timbers, and drop the pump into it in the deepest part of the bilge, but out of the way of the shaft or seal.
The pump (left), bracket (centre), and combination (right).
It would be nice to be able to provide a solid hardwood fillet inside the bow to take the force of the winch, but the acute angle at which the hull sides meet at the bow make working there very difficult. It is impossible even to get a tool in there. Had I thought of this earlier I would have cut a bite out of the girder before it was positioned, but it is too late for that now.
The right angle attachment I found for my electric drill gives me an idea that a flexible attachment might serve to cut a hole in the girder, but the problem still remains that the distance from the outside of the stem to the point at which a flat might be able to be carved into the epoxy fillet inside the bow is about 70 mm. which is a long stretch for a U bolt.
In the end I was lucky with the screws and was just able to get a nut and washer on. The whole lot will be epoxied into place now.
The bow eye and the cavity created for its nut and washer.
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The pump I have chosen is a small Rule pump of 500 GPH capacity, which is garishly coloured to proclaim its country of origin. Thankfully, it will be concealed under the sole. Apart from the fact that it was on special at the time I bought it, the availability of a bracket to hold it appealed to me. I can screw the bracket to one of the floors or longitudinal floor timbers, and drop the pump into it in the deepest part of the bilge, but out of the way of the shaft or seal.
The pump (left), bracket (centre), and combination (right).
It is also possible
to buy a strainer for the inlet of these devices, which is probably a
good idea, and a float switch, but by the time you have put all that
together you will have spent just as much as a large, fully automatic
pump anyway. The small size is a clear advantage in this case because
of the small compartment into which I want to place it.
It will run on 1.9 amps at 12 volts, but that increases to 2.5 at 13.6 volts, so the fuse size needed is 3 amps. The hose is a 3/4" ID hose, which will be fed up under and through the floor longitudinal timbers to a through-hull fitting, and the wires will head in to share the conduit for the house battery leads, and thence to the motor compartment, where they will ascend the dash bulkhead to the bilge pump switch on the dashboard. I am keeping the bilge pump switch off the main distribution panel, so that it can still be operated even if there is a major malfunction with the panel. An in-line fuse will do the job here.
The wires on the pump itself are 16 AWG, which is sufficient for runs of up to 7.5 metres. This wire would easily tolerate 10 amps, so if it were necessary it could be protected with a 10 amp fuse, but since the pump needs a 3 amp fuse both functions can be achieved by locating a 3 amp one between the battery positive and the switch.
The black hose is for the bilge pump. The clear one is for the shaft seal. Pump wiring is held up above the bilge.
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83. The Bilge Blower
It will run on 1.9 amps at 12 volts, but that increases to 2.5 at 13.6 volts, so the fuse size needed is 3 amps. The hose is a 3/4" ID hose, which will be fed up under and through the floor longitudinal timbers to a through-hull fitting, and the wires will head in to share the conduit for the house battery leads, and thence to the motor compartment, where they will ascend the dash bulkhead to the bilge pump switch on the dashboard. I am keeping the bilge pump switch off the main distribution panel, so that it can still be operated even if there is a major malfunction with the panel. An in-line fuse will do the job here.
The wires on the pump itself are 16 AWG, which is sufficient for runs of up to 7.5 metres. This wire would easily tolerate 10 amps, so if it were necessary it could be protected with a 10 amp fuse, but since the pump needs a 3 amp fuse both functions can be achieved by locating a 3 amp one between the battery positive and the switch.
The black hose is for the bilge pump. The clear one is for the shaft seal. Pump wiring is held up above the bilge.
A close look at the plans for
this boat will show that the bilge pump shown above is not at the
deepest part of the bilge. Theoretically it should be at the level of
bulkhead B, the front end of the motor compartment. However, a
scientific trial of this (with the aid of a rolling golf ball)
demonstrated that there was very little practical difference between
the level of the motor compartment and the shaft seal compartment.
Because of the much more ready access to the latter I have placed the
pump there. Any water in the motor compartment will soon be pushed back
into the shaft seal compartment when the boat is lifted onto its
trailer at the end of the day, so it can be pumped out then. Prior to
that, while the boat is in the water, the placement of the pump will
only allow a centimetre or so of water to accumulate anyway.
83. The Bilge Blower
It
has
been pointed out to me that a bilge blower is not necessary in an
electrically powered boat, because of the absence of petrol or diesel
fumes in the engine compartment. That is true enough, but the other
"vapour" which needs to be considered is water vapour. Much of the
design
of the boat is directed towards achieving adequate ventilation, and a
system of louvres and vents is supposed to allow just that. However, it
seems to me that the provision of a fan induced draught can also help
here, and a bilge blower is just what is needed.
Generally there are two types for pleasure craft: the in-line type, which draws air in and pushes it out in a straight line past the fan, and the sort which blows it around a right angle. They are meant to be connected to exhaust hoses of either 3" or 4" diameter, and thence to a vent on the deck or transom. The input voltage varies, as does the current draw and the capacity for moving air volume. For a general air circulation function no great capacity is required, so a low current draw model seems appropriate.
The best configuration for my purpose is to have an offset pump motor, rather than an in-line one. This way I can screw the outlet directly to an opening in the bulkhead, and no hose is necessary. Until such time as the rear vent is fitted to the deck the circulated air is re-entering the rudder compartment via the limber hole, but that will change when the vent is working.
The bilge blower attached to bulkhead F.
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Generally there are two types for pleasure craft: the in-line type, which draws air in and pushes it out in a straight line past the fan, and the sort which blows it around a right angle. They are meant to be connected to exhaust hoses of either 3" or 4" diameter, and thence to a vent on the deck or transom. The input voltage varies, as does the current draw and the capacity for moving air volume. For a general air circulation function no great capacity is required, so a low current draw model seems appropriate.
The best configuration for my purpose is to have an offset pump motor, rather than an in-line one. This way I can screw the outlet directly to an opening in the bulkhead, and no hose is necessary. Until such time as the rear vent is fitted to the deck the circulated air is re-entering the rudder compartment via the limber hole, but that will change when the vent is working.
The bilge blower attached to bulkhead F.
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84. Joining-Up the Limber Holes
Up to this point the placement
of limber holes for the free drainage of bilge water has been easy
enough. They have been located in the midline of the boat where the
bilge is deepest. But there is a problem at bulkhead D and its attached
floors. Here, the stern tube for the propeller shaft emerges through
the hull, and almost immediately enters the bulkhead/floor complex as
it passes forwards. The use of a steel tube has meant that I can
dispense with a traditional shaft log, as the tube is epoxy glassed
onto the very substantial complex, as well as passing through a hole in
it.
I do not want to weaken that area by placing a limber hole there, so I will have to substitute two holes placed a little outboard of the midline. The trouble with that is that they will not be at the deepest part of the bilge, so water will be able to accumulate astern of the floor up to the level of the bottom of the holes. (Forward of the floor the water will drain forwards when the boat is floating level, and will find its way into the bilge pump).
The problem area for drainage lies where the tube emerges through the bilge and bulkhead.
The original plans for this boat had a hog in the bilge, so that the limber holes would have had to have been placed lateral to the hog anyway, but in this case the water could not accumulate. The solution then is to build a mini hog, a "hoglet", to place astern of the floor and bring the level of the bilge up to the level of the bottom of the limber holes, and, considering the small area involved it seems appropriate to construct the hoglet out of poured epoxy resin, rather than trying to fashion one out of wood and glue it in.
Astern of the bulkhead D/floor complex (left), forward of it (centre), and astern of the intermediate floor between bulkheads D and C (right).
I do not want to weaken that area by placing a limber hole there, so I will have to substitute two holes placed a little outboard of the midline. The trouble with that is that they will not be at the deepest part of the bilge, so water will be able to accumulate astern of the floor up to the level of the bottom of the holes. (Forward of the floor the water will drain forwards when the boat is floating level, and will find its way into the bilge pump).
The problem area for drainage lies where the tube emerges through the bilge and bulkhead.
The original plans for this boat had a hog in the bilge, so that the limber holes would have had to have been placed lateral to the hog anyway, but in this case the water could not accumulate. The solution then is to build a mini hog, a "hoglet", to place astern of the floor and bring the level of the bilge up to the level of the bottom of the limber holes, and, considering the small area involved it seems appropriate to construct the hoglet out of poured epoxy resin, rather than trying to fashion one out of wood and glue it in.
Astern of the bulkhead D/floor complex (left), forward of it (centre), and astern of the intermediate floor between bulkheads D and C (right).
Apart from that, the placement of limber holes is straight
forward. They go through the centre of the bulkheads and floors.
Off centre limber holes are used for the intermediate floors behind and in front of bulkhead D too.
Behind that level single central ones are employed.
The drainage system for water is being complemented by a system of ventilation holes for that other inaccessible area, the cockpit sides. Here, air circulation is assured by placing holes in the sole panels located behind the lagging, and thence into the rudder compartment through bulkhead E. Once there, the air is blown into the stern floatation compartment and out through the vent. Vents on top of the motor compartment hatch covers scoop air into the motor compartment, and from there it can enter the sub sole and cockpit sides via the limber holes and some intake vents which have been placed on the bulkhead.
An intake vent to the cockpit side from the motor compartment is located underneath the
aerial for the stereo. Now you wouldn't do that with a diesel!!!
Large cut-outs in bulkhead B give free circulation to the fuel compartment, and fenestrations in bulkhead A allow communication with the forward floatation compartment.
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Off centre limber holes are used for the intermediate floors behind and in front of bulkhead D too.
Behind that level single central ones are employed.
The drainage system for water is being complemented by a system of ventilation holes for that other inaccessible area, the cockpit sides. Here, air circulation is assured by placing holes in the sole panels located behind the lagging, and thence into the rudder compartment through bulkhead E. Once there, the air is blown into the stern floatation compartment and out through the vent. Vents on top of the motor compartment hatch covers scoop air into the motor compartment, and from there it can enter the sub sole and cockpit sides via the limber holes and some intake vents which have been placed on the bulkhead.
An intake vent to the cockpit side from the motor compartment is located underneath the
aerial for the stereo. Now you wouldn't do that with a diesel!!!
Large cut-outs in bulkhead B give free circulation to the fuel compartment, and fenestrations in bulkhead A allow communication with the forward floatation compartment.
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85. Levelling the
Floors
Until
now, the sole panels have been just sitting on top of the floors,
unattached. With the completion of the limber hole and ventilation network, and the threading of
the bilge pump tubing through the bilge, it is time to secure the sole
permanently. There are still a few creaks and groans when I walk on the
sole, implying that the panels are not lying flat, and in some areas it
can be seen that the intersection of athwartships and longitudinal
floors has left one member sitting a little proud of the other. These
are now levelled with a plane where there is room, or with a sharp
chisel where there is not, until a creak free platform for the sole
panel is achieved. While it would be nice to claim that all the panels
are going to lie in a single uniform plane, in practice it does not
really matter all that much. The differences are very slight, and there
will be carpet anyway. So there is no place here for long straight
edges to monitor the levelling process. Once the panels are sitting
flat, the position of the floors is marked onto their top surfaces for
the countersunk screw holes, and they are given a final sanding and
finish on the undersurface. I am going to use epoxy to glue them down,
so the finish is straight resin.
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86.
Attaching the Sole
Only the outer sole panels are
to be glued down. Of the central ones, the larger rear one will
be screwed, and the smaller one over the shaft seal and bilge pump will
just sit there so that it is quickly removable. I have been a little
uneasy about the idea of making the majority of the bottom of the boat
permanently inaccessible, but the added strength derived from gluing
the outer panels, and filleting them to the hull sides will be useful
in a trailered boat, and that tipped the balance.
Here, the sole panels have been screwed down in preparation for gluing.
Note the ventilation holes in the sole behind the eventual location of the
cockpit lagging.
There is a tight fit between the panels, so they all have to be in position simultaneously while the glue is setting. That means introducing some epoxy proof paper between the permanent fixtures and the removable ones. Once the outer panels are screwed down any excess epoxy is removed from the half of the floors which will be shared with the central panels, and the filleting of the sole to side joint can begin.
That done, the rear central panel is screwed in, the front is dropped in, and when all is set any final planing of the edges of the removable panels can be done to ensure a squeak free sole.
In order not to be slipping around on the sole, I will not be using epoxy on the top surface. Instead I will be using Deks Olje #1, which achieves a matt finish, and is a better grip for the carpet and for feet.
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Here, the sole panels have been screwed down in preparation for gluing.
Note the ventilation holes in the sole behind the eventual location of the
cockpit lagging.
There is a tight fit between the panels, so they all have to be in position simultaneously while the glue is setting. That means introducing some epoxy proof paper between the permanent fixtures and the removable ones. Once the outer panels are screwed down any excess epoxy is removed from the half of the floors which will be shared with the central panels, and the filleting of the sole to side joint can begin.
That done, the rear central panel is screwed in, the front is dropped in, and when all is set any final planing of the edges of the removable panels can be done to ensure a squeak free sole.
In order not to be slipping around on the sole, I will not be using epoxy on the top surface. Instead I will be using Deks Olje #1, which achieves a matt finish, and is a better grip for the carpet and for feet.
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87. Finishing Touches to
the Rear Seat
There is a gap between the rear
seat back and the cockpit side which has to be filled. The situation
can be appreciated with the seat back folded down.
The scrap pieces seen above represent the coaming, which has to be allowed for in the design of the gap fill.
The scrap pieces seen above represent the coaming, which has to be allowed for in the design of the gap fill.
In order to take the lagging
back to the bulkhead it is necessary to add two more cleats, on the
seat platform and the bulkhead itself.
A mock-up of the rear lagging
board is then fitted over the parts, and blocked out away from the
cleats and carling until the thickness of the real boards is
approximated. A slightly wedge shaped filler is introduced into the
gap, and then a piece of hardboard edging is cut to fit alongside its
counterpart on the seat back.
Next, a wedge of ply is cut to
fit into the triangular space between the seat edge and the lagging.
The coaming is removed from the carling to allow it to slip in. The
triangle is trimmed to shape, and edged with hardwood on the top.
The outline of the side coaming
is scribed on to the ply for removal, so that the coaming can later
pass
through to the back. The entire complex, with the exception of the
false lagging, can now be glued up ready to be attached to the real
lagging next month.
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The same is done on the
starboard side, and the seat is finished.
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88. Upholstery
With the completion of the rear
seat it is time to introduce the other half of this boat building team
to her first task, upholstering the rear seat cushions. The basic
arrangement is to have a large cushion for the seat base, and a smaller
one for the back sitting on top of it. They can be made out of cut
foam, preferably wrapped in some sort of wadding so that it does not
feel so much like foam. The covers should be made from something
reasonably water resistant, but preferably not as synthetic feeling as
vinyl. A light, treated canvas would be ideal. Some of the woven
acrylic
canvases have the advantage of resisting mildew, which cotton canvas
does not.
The fiddle on the front of the seat holds the base cushion in position, but only to a degree. Sitting on them tends to raise the edge so that it can slip forward unless the fiddle is so high that it cuts into the back of the knees. A very acceptable alternative here might have been to use Velcro fastening, one strip attached to the seat bottom, and the other to the cushion. That precludes the possibility of turning the cushion over to even out the wear, but canvas is not all that expensive anyway. Well, that's what I thought. It turns out that the soft acrylic canvas which is comfortable to sit on is $52 per metre!!! Stuff the Velcro.
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The fiddle on the front of the seat holds the base cushion in position, but only to a degree. Sitting on them tends to raise the edge so that it can slip forward unless the fiddle is so high that it cuts into the back of the knees. A very acceptable alternative here might have been to use Velcro fastening, one strip attached to the seat bottom, and the other to the cushion. That precludes the possibility of turning the cushion over to even out the wear, but canvas is not all that expensive anyway. Well, that's what I thought. It turns out that the soft acrylic canvas which is comfortable to sit on is $52 per metre!!! Stuff the Velcro.
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89. The House Battery System
For much of what appears below
I am again indebted to Charles Fitzhardinge of Solarboat whose
generosity of time and encyclopaedic knowledge of matters electrical
has been called upon more than once to augment my own high school
understanding of physics.
Because of the greater availability of 12 volt appliances than 24 volt, and also because of the suspicion that I might be eventually settling on a higher voltage than 24 for my drive system anyway, I had decided to have two separate power supplies on the boat. One would be 12 volts for the domestics, the other 24 volts or above for the drive. I simply intended to use two 6 volt golf cart batteries for the house system, but that leaves open the question of recharging them. There would have to be two chargers if both systems were to be charged from AC, but if the 12 volt system were charged from the drive battery bank via a DC to DC step down converter, only one charger would be needed and the house system could be recharging whenever the main batteries were in use. At this point I am thinking of a 24 to 12 volt converter, although in order to bring the 12 volt batteries up to peak power the converter would have to be able to output 13.6 to 13.8 volts. The thought then occurred, why have a 12 volt battery at all if the converter is producing enough power for the domestic demand?
As Charles has pointed out, there are three possible solutions here:
1. Have the converter only, no 12 volt battery, but in this case the converter will have to have enough output to be able to meet all the current requirements of all the domestic circuits being on simultaneously. I estimate that it could be up to 30 amps of current being drawn, meaning that the converter would have to be able to put out 360 watts. These high powered converters are on the pricey side (A$300 to 500 approx.). Mind you, you don't have the expense of the batteries.
2. Have a lower powered, and therefore cheaper, converter combined with a small battery. The battery now acts not only as a small extra source of amp hours, but also as a buffer for the converter, so that any current demand which cannot be met by the converter will draw down on the battery; but when the demand falls the converter will start to recharge the battery. With this scenario, the converter could be chosen to supply the average likely demand, (say 50 watts), and the battery would not need to be a deep cycle one. A simple car battery would do because the peak demand periods would be infrequent and of short duration, so that deep discharging of the battery would never occur.
3. Have a very small converter and deep cycle batteries. This is based on estimated low usage of the boat and therefore long recharge time availability. The house system demands would be met by the deep cycle batteries, and the converter would act almost entirely as a recharger when the current draw is off. Since it would have a long time to do so (the days of the week when the boat is not being used) it would be adequate to have a low power rating converter.
Of these possibilities, I have chosen the second, partly because I just happen to have a 12 volt car battery sitting around anyway.
Downstream of the converter, the 12 volt supply is split into two banks: the first, which bypasses the distribution board, goes first to a circuit breaker and then on to a positive bus board. Individual circuits for the independent devices feed off the bus board via in-line fuses, where necessary, to the following apparatus:
1. The horn
2. The bilge pump
3. The cockpit lights (three circuits)
4. The back-up for the stereo (unfused)
The bus board also feeds a keyed ignition switch on the dashboard, which, when in the on position, forwards power to the distribution panel. From there the following are controlled:
1. The refrigerator
2. The stereo
3. The spotlight
4. The navigation lights (five circuits)
5. The bilge blower
6. The instrument lights (four circuits)
The reason for this arrangement is simple: I want to be able to get into the boat at night and easily find the switch to illuminate the dash with the forward cockpit light, and not have to fumble around trying to find the key hole in the ignition switch before I can do so. The bilge pump has to be able to be left on when the boat is at anchor with the power off. The horn is necessary for an emergency when there may be no power to the distribution panel. The stereo needs constant power to remember its presets, time, etc., the current draw for which is tiny.
The wiring is kept as orderly as possible with the use of spiral wrapping, but, even so, it looks a bit daunting at first, and this is only beginning of the house system!
Because of the greater availability of 12 volt appliances than 24 volt, and also because of the suspicion that I might be eventually settling on a higher voltage than 24 for my drive system anyway, I had decided to have two separate power supplies on the boat. One would be 12 volts for the domestics, the other 24 volts or above for the drive. I simply intended to use two 6 volt golf cart batteries for the house system, but that leaves open the question of recharging them. There would have to be two chargers if both systems were to be charged from AC, but if the 12 volt system were charged from the drive battery bank via a DC to DC step down converter, only one charger would be needed and the house system could be recharging whenever the main batteries were in use. At this point I am thinking of a 24 to 12 volt converter, although in order to bring the 12 volt batteries up to peak power the converter would have to be able to output 13.6 to 13.8 volts. The thought then occurred, why have a 12 volt battery at all if the converter is producing enough power for the domestic demand?
As Charles has pointed out, there are three possible solutions here:
1. Have the converter only, no 12 volt battery, but in this case the converter will have to have enough output to be able to meet all the current requirements of all the domestic circuits being on simultaneously. I estimate that it could be up to 30 amps of current being drawn, meaning that the converter would have to be able to put out 360 watts. These high powered converters are on the pricey side (A$300 to 500 approx.). Mind you, you don't have the expense of the batteries.
2. Have a lower powered, and therefore cheaper, converter combined with a small battery. The battery now acts not only as a small extra source of amp hours, but also as a buffer for the converter, so that any current demand which cannot be met by the converter will draw down on the battery; but when the demand falls the converter will start to recharge the battery. With this scenario, the converter could be chosen to supply the average likely demand, (say 50 watts), and the battery would not need to be a deep cycle one. A simple car battery would do because the peak demand periods would be infrequent and of short duration, so that deep discharging of the battery would never occur.
3. Have a very small converter and deep cycle batteries. This is based on estimated low usage of the boat and therefore long recharge time availability. The house system demands would be met by the deep cycle batteries, and the converter would act almost entirely as a recharger when the current draw is off. Since it would have a long time to do so (the days of the week when the boat is not being used) it would be adequate to have a low power rating converter.
Of these possibilities, I have chosen the second, partly because I just happen to have a 12 volt car battery sitting around anyway.
Downstream of the converter, the 12 volt supply is split into two banks: the first, which bypasses the distribution board, goes first to a circuit breaker and then on to a positive bus board. Individual circuits for the independent devices feed off the bus board via in-line fuses, where necessary, to the following apparatus:
1. The horn
2. The bilge pump
3. The cockpit lights (three circuits)
4. The back-up for the stereo (unfused)
The bus board also feeds a keyed ignition switch on the dashboard, which, when in the on position, forwards power to the distribution panel. From there the following are controlled:
1. The refrigerator
2. The stereo
3. The spotlight
4. The navigation lights (five circuits)
5. The bilge blower
6. The instrument lights (four circuits)
The reason for this arrangement is simple: I want to be able to get into the boat at night and easily find the switch to illuminate the dash with the forward cockpit light, and not have to fumble around trying to find the key hole in the ignition switch before I can do so. The bilge pump has to be able to be left on when the boat is at anchor with the power off. The horn is necessary for an emergency when there may be no power to the distribution panel. The stereo needs constant power to remember its presets, time, etc., the current draw for which is tiny.
The wiring is kept as orderly as possible with the use of spiral wrapping, but, even so, it looks a bit daunting at first, and this is only beginning of the house system!
The wiring for the
four stereo speakers is kept on a separate connection bar.
The other branch of the wiring
goes through the distribution panel. It feeds on to the refrigerator,
which will plug into
a socket in the cockpit, (which could
also act as an accessory power outlet), and all
the
navigation lights which are on
separate circuits, but
activated by a single switch. Their positive line from the switch goes
via a mini bus bar to all five lights and their return is to the main
negative bus bar via another mini bar (see below).
The negative side is
a bit simpler than the positive. The distribution panel's
negative feeds on
to the main negative bus bar. The cockpit lights are also returned to a
mini bar first. The rest, comprising, stereo, power
outlet for fridge, horn, bilge blower, instruments and
spotlight go directly back to the main negative bus, and on to the
battery negative. All
circuits are closed so as to avoid the necessity for bonding.
The picture on the left shows the negative
side beginning to be put together. The double bus bar on the far left
is for the navigation lights, of which four are already connected. Its
positive side will be connected to the switch in the distribution
panel, and its negative side will be connected to the main negative bus
bar, which is the one on the right. Two devices have been wired into
the main negative here, the bilge blower and a light for the rudder
compartment. All of the other devices will eventually find their way to
this bar.
A more economical alternative would have been to replace the double bar with a lower current capacity terminal block, converted into a bus bar by the use of jumpers, and that is what I am planning to use for the cockpit and compartment lights, which, like the navigation lights, will all operate from a single switch. But, when you take into consideration that you need either two of them, or one, with a large capacity negative return like the 12 point bar at the left, the cost saving is not that much.
The instruments employed on the 12 volt
system are a -50 to +50
ammeter, and a 10 to 16 voltmeter. The ammeter is connected directly
between the circuit breaker and the main positive bus, so that it
transmits all of the current emanating from the battery which is being
consumed by the domestic circuits. Its
backlight, however, is activated by the "Instruments" switch in the
distribution panel. The voltmeter is connected in parallel with the
battery.
The DC to DC converter could work simply by being attached directly to the battery poles in parallel with the battery, thereby acting as both a power source for the domestic appliances and as a battery charger. However, if it is, the ammeter will not register any current flow when the battery is being charged, because there will be no open circuits through the appliances back to the battery. If the positive lead from the converter is instead attached to the positive bus bar, ie. downstream from the ammeter, any charging current will have to pass through the ammeter to get to the battery, so it will register as a positive deflection (or negative, depending on how the ammeter is wired). This arrangement uses the ammeter to show only the current passing into or out of the battery, and not the total current consumed, as it does not register the current coming from the converter to the devices other than the battery. But it is not necessary to know precisely how much current is coming from the converter as opposed to the 12 volt battery, so the ammeter placement is satisfactory. Later, when the main drive system meters are installed, some influence of the current coming out of the converter will be felt, as its input current will register on the main battery ammeter, in addition to the draw from the motor controller. (In this situation the ammeter connection is similar to a car's, with the generator or alternator current being registered as positive flow into the battery.)
The domestic voltmeter, on the other hand, will merely reflect the current state of charge in the house battery, and can be attached between any positive and negative points in the circuit, (in parallel, of course) provided that they are at the same potential as the battery terminals, or so close to it that it makes no practical difference. Obviously, the further along the circuit you get the greater will be the voltage drop, so as close as practical to the battery is the best rule.
As more circuits are added the chaos gets worse, but it is all systematic and easy to trace.
What you can see here are: the main positive bus bar just to the left of the darker wood, the
positive and negative bars for the five navigation lights to the right of the positive bus bar, the
main negative bus bar to the right of that, the terminal block for the stereo speakers below the
dark wood, and a small terminal block for the instrument back lights above the distribution panel,
which is above the stereo head unit, which is above the battery switch.
Top of Page
In an effort to avoid too modern a look in the cockpit, I have opted for an old style set of gauges for the 12 volt system. The ammeter, which has not arrived yet, may be an unshunted one. This means that the cables running to and from it have to be big enough to handle the full current draw of the domestic system, or 30 amps. For the length of conductor required that means at least AWG 10 size cable to preserve a voltage drop of less than 3%. AWG 10 is equivalent to about 3 mm. diameter, which is heavy, but not outrageously so. The worry with these old style ammeters is that their high current carrying cables are connected to the electrical system in the assumption that the meter will always be in series with a load, and that the current they carry will not, therefore, be so high as to damage the meter. Which is all very well except in the case of a short, when there could be a high enough current to not only fry the meter, but also melt the wire and start a fire.
Such a disaster should be taken care of on a boat by upstream protection, but the only thing between the battery and the ammeter is the circuit breaker, and it is primarily there to protect the main battery cable rather than the ammeter. The standard battery cables are sold here in the so called B&S (Brown and Sharpe) rating, and the most readily available is B&S 2, which is 32 mm.² in cross section, equivalent to AWG 2, and that can be rated to carry up to 240 amps, depending on its insulation and the heat of its surroundings. It seems odd then to use a circuit breaker which breaks above 30 amps just to protect the ammeter.
Some ammeters have internal fuses to protect themselves, but others use external low resistance electrical shunts. The ammeter in the latter case might really be a voltmeter, measuring the very small potential difference across the shunt (with the addition of a voltage amplifier in many cases), and expressing it in amps by a derived formula. These instruments are safer, as they only require small gauge wires and carry very little current. They are actually connected in parallel with the circuit instead of in series. If neither of these pertains then it is probably best to introduce a secondary fuse between the battery and the meter.
Although, to be realistic, the boat is not a car. The 12 volt battery will not be required to serve any cranking action, so there is no need for such large capacity battery cables as AWG 2. It should be feasible to replace them with AWG 10 and a 30 amp breaker, and then use the ammeter in series with big wires. Just be careful to protect the wire as well as possible, and avoid shorts.
However, the distribution panel I am using has a cumulative amp rating of 90 amps because of its six 15 amp circuits, and although I am not going to be using equipment which draws anything like that amount of current, it would be permissible to protect the system with a 90 amp breaker, or, if there were to be a 90 amp sub-main breaker protecting just the panel, the main breaker could be rated up to 135 amps. Under those circumstances, AWG 2 cable would be necessary.
I think that the best compromise is to work out what the maximum actual current draw will be in each circuit, allocate individual fuse ratings to them and add it all up. Even allowing a mark up for the next available fuse rating for each circuit, the total draw is still under 30 amps, and less than 20 amps through the panel. Since there will not be anything like the possible 90 amp capacity reached it seems silly to use cables and protectors which could cope with that demand. Instead, I shall use B&S 8 cable which is rated to 85 amps if a 10% voltage drop is permissible, and a single breaker rated at 50 amps. That will protect the cable, the panel and the ammeter all in one.
The 12 volt Voltmeter
The voltmeter is an altogether more useful gauge than the ammeter, and less complex in its operating requirements. Being in parallel with the circuit, it does not carry a high current, and does not need heavy cabling. The only consideration is where to connect it to the circuit. It needs to be as close (electrically speaking) to the battery terminals as possible, so as to measure the condition of the battery charge. Its run of cable from the back of the dash needs to be as short as possible, so the ideal place to join it would seem to be to the main negative and main positive buses, which are located right next to the gauges on the back of the dash. The only inaccuracy then would be the tiny amount of voltage drop occurring in the main battery cables, the circuit breaker, the bus bar posts and the ammeter. If you were concerned about that you could bring it in upstream of the ammeter, in which case you would be making the ammeter slightly inaccurate by allowing it to ignore the small current passing through the voltmeter. Given the coarse nature of both of these instruments, in terms of their usefulness to illustrate battery condition, any fiddling with voltmeter connections would be to guild a rather faded lily anyway.
However, ideal is not always practical, and in this case, to connect the voltmeter between the main positive and negative bus bars would mean that it would be working all the time. I only want it working when I am drawing power from the batteries, and then really only when the devices wired through the distribution panel are running. So the positive lead to the voltmeter has to be downstream of the start switch which activates the panel. Luckily, there is a three pin positive bus bar on the panel itself. The switch runs down to one of them, and the voltmeter can be wired into another one. The voltage drop through the switch and its wires is negligible because of the short length involved.
The Battery Monitor
Battery monitors come in a variety of guises, from the very sophisticated (and expensive) amp hour counters, to the simpler and cheaper glorified voltmeters. As Ariadne will never be far from civilisation in her voyages, I do not want to have one of the expensive ones, but I do need something more than a voltmeter. There are two meters which look to fill the bill here: Sevcon's "Powergauge" and Curtis' battery discharge indicator. Thy both can come as a combination instrument with engine hour logging if you want, and both appear to work by measuring the battery capacity in a narrow voltage range and by estimating the percentage of discharge which has occurred. They do not predict cruising time left or amp hours remaining, but I don't think I need that facility.
Unfortunately they both operate with LED displays, which means that they will look a bit out of place in the dash console, and also that they can be difficult to read in bright light, but they are not as obtrusive as blinking LED numbers such as you find on the panel meters, and they do come in 2-1/16" (52 mm.) diameters, which allows them to fit in with the 12 volt instruments I already have.
Pure battery state of charge instruments are cheaper than the ones which log engine hours as well, but they operate only on a single input voltage. Some of the dual instruments can be operate on either of two voltages if required. Since I am not yet certain of the voltage at which I will be running this boat there is an advantage in choosing the one of those dual instruments. The one I chose was the central one below, the Curtis 8., rated for 36 or 48 volts. So that is the end of my initial plans for a 24 volt system. All other equipment will now have to be able to cope with at least 36 volts, and preferably 48.
The Sevcon "Powergauge" (left) which also has an hourmeter, the Curtis with hourmeter (centre), and without (right).
A Voltage Independent, High Current Ammeter
The only problem then with trying to
leave my options open is the main drive system ammeter, if I want one.
To find a dial analogue ammeter which is rated to operate on 48 volts
and give
+ or - 150 amps is proving very difficult. The sophisticated monitoring
gauges can cope with that, but they look like something out of Star
Wars. Luckily, once again Solarboat
has come to the rescue with just such an instrument for A$125 including
the shunt. That is too good to pass up, so it will soon be gracing my
dashboard. It is a Westach instrument 0 to 150 amps with a Deltec
shunt. (I don't suppose I need to know the current coming out of the
charger, so the lack of negative readings won't matter). Although there
is no mention of the combination being suitable
for 48 volts, there is no mention that it not either, so I shall assume
the best.
Actually, the whole concept of a voltage rating for an ammeter seems odd to me. It is not as though the ammeter is offering much in the way of resistance to the circuit, and neither is the shunt, so why would the voltage make any difference? The current is what does the damage, and, since the current will be set by the motor controller, as long as the ammeter is rated to handle the correct current I cannot see why the voltage would affect it at all. But perhaps we are really dealing with a kind of voltmeter when we use shunts. They are, after all, connected in parallel. Maybe that makes the difference.
Anyway, the instrument cluster is first sketched onto a piece of paper to find a good arrangement, and then the holes are cut out of the fascia panel, and the size of the cut-out in the dash bulkhead is determined. With that done the panel is screwed into the frame, and further wire connections are made in the motor compartment.
Here, the 12 volt meter, ignition switch, horn button, cabin light and bilge pump switches are in place, and further holes are waiting for the 12 volt ammeter, and the two main battery meters.
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Problems shows higher resolution shots as well.
The picture on the left shows the negative
side beginning to be put together. The double bus bar on the far left
is for the navigation lights, of which four are already connected. Its
positive side will be connected to the switch in the distribution
panel, and its negative side will be connected to the main negative bus
bar, which is the one on the right. Two devices have been wired into
the main negative here, the bilge blower and a light for the rudder
compartment. All of the other devices will eventually find their way to
this bar.A more economical alternative would have been to replace the double bar with a lower current capacity terminal block, converted into a bus bar by the use of jumpers, and that is what I am planning to use for the cockpit and compartment lights, which, like the navigation lights, will all operate from a single switch. But, when you take into consideration that you need either two of them, or one, with a large capacity negative return like the 12 point bar at the left, the cost saving is not that much.
The instruments employed on the 12 volt
system are a -50 to +50
ammeter, and a 10 to 16 voltmeter. The ammeter is connected directly
between the circuit breaker and the main positive bus, so that it
transmits all of the current emanating from the battery which is being
consumed by the domestic circuits. Its
backlight, however, is activated by the "Instruments" switch in the
distribution panel. The voltmeter is connected in parallel with the
battery.The DC to DC converter could work simply by being attached directly to the battery poles in parallel with the battery, thereby acting as both a power source for the domestic appliances and as a battery charger. However, if it is, the ammeter will not register any current flow when the battery is being charged, because there will be no open circuits through the appliances back to the battery. If the positive lead from the converter is instead attached to the positive bus bar, ie. downstream from the ammeter, any charging current will have to pass through the ammeter to get to the battery, so it will register as a positive deflection (or negative, depending on how the ammeter is wired). This arrangement uses the ammeter to show only the current passing into or out of the battery, and not the total current consumed, as it does not register the current coming from the converter to the devices other than the battery. But it is not necessary to know precisely how much current is coming from the converter as opposed to the 12 volt battery, so the ammeter placement is satisfactory. Later, when the main drive system meters are installed, some influence of the current coming out of the converter will be felt, as its input current will register on the main battery ammeter, in addition to the draw from the motor controller. (In this situation the ammeter connection is similar to a car's, with the generator or alternator current being registered as positive flow into the battery.)
The domestic voltmeter, on the other hand, will merely reflect the current state of charge in the house battery, and can be attached between any positive and negative points in the circuit, (in parallel, of course) provided that they are at the same potential as the battery terminals, or so close to it that it makes no practical difference. Obviously, the further along the circuit you get the greater will be the voltage drop, so as close as practical to the battery is the best rule.
As more circuits are added the chaos gets worse, but it is all systematic and easy to trace.
What you can see here are: the main positive bus bar just to the left of the darker wood, the
positive and negative bars for the five navigation lights to the right of the positive bus bar, the
main negative bus bar to the right of that, the terminal block for the stereo speakers below the
dark wood, and a small terminal block for the instrument back lights above the distribution panel,
which is above the stereo head unit, which is above the battery switch.
Along
with
all the wiring comes some new hardware. The compartment light for
the motor compartment is placed on bulkhead B, so that it can shine
from behind me when I am working on the wiring looms in the future, and
the new steering wheel's arrival has allowed me to ditch the terrible
old plastic one.
The
light
in the rudder compartment is attached to bulkhead F, and its
wiring has to pass through that bulkhead, so it is taken down into the
locker under the rear seat. Because it is liable to be snagged by life
jackets, etc. which may be thrown into the locker, I have protected it
by routing it through some clear tubing.
The route taken by the wiring for the rudder compartment light.
The route taken by the wiring for the rudder compartment light.
Top of Page
In an effort to avoid too modern a look in the cockpit, I have opted for an old style set of gauges for the 12 volt system. The ammeter, which has not arrived yet, may be an unshunted one. This means that the cables running to and from it have to be big enough to handle the full current draw of the domestic system, or 30 amps. For the length of conductor required that means at least AWG 10 size cable to preserve a voltage drop of less than 3%. AWG 10 is equivalent to about 3 mm. diameter, which is heavy, but not outrageously so. The worry with these old style ammeters is that their high current carrying cables are connected to the electrical system in the assumption that the meter will always be in series with a load, and that the current they carry will not, therefore, be so high as to damage the meter. Which is all very well except in the case of a short, when there could be a high enough current to not only fry the meter, but also melt the wire and start a fire.
Such a disaster should be taken care of on a boat by upstream protection, but the only thing between the battery and the ammeter is the circuit breaker, and it is primarily there to protect the main battery cable rather than the ammeter. The standard battery cables are sold here in the so called B&S (Brown and Sharpe) rating, and the most readily available is B&S 2, which is 32 mm.² in cross section, equivalent to AWG 2, and that can be rated to carry up to 240 amps, depending on its insulation and the heat of its surroundings. It seems odd then to use a circuit breaker which breaks above 30 amps just to protect the ammeter.
Some ammeters have internal fuses to protect themselves, but others use external low resistance electrical shunts. The ammeter in the latter case might really be a voltmeter, measuring the very small potential difference across the shunt (with the addition of a voltage amplifier in many cases), and expressing it in amps by a derived formula. These instruments are safer, as they only require small gauge wires and carry very little current. They are actually connected in parallel with the circuit instead of in series. If neither of these pertains then it is probably best to introduce a secondary fuse between the battery and the meter.
Although, to be realistic, the boat is not a car. The 12 volt battery will not be required to serve any cranking action, so there is no need for such large capacity battery cables as AWG 2. It should be feasible to replace them with AWG 10 and a 30 amp breaker, and then use the ammeter in series with big wires. Just be careful to protect the wire as well as possible, and avoid shorts.
However, the distribution panel I am using has a cumulative amp rating of 90 amps because of its six 15 amp circuits, and although I am not going to be using equipment which draws anything like that amount of current, it would be permissible to protect the system with a 90 amp breaker, or, if there were to be a 90 amp sub-main breaker protecting just the panel, the main breaker could be rated up to 135 amps. Under those circumstances, AWG 2 cable would be necessary.
I think that the best compromise is to work out what the maximum actual current draw will be in each circuit, allocate individual fuse ratings to them and add it all up. Even allowing a mark up for the next available fuse rating for each circuit, the total draw is still under 30 amps, and less than 20 amps through the panel. Since there will not be anything like the possible 90 amp capacity reached it seems silly to use cables and protectors which could cope with that demand. Instead, I shall use B&S 8 cable which is rated to 85 amps if a 10% voltage drop is permissible, and a single breaker rated at 50 amps. That will protect the cable, the panel and the ammeter all in one.
The 12 volt Voltmeter
The voltmeter is an altogether more useful gauge than the ammeter, and less complex in its operating requirements. Being in parallel with the circuit, it does not carry a high current, and does not need heavy cabling. The only consideration is where to connect it to the circuit. It needs to be as close (electrically speaking) to the battery terminals as possible, so as to measure the condition of the battery charge. Its run of cable from the back of the dash needs to be as short as possible, so the ideal place to join it would seem to be to the main negative and main positive buses, which are located right next to the gauges on the back of the dash. The only inaccuracy then would be the tiny amount of voltage drop occurring in the main battery cables, the circuit breaker, the bus bar posts and the ammeter. If you were concerned about that you could bring it in upstream of the ammeter, in which case you would be making the ammeter slightly inaccurate by allowing it to ignore the small current passing through the voltmeter. Given the coarse nature of both of these instruments, in terms of their usefulness to illustrate battery condition, any fiddling with voltmeter connections would be to guild a rather faded lily anyway.
However, ideal is not always practical, and in this case, to connect the voltmeter between the main positive and negative bus bars would mean that it would be working all the time. I only want it working when I am drawing power from the batteries, and then really only when the devices wired through the distribution panel are running. So the positive lead to the voltmeter has to be downstream of the start switch which activates the panel. Luckily, there is a three pin positive bus bar on the panel itself. The switch runs down to one of them, and the voltmeter can be wired into another one. The voltage drop through the switch and its wires is negligible because of the short length involved.
The Battery Monitor
Battery monitors come in a variety of guises, from the very sophisticated (and expensive) amp hour counters, to the simpler and cheaper glorified voltmeters. As Ariadne will never be far from civilisation in her voyages, I do not want to have one of the expensive ones, but I do need something more than a voltmeter. There are two meters which look to fill the bill here: Sevcon's "Powergauge" and Curtis' battery discharge indicator. Thy both can come as a combination instrument with engine hour logging if you want, and both appear to work by measuring the battery capacity in a narrow voltage range and by estimating the percentage of discharge which has occurred. They do not predict cruising time left or amp hours remaining, but I don't think I need that facility.
Unfortunately they both operate with LED displays, which means that they will look a bit out of place in the dash console, and also that they can be difficult to read in bright light, but they are not as obtrusive as blinking LED numbers such as you find on the panel meters, and they do come in 2-1/16" (52 mm.) diameters, which allows them to fit in with the 12 volt instruments I already have.
Pure battery state of charge instruments are cheaper than the ones which log engine hours as well, but they operate only on a single input voltage. Some of the dual instruments can be operate on either of two voltages if required. Since I am not yet certain of the voltage at which I will be running this boat there is an advantage in choosing the one of those dual instruments. The one I chose was the central one below, the Curtis 8., rated for 36 or 48 volts. So that is the end of my initial plans for a 24 volt system. All other equipment will now have to be able to cope with at least 36 volts, and preferably 48.
The Sevcon "Powergauge" (left) which also has an hourmeter, the Curtis with hourmeter (centre), and without (right).
With any of these
devices you run into a slight problem if you have more than one battery
bank. Ideally they need to be connected to the battery positive as
closely as possible, so as to avoid any voltage drop between the
instrument and the battery. The Curtis instructions are to connect it before
the switch for that reason. If that is to be done there would need to
be one monitor for each battery bank. If, however, you connect it after
the switch, and if the switch causes a significant drop, the monitor
may register a slightly less than full state of charge. But it will be
able to operate on each bank independently, or on both together.
There is another possibility in my case. As I intend to run the motor with both banks simultaneously I could connect the monitor to a single bank before the switch, and assume that its reading relates to the other bank as well, since they should be at the same level of discharge. But it is the assumption part that I feel uncomfortable with. If I could trust assumptions I would not need a battery monitor.
At present I am hoping that the use of a good quality selector switch, heavy (AWG 2) cable and short cable runs will prevent the voltage drop from becoming significant, so I will connect the monitor to the common post of the switch and see what happens.
There is another possibility in my case. As I intend to run the motor with both banks simultaneously I could connect the monitor to a single bank before the switch, and assume that its reading relates to the other bank as well, since they should be at the same level of discharge. But it is the assumption part that I feel uncomfortable with. If I could trust assumptions I would not need a battery monitor.
At present I am hoping that the use of a good quality selector switch, heavy (AWG 2) cable and short cable runs will prevent the voltage drop from becoming significant, so I will connect the monitor to the common post of the switch and see what happens.
A Voltage Independent, High Current Ammeter
Actually, the whole concept of a voltage rating for an ammeter seems odd to me. It is not as though the ammeter is offering much in the way of resistance to the circuit, and neither is the shunt, so why would the voltage make any difference? The current is what does the damage, and, since the current will be set by the motor controller, as long as the ammeter is rated to handle the correct current I cannot see why the voltage would affect it at all. But perhaps we are really dealing with a kind of voltmeter when we use shunts. They are, after all, connected in parallel. Maybe that makes the difference.
Anyway, the instrument cluster is first sketched onto a piece of paper to find a good arrangement, and then the holes are cut out of the fascia panel, and the size of the cut-out in the dash bulkhead is determined. With that done the panel is screwed into the frame, and further wire connections are made in the motor compartment.
Here, the 12 volt meter, ignition switch, horn button, cabin light and bilge pump switches are in place, and further holes are waiting for the 12 volt ammeter, and the two main battery meters.
The arrival of the
12 volt ammeter fills another gap. As I suspected, it is unshunted, so
needs
heavy gauge cables from the main circuit breaker, and on to the
ignition switch.
The ammeter is added and the
rudder compartment light is connected. A bit more wiring
can be done in anticipation of the deck hardware yet to go on, such as
spotlight, horn, etc. but this is basically the 12 volt system finished
until then. As soon as the ammeter is connected I will tidy up the
wiring and build a proper circuit panel which can be covered for
protection. I will also enclose the back of the instruments, as much
for noise reduction as anything, as the motor compartment is now open
to the cockpit through the bulkhead fenestrations; but it will also
help prevent trouble from any water which might be whipped around by
the drive belt.
The beginning of an enclosure for the wiring. The wing nuts could hold down a Perspex plate if a view of the wiring is desirable.
Once all this is working it has to be removed again so that the dash board can be varnished. The solid wood fascia panels have to be able to expand, so slotted screws are used where they are not floating in grooves. When it is all replaced and joined up again attention can finally be turned to the cockpit.
Slotted screws for the fascia.
The complete instrument bank with 12 volt ammeter and voltmeter above, and 48 volt ammeter and battery discharge monitor and
hour meter below them. The selector switch and the two circuit breakers are in the lowermost compartment.
The insertion of two circuit breakers
next to the battery selector switch shows how ugly they can be, so I
have made up a pair of cover plates for them out of Huon pine. In the
motor compartment the three devices are seen placed close together to
minimise cable lengths. To the left of the red battery switch is the
high current breaker for the main drive batteries, and to the right is
the smaller one for the house battery.
The door and cover panel still has to be fitted to the dash console when I get some extra wide mahogany. Until then there is more subdeck to be laid, and then the cockpit lagging can be recommenced...next month.
Top of Page
The beginning of an enclosure for the wiring. The wing nuts could hold down a Perspex plate if a view of the wiring is desirable.
Once all this is working it has to be removed again so that the dash board can be varnished. The solid wood fascia panels have to be able to expand, so slotted screws are used where they are not floating in grooves. When it is all replaced and joined up again attention can finally be turned to the cockpit.
Slotted screws for the fascia.
The complete instrument bank with 12 volt ammeter and voltmeter above, and 48 volt ammeter and battery discharge monitor and
hour meter below them. The selector switch and the two circuit breakers are in the lowermost compartment.
The door and cover panel still has to be fitted to the dash console when I get some extra wide mahogany. Until then there is more subdeck to be laid, and then the cockpit lagging can be recommenced...next month.
Top of Page
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Problems shows higher resolution shots as well.