New Sailing Instruments for Peregrin
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The instruments which were on
board Peregrin
when I bought her were apparently the original instruments installed in 1984,
making them 20 years old. Three Datamarine
“Corinthian” instruments in large round cases, wind, depth and speed, had
been installed in the cockpit bulkhead to the right of the companionway.
Although they were of excellent quality, there were some problems. For one
thing, I wanted to interface them with my soon-to-be-installed radar and chartplotter, but a call to Datamarine
dashed that idea: these instruments had no NMEA capability, although they did
however interface and share information with each other. Another problem with the instruments was
the location- aboard Peregrin,
guests and crew often blocked the helmsman’s view of the instruments when
they got too comfortable; also, there was a large rectangular plastic box
which covered the backsides of the instruments in the head. I was always banging my head on that; the
instruments took up far too much space in the small compartment. In addition,
the plastic cover was by no means waterproof, which meant that taking a shower could lead to drowned instruments. We
removed the instruments (a nightmare!) and hired a fiberglass expert to fill
the 3 holes. The instruments were held by machined aluminum rings, secured to
the instrument case with setscrews, and by copious amounts of silicone. By the
way, I was very impressed with Datamarine’s service
department (508-563-7151). They have parts even for these old Corinthian
instruments, are staffed with very professional and knowledgeable
technicians, and will rebuild and recalibrate these old instruments at reasonable
rates. I had them rebuild the wind sensor (anemometer) which was dead when I
bought Peregrin,
and it came back as good as new. The
Corinthian instruments are still made today. They are beautifully made, with
turned aluminum cases, hand-wound coils, and hand-made circuitry. For my
purpose though, besides the lack of NMEA output, the main disadvantage was
the small size of the display for mounting on the sea hood. |
Peregrin’s Original Instrument Installation
Datamarine “Corinithian”
Instruments |
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The instrument cover
in the head Another
shortcoming of this plastic cover was that it would often fall off, leaving
all of the wires exposed. It was attached to the bulkhead with Velcro. As you can see, the previous owner of this
boat loved Velcro- he velcroed every thing that moved on the boat. In fact, Emilya and I spent several days removing Velcro from all
over Peregrin,
and we are still not done. There was
Velcro around the windows, on all the woodwork, etc., etc. We started to
believe that he was a major stockholder in the company which makes Velcro… |
The instrument cover in its usual position, falling to the
deck. |
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I have
always thought that instrument installations atop the sea hood or hatch
turtle above the companionway were an ideal location. Many newer boats have a molded-in panel at
the after end of the sea hood just for this purpose. It’s a good idea in my opinion for several
reasons: 1) the instruments can be seen from anywhere in the cockpit; 2) they
are protected from direct rain and spray by the canvas dodger, and 3) they
don’t intrude into the cabin and take up room. This
installation will only work, however, if you install instruments with very large
displays as you could be up to 9 feet away from the gauges. |
Instruments on the
Sea Hood of a J-120 |
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Raymarine ST60 Instruments |
We
seriously considered instruments from B&G, Raymarine (formerly
Raytheon), and Navman. I did a lot of research on
each type and brand, most of it on that most useful resource, the Internet. I
had learned that while many racers preferred B&G due to their precision
and flexibility, they were difficult to install and calibrate, and were
sometimes erratic in operation; they are also very expensive. I liked the Navman
series from |
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I know
that the “trend” these days is to mount instruments and even radar or chartplotter above the compass on the steering pedestal,
but personally, I don’t like it. If
you sit behind the wheel, your view is partially blocked. If you sit anywhere
else, you can no longer se the damn things. If you stand a lot behind the
wheel, I guess it’s OK. Even if
I had wanted to set up a pedestal mount, the guard around the Scanmar’s Whitlock steering pedestal doesn’t permit it
because of its unique 3 guard bar arrangement. Not all Scanmars
have this guard; some have no guard at all.
Note how there is one guard bar at the front of the pedestal. Also, 95% of all instrument pods sold in
the |
A Cluttered Steering
Pedestal
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I did
like the Navpod line of instrument housings. They are made of
a high-strength plastic such as is used in football helmets, and have excellent
gasketting to keep out water. I bought a model NP131RA
Navpod which comes pre-cut and pre-drilled for
three ST60 instruments. But how
and where to mount it? Emilya came up with the idea
of suspending the instruments over the companionway on some sort of
dowel. I refined this idea and
developed a simple solution which utilized standard stainless steel 1” tubing
and fittings from Taco Metals, available from West Marine, and a special
adapter from Navpod called the “PowerMount”. |
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The Navpod “PowerMount” is a
U-shaped bar which is designed to mount a sailboat-type Navpod
on a flat surface, such as the dashboard of a powerboat. It is supplied with two cast stainless
steel feet for mounting. Despite what
the photograph shows, the PowerMount is not
pre-drilled at all, which is a good thing.
I measured for the large hole to accommodate the instrument cables,
and for the smaller holes which were to be tapped for the mounting screws. I mounted the Navpod
as far up the U-bar as possible, and cut the bottom off the bar to keep the
overall height short; this is because the whole assembly had to fit under the
slanted window of the dodger. |
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Using
1” diameter stainless tubing and components made by Taco Metals (sold at West Marine),
including 2 “tees”, 2 elbows, and a 6’ length of 1” tube, I created a kind of
grab bar to span the forward end of the companionway. The long piece was cut
to 30”, and the two upright pieces were cut to 3-1/2” high. Here you see how
short the U-shaped PowerMount was cut to mount on
the bar. At this height, my head just
barely clears the bar as I descend the steps down the companionway (I am
6’1”). Also, the sliding hatch just
clears the bar. I didn’t want to make it too high because it had to clear the
window of the spray dodger. A large
hole was drilled in the horizontal tube where the starboard tee (on your left
in the photo) is mounted to accommodate the instrument cables. The cables pass through the tubing to the
left (starboard side) and down through a 9/16” hole in the deck centered in
the base or foot supporting the bar. This gives a clean installation with no
exposed wires. Here is
a closeup of the port side mounting foot. I used
the round bases which Navpod supplied with the PowerMount, because it is much wider than Taco Metal’s
rectangular foot. To mount the foot, I
drilled oversized holes in the cabintop, and
removed the balsa coring for ¼” from the edge using a dental pick. I applied masking tape around the foot to
protect the gelcoat, and then sanded the gelcoat directly under the foot; I also applied masking
tape to the foot itself. I “wet out”
the exposed remaining core in the drilled holes with straight West System epoxy, let it soak for 5
minutes, and then injected epoxy thickened with #404 high-density filler into
the holes. I gooped on a blob of thickened epoxy
tinted with white pigment and laid the foot of the assembled bar onto it. I
inserted the three machine screws into the holes while everything was wet,
and installed the aluminum backing plate I had prepared earlier; I made these
from 1/8” thick aluminum plates removed from salvaged industrial computer
hard drives. Within the span of 5
minutes, I tightened the bolts evenly and with very moderate pressure as the
epoxy oozed out everywhere. Yeah, it was messy but when it was dry, the whole
assembly was solid as a rock! Before
the epoxy dried, I removed the excess with a tongue depressor and made a fillet
to shed water. The hardest part was
making sure that the bar was bolted in a horizontal position while the epoxy
was drying. When
everything dried, I was left with a perfectly shaped and beveled base of
epoxy which is bonded to the boat, screws, backing plate and base. The
horizontal bar is rock-solid and doesn’t move at all. It actually makes a
nice grab bar to hold onto when climbing down the companionway. There
is no caulking in this installation. Water should not be able to enter these epoxied joints, but if any water did, it would only
encounter epoxy-sealed balsa or solid epoxy- no water can reach the balsa
core. This method of securing objects and hardware onto a cored deck is
described in detail on the West System website. |
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This is
how the starboard base of the bar is mounted.
The lintel of the door to the head had to be cut away with a chisel to
permit the instruments cables to pass over it. The cables will be hidden by the
vinyl headliner and enter the side of the wet locker, and then down to the
breaker panel and transducers at the mast and forward bilge. The
9/16” hole for the cables was drilled into solid epoxy after the whole
assembly dried. The
diamond plate peeking over the lintel is the backing plate for the new rope
clutches. |
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As the Datamarine transducers wouldn’t work with the Raymarine instruments, they had to be replaced. The
transducers are mounted just forward of the keel. The knotmeter
came out easily, but the flange of the depthsounder
needed to be pounded out and cut up with a saw because of the tenacity of the
Swedish polyurethane adhesive used to bed it.
Check out the thickness of the hull in this picture- it is a full 25mm
(1”) thick layup of solid fiberglass! No coring, just solid GRP! Everyone
in the boatyard was pretty impressed when they saw this hole. |
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Here are 2 views of
the new instruments on their custom-made pod mount. |
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