Tuesday, October 27, 2015

Low-Cost Depth Finder

Over aboard s/v Cay of Sea, Rick thinks about depth sounders, and replaces his. He keeps the original transducer tho, making this an easy project.
Before our July cruise, I installed the Hawkeye Depth Finder Model #D10D because my previous low-dollar depth finder (Uniden QT 206W) had failed. I’ve had a good opportunity now to compare the performance of both, and can definitely recommend the Hawkeye over the Uniden.

It seems that it is possible to pay up to $500 for a large format “sailboat” depth finder that mounts on the bulkhead. However, the availability of high-dollar stand-alone units is dropping off due to the popularity of consolidated multifunction displays for gps/chart plotter/depth finder/radar displays. And as I’ve looked at the market recently, I’ve noticed what seems to be greater selection among models and makers in the budget depth finder realm. I think makers of marine gear are understanding that the market for high-dollar gear has out priced the budget boaters, and they are now offering more products in the $100-$150 range, which is where I live as well. Don’t mistake this as altruistic behavior on the part of marine gear makers – I’m sure they are more motivated to not leave money on the table by ignoring this large group of boaters.

Regardless, the Uniden model represented a poor value with respect to construction and performance. I had this unit installed on my boat for about four years. After the first year, the display began to suffer from UV and weather-related damage, although it still functioned. The plastic display became frosty, the printed controls lost their readability, having faded in the sun. Finally, the display window cracked, which allowed moisture to enter the unit and make it unserviceable.
All-plastic components with no protective covering provided. It was a UV victim waiting to happen.
All-plastic components with no protective covering provided by the manufacturer. It was a UV victim waiting to happen.

Performance-wise, it was inconsistent at best, but I must say that whenever I absolutely needed to know the depth when approaching shoal waters, it gave me the right information. This may in part be due to my choice of installation. I installed the transducer inside the hull without drilling a hole, and I didn’t glue it to the hull with epoxy – rather, I bedded it in a blob of silicone. I am confident this degraded its performance to some degree. It would never give much in formation in waters deeper than 50 feet, and often in choppy conditions it would return error readings, I assume due to the amount of air passing underneath its location just behind the vee-berth, or the inability of the processor to keep up with excessive motion as found in choppy conditions. When that area was ventilated by air bubbles, I feel sure the device had a more difficult time determining depth. Additionally, it featured a gain, or sensitivity adjustment on the back side, which was extraordinarily touchy.

By comparison, the Hawkeye, while still mostly plastic, features a glass screen. While vulnerable to impact damage, it is nearly impervious to effects of UV radiation, which means that the screen will always be readable. Additionally, it comes with a protective cover which will shield the unit from the sun during the many days and weeks when the typical boat is not in use. I did not install the new transducer that was included in the purchase. Instead, I determine through reading the spec sheet, that both Uniden and Hawkeye used the same frequency and wattage transducer. Not installing a transducer spared me a lot of trouble and effort with the installation. I was also curious how the unit would perform with the old transducer.
New meter from HawkEye - fits the into the same diameter hole.
Depth meter from HawkEye – fits the into the same diameter hole as the Uniden model.

The Hawkeye returns depth measurement much more consistently, with many fewer instances of error reporting. It will also return more depth data in deeper water than the Uniden, although it also has more difficulty with depths larger than 50 feet. Again, my suspicion is that installation mode is a significant factor, and that an external placement would yield more accurate depths more often regardless of the depth of the moment. That said, however, the Hawkeye is significant improvement over the Uniden model. It is less sensitive to choppy conditions, returns readings very consistently in waters up to 50-60 feet deep, and has no gain/sensitivity adjustment. Apparently, the “new improved” algorithms for calculating data are indeed effective, and obviate the need for a gain adjustment featured on depth finders made by other companies.

So at about the same price point (approx. $100 for each) the Hawkeye is a much better value than the Uniden. I feel more confident with this unit on board than I have with any other brand during our ownership of Cay of Sea – and early on, we had a “legacy” Datamarine large-format (read expensive) depth gauge.

Tuesday, October 20, 2015

Transforming Current

Please welcome new contributors Sean and Louise, who live aboard their 52 foot one-off steel motor vessel, m/v Odyssey. For their first contribution, Sean offers a project which provides insight into marine electrics - a subject that can never have too much light cast upon it:
I'm perpetually behind on projects here, which I think is a condition of living on a boat, or perhaps just a condition of modernity. So I've been taking the time, on otherwise idle days at anchor, to whittle away at the list. I'm also perpetually behind on blogging some of the major projects I've already done, such as the great 24-volt conversion project that I've been promising to write up for over a year now.

In an effort to keep the backlog from growing, I thought I'd use some of the time to write up one of the most recent, considering weather has pinned us down here for at least another day or so. As with so many projects, this one has been on the list for a long time, but has bubbled to the top because recent events on board increased the urgency. I am talking here about fixing the main AC panel ammeter that tells us how much power we are drawing from shore or generator systems.

The ammeter, in this case, is part of the Blue Seas AC/DC circuit breaker panel built into the helm console, which is original to the boat and has been there, according to the photo record, since it was originally finished under the first owner's watch. While large and swoopy-looking and "custom" labeled, this breaker panel is actually an off-the-shelf item available in the Blue Seas catalog. The labels come with it on a big sheet of commonly-used circuit names, for customization by the installer.

Main AC ammeter (left) and selector switch.

As such the ammeters are actually pre-installed and pre-wired on the panel. The DC ammeter is hard-wired and measures all the current passing through the main DC breaker on the panel, while the AC ammeter is wired, along with the AC voltmeter, through a built-in switch that allows it to be switched from one AC leg to the other.

This is all well and good, but in this configuration it has, as far as I can tell, never, ever been able to measure all the current the boat is drawing on either leg. That's because there are some large AC loads that do not actually pass through the panel on the helm.

When we got the boat, the big culprit in this regard was the washer/dryer. It's located in the engine room and is the only 240-volt appliance on the boat. When the automatic transfer switch (ATS) was added during the last owner's stewardship, the electricians split the feed to that appliance off right at the ATS, running it through a separate tiny panel with a two-pole breaker for the washer/dryer and another single-pole breaker that supplied the engine room exhaust fan. Any current being used by those items was thus not included in the totals shown on the helm ammeter.

The engine room fan was moved off this arrangement early on, because wired in this way it could only be operated on shore or generator power. We don't typically run the generator under way, which is exactly when we need the exhaust fan, and so I moved it to a circuit connected to the inverter.

Having the enormous load of the dryer invisible to the ammeter was problem enough in itself. We often tripped the shore power breaker when using the dryer, until we learned just how much (or little) other load we could have on the system at the same time. We had to go by feel, guessing at the amount the dryer was using at any given moment, subtracting that number from the 50-amp shore supply, and keeping everything else under the remainder based on the panel ammeter.

The problem grew much worse when I completed the aforementioned great 24-volt conversion project. That involved, among other things, a new inverter/charger, which was best wired with a 120/240-volt, four-wire circuit, thus loading both legs of the input power, in contrast to its predecessor which was a 120-volt-only, three-wire load and was supplied by a circuit on the main helm AC panel.

The "new" main panel, in the engine room, a 120/240-volt 8-space "main lug" QO-series panel. Two-pole breakers feed the inverter/charger and washer/dryer, while two single-pole breakers feed the two sides of the former main panel at the helm.

The helm panel has no provision for 240-volt circuits (it's arranged as two separate 120-volt panels), which is probably why the washer/dryer was not wired to it, and why I could not wire the new inverter/charger to it either. Moreover, wiring such a big load through the helm meant the power would pass right by the load in the engine room on its way to the helm, through the panel, and then all the way back again, adding cable, weight, heat, and voltage drop.

So now we have two of the largest consumers on the boat -- the dryer and the battery charger -- that do not register on the helm ammeter. Even with the higher 67-amp capacity of the generator circuit, we still occasionally trip a main breaker, and this problem is just getting worse now that we are running air conditioning more often. And if we want to deliberately load the generator right to its limit, to reduce wet-stacking, we have no good way to monitor our progress toward that end.

The simple answer to all of this is to move the input for the panel ammeter down to the engine room, immediately after the transfer switch, so that it can see the full draw of everything on the boat. Easily said, but a lot of work to actually do.

AC current is measured with a device known as a "current transformer" (CT). Unlike most transformers you might encounter in a typical electrical system, which transform one voltage to another, a current transformer actually transforms one current to another, proportional, current. In the case of our ammeter, it's a 1,000-to-one ratio: a 50-amp current passing through the main feed is transformed into a 50-milliamp current into the meter, while, say, a 12-amp current would result in a 12-milliamp meter input. The meter pegs at 50 milliamps, but the dial is marked from zero to 50 amps.

Physically a CT is a toroidal coil, with the current-carrying conductor to be measured passing through it. It picks up the magnitude of the measured current by induction. The CTs in the Blue Seas panel are very small, just big enough to go around a 6-gauge wire with a bit of room to spare, making them easy to fit into the tight space for which the panel is designed. That also made them ideal for installing in the tight space of our new main electrical panel in the engine room.

One of the two Blue Seas CTs, still installed in the old panel.

The CTs that Blue Seas uses have their pair of lead wires molded in. Blue Seas has soldered the other ends of the leads to the selector switch. I cut the leads at about their midpoints. To extend these down to the engine room I needed about 35' or so of two-pair wire, but all I had on hand was some 4-pair CAT-5 communications cable. While I would not use untinned, coarse-strand cable like this for any critical application on a boat, for the meter it would suffice. I used two pair for each CT to minimize the resistance. At least the fine twist of CAT-5 will also minimize inductive interference in the signal.

CT relocated to new main panel in the engine room. The zip tie just keeps it from sliding on the wire.

After moving the CTs and splicing the wiring at each end, we fired up the genny for a test. While I was concerned that such a long run of meter wiring might impact the accuracy, a quick check with my clamp-on meter revealed that the helm meter is spot-on. We now have an accurate reading of the full draw on both legs up to a maximium of 50 amps, which is the limit when we are on shore power.

The generator is a 16kW unit, however, which means it is theoretically capable of producing 67 amps, and in practice has a 70-amp main breaker. Consequently, when running on the generator the 50-amp ammeter can and does peg occasionally, particularly on the leg carrying the battery charger, which by itself can draw up to 30 amps. For the time being, we avoid leaving the meter connected when running above 50 amps (the selector switch has an "off" position).

I'm not too worried about running the CTs at 30% above their 50-mA rating, as these are minute amounts of current. But the meter itself could be damaged long-term, and besides, we'd like to know exactly how much we are drawing even when we go above 50 amps. So I will probably devise a shunt that can be switched in when on the generator to divide the reading in half. I'll need to experiment to determine the meter's internal resistance in order to size the shunt.

We almost never trip breakers when running on the generator, which is large enough to run almost everything on the boat simultaneously unless we are running the dryer, which we try to run mostly on shore power anyway. So the meter is most useful in managing the more limited shore power feed, and for that, the 50-amp full-scale reading is perfect.

Tuesday, October 13, 2015

How To Make Holes In Your Boat

Making a hole in your hull is serious business, even more so if your hull is foam-cored. Jeff and Anne aboard s/v Pilgrim and in the midst of a complete refit demonstrate how it should be done...
We have added two new 1-1/2” thru-hulls above the water line.  The port thru-hull will serve as the discharge for the upper, larger capacity bilge pump (3700 G/H).    

The starboard side thru hull will act as a drain for the deck scupper.  We did not like the long hose run from the starboard scupper to the torpedo tube drain manifold.  We also wanted to rig a method for collecting water off the deck if necessary. 

Prior to drilling any holes we assembled the new starboard deck drain plumbing.
Test fit of new plumbing for starboard deck drain.  Note old drain hose at far right.
Test fitting the new plumbing allowed us to accurately mark the location for the starboard thru hull.   The port side fitting connects to a single flexible hose so identifying the exact location was less critical.

Since the location of the holes was marked on the inside of the hull, I began the drilling using a ¼” bit to drill a pilot hole from the inside out.  The ¼” hole matches the diameter of the hole saw pilot bit.  Next, I chucked a 1-7/8” hole saw into the drill and moved outside the hull.  Drilling the larger hole from outside allows for properly aligning the hole perpendicular to the hull and creates less dust inside the boat.
We drilled two 1-7/8" holes in the hull.
The Morgan 382, 383, & 384 hull’s have a foam core above the waterline.  This is the first time we have drilled large diameter holes above the waterline and subsequently our first look at the coring material. 
Close up of plug offers a glimpse of Morgan's construction techniques.
The hull is slightly over one inch thick… the outer fiberglass layer is 5/16”; the foam 9/16”; and the inner fiberglass layer 1/8”
Placing holes in cored hull’s or decks requires additional effort to ensure water never reaches the core material.  In smaller, fastener sized, holes this can be achieved by over drilling the size of the hole and then filling it back with epoxy.  Larger holes for plumbing fixtures require a different approach.

Using a small flat screw driver and a couple different styles of picks, we removed all the coring material within approximately ½” of the hole.
Foam core removed from the area around the hole.
The plan is to fill the newly created void around the hole with thickened epoxy.  So the next couple steps are the usual epoxy prep… 80 grit sanding, acetone wipe down, mask area...  We used a syringe to apply the epoxy and a plastic spreader to achieve a nice clean finish.
Filling the area around the hole with thickened epoxy.
After a couple days for the epoxy to fully cure, we returned to the project.  Using a #49 cabinet rasp and some 80 grit sand paper, Anne cleaned up any excess epoxy from the holes.  While I cut down the length of the threaded section of the thru-hull to properly fit the valve on the starboard side.

Prior to applying any sealant we dry fit the two thru-hulls and masked the surrounding area.  For the final install we used 3M 5200 sealant. Anne worked the interior and I the exterior.
New thru hull fittings are just above the waterline and five feet forward of the torpedo tube drain on either side of the hull.
We are still waiting on hose to connect the bilge pump to the new fitting on port, but we wasted no time installing the new starboard deck drain plumbing. 
New deck drain w/ option for filling water jugs installed.
Since the installation we have weathered a couple heavy rains.  The starboard deck scupper is performing much better with the new system.

What was that you said? 

Why yes that is a new battery selector and bilge pump switch panel in the image above.  I’ll post more info on that project very soon.

Tuesday, October 6, 2015


Drew from Sail Delmarva is with us today, with some insightful comments on jacklines:
Vertical Jacklines
Who says they all need to be on the deck? I installed a pair of vertical lines to deflect the genoa sheets away from the mast-mounted halyard winches (one on each side), around which they loved to foul during tacks. They are anchored to strong points and the line is 1/4-inch Dyneema, selected because I had it and it was non-stretch. At first I was concerned that the deflectors would be in the way, but I soon realized that they were handy holds and clipping points when working at the mast, much better than clipping to the mast base. I can even lean on the tether in rough weather, allowing for better 2-hand work.

Jackline and Lifelines
It is often said that using the lifelines as handholds is a bad habit. While there is truth to this on a monohull (the leverage on the stanchion bases is cruel when hauling to one side from the deck of a leaner), I disagree for catamarans. The difference is that cats do not heel and that most of the motion is vertical (it doesn't show in pictures, but cat sailors know they get light on their feet when pitching up wind). Additionally, my jacklines are relatively high at the beam, since they are secured to the hard top. Thus, the safest way to traverse the side decks between the hard top and the tramp is to hold the lifeline in one hand, the jackline in the other, and pull up. Not to the side, not push down, but pull straight up such that your feet are held firmly on the deck. There is little bending stress on the stanchions because the load is vertical, and the support is steady rather than surging roughly as the boat moves. Intuitive to a lifelong climber, something may lubbers and sailors have to be shown.

Probably just a catamaran thing.
Related Posts Plugin for WordPress, Blogger...