Sunday, April 20, 2014

Keeping An Eye On Things: A Boat Monitoring System

It is a good idea to monitor boat systems in order to detect problems before they become major problems. Collecting basic information like engine operating temperatures, refrigeration system temperatures, and battery performance information are a few examples. It is best to gather an information baseline when everything is operating correctly so that abnormal readings are easy to identify. A manual method of recording the information is easy - just record the measurements on paper. Transferring the information to a spreadsheet makes it easy to display as graphs, making it easy to spot trends that may indicate a pending problem.

IR Thermometer Gun
We've been recording engine temperature readings for some time, but only doing it on a sporadic basis and putting the data into a spreadsheet. Even with the sporadic measurements, we've developed a baseline that allows us to determine if there is a problem with one of the engines. (Note: We recommend that everyone capture the data to create a baseline of engine operation. An IR thermometer isn't terribly expensive ($40-$90 on Amazon) and is a great diagnostic tool. Put one on your gift list for your spouse/SO to buy for you.) We have a remote temperature sensing system to show us the refrigeration system temperatures (freezer, fridge, compressor housing). But there is no historical information stored that allows us to determine if (or when) the system is experiencing problems.

My "day job" is computer network design and monitoring, which requires automated systems to collect the large volume of data. Applying those same principles to boat monitoring led me to automate data collection using a single board computer known as a Raspberry Pi. The other attractiveness is that it is a cool project. I'll refer to the Raspberry Pi as "RPi" in the rest of this post. I'm starting with temperature monitoring and will add other features as I go.

I plan to monitor the temperatures listed below. The engine temperature readings are the same as what we've been manually monitoring. We have the Oregon Scientific Clock Weather Forecaster BAR206A and THN132N Wireless Temperature Sensors for monitoring the refrigeration system, but have not recorded measurements. Manually recording refrigeration system temperatures would be useless because of the changes in temperature after the door was opened. Automated temperature recording would let us know how long it takes to return to the desired operating temperature.

Raspberry Pi with Pi Plate Development Board and Acrylic Enclosure
* Ambient air (clipped to the back of the DC panel)
* Freezer plate
* Freezer mid-rack
* Refrigerator mid-rack
* Refrigeration compressor cabinet
* Port and Stbd water heater
* Port and Stbd air conditioners
* Port and Stbd engines
  - Alternator frame
  - Exhaust mixing elbow
  - Raw water inlet
  - Oil pan
  - Cylinder head (one sensor - the ideal would be one next to each injector)

This photo shows the RPi with the attached Pi Plate development board in an acrylic enclosure. The is the fully assembled unit. It measures 6in x 3in x 1.5in. In the foreground is one of the waterproof temperature sensors, which is attached to the white cable that connects to the board. My prototype has three sensors, which I've labeled freezer, fridge, and compressor.
Sample Hourly Temperature Graph

I have a script (a small computer program) that periodically creates graphs of the collected data. All three temperatures are shown on one graph. I'll wait until I get on the boat to refine what types of graphs I want.

The Details

The temperature probe is the DS18B20, which is available in a waterproof version (we'll see, they are probably only water resistant) from sellers on Ebay (search for "waterproof DS18B20"). I found that connecting the DS18B20 using all three wires (Ground, Data, +3.3v) worked the best. I used a "Pi Plate" development board for connections between the RPi and the DS18B20. All sensors can be connected to the same 3-wire bus, which I'll snake around the boat to all the locations. The operating system supports up to 10 temperature sensors. That's not enough for my purposes, so I'll have to generate a new kernel to support many more sensors, probably 30.

The Internet contains many examples of interfacing the DS18B20 temperature sensor with the Raspberry Pi.

I am using the Round Robin Database (RRD) to store the sensor values. RRD is typically used for network management functions. It is very simple and does a good job of storing and displaying time-series data. The current implementation stores a month of samples. I have plenty of storage space and RRD is very efficient, so I'm planning to increase it to several months so that we can see longer term trends.

12V to USB Power Adapter
I needed a way to power the RPi on the boat. The easiest solution was to modify a 12V to USB adapter. This photo shows the adapter with two new wires soldered to it. I wrapped the modified adapter in heat shrink. The red wire connects to an in-line fuse for connecting to the boat's 12V system.

I'll be publishing the scripts that I've developed for this system so that anyone can make their own and can contribute to it.


Sunday, April 6, 2014

Summer Refit Projects

During the summer of 2013 we had LUX hauled to address several projects on our TODO list:
* Clean the hulls and fix multiple gelcoat dings
* Replace the rear, inboard U-bolts with cleats
* Re-bed the stern rubrail
* Replace the port seacock with a larger seacock and manifold for several raw water consumers
* Complete service of the saildrives and props
Unfortunately, we started the work just as a major heat wave hit the Baltimore/Washington area. It was over 100 deg F during the middle of the day. We would start work by 7am, break for lunch around 11 to cool off in the marina lounge, then work until about 2-3pm. One of the nice things about a cat is the substantial shade under the bridge deck. By the time the middle of the afternoon arrived, we were drained. The weather broke after a week and we were able to put in longer hours. Even still, it took almost three weeks to accomplish everything.

Brown Stain Removal

LUX had a big, brown stain on the hulls, particularly in the aft, inboard areas, just below the rear part of the bridge deck. Trips up and down the ICW, with its typically brown water, had taken their toll. We found that Marykate (or Marikate on some web sites) "On & Off Hull & Bottom Cleaner" did a fantastic job of removing the stain. This stuff is an acid that is not environmentally friendly. Rubber gloves and some care is required to protect our skin and to only apply it where needed. See the MSDS sheet for handling directions. You can keep a can of soda or a box of baking soda handy to neutralize the acid, should you have an accident. Wetting a cloth with On and Off and wiping down the stains quickly removed them. We followed with a wash and wax. The hulls now look great.

Aft U-Bolts

U-Bolt Holes
The Leopard cats all seem to have big U-bolts installed aft and inboard of the hulls. They useful for cross tying the boat in a slip. But it requires a bit more time to tie a bowline through the eye of the U-bolt and it is nearly impossible to adjust the line on the boat. We wanted something that allowed us to quickly belay a line. We also wanted to seal the holes to prevent water ingress, as evidenced from the water stains on the inside of the hull. Fawcetts Marine Supply store in Annapolis, we found the Sea Dog Line 10-inch cleats (SDL 041610) cleats. The arms are long enough to securely hold our 5/8-inch diameter dock lines and allow us to quickly belay and adjust the dock lines from the boat. In addition, the open base provides hand-holds when we're in the water at the stern. We filled in the old U-bolt holes with thickened epoxy and finished the outside with new gelcoat. The inside space is so tight and uneven that we couldn't install big backing plates, so we used large fender washers as backing for each of the bolts. Since there are now four bolts instead of two, we feel that this is acceptable. Instead of caulk for waterproofing, we used gray butyl rubber. The butyl rubber only forms a water bond, not a mechanical bond, which is fine for this application. This upgrade took care of one source of water ingress into the engine compartment.

Stern Rub Rail

Old Hull-Deck Caulk
The big job was re-bedding the stern rub rail. The L40 has separate engine compartments aft, using saildrives for propulsion. The bilge pumps in both compartments have been periodically running while under way and there is evidence that one source is from the stern railing and perhaps the hull-to-deck joint at the bottom of the sugar scoop. The bottom step of the sugar scoop is under water when under way, so we wanted to make sure that we had a good seal.

Hull-Deck Joint Prepared
It was easy to remove and clean the old rub rail. What took the time was to clean up the hull-to-deck joint. It looked to us like the joint was filled with automotive repair putty. It was relatively soft and brittle, easily breaking into chunks. We used a combination of a Dremel tool with 2-inch heavy-duty cutoff wheel and a vibrating cutter to reach into the filled space between the hull and deck to remove the putty. (I hesitate to call it 'caulk' because of its brittleness.) We also had several sections of fiberglass and gelcoat that needed to be stiffened or rebuilt. The fiberglass was repaired with West Epoxy and additional fiberglass mat. The hull-to-deck joint was filled with 3M 5200, with the intent that the joint should be strong and well sealed. Our reasoning on using 5200 is that this joint should never come apart for any reason.

The stern handrails were also re-bedded during this process. It took some re-bending of the railings to get them into the right shape to match all the attachment points. We needed a couple of 6-inch extensions and a universal drive on the ratchet socket wrench to reach all the way to the aft attachment point. Even with the extensions, it required weird contortions in the engine compartment to get the nut started on the railing's attachment bolt. This is a good opportunity to enlist the assistance of a small, flexible crew member or boatyard worker. We used 4200 on the seal around the attachment points and found that adding the caulk after the nut was started helped to keep the 4200 from getting on everything while fitting the railing to the boat. The process of re-bedding the aft railings can be frustrating. We had to experiment with which attachment point to start first. 

Cleaning the Rub Rail
The rub rail was cleaned with 3M Compound and Wax, which we've found does a good job of removing various marks and goo. We installed the rub rail with a seam of 3M 4200. The stainless hardware was reinstalled and it looks like new.

The swim ladder was also re-bedded, which included sealing the bolt holes with epoxy. We dug out the old balsa around the perimeter of the hole and filled it with epoxy, and re-drilled the holes before re-installing the ladder.

Port Seacock

Hull Construction
The L40 has a raw water thru-hull under the floor board of each forward cabin to supply water to the toilet. We had already installed a T on each to supply water to the air conditioner on each side. Since we are planning to install a generator, we needed a larger raw water source so that there was sufficient water flow for both the generator and the air conditioner at the same time. This is a tricky install because there isn't a lot of room between the bottom of the floor board and the hull. We used a piece of 1/2-inch marine plywood, shaped to mate with the curve of the hull, as the backing plate for the new thru-hull, a Marelon sea cock. We had to look around to find a raw water strainer that would also fit in the space under the hull. We used a Groco multi-port manifold <> to provide connections for the toilet, air conditioner, and generator.

Seacock, Filter, and Manifold
One of the interesting things we learned is the hull construction where the thru-hull is located. It is solid fiberglass, about 5/16-inch thick. We think that this makes it essential that a good backing plate be used for any thru-hull replacement. It is surprising that there is no backing plate on the original sea cocks (which are actually just ball valves).

Saildrive Servicing

Saildrive Servicing and Boot Install
Mike undertook the task of complete servicing of the saildrives. We found one of them had water ingress - the oil was a milky consistency. He checked the bearings, researched the proper oil to use (10W40, specified in a service bulletin), cleaned out old barnacle shells, mounted the rubber seals at the hull, and took the props to Black Dog Props to get realigned. A charter customer had backed over the dinghy hoist lines and bent the port prop. All the work was worth it. The vibration that we previously experienced at 2000-2500 RPM disappeared.

Completed Saildrive