Holding Tank Level Monitor

 I wrote previously about Gobius Tank Level monitoring. You can review that blog here.
On my forward holding tank, there is no way to easily place an inspection hatch for level monitoring (as per my previous blog). That is because to get at the tank, I have to remove a heavy mattress and covering board to see the tank. We also use the forward berth a lot, to store our extra equipment and sometimes supplies. So it can be a real hassle getting to the forward tank.
We use to empty the forward tank whenever we emptied the aft tank; but that was a
waste of tank treatment if the tank was say only 1/4 full.
So for me the solution lay with this new tank monitor device. You can see in the three photo's, the installation of the three main components of the device. The level indicator was placed just over the head electrical switch. The "computer" was placed on the side of a locker, next to the holding tank and the sender unit on the side of the tank as indicated in their web site tank calculator. Everything was easy except the sender unit. I followed their direction to the letter, but it would not stick. Sanded level, made sure tank surface was above 20 degrees C, and wiped surface prior with their special towel. Didn't stick! They supplied a spare sticky patch with the kit, so I tried the spare. Still no stick! So I wrote to their support email and two days later got a reply. The insinuation was that I had not followed with their directions

but they would post a new sticky patch out to me. Well, that wasn't going to help much, being on a boat, "cruising the world". So I took matters into my own hand. This they didn't recommend, but I did it anyway. I sanded the sticky patch that wouldn't stick so that it had a rough surface. Next I applied a very thin layer of 3M 4200 and applied the sender unit to the tank. I had duct tape ready to tape this unit to the tank until the 4200 set up. Next morning, the sender unit was attached "rock solid" to the tank. I proceeded to change the default settings and calibrate the unit as per their directions. And the unit works great. I may at a later date put a buzzer in the analog circuit which is detailed in their instructions. In the mean time, the 3/4 warning light comes on when the tank is 3/4 full. You can add extra sender units to have a 1/4 and 1/2 level light as well, but I'm very happy with this at the moment.

One Stop Shop

Here's a web site that seems to sell almost anything. They claim over 490,000 products. Great stuff for your boat project and that hard to find piece of hardware. Take a look here

Holding Tank Level Inspection Window

I have a holding tank gauge with sender unit for some years now, but have never enjoyed removing the tank sender unit for a clean from time to time. Even when the unit is especially designed for black water, it would eventually clog up and need to be cleaned. My aft holding tank was easily accessible, so I decided to put a view port in so as to "see" the level of the tank. You can view the old sender unit here at WEMAUSA. It is the one on the right.
First, I had to design my window and decided for simplicity sake, to use a beckson hatch with a clear screw lid. These have a "O" rind for sealing. To this I mounted it on a half inch piece of ply cut to shape and given 3-4 coats of clear epoxy. Screws were mounted so as not to protrude through the other side. I also didn't want screws to go through into the holding tank and the mounting wooden plate adds some stiffness to the tank. Why wood instead of GRP? I like the idea of being able to reverse anything I do and the wooden base plate would (no pun intended) be easier to cut off.

After removing the sender unit, which was now showing signs of corrosion, I had to remove the screw in adaptor. This had a "C" shaped backing plate, so I lassoed it with a cable tie before undoing the last screw which held it there. I was then able to remove the backing plate with some ease.

I marked out the location of the new base plate, takeing out the old hole. But it was somewhat off centre, so to help with the hole saw, I screwed on a scape piece of wood and held it in place with screws through the piece of GRP that was going to be discarded.

To the right you can see how easy it is to drill a new hole where an old hole already exists.

Next, I sanded the paint off with a Rolok sanding disk.

The back of the backing plate was also sanded. Then I mixed up some epoxy with a silica type "Glue" additive to give a peanut butter viscosity. This was applied to the tank and then the backing plate pressed into the mix. Some squeezed out to the inside and I was able to get this before it fell into the tank. (wearing rubber gloves). The out side was smooth filleted with just a finger and left to harden overnight.

Finally the beckson hatch was bedded with 3M 4200 to the base plate.
And the finished inspection/view hatch to the left. It helps to shine a small flashlight up to one side of the clear hatch to get a better view of the level. Plus, now if I want to, I can put a hose in the tank to give it a wash out from time to time.

A Lesson in Troubleshooting

I'm writing this up after almost a year after the incident. I never wrote it up originally because I was some what embarrassed about it all, but after reading an article by sail-delmarva, I have thought it my be of use to some of you "troubleshooters" out there.

Last year we installed a class "B" AIS transponder and after some issues with it not working, we left Picton, New Zealand and eventually made Fiji. The unit worked fine and we loved seeing the targets on our MFD. (Furuno AIS and Furuno MFD). The original reason it didn't work was because the unit was set to "USA" instead of "International". Something to do with the frequencies AIS works on.  I checked the installers manual and all the frequencies are the same, except for about two. I couldn't understand why that setting made a difference, but it did. Perhaps somebody out there can tell me why.

Anyway, in Fiji, I noticed we were no longer picking up ships which should be displaying as an AIS target on our MFD. So, I check the AIS unit and notice the power light is now flashing green and none of the other LED's were on. I said to my wife, "I'm sure that Green LED used to be a solid Green".
I checked the manual and couldn't find anything about a flashing Green power light, but figured that with the other LED's not lighting up there was something wrong with the unit. I also hooked up my computer to it, because it has a self test, and you can change the settings with the computer, but was unable to get a connection.

So, as per sail-delmarva suggestions in "Lessons in Electrical Troubleshooting", I took out my multimeter and checked the voltage supply. The batteries were a little down but I showed 13.2 volts. Almost the same as what was showing on my house bank monitor.

My wife was making a quick trip back to New Zealand (by plane), so I had her take the whole unit back to Auckland NZ for a test etc. To my surprise, I get a phone call from NZ to say the unit tests out OK. Fine, bring the unit back.

Now this is where it gets interesting. Sail-Delmarva says 

1. Never assume the previous owner didn't set you up. He did.
2. Always trace the wiring

I reinstall the unit, and that dammed light is just flashing back at me again. Damm! I check the voltage again. 13.4 volts. What could be wrong?

I  take the unit out and now hook it straight to the battery. Yes, it works!!!
Put it back in place  and the light is flashing again. Voltage fine. Hmmmmmm
Check circuit breaker voltage. Fine. BUT now I have a little alarm go off in my head.

I vaguely recall having switched out a circuit breaker some time back because one had been playing up. At the time I switched it with one that wasn't being used, and I remember thinking, I'll change that faulty circuit breaker sometime when I can get into my spares.

I change the circuit breaker, and all is solved. I don't know why the circuit breaker seemed to test out fine with the multimeter, but there was something the AIS unit "picked up" and wouldn't work due to the fault in the circuit breaker. Can anybody tell me why this might be?

The issue was, when I had installed the the AIS, I put it to one of the remaining circuit breakers that was not in use. This was of course, the faulty one, and unknowing to myself at the time, set myself up.

So, my lesson is, if at first everything checks out fine with the multimeter, try hooking the device straight to battery to see if it works. It seems the electronics of today are getting so much smarter and can detect issues on an electrical supply and turn themselves off to protect their circuits.

They do say " a stitch in time saves nine". I should have replaced that circuit breaker at the time of the fault, or put a note on it.

Clean cuts on Plywood

Mark Corke has shown us a wonderful tip for cutting ply. Go on over to his web site to get the full blurb.

Mark says.....  The picture shows some cuts that I made in half inch thick marine ply and as you can see they are perfect straight from the saw. The blades that I use for this type of cut is the Bosch 101AO, which have needle teeth not too dissimilar to those found on Japanese pull saws. With the pendulum action turned off they really are the nuts with almost no tear out even when cutting against the grain on the face laminate. A quick trawl of the internet shows these blades can be had for around $8 for a pack of five which considering the little cleaning up you have to do once you have cut out the component is money well spent.