Thursday, April 11, 2013

Fischer Panda Cooling System Modification

Fischer Panda (FP) Generators are now cooled by fresh water and the sea water only passes through the heat exchanger and then out via the exhaust hose. BUT it didn't use to be that way. My  FP is around a 2001 model, 5.5KVA. In my FP the cooling is done with sea water, which first goes around the generator casing and then to the heat exchanger, before exiting via the usual exhaust method. The fresh water gets circulated around the engine and through the heat exchanger to get cooled from the seawater that has picked up a little heat from the generator casing.
You can see the heat exchanger situated underneath the generator in the picture below. I consider that poor design and changed my heat exchanger location which you can read about here and also here
To change my cooling system, I figured it was only a case of changing a few hoses over and I could have both my generator casing AND my engine cooled by fresh water and use the raw water only for cooling through the heat exchanger. Read below how I did it...
FP blurb about their water cooling.
First I removed the freshwater hose that went from the engine to the heat exchanger. You can see the fresh water hose coming from the pump (above generator belt) to a metal tube which then does a small bend and goes down and sits just behind the Johnson raw water pump. The removed hose is sitting in front of the pulley.
Next I removed the hose from the raw water pump which goes straight down to a pipe that dives under the motor to the generator casing.
The idea is to swap these two over. Fresh water will now go to the generator casing, and raw water to the heat exchanger.
In the picture to the right, you will now notice, the pipe that sat under the raw water pump has been moved to the right a little and hooked up with the fresh water pipe coming down from the fresh water pump. (pump not seen). I had to cut about two inches (50mm) off the pipe so that a hose will connect.

I had this 20mm pipe (in picture to the left) made for this change over.

In the picture to the right, you can just make out the curved pipe as it is now attached to the raw water pump and the pipe continues to the heat exchanger underneath the pulley.
Now, at the heat exchanger. the pipe that use to be fresh water is now raw water and should be connected to the raw water input at the heat exchanger.... AND the raw water input hose at the heat exchanger is now fresh water. Just swap the two over.
So, lets follow the path of the fresh water first.
From the fresh water pump, it goes down beside the crank pulley and dives under the motor to the generator casing. From the generator casing, the fresh water goes to the heat exchanger to be cooled and then returned to the engine at the header tank. From the header tank, it gets circulated around the engine and repeats the cycle.
Now the raw water.... It leaves the raw water pump and goes straight to the heat exchanger; picks up the heat and then exits via the exhaust. Just like the new FP's.
Finale hookup with generator belt back on.
  BUT, that's not the end of it. You might imagine that the generator casing may have some internal salt deposits. So, I first ran the engine up with fresh water to temperature and then after cooling down some, drained that water  away. I then did another run up using a product called "Salt-X". I mixed with water as per directions and repeated the draining of the fluid after cooling down some. This Salt-X is a produce for removing salt deposits in outboard engines and should be available in most marine Chandler stores. Finally, I did another fresh water run up and emptied that too, before using a ethylene glycol "antifreeze/antiboil" product. I'll change that in about 9 months time as well; to make sure all salts that remained have left the cooling system.
We also have a fresh water flush system for both our engine and Genset. As we get ready to shut them down for a while, we open a valve to our fresh water tank and close the sea cock. We let the engine run for a minute or two and this then flushes out the seawater from the heat exchanger. Thus prolonging the life of the heat exchanger. Then, after shuting down the motor, it is important to close that fresh water valve; otherwise, the next time you open the sea cock, it can back pressure to the fresh water and ruin your tank supply. It usually only happens once. :-D
All up, it took about 2 hours and a ten dollar item to complete. Antifreeze and Salt-X were extra costs; but you should replace you antifreeze once a year anyway. It's mostly for the anti corrosion properties that we use it.The engine actually runs slightly cooler, and with a trip up to the tropics soon, will be beneficial.

Tuesday, April 9, 2013

New HF/SSB Backstay Offset

Solace HF/SSB antenna cable ran down the backstay with a two inch off set as shown in the photo to the left.

The problem was, what to do about the cable as it ran pass the backstay turn buckle. Ordinarily, I might have fashioned something up to keep it tidy, but with the boarding ladder in the middle of the pushpit, people were constantly reaching up and grabbing anything to help themselves get aboard. Mostly they grabbed the back stay and HF cable. Eventually it became loose and pulled out of the deck fitting. (The ladder here is part of the pushpit, but when needed folds down and steps are formed over the railing.) Yes the back stay is right in the middle of the boarding area!

So I came up with another idea. I used two tubes. Pressure PVC  pipe; one 50mm and the other 20mm. I made end caps which can be viewed here.
for the 50mm pipe and some 32mm for some shroud antichafe rollers. (Another project)
The 20mm pipe has some strategically placed holes placed in the tube along one straight line. These were big enough just to fit my pop riveter. The length was assessed to allow the tube to move up the backstay to gain access to the turn buckle. The 20mm pipe was pop riveted to the 50mm pipe.
The back stay was marked for it's present tension and the turnbuckle was then undone.
The first end cap was placed on the back stay and held in place with some self amalgamating tape. A small rope was thread through the 20mm pipe by which later we would draw the HF wire through.
The combined pipe was then placed over the back stay and the top endcap engaged into the 50mm pipe. A small hole was drilled each side and a small SS screw inserted through to engage and hold the top endcap.
The bottom endcap sat on the very bottom part of the turn buckle, just above the swivel  The inside hole here is large because the "T" bolt that makes the bottom part of the turn buckle is larger in diameter than  the backstay cable. This bottom end cap does not slide up and down.
The tubing was slide up the back stay and the turn buckle re connected and tensioned. The top wrench, which holds the top swage at the turnbuckle and prevents the backstay from twisting, supports the tubing while tightening the turnbuckle. Once the turnbuckle is tensioned and the split pins applied, the tubing is allowed to to slide over the turnbuckle and engage the lower endcap. The same two holes with screws to secure the endcap were applied to the lower endcap as done for the top endcap.
The HF cable was then threaded through the 20mm tubing and attached appropriately.

Hint. As you undo the HF cable above the backstay isolator, place a small rope around the isolator so that later you can have a companion pull down on the back stay, which will help with re connecting the turnbuckle. Also, if you buy pressure PVC pipe, it may have black writing on the pipe. A paint thinners on a rag usually wipes this off so you have a nice white tube.
How to stop the pipe from turning? I'm trying some heavy self amalgamating tape at the bottom end, which at the moment has a little give, but seems to hold everything in place. Another method might be to place a bolt through the 50mm pipe and through the turnbuckle openings.
To access the turn buckle again, it is a simple case of talking out the small screws at the bottom endcap and sliding the combined assembly (minus the bottom endcap which stays in place) up the backstay to gain access.
In the photo to the right you can see that there is just enough room to slide the 50mm pipe up the backstay. The HF wire is cable tied to the isolator and gradually moves away from the backstay until it enters the 20mm pipe.
The holes which were made for the pop riveter will later have some 20mm rubber bungs inserted to tidy the whole thing up

Monday, April 8, 2013

Battery Replacement with Balanced Interconnections

Solace has three battery banks. One bank is in the forward cabin and has a long run of wire. I added two batteries to that bank (#3) in  2007 because we were going cruising and needed the extra battery capacity. I had no other place to place the extra two batteries and hence the unequal array of batteries. But there was nothing I could do about that. You have to put the batteries where space dictates.
It is now time to change all the batteries (my oldest battery is 12 years old) and it doesn't pay to mix old batteries with new. In changing the batteries I intend to fix some of the (lack of) balance in the system.
One of the things I have done, is to have all three banks combined all the time. There are reasons for this; namely the bigger the bank and the smaller the discharge percentage before recharging, the more recharge cycles one will get out of the batteries.

Here is a diagram of my boats wiring diagram for the three battery banks I have. I have been long aware that the draw from the 3 banks, which are always combined together is not balanced and the charge to the batteries is also not balanced. I'll try to explain.

A common method used to connect batteries, and then feed the load, are all taken from one end, i.e. from the end battery like in the diagram to the left.
The interconnecting leads do have some resistance. It will be low, but it still exists, and at the level of charge and discharge currents we see in these combined batteries, the resistance will be significant. In fact, it will have a measurable effect.
Often the batteries are linked together with heavy cable around 35mm. 35mm copper cable has a resistance of around 0.0006 Ohms per metre so the 20cm length between each battery will have a resistance of 0.00012 Ohms. This, looks like it is nothing to worry about. But add to this the potential 0.0002 Ohms for each connection, such as cable to crimp, crimp to battery post, we find that the resistance between each battery post is around 0.0015 Ohms. Plus the batteries themselves have an internal resistance of about 0.02ohms
So armed with that data we can then look at each battery to determine the draw.What ever we draw from this battery bank (say100amps), most would think the draw is evenly divided (25amps) between the four batteries. Least that's what we may think. But that's not the case; when you take the internal resistance and add that to the cable resistance the batteries supply a different amount. Without going into the calculations it would look like this
First battery draws 39.5 amps
The next battery up draws 26.2 amps.
The next battery up draws 20.4 amps.
The top battery draws 17.8 amps.
What can we deduce from these numbers? Clearly, the first battery is working harder than the last, but because the first battery looses capacity quicker, the other three will start to take more of the load. Because of the unbalanced nature of this battery bank, the bank as a whole will age faster than if it was properly balanced. Also the charging input works to the same inbalance; the first battery will receive more charge than the last battery in the line.
So how do we change the battery set up to give a more balanced draw and charge. Look at the next picture

What has changed in this diagram is that the main feeds to the rest of the installation are now taken from diagonally opposite posts.
It is simple to achieve but the difference in the results are truly astounding for such a simple modification of moving one of the connecting leads; everything else in the installation remains identical.
The results of this modification, when compared to the original numbers are shown below. It was simply done with one single connection being moved.

The bottom battery provides 26.7 amps of this.
The next battery up provides 23.2 amps.
The next battery up provides 23.2 amps.
The top battery provides 26.7 amps.
Clearly these numbers are better than those shown in the first example. But we can improve on this too.

One final method I'll present here gives a complete balance to the bank

It is  quite simple to achieve but requires two  terminal posts, by which the short leads, all which must be of the same length and size, are connected to the terminal posts.

The difference in results between this and the prior example are much smaller than the differences between the 1st and 2nd (which are enormous) but with expensive batteries it might be worth the additional work.

And here's what I have changed to (picture below). Simply, I have changed the interconnections for the batteries on Bank 3. Unfortunately, I can't do anything about one bank (#3) being so far from the other two.

  • When motoring the alternator can supply to Bank 1,2, and 3, individually or combined. Because mine are usually combined, Bank 3 will lag behind in charging compared to Bank 1 and 2 (because of the small resistance in the long run to Bank 3's batteries). Solar and wind will not charge because my set point for the alternator is set higher than the wind/solar and therefor the wind/solar see's the batteries as being charged and dumps their load.
  • Alternatively, when motoring, I can have Bank 3 turned off and have the alternator charge Bank 1 and 2;  OR turn off 1 & 2 and charge #3.
  • When at anchor with no motor going, wind/solar charges all three Banks.. I have the option of turning Bank 1 and 2 off to give Bank 3 a faster charge.
Now all I need now is a method to remember to switch banks on or off while on the go.

Sunday, April 7, 2013

Chain Stripper Modification

Bent stripper compared to new stripper
Last year I had a guest on board who was trying to be helpful and undertake some of the chores on the boat. He was going through the anchoring process and while anchoring, I (he) found a deficiency in my capstan while easing out chain as one puts on the snubber.
Normally, when bringing in the chain with the capstan, a stripper is in place to ensure the chain comes off the capstan and goes down the Hawse pipe. Otherwise, it can get caught in the gypsy (wildcat in the USA) and wind up the chain around itself. Easing chain out, say when anchoring, the weight of the chain is usually sufficient to take the chain of the capstan gypsy. But in my case, my guest was not aware of the potential issue and as he eased the chain out while holding tension on the snubber line, the chain stayed in the gypsy and bent the chain stripper on the opposing side. You can see the bent stainless stripper above.
Plastic compared to SS
We were in the middle of "nowhere" and there was no way I could straighten that stainless. So what to do? I used one of my wife's "polyplastic" chopping boards and cut it up to make a plastic, but temporary chain stripper. While getting everything ready, including a cardboard template, I decided to design it so it was able to strip the chain whether it was coming in, or going out. I used both hacksaw and Dremel for fashioning the plastic stripper and the thing worked so well, it stayed on for the whole cruising season (6 months). I improved the cardboard cut out a little and had a piece of 6mm stainless laser cut when I went home.
Plastic stripper in place

New SS stripper to replace plastic in place