I had last weekend off, Jo and I went to Melbourne for a long weekend, we left on Thursday and got back Monday night so I did not get any work done on that weekend, and the Tuesday was Australia day, but again I did not get any work done that day because of a combination of the festivities on the waterfront and then being just too hot to work in the afternoon.
I did get a start on fitting the 2 pumps into the toilet cavity. The hand pump has a handle that must protrude into the ensuite (when the lever is fitted) so this pump has to be against the bulkhead, and the electric pump must be in front of it (first pump off the toilet, so it pushes waste through the hand pump on its way to the tank and the hand pump pulls waste through the electric pump if it is used) and both of these pumps must be vertical or at 45 degrees to vertical at the most. Its a tight fit in and around the toilet base but it all fits in. I needed to take a notch out of the toilet base so that the hose does not chafe on it as it goes from the electric pump to the hand pump, and it is a tight fit under the duflex lid getting the hose from the top of the electric pump to make the sharp turn down again without kinking but I think I have managed that ok. So once I had determined that everything fit ok, I glassed the electric pump mount to the hull side and cut my hole for the hand pump and drilled the holes for the mounting of this. With any through deck/hull/bulkhead installation on a balsa core panel (or any core for that matter) you need to de-core the surrounds and back fill with filler. The cut out for the pump handle was easy enough, I cut 2 holes with a hole saw and used a jigsaw to make the sides straight and ran the router around then used a chisel to remove the balsa. With the bolt holes, I only drilled the hole through the front glass, leaving the back glass intact, then fitted an allen key into the drill and used this as a blade to remove the core from the inside of the drill hole making it way oversize. I bent 3 allen keys doing this but eventually got it done. I back filled it all and waited until the next day for it all to set before I could re-drill my holes through the filler. Its a tedious process but it absolutely must be followed.
I also had a bit of a dilemma this past week with how to plumb water into this toilet. The Lavac is a vacuum toilet, it has a vacuum pump (either electric diaphragm or manual diaphragm pumps, in line and either can be used) with a lid that seals to the bowl to create the vacuum and the pump both evacuates the waste and pulls cleaning water (either fresh or salt depending on your set up) into the bowl. I have chosen to go for fresh water in the ensuite (I will likely have both fresh or salt on the main toilet with a Y valve). The problem I had was that this toilet had to pull the water into the bowl. There is no control other than the suction of the vacuum pump to control water into the bowl, so a hose to the main pressure water pipe (and T join) that passes by the toilet on its way to the shower must be regulated in some way or it would empty my water tank.
The resolution of this issue had me change my mind about the best solution about 10 times in the space of a week and showed there are numerous ways to achieve the same outcome. The first method would be to run a separate water line back to the tank not via a pump so not under pressure and the suction of the toilets own pump would do the job. What stopped me on this idea, besides the fact that I had water flowing though a pipe just inches away but had to send another hose 5 meters to the tanks was that in order for the toilets vacuum to be broken and release the lid after a flush a vented loop is placed in the inlet water hose about a meter higher than the water line and as the pin hole vent in the loop lets air into the toilet it also allows the water in the hose past the loop to drain into the toilet leaving the water in the bowl ready for the next use. The height of the loop above the bowl will determine how much water is left in the bowl and the size of the pin hole in the loop also determines how much water is released into the bowl and the speed at which the vacuum releases but too big a hole and the vacuum is less effective in cleaning the bowl. The problem I face with sending a line back to the tank was that the height of the top of the water tank is higher than the highest point in the vented loop, so I would need to make one of the tanks a little smaller so that its top was below the height of the top of the vented loop. Otherwise, water would drain from the hole in the top of the loop until the height of the water in the tank and the top of the loop had equalized. Doable but I would rather not decrease the size of my water storage.
Next option was a device called a “demand valve”. They are used in scuba gear and are known to be available for irrigation and farming. But I could not find one anywhere off the shelf for my application and would need to have one made at considerable cost. What a demand valve does is it is a one way valve with a spring against the ball that stops the flow. The spring tension is adjustable so you can set it to the pressure you require it to release at. So for example the pressure my water system is pumped at is about 35 pound per square inch (psi) and the vacuum pump on the toilet also pulls at 35 psi so that is a combined 70 psi, 35 pushing against the spring loaded ball 35 pulling. So you set the spring tension to say 50 psi which is enough to stop the water from pushing it open, but once you flush the toilet another 35 psi is added and the combined 70 psi is enough to open the valve and let water through until the vacuum stops and the pressure is reduced again to the 35 psi and closes the valve. Simple. Problem is I could not get one anywhere and I tried the leading valve specialists in Sydney. They are made for high pressure applications and are expensive and I could have one modified (replace the spring) for an additional fee but still relatively expensive. Also as the next option shows, I would have to reduce the flow past the demand valve which may mess with the pressure from the vacuum which in turn could stop the valve from opening. So strike idea 2.
Next idea was a solenoid valve. Simple, cheap, easy to locate should I ever need to replace it. A solenoid is an electrically operated switch that had the valve closed in its native (off) state and opens when power is passed through it. I simply attach its power through the switch that controls the vacuum pump so that whenever the vacuum is operating the valve is open and when the vacuum is off so is the water. Seems a no brainer really. But (there is always a but) the toilet vacuum will only draw a liter of water during its 30 second operation but my water pumps pump 12 liters per minute so if run for 30 seconds would pump 6 liters into the flush which is a bit waste of limited fresh water. I could stop down the water hose reducing the flow but I am not sure what effect this has on the pressure or speed of the water entering the bowl and if it would spray everywhere in there as a result instead of swirl around the bowl as designed so I scratched this idea even though it would probably be the simplest. I also dont know what effect this would have on the vented loop, would water squirt out of the vent under pressure, if so I would need a way to get it out of the boat (another vent hole in the side of the boat?). As mentioned I cannot remove the vent hole or otherwise the vacuum would not release the toilet lid. Too many what ifs in that option.
Finally I settled on making a cistern. With a horizontal float valve inside a small tank behind the toilet I would achieve all of my objectives. First I would have a fresh water source for the toilet, collected by the toilets vacuum thereby only using the water amount the maker intended but I would feed the cistern from my pressurized water hose system already on hand. As the toilet used water the float valve would refill the cistern and shut off when it was full. I also have an air break between the toilet bowl and the water system both in the vented loop and in the cistern itself to prevent the migration of bacteria from the toilet into the water (which I am not sure would adequately occur with either a demand valve or a solenoid. The cistern also provides an additional benefit, I have to make the tank big enough for a lever arm float valve (although I have since found compact float valves I am evaluating) and as a result this tank will hold about 15 liters, so the toilet will flush a number of times before the float valve kicks in again to refill the tank. It means that if a person uses the toilet at night it wont make as much noise as it wont need to activate the water pump each time.
Having settled on the cistern idea I set about making the 8th tank I have made for this boat! (3 water tanks, well actually 1 big tank separated into 3 smaller ones, but I have previously made 4 waste tanks, 2 black 2 grey). As I am now an experienced tank maker, it only took me an hour to make the ply (I am using 5mm ply for this small tank) sides and bottom, I have still to cut the top. I have dry mocked it together to see that it all fit. Next I will take it to the irrigation shop to insure the lever arm fits into the tank, before making the top and glassing it all inside and out.
I gave the toilet set up a thick coat of white epoxy to finish it off. I still have to glass the separating bulkhead in which I removed for ease of access and I also need to fit some 25mm ply to the hull sides at a base for the lid to sit and be fastened to. I forgot I had to fit these before applying the white epoxy so I will strip some back to glass this ply in and recoat it once done.
I also got a start on vacuum bagging my polycore panels. For those that dont know, I decided on polycore, a honeycomb panel with glass each side as my furniture material. Schionning recommend and sell ATL Featherlite which is also a honeycomb composite panel but is a paper core, and can be bought as ready made panels or a kit. But I can buy and glass polycore myself which for me has 3 benefits. First I figure poly to be a better core than paper should water ever get into the core. Now in all likelihood this should never happen, but being surrounded by water you just never know. Second I can glass polycore bent around curves rather than having to kerf solid panels which saves a lot of fairing work and cutting gluing and glassing of the kerfs. But perhaps the most telling of reasons for me is cost. I have figured out I can make my own panels for about half what they cost prefabricated and a third of the cost of buying the furniture kit. The cost of the pre cut kit was $15000 when I bought my boat kit, the cost of enough prefabricated panels to cut my own kit is about $10000 and the cost of the polycore panels without glass, resin, peel ply and the fiberglass cloth and consumables in the vacuum process about $5000. But it does cost time. Time I have, money I dont. So the decision was out of my hands really.
I had already hand laid up some panels without the vacuum process. What the vacuum process does is pull the glass to the core much tighter, it also reduces the amount of resin used (although not by much on the first panels it seems) and ensures a more consistent finish. In fact I am making some panels with a smooth gloss finish by allowing them to cure against the table rather than peel ply.
First we precut 2 layers of cloth, 1 for each side of the sheet, a layer of peel ply, a layer of porous material that feels like felt but is man made, this allows the vacuum to migrate evenly all over the panel, and a layer of non porous plastic film, this ensures the resin is kept mostly on the job, some use perforated film so resin can migrate but we dont need it to move so used non perforated film and finally the bag, which is basically a sheet of clear plastic that will be stuck using double sided tape to the table, which we also pre applied around the perimeter.
Once you have a table (I am using a friends but you can make a table with a sheet of melamine and a vacuum pump) you wax coat the surface and polish it as you would a car, this ensure the panel releases once cured. We (my friend Dean who owns the table is helping me, Dean painted Nine Lives and did a fantastic job, he will probably be painting my boat if I can afford him when the time comes) then applied a thin coat of resin to the table before laying a layer of glass over it. I am using 600gsm plain weave cloth, over it and wetting it out. We then folded this wet cloth and put it aside whilst wetting the other sheet of cloth. With it wet and smooth on the table we sat a sheet of polycore over it and wet out its scrim (thin layer of porous material that feels like fabric to which the glass adheres) we then turned it over and placed it carefully over the layer of wet glass on the table as this will now be its final curing position. We then wet the other side of the panel out and applied the pre wet glass we had put aside a few minutes earlier. You have to get this glass down smoothly with no bubbles or kinks as I did when wetting the sheets out without the vacuum a few weeks ago. We finished the panel off by applying the peel ply again just as I did previously and smoothed it down removing any bubbles. To this stage this method is no different to the method I had previously used.
Now the layer of non porous non perforated plastic is smoothed down over peel ply and then the felt like material is laid over it and finally the clear plastic bagging material over it. Then you removed the protective layer from the double sided tape starting at the middle and moving toward the edges to minimize folds or bubbles in the plastic as it is glued with the double sided tape to the table. The plastic to table bond must be air tight for the vacuum to work. More double sided tape is applied around the hose fitting. Once it is all down, the pump is turned on and you look for leaks although listen for them is more accurate, and any that are found are repaired with more tape. Then you wait a day for the panel to cure naturally and deconstruct the layers. It is difficult to deconstruct without wrecking the plastic so you cannot re use it or the double sided tape but the porous sheet can be reused.