Scott pictures last pdf
This is background on what I’m trying to accomplish
I've installed four pumps and their associated plumbing. Because of the configuration I want to achieve with the port and starboard ex-current nozzles as close to the tail as possible necessitates that the two forward pumps excurrent nozzles had to be placed higher than in the previous 4 ft jet nautilus model. This should not change forward performance. It's still possible to lower the port and starboard excurrent nozzles but this would mean more plumbing external of the shell. So for the time being I'm trying to keep things internal as possible.
Although I have a lot of experience and it took me long time to workout all the variables on the first 4 ft there's no guarantee that I'll get it right the first time on the second version.
As I was anxious to try out the pump with the higher voltage battery I temporarily connected the 14.4 V cordless drill battery to one of the forward pumps. To keep a supply of water I simply filled the bottom hull section using a garden hose. To my surprise I found that the pump would empty the hull (in about one or two seconds) even with the garden hose fully opened, the discharge pump exceeded the capacity of the garden hose at full open.
I wanted to install four cordless drill batteries. These battery packs with their awkward shape and size would be hard to fit in the shell even if I could waterproof them. So I took out the Ni Cad batteries and encased them in fiberglass to insure waterproofing. The other 4 foot used sealed batteries so there was no need to waterproof. There are 48-1000 milli-amp cells that I took out of the four cordless drill battery packs. This should give me decent runtimes. Also unique to Ni Cads is that their discharge voltage remains high to the very end. The sealed batteries drop voltage proportionate to the level of charge. So that cuts into your runtime.
I had to take apart a charger and rewire it since the original battery packs are no longer. Since the charger was designed to charge only one battery pack at a time a total of four at once may generate too much heat. In that case charging may be a two or three stage process, leaving time for the new pack to cool or I may need some type of water cooling.
If too much heat is generated the fiberglass used to encase the cells would crack exposing the cells to water and corrosion.
I'm not worried about discharge heat in the sub since it will be in contact with a constant flow of cooling water while the sub is operating.
What remains to be installed now are the down and reverse pumps and the RC electronics. Then the RAM needs to be completed, the bottom rakers and a rear stabilizing fin. This bottom rear fin serves two purposes. Since the sub hull is full of water with a lot of inertia, the sub tends to turn underwater when brought to a stop. The stabilizing fin resists this turning and keeps the sub in a straight orientation when the forward pumps stop. Also the sub may veer to the right or left when under full forward power at the surface. Since there is no rudder control, the rudder itself can be repositioned slightly by heating the fiberglass and making a best guess correction. This can't be tested unless the sub is actually in use at the Pond. However the stabilizing fin made of aluminum can be bent slightly while at the Pond in real-time mode. Slight adjustments are usually enough to keep the sub straight.
Some more info on progress to date with pictures
I was anxious to test the system to try and get an idea if the concept will work. I'm trying to get better turning performance at full speed by relocating the turning Jets to the rear of the sub where they will deflect one of the foward Jets. This is illustrated in the PDF file linked below. The bilge pumps themselves are not yet sealed as I wanted to get an idea if it would work before I committed to further development.
And while it seems like it might work I won't really know until I actually take it to the pond.
Also found out that charging the equivalent of 4 cordless drill batteries at once does not increase the heat but just takes four times longer.