Need lots of help

[Nb1914]

I had a look through Tims build, very interesting he has the battery in the same compartment as the Ballast bag, i wonder if having the battery in there takes up volume so you only need a small ballast bag ??? i think from some pictures i could see how he fixed the top hull half to bottom hull, looked like velcro on right angle bearers.

[Nb1914]

Ah no, the total volume isn't changed where ever the battery but balance does .

[Ralph --- SSBN 598]

You got it.
Battery is movable ballasts that can be used to trim.
Tim has a containment tank for his ballast balloon.
He used clear plastic and it can be hard to see.
I am not sure by he may have removed that tank in the updated build.

My battery slides under the containment tank and both can be move in either directs to trim.

Tim had worked out that the ballast tank needed to hold just over 400 ml.
Mine hold about 425 ml.

The submarine is trimmed with ballast bag empty and ballast bag full of water.

When trimming the boat, weight is added in the bottom of the hull and flotation foam is added at and below the water line.
The weight of the equipment is not relevant to the trim.
Only it's position effects fore and aft trim.
The weight of the equipment and weighted ballast is compensated by the cylinder buoyancy and foam added.

The live ballasted needed is determined by the volume reduction in the cylinder to go from waterline surfaced to submerges with about 1/4" to 1/2" above the water.

It sounds complicated but once trimming is started, it makes sense.

An object that weights 10 pounds or 100 pounds may take the same live ballast to go from waterline to submerged.
If the above waterline parts are equal.
The 10 pound object will take far less foam than the 100 pound object to achieve positive buoyancy.

Yea, technical stuff.
Easier to do than to explain.

[Nb1914]

Im learning ………i think, so if i have lots of weight in the front and it sits nose down tail up i can either put weight in the rear or foam in the front to compensate, so its very low in the water (no ballast ) with the nose completely under etc foam in the front would be better than weight in the rear that would take the entire sub under ?. If i parallel 2 batteries i might put one in the rear one in the front if i can get decent gauge cable front to back.

[Nb1914]

Motors and elastictrickery not my strong pojnt either but here goes. I looked up your motor anx it is rated at 1885kv . I would imagine with a sub that we want low rpm for the max power of the motor. This is how i see it ,i have a 400kv motor and lets say it max power is 100w. Lets say i have a 14.8v battery . I will pull 6.8 amps to achieve 100w, anx my rpm would be approx 6k. With the same setul your motor would be at 27k
rpm. If i use a 7.4v batt i woulx pull 13.6amps and have an rpm of approx 3k you would have an rpm of approx 14k. Im sure someone can correct me im wrong but in all scenarios we produce the same power 100w but your boat is goinv tk be much faster. So for a scale performane i guess i need tk lower my voltage. Bit diesel car v petrol both produce same power but at different rpm .

[Nb1914]

Just incase it might be of use to others see attached which is a wiring harness for parallel connecting 2 lipo's to increase capacity. The small devices you see inline on each positive leg from the battery are Schottky diodes preventing cross charging between the batteries, this at 11.1v only looses 0.05 volts.



This is easy to confirm with a Ohm meter ( multimeter ) i.e. if you put the tester positive probe on the positive input for each lipo connection it will see an open circuit , but when you put the negative probe on the positive leg of the combined output it see apron 120ohm.