Ballast Tanks

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The main ballast tanks are made from 150 mm PVC pipe and an approximate length of 3 meters. There are four in total, each one displacing about 50 liters and creating an overall buoyant effect of 200 kg when they're full of air. Each one is held to the side of the hull by 4 brackets. They also provide stability when on the surface.

Fig. 1. I drove into town that morning and purchased all the PVC pipes needed for the ballast tanks & trim tanks.  All up they cost me about $300 AUD.

Fig. 1.
15/04/2014

Fig. 2.  Here I'm trying to figure out the best way to hold the tanks onto the hull.  I ended up the using the modeling program Blender to design the brackets in 3D so I could be sure I would maximize the use of the space and that it would be strong enough to hold the sub up.

Fig. 2.
15/04/2014

Fig. 3.  Several days later I had a design I was happy with and then I began the tedious task of fabricating 32 brackets!  All up I had to;

• cut 32 of 60 mm x 20 mm x 5 mm (feet).
• cut 32 of 60 mm x 35 mm x 5 mm (legs).
• cut off the feet from 32, 150 mm pvc pipe brackets (body).
• drill an 8 mm hole into the 32 feet.
• grind a curve into the ends of the 32 legs to fit the body.
• clamp it all to an off-cut of pipe and tack weld it in place before testing two sets together and finishing the welds.

Fig. 3.
23/04/2014

Fig. 4.  The first two  brackets.  Still to make are the arms that will attached each pair to the sub.  They will;

• be 60 mm x 50 mm x 5 mm
• and have two 8 mm holes in each arm.

Fig. 4.
23/04/2015

Fig. 5.   These four brackets took the whole day to make because at the time I was still trying to figure out the best way to actually put them together.  By the end of the day though I had a system in play that had them all built over the next few days.

Fig. 5.
23/04/2014

Fig. 6.  I sat the first few pipes on top to make sure all was going to plan.  At this point they weren't able to be bolted to the hull.  I was also welding onto the hull the steel that they would end up bolting to.

For the tank mounts I welded 4 rolled pieces of 20 mm x 5 mm flat bar to one side of the hull, and had them at an equal distance apart from each other (about 1/3 rd the total hulls length between them).

Fig. 6
24/04/2014

Fig. 8.
21/06/2014

Fig. 7.
21/06/2014