Ballast tank/bag placement

[redboat219]

Just curious about where the ballast tank/water bag should be placed in the hull. Noticed in the old Krick Uboat it was above the dry hull
In JHapprch's Delta II I also noted the bladder was in the upper half of the WTC. Not saying it's a bad system but shouldn't it (ballast tank) be lower down in the hull for stability? I guess you could offset it with keel weights.

[JHapprich]

Maybe you should build a boat and try ;-)

[redboat219]

Maybe you should build a boat and try ;-)

So build a boat, stick the ballast tank anywhere I fancy and worry about stability later.

Couldn't I make a boat inherently stable from the start?

[JHapprich]

You are not a practical type, right? Nothing is perfect from the start.

"Stability" is not the problem, but your shifting cg when filling the bladder, i.e. will you dive front or stern first. Keep in mind the weight of balast water you are talking about, compared to the weight of the dry model. Dry hulls are naturally heavy.

Ideally balast tank goes low. Often not practical in a dry hull, or better explained you waste space in doing so. Therefore the battery ( i used nimh packs) go low.they are always heavier than the balast water in that model scale around 1m in total. The battery is your "active" or "life" balast.

You are thinking from the wet hull perspective.

Another application in my modified arkmodel redshark:

[JHapprich]

See that one trim weight in the lower stern? That is your "keel" balast to fine tune for level diving.

There is a bit more brain grease in those models than putting your components in a subdriver/dive module/whatever. You have to calculate the position and weight of each component and its effect on trim.

Think of it as if you would trim a subdriver itself instead of the hull around it. How much balast water would you need to submerge the module only?

Jörg

[neitosub]

The ballast tank has always been the biggest component in my WTCs, followed by the battery. Everything else gets squished around them. Always have the ballast tank more or less in the center of the boat. Trimming sorts out the balance later.