Semi-Aspirated Ballast System

[He Who Shall Not Be Named]

This is really great! I so enjoy the learning I am getting while I see a wonderful addition to our hobby being created. I know that at the end of the day there is going to be moisture. That is the environment that our subs will run in. And as David pointed out, do the pre, running, and post checks, however.... would adding a silica filter or pack above the tank help absorb the nominal moisture that might be blown out?

Something like this?
[ATTACH=CONFIG]12213[/ATTACH]
Or am I over thinking this? Is it necessary?
Peace,
Tom

You're over thinking this!

Damit! I feed you, cloth you, send you to school. And what do you do?! ... you eat the *** Teacher!

David

[trout]

LOL - a momentary lapse of judgement.

[He Who Shall Not Be Named]

I just had another thought (scary, I know). You could make your sub slightly negative buoyant (is there really such a thing - when a sub does not come up?), then use this system to partially blow the tank to hover????

No.

Two reasons:

1. Free-water sloshing around in a partially filled ballast tank kills pitch stability unless you put in a rather complicated baffle system within the tank.

2. Use of air within the SD is a rare occurrence. Normal operation of the sub-system employs snorkel head-valve supplied air. Constant, unnecessary use of SD air -- a finite commodity -- will get you into trouble (unless you have an emergency gas sub-system installed as back-up).

Do not hover or play games with the semi-aspirated sub-system.

David

[MFR1964]

Looking good David, nice to see how you do your tests, i run them the same with all new designed components, one remark, there is a nasty catch using a ventilated WTC, if your boat stands in the sun or warmer climate for a long period she will become bigger, not much, but enough.

Then you decide to take the plunge into the colder water, you're a fast diver, so after putting her into the water you want to submerge rapidly, there it goes wrong, this period between dry and warm, and wet and cold will give you allready a vacuum inside the WTC due to the shrink of your sub/wtc.

You need at last 5 min above the surface, just to let your sub shrink, doing this with the open schnorkelhead you will create no vacuum, since i use compressed air it's not a big issue for bringing the boat up, but in your case it can happen that you don't have enough air to bring her up.

And believe me, it happens, every time i dive directly after putting her in the water without the 5 min period, she will suck up some water through the rubber sealing of my hatches, underpressure is more violent than overpressure inside a sub, for sealing off the hatches completely i need the pressure from outside the sub.

Tom,

Using silica i wouldn't do, because you want to evaporate the catched up water, silica wants to bond to the water, in my profession we use silica inside CCTV camera housing to suck up the moisture in the air, have to replace it on a regular base to keep the moisture out.


Greetings Manfred.

[trout]

No.

Two reasons:

1. Free-water sloshing around in a partially filled ballast tank kills pitch stability unless you put in a rather complicated baffle system within the tank.

2. Use of air within the SD is a rare occurrence. Normal operation of the sub-system employs snorkel head-valve supplied air. Constant, unnecessary use of SD air -- a finite commodity -- will get you into trouble (unless you have an emergency gas sub-system installed as back-up).

Do not hover or play games with the semi-aspirated sub-system.

David

That makes sense (of course).
Thank you for clarifying.
I think this should be called SASSy (in true government form using acronyms) or SASSI (Semi-Aspirated Sub-System Integration).

[trout]

Manfred,
Thank you for clarifying on the silica. I have used it to dry flies while fly fishing and I know it is packed in a ton of stuff we order. Just me over thinking.....
I recall in a post somewhere about the cooling effect of water verses the heat from warm atmosphere and the vacuum it creates. I just cannot recall the issue. My mind had a check mark to remember to allow the sub to adjust. I guess the same can happen in cold air and warmer water except expanding air issues.

[MFR1964]

Tom,

Your´re right, allways keep the cooling down time for your sub inside your mind when you use a ventilated WTC, cold air and warm water won´t be a issue, expanding air is not a issue, it will create more pressure inside the WTC, when becoming to high the floatvalve will shortly open to equalize the pressure.


Greetings Manfred.

[trout]

Correct on a ventilated system, expanding air would just escape out. On a non-ventilated system, expanding air might push an end cap off - which I think was the issue with an individual running in winter.
Thank you Manfred!

[Reckless]

whats the chance of something like an Assembled/complete SAS SD with no gas offered for the 144 Kilo?

[redboat219]

David's current induction head float valve won't fit inside the Kilo's small sail, you need to make a more compact closing mechanism to seal off the snort intake.

[Albion]

i could be wrong, but in think the kilo will be too small for this, the type VII is probably borderline

[Reckless]

arent ya'll a bunch a buzz kills :P

oh well can't have everything... I wanna do a smaller nuke sub next ... all this WW2 1/72 scale detail stuff back to back is getting hard on the hands/eyes... LOL

[redboat219]

Well according to David it'll fit inside a 2" SD.
Just have to modify the snort head float valve. That lever arm won't fit inside the Kilo/ Seawolf sail. You have to lose the masts and put in a sliding type float valve to seal the intake.

[Subculture]

Don't know about the Kilo kit, but most injection moulded models tend to have quite thick walls, so perhaps you could sand out the inside a bit, and that might give you sufficient clearance.

[Albion]

i wonder not about the outer float valve, but where the inner float valve will go, and how much air is inside the dry spaces