My prototype of a semi-aspirated ballast tank system

[redboat219]

Hi, do you have a picture of how the float valve is constructed? I want to use one as self closing snort head.

[Slats]

Hi, do you have a picture of how the float valve is constructed? I want to use one as self closing snort head.

The float valve as stated comes from Jim Russell, - so I don't have pics of its construction. Its a simple ball float that closes off the top vent with water ingress to the tank.
Have a look at the basic diagram I posted in this thread.

Hope that helps
J

[Slats]

Hi guys,
a quick update on progress.

Jim's system works just fine using the PVC tank and materials I have described herein. However the key variation on my system was I installed a PVC conduit through the tank.

I have been cycling the ballast system every day for a few minutes in order to look at how well its all holding up. This morning I had a key failure - the tank let go at 7.2v - the pressure found the weakest link, being the join of the PVC conduit to the tank. If this had happened underway, it would mean dumping under pressure about 200ml of water into the adjoining WTC and could have been a disaster. A secondary tank I had on the bench was tested and this too let going with 8.4v of power - it let go in the same spot. I need to look at the my assembly of these parts carfefully. - Thought I'd give you a heads up though, as although this is my prototype, I am sure some might want to try it out.

The system seems fine with a PVC tank with no conduit - but clearly I have work to do to check out my conduit through tank version.

Best

John

PS - at 6v the pressure is a lower and has not caused any failure thus far.

[Subculture]

Double the thickness of the bulkhead/endcap, where the tube passes through. Cut out a disk from PVC sheet that allows 3/8"-1/2" around the pipe for each end, and solvent weld that to the centre of each endcap.

[Slats]

Thanks Andy, I'll give it ago.
Best
J

[He Who Shall Not Be Named]

Take heart, John, you are only identifying (good testing protocol) the bugs in an otherwise sound system. Keep at it. Rule of thumb as to qualification of a pneumatic or hydraulic system: test to 150% of the rated pressure and hold it for 12 hours without a significant drop in system pressure. You can then operate the system with a good deal of confidence.

David,

[Slats]

Take heart, John, you are only identifying (good testing protocol) the bugs in an otherwise sound system. Keep at it. Rule of thumb as to qualification of a pneumatic or hydraulic system: test to 150% of the rated pressure and hold it for 12 hours without a significant drop in system pressure. You can then operate the system with a good deal of confidence.

David,

Yes not giving up on this, proof of concept revealled that it worked. Key issue is getting the manufacture of the tank right, and I know minus a conduit through the tank, as per Jim's method it works without this hitch.
That said this will have to wait awhile.

That said, I find it revealling to myself, that for now to get me through a forthcoming regatta and runs after before the winter here in Australia, that I have grabbed a Gas /snort replacement. And yes, whilst the semi-aspirated tank, the sealed tank and indeed RCABS can be used to trim the boat at depth via incrmenental ballast change, which is not possible with gas as you tend to shoot to the surface, gas has great appeal nonetheless for its simplicity of operation cf with any system relying on holding back some sort of positive or negative air pressure.

Further, and I will be doing a write up on assembling the 3.5" SD kit soon, after having just put my first gas / snort kit together (all others had the gas / ballast pre installed), I just don't understand what is so darn complicated about Gas, and yet there are numerous sources (not just on the net), but indeed texts quoting "Gas as having complicated plumbing etc". Where is the complication? WTF am I missing? I am not the brightest or dumbest tool in the shed but I don't get it???

I would have to rate the semi-aspirated system as more complicated than Gas, RCABS too, and then of course there is the electronics etc with pistons and gears and multi tanks, which as an electrical cave man to me is scary. I just don't get why Gas is labelled as "complicated". Sure there is effort involved in tweaking it - BUT that is part n parcel of any system we employ. I have never known any submarine to be maintenance free and simply plug n play everytime, but Gas / snort IMO comes the closest to this.

J

[Slats]

Actually I will be giving up on this? why? well after a very successfully w/end at the Australian Sub Regatta, I will be confident enough to say gas with snort is king. Why? It works so well, its simply, reliable, and affordable. I spend most of my time at PD of just a bit below, so there is no need for me to chase down a system that "trims" the boat. It has been argued that gas / snort lacks a trim mechanism to obtain near neutral bouyancy the deeper you go, given that the tank should be either 100% full or empty, but in the real world who cares. I simply don't regularly go that deep to need a trim system and with a well balanced / ballasted boat neither will the majority of sub drivers. No point therefore in wasting my time.

J

[Kazzer]

Now I'm no expert operator, never have been, never will be, but I've often found all this ballast 'stuff' far too complicated and off putting to the new submariner.

The Wizard explained to me once, that I should trim my boat so the tank is full, and the periscope is just out of the water. Correct me if I'm wrong, but at 'stop engines' the boat should therefore surface to periscope depth even with a full ballast tank. Full ahead would make the boat dive if the planes were adjusted so. Isn't that called dynamic diving? Only if one dived to a critical depth would the boat not surface, and then the failsafe would kick in and gas blow the tank. Obviously, no boat in a pool would go to a critical non recoverable depth, so the gas failsafe would never be employed.
So, if you are in a pool, or shallow area, you don't need the gas and can patrol all day on the Snort. No gas, no RCABS, no other dweebie system, just Snort. If you're in a deep lake, then put a failsafe charge on gas on board.

It's so simple, why is this so over engineered?

Oh! Yes - thanks John! Great work here!

[Slats]

I'd add Mike that you should charge the gas bottle in ALL situations. Your boat should be ballasted properly based on a full gas charge.

The gas consumption I find is minimal - as the Merriman gas saver set up is the superior least complicated system.

Mike you have permission to send the heavies around and break both my legs if I ever stray again. Serioulsy guys its that good. To me reliability coupled with simplicity is everything.
J

[Kazzer]

I'd add Mike that you should charge the gas bottle in ALL situations. Your boat should be ballasted properly based on a full gas charge.

J

Agreed, but only if you are operating in dangerous waters. If yours is a pool toy, then trim the boat with the gas tank empty. Why waste gas when you can paddle?

[CamSSN771]

I watched John's sub perform at the sub regatta on the weekend. I can see more using this system.

[He Who Shall Not Be Named]

Actually I will be giving up on this? why? well after a very successfully w/end at the Australian Sub Regatta, I will be confident enough to say gas with snort is king. Why? It works so well, its simply, reliable, and affordable. I spend most of my time at PD of just a bit below, so there is no need for me to chase down a system that "trims" the boat. It has been argued that gas / snort lacks a trim mechanism to obtain near neutral buoyancy the deeper you go, given that the tank should be either 100% full or empty, but in the real world who cares. I simply don't regularly go that deep to need a trim system and with a well balanced / ballasted boat neither will the majority of sub drivers. No point therefore in wasting my time.

J

What John has identified here is the main problem I have with most guys who get into this game; guys who have yet to acquire any significant underway time driving an r/c submarine: they OVER-THINK the physics of the problem; they grasp ahold of the complicated trimming systems aboard a real submarine and assume that they have to emulate -- at least in function -- those devices that permit fine adjustment of the boats weight and weight distribution. And that's where you get this stupid fixation on the supposed need to have a variable ballast sub-system (auxiliary tanks) and/or trimming tanks distributed fore and aft to fine-tune the boats dead-in-the-water pitch-angle.

YOU DON'T NEED ALL THAT HAPPY HORSE-**** ABOARD YOUR TOY SUBMARINE!

You're fine tunning of trim is done with fixed lead weight in the bottom and hunks of foam up high in the hull -- and this is done one time.

What's wrong with you gear-heads!? Do things just have to be so *** hard all the time?! ... can't you be happy employing a method/system that works simply and reliably. R/c submarining should not be an exercise in self-flagellation! KISS, as Skip so well puts it.

KEEP IT SIMPLE, STUPID

David,

[Slats]

And on that note from David, I am re-tooling my fleet with SDs featuring gas and snort.
Mike you have got mail -just flicked you the new shopping list - hope the wife won't see it!

Life is too short and money too hard to earn to waste both on taking the wrong way. That said, its amazing how many new guys (myself guilty of this too when I started out) that bring the a pre conceived arrogance to the hobby that their home built efforts right from the get go will be cheaper and more effective. Recently met some guys that are gleeing over the massive dollars their apparently saving by tooling their own end caps. Yeah right! Reminds me of my last trip to Europe, where it seemed the highlight of every stop on the tour I was on, was some guy boasting about how he scored the best price on a Coke, by shopping around. Yes he saved a $1.75 but was this why he shelled out several grand to see ancient ruins that he missed through his bartering efforts??? The same applies to this hobby. Your prioirites should be a boat that works well and is fun to drive. If money is important to you, and I hope it is- the best bang for your buck is a SD kit that is fully backed by Mike and David.

[Slats]

I watched John's sub perform at the sub regatta on the weekend. I can see more using this system.

Thanks Cameron, and its great to have you involved in this forum.

For those who don't know him, Cameron Glassford, like Jim Russell here in Australia, is one of the guys who in my very early days in the hobby - jeppers nearly 2 decades back, offered great advice and assistance. Cameron is a talented and gifted craftsman, putting together the 1/72 Typhoon master that later became APS Models kit of the same.

J