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[gingyer]

Hi All,
looking for some feedback,
has anyone used the WTC from A1 down under models??
 
how did you rate it? would you recomend using them?
 
thanks
 
Colin
 
 

[Subculture]

They're selling on ebay now. Only seen them in pictures. They look nice enough, and competitvely priced against the competition. They appear to be similar in design to Sheerline modules, with external endcap rods and a sealed tank water pump system.

They use what looks like clear acrylic tubing in place of PVC pipe, and a geared pump in place of a centrifugal design. This allows bi-directional pumping, but the flow rate will be lower, so I would expect leisurely diving times if you have a large tank, unless multiple pumps are fitted (not very efficient) or bigger pumps are specced than the ones shown in the images I've seen.

[gingyer]

they look ok and I saw them years ago at blackpool
but he only had one with him it looked ok but given that was the demo model
it has to work if you know what I mean...NOT saying he is selling faulty items
 
I was thinking about 1 for the OTW S class as you said it was a good bit cheaper than the rest.
failing that I had been looking at building my own and using parts from RC-SUB WORKSHOP have you
or anyone had dealings with them?
 
Sorry for all these questions but I am looking at alternates without having to get buy a OTW WTC
and I want to make sure what I buy isn't going to cause me major problems
 
Colin

[Subculture]

No I haven't purchased anything from them. Some bits look okay, some others look a bit over priced IMO.

For an s-class, you need a big tank. The pumps OTW use are high flow, 4 litre per minute units. Geared pumps typically only flow about a quarter of that, with larger geared pumps like Kavan flowing about half that rate.

They make higher pressures though, so better suited to a sealed tank system. Somone mentioned the tank size for an OTW S-class in another thread- over 2 litres. So you are going to be looking at dive times of over a minute, which is too slow IMO. But it's your boat.

[gingyer]

I had seen that thread and had expected a tank about 2litres
 
one idea I had thrown about in my head and reading what you had said in the same thread about 2 pumps
was using 2 pumps connected to 2x 1400ml water bladders that would give me 2.8litres of available ballast which would allow for
any miscalculations. the down side I saw in that was the bladders would sit behind each other if something failed then it could be a bit of a problem with weight going each side of the CofG or maybe I was thinking too much
 
I had also seen that the RC SUB Workshop had a submersible pump available that pumped 8l/min with a drain of 3Amps/hr... it was big at 2"x4" but you could stick that external to the WTC as its submersible. may even cut down on any potential interferance problems as I know I had to heavily supress the pump in my trafalgar class
 
 

[Subculture]

For a tank the size you need, I think you are better off with a hard case than a bag- they're better suited to smaller volumes.

My personal preference is for ballast systems that don't maintain an air bubble, thus eliminating slosh (even with baffles you tend to get some movement of water which can hinder the boats underwater handling). That tends to rule out the sealed tank system unless you compress the air into an auxilliary container.


However I'm aware it has it's fanbase as it's simple to build and inexpensive.

[gingyer]

thanks Subculture,
can I ask how you would go about the ballast tank?
not too sure what you mean by getting rid of the air bubble are you meaning similar to OTW
with an opening for the air to escape from into the "dry sections" of the WTC or something else??
 
Colin

[Subculture]

The OTW system employs an air bubble, but it's a lot smaller than the sealed tank system, so that cuts down on water movement to some extent.

Systems that don't keep an air bubble are piston tanks, flexible bag systems (e.g. Thunder tiger Neptune), snort/ gas and hybrid ballast systems which mix technologies and tend to incorporate separate main and trim tanks.

Unfortunately very few of these systems are available in commercial format that are adequate for the size of model you are building. That means scatchbuilding.

If you are seriously thinking about building your own ballast system, then you need to get a copy of the Model Submarine technology book from Traplet.

This doesn't give much in the way of building details, but it does cover the theoretical bases, and spells out the advantages and disadvantages of the various systmes you can use.

[gingyer]

If you are seriously thinking about building your own ballast system, then you need to get a copy of the Model Submarine technology book from Traplet.

Santa wouldn't take the hint so ordered it last week 
 
Thanks for the info some more things to ponder over

[Subculture]

Good stuff. Don't blame me for the headache though. The book is very technical, but the principles are sound- follow the advice in that book about pressure hulls and ballast systems and you should have a nicely performing boat.