Is this possible?

[mrcandyman]

Hi there. I have decided my next RC will be a submarine. I have been racing cars and trucks since I was young and have been flying helicopters for a few years now. I also have a boat that I use occasionally. The submarine is unique and I want to use it to explore the bottom of lakes.

I have been reading about RC submarines and real submarines and how they work. I also see that quite a few RC modelers try to make their operate like the real thing. I have not, however, seen a RC submarine with actual functioning saddle ballasts. I find this odd because it would be very simple to, say, use a plunger hooked up to a tube connected to the saddle ballast, sucking the air out and into the ballast when needed. This would save room inside the model as well.

I Do notice that the Grado model doesn't have separate side ballasts and instead it's just a molded hump. Of course either you'd need to find a model with the ballasts separate and that glue on to the side, or you could fill the inside of the model with another piece (I'd not like to do this though as if they pop out, it's doomed.

SO basically I'm asking why people don't do it and if there are any models that have the saddle ballast tanks separate, even if it's a smaller model.

[JWLaRue]

Using multiple ballast tanks is

Using multiple ballast tanks is certainly possible, but in practice it's just easier to deal with a single ballast tank in a model. That eliminates any need to provide a means to equalize multiple tanks. It can be (and has been) done, but most folks prefer simplicity of operation....which also greatly increases reliability.

-Jeff

[mrcandyman]

If you had 2 separate

If you had 2 separate plungers though then you wouldn't have to worry about one getting the air while the other doesn't. I thought most people were using 2 (or 3) ballast tanks? One in the front, one in the back, and sometimes a third as a trim tank, which I would have to assume they would be using in the middle (I haven't seen any pics of one set up like this in an RC yet). That would still require equalization.

[JWLaRue]

Any time you have more

Any time you have more than one tank, it would require some means to ensure that they stay 'in synch'. The Engel piston system is the principle system that I see used where there are two pistons that are slaved together with custom (Engel provided) electronics.

...having two plungers yields the same 'requirement'......

Folks who do use trim tanks seem to use a single, central ballast tank and then fore and aft trim tanks that are then used to adjust the pitch angle of the sub. This can be useful for static trimming. For dynamic trimming (e.g. while moving through the water) a pitch controller is the most common method used to maintain correct pitch.

-Jeff

[mrcandyman]

Hmmm...I see the point behind

Hmmm...I see the point behind using fore and aft trim tanks. For some reason I was taking this out of the equation. The saddle tanks would be able to provide better cornering stability underwater. Wonder if I could get away with using the 2 saddle ballasts and then just having a fore and aft trim tank. Sure this would mean that there would be 4 tanks instead of 3, but the tanks inside would be smaller than having them all inside, and I would get the added stability. Hmm...this would require 3 channels just for the tanks. Of course doing it the common way would also require 3 channels for the tanks. This way would definitely be more complex though, not to mention the failsafe I intend is a compressed air system, making for a 4 channel requirement just for diving...

[JWLaRue]

I find that I got

I find that I got much better stability if I place floatation foam in the (upper) saddle tanks and place the weight (batteries and ballast) low and along the centerline.

-Jeff

[mrcandyman]

yes, definitely need to keep

yes, definitely need to keep the weight low. I'm considering not using a WTC in order to keep the weight low and for sheer simplicity's sake. I know the risk though and am not sure if I want to take the chance. I might just do what I do in my cars and balloon the equipment (aside from motors of course) to minimize the amount of water that can contact the electronics. This would save some weight, bring the weight lower, and be easier to fiddle with. Only downside is the potential to lose everything. I will have a camera mounted inside the sub though so it wouldn't get TOO much water in before I notice... Something to think about anyways. Definitely going to need to pressure test it all before putting the electronics in.

Oh, I do have another question. How are people sealing the removable section of the hull? If you cut it away to open it up you'll be left with a small gap that is easily filled in, but do people build a lip below that section all around and use a gasket of some type?

[JWLaRue]

Oh, I do have another

Oh, I do have another question. How are people sealing the removable section of the hull? If you cut it away to open it up you'll be left with a small gap that is easily filled in, but do people build a lip below that section all around and use a gasket of some type?

Sealing the hull......if I understand what you mean correctly, this is why folks like the dive module approach. No need to seal the hull.

If you are looking to seal the hull and create what is called a dry hull sub, then some sort of gasket seal will be needed to ensure that there is no water leakage. Where the hull pieces join some sort of flange or lip could be used as a base for the gasket.

-Jeff

[mrcandyman]

hmm...so people aren't sealing their

hmm...so people aren't sealing their hulls correctly then? I'm thinking of a light wood (balsa probably) case that will boh house the electronics and form around the top to I can seal it up. Create a gasket system and have the top screw down onto it. I would of course use metal for where they screws go in.

Anybody know of any good model japanese subs to use to make an RC one out of? I prefer their look.

[JWLaRue]

hmm...so people aren't sealing their

hmm...so people aren't sealing their hulls correctly then?

...correctly? Folks are doing what is appropriate for the type of sub they are building. (e.g wet hull vs. dry hull)

-Jeff

[mrcandyman]

I have another question. If

I have another question. If I were to hand craft a sub, say, about 40" long out of sheet metal, would this add too much weight for the sub to stay afloat unless I put on bigger ballasts or would it simply mean I would use less added weight (shot, ect.) to bring it to a good water line above water?

[skip asay]

mrcandyman -

I hate to burst

mrcandyman -

I hate to burst your bubble but let me make a suggestion.....buy a Dumas Akula, build it, and run it. Then, and only then, build whatever you're thinking of building. While you certainly possess the requisite knowledge about the R/C end of things it's very obvious that you don't really have a clue as to how a submarine works.

No, I'm not putting you down. I remember being exactly where you are. The only difference is that there were no kits or sub related parts available back then.

Just a suggestion.

Skip Asay

[mrcandyman]

Hey Skip. Why would you

Hey Skip. Why would you that? What knowledge about how they work do I seem to lack? I know I would rather be told what I lack than buy an kit that I would end up shelving, especially a dynamic driver. I don't really see what knowledge I could get from an dynamic kit.

[Guest]

Well for starters I'd say

Well for starters I'd say you need to go and have a look at Archimedes principle, and find out the answer as to why your idea of making things lighter won't work.

Secondly, a dynamic diver is an excellent boat to learn about how submarines work. Most boats equipped with a ballast system are trimmed slightly buoyant, so they still dive dynamically, albeit with very little effort.

A dynamic diver will teach you many things- how to seal a boat reliably from water pressure, how to trim and control a boat underwater.

You can always retrofit a ballast sytem later if you wish, but I think you will find a small dynamic boat is a nice thing to have around- they're simple and fun to run, even when/if you move on to more complex creations.

[u-33]

Having read all of this

Having read all of this post Mr Candyman, I would say to you to read and inwardly digest all the information the guys here are offering, they have been there and made all the mistakes that you are will be making, and you will make mistakes, trust me. I've been making model subs for years now and look at my post count, most of them are asking questions of how to do this and that.

As Andy says, start yourself off with something easy to build and easy to operate properly, a dynamic diving boat is absolutely ideal. Learn from it, then you can go for an all singing, all dancing static diving boat. A ststic diving boat is a totally different animal to a dynamic diving boat, but if you start your r/c sub career off with something difficult to build and control you'll be doing it long!

The guys here will help you all they can sir...listen and learn from them. I do...


Cheers,

Rich


Oh, I used to fly model helis as well...a piece of cake compared to running a full static dive sub.