Resurrecting the dead Gato project

**JWLaRue** · 02-28-2012, 10:11 AM

Re: Resurrecting the dead Gato project

Steve,

I'll see if I can help.

1a) Ballast system : a lot of us trim our boats first for a submerged trim (ballast tank full of water) and once that's satisfactory, do the surfaced trim.

1b) Maintaining depth: using an ADC is one way to do this. But most of us do not use this device, preferring to 'fly' the boat with the joystick. If you do use an ADC, the preferred method is to mimic the way the real boats do it - bow planes are used to control depth and stern planes are used to control pitch.

1c) Redundant ADC: whether or not the boat sinks (as in to the bottom) is dependent upon what your submerged trim is. Some folks do the trim such that a very small amount of the conning tower is out of the water. For me, the submerged trim depends on which ballast system I am using. For example, on a gas-boat (e.g. Propel) I trim so that the top of the sail is just out of the water. But for my boat that uses an Engel piston it is trimmed to go all the way to the bottom since I can control depth with the piston.

2) Pitch of the sub: I would suggest getting a pitch controller....most folks find these very useful to keep the boat on an even keel. Connect it as per 1b.

3) Running lights: port and starboard on the sides of the conning tower. The stern light is on top the stern fairlead.

4) Paint: make sure that it won't fog in water...which is what acrylics tend to do. Lacquers are really good. For smaller boats I use Testors ModelMaster through an airbrush. For really large models I like to use Krylon rattle can.

Hope this helps! Please feel to ask questions.

-Jeff

**stevolution** · 02-28-2012, 11:02 AM

Re: Resurrecting the dead Gato project

Thanks Jeff.. although even more confused now

Not sure where I am going with this now then.

I have a pretty decent sized ballast tank. So you are saying sink the sub with a fully flooded ballast tank, then pump air into the ballast balloon until she floats - then trim her to waterline.
What is submerged trim then? Surely.... once flooded it sinks.... job done! Is the idea to aim for barely heavy enough weight to submerge? Does it matter if full ballast tank = straight to the bottom?
I can understand a surface trim - getting to to sit on the waterline correctly.

So... the ADC and APC.
I thought the subs sometimes had issues staying at depth (wallowing up and down) if you didn't have an APC. Especially as I am a newbie to these things.

Therefore, correct me if I am wrong... Fit an APC to control the rear planes. Also, the rear planes are the ones I operate from my radio if I want to adjust pitch manually. When I release the stick, the APC would level her again using the rear planes.

An ADC would be controlling the front planes. This would need to have some sort of safety switch to ensure it only operated when the planes when they were folded down.
I spent ages making the front planes deployable and tiltable ... gotta use them!
I read that you set the ADC default depth before it sails.... eg 18" deep (is that how the ADC-1 works?) When you decide to dive, you switch on the ADC from your radio and it operates the front planes until you are at 18" depth with the stick dead centre. You can then manually adjust the depth either side of that with the stick if you wish.

So many things seem to conflict here. If I manually decide to alter my rear planes while on the surface and effect a nose down pitched 'dive' then I assume she will will attempt to dive.... but fail because my ballast tank is empty.
So what is the point of having manually adjustable planes? You would be fighting the ballast tank if surfaced and fighting the ADC if submerged.

To my thinking (get ready to shoot me down!!)... the ADC would control the ballast tank. I set the depth I want and the ADC operates the ballast control until she decends to that level. The APC keeps her level. Is that novice thinking?
Perhaps the adjustment of buoyancy would not be quick enough to maintain depth (however surely buoyancy would not need much adjustment once correct for a certain depth). The ADC will be keeping her level.

I don't think I understand the skills and practices involved in model submarining yet.

**stuartl** · 02-28-2012, 11:40 AM

Re: Resurrecting the dead Gato project

I have a pretty decent sized ballast tank. So you are saying sink the sub with a fully flooded ballast tank, then pump air into the ballast balloon until she floats - then trim her to waterline.
What is submerged trim then? Surely.... once flooded it sinks.... job done! Is the idea to aim for barely heavy enough weight to submerge? Does it matter if full ballast tank = straight to the bottom?
I can understand a surface trim - getting to to sit on the waterline correctly.

I don't want to mis-speak for Jeff but I think he was referring to trimming the boat so that it's natively level when submerged, i.e. the bow and stern are at equal depth. You may choose to trim the boat so that it's slightly bouyant with a full ballast tank, i.e. will eventually float to the surface, but that's very much a modeller's decision.

**JWLaRue** · 02-28-2012, 11:47 AM

Re: Resurrecting the dead Gato project

Steve,

Oh, no! Didn't mean to cause confusion. Let's see if we can make things more clear.

>>> So you are saying sink the sub with a fully flooded ballast tank, then pump air into the ballast balloon until she floats - then trim her to waterline. What is submerged trim then?

Submerged trim is that condition that you want the sub to be in when the ballast tank is full (of water). Even if you want it to go to the bottom, you will want to add floatation foam so as to get the boat as close as practical to the theoretical 'neutral buoyancy'. This minimizes the amount of lift that the ballast tank needs to provide.

If you choose to trim the boat such that a small amount of the sail (or conning tower or shears) is out of the water, then you will need very little forward motion to drive the boat down. Don't forget that as the boat submerges it compresses as it goes down...which reduces the buoyancy further. It's a personal preference mostly around how much risk you want to take with not getting the boat back in the event of a failure.

>>> So... the ADC and APC. I thought the subs sometimes had issues staying at depth (wallowing up and down) if you didn't have an APC. Especially as I am a newbie to these things.

Correct. You're referring to porpoising as the person controlling the transmitter tries to react to and counter the pitching movements of the boat. The APC can do that for you if you want it to.

>>> Therefore, correct me if I am wrong... Fit an APC to control the rear planes. Also, the rear planes are the ones I operate from my radio if I want to adjust pitch manually. When I release the stick, the APC would level her again using the rear planes.

I think instead of "adjust pitch manually" you might be thinking "adjust depth manually"?

Yes, if you prefer to control depth through the stern planes with an APC in the circuit, the APC gets overridden when the transmitter stick is moved to command the planes to move. Once the stick goes back to neutral, the APC takes over again.

>>> An ADC would be controlling the front planes. This would need to have some sort of safety switch to ensure it only operated when the planes when they were folded down.

Agreed. These days programming the computer-based transmitter is the way this 'safety switch' is done. I've seen folks do this mechanically, but I don't have a diagram handy that shows this.

>>> Can you not adjust your desired running depth as you go? Could be totally wrong there however.

Sorry, I've never used an ADC, so will need to have someone else provide the answer. However, I *think* you can change depth and the ADC will then assume that the new depth is the one to be maintained.

>>> If I manually decide to alter my rear planes while on the surface and effect a nose down pitched 'dive' then I assume she will will attempt to dive.... but fail because my ballast tank is empty.

Empty as full of air? Then it will be difficult to drive the sub down except be running the motors at very high speed...if even then.

>>> So what is the point of having manually adjustable planes? You would be fighting the ballast tank and the ADC.

Having a submerged trim for the boat does not mean that you are fixed at a set depth. When at submerged trim you are close to neutral buoyancy. Neutral buoyancy is not really practical for model subs...unless you can make very, very fine ballast changes. So we strive to get close enough such that when submerged, the boat can change depth with the combination of very little forward speed and the flow of water across the planes as they are moved to change their pitch. This has nothing to do with the ballast tank...see next answer.

>>> To my thinking (get ready to shoot me down!!)... the ADC would control the ballast tank. I set the depth I want and the ADC operates the ballast control until she decends to that level. The APC keeps her level. Is that novice thinking?

The ADC controls the bow or stern planes. Unless you are running a ballast system like an Engel piston, the ballast tank is either completely full or completely empty. Submerged depth is controlled with the planes.

------

Lot's to digest here....is this helping to make things clear(er)?

-Jeff

**JWLaRue** · 02-28-2012, 11:50 AM

Re: Resurrecting the dead Gato project

I don't want to mis-speak for Jeff but I think he was referring to trimming the boat so that it's natively level when submerged, i.e. the bow and stern are at equal depth.

Good point! That's an important part of what is done during trimming, but I was specifically focusing on how far down the boat goes when the ballast tank is full. It would be very difficult to adjust the pitch or roll trim if the boat is on the bottom.

-Jeff

**stevolution** · 02-28-2012, 12:20 PM

Re: Resurrecting the dead Gato project

OK... thanks guys.... I am getting there.

Yes, I realise that part of the buoyancy trimming requires getting her to sit level whatever depth she is at.

So, the idea is you aim for approx neutral buoyancy once your ballast is full of water.

Also then, this means that depth control is only achieved through forward motion.... with ADC control of the front planes
Does mean you can't actually static submerge while sitting still unless you trim her slightly heavy.

Your actual depth you want to obtain is arrived at by letting the ADC controlled front planes drive you down to depth you select as you move forward.
Or you could manually drive your sub to that depth using the rear planes - manually controlled by me and then trimmed level once dead stick by the APC. No ADC required.

My ballast is a pretty decent size. Due to having no real idea of the size of tank required, I kind of made it as big as I could. That may bite me in the bum now (although I can cut it down) as I might not need anywhere near as much ballast as I can probably obtain.

And I didn't take up RC helicopters cause they were too complicated to set up

**JWLaRue** · 02-28-2012, 12:33 PM

Re: Resurrecting the dead Gato project

>>> So, the idea is you aim for approx neutral buoyancy once your ballast is full of water.

Yes, either just slightly floating or just slightly heavy enough to sink. (again with the caveat around a ballast system with a fine level of control being a possible exception.)

>>> Also then, this means that depth control is only achieved through forward motion.... with ADC control of the front planes. Does mean you can't actually static submerge while sitting still unless you trim her slightly heavy.

You will 'static' submerge all the way down to your submerged trim level.

>>> Your actual depth you want to obtain is arrived at by letting the ADC controlled front planes drive you down to depth you select as you move forward.
Or you could manually drive your sub to that depth using the rear planes - manually controlled by me and then trimmed level once dead stick by the APC. No ADC required.

Correct, with the possible exception that I noted that the ADC may allow you set a desired depth by simply driving to it and then lettign the ADC take over.

>>> My ballast is a pretty decent size. Due to having no real idea of the size of tank required, I kind of made it as big as I could.

Speaking of which, what scale Gato are you building? Whose hull/kit is it and can you share some details aroudn your dive module, etc.? We love to hear what everyone is doing! (photos are good too!)

>>> And I didn't take up RC helicopters cause they were too complicated to set up

Naw, this is much easier. And subs are even easier to run. There really isn't any such thing as "re-kitting" with r/c subs. (Unless you're BD and you smash your Sushi sub! LOL!)

-Jeff

**stevolution** · 02-28-2012, 01:07 PM

Re: Resurrecting the dead Gato project

Its a Revell 1:72 scale. Getting put together with bits from the workshop!
I will get some photos together and start a thread.

Made boobies along the way. For starters, I didn't have a full length of acrylic tube, so mine is made up of sections. Not a tragic issue, but does make for a more complicated build.
My WTC is too big for the hull really. I got fed up trying to 'pry' it through the open top in sections (cut along the top - just above the deck join). Finally cut it completely half (I can hear the gasps) and made an aluminium ring to join the halves back together.
Makes putting the WTC in much easier and seems fine.

I just don't really have much room (hence the big WTC tube). I think my ballast tank is too big. Doesn't leave me much room at the bow and stern for connecting the shafts and servo links.

Its all a learning curve!

My biggest gripe I think is the air pump (old blood pressure monitor).... WAY too noisy for my liking, but I am not trying to get that out now.

Currently got a standard balloon inside the ballast tank, but I suppose I should get something a little better than that.

Thanks for all the assistance guys
Steve

**thor** · 02-28-2012, 01:10 PM

Re: Resurrecting the dead Gato project

Steve,

I am very happy to see you back at it! When you get the chance, how about renewing your SC membership? Keep up the great work!!!

Matt

**JWLaRue** · 02-28-2012, 01:43 PM

Re: Resurrecting the dead Gato project

Steve,

The size (e.g. volume, the amount of variable ballast) of your ballast tank only needs to be equal to (or very slightly larger than) the amount of water that the above-the-waterline part of your boat displaces. Anything more is essentially easted space.

This volume can be derived by getting your submerged trim and then (temporarily) adding foam until you get a proper surfaced trim. The volume of the foam equals the volume of your ballast tank.

-Jeff

p.s. I typically use the Skip Asay method and place a couple of rubber bands around the hull and place the hull beneath them. The rubber bands hold the foam in place well enough to figure out how much I need. You'll be wanting to place the foam at or below the waterline....hopefully the reason is obvious!

**stevolution** · 02-28-2012, 02:31 PM

Re: Resurrecting the dead Gato project

Mmm
That was the trouble when I was building it.... displacement what na who how? You sort of need the model finished surely to be able to work out what its displacement is.... but its not finished, cause you have not made the ballast tank!
I ended up (if I remember rightly) going for the ..... too much is better than too little. I can always shorten the ballast tank if need be.

As a side question (gonna get banned in a minute for too many silly questions in one sitting)...

Prop shafts. I don't have any posh bearings or methods of exiting the WTC.
I was thinking... and again, please feel free to laugh and put me right...

Could I take a length of brass tubing say 4" long. Solder a short length of the next size down brass tubing in each end. Drill a hole off at 90 degrees part way along and solder another piece of pipe on with a cap on it (making a greasing access point))
Push a solid brass driveshaft through the whole tube (next size down again from the smaller tube)
Then pack this tube with model prop shaft grease (using the piece of pipe I soldered on at 90 degrees) until the tube was full.

Would it work? or would the grease just push out under pressure or get hot and leak out.

Any ideas welcome.

**JWLaRue** · 02-28-2012, 05:07 PM

Re: Resurrecting the dead Gato project

It's not really required to have the model built before determining the size of the ballast tank. What you can do is to take all the components for the dive module (e.g. motors, servos, ESC, battery, etc.) and put them in the empty tube with the end caps in place. Tape the model hull and conning tower together. Place the dive module in the hull...don't forget to add the props and shafts.

Next get a submerged trim by adding foam and/or weight as necessary. Once you have a submerged trim start adding foam until you get a good surface trim. The volume of foam that you added to go from submerged to surface trim is the volume that you need the ballast tank to be. (I'd make it ever so slightly larger just as a bit of insurance)

For the shaft seals, a greased stuffing tube will work, but you may wish to consider using o-rings or cup seals instead. This tends to be the more current accepted practice. Check out the SubTech BHS seals to see what they look like. You can also make your own if you have access to a lathe.

On the A-frames, I'd recommend staying away from a metal-on-metal bearing surface. Something like an oilite or Rulon bearing will give you far less friction, which translates to lower amperage draw and longer run times.

-Jeff

**stevolution** · 02-29-2012, 10:51 AM

Re: Resurrecting the dead Gato project

The main issue is the prop drive leaving the WTC. I did have a load of bookmarks for various bearings to fit (back when I started the build), but all these bookmarks are now dead links - so research is needed again.

I can't remember off the top of my head, but I think my drive shaft is 3mm. Might be 4mm.

I think I originally planned to buy a couple of ball raced decent driveshafts to actually install into the hull, and then connect between those and the WTC with my universal joints.

I will have to Google for bearings!

As a side question. Props are handed, so I assume the threads inside are too. Therefore an 'off the shelf' prop shaft surely will be thread the wrong way for one of my props.

Steve

**stuartl** · 02-29-2012, 11:46 AM

Re: Resurrecting the dead Gato project

I can't speak for the US (not sure where you are) but www.rcbearings.co.uk is run by a mate of mine and it's excellent. I'd use him without question even if he wasn't a mate. Cheap high quality bearings...

Resurrecting the dead Gato project

Resurrecting the dead Gato project

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