Delta Show and Tell - In progress details

[rcher]

Though it was time to show the progress on my first submarine. Really liked the looks of the Delta but as I already had most of the plastic material laying around, I decided to build it from scratch. Two weeks later this is it so far. I'm aware that it is not exactly scale since I had to make some concessions due the available materials that I was using to build the model. But I'm building as close to scale as I can. I think I'm going to call it the "Epsilon" which is the next letter in the Greek alphabet.

I'm going to use Art Broder's bladder system and power it with a 550 motor or maybe a smaller 380 motor/gearbox. I have the hull mostly detailed and it is just about ready for it's first coat of primer.






My next step is the WTC. Here's a question, does the WTC need to be as small as possible or as big as possible. The hull is 6" dia x 12" long.

[Guest]

Hey, looking good there.

In regards

Hey, looking good there.

In regards to the WTC, you need to size it to support the weight of your equipment and batteries.

The volume is easy to ascertain for a cylinder-

Pi x radius squared x length of cylinder.

If you use metric as your measurement system that'll give you volume in litres which directly translates to grams. 1 litre of water equals 1 kilogram.

It's better to go too big than too small, any extra displacement can be dealt with by adding lead ballast- this will also increase the metacentric height- which will give you a more stable boat.

[JWLaRue]

Just a bit of clarification

Just a bit of clarification to Andy's advice that may help.....

>>> In regards to the WTC, you need to size it to support the weight of your equipment and batteries.

At a minimum you need to size the ballast tank to be able to lift the weight of everything that is at and above the waterline. The weight of everything at and below the waterline would normally be countered by adding foam (at and below the waterline as well).

I'm fairly certain that this is what Andy meant!

-Jeff

[Guest]

Yes, fair enough. But it

Yes, fair enough. But it looks to me like the delta is going to be a dry hulled boat, therefore no room for foam!

Andy

[JWLaRue]

Ahh....a dry hull! No foam.....lots

Ahh....a dry hull! No foam.....lots of lead?

But even then, the ballast tank still only needs to lift the weight of the part above the wateline.

-tnx,

Jeff

[rcher]

Nope, wet hull. That way

Nope, wet hull. That way I don't have try to seal all 20 of those windows.

I'm planning on a WTC to hold the motor/battery/ electronics with an air bladder in the free flood area. I'm currently trying to figure out just how much room I have between the WTC and the hull for the bladder and if I need to offset the WTC to make room for the bladder. And/or a separate WTC for the motor. The lead will go into the keel box under the hull

Incidentially I just found a digital video camera that's about 3" sq that will fit perfectlly in the nose of the Delta.

[rcher]

BTW Can somebody show me

BTW Can somebody show me a picture or a drawing of a tic-tac buoy system? I am planning on using a radio failsafe but the failsafe will not bring the sub to surface in the case of a dead battery. The hatch on my sub does open so I'm thinking of having a backup failsafe using a tic-tac or whatever under the hatch.

[Guest]

BTW Can somebody show me

BTW Can somebody show me a picture or a drawing of a tic-tac buoy system? I am planning on using a radio failsafe but the failsafe will not bring the sub to surface in the case of a dead battery. The hatch on my sub does open so I'm thinking of having a backup failsafe using a tic-tac or whatever under the hatch.

Ahh, I stand corrected. I thought you may be using Norbert Bruggens Delta as inspiration, which is essentially dry hulled, with fore and aft free flooding sections.

All the same the principles for sizing a wet hull and dry hull are the same.

Personally I don't like using foam in my models, it looks like a bodge up IMHO. However it does work okay, and is useful if you want a small cylinder that transfers from model to model.

Seems to be popular in the States, but I've never seen foam used in any model over here in the UK.

In your case, I don't think foam should be necessary, unless you undersize the WTC! #

Regarding a failsafe/detector- have you looked at Davy's pinger?

Andy



Edited By Sub culture on 1091828412

[rcher]

Close, Norbert's Delta did inspire

Close, Norbert's Delta did inspire me but I'm doing my version of it based on the materials that I have to work with. The biggest difference between my version and his version is that he uses a water bladder inside his dry hull where-as I'm going to use an air bladder in the free flood area. We'll see how it works.

Yep, I've heard about Dave's pinger. I'm exploring my options for now.

[Guest]

If you have room on

If you have room on top of the WTC for the bladder to expand, you can experiment with a child size bladder as in my Alfa bladder video, http://groups.msn.com/ArtBrodersmodels/documents.msnw ,
or an adult size bladder, which wouldn't need to expand as high to give equal volume of water displacement. You might also want to use the expansion of the bladder, while surfacing, to raise open the hatch, if it is moveable. I use it to raise a mast in my Alfa.

[JWLaRue]

Andy makes a really good

Andy makes a really good point around sizing the WTC to minimize (or eliminate) the need for foam in a wet hull boat. This does make for a much cleaner looking installation.

My two most recently built subs (Type VII and Seehund) have virtually no foam in them due to being able to use oversized WTCs in them.

-Jeff

[tmsmalley]

You will need enough volume

You will need enough volume (of air) in your WTC to allow the cuff to expand since that is where the air comes from to inflate it. I also recommend leaving enough room so the cuff can open a switch to shut off the pump when the cuff is nearly full.

I imagine that the child cuff one will work fine since there isn't that much surfaced freeboard on the Delta and it is a relatively small model.

Since it also isn't very long - your cuff probably needs to be on top of the WTC - so makes sure everthing fits in the hull with the cuff fully inflated

Check out how Big Dave Welch does his on my website:

RC-Submarines - Big Dave Welch





Edited By TMSmalley on 1091879172

[rcher]

You know Art, that's a

You know Art, that's a great idea using the cuff to pop the hatch open! I wonder if I can use a pop-up figuire as well

I've built a separate WTC for the motor and have decided to use a 4" WTC for the rest of the electronics That will give me about 1.5" - 2" of space above the WTC for the cuff bladder.