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[Davy1]

Spot on bobk!

See you soon,

David Forrest

[kazzer]

Of course if your deeper you can give a short burst of propel to empty just a small fraction of the ballast tank that will take you back to periscope depth- where you can continue to blow the tank with the snorkle.

Yes, that's pretty much right. You're going to trim ballast your boat so the ballast tank is full of water and the periscope is just out of the water.

If you 'stop engines' then the boat will surface to periscope depth without any help from the gas reserve.  Only if the boat goes so deep that it become negatively buoyant and starts to sink, will you need the gas, and loss of signal (switch the radio off) will surface the boat from virtually any depth.

Normally, the boat will dive once the ballast tank is blown, and for deeper dives, the dive planes and forward motion will push it deeper. I guess you'd call that 'dynamic diving'.

[bobk]

I am now underway, starting with joining Black Park Model Boat Club today.   
http://www.blackparkmodelboatclub.org.uk/   Nice facilities, plenty of space, friendly welcome.  Very clear water.
Photo of Alan Rix and his ThunderTiger Netune at BPMBC:


Thank you to Mike Caswell of Caswell Plating for this link to plans & photos of the K class subs:
http://support.caswellplating.com/index.php?/Knowledgebase/List/Index/40/submarine-plans
 
Next step, work on the hull . . . 

[Albion]

Doing some basic 'sanity' tests using a 2L coke bottle with a couple of lengths of tube it appears that once the neutral/zero buoyancy point is exceeded the bottle sinks to the bottom rapidly.  Getting it to stay a few inches under looks tricky to trim for.
Hopefully on my next visit to Black Park I will meet some submariners 

Finding the neutral point is the hard part, and making sure its level. judious positioning of ballast and foam is the key.

[bobk]

Just to let you know I haven't lost steam on this project, just awaiting the K class hull to arrive from Deans Marine, and collecting beer cans.  I need to simulate the Caswell sub-driver to confirm it will fit in the hull before ordering one from the States.  A cylinder of 2.5" dia and 30" long.  Turns out I have found an excellent real ale simulation, exactly 2.5" diameter, so, I am enjoying the sunshine by my Koi pond carefully transferring ballast from the cans until I get the desired thirty inches total length. 
Can't rush it you know.  With all ballast transferred I will then glue them into a card tube to effect the simulation.  I now have a number of cans of different length, but the same diameter.  Very technical approach    Photo to follow in due course.
I just wonder how many build projects start off requiring a precise consumption of ale ?

[Subculture]

Oh lots and lots, it's remembering the master plan the next day which is the tricky part!

[bobk]

Attached are photos of my dimensional simulation of the Caswell sub-driver unit, 2.5" diameter and 30" long, made from empty beer cans.
When the hull arrived I thought this looks a lot larger than I had visualised, but fitting the simulation model it was a very close fit. Not too much space left for fitting frames, lead ballast, or running a rod through to the front diving planes.
I also need to make up a waterproof gear set to drive two props from a single motor.  Ideally I would have liked separate motors.  Any ideas?





This is going to be a real challenge, even getting the upper hull to fit snugly yet be readily removable for access will be interesting.   

[bobk]

PS:  You may have to double-click on the above images to see the whole image

[MikeW]

Why not get the version with 2 motors (the one for the Gato- also 2.5")?

[Subculture]

Yes what Mike said.

What you now need to do is remove a section that is equal in volume to the 2.5" subdrivers ballast tank and see what happens to the waterline when you dip it in the bath...erm test tank. Don't forget to take into the account the future superstructure, and allow yourself 10-15% extra for fudge factor.

I'm sure that if required, a special sub driver with a larger tank (if required) could be built, so there is some flexibility.

[bobk]

Many thanks Subculture & MikeW.  I have since spoken with Mike Caswell in N.Y.  He was so helpful. Some on the online pics are a bit small to appreciate, and also the latest twin-motor Gato sub-driver is three inches shorter, which should making mounting easier as it was the ends that got tight for space in the hull.  Also, should give more flexibility for fore and aft positioning.
It turns out the Gato is only one inch difference in length, and is also fairly slender.
Next step will be ordering the sub-driver, then making up internal frames.  Getting the balance point between centres of gravity & buoyancy should be interesting. I guess this will require a mock-up in water (yes, bath tub!) simulating weights for internals and superstructure.  Should I get the actual speed controllers, receiver & batteries etc, or start off with with using equivalent sized weights?
Dumb question:  What is 'blue foam'?  I understand I need this to get buoyancy trim right.

[Albion]

It will be worth you have a surf around the Caswell website for the Cabal reports, particularly the one related to the alpha submarine. There are som e clear details on how to work out the best place to locate the sub driver

[Subculture]

Blue foam is just expanded polystyrene, tinted blue. Also comes in pink and white. Bear in mind this foam is denser than the expanded polystyrene foam your average new TV set comes packed in.

In the States, they use it a lot for home insulation, so it's easy to get. In this country we tend to use polyurethane foam which is partly filled with ground glass, this tends to be yellow in colour. You can use this for buoyancy, and then glass over it to make it a bit neater. The other option is the expanding polyurethane foam you can buy in a tin, although that can get very messy very quickly.

If you want high density polystryrene foam in a smallish quantity, EMA model supplies sell it. http://www.ema-models.co.uk/index.php/materials/foam-polystyrene/expanded-polystyrene-sheet.html

One more thing- don't try using polyester resin with polystyrene foam- it melts it. Polyurethane is fine, you can glass straight over that.

[Davy1]

I've just been taking a look at the Caswell Subdriver and although it looks excellent for a plastic kit conversion, I do wonder if it the best thing for your K class project.

(If you have just sent off your order please ignore this message!)

Even with 2 x 385 motors installed it is going to be  a rather slow K class and $450 is also an expensive learning curve.

I wonder if you wouldn't be better off operating it first as a surface runner and doing some experimentation with the drive motors, props etc. (Basically squeezing them (it is a narrow hull) into a stern WTC.)

You will then get the most important thing about the model submarine right fairly painlessly - a fast destroyer with some diving ability.

Hope you don't mind me saying this but you did ask for advice.

David

[Subculture]

3 mph on the surface, and about 1mph dived scale speed.

You really will need a shoe horn to get bigger than speed 400 can motors in though.

[bobk]

Appreciate your advice David.  No, I have not sent off the order yet. Waiting for quote + shipping.
My thought was that by using a ready built driver unit it might save me numerous iterations of ripping stuff out and trying something else.  A vast number of multiple unknowns here.  The GRP hull is quite thin walled, and the video on the Gato page appears a fair speed.  I want it to look realistic, but I understand power is needed to drive it under if not trimmed to decks-awash.  That alone will be a corker to achieve I expect.  
Designing and building a three-chamber WTC with all the glands for controls and shafts etc may be a bridge too far.
Cost is high, but that would be well worth it if it achieves the objective with less back-to-drawing-board 'sinkings'.

Subculture:  With a 2.5" outside diameter WTC maximum motor size is hard to achieve, I agree.  I could cheat and use a single C/L prop but that would spoil the realism.

Without all your help this project would have been vastly more difficult.

[Mankster]

Its the wetted surface area that will determine the power needed to move the boat once its under so there should be little differance in the performance between the Gato and the K if they are similar sizes. If you decide to get the Subdiver, and for some reason find it underpowered, you could try swapping the motors with some 400 sized inrunners which should be a straight swap.

[Subculture]

Doesn't your Trafalgar class use a geared speed 480, Ramesh?

[Mankster]

Smaller than that, its a single geared 385 motor. Its the same drive system Sheerline supply with thier 1/64 Trafalgar kits.

[Subculture]

Ah right. Well there you go Bob. One 385 motor is sufficient to propel a 1/64th scale Trafalgar class at reasonable speeds. Two in a 1/72nd K-class a boat of considerably smaller cross section, should cut the mustard.  

[bobk]

Ah right. Well there you go Bob. One 385 motor is sufficient to propel a 1/64th scale Trafalgar class at reasonable speeds. Two in a 1/72nd K-class a boat of considerably smaller cross section, should cut the mustard.  

Wow!  That could turn it into a torpedo tube launched Harpoon cruise missile !  Do bow planes work as aerofoils in catamaran mode I wonder 
Would certainly generate some bow wash.

I am definitely leaning towards adapting the Caswell system.  They even do set of M1 fittings as a kit, rudder, bow planes etc, at same scale.  Near enough identical to the K boats.  Westbourne do 3 blade brass propellers of almost exact size required (must check photos to see if they are 'c/w or ac/w handed').

I need to figure out what is the best 6 channel 40MHz TX/RX system to use, without further breaking the bank.  Ideally one that could also run a twin-prop WW1 destroyer of similar size I have just acquired on E-Bay.

[Albion]

Don't forget these are only 25mm diameter props, they wont need much to make them spin

I just took delivery of my M Class from Caswell, complete with the fittings, will try and post photo later.

At the same time i took delivery of one of the WTC for the Revell type VII (which i have half built), its a very very long shot, but i'm going to dunk the upper hull and sail in a tank to find its displacement, then see how much the ballast tank holds

[Subculture]

I recommend prop shop for props, Bob. Not only are they very nice lost wax cast, so all one piece and with nice defined blade profiles, but they're also well documented.

I'm not sure if the Gato SD uses direct drive motors or geared- Dave Merriman tends to use both approaches depending on the application. If they are direct drive, go for a moderate propeller pitch, no more than 1.2x diameter, perhaps less. If you have a word with Simon at Prop Shop, he'll also advise on the best prop pitch for your application.

Andy

[bobk]

Whilst my K Class is under construction I had my first RC outing in almost 40 years, at Black Park Lake today.

See new topic http://www.modelboatmayhem.co.uk/forum/index.php?topic=29971.0 for photos.
An R Class destroyer of similar WW1 vintage, and almost same model length.
At least I have something to sail whilst the K is on the slips 

[pugwash]

found a nice photo of members model K4 on edinburgh MBC website

Geoff

http://www.edinburghmodelboatclub.org.uk/members_models/03.jpg