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[allnightin]

That looks like the shipwrights model I saw !  Where did you see it please?  It does not appear to be on display at the Imperial War Museum any longer.

It was one of the old Model Engineering Exhibitions but I can't even remember if it was at Olympia or Alexandra Palace. 

It might be worth asking the IWM if there is any possibility of access at some stage to the model or any plans to pt it on display again.

[Subculture]

That model looks identical to the one at the RN Submarine museum at Gosport.

[Davy1]

There is a photo of a K class model in the latest issue of "Model boats."
I think it is in the feature on the Sandown show, if I remember correctly.
(it is funny how once you start looking they pop up everywhere!)

[tobyker]

No, the problem was that they didn't "pop up".

[bobk]

Manny thanks everyone.  www.rcmodelsubmarines.co.uk is an amazingly informative site, and has greatly helped my appreciation of what I am getting myself into.  It appears that with a hull of these proportions I will need two ballast tanks, fore and aft, with a proportional control system to effect trim.  Perhaps an automatic trim control to counter the K's natural disposition to seesaw / nose dive.  Sad there seems nothing 'off the shelf' to fit a 53 inch hull with only approx 4 inches i/dia and just over 3 inches i/height including keel. 

Maybe I should look for a system designed for smaller boats, fit one small tank forward, one aft, with a third admidships on a separate channel for emergency surface (similar effect to the K's droppable keels).  The volume and complexity of electrics looks vast.  As most of the hull could end up as WTC I will need to cast some metal ballast to fit into the keel space. 

I aim to visit the Submarine Museum at Gosport, contact the IWM, and subscribe to Model Boats.  Advice appreciated.

[Mankster]

I think you will be fine with a single ballast tank, and it doesn't really need to be proportionally controlled (though that is the gold standard).  A single ballast tank sysytem is something you can easily make your self with a reversible water pump and a bladder from a blood pressure cuff. A horizontal trim system is a good idea, as their is a lot of superstructure that will creat drag when under water and alter the pitch of the sub.. A sevro than moves the battery (or a weight) a couple of inches will be more than enough.
Oh and thanks for the plug

[Subculture]

Have you got a lathe, Bob?

Also get this book- http://shop.traplet.com/product.aspx?c=294

and also have a look at this website-

http://www.heiszwolf.com/subs/tech/tech01.html

[bobk]

No I don't have access to a lathe, although I served a 5 year apprenticeship as a toolmaker.  One reason I have tended to model with ABS & Perspex etc.
I think my best approach is to try to design and build a ballast tank system, plunger style, of a diameter able to fit the hull, although it still appears that as it fills from one end the fore & aft trim is going to shift massively.  I like the idea of using the battery as a servo-movable trim weight.  Once I have that working and watertight I can then start on motors and control surfaces in a separate WTC.  The whole assembly will need to be adjustable to determine 'neutral trim' before going any further.
Frankly, I would like to see something working first and discuss it to avoid an expensive hit & miss series of learning curve experiments.  A lot of time and cost that could easily end up in a terminal sequence of ripples with a final bubble or two.   The risk of total loss is very high. 

PS:  Has anyone else used Gyproc coving adhesive, a totally amazing modelling media for creating smooth blended curves and surfaces.  Smooths with a damp cloth.  Sets like concrete with a silky finish.

[Davy1]

Hi Bobk,
Thinking about what you are planning to do, I would suggest a fairly conservative approach to what will be your first submarine.
Build it first as a surface runner - it will look super anyway.
Leave at least a "1 litre shaped hole" just under where the periscopes will be. You can fill this with whatever ballast tank system you choose at a later date.
You can get guidance on different ballast systems from many sources including:
http://associationofmodelsubmariners.com/
Keep your superstructure as strong and light  as possible but with as little displacement as possible.
A lot of advice you will be given is from people who have never scratch-built a submarine - it can be a steep learning curve.
Hope this doesn't pour cold water on your plans but it could save a lot of cold water later!

David

[bobk]

Many thanks Davy1,
Sounds like good advice,  the more I hear and see online the more I appreciate how much of a "steep learning curve" this will be.   OK, I feel confident in building a very detailed display model, and fairly confident in taking the lower technical challenge of making it a working surface runner - perhaps then even a dynamic diver with it trimmed low after confidence built in surface testing.  One step at a time.  The basic hull is not that pricey, nor will the cost of 'surface' running RC for two props and a rudder.  Allow for adding dynamic diving planes later. ie: 4 channel, 40Mhz, etc

As you say, many of the wonderful videos etc I have seen are are for 'kits', although some of the scratch built ones are awesome!

Could I ask, do you think after this I should consider gaining experience on a pro-designed static diver package such as the Engel 212A?  That way I could have my dream K first, then next a static diver with a proven pedigree that I could learn the 'art' with. 

PS:  It was always my intention to build the K as originally designed, no swan bows, and with all 3 guns plus superstructure mounted torpeo tubes as photos posted by 'subculture' and 'allnightin'.

[Mankster]

With your experience, I dont think you willl have to much trouble building a working and diving submarine. Something like an Engel 212 I fear will be a rather simple, not too taxing affair (the Engel Lafayette is a little more of a challange and involves working with a GRP hull. If your keen on the engel dive system have a look at my Trafalgar thread (Its essentially a Lafayette internals but with two piston tanks and enclosed with a tube rather than making the entire hull waterproof like Engel)
http://www.modelboatmayhem.co.uk/forum/index.php?topic=14332.0

[Subculture]

Sad there seems nothing 'off the shelf' to fit a 53 inch hull with only approx 4 inches i/dia and just over 3 inches i/height including keel. 

There is the Merriman/Caswell sub driver/wtc built which is designed for the Revell Gato class boat.

http://www.caswellplating.com/models/sub-drivers.html

This has a 2.5" lexan cylinder, twin screw output and a large volume ballast tank which should be adequate to get you a scale waterline if you keep the upper works as thin as possible.

It's a gas/snort system, so no piston tank I'm afraid. Most of the dive modules/wtc's made by suppliers here in the UK are designed for larger boats, or those with broader beams.

In regards to losing your boat.- sail in clear and/or wadeable waters. Swimming pools are perfect,  London and Hertfordshire based Dive-in events give you access to such facilities. There is also Black Park Model Boat Club which is just down the road for you, and they have a lot of model submariners in their ranks- the lake is spring fed, so the water remains very clear, although it is deep. A local scuba club help recover models which fail to emerge for a modest fee!

[Davy1]

Subculture (Andy) is being a little modest. He is the one who runs the "Dive-Ins."

[Subculture]

I thought Bob might have picked that up from my  forum signature.

I've made it a little more obvious, so you can't fail to notice it now.

[bobk]

I thought Bob might have picked that up from my  forum signature.

I've made it a little more obvious, so you can't fail to notice it now.

Yes thank you, I had already browsed this site with interest.  I have just been down to Black Park Lake (it is big, and looks deep).  No one there, so try again Sunday.  I have got latest "Model Boats" mag (nice K boat in it!). 
The Merriman/Caswell 2.5" diameter sub-driver system looks interesting, but even if I ship it from the States getting gas cartridges here might be difficult?  A lot of valves to control.  How long does the gas last, and when it runs out ...   I will have to look up 'snort' systems.  I have emailed them questions.

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 

[Subculture]

Might be worthwhile getting in contact with the club that runs there. Here is a link to their website-

http://www.blackparkmodelboatclub.org.uk/

The snort system is very simple. To submerge a small valve located at the top of the tank is opened by a servo. The bottom of the ballast tank is vented so the water flows in freely, and down you go. To surface a small diaphragm pump blows air via a snorkel into the main ballast tank. This does mean your boat needs to be trimmed slightly positively buoyant, or you will have to drive your boat under power until the snorkel mast broaches the surface in order to blow your tank. This particular system was difficult to implement, at least in small boats until a few years ago. The miniature diaphragm based pumps were difficult to find, and/or expensive. This is no longer the case.

If you like to run negatively buoyant and assuming you're unable, or unwilling to drive the boat to the surface, then the on-board gas system can be used as a back-up. An on-board reservoir (which is constructed from copper fittings) is filled using an external aerosol can (e.g. airbrush propellant) via a schrader valve .The amount of submerge/surface cycles varies, but generally you will get about eight or more. What happens if you lose count? The boat stays on the bottom, and this is one of the weaknesses of the gas system.

[Subculture]

Do bear in mind that the 2.5" cylinder may not give you a scale waterline- it should get close. Not sure how much that matters or not.

[bobk]

Thanks.  I have emailed Black Park Model Boat Club.  Using a airbrush propellant aerosol can via a schrader valve sounds good, but getting it back to snorkel depth before you can blow the tank no so.  Can't you just vent into the water via the valve if needed as internal air pressure will be much higher.
I was intending, through extreme caution, to build to near-scale waterline depth, with maximum ballast keeping just the conning tower above water.  That way I can dynamic-dive the last bit whilst retaining some buoyancy in case all else fails.  Seems more controlable after my weighted coke bottle test.
I guess so much depends on getting a tank system into the hull, then filling the bath. 

[Davy1]

Andy's advice to join a club is very good.
Also don't worry too much about water clarity/swimming pools etc. A lot of us now use an on-board Pinger which means that, in combination with a hydrophone, you may lose your sub but you do get it back. Unlike R/C planes, helicopters etc!
I'm still wondering how to ease the entry into model submarines for you. You have chosen a difficult subject (size, complexity etc.) - K's are rare models for that reason. To counter this you are very keen on building one and you are a very experienced modeller.
I think that the route that you've identified - surface runner - maybe dynamic diver - then ballast tank will work for you.
And make her fast - therefore very impressive as a surface runner - 24 knots on the surface remember!
Hope to see you at one of the events which the AMS attends.(i.e not Dive-Ins) http://associationofmodelsubmariners.com/

[Subculture]

AMS members do attend the Dive-ins, alongside Sub Committee, BMSA and those who aren't affiliated to any organisation.

[Davy1]

You might very well think that; I couldn't possibly comment. ...

[Subculture]

It's not a thought David, it's a fact.

[bobk]

"You have chosen a difficult subject (size, complexity etc.)"  -  Yes, silly I know, but somehow the thought of a "build in a weekend" does not have quite the same appeal.  I am still crazy enough to hanker after retractable funnels too 

And make her fast - therefore very impressive as a surface runner - 24 knots on the surface remember!  - 
At 1/72 scale is that 1/3 mph ?  But I know what you mean, bow wash (LOL)

Hope to see you at one of the events  - 
I would be honoured to meet any experienced submariner at any event, whether pool lake or whatever organisation.  I aim to join the Black Park Club, but please note it could be a while until anyone sees me at the helm of a model steam sub.  Lots to do, but at least I feel am underway.  Thanks for all your input.

[Subculture]

You take the square of the scale and divide that by the full size speed to get scale speed-

For example the square of 72 is 8.5. Therefore 24 (knots) divided by 8.5= 2.8 knots for your K-class

Not ultra quick, but not a dribbling along either. To get a realistic bow wake (for photographs etc.) you will need to increase this speed further.

[Mankster]

Using a airbrush propellant aerosol can via a schrader valve sounds good, but getting it back to snorkel depth before you can blow the tank no so.  Can't you just vent into the water via the valve if needed as internal air pressure will be much higher.

Yes thats the way it works, you can blow ballast with the stored air brush propellent at any depth. If you want to save on proplent and use the snorkle instead, but you need to be at perscope depth (snorkle out of the water). 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.