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[bobk]

Thank you Geoff.  Very nice picture.  Beautiful model. 
Bob

[bobk]

Quick update:

I have now bitten the bullet and ordered the Caswell sub-driver.  This includes motors valves and servos etc, plus M Class rudder and diving planes.
After much research nothing else will physically fit (2.5 inch diameter max) and I don't have access to a lathe etc to start 'inventing' my own WTC.

I have been given to understand that there may be only two other working K's seen at events around Britain, both in the north, so this could be something more special than I had anticipated when I took on this self-challenge.   

In the mean time I am working on my HMS Skirmisher, rebuilding the internals and electrics, and bringing it back up to spec.  Missing boats, davits, etc.  This will also be fun, and give me something to sail on nice days whilst the K is in the prototype dock.

I intend going up to St Albans for the Dive Into Summer event on June 12th.  I hope to learn a lot there

[Subculture]

Ah top man.

Not only will the k-class be unusual, so will the Caswell/Merriman Subdriver. Most submariners over here tend to go for Sheerline, OTW, Engel or a DIY approach. I've seen pictures of one or two modellers up North with a Sub Driver in, but never down here.

[bobk]

I am more than excited !  My sub-driver package has arrived from the States.  It really does look very well made, and fits the hull nicely.
Wow, there is a LOT of electronics in this, and at 2.5" inside diameter it will require very careful building.  As you can see I did go the whole hog, rather than get enough just to get it going then try to add extras (which I will probably need anyway) later.   

(click to enlarge)
Pictured above is the Caswell/Merriman SD25G Subdriver with installed twin motors, gas system, servo frames, snort valve etc.
Supplied separately are 6 micro servers, snort pump, rudder and diving planes from M Class model (identical to K's), pump controller PCB, self leveller module, drive couplers and linkages etc.
The primary dive system is the snort valve, which I intend plumbing into the tall forward radio mast. The gas system is to blow the ballast when below snort depth, which hopefully will allow many snort-depth dives without expending compressed gas.  Gas used is from a regular airbrush aerosol can through a Schroeder valve at the top of the WTC.

I also took the opportunity to buy the WFly FT06-C 40Mhz 6 channel radio control, which at US$89 (£55) works out to a fraction of the cost of a Robbe F14 equivalent. 

All-up that lot dented my Card to just over five hundred including shipping, but looking looking at many of the kits I've seen with built in sub driver I believe this represents excellent value, plus I could have paid well over 200 just for the radio control.

I intend having huge fun with this build, which will be over a long design & test period.  I am already working out how I am going to retract the funnels before diving.  Tee hee !

[Subculture]

Looks good. I'd say your first job, once you open all the packets, is to make a set of saddles for the subdriver to sit in. Retracting funnels shouldn't be tto hard- they swung in an arc I believe. Couple of miniature servos should do the trick, with a servo speed controller to slug the action a bit.

[bobk]

Good advice, thank you.  I intend getting a Profile Template first so I can accurately replicate internal bulkhead profiles.  I will leave plenty of fore and aft latitude for balance adjustment.   One major problem is that the set came with effectively no instructions or photos, so figuring out where the 6 servos etc get mounted, actuating rods, how they seal through the WTC etc, could be sheer guesswork.  Hopefully I may see a similar subdriver at the St Albans Dive-In so I can take photos and notes !

It appears that after building the WTC unit I should test that as a stand-alone unit.  I found this video of a single motor version on YouTube . . .
http://www.youtube.com/watch?v=UNVHt5r567Y&feature=related
Please bear in mind that this is a total first for me 
Any and all advice greatly appreciated !

Funnels:
On the original boats the funnels retracted through 180', with circular watertight hatches closing, also by 180'.  (See diagram)




With both funnels requiring 180 degrees in opposite directions, some kind of geared or compound linkage may be required to translate a 90 degree servo arm movement.  As I said, an interesting problem.

[Subculture]

Servos can operate over 180 degrees, but you need a servo extender to increase the throw, as RC receivers only operate over 1ms range which gives you the 90 degree throw.

Or you can apply gearing, but that will mean you need to slow the servo down even more. BTW, I find digital servos are much smoother when slowed down than analogue models- I think the higher pulse rate helps there.

With regards to instructions for your Sub driver, don't forget there is a dedicated forum for all things Merriman/Caswell- http://forum.sub-driver.com/index.php

You can talk to the man himself there, post some details up of what you're building, I know this will interest Dave. I'm also sure there are specific instructions for your Sub Driver- David is good with that sort of thing.

I use a profile gauge, and also soft solder for lofting lines for templates. Then I use old cereal packets to make templates from before committing to expensive material.

Andy

[bobk]

Andy,  you are a real Star !
I have registered on the sub-driver forum, posting the kit photo above and asking for assembly instruction help. 
In the mean time I will get a profile template for the mounting bulkheads.  Good idea about using card to check fit first.
Thanks too for servo info.  This will need my best Bagpuss thinking hat, but that's half the fun of building a concept instead of just a kit.

[bobk]

Thanks again Andy.  I now have very detailed build instructions in PDF format, plus links to some extremely useful build videos.
For anyone interested in using a Caswell dive system I hope they will not mind me giving links to their published information.

Sub driver instructions:
http://support.caswellplating.com/index.php?/Knowledgebase/List/Index/35/sub-driver-instructions
Very useful videos
http://youtu.be/_IgZ_M5t2l0
http://youtu.be/-qo-Hs3Bl0I
http://youtu.be/wSqcUBQy1ac
http://youtu.be/lifC6S4sbuE
http://youtu.be/L5ayOY4mb1M
http://youtu.be/lifC6S4sbuE

[bobk]

A pause in posting whilst I did a lot more research.  I now understand much more on how the WTC goes together thanks to Dave Merriman.  Hopefully I now have enough info to work out the technical interfaces between the WTC assembly and the hull, enough to get underway.  The tube is a very close fit in the slim hull.

All electrics bar the battery is in the rear 'dry' compartment.  Therefore the retracting funnels and retracting front dive planes should be operated together from the same servo in the rear of the WTC.  
Working out the linkages for the funnels capturing still shots from a video clip . . .

The object is to retract the funnels and extend the dive planes from their slots in the hull via a dedicated Rx channel prior to trimming down for diving.

On this boat building the hull togther with building the WTC appears essential as otherwise I would end up cutting a lot of holes then have to fill some in and cut them again in slightly different positions as the WTC cannot be moved.

[bobk]

K9 Back On The Slipway:

Main slipway cleared following destroyer completion, the dockyard is now set up for the construction of my K9 to recommence.   The submarine went on temporary hold late October whilst I pondered some basic sub-specific technical problems, and gained more model making experience building a surface warship.



Here are the main design problems I am working on.  Sorry, it’s a bit long.

WTC Positioning:
The WTC is a good fit in the hull section, but does have a limited fore and aft positioning ability.  I know I have to get the balance point for centre of gravity and centre of flotation fairly exact otherwise it will submerge bow or stern first.  I can build in supporting rib frames so as to allow fore and aft movement, but cannot connect up shafts or control linkages until I have got that right.  I assume at this point I aim to get the framed-hull neutral ‘tip’ buoyancy and concentrate on the WTC ‘balance’ first.  This appears to require building and commissioning the WTC first.  Choice and weight of battery appears most critical.

If I start with a temporary dynamic diving solution then by the time I get that far into things there will be far too much to rip out and rebuild for static conversion.

Internal Framework
I need a series of frame ribs to strengthen the hull, “U” slotted to mount the WTC, and also securely locate the upper hull.  Matching inverted “U” frames in the top hull, and strengthening beams along the length of both.  The ideal being locating lugs at the rear, along the joins, and a single thumbscrew fixing at the front (maybe a deck gun?).   I could use either 3 mm ply or 3mm styrene, neutral buoyancy being a factor in choice of material.

Control Linkages:
Unlike a Neptune or Engel ‘front end fit’ system, once the WTC is built in it cannot easily be removed without significant disassembly.  Control linkages will run in tubes through the rib frames, especially to the bow as all servos are in the rear compartment.  Bow hydroplanes need to turn and retract, plus control rod to geared funnels retraction.  With the WTC so time consuming to get out, especially at a lakeside, ideally I could do with a means of turning on power and charging the battery that avoids disssassbly.

ie:  Magnetic power switch, or stainless stud terminals with an external swivel “U” link.  An extra stud for neutral, and I could charge battery using croc clips.

Finally:

Static Dive System
The Caswell WTC comes with a gas bottle system, plus a snort system that I intended using the radio masts as air intakes for.  However, I understand the gas capacity only allows for 2 to 3 surfaces, and if I slip below snort tube depth the snort will not work.  Should I opt for a water-pumped bag system instead?

Am I thinking on the right lines here ?

[Subculture]

WTC positioning- the c.g on this boat is bang central on this boat, so mount the cylinder so that the centre of the ballast tank lnes up with that, don't worry about other equipment at this stage, when it's all in, you will use lead to balance the boat at the centre of the tank, and dial in the correct c.g.

You will then adjust the centre of buoyancy using foam or floatation cylinders (depending on preference).

For strengthening ribs I would use plastic or better still fibreglass sheet- much stronger. I would not use wood at all, and don't worry about the density.

Design the boat so that items are relatively easy to disassemble and remove. The whole idea of a cylinder system is that it's easy to hook in and out of a boat

Please don't charge batteries in a sealed container, it's not safe.

The concept of the snort/gas ballast system you have, is to only use the gas in an emergency situation. A water pump system won't fit in the confines of that cylinder.

[bobk]

Many thanks Subculture:  As I'm sure will be obvious to all -  this side of model boating is all new to me but I am determined to succeed, especially after being inspired at the St Albans Dive In last year !

WTC positioning at exact centre.  That means I can get started on sheet fibreglass bulkheads.

Fair comment on not charging battery in situ, but does mean I have to figure a way of disassembling all the WTC connections to get it out.  Pity the narrowing hull width at the front hydroplanes precludes a front exit using magnetic couplings at rear.  I will have to have more thoughts on that.

On the ballast system, my inexperience is bound to encounter ‘emergency situations’ frequently at first.  OK, if I need to blow gas (even once) then bring it in to recharge the air tank.  Hopefully, when I get the ‘balance’ and trim right, 140 mm radio masts should give a reasonable snort length.  I might even make them much longer to start with.

Bob K

[Subculture]

How high can you raise the WTC above the hull bottom?

[bobk]

How high can you raise the WTC above the hull bottom?

The WTC effectively rests on the inside of the hull bottom with only 3 mm clearance under the upper hull.  There is a small void space within the keel but this ends about an inch past each end of the WTC.  Might be able to route hydroplane rods through that if cranked.  Alternatively there is quite a lot of space alongside the WTC, 20 mm at centre narrowing to 5 mm at WTC front end.

[Subculture]

Can't you run the linkage for the front planes across the top of the cylinder?

[bobk]

Can't you run the linkage for the front planes across the top of the cylinder?

Sounds like a good idea, I can try that.  Alongside cylinder top, so I can pull WTC upwards to extract

Photo of WTC front end in hull.  A lot more space halfway along hull, but narrows fore & aft.  
Cut edge is widest part of section profile.  Modern subs tend to be more circular in section.
 
Bob K

[bobk]

I think I can see possibilities here !   Maybe if I attach the control rod tubes to the WTC, then I only have to disconnect at the front end.

[Subculture]

If you connect up with the magnetic connectors throughout, then removing the WTC from the hull should be a quick affair.

[bobk]

Eeeem.  That’s rather sunk my design for retracting funnels using two sets of servo gears, brass tube rod and plates.  This was intended to be mounted on top of the WTC to get a precise ball joint linkage, with the upper hull lowered in place over it.  Now I shall have to look at a flexible Bowden cable to a sub frame inside the upper hull.

The motor shafts are 4.8mm dia with a pronounced D flat, which I have to devise a way of connecting to 2mm prop shafts via universal joints angled at about 5 degrees each, and add magnetic couplings.  Will they take power?

With only a single day oogling inside peoples submarines I am now trawling Mayhem and Google to find photos or diagrams of control linkage set ups.  Surely it should not require almost total disassembly at the waters edge, comparable to having to remove a cars engine and transmission just to turn the ignition or fill with petrol?  One lost grub screw and its pack up and go home.

Bob K

[Subculture]

The driveshafts are usually coupled using dog and bone couplings, not magnets.

Most submarines don't have much going on like retracting funnels, but watch the weight up top if you're using brass.

I would study the Revell Gato conversions, as the two boats share a lot of similarities- twin screw, forward and aft hydroplanes, single rudder and a high freeboard.

[merriman]

Magnets can be useful.

[bobk]

Wow Dave, those photos were really useful.  Many thanks.    
I see the motor shaft uses a ball joint (readily disconnectable) so the magnetic couplers are just for the control rods.  I like the way both 90' and 180' transitions are done in your pictures, and especially how the geared forward dive plane retraction is done.  Burning question now is - can I order a fairly comprehensive selection of these through Caswell ?  Please PM me if this is possible. I could link my funnel retract gearing through a rod inside the upper hull, using a right angled magnetric coupler. 
I do have some ball joint couplers, and could drill these out to fit the motor shafts. 

Thanks again !

[bobk]

Most submarines don't have much going on like retracting funnels, but watch the weight up top if you're using brass.

Thanks.  I know hankering after working funnels maybe dumb at my level, but I can't resist it.  Now, if I can get the boat to go up and down too . . .

[merriman]

Wow Dave, those photos were really useful.  Many thanks.    
I see the motor shaft uses a ball joint (readily disconnectable) so the magnetic couplers are just for the control rods.  I like the way both 90' and 180' transitions are done in your pictures, and especially how the geared forward dive plane retraction is done.  Burning question now is - can I order a fairly comprehensive selection of these through Caswell ?  Please PM me if this is possible. I could link my funnel retract gearing through a rod inside the upper hull, using a right angled magnetric coupler. 
I do have some ball joint couplers, and could drill these out to fit the motor shafts. 

Thanks again !

You're welcome.

Drop the practical funnel-closure-valve mechanism.

FIRST: get that boat working in the water! Don't load it down with gadgets and crap. Not till you have the boat running, and the 101 bugs you're going to encounter worked out, anyway. Only with the boat working well can you get fancy with the funnels and shiny stuff. Keep it simple, learn the boat.

Crawl, walk, then, and only then, run, damit! Practical funnels and the like is, 'running'. You are not ready.

I don't have time to e-mail and PM. My time is precious: I'll spout off in public. It saves me having to repeat myself. And you, don't you be shy about reviewing the FAQ's at this and other related forums. You'll find most of your questions have already been answered, decades ago. There's nothing new here other than the faces of those who come and go.

And don't post so much. Every minute staring at the monitor and banging on the key-board is a minute out of the shop! Get to work.

David