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    Cheap, simple R/C sub, suitable for beginners - A Charlie Class

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    david f
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    Cheap, simple R/C sub, suitable for beginners - A Charlie Class

    Post  david f on Mon Nov 17, 2014 1:12 pm












    http://youtu.be/XWnMu2ikqQk

    http://youtu.be/7ZHnO3sqjPw

    http://youtu.be/VaUBZZ36RRc

    These photos and videos were taken yesterday at our pond in Barrow in Furness. I've put them in for a couple of reasons:

    - This Charlie class is my favourite for winter sailing - to keep my hand in. You will see me there every couple of weeks.

    - Graham B of Cornwall asked me another interesting question on the phone recently. "Can't you use ordinary plastic pipe to make up WTC's?"

    So it occurred to me that to cover the build of this type of project on here would answer a number of questions:

    - How to make up WTC's - the centre section of this sub is just PVC drainage pipe.
    - Simple fibreglassing  - the nose and tail cones and the sail are simple mouldings made originally on a foam former.
    - Making plastic disks (hopefuly on a lathe) - this makes the internal "Tech-Rack" and the bulkheads for O ring seals. (The basic method could eventually lead you on to making your own piston tanks.)

    So keep an eye on this section as I add to it. The finished model will not win you any prizes but I hope that the videos show that she is a fun model.

    David
    -


    Last edited by david f on Mon Nov 17, 2014 1:37 pm; edited 3 times in total

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    Re: Cheap, simple R/C sub, suitable for beginners - A Charlie Class

    Post  Kevin D on Mon Nov 17, 2014 1:24 pm

    What make are they?
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    Re: Cheap, simple R/C sub, suitable for beginners - A Charlie Class

    Post  david f on Mon Nov 17, 2014 1:34 pm

    Aaaahhh more to come young, Kevin!


    David

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    Re: Cheap, simple R/C sub, suitable for beginners - A Charlie Class

    Post  Kevin D on Mon Nov 17, 2014 1:45 pm

    The suspense will kill me!!!!

    Could this be a candidate for my new WTC?
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    Re: Cheap, simple R/C sub, suitable for beginners - A Charlie Class

    Post  david f on Mon Nov 17, 2014 1:55 pm

    Well the advantage is that this a preqel i.e it is already built. So I should be able to add content quite quickly.

    The design is hardly original or cutting-edge being published in Model Boats January 1976!

    The current model is the second reincarnation though. (The first one I built was as per the original design with flat hatches. I've never liked them since!

    Second episode tomorrow.

    David
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    Re: Cheap, simple R/C sub, suitable for beginners - A Charlie Class

    Post  david f on Tue Nov 18, 2014 1:42 pm

    The original design of 1976:



    Built exactly as per the original plans, note radio aerial of the period!



    Languishing in a  Foreign Pool!

    My thanks to John W and Ian O for these parts of the original plans. (They saw my post and sent them to me - Thank You!)







    The original design was OK for it's day. I did not like (and never have liked, since) the flat hatch approach. There was always a dribble of water in the boat. There were 32 bolts to do up and I still remember them! Flat hatches are fine perhaps if you rarely use or rarely open up your boat.

    The drawings show tantalising glimpses of another era - Decaperms with gearboxes and grease filled prop shaft tubes! Oh unhappy days.

    So the Mark 1 was consigned to hang up from a friends ceiling!

    The Mark 2 is heavily influenced by Norbert Bruggen's book and the use of a circular O ring seal with the split at the stern. Also out went the the forward hydroplanes - more trouble (connections etc.) than they are worth.

    I will cover nose and tail cones next week. The centre section is just a 28" length of 4" soil pipe. Very tough, very strong.

    Cut it to length. Oddly it is quite difficult to cut it square. I would suggest sliding a plumbing fitting on to help you mark it up.

    You now need 2 circular bulkheads into which you will cut a groove on the outer edge to fit an O ring.

    These form the bow and stern bulkheads.

    The next bit may seem to contradict the "Beginners" label because it is really impossible to do without access to a lathe. I say access because friends, schools and colleges often have lathes so you may not need to buy one.

    The whole subject of lathes is rather nicely covered in this Forum thread:

    http://www.theassociationofmodelsubmariners.com/t1187-looking-for-a-lathe?highlight=Lathes

    I have also seen somewhere a rather useful video on making endcaps (bulkheads)  by Andrew L.

    I use 6mm polycarbonate sheet for all these things including pistons for piston tanks because I just find it a nice material to work (And I was given a lifetime supply. A large sheet once used as a security window.)You can stick several disks together using Solvent Weld or (I think?) Superglue.

    You will probably use the Faceplate on the lathe to hold and machine the disks which need to be a snug fit (no slop) in the tube.

    You then cut a groove in the outer edge for the O ring. I suggest you buy some 3mm x 94mm O rings before you try the machining - there is a lot of trial and error.

    People spout a lot of numbers when it comes to sizing the grooves but the key things to remember are:

    - the groove needs to be about 1mm wider than the O ring. It is not very critical but the O ring must be able to "squidge" down.

    - the O ring needs to be proud of the surface. Probably best determined by trial fitting a piece of plastic pipe over the disk as you machine the groove. And remember you can't add any material!

    If you make a complete Horlicks of machining the disk, it can always be a spacer in your Tech Rack or even a drink mat!

    When you have machined the disks put the O rings on, smear them with some silicone grease and push them into the ends of your cylinder. This should give you a watertight and airtight seal. You should be able to push them in and pull them out with only firm hand pressure.

    And that is really the start of a sealed centre section, WTC or piston for a piston tank.

    Two more episodes next week.
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    John Wrennall
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    Re: Cheap, simple R/C sub, suitable for beginners - A Charlie Class

    Post  John Wrennall on Wed Nov 19, 2014 7:49 pm

    My very early attempts at making bulkheads before I bought a lathe, definitely possible.




    I see that most bulkheads have seals which seal in either the radial or axial direction so here is a variation.



    Two discs turned to fit inside the tube as normal, 1 drilled and the other drilled and tapped to allow them to be fastened together. Ignore the centre mandrel holes.



    Note the chamfers on the adjoining faces of the two discs, this is turned to suit the O ring.



    After greasing and assembling, slide into tube and tighten screws(Allen screws better). This compresses the o ring via the chamfer and it grips the inside of the tube.

    Small O rings under the Allen screw heads completes the sealing.

    This is probably more complex than a 'standard' bulkhead but it may be that someone can find a use for this idea....

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    Re: Cheap, simple R/C sub, suitable for beginners - A Charlie Class

    Post  david f on Thu Nov 27, 2014 2:57 pm

    3rd episode---------

    Firstly thanks to those who asked questions or given feedback to the first 2.

    John, Makes the very good point that you can make disks without a lathe. Yes, you can and re-reading the original notes I realise that I did do this for the original. In fact I am still using one! It is though much easier with a lathe.

    John's design for the expanding bulkhead is very interesting and I could see a number of uses. Temporarily fitting a bulkhead or blanking off a section of pipe for example.

    Andy L (Subculture) has been in touch via Model Boat Mayhem and provided this link for the video, I mentioned. Many thanks for that!

    https://www.youtube.com/watch?v=hWcryehE7EU

    So you have your two disks with O rings "in the groove" They should seal your tube effectively and so how are you going to use them?

    The forward bulkhead can be made to be adjustable. This is useful so that you can fit things in the dry bit of the WTC. It also means that you can adjust the volume of air in the tube, which means that:

    - You can adjust the overall weight of the boat (More air means more weight because your sub has to sink in the end!)

    - You can adjust the fore and aft trim of the boat because you can alter the position of the centre of bouyancy in relation to the centre of gravity. (The centre of gravity is the balance point of the boat in air. The centre of buoyancy is the balance point of the boat immersed in water.)

    In practice,the bulkhead can be temporarily fixed in position with sticky pads(stuck to the inside of the tube on each side of the bulkhead) but make sure that it doesn't move!

    I suggested the magic length of plastic tube as 28" because this makes the model rather more like a scale Charlie II. (More on the 1:1 model in later editions.) It also means that with the end caps on,the model is close to the magic length of 42"! (The typical width of a car seat.)


    This photo shows some main parts of the model (no not the bins!)

    You can see the forward bulkhead, main tube and bow cap.

    The forward bulkhead has a couple of additions . You can see 3 polycarbonate "tabs" stuck on the water side of the bulkhead. Once I have fixed the bulkhead position , I screw through the tube into these tabs to fix it firmly.

    Also note the cable. This feeds power into the WTC from a 12v lead acid battery, kept in the "wet" in the bow. It is connected through 2 brass bolts in the bulkhead. A smear of vaseline on the battery terminals and connections (positive side only) limits any corrosion - this arrangement has worked for many years. No need for waterproof switches - take the bow cap off and disconnect the battery!

    I have also used Lipos inside the WTC but I must admit I prefer the original lead acid arrangement.

    I will cover the stern bulkhead in the next episode.
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    Re: Cheap, simple R/C sub, suitable for beginners - A Charlie Class

    Post  david f on Sat Nov 29, 2014 10:34 am

    Episode 4 - the stern bulkhead

    No, I know that the first photo is not the Charlie, it is a actually a partially stripped down Nordenfelt but it shows the basic principle well. I have used a very similar principle in most of my subs.
    So we have the basic polycarbonate disk with an O ring seal around the edge. For the stern bulkhead an extra, larger diameter, disk is stuck (I use Solvent Weld) to form a flange - basically to stop the bulkhead being pushed in.

    To make the seal, just push the bulkhead in like a cork with firm hand pressure. (Buy your O rings by the way, O ring cord produces stiff O rings which are difficult to push in.) Taking it out, I just prize a small gap between the flange and tube and then pull it out. A lot easier than 32 nuts and bolts!



    You will also see that ALL the connections, controls, prop shaft etc  are made through this stern bulkhead. This makes life much easier too - that's also why I don't like bow hydroplanes.

    All these connections etc. are made in the same basic manner which I have used for a number of years - a brass M8 bolt with a 4mm hole drilled through the middle. This can be used by a 4mm stainless steel propshaft (with a Simrit type oil seal added - see later) or a 4mm nylon tube for air or water or a 4mm brass push rod for controls with a bellows seal (with a length of brass tube soldered into the brass bolt to take the bellows.) I am not giving too much detail here, have a look at the links at the bottom and work on the basic idea, perhaps.




    But what about Bayonet fittings, I can hear you asking! Well I use a poor-mans bayonet fitting. In the photo above, you can just see a shiny aluminium "pulley". I stretch an O ring around this (like a rubber band) to hold the tube and stern bulkhead together. It works fine and I am using a piston tank at the moment which generates internal pressure. (I have a large number of O rings left over from my days of Pinger and Hydrophone manufacture!)



    The photo above shows the O ring at the end of the tube section.

    It also shows another labour saving idea - Velcro stick on weights!

    Much easier to adjust trim at the pond, very little drag, and you can remove them to carry a heavy model to the pond. Buy the self adhesive version of Velcro - I got some on ebay.


    In conclusion, there we have a key component, the stern bulkhead to RELIABLY keep water out and allow controls etc. As I write this I am looking at the Charlie model all ready to go for tomorrow. Tested and sealed  up with my inflated balloon attached to leak test. (The balloon should stay inflated overnight.)

    One episode next week - making the bow and stern caps.

    David

    Some relevant links with more detail follow:

    http://www.theassociationofmodelsubmariners.com/t957-rubber-bellows?highlight=bellows

    A bit more detail about prop shaft seals:

    http://www.theassociationofmodelsubmariners.com/t266-prop-shaft-seals

    A very good UK supplier of O rings and oil seals:

    http://www.theassociationofmodelsubmariners.com/t410-simply-bearings
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    Re: Cheap, simple R/C sub, suitable for beginners - A Charlie Class

    Post  david f on Sat Dec 06, 2014 9:59 am

    Episode 5  Bow and stern caps

    A short episode this one, because glass fibre is covered in plenty of places. To see a master at work could I suggest this link:

    http://www.theassociationofmodelsubmariners.com/t460-css-pioneer

    However making bow and stern caps is a VERY good introduction to glass fibre work.

    I will cover the topic in two bits. How I actually did it and How I should have done it!

    The original article suggested shaping the sections from polystyrene foam. Covering them with masking tape (to prevent attack from resin) and coating with 2 to 3 layers of glass fibre tissue. It didn't even suggest turning the foam in a lathe (see Nigel's Pioneer link).

    And that is basically how I did it. I seem to remember coating the masking tape in wax (belt and braces.)

    The problem is that you are then left with quite a rough end cap which requires rubbing down. I remember much sanding while spinning it on my Dad's long suffering Myford lathe!

    So this is one problem with this approach. The other one is that if you ever need another one you have to make a female mould, in which case this is how you should have started in the first place!

    The photograph below shows my current collection of female moulds. Note that their are two for the fin. The fatter one is more scale following research on the 1:1 Charlie (See next week's episode).





    My suggestion  for how you should ACTUALLY make these is as follows (based on my early mistakes):

    - Don't start now unless you have a WARM outside shed. (Polyester resin is very smelly and needs warm conditions to set. You will not have a Happy Christmas if you start off in the Family Kitchen!)

    -Start by turning the caps (called a plug) from softwood on a lathe. You can use a wood lathe but a metal turning lathe can also be used. The maximum diameter of the cap is the Outside Diameter of the plastic pipe. Be careful not to have any undercutting - the shape should be  a smooth tapering curve all the way along. Remember that you will need to release the plug from the mould!

    - Make the plug as smooth as possible - sand it down. (Protect the lathe bed from grit!)
    - Paint it. Use paint that is not affected by resin. If I remember correctly, acrylic car paint (Halfords) is fine.
    -You may consider fixing the plugs to plywood etc. to form a flange around the mould. (See the Pioneer link for some ideas.
    -Paint the plug with 2 to 3 coats of PVA release agent, allowing to dry between coats. Some people suggest also waxing the mould but I have found that this creates more problems than it is worth. It is very important that you have a continuous film of PVA. Resin really sticks and you may be unable to release the plug.
    - Then start to build up your layers of glass and resin. Follow the various guides but I wouldn't suggest any shortcuts. Use gel coat, surface tissue and 2 to 3 layers of glass matt (cut into small pieces).
    -Some general points. I work outside (starting in Spring!), use a cut down paintbrush for resin, wear disposable latex gloves (thanks for the tip, Nigel) and old clothes. You can clean things with Acetone. (I think Nigel uses Paint Thinners successfully.)

    (This vision of me wearing latex gloves, old clothes and wandering around my garden in Spring has probably put you right off!)

    You can apply the various layers over the space of a couple of days. Leave the plug overnight and then remove the plug. Dunking and soaking in water helps the release.

    You make the actual end caps in the same way - applying the layers to the inside of a carefully PVA coated mould. You will find it more difficult working inside the mould. When you make the fin, use as little resin and glass as you dare. A common mistake (even in commercially produced hulls) is making them too thick and heavy.

    So there we have it. A bit of an "idiots" guide to fibre glass but it will start you on the path to an important construction technique in our hobby.

    A quick word on materials (very UK orientated):
    - Epoxy can be used but is still expensive in the UK.
    - Halfords have quite useful fibre glass repair kits but they lack things like gel coat.
    - A good UK supplier for everything you may need:

    http://www.theassociationofmodelsubmariners.com/t1403-glasplies-glass-fibre-and-resin

    Next weeks episode - some notes on the 1:1 Charlie.
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    Re: Cheap, simple R/C sub, suitable for beginners - A Charlie Class

    Post  John Wrennall on Sat Dec 06, 2014 7:32 pm

    Episode 5a

    May I offer up another method of constructing the nose and tail “cones” which could be helpful to anyone with an aversion to working in fibre-glass.

    I have used this method for two hulls already and another on the way as well as two torpedoes for my Biber.

    We will be working with plastic pipe only,  the photos are of a drainpipe size but the idea works just the same with 4 inch pipe. As the same pipe is used throughout, there is a continuity of diameters and thickness and plenty more pipe if things go wrong or if you wish to change the shape.

    Doodling the cone shapes wanted on a sheet of squared paper will help with the layout and the marking out.

    1.Using a short length of pipe, mark out and cut to shape. Note that the cut lines are NOT straight but a gradual curve. The example in figs 1 and 2 shows a six segment cut but 8 or 12 would give a smoother curve. Also figs 1&2 are illustrated with a toilet roll centre which was used for conveniece.  Think - smoke stack from Stephenson’s Rocket



    2. After cleaning up the cuts, position some sort of annulus ring on the prongs and press down and secure to give the required shape. Pour a kettle of hot water over the tube and leave for an hour or so to cool. Retain enough hot water for a brew.
    It should now have taken on a curved shape.



    3.Check and repeat 2 as necessary to get the shape you want.

    4.Glue and filler is now the order of the day. If the rear cone is for a single shaft then I always glue in a short section of tube at the rearmost point. This is to allow the prop shaft to SLIDE through to allow for easier assembly especially if the prop shaft is glued into the bulkhead. It does mean that a bulkhead is required to assist alignment.



    5.Bulkheads are made up from 3 discs of your favourite acrylic/whatever, the two outer disks turned to suit the inside of the hull tube, the inner disk diameter matches the outside of the hull tube. I glue the discs together with Plasweld and clamp the assembly. Plasweld very quickly evaporates so speed of application and clamping is essential. These bulkheads are made with AXIAL seals in mind hence the through-bolts. Rear bulkhead has prop shaft in the centre hold, Front bulkhead is fitted with a tyre valve to assist with pressure checks.



    6. The 6 radial countersunk screws shown in the rear bulkhead are to attach the rear cone. Hardy noticeable after the final paint job and this does allow a full maintenance strip down capability.

    7.Assemble all the components and carry out any final filling/smoothing/undercoating.



    Finally, a 4inch version shown below. After final smoothing and before being drilled for fittings, the cone was given several coats of varnish and used as a plug to make a glass fibre mould to give me the best of both worlds.



    Hope these notes are of use and promote further thinking and new ideas.

    Did anyone noticed 6 screws in the bulkhead and only 4 holes in the cone ??
    If you did then WELL DONE.
    (Not a fault, just 2 separate builds)


    Cheers for now

    John
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    Re: Cheap, simple R/C sub, suitable for beginners - A Charlie Class

    Post  david f on Sat Dec 13, 2014 9:40 am

    Many thanks John for posting the methods of making end caps from plastic tube - very useful. I liked the use of an electric kettle and boiling water to bend the pvc. (I used a hot air gun but your method is much better, cheaper and multi- purpose!) Following our conversation some years ago at Barrow, I used your method for the u-UPVC class submarine:

    http://www.theassociationofmodelsubmariners.com/t139-u-upvc-class

    (If people like the Charlie class PVC pipe idea perhaps try this one next as your first twin screw sub.)

    Episode 5: The full size submarine.

    This could be sub-titled as "Pimp my Charlie" perhaps!

    The 1976 Model Boats article does not give much detail  - not much was available then anyway. The Cold War and no Internet! That year I bought a Jane's "Pocket book of submarine development" which had a grainy black & white photograph and some information - a much improved design, quieter and able to do a submerged launch against a carrier battle group from 30 miles range. Charlie was of course a Nato codename the real name was Skat in Russian (Anyone know what that means? Most Russian subs were named after fish - rather sensibly!)

    Nowadays look straightaway at the excellent Wikipedia article:

    http://en.wikipedia.org/wiki/Charlie-class_submarine

    That includes the fascinating information that a Charlie was leased to India as the INS Arihant (Yes, it was Indian!) So you could build an Indian nuclear submarine.

    Looking at the first photo shows our first disappointment. The hull shape is not a parallel cylinder but more like the ideal (porpoise) submarine shape. Oh well I did say that you were unlikely to win prizes with this model - just have lots of low cost fun. This is confirmed with a nice little model they have at the Royal Navy Submarine Museum. (Did you see the piece on Reindeers in submarines on the BBC 1 show last night from the RNSM?)

    I settled with the Charlie II variant because as I said earlier, it seemed to fit my 4" diameter pipe, 42" car back seat scale better!



    Remember I said that you would always need to make several end caps and fins. Well the next photo is one of my secrets. One very simple fin for sailing with and one fin (with all the trimmings) for table display. (I also display these fins/conning towers in our downstairs loo!) This one is one with all the trimmings. The radars etc are made from that plastic that softens at boiling water temperatures, moulded onto aluminium rod.

    I prefer swapping fins rather than having all the complexity ( and top weight) of motorised mast raisers etc. KISS is best for this boat!



    And this is the real thing. (All these photos seem to have been made by someone craning out of a helicopter.)



    To finish off with some photos all from the internet showing useful details. (The middle one is from the Wikipedia article, I think.)

    Prominent features to note. Lots of big (noisy!) free flood holes. Prominent longitudinal ridges on the deck. (I stuck pvc sheet on the pvc tube and sanded it down.) Very brash and colourful hull painting (Rescue buoy etc) I scribed or Dremelled (carefully!) lines into the tube and painted them.








    So there we go. Lots of opportunity to put some detail on. It looks good on the water,always attracts comments and everyone can see it is Russian and they often think is is a Typhoon!

    A final word on painting. Go no further than Halfords acrylic car paints. Plastic primer paint followed by matt black or perhaps satin black.

    Next edition next week: Options on fitting out the internals.

    David

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    Re: Cheap, simple R/C sub, suitable for beginners - A Charlie Class

    Post  dgp1957 on Sat Dec 13, 2014 3:00 pm

    I remember having a set of these plans years ago, are they still available?
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    Re: Cheap, simple R/C sub, suitable for beginners - A Charlie Class

    Post  david f on Tue Dec 16, 2014 12:01 pm

    Nice question. Gosh, they are after all these years! Look here:

    http://www.myhobbystore.co.uk/product/16992/charlie-class-mm1210-submarine-plan

    Surprising but at £12.50  a bit steep perhaps?!

    I think I would regard my articles as a bit of an update on the original excellent concept.

    The flat hatch concept in the original is the main problem, in my opinion. I also felt that the Charlie II was easier to make a bit more scale.

    David
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    Re: Cheap, simple R/C sub, suitable for beginners - A Charlie Class

    Post  david f on Sat Dec 20, 2014 9:19 am

    Episode 6 - Fitting her out (This is the last episode)

    The original Charlie design drawing shows a quite large (4 Ah,I think) lead acid battery "in the wet" up in the bow. This is also the way I have it configured at the moment. Lead acid batteries work well this way (some of mine are 10+ years old) and are very easy to access. No need for waterproof power switches just connect the battery and put the bow cap on and you are away.

    Some would argue that this position for the battery raises the centre of gravity and puts it forward. True but you can compensate for that as we will see.

    The original design was for a dynamic diver and this is the way I operated it initially. (Those early swimming pool pictures.) This worked well. You have to have the sub trimmmed to an almost awash condition because the only downthrust (i.e like ballast) comes from forward speed. If I was doing it now I think I would go straight to brushless motors:

    http://www.theassociationofmodelsubmariners.com/t1427-going-brushless

    (I think I used a very nice (and expensive!) Pitman boat motor in the original.)

    Another slight advantage of the original "flat hatch" design is that you gain a bit of waterline from the hatch cover. (With the cylindrical version anything sticking up above the surface has a lot of displacement.)

    Probably a good moment to give some design princples:

    - Try to keep any superstructure (anything that sticks up above the surface) to the minimum displacement and weight (i.e use strong , light, thin materials. Fibreglass is not necessarily the best choice. I like tinplate and David J likes thin brass sheet.) Minimizing displacement reduces the downthrust needed for dynamic divers and ballast tank volume for static divers. Too much weight and your sub will try to wobble and turn over!

    - To minimize the weight of your sub keep the volume of air in the WTC to a minimum.That is why the movable forward bulkhead comes in handy. (Having some wriggle room helps. It is not unknown to find that your sub can only sink! I believe this happened to a full size Spanish sub recently after an excessive equipment fit!)

    - Don't forget about foam - it comes in very handy to gain overall bouyancy or to adjust fore and aft trim. (The use of foam and lead acid batteries in the wet were the two big things I learned originally from the excellent SubCommittee Forum.)
    Keep the foam as high as possible in the hull but it must not be above the waterline to avoid using up precious downthrust.
    Blue builders foam works well - stuck into position with silicone sealant. It needs to have a closed cell structure to avoid getting soggy.

    - If you are using a ballast tank keep it in a central (perhaps slight forward) position under the fin/periscopes.

    - Trimming a sub can be awkward because  a lot of these design principles interact. Don't forget that you can hold foam block and lead blocks on externally with rubber bands (or the Velcro I recommended earlier) while you get things right in the test tank.

    Back to the Charlie model. I find that foam in the bow cap is also useful to hold the battery in position. (You don't want that moving around.)

    I now use a piston tank positioned in a central position. I have previously used a pressure tank ballast system. They both worked well but a piston tank just has the edge, somehow.

    I use car type bullet connectors for all higher current connections. The aerial lead is just run around the WTC in a fairly random fashion. The earlier photographs show my installation - no, not the neatest but it works!

    Some modellers prefer to fix everything down and wire everything permanently having removed all the plugs and it looks lovely.

    So that is it. The updated Charlie. A cheap, easy model that will not turn heads on the exhibition stand but certainly does on the pond.

    If you like the Charlie design concept have a look at this for a twin screw U class that looks pretty good on the water: (The photo illustrates light superstructure on top of a pressure hull. Which is full size practice anyway.)

    http://www.theassociationofmodelsubmariners.com/t139-u-upvc-class



    Have fun!
    avatar
    John Wrennall
    AMS member

    Posts : 156
    Join date : 2011-11-16
    Age : 71
    Location : Leyland

    Re: Cheap, simple R/C sub, suitable for beginners - A Charlie Class

    Post  John Wrennall on Mon May 18, 2015 10:25 am

    John Wrennall wrote:My very early attempts at making bulkheads before I bought a lathe, definitely possible.




    I see that most bulkheads have seals which seal in either the radial or axial direction so here is a variation.



    Two discs turned to fit inside the tube as normal, 1 drilled and the other drilled and tapped to allow them to be fastened together. Ignore the centre mandrel holes.



    Note the chamfers on the adjoining faces of the two discs, this is turned to suit the O ring.



    After greasing and assembling, slide into tube and tighten screws(Allen screws better). This compresses the o ring via the chamfer and it grips the inside of the tube.

    Small O rings under the Allen screw heads completes the sealing.

    This is probably more complex than a 'standard' bulkhead but it may be that someone can find a use for this idea....



    An addition to the original post now that I have decided on a use for this adjustable bulkhead...

    I always seem to make a "pigs ear" of cutting large diameter tubing square and have now fitted the adjustable bulkhead onto a mandrel to enable it to be held in the lathe chuck. My chuck is too small to take the tube directly. This enables the ends of the pipe to be skimmed square.





    A second unit is currently being made with a central bearing to allow alignment with the lathe tailstock.

    Hope this may be of help to anyone who makes their own cylinders.

    John


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    Re: Cheap, simple R/C sub, suitable for beginners - A Charlie Class

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