A Skipjack in Ireland

[The Boattrainman]

I will need a 'tech' rack, to mount motor, servos, piston tank etc. etc. I'll use the 3.2mm styrene to make a 587mm long (600 mm less 6.5mm each for the end caps). The rack is in two pieces which will be bolted together, a smaller one for the motor and servos and a bigger one for the battery and piston tank.




The rack which is 82mm wide, will sit on half round shapes to 84mm diameter, I'm using this handy circle scriber to mark out full circles which will be cut across at the 82mm points




This is the rear of the rack, the raised box will house the drive motor which will be mounted upside down to put most of it is weight at the bottom of the cylinder, as well as helping with buoyancy, it will give me a small bit of space on top for other items. The motor spindle is off centre due to the 6.1 gearbox which makes this possible.




The Boattrainman

[The Boattrainman]

The 84mm plain discs are again cut from 3.2mm styrene sheet, they will sit inside the 90mm tube. Making them perfectly round is tricky without a lathe, but the 'O' Ring itself should take care of any minor flaws.




I'll wait for the tube to arrive before bonding them to the end caps.

The Boatrainman

[The Boattrainman]

While I'm waiting for parts to arrive, I'll have a go at making the end caps for the WTC. The key component will be a compressed 3mm nitrile 'O' Ring at each end of the tube

There are two ways to go here, threaded rod from one end cap to the other either inside or outside the WTC, there are disadvantages to both.

Inside rods will mean four extra holes in each end cap having to be sealed against water (four small circles inside the 84mm inner diameter), outside means extra width that the hull barely has to spare (the four dot points inside the semi-circles outside the 90mm outer diameter).

So here is a go at end caps with outer rods, the first job was to make a paper template to see if it would just fit inside the Skipjack hull.





The paper dimensions area transferred to a sheet of 3.2mm thick Evergreen Sheet (Plasticard), and then carefully cut out with a heavy duty blade.

The centre hole (which will eventually allow the motor shaft exit) and four outer holes were pre-drilled with 1mm pilot holes before the final cut out below. The outer holes are then opened a bit at a time with 1mm, 2mm and finally 3mm drills (for 3mm threaded rod).





All the tools to do this job are below, and more importantly it didn't require a lathe (I haven't got one!). The cap needed a fair bit of tidying up with various sandpapers as cutting 3.2mm styrene is messy.The completed end cap is seen with the paper template, now to make another identical one, plus the two round inner caps that will keep the sealing 'O' ring in place.




The end cap sits on a roll of tape to illustrate how it will sit on the end of the 600mm X 90mm tube.

The Boattrainman

[greenman407]

Looks like its going to be an interesting build.

[The Boattrainman]

Hi Greenman,

The gratings are detailed on page 1 and 2 of this log, all brass mesh and plastic strips.

There were some happy coincidences in going down the route of building my own WTC. The Caswell upgrades are suited for the 3.5 inch Subdriver, and there is 90mm Acrylic Tube (approx 3.5 inches) freely avaiable over here, plus the Engel Piston Tanks are 75mm in diameter with an additional 2.5mm for the motor overhang, so it will just fit in the internal diameter of the Acrylic Tube (84mm when you factor in the 3mm tube wall thickness).

Here is the Engel Piston Tank, a paper template is in the pictures above.





I've used these tanks before, they are 100% reliable and function exactly as Engel specify, plus they'll make one to any volume you want.

One step at a time, I'll get the WTC built and tested first before I purchase (as they are not cheap, but worth every cent for what you get).

The Boattrainman

[greenman407]

So some good and bad news with the first of many Primer coats, which will be done with acrylic spray cans (Humbrol range).

[ATTACH=CONFIG]n114091[/ATTACH]


The main seams have come out quite well and will need just a small amount of work, there's a seam running top to bottom here, nearly invisible.

[ATTACH=CONFIG]n114094[/ATTACH]


The Photoetched hatches and ballast vents add nicely to the main deck.

[ATTACH=CONFIG]n114092[/ATTACH] [ATTACH=CONFIG]n114093[/ATTACH]


The scratchbuilt inlet gratings look reasonable now they have blended in.

[ATTACH=CONFIG]n114095[/ATTACH]


However, there is a serious problem with the nose! As well as the obvious line where the two halves meet which can be filled, there is a dip along this seam resulting in the rounded shape having a flat in it around the entire nose, plus (to my eyes) the nose is slightly an odd shape, with the most forward part having a slight bulge outwards again spoiling the teardrop shape. It's not a biggy, but it will need some work to get it properly 'rounded', but it's the only flaw in what has been an excellent kit so far.

As for the flat meeting of the two halves, I can't see any solution other than some serious filling/sanding.

[ATTACH=CONFIG]n114096[/ATTACH]

If you enlarge the picture up a bit, you can clearly see a flat spot to the left of the torpedo doors at the seam.

The Boattrainman

Wow! Those inlet gratings look Fantastic! How did you do that?

[greenman407]

Your model looks very good. Now that you have determined your course of action,success is easier to achieve. I look forward to seeing your progress.

[The Boattrainman]

Happy New Year!

So after a lengthy hiatus, I will be re-commencing my Skipjack build. I had to suspend the build and log due to work commitments and I used the small time I had available to finish the small details on my Ben Ain (Mountfleet Models), all those tiny details take a lot more time than you think.

Anyway, here is the Skipjack in primer, the hull is basically finished, with the all planes, rudders, lights etc working.




So I've spent a lot of the last few months mulling over the WTC and how to power and control the model, and I've decided to build my own WTC. This decision is based on a number of factors including the cost of buying a commercial product. For example, I had considered the Sub-Driver but the cost of delivery from the USA to Ireland plus the import taxes made the purchase prohibitive, the decision was taken out of my hands when production ceased anyway (for now at least).

Secondly, I want a challenge, having built the Robbe U47 (as U203) and converted it into a static diver with an Engel 750ml Piston Tank, I think it's not beyond my skills (hopefully). Also, I'm going to try to buld this for the minimum cost possible from items readily available to anyone (Ebay etc.) and be asthetically pleasing and more importantly watertight. So to get the ball rolling, I've mocked up on paper all the main WTC dimensions, with a 500ml Engel Piston Tank inside a 90mm diameter acrylic tube (3mm walls) plus various control items, Piston Tank controller, receiver, main battery, servos, drive motor, etc. etc.). Control items will be stacked on top of each other (i.e, in three dimensions), so I won't be 100% sure of locations till the WTC is complete.














I've ordered all the WTC components, I'll post the build when they arrive, the first hurdle will be to get this sorted. If I can make a watertight tube, I'll worry about other problems as they arise.

The Boattrainman

[Tugfan]

More! More!

[The Boattrainman]

Thanks David for the info on the snorkel assembly, much appreciated

To lead the sail lights wiring to the connection point at the rear of the sub, I've made some 3cm long wire guides from 7mm square Plasticard, each with three 4mm holes drilled so air and water won't get trapped in them.




They are glued to the hull on the opposite side from the sail plane 'snake', and a loop of wire will be left so the sail can be lifted off for maintenance.




The wiring will go to the rear of the sub to unite with the rear light wiring.




The Boattrainman

[He Who Shall Not Be Named]

Your comment as to there being a, ‘MK-2 Snorkel’ provided with the 3.5 SD may originate with an earlier post where I described the ‘horizontal’ type snorkel mechanism I developed for use in the smaller 1/96 SKIPJACK kits I produce. As that sized sail is too narrow to provide for a proper float I was compelled to go with this arrangement – that took advantage of the wider base of the sail. However, this mechanism is not to be confused with the ‘vertical’ snorkel mechanism employed (and provide with the 3.5 SD) by the 1/72 SKIPJACK.






Just a little refresher on how the SemiASpirated ballast sub-system works. Air to blow the ballast tank is either scavenged out of the SD’s air-spaces or from atmosphere from the open snorkel head-valve. The examples here show the safety float-valve with the external plumbing, the 3.5’s unit is housed within the after dry space and has no external plumbing.





Typical of the ‘vertical’ type snorkel mechanism provided with the 3.5 SD. It fits comfortably within the 1/72 SKIPJACK sail.



Break-down of a typical ‘vertical’ type snorkel mechanism – there are slight differences for different scales and types of r/c submarine sails these things have to fit into.

[The Boattrainman]

The new sail sides are united and primed.




The sail top is not glued on yet, I want to see the snorkel operating correctly when installed, I understand there is a Mark 2 Snorkel with the 3.5''Subdriver.




There is still plenty of minor filling and sanding to do.




On to the wiring route inside the hull.

The Boattrainman

[The Boattrainman]

The new sail means I can re-visit the wiring, so I've gone for something different to last time, just one + and one - existing the sail.




The side lights get a plastic surround again.




They are filled with epoxy to completely enclose the wiring and resistors.




A bit neater than six wires to deal with, I'll close the sail later but work out a wiring route in the main hull next.

[The Boattrainman]

The throw extender is shortened and a servo arm connector is attached to further move the attachment point away from centre. A number of L-shaped pieces of Plasticard are cut to 10mm width and a hole to take the 'snake' pushrod drilled in each.





The 'snake' is fed through the holes and the inner sleeve inserted in the pushrod connector, I've cut away sections of the inner hull bracing to allow the snake pass plus moved it further toport to connect with the lever mechanism I made to attach to this pushrod and the sail plane servo pushrod exiting the Subdriver.




The Boattrainman

[The Boattrainman]

Here is the second attempt at the Caswell sail plane linkage/yoke, a process I should have undertaken the first time.

Squares and a ruler are used to measure the distance between the axle centres which is 24mm for a tight fit of the teeth in the units. The distance is drawn on to two 12mm wide pieces of 0.5mm Plasticard.





Once drilled for both the sail plane arms and the yoke axle the parts have two square pieces of 2mm card glued to the bottom of the new fitting where the yoke axle will fit. It is opened out to the axle diameter and then a trial fit of the parts is undertaken





This little mechanism sets the distance between yoke and sailplane cog, no matter how you set them they will always be at the correct distance and perfectly interlocked.





The new parts are stuck to each side of the new sail planes I acquired from another kit, the straight lines help to keep it all in line. The sail plane hole is made to align with the top hole of the new fitting, if you have the Caswell resin bushes they can be pushed into the hole from the outside, mine are gone on version one, but it doesn't matter the Plasticard is strong enough to act as an axle bearer.

The Boattrainman