A Skipjack in Ireland

[The Boattrainman]

The Piston Tank outlet hose sits neatly around the motor and between the servos.




Bits of square plastic tubing and channel are used to make fixings for the permanent 12V wiring, and holder for a spare fuse is made.




A short additional support rod is used as the lower one is missing to allow the motor to be taken in/out. Around this bar the wiring to the end cap for the lights will be wrapped and down the square plastic rod.




On the servo lead side a series of double holes are drilled to take mini cable ties.





The Boattrainman

[The Boattrainman]

Progress has slowed, not because there is any less work being done, but because I'm painting the tech rack. As I spray slowly and leave 24 hours between coats it's time consuming.



Paint is a basic automotive spray primer, same colour as the plastic, just to cover up blemishes and filler.


The final 12V item is the switch to turn off the lights when diving, it'll be covered by the piston tank switch.




Here is the switch outside the housing, the roller arm is depressed as the piston spindle moves outward. By wiring a standard SPDT Push to Make microswitch with the 'On' side when the arm is not depressed, when it is depressed it switches to the unwired side, making it a Push to Break switch.



The Boattrainman

[The Boattrainman]

The wiring continues, every wire is being custom cut,including the servo leads, to the exact length, I'll post only when it's all done

However, a previous post about water leeching up the external wiring bit me on the ass! During pressure tests with the Piston Tank installed, the only air escaping was out the leads to the lights...................Incredible.

To remedy this,I tried an external compression fitting, using a connector and small brass inserts to squeeze the wires.





It didn't work!!!!!


So I resorted to my usual plastic surround making a small box filled with epoxy, this time inside the WTC.



The four leads are soldered to two wires leaving the box.





This is the finished box, with cables soldered to the bare wires running back to the lights switch.


The Boattrainman

[greenman407]

Nice and Tidy. My wiring is usually a mess(rats nest).

[The Boattrainman]

I'm closing in on the final part of the wiring but I have a question.

To get the Receiver aerial from inside the WTC to the outside (and hopefull up the inside of the sail), there are two options.

1. Drill a small hole in the end cap, lead the aerial out the hole and seal as usual with epoxy. That means the reciever and aerial are mated to that end cap.

2. Drill a small hole in the end cap, push a small length of brass wire (the same diameter as the inner core of the Reciever aerial) through the hole, cut the aerial short in the WTC and attached a single pin connector to inner aerial to push onto the wire ,and solder the outer piece of aerial to the outer piece of wire. As long as inner piece of aerial, PLUS brass wire PLUS longer piece of outer aerial come to the same length as the original whole aerial it should work?????

I know, I know the web is full of posts 'never ever cut, shorten, lengthen a receiver aerial, etc. etc. But if I get this to the mm, it should work. And I get that the aerial length is a mathematical factor of the transmission frequency, but if it all ends up the same length, what's the diff?

Or am I missing something.

The Boatrainman

[trout]

I used to use #2, but I would sometimes get funny reception. Now all my subs have the antenna left inside the tube. No issues. Someone else who periodically runs in brackish water would leave his antenna full length in the cylinder then using option 2 and whatever went outside the sub was just additional. His subs run amazingly well.

[He Who Shall Not Be Named]

I'm closing in on the final part of the wiring but I have a question.

To get the Receiver aerial from inside the WTC to the outside (and hopefull up the inside of the sail), there are two options.

1. Drill a small hole in the end cap, lead the aerial out the hole and seal as usual with epoxy. That means the reciever and aerial are mated to that end cap.

2. Drill a small hole in the end cap, push a small length of brass wire (the same diameter as the inner core of the Reciever aerial) through the hole, cut the aerial short in the WTC and attached a single pin connector to inner aerial to push onto the wire ,and solder the outer piece of aerial to the outer piece of wire. As long as inner piece of aerial, PLUS brass wire PLUS longer piece of outer aerial come to the same length as the original whole aerial it should work?????

I know, I know the web is full of posts 'never ever cut, shorten, lengthen a receiver aerial, etc. etc. But if I get this to the mm, it should work. And I get that the aerial length is a mathematical factor of the transmission frequency, but if it all ends up the same length, what's the diff?

Or am I missing something.

The Boatrainman

Antennas on the bands we use (the exception is that god-awful 2.4gHz) are of the fractional type -- ideal length is too long to burden transmitter or receiver. But antennas at a harmonics of the full wave work just fine, and that's what comes in the box. So, fine if shortened a bit. You'll still get enough signal to the detector part of the circuit to be useful. So, cut away and don't sweat it. Another thing -- we don't come close to exploiting the ideal range on this gear. We bubble-heads typically consider 150-feet away a long way off -- we're not sending a drone a mile down range here! To us the inverse-square-law is our friend.

David

[The Boattrainman]

Thanks guys!

Another expense I hadn't factored was my 2.4Ghz Trans was redundent for this build. I'm sorry now I let my lovely 6-channel 40Mhz Hitec unit go when I sold my U-203, 40Mhz stuff almost impossible to find now.

I eventually found a second-hand Trans in a local model shop, they let me have it for 40 Euro, a bargain I suppose. It's a Futaba T6EXAP and is the last model before they switched to 2.4Ghz and using the same Trans design, looks like it was never used...............120 bucks when first came out but redundent within a few months.

What was wrong with 35mhz, 40mhz and 72mhz (in the USA), I actually enjoyed fecking around with crystalsl!!!!

That said, my FlySky 2.4Ghz was also a bargain, at 50 Euro brand new with matched Receiver and fully programmable..........time marches on............!

Rob

[The Boattrainman]

Some form of heat insulation/shield is needed around the ESC. This small aluminium plate is made to go under and keep the ESC away from plastic parts.




The Boattrainman

[The Boattrainman]

Following on from the advice about the Receiver aerial here is the build. The total length of the aerial is 985mm, so I have to re-create that.

A 1.5mm hole is drilled in the end cap and a small plastic tube is glued to the outside and filled with epoxy, and has a 1.5mm pin pushed into it which is pre-soldered to an 800mm length of the aerial.




The small plastic tube gets an end cap, and the pin inside a small washer to finish it off.




The small piece of aerial still attached to the Receiver, gets a connector made from a 2.5mm brass tube, small piece of heat shrink and a plastic cover from mains cable.




The entire length of the aerial inside PLUS connector PLUS end cap pin PLUS external piece of aerial is still 985mm, and receives signals from the Transmitter just fine.




And that is the last hole to be drilled in the end caps (6 in the aft cap and 3 in the fore cap)!!! Each time you sweat that a new hole will leak and ruin the build, glad that's over.

Just waiting for a main drive battery and some final parts and I can finish the wiring,then the WTC will be operational.


The Boattrainman

[The Boattrainman]

The wiring is now sorted, five weeks including de-bugging and a faulty pitch controller.

It took a lot longer than expected also as both wire ends (on over 100 wire pieces) are tinned with solder, and all soldered connections have a heat shrink sleeve.

Starting at the forward end, the 12V power is taken from the battery box with a Deans plug. The box can hold an 11.2V 5000mah Lipo, or a ten-cell 12V 3000mah Nimh block, will be testing both.




The power is led up to the fuse box and main switch and to a connector block with one connector each for the motor ESC, Piston Tank Switch and navigation lights. The light switch is just visible under the piston tank switch.




Wiring passes the piston tank through a square plastic tube and to the lights along the upper strengthening rod, and into another four connector block (2 for 12v power in, and 2 to the motor under).




The space for the ESC has the heat shield and a connector to the Receiver ready to take the plug. The screws on the top are holding the motor mount under this box.




This is the underside of the above, the motor is upside down and retains it's Tamiya plug so it can be swopped out, twin cable ties keep the wiring off the motor in case it heats.




On the servo lead side, there is a space for the Engel piitch controller beside the dive plane servo (the unit is gone back to Engel as it's 'twitching' the servo, numerous tests with other servos etc. proves the unit is faulty).




The servo leads pass the piston tank in pairs, held in place by heat shrink sleeve and a plastic keeper stuck to the piston tank with double-sided tape.




The servo leads are led by the main switch etc. through two tunnels and a piece of heat shrink, all servo leads custom cut to length.




The Receiver is held in place by three L-shaped pieces of plastic, the push rod to the outer part of the main switch has a bit of Bowden cable as a cover.




There are two universal couplings, one at each end of the stuffing tube, and each has a compressed O-ring and thrust washer.




And it all fits snuggly into the WTC. All 12V on the starboard side and all servo wiring on the port side, with both motors having suppression capacitors that should stop any interference to the Receiver.





The Boattrainman

[reddevil]

Really impressive. Congratulations.

[The Boattrainman]

Thanks Reddevil.

This little fitting will help keep the wiring tidy outside the WTC.




I sourced automotive waterproof connectors (from 12v Planet) to join to both the sail lights and solitary tail light, a bit big for a small model but worth it.




The plugs are held down to the bottom of the hull out of the way of the push rods and prop shaft.






The Boattrainman

[The Boattrainman]

Another update on costs:-

The basic WTC is detailed earlier at 103 Euro.

Going left to right on the large picture above:-

WTC..........................103
Battery.........................25 Hobbyking
Receiver........................8 Ebay, used
Piston Tank Switch.....59 Engel
Piston Tank...............175 Engel
Lights switch..................6 RS Radionics
12V Motor....................33 Ebay
Elec Speed Cont..........30 Cornwall Model Boats
3 X Small Servos..........24 Hobbyking
Pitch Controller............79 Engel
2 X Couplings..............18 Cornwall ModelBoats
2 X Connectors............14 12V Planet
Servo leads..................10 Local Model Shop
4 X Rubber Bellows......16 Cornwall Model Boats

Total.............................599

Wiring of various gauges, brass/steel rods, small connector blocks, plastic tubing, screws, fuse, main switch, heat shrink, glue, solder and sanding materials, I had in stock.

With the cost of two kits (I had to acquire a second as I was unhappy with the sail on the original) at 128 and Caswell Fittings at 150, the grand total looks to be coming in under 900 Euro, with only paint and ballast materials to be sought.

Not bad value for a fully working static(hopefully) diving sub, and a good test bed for future models.

All of the suppliers mentioned were excellent except for one delay from Hobbyking, I have to commend both Cornwall Model Boats and Caswell (now Nautilus Drydocks) for the quality of items and back up service.

On to the WTC shakedown and system test.

The Boattrainman

[The Boattrainman]

There are three parts to trimming the model, surface major trim, surface sub-trim and submerged trim.

7mm X 20mm metal bar is cut to various lengths and laid along the keel. I've seen a lot of boats/subs trimmed with large pieces of lead or metal usually bunched up in one place, this is a mistake as it creates a 'moment' around which the boat will bob. To counter this, the bars are laid along the keel as close to the bottom as possible all along the line of the keel but not fouling the water inlets/gratings.







The bars are moved around to get the sub level, and here it sits in my test facility.





Now the eagle eyed will notice it's trimmed to slightly below the waterline as tests with a 500ml weight (below) slung to the bottom of the hull on the elastic band, simulating the 500ml piston tank volume/weight, demonstrate it needs to be a fraction low in the water to completely submerge.





On the plus side, sub-trim is not required as care with the building of the WTC and positioning of the heavy components plus accurate centreing of the WTC within the hull at the centre of gravity means it sits perfectly upright. Neither is any foam needed for flotation as the WTC provides all the buoyancy needed.

I'll work on the submerged trim when the piston tank is fully tested.

The Boattrainman