USS Thresher

[greenman407]

Nice! I like the splined U joint. Where did you get it? Ill probably be needing some of those for the Seaview. There is a lot of original thinking going on, on this build.
If your asking me about the length of your ballast tank.....well.....your asking the wrong guy. I would say make it too long. You can always go back and put a round piece of blue styrofoam in it to reduce its volume.

[Albion]

WTC Mk 4!!!

With the M1 nearing completion, im switching over to the Thresher rebuild. Sorted through some of the second hand WTC parts and worked out how it will all fit together. I cut out some new saddles this weekend and ripped out the old ones. The cylinder will sit very low and for once all will be below the Waterline. In Mk3 configuration she weighed 2.85Kg (6.3lbs) and didn't achieve true waterline, so plan is for waterline and saving weight. Going to be a simple snort arrangement with no gas back up.


So per previous post how long does my tank need to be, or are you going to make me work it out myself?

[Albion]

Whilst the RCABS works, there isnt much radial space between the 3" WTC tube and the hull, so im not really getting a good surfaced water line (i know, you told us so).

So im going to be retrofitting a 2.5" snort only wtc in here ;)

Thanks to the garage sale i have the basic bits and pieces needed along with a long tube which can be cut to fit. Couple of questions
1) without any gas tank in the ballast tank, how long should i make the tank?
2) Looks like there should be a lip seal on the drive shaft. Could you let me know what it should be so i can get back in Singapore
(currently enjoying , hah, the -20C weather in western PA)

[Albion]

Well finishing touch's on this one, i needed to make it a boat more user friendly. The front end cap for WTC also had the hole for the wtc locator pin, so it meant this had to be lined up with rear end cap, also it mean't hassle for removing end cap whilst wtc was in hull. (ie major strip down to get to the batteries. I also needed an on / off switch.

I had realised that the motor i was using was too high reving (Engel 540/6), a test using the new prop showed 7.5 amps at max speed, and was audibly straining. My Koryu which is swinging a bigger prop, albeit only a conventional 3 blade (this is 7 blade cleaver), only pulls 1.5A, with its slower running motor, so i got hold of another one of this type (Engel 540/12), which needed a big strip down, but the result was only 2amps at full speed, and things still feel a bit tight so this should come down.

Looked at the new rubber booted toggle switches on this site, but end cap was too thick, so would need to recess the end cap, plus there isnt much radial room.

So i came up with a push on push off mechanism (blue switch), which uses the same seals as my push rods.

Also i cut a pin locator in rear end cap, and a pin mounted in the hull. With this type of coupling it isnt so easy to drop the wtc in and locate onto a pin. So the pin hole is actually a channel, and then i have a clip at front of wtc to stop the wtc moving forwards. Was suprised how simple and effective this turned out to be. Also the more observant may notice the RCABS system has changed slighlty, i'm now using a subtech SES switch to turn on the pump, and open a valve, instead of servo. The previous failsafe is needed for a new project, and the SES is now redundant from another boat as i will be using a completely different ballast system, watch this space for future projects!

[Albion]

Latest condition.

Need some natural sunlight shots, the flash makes everything look, well more weathered than it is.

Prop shop prop :wink:

[Albion]

no problem and thank you. the Toothpasting trick has worked in a few places, and next time i can get that better, so not 100% but not bad , im pleased for now. just need to dirty up the topside as its looking a little stark

[He Who Shall Not Be Named]

Albion,

Much, much better effort this time. I think you'll agree with me that taking the time and working in the new techniques you've learned has turned your model into a much, much better looking display that what you would have had had you gone with the original paint-job. Well done, sir.

Don't forget the bird-**** streaking down from atop the upper rudder!

And you'll soon have a 1/72 M-1 to further practice your painting skills on. Thank you for being patient with me.

David,

[Albion]

Below Waterline, yet again the flash is making the white appear much more prominent that it really is

[Albion]

Line in the sand time. Here she is pre weathering, pre lacquer coat.

The front vent in the sail looks minggy, i hate digital close ups, they show up everything

[Albion]

The real reason for this thread this as a home made WTC right, not all this namby pamby painting stuff

First a history lesson
I was rebuilding the WTC on my Permit into the Mk3, and at the same time cleaning up the hull to make it more presentable, rather than looking like a scruffy toy, which has clearly had a lot of experimentation.

The existing WTC is what I call the Mk2B, it started life as Mk1 using a 3.5” tube with the motor and servos located in the rear, and a forward section housing the electronics, batteries and a small piston tank. The two areas are separated by a simple centre cap, through which the wires that pass are sealed with silicon, so the aft section (where the rotary seals are located), is not pressurized when ballast tank is filled. Mk2 used my own machined centre cap containing a monocoque piston tank, but had too much material and was far too negative especially at the stern. Mk2B removed some “meat” to increase buoyancy but still is not too good.

Problems with Mk2b
1) Still too heavy
2) The material used did not machine well enough to create a smooth bore for the piston tank, leading to excess friction causing reduced battery life, and also some leakage past the o ring and into the wtc
3) The 3.5” tubing is really too big for the hull, meaning lack of radial space and the WTC is above water level in surfaced state, so extra tank volume required to offset this.
4) Piston tank volume not large enough for a scale waterline (see also 3) above).
5) The Front end cap was never truly fixed to the tubing, it was held on with Tank Tape meaning sailing was limited to pool use in case the internal pressure popped the end off, which it often did after a while.
6) The Tube was secured to centre cap via radial screws, which caused stress cracks on the tubing.

Solution
A) Going back to a tube for the piston tank cylinder.
B) Increasing the length of the tank.
C) Using 3” diameter tube for WTC.
D) Using tie bolts to hold pressurized part together.

My Xmas Project - machining new custom centre cap. This was finished and all manner of holes drilled and tapped, I now had it ‘equal’ in scope to the previous centre piece. Ok one is 3.5” dia and the other 3” but was shocked by the weight difference as I thought the metal in the studs would offset the lack of ‘plastic’ material, damm Delrin must be dense.
Original = 397g
Revised = 200g
Half the weight! And that is after my removing material, the Mk2 must have been a brick. The smaller WTC tube will mean less buoyancy but it was all going in the right direction. Then I hit a wall I hadn’t planned for, the drive motor for the piston doesn’t fitL. The pulley wheel on the piston shaft is 40mm od and the motor pulley is 9mm. The WTC is 70mm ID. So working from CL I have 35mm height. Large Pulley =20mm, small pulley 4.5mm, that leaves 10.5mm or 21mm diameter drive motor, it currently is 28mm. I was too busy focusing on the piston and wire routing I forgot about this.

So refocused and worked on the motor mount for end cap, I really like the Engel fittings which I used on the Koryu, so I am using the Engel motor mount which incorporates a seal and bearing. A cut off from an old shaft provides the stub shaft. Using the same servo mounting method as on the Koryu, also the same bellows assemblies for sealing. Only less than perfect part is the through bolts on the end cap which despite having capped nuts will still probably require some sealing.


Kept looking back at how to fit a drive motor for the piston, when Nuke power (yes He is to blame) posted a how to make a RCABS WTC on another forum (clearly in present company this post should be spat upon and finally tarred and feathered). I had already got one end cap made up with Servo’s and motor, and realized that the components I needed were all in my box. So one Saturday morning I started out with a rough drawing of how to lay out my internals and got to work, by the end of the day, covered in lexan dust and other assorted toxins I finished up with a working item. Inside I have

Receiver
3 x standard size servo, two to operate rear planes and one to operate ballast
Engel motor mount, motor, ball race and seals
Engel bellows seals and ferrules
Schrader valve stripped down and soldered to a bracket.
Motronics ESC
Air pump
Subtech leveler
Subtech failsafe
7.2V car type battery pack

I fitted the Switching servo so that it acts as a stop for the battery pack, ie the battery just fits between the front end cap and the servo, so it doesn’t slide about. With this location fixed I then played around with the various bits to get optimum layout, ie hoses not kinking, power wires away from signal, noise generating parts away from receiver, well I did the best I could anyway.

I cut some lexan sheet so that it closely filled the 3” cylinder at its widest point thus supporting the tray full length without additional fittings. Everything can be installed from the drive end. X on the end cap marks the spot where I want to install a Caswell waterproof switch to complete this.

The ballast system is connected to a 12” long bladder which sits on top of the WTC between WTC and hull, it’s a tight fit, but provides just enough space to inflate the bag and achieve scale waterline.

If I did this again I would use a 2.5” cylinder in this hull, maybe a bit longer to allow more volume for filling the bag. The smaller diameter would allow more room for bag to inflate and give even more waterline. Also I would buy (yes I would, but they weren’t available at the time) the D&E end caps, as this would avoid the messing around I had with making my own servo supports, and would make for an even easier “build it yourself” WTC. Additionally I would probably go for a solenoid valve and the caswell pumps with built in switch board, this would clean up the internals no end, and combined with KMC leveler / fail safe, it would give a very clean look to it, and maybe avoid a longer cylinder. But as I said, I did this with what I had lying around.

The drive shaft mount is in the standard location for this hull, which is most suited to a D&E 3” wtc (old design), and so if it was sold on or later converted it maintains its resale J. The shaft coupling allows easy transition from Metric Engel shaft, to imperial drive shaft, but is suited only to angular misalignment, so it took some careful work to ensure WTC mounted correctly

As I mentioned earlier this has been a bit of a mule boat, and took a bit of bashing around in the pool. The original propeller was white metal and firstly got bent a few times, and finally stripped its grub screw. Its replaced with a brass Raboesch 7 blade prop which is a bit too good!!!, and also suffers from having a large hub. I found that Rabo now make a small hub 7 blade scythe (R186-10), but need to get Mike excited enough to stock them as I cant find a distributor, go on, you know you want to.

Well that’s the mechanics sorted aside from a switch, I just need to finish the paint job now, and then I can start something new J

[He Who Shall Not Be Named]

Albion,

Good, good. You jumped back on the horse after that recent nasty fall. OK, you now have a good canvas upon which to paint (weather). Yes, give the model two rather heavy coats of clear -- this will give you the ability to sand off any bad weathering applications without cutting into the base colors, do such sanding with 2400 or 600 grit sandpaper. Look on that ability as you would a pencil eraser abrading away an error you wrote onto a piece of paper, the ability to scrub off markings/bad weathering without harming the substrate.

Have your test article standing by and perform all proposed operations on it (in small patches) first -- once you have the right mediums and applications techniques down solid on the test article, immediately move onto the THRESHER and lay down the mung.

Those photos sucked! Put in more hours at work so you can afford a camera that can get into focus!

David,

[Albion]

Well just so you dont think ive given up, here is latest status, been working too much.
plus there was an intermeadiate paint scheme, where i tried to paint the grey below water line a slightly lighter grey, however it came out too grey, and really my grey to was too light as well, so it all got cleaned off again.

So now got nice differential between the hull and anti slip area, still need anti slip on sail fins. Need to add the white draft markings, then venture into weathering again. Should i laquer it before weathering?

[RonP-UK]

God, I wish I could do this sort of stuff----------My paint jobs are always too clean, they look like the boat has just left the paint shop and on the odd occasion that I have tried to put some life into the model it looks as though its just been dragged out of a cow shed. Give me a chunk of brass and I can do something with it, plastic or resin the same but a paint brush
---------------well we just don't mix well.
RonP

[He Who Shall Not Be Named]

LOL. You've taken your smack-down in good humor, and your willing to fix things. Good man! You're trainable.

Let's rescue this boat:

Water-soluble paints are only water soluble as long as the binding resin has not polymerized -- which does not happen dill the solvent (water) has left the molecule. Once the water has evaporated out, the cross-linking of the resin changes its state to a solid, now only soluble in harsh solvents that will also attack the underlying paint, primer, fillers and adhesives.

You're pal!

Wet sand the entire model with #600 and re-paint the basic above and below waterline colors. Start again.

Break out an old half-started kit and make that your test article. Get it into the same paint condition as your nice little THRESHER and parallel the weathering tasks between the two: first the test article, where you will refine your technique and choice of mediums; then apply those lesson to the THRESHER. You'll note a vast improvement in the work over your initial attempt, Albion.

I'm here with help anytime, buddy.

David,

[Albion]

I've stood in the corner with my hands on my head, and written a thousand lines, i must not use fire crackers and paint again.

So how to fix the damage.

The grey white streaks are indeed water based, will it come off so i can avoid a respray