My first Sub obtained today. Is going to be a bit of a slow burn....

[salmon]

I think you are on the right path with keep it simple. I was told on my first build to "Crawl, Walk, Run". Too often, I see a newcomer wanting to add all the whistles like working scopes, torpedoes, moving radar, etc. With the ending of getting frustrated and never completing their sub.
Asking for a device to autonomously surface your sub, yes, that is easy. In my case, I call it an emergency blow. HaHaHa You are located where? That might help with suggestions, but many of our components have failsafe settings.

[MrJoshua]

Sorry yeah, I should of course have said where I am! Am in the UK, but more specifically the Isle of Man. Right now it's pretty crazy as we're right in the middle of the TT bike racing festival so the population of our little rock in the sea has drastically increased with many thousands of bikers, and a fantastic atmosphere.

The heavy glass work on this boat looks to me to be a Darnell kit.

If the Darnell dealer will not sell you parts, I will sell you parts from the Precision Pattern kit. The Darnell kit is a tad off here & there, but with very little effort you can make these parts fit just fine.

Thanks Matt - really appreciate that, cheers!

I forget offhand the name of the place but now I think on it, I recall that when I sent the message via their website, there was no message on screen that confirmed the message had gone through etc like I'd expect with most websites.
It seemed to be a UK site from the pricing, which is useful, but I haven't exactly found many UK places offering much in the way of sub hardware, other than ready made WTCs. Not sure if there are any particular places on this side of the pond which sell a big variety of sub parts?

I'm looking forward to making my own one, but still not fully decided on the method I want to use for submerge/surfacing. I ordered a cheap blood pressure monitor air pump, but it occurred to me that it might actually work reasonably well to use the air bag from a blood pressure monitor also.

I also need to look into what sort of drive setup to use for the two propshafts, i.e. if they should be geared or whatnot, and if they should be driven by one motor or individual control of two motors to help rudder effect etc....

[bob the builder]

In my experience, individual control of the motors, particularly in a boat like the XXI, is useless. The shafts are too close together, and in the case of the XXI, are also angled outward from center. Don't bother with that complexity. It won't help at all. The only boats that individual control really helps is with subs with dual shafts that are greatly offset from one another such as the Oscar and Typhoon (and even then, the effect is very slow).

[subdude]

Bob has it right. Individual control of dual shafts is all but useless. Tried it many years ago on my 1/48 fleet boat. Did absolutely nothing. I am going to run dual speed controllers on my Typhoon, but more for the fun of it (and to use my dual throttle radio) than anything else.

Jim

[Rick Teskey]

Kevin McLeod uses his throttle jockey with great success in moving his Oscar class he can make it piroett within its length
His devices is tied in with the rudder, don't be afraid too try it

[crueby]

Kevin McLeod uses his throttle jockey with great success in moving his Oscar class he can make it piroett within its length
His devices is tied in with the rudder, don't be afraid too try it

I think a lot depends on how close together the props are, and the length of the boat - the farther apart the prop shafts are the better action you will get, also better on a shorter boat. Extreme case is on one of my tugboats (yes, that target thing), can steer and spin just with the two throttles.

[bob the builder]

That's what I had said. Oscar and Typhoon are good candidates for the Throttle Jockey (offered at www.nautilusdrydocks.com). Fleet boats have the shafts too close together to make any difference. It would be better to allocate your attention to a bow thruster in those boats if you need stationary turning abilities.

The other thing about the throttle jockey (again, for the boats with spaced shafts) is the turn-assist they offer. In tight turns under throttle, it adjusts output to one shaft or the other to assist in the turn. A great idea in nuke boats with poor rudder response due to size (which may help alleviate the need to use oversized rudders or rudder extensions.)

[bob_eissler]

My Russian boats don't have enough rudder to steer well. Separate throttles did little on the Robbie Type VII & XXI. Is it worth an extra $100 to you to add it? You have to be running very slow for a bow thruster to work. I recommend a clear rudder extension, very had to see in the water.

[thor]

The Type XXI runs pretty well submerged. Turning radius is acceptable. Running on the surface is an entirely different issue. I kept the scale rudder on mine and didn't add an extension, but I did move the pivot point further forward significantly. That helped quite a bit.

[Ralph --- SSBN 598]

I was not happy with my Engel's Akula II turning radius.
Thought about it and then modified the lower rudder by extending the front edge...twice.

First time I made the shape of the rudder different on the right compared to the left.
After running the boat, I learned that the boat turned better one way than the other.

Second modification was to make both sides of the rudder match the good side and I added a little bit more to the rudder.
In total, I added 1/4" to 3/8" to the lower rudder.

The upper rudder is still stock and most do not noticed I lengthened the lower rudder.

This reduce the turning radius by about 5 feet.
----------------
The original rudders has the pivot point almost at the leading edge.

This is the first modification.
The upper is still original size.
You can compare the upper to the lower here.


The second filled in the gap to the skag and both sides where shaped the same.

[MrJoshua]

Hi guys,

Sincere apologies for this thread abruptly going quiet erm..... some time ago.... but this was just after I'd started a new job which has been somewhat demanding of my time and focus so the Type XXi was shelved for the time being but have now picked it up again with a renewed enthusiasm and begun to start doing some basic prep with a view to finally getting things moving. To be fair, I think one of my first comments was that this would be a slow burn project

Anyway, first things first, it's definitely a Darnell. I actually spoke to the guy who built it originally or at least perhaps previously owned it in the UK before it somehow found its way over to where I am.

I have gutted out the hull now and chipped out a ton of chunks of bodyfiller, resin, rubbery glue type stuff, then smoothed several edges etc with the dremel.
I could not tell what was inside the conning tower when looking from beneath as it looked like there were various bits in there but you couldn't see much beneath as the gap for access was not that wide and did not extend to the rear of the sail, so I dremeled out the opening much wider to access those bits. It was basically the remains of a few wires that I think must terminate in painted over LEDs in the tower, and a bit of alloy plate and tube that probably used to be periscope type bits but had been cut down short.
So that's all been removed now also.

I've given a quick spray over of matt black paint on the inside of the hull to even out the appearance. I think I'd prefer grey or even white for a clean look, but then it occurred to me with all the flood holes in the side of the hull etc, it might look a bit off to be able to see lots of bright bits through those, and that matt black would help keep the innards of the sub from being too visible etc.

Now I've begun pondering what design of WTC and ballast again I should do. I've got a small but surprisingly potent air pump (meant for blood pressure monitors) and it seems capable of quickly moving quite a lot of air. Also have a couple of tiny little solenoid valves but they might be a bit on the small side to be useful.
I've ordered 500mm worth of 100mm OD acrylic tube (couldn't seem to get the same in polycarb for anything approaching sensible money or it would have been my first choice due to being vastly more resilient.

Might have 'accidentally' ordered a new 3D printer (a Prusa) that's infinitely better than the one I have now, so that will definitely assist in this endeavour, although I won't have that for a while yet.

I've just removed the one actual propshaft that remains from the 2 propshaft tubes, and its surface is in a pretty horrible state, meaning the inside of the tube is not really going to be very nice either.
I need to get 2 new tubes complete I suppose so I have the new shafts even if I didn't need the outer tubes, but it'd be nice to replace them if I have to buy new ones anyway.
But.... not sure how I will get the original tubes out as I am guessing they are bonded in pretty solid and will not want to give way. I'll try some cautious hits tot he end of one and see if I can make it slide in its place, but my guess is it won't want to and I'll be risking damaging the hull to actually get them out. Is it possible to get propshafts that run in watertight bearings/seals now instead of standard brass tubes with grease tubes attached? It'd be nice to be as maintenance free as I can be with it if so.

I have one brass prop for it on the shaft that i have, and it seems to be 39mm diameter as far as I can measure, do will get looking for a matching one or a new pair that might be right.

No idea if this should be a single motor or twin, or if it/they must be geared down but I'm pretty sure direct drive to the prop I've got, and the amount of pitch it has will mean it's way too fast, so I think I may use belt and pullies perhaps to gear it down and try to have it running nice and quietly. Think I already may have suitable stuff for that.

Lots and lots to think about and plan anyway.

[MrJoshua]

Here's how it looked inside the hull after I removed all the remaining parts. Not so pretty.



Missing section of hull where bow planes should go. Would this normally be a detachable piece, or has someone butchered it, cutting a section of hull out, perhaps for ease of access?


Another bit that's been cut out, just on the port side of the bow. I'm going to hazard a guess that perhaps there was a plan to make this an opening for a torpedo tube? We'll never know, and another piece I'll need to fabricate for it.


I've now detached the conning tower as it's pretty bad in several respects, and it will be easier to work on like this. Thankfully it came away from the hull with relative ease with no collateral damage.


Conning tower from above. I think the worst bit here is the shape on one side is not symettrical with the other (just below the forward turret where it curves). You can see the curve is very different on either side so I'm going to assume at some point it's been damaged and filler added. I think what I will have to try doing is carefully sanding on both sides until I reach gelcoat on one side or the other, revealing the original surface, then try to get the other side to match better than it currently is.


One of the turrets:


Same from another angle:


So as you can see, all in all there is a lot to do aside from the WTC aspect of things!