today's work

[goshawk823]

Hmmm… well, ****, I hope I didn’t step in it! I’ve just never seen anyone do a plug/master/hull XXI in that small a scale. I/72, 1/48 and 1/32, yeah.
Apologies in advance if I started a **** storm! ::). (Ducking as I type…)

[Das Boot]

wow…very nice looking xxi, david. Is that from a 3d file print?

Incoming!!!!!!

[Das Boot]

Wow…very nice looking XXI, David. Is that from a 3D file print?

Incoming!!!!!!

[redboat219]

GRP? 2-2.5" Subdriver?

[He Who Shall Not Be Named]

Hmmm… well, ****, I hope I didn’t step in it! I’ve just never seen anyone do a plug/master/hull XXI in that small a scale. I/72, 1/48 and 1/32, yeah.
Apologies in advance if I started a **** storm! ::). (Ducking as I type…)

Yeah, it's a 3D print.

WE SHALL NEVER SPEAK OF THIS AGAIN... EVER!

David

[SubDude]

Yeah, it's a 3D print.

WE SHALL NEVER SPEAK OF THIS AGAIN... EVER!

David

I LOVE IT! Queue up "The Stars and Stripes Forever"!!!

[redboat219]

Are you ready for THIS?!!...

A 1/96 Type-21

31 inches long
3.2 inches wide

[He Who Shall Not Be Named]

This coming fall the North Carolina Model Boat Club will again host the annual 'Fleet-Run'. An all 1/96 scale r/c boat (and submarine) group run at City Lake in the city of Rocky Mount. I've attended one of these events and it's a wonderful three days of running at one of the best boating venues on the East coast. Currently I'm just about the only guy who operates r/c submarines over there. However, next year I will be joined by J. Hoffman who will operate a German Type-21 U-boat. This guy is renowned for his very well crafted, scratch-built model warships, and its a pleasant and instructive task to study his work in and out of the water.

I'm a submarine guy. Mr. Hoffman want's to be a submarine guy. So, we agreed to a collaborative effort: he wanted a German Type-21 submarine to add to his 1/96 fleet, and I agreed to help him equip it with the gear needed to make it a fully functional r/c submarine.

And here it is, in foreground, next to my still in-work 1/96 SKIPJACK. Remarkably, they are both just about the same length.



The entire model kit was fabricated in a printer, I don't know at this time if it was a filament or resin type printer. You see that blue tape on the sides? That's to hold the three pieces of hull together for these shots. I assume it was printed this way owing to the machines maximum height build-up ability. Anyway, I will eventually glue the three hull pieces into one, then, at the waterline, I'll split most of the upper hull from the lower hull. This will give us access to the interior for installation of the water tight cylinder (WTC) that will contain the control, ballast, and propulsion sub-systems needed to animate the model.



Though only some 31" long, the hull has room for a 2" diameter WTC with all the gizmos needed to permit control of the propulsion, stern planes, rudder, bow planes, and ballast sub-systems. I've yet to determine how much water the ballast tank has to hold, so I'm deferring assembling the WTC till I have that number in hand, which will drive the length of the WTC's centrally located ballast tank.



Most Allied nations, after the war, conducted evaluation of the surviving 21's. Those submarines, the most advanced production submarine of the war became the grand-daddies of the first post-war designs to join the cold-war. Quit a legacy! There's a little 21 DNA in the SKIPJACK's. Both true underwater fighters.



To make things easy I elected to work out the propulsion shafting and bearings; rudder operating shaft and control horn; and stern plane operating shaft and control horn with the after section of the hull removed from the rest of the hull. In this shot I've already made up the propellers -- I was surprised and delighted at the strength of these and the other thin cross-section printed parts -- to 1/16" diameter brass propeller shafts, and installed them into the stern tubes embedded at the trailing edges of the horizontal stabilizers.





There were no bore holes in the propeller hubs, and that meant some careful work starting and finishing off interference-fit bores for the 1/16" diameter brass rod propeller shafts. The bores started life as a punch-mark, then a shallow plunge with a #80 bit, followed by a reaming with a hand-twisted #53. At that point the bore was only 1/32" deep, a good enough pilot-hole to let me use the big gun with an assurance that the bit would not wander off-center.



On the drill press, with the hub tip residing in a hole drilled into a scrap piece of shelving board laid atop the machines bed. This way the three blades of the propeller rest atop the board and in so doing presented the hubs base at a right-angle to the drill-presses 1/16" bit. Then -- with very light, shallow stabs of the bit into the work -- I deepened the hub bore hole. Sweat-pumps to Fast!



Damn! I didn't break anything. Notify the Media! Wrench-wrist Dave pulls another one out of the hat!



Just some of the tools used to hand-bore the pilot-holes into the propeller hubs. The same tools were used to bore out the propeller shaft stern tube bores -- I was glad to find that even the horizontal stabilizers were hollow, and of very thin section, which made that job a cinch.



A nasty characteristic of the 21's was that differential use of the screws to aid in the turn was backwards from most vessels. This is because the thrust line of these toed-in shafts intersects the crafts longitudinal center a bit aft of the vessels center of mass. But, since this model will have these two propellers spinning at identical RPM, in counter-rotation to one another, that's not an issue for this model. Here I'm sliding a propeller shaft into its stern tube.



Now, to work out the rudder and stern plane linkages. God help me!

David

[redboat219]

Can't wait to see how you'll tackle the linkages specially for the rear dive planes.

Can you use the SD for the 1/72 Type VII or is it too long?

[He Who Shall Not Be Named]

Can't wait to see how you'll tackle the linkages specially for the rear dive planes.

Can you use the SD for the 1/72 Type VII or is it too long?

Two motors is too much power. I'm using one motor with a gear-splitter. As to the rudder and stern plane linkages. I'll try to keep them internal, but may whoose out and run the pushrods and horns external. Those 'blisters' each side of the stern, just over the rudder provided for the rudder operating shaft bell-crank on the real thing. And, on this 3D printed model they are hollow, so I might be able to do it as the prototype did. We'll see. A Watch-makers delight to be sure.

David

[Monahan Steam Models]

Watch-makers challenge for sure! Looking forward to seeing more of this build. Really nice sized model that you can carry in one hand.

Hard to tell from the photos, but it almost looks like it might have been built on a resin printer? Would be interesting to know more about how the hull was made and who’s files were used.

[goshawk823]

looks fantastic David. I've always loved the Type XXI. definitely a challenging build in that scale.

[He Who Shall Not Be Named]

Watch-makers challenge for sure! Looking forward to seeing more of this build. Really nice sized model that you can carry in one hand.

Hard to tell from the photos, but it almost looks like it might have been built on a resin printer? Would be interesting to know more about how the hull was made and who’s files were used.

I think you're right, very, very light striations.

David

[redboat219]

Watch-makers challenge for sure!

Found these photos of an RC conversion being done on a 1/35 Bronco Seehund in a French RC forum.

[He Who Shall Not Be Named]

Found these photos of an RC conversion being done on a 1/35 Bronco Seehund in a French RC forum.

External linkage elements I wish to avoid.

David