The Ship Model Forum

Thanks!

I need to get a consensus on what that device is called as screw boss trailing edge vortex dissipator (SBTEVD) doesn't exactly roll off the tongue...

I will note the Trafalgar screw has that device removed...is it because it was deemed sensitive? I guess beggars can't be choosers and we're lucky to be able to see the Trafalgar screw as it is...

Now, anyone have a line on the Swiftsure's?

I'd call it diverging hub (or boss) cap; if you add one of these nice pointy hubcaps then you are actually concentrating the hub vortex. The stronger the vortex, the earlier if will start cavitating and create noise. Also, with a low pressure in the vortex core you add 'suction' to the prop and you loose thrust. One of the reasons that all propellers have a blunt hub and some are slightly diverging. But I have to admit I have not seen such a cap that is as large as this one!

More in the commercial corner you can also add propeller boss cap fins:





When you have high rotational losses this may alleviate your hub vortex problems and add a few percent efficiency (of course this example has a slightly converging hub for effect, but we did test/analyze boss cap fins that did nothing; one of them because the cap fell off the propeller...). For more modern subs with pumpjets you can add pre- and post swirl stators to manage your flow rotation problems, but these are still very rare for commercial applications. For navy applications they are for subs so not a lot to find online on that particular subject.

Agreed with EJFoeth on the terminology. I've also heard that particular style called a "reverse taper boss" (or "reverse taper dunce"). The seven-bladed propellers for the Skipjack and Sturgeon classes had this style of vortex diffuser, but far less dramatic in appearance than the Resolution.

Also, the official Navy terminology for the 11-bladed boss caps on some Los Angeles propellers is Hub Vortex Diffuser (HDV).

Jacob

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Under Construction:
1/350 Typhoon
1/350 Skate
1/350 USS Nautilus
1/350 Tang
1/350 November
1/350 Hotel II
1/350 Alfa
1/350 George Washington
1/72 Type VIIC

First mock up with the newly drawn HMS Trafalgar screw. I had to speculate on what happens where the screw boss trailing edge attaches as that item is removed from the screw on display, and so I went conservative and with something similar to what's on the HMS Resolution:

HMS Resolution:

Anyone know what the intended added purpose was for the Swiftsure/Trafalgar's 5th lower centerline torpedo tube was? Never read much about it to be honest, and seems somewhat unique?

Five tubes is better than four, I don't think it's much more complicated than that.

_________________
Under Construction:
1/350 Typhoon
1/350 Skate
1/350 USS Nautilus
1/350 Tang
1/350 November
1/350 Hotel II
1/350 Alfa
1/350 George Washington
1/72 Type VIIC

Indeed it is.

Another question regarding the pump jet on the Swiftsure class, do we have any idea how similar it was to that on the Trafalgar? Do I understand correctly the Swiftsure class' unit was prototyped on the HMS Churchill? A shame we don't have a model of the Churchill as that would be an interesting looking combination.

So which British submarine had the 9-blade scythe screw? I've seen references one might exist in older books...but chalked it up to best guess at the time.

Also, which boat is this? HMD Devonport

A little more digging, clearly a Valiant/Churchill class.

She's the Courageous. I think they're moving her to a new berth soon so she can be a museum ship again.

_________________
Under Construction:
1/350 Typhoon
1/350 Skate
1/350 USS Nautilus
1/350 Tang
1/350 November
1/350 Hotel II
1/350 Alfa
1/350 George Washington
1/72 Type VIIC

Can anybody confirm: the boat moored to the quay next to Courageous, is she Conqueror? I guessed that as she is still having her conning tower/fin.

At the opposite quay in the basin are two very similar boats, but without fins: are these maybe Valiant and Warspite?

The other boats are more difficult to identify, but must be various Swiftsure and Trafalgar class boats.

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"I've heard there's a wicked war a-blazing, and the taste of war I know so very well
Even now I see the foreign flag a-raising, their guns on fire as we sail into hell"
Roger Whittaker +9/13/2023

Hi all,

After a lengthy research and conversion I have the basic form right, now only some final painting and detailing needed. Here's HMS Conqueror (Valiant/Churchill class).
I have contacted MikroMir, I will share the research with them to create a kit of the type. Patience!

_________________
"I've heard there's a wicked war a-blazing, and the taste of war I know so very well
Even now I see the foreign flag a-raising, their guns on fire as we sail into hell"
Roger Whittaker +9/13/2023

That looks awesome. Great job on a historic boat.

Dave

Now that Mikro-Mir has given us the Churchill class (Conqueror) kit, the question begs; how similar was the Valliant class? Looking at over all dimensions, it seems they're spot on regarding the hull overall dims. What about general hull shape? Seems this might be an excuse to get another kit from Mikro-Mir?

Hi Woodstock74,

I did that reasearch already: the Valiants were totally the same as the Churchills, only things like soundproofing internally were improved on the latter. For us modelers there is no difference I can tell. So you can safely order the MikroMir Conqueror kit to model either the Valiant or the Warspite.

Only over the lifetime of these five boats there were some differences: originally they had no towed array (on the left aft stabilizer), the hydrophones on the foredeck were originally the small 'dimple' type and later to be replaced by the later familiar and more obvious 'pillar'. And finally, they all originally were fitted with a seven blade propeller but at some time in their life replaced by a nine-blader. But you know everything about those already!

It seems that Churchill has been used as a testbed for the pump-jet propulsor, later to become standard on the Swifture and Trafalgar classes. But I have not found any document lest picture confirming this. Obvious, as the ships are still under official cloaks of secrecy!

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"I've heard there's a wicked war a-blazing, and the taste of war I know so very well
Even now I see the foreign flag a-raising, their guns on fire as we sail into hell"
Roger Whittaker +9/13/2023

Yes, a picture of the Churchill with the pumpjet would be grand, but I think it would be easier to obtain a picture of a unicorn...

I have a picture of a 7-blade "speed" prop on what is claimed to be the Valiant to augment the two "scythe" props (the 7 and 9 bladers). Though good to know it's safe to order a second Conqueror kit; I'm very happy to give my money to Ukraine these days.

I'll post that other prop image up after work.

I stand corrected, not Valliant, Courageous: