Vosper Hydrofoil MTB - 1/72

[Rick Lowe]

Or, you could say that trials highlighted this exact problem, but with the early generation missiles coming along, they modified the boats to carry them - AIUI, MTBs morphed into missile boats in the RW

[jcf]

Another thought is, I wonder if you might have a risk of running into your torpedo before it got up to
speed?


Perhaps the technique would be to slow the boat and drop back down to hull borne, but still planing,
before launching the torpedoes, just long enough to launch and then turn away accelerating back to
being foil borne. Basically come in fast, suddenly slow, then turn and speed away.
 

[buzzbomb]

Another thought is, I wonder if you might have a risk of running into your torpedo before it got up to
speed?
 

Perhaps the technique would be to slow the boat and drop back down to hull borne, but still planing,
before launching the torpedoes, just long enough to launch and then turn away accelerating back to
being foil borne. Basically come in fast, suddenly slow, then turn and speed away.
 

I have decided that in this build universe, the magic of whiffery has decreed that the boffins have come up with a way to extend the distance a torpedo will launch so it is outside foil zone.
Also the torpedoes may have become secondary armament due to the heavier 6 pounder mount due to your valid point about lack of viable targets.

Buildwise, on a bit of a roll.

Moving onto the base. It is a foam base, with some sculptamould base texture. This was allowed to dry then a couple of sheets of blue crepe paper was laid over the entire thing and then wetted down with diluted white glue, which added further "wavy" texture and a more merged surface.


After that had dried, the next step was a quick coat of paint to check it out and then starting to pack in more crepe paper around the hydrofoil business, only with water at this stage, because my logic says, I should be able to still remove it. We shall see if logic wins over reality

[Old Wombat]

 

[Rick Lowe]

 

[zenrat]

Seeing as most of the torpedo is not visible due to the tube you can posit that they have rocket assisted launch packs mounted to the rear of the fish.
Or just claim they are similar to Soviet Shkval - rocket propelled supercavitating torps.  With solid fuel rocket propulsion they'd be pretty quick out of the tubes.
https://www.naval-technology.com/features/featurethe-allure-of-supercavitating-torpedoes-5838643/

[NARSES2]

That's looking good 

[jcf]

Looking good. 

According to Allied Coastal Forces of WWII: Vol.II Vosper MTBs & US Elcos* by Lambert and Ross
the aft torpedo tubes on the 73' Vosper MTB Type II were mounted at an angle of 15.5º from the
boat's centreline.

The UK 21", 18" and US 21" Elco-type tubes all used an exploding charge to create the gases used
to propel the torpedo from the tube. The 78' Higgins boats used a compressed air system.

The ideal launch speed for the UK torpedoes was evidently 12 knots - otherwise they would either
dive too deep or porpoise, the US was 20 knots, at least for the tube launched 21" Mk. 8. I haven't
been able to locate a number for the 22.5" Mk. 13 aircraft type used with the simple "roll-off" racks,
I'd guess it's probably higher seeing as it was a torpedo designed for airdrop. The UK didn't adopt
the roll-off technique during the war but did so post-war.

So in reference to your boat, the 15.5º angle is probably still good and the whiffery could be a
larger propulsion charge and an improved torpedo with a higher speed and better depth setting
controls enabling a higher launch speed.


*A very good book, the only major niggle being that in the section on the Packard 4M-2500 engine
Lambert repeats Scott-Paine's bogus claims of having been responsible for the engine design.

[buzzbomb]

Well that's about it. Call it done for what it is.
I got to thinking about pulling off both torpedo tubes and creating a Destroyer type rotating mount, like this (thanks for the pic shapeways).. but only a triple mount, trash the Oerlikon mount


Luckily, I then decided. Nup, for the intended purposes, it will do. Not quite sure about the dumbflow exhaust outlet attempt. With them on

With this beam side off. Leaning toward off as getting this water/exhaust mix to look any good appears to be rather a challenge


Couple more beauty shots



thanks for dropping by and the excellent discussion on this topic.

[zenrat]

Looks great BB.

[AndrewF]

That looks fantastic! Nice one.

Regarding the exhausts, I think it looks like it's going faster without the exhaust flows - you could angle the flows more to the rear to give an impression of speed. But the side without the exhausts looks like it's powering along at a greater rate of knots.

[Old Wombat]

Awesome work, BT!


I'd lose the side fountains, they just look wrong. The (limited) MTB footage I looked at showed a relatively small amount of water being sprayed out at high velocity, even with the boat idling.

Plus, with the hydrofoil, where do you get that much water to pump out?

[NARSES2]

That's a terrific build sir 

As an aside what scale are those Shapeways torpedo tubes ? Whatever scale they must cost a fortune ?

[Rheged]

This, I like very much!!


I'm sure I've seen a series of pictures in a 1950's  publication of a group of these boats becoming foil-borne as they pass the Portland Harbour breakwater.

[jcf]

Very nice. 

Wet exhausts don't produce streams of water, when you see a stream coming out of the side
of a boat it's usually from a bilge pump.