Vosper 73' 20th scale hull

I am working on a 20th scale model of the British Vosper 73' version II boat, this is based on drawings of MTB 523 obtained for me by one of my cousins who worked there.

The Vospers were built in the Vospers Yard in my home town of Portsmouth England.

MTB523 was a late war production and I don't believe it saw any action. The type II was fitted with an Oerlikon 20mm on the stern, a British 6 pounder canon on the bow, a couple of twin .303 Vickers machine guns, one to port and one to stbd and two 18" torpedo tubes mounted further towards the stern than the type 1 boats. These later boats were powered by three late model USA built V12 Packard engines which developed around 1,500 HP at 2500 RPM.

The Vosper boats (type 1 and type II) hull had a relatively flat bottom with a hollow or slight tunnel on both sides and the keel was a fairly large radius rather than the sharp keel of the US P.T. boats, a flat vertical almost rectangular transom and much less superstructure than the Elco and like the Higgins boats with no day cabin for the crew. So for the kit I have made provision for large hatches at the deck level, this is not strictly scale but we need to be able to get access to the motors, batteries and stearing gear, I have made all the Ribs with fixed tops so you can customise it any way you like and make it truly scale if you want to.

The engines were the same as the Elco and the Higgins boats - Packard V12 M2500's, the two wing engines faced aft and were direct driving the propeller shafts and the centre engine faced forward and drove into a Vee drive gearbox and then back down under the engine. The engine exhausts were piped out to both sides through internal "Dumbflow" mufflers, two on the port side and one on the stbd side, the boat had three rudders.

I am not sure about the propellers used on these boats, this will require more investigation.

In the 20th scale Hull I have allowed for three electric motors of up to 42mm diameter, this is larger than the 35mm motors in the Elco 20th scale.

These three pictures (above) are exported from Autodesk Fusion and the 3D model that I have been working on for around a year (June 2024).

I will export the rib files and make them into a laser cut hull kit, many of the individual parts are already on my Shapeways shop https://www.shapeways.com/shops/pt-boat (July 2024 update - Shapeways has filed for bankruptcy, not sure what will happen there!)

In the process of making a 3D model there is no tolerance in the lofting process, any lumps in the rib drawings causes a coresponding lump in the final surface so it has to be near perfect, so I have then reverse exported the cleaned up rib profiles back into Autocad and I am working on laser cutter files.

This is the reverse exported Rib profiles for all original ribs, these profiles allow for a 1.6mm even coverage of the hull skin. Should make a great hull!

The laser cut hull.

(August 2024)

The full frame kit (the stand not shown).

With deck edge and chine stringers added.

All stringers added.

I am very pleased with this hull, it has great lines!

Above is the suggested build board for the 20th scale hull.

Why is it so hard to make a video work on an updated browser - mpg doesn't work, mp4 doesn't work, mov doesn't work, all with different excuses but! I'll work it out one of these days! In the words of Kramer "Why not just tell me the movie you want to watch"!