The Mk.18 torpedo tube, which launched the Mk.8 21” torpedo, was used on Elco PT boats beginning with the 77 footer and part way into the production of the 80 foot PT-103 class in its original form that I call “Mod.0”. Mods 1 through 5 followed, but you need a “Mod.0” on your 77 footer or PT-109 80 footer. And it does differ in some visible ways from Mod.1, but it’s not a well documented design.
I’ve been frustrated by the incomplete details needed to accurately model this very visible part of the early Elco PTs. A number of modeler’s drawings exist, but they don’t shed light on all the mysteries of this complicated assembly.
So I’ve assembled all the available Electric Boat drawings and the handful of historic photos that show any detail of the tubes, and built a complete CAD model of the tube in 1:1 scale. This project allowed me to fill in many of the blanks, interpolating between the existing “knowns” to flesh out possible solutions for the unknowns.
The 3D CAD model, my 2D drawings, and historic reference material is now all posted at GrabCAD:
https://grabcad.com/patrick.matthews-1/
(you may need to click on “View All”)
GrabCAD is a trusted file sharing site run by the 3D printing technology giant Stratasys. Downloads are FREE but you do need to sign in there. Note that my model is NOT directly usable for 3D printing! But a CAD designer can work up printable parts from this information.
Once there, PLEASE read the “NOTES” document which provides much more additional detail on the torpedo tube and the available files.
CREDIT: All the source information comes from the PT boat community, in Groups like this, at the PT Boat Forum, and from books by more PT boat fans. Thanks to all who keep contributing to the knowledge base!
~~~ MMM ~~~
Matthews Model Marine 