Hi Rainer

The design studies, of which this report is a part, have been made under the authority of the Chief of Naval Operations resatricted letter Op-23C-1-Serial 217423 of 28 May 1945. This letter directs the Naval Shipyard Portsmouth, to prepare design studies, perform tests and to compile reports on each type of submarine.

This report has been prepared to describe the material compeonents of a single type of vessel. In addition to the purely descriptive matter, to report includes comparison with related U.S. Naval or commerical practices in place where it is believed such comparison is of value in determining the basis of design.

Where comparisons are made, they are intended to assist in evaluating the particular circumstances, and are not made for the purpose of questioning the existing practice. To the extent that any single item has merit, it has been so described, but it is fully recognized that the good points of a single component do not necessarily indicate that an entire system or method is superior.

This report has been prepared in accordance with the division of subject matters given in the Ship's Material Section of the Navy Filing Manual. All of the "S" groups are represented by text material or by cover pages which either refers to other report sections for related text or indicate the inapplicability of the section.

In view of the applicability of the Navy Filing Manual as an index for the report no separate index has been prepared.

Each "S" group in the report on 9C40 vessels is complete within itself and consists of a title page and summary, a description of the appropriate design elements and relatede remarks and conclusions. The corresponding section in the reports on other types of vessels is not, generally speaking, complete in itself, but describes the changes from the 9C40 vessels which were made when designing the corresponding elements in that one type. This procedure has saved a great amount of duplication, for all the later types were related in varying degrees to the 9C40 and in a number of respects are identical.

In certain cases, it has been necessary to divide sections into their sub-groups because of the extent or character of the matter described. Generally speaking, however, the subject matter has been briefed by "S" groups without employment of sub-numbering.

In the case of sound isolation it has been considered preferable to centralize all information in the S-23 group. Souns isolation is applied to components of many different systems and the extent could not be indicated without employing this method.

Similary, primary reference to main motors and generators is made in S63, in order to avoid segregating individual aspects of single machines under two "S" groups.

At the end of the report is a bibliography which has been cross-listed by the "s" group number.

The first part of the bibliography is an alphabetical list of the reference material. Each one of the titles is given in German and in English and each title is numbered. The titles are shown in two groups: first, those applicable generally, and second, those applicable to the one type of vessel.

The second part is a list by "S" groups giving the numbers of the reference titles which were used in the compilation of that section. This is also divided into two groups: first, those applicable to the vessel as a whole, and second, those applicable to parts of the vessel.

Few of the reports on exploitation of individual components by other agencies, or on operating experience with the vessel, have been received. All report received as of 22 July, 1946 are listed in the bibiography, but the disbanding of the German Submarine Planning group at Portsmouth, as at present constitued, prevents modification of report sections to incorporate material which may be received at some later date.

The text and plan material in the bibiography has been used to supplement personel observation by the personnel of the group on board available vessels.

The vessels on which it was possible to make personnal observations are as follows: IXC-U505, IXC40 U-530, U805, U858, U-889, U-1228, IXD2 U-873, XB U-234 and XXI U-2513 and U-3008.

Hope this help in describing how this material was put together. I still have alot more material that I am still going through. Hope to post soon.

Scott