Memorandum and Minute
With the introduction of the new A.P.C. shells capable of carrying through thick armour at long ranges and of bursting about 40 feet behind the first plate struck, it was decided to test critical points of the design of H.M.S. "HOOD" to see whether the protection was adequate against our own 15" A.P.C. shell.
A. Trials at upper belt (7") at Section 91.
Projectile. 15" A.P.C. shell, Striking velocity 1430 f.s. corresponding to a Range of 19500 yards. Angle of descent 20°.
See diagrams 1 and 2 on ensclosure.
Trial 1. Fused Shell- shell perforated and burst 40 feet behind 7" armour "in the magazine".
Trial 2. Fused Shell- Magazine roof thickened from 1" to 2". Shell perforated and burst 34 feet in rear of 7" armour. Magazine Roof plate blown to pieces.
Trial 3. - See diagram 3 on enclosure.
A weighted shell was used and the 3" ?(illegible handwriting)? representing ?(illegible handwriting)? main deck was wrecked but the shell did not penetrate and glanced off.
This the modifications to the main deck shown in diagram 1 may be considered to give fairly good protection to the magazines from shells which hit the side armour. This addition of 3" plating & of this proposed 2" ? (illegible handwriting)? plating in ?(illegible handwriting)? of the magazine were approved and fitted to H.M.S. Hood.
B. Trials at "HOOD'S" decks.
See Line B on diagram 1.
Projectile 15" A.P.C. weighted shell.
Striking velocity 1350.
}Corresponding to 25500 yds range.
Trial 1. Shell perforated all three plates and buried itself 5 ft deep in the ground and was recovered intact.
Proposals were then made to surrender ?(illegible handwriting)? weight in "HOOD" be removing certain of the 5.5" guns and their ammunition and by removing the above water torpedo tubes etc, the weight thus saved to go in thickening the main decks as follows:-
Trial 2. Same as above only different target.
Shell perforated all plated and buried itself deep in the ground- probably it wil be recovered whole./p>
Trial 3. Not yet done. Same as trial 2 but with 3" (120 lb.) mild steel plate instead of the 100 lb. armour plate. It is probable therefore that the weight available cannot protect "HOOD'S" magazines from plunging fire at ?(illegible handwriting)?Ranges unless the ship were rebuilt with a deck of thick homogeneous armour plate.
1. Series B. Trial 3.
"Hood's" decks" reinforced with 3" mild steel same as trials 1 & 2 (B. series) hit target as shown:-
Result. 15" A.P.C. shell perforated all plates, presumed "whole", shell being buried in ground and not recovered. The shell turned down about 15° while perforating the "armour" deck (i.e. centre plate of target).
2. These trials showed that neither 3" mild steel nor 2½" armour quality steel added to the main deck are sufficient to keep out the 15" A.P.C. shell at this angle of impact. It was therefore proposed (C. Sec C.1527/18 attached) to complete H.M.S. "HOOD" without any further additional deck armour and to press on with D.N.C.'s trials of improved "special treatment steel" plates etc. in hopes of producing plating which would meet the case without adding undue weight, and at a cost less than that of "armour quality" plating. This poilicy was carried out & ? (illegible handwriting)? trials are pending.
It was further proposed to carry out a further trial at "HOOD" deck target, the main deck being reinforced with 4¾" roof plate quality armour. No approval for this proposed further trial was given (C. Sec. 01527/1).
3. H.M.S. "HOOD" was completed with following additions and alterations to original designs as regards protective decks:-
(a) 1" H.T. Steel
Roofs to 15" magazines......
(b) Main Deck
The weight involved in the above additions was compensated for by removing
an extra 1" H.T. Steel plating was added.
3" H.T. plating added at after edge above the slope
(c) 4 - 5.5" guns.
(d) 4 - above water torpedo tubes.
(e) Director tower aft.
4. Submit that trial in para. 2 above at X be approved and further action then considered.
