Dear Mr. Woolcock and Community,
Intriguing topic. The notebook seems to give a valuable clue, although no dates of original layouts and changes are entered. Also, the writing is not 100% discernible at certain places. Perhaps a separate enlargement of the bottom half of the left page would be helpful.
At the moment, i read the data like this:
Project no. 400 (Olympic)
Reciprocating
Propeller diameter: 23'-6"
Blade pitch: 33'-6" (changed into 34'-6")
Blade area: 160 sq. ft.
Blades: 3
Turbine
Propeller diameter: 16'-6"
Blade pitch: 14'-6"
Blade area: 120 sq. ft.
Blades: 4
Project 401 (Titanic)
Reciprocating
Propeller diameter: 23'-6"
Blade pitch: 34'-6"(changed into 35')
Blade area: 160 sq. ft.
Blades: 3
Turbine
Propeller diameter: 17'-0" or 17'-6" (hard to make out in the writing)
Blade pitch: 14'-6"
Blade area: 120 sq. ft.
Blades: 3
The 3-bladed prop on 401's turbine shaft is one foot larger in diameter, yet each blade still has a surface area of 120 square feet, meaning that the blades have a slightly more slender shape. 360 square feet (3 blades) thrashing through the water at a certain rpm require less horsepower than driving 480 square feet ( 4 blades) through the water, with the same pitch at the same rpm. So, the 3 bladed prop may have been an experiment to allow the turbine to run at a higher rpm, possibly to improve its efficiency or to lighten its load. Increasing the blade pitch of the two wing props would mean a higher load on the reciprocating engines and would reduce their rpm, saving steam (unless the boilers would be made to generate more psi to compensate). Less steam through the reciprocating engine would mean less LP steam through the turbine, making it necessary to lighten its load in order not to lose too much rpm.
Kind regards, greetings from the Netherlands