Help with Propulsion

[standman]

Hi All,
I enjoyed a 16ft. boat I built and decided to built a 49' version. I am now at the stage where I need to install the propulsion.
Power will be from twin 360HP 2200 RPM Diesel
ZF V drive 2.06:1
Waterline length 45'
draft 2ft
beam at waterline 12'
vessel weight about 13 tons loaded
Target max speed 24 cruising 18 knots
propeller 28 x 34.8 x 3 (55% coverage) (recommended size by prop maker)
So what I have available are 2 or 2.5" Stainless 304 shafts. I'm worried with 2" ( should I be?)
rudder is twin 3.06 sq. ft. - adequate?
The propeller strut i need to fabricate, single or v type?
about 6' of the shaft is exposed - will this need 2 struts?
30KG Delta anchor ok?
TIA for the input

 

[Mr Efficiency]

Quite a step up in size, shall we say about 30 times ? Any pictures or drawings ?

 

[standman]

Quite a step up in size, shall we say about 30 times ? Any pictures or drawings ?

will resize pics and video as I can't seem to upload them

 

[standman]

Quite a step up in size, shall we say about 30 times ? Any pictures or drawings ?

 

[Mr Efficiency]

OK, that gives a fairly good idea, what is she made of ? Is it a scaled-up version of the small boat ? My initial thought was she might slap on those very wide chines.

 

[standman]

OK, that gives a fairly good idea, what is she made of ? Is it a scaled-up version of the small boat ? My initial thought was she might slap on those very wide chines.

FRP, very close to the design of small boat. I thought too the wide chines would cause slamming but the much deeper kiln actually push water to those chines and somehow acts like a suspension and allows to plane quicker.

 

[tonipu]

With 3 blades 55%
Some cavitation problem and strenght

 

[tonipu]

4 blades 67% blade area

 

[tonipu]

4 blades area 75%

 

[tonipu]

i will go with 2.5 shaft, and if you can find with aisi630

 

[tonipu]

and 4 blade prop

 

[tonipu]

from the strut to propeller is better to go out, no more than a shaft diameter

 

[tonipu]

Prop and strut

 

[standman]

i will go with 2.5 shaft, and if you can find with aisi630

First, thank you for the input. I'm not familiar with aisi 630 but a google check says it is equivalent to stainless 304 which is what I will use. I wonder why the prop maker gave me those specs? Is it because they are confident with their material? ( Hypothetical) As for the strut to propeller, anything beyond shaft diameter cause vibration? TIA BTW, How's your boat coming along?

 

[tonipu]

it is about 3 times stronger than 304