propeller shaft bertram

Hello

I am back after 2 months in france happy new year to all of you my best whishes for you and your family in 2010.
I got now time to settle those boat problem and will need advice of all of you experianced sailor, particulary as the cutlass bearing doesnot alowed us to put bigger shaft without glass work is there any alloy which allwed us to stand the power and propeller we want for make those 18/20 knots per hours.
In an other hand could you said me which info you need for make sharpest calculation i dont understand well as english tecnical marine vocabulary i am a begeener.
Thanks a lot to all of you
Kind regards
pascal

 

hello Baekmo

My best whishes to you and your family in 2010
i am back to my problem and i wonder if there is some alloy performant enought for give me a prop shaft standing the power gear box ration and propeller size able to give us the expected performance of 18/20 knots .
please what more info should i give you for sharper results as you said for going further preliminary

thanks a lot for all
kind regards

pascal

 

Hello Frosty


As you also live in thailand i wonder if we could some day meet somewhere for a beer ans some talk if it happen to come in samui please be my guest
you can call me anytime on 08 66 82 18 25

kind regards

pascal

 

dear Apex

Cheers and best whishes for you and family in 2010
Did you think i should try to have calculated the hump condition if yes how
Again thanks for all your help

kind regards

pascal

 

A 42 Bertram with only 325 HP is a bit strange?
Inline GM's even stranger

Is it an Australian or American built?

 

dear Apex

Cheers and best whishes for you and family in 2010
Did you think i should try to have calculated the hump condition if yes how
Again thanks for all your help

kind regards

pascal

 

hello Baekmo

My best whishes to you and your family in 2010
i am back to my problem and i wonder if there is some alloy performant enought for give me a prop shaft standing the power gear box ratio and propeller size able to give us the expected performance of 18/20 knots .
please what more info should i give you for sharper results as you said for going further preliminary

thanks a lot for all
kind regards

pascal

 

Hello Frosty


As you also live in thailand i wonder if we could some day meet somewhere for a beer ans some talk if it happen to come in samui please be my guest
you can call me anytime on 08 66 82 18 25

kind regards

pascal

 

Ok Pascal, previously you gave the following info on engines, transmissions and propellers:

Engine power 325 hp @ 2300 rpm. Transmission gear ratio 2:1, propeller diameter 22".

Ad Hoc and I estimated max speed to be ~18 to 20 kn at the best.

What speed do you get with the setup you have today? Do the engines reach just 2300 rpm, or are they overrevving? I would like you to check the transmission ratio once more; is it really 2,0 : 1, and do you have a figure for propeller pitch? How many blades, can you send a picture of propeller?

I'm asking this, because the figures given don't match; either ratio is something else, or engines are running on governor rpm limit.

 

hello Baeckmo
what i give you previosly was i got 22'' 3 blades prop because the original have been stollen before i buy the boat and we hardly go 12/13 knots but those prop are made here in a factory for thai fishing boat and those prop are moving so much water that it looks like the water is boiling 2 meters after the boat but the boat doesnot move .The gear box ratio is really 2-1 it is what is write on the allison small metal .
we do reach 2300 RPm actualy but at 12 knots with soo much vibrations we definitly got prop undersized shaft may be a bit to long after the strout and anyway undersized for bigger prop. what i have been founding out from the time before my purchase was that at the begeening the boat was 450 HP there where 3X4 blade very tin nibral prop like the occidental makers and after the engine have been put down to 325 HP the Oman gen set gone every stainless or aluminum peaces gone electronic gone ................
I try to found out more but no word on the prop size so i gave up looking for before trying to look for after brings this this boat go 18 knots crusing speed for trying to use it because at twelve knots and 110 liter / hour there is no fun and difficult to afford as i am not a pro from this and as there are no professional around only on the other side of thailand and so little and even less trustable and here a white man with something they call a yacht is suppose to be Rockfeller and i got little to put in that all what i know so i am so happy to have you guys for helping and giving light to my search
thanks a lot
kind regards

pascal

 

How much shaft between aft skeg and front of prop?

 

Hello Powerabout

Sorry I Am French And I Dont Understand Aft Skeg Front Of Prop
A Small Help For Understand My Technical Vocabulary Very Poor
Kind Regards

Pascal

 

The distance "C":



(pic abusively taken from Yanmar site... )

 

D, actually and keep it under one shaft diameter

If a single 'P' strut (as was standard) you need to be close to help prevent trouble.
The other issue with them depending on the year built, is how strong the hull is where the strut bolts to the hull.

We strengthened quite a few to prevent vibration.

Its a bit of a job as the fuel tank has to come out.

I assume we are talking a FBSF, Fly Bridge Sport Fisherman yes?

( FB Motor Yacht I havn't worked on those)

Cheers

 

Hello
actualy i dont have this c distance from half the radius to the strut and it doent look like this i will send you one picture and for the d distance i got near 3 time the diameter probably too much for bad and unbalanced prop.
for strengthening it is a kolosal work on this fly bridge sport fisherman and even i was wondering what to do if one day i came to touch and move the strut. got to blow out the rear cabin the tank it would cost a fortune. or may be there is a tric ?
anyway let hope we would not have to strengthening the hull.
kind regards

pascal