nofords

I'm buildnig a 72" mono (scaled up plans of doug's 48" mono) and will be running twins.
What are the typical distances between props "ctc"?
I scaled of a pic of a Bonzi 84" Classic (17" beam) and my rough calculations are 6.5" apart and 1.5" above the keel. Does this sound right?
What would be the closest I can place them w/o loosng too much efficency?

Thanks
Darin

Justaddwata

My Feedback: (3)

Depending on what your doing with your rudder. Aim for sufficient clearence for the largest diameter propellers you plan on running plus another 5/16" or so.

For surface drives aim for them to be level with the running surface where they exit the transom.

nofords

See there i am torn as to where to put the drives. I had planned on using twin inline rudder systems and starting with 75mm - 82mm props (twin 25cc engines).
With a single surface drive, propshaft center is +/-1/4" above the keel right? If i place the twin drives at the lowest place on the transom 4" apart, they could be as much as an inch higher. This places the boat further into the water. Is this ok?
What do I need to do to the bottom of the boat to reduce drag? keelsons? Step it?

s2sinner

Photos PLEASE.

P.S. One question....Why you scaled the plans of the 48 and you don't make it with the original plans of the 72 ????

nofords

because i didn't want to build the offshore version and the scaled 48" allows for the room I need to run twin engines w/o too much hassle on cg and engine for/aft placement

s2sinner

I see. Good to know. I just start with that hobby and Im asking all the time.....After all Im happy that always get one answer

I build also the 48'' and one a bit bigger 54''.

Somewhere on the forum are some post about.


Ok....another question.....Where is the photos? Or you keep it for surprise?

nofords

I am currently at work. I cannot take any photos at this time. Will do later.

s2sinner

Here is my 54'''