Trawler Concept

BTW, look at Grand banks 32. It has been in production for 27 years, since 1965. Its clones, Integrity/island gypsy 32, are still in production.

So this boat should not be too far from truth ...

The main problem seems to be a lack of speed, since power evolved from 78 hp to 210 hp in 30 years. And some even got 2 * 200 hp.

 

Grand banks 32.

With only 32 ft of boat speed is not in the offing.

6k is about all most folks will put up with in terms of noise , RRPM , and fuel use for this style full displacement boat.

FAST FRED

 

I checked my spreadsheet this morning, and i agree with the specs.

SL 1.34 7.34Kts 21.5 HP DL248 15000lbs
SL 1.4 7.67Kts 25.74 hp 30LWL
SL 1.5 8.2 Kts 33.10 hp

So this nice light weight hull will be fine at speeds around hull speed. But when you get much faster the HP requirement will go up drastic. Hench the early post of 134 hp will be more correct for the 12 knots. My spread sheet i made after talking to Robert Beebe to get some of his formulas. The next time i called his wife said he had passed away. She said he got to make a last cruise and enjoyed it very much. GS

 

Form MikeD displacement / semi displacement spreadsheet:
(more elaborate than mine)


figures for Shaft horsepower. (ie at the propeller)
For engine power, add 1.5 for each shaft bearing, 2.5 % for gearbox and 2.5% for error. So a total of 8 %.

No wind condition:

7.150 kts 19.6 hp
8.46 kts 36.8 hp
9.77 kts 56 hp
11.1 80 hp
12.3 kts 108 hp

with 30 kts wind

4.5 kts 34 hp
5.8 kts 50 hp
7.150 kts 73 hp
8.46 kts 102 hp

for info, 8.46 kts with 15 kts wind need 57 hp.

I have found MikeD spreadsheet on this forum, but I do not remeber where. You will have to do a search.

 

Thanks guys. I appreciate all your help. I think I'll do semi-disp with a 150 b.h.p. diesel.

 

Has someone some figures for the GB 32 ?

the figures I have gice 7.5 kts @1800, 8.7@2300 , 120 hp engine.
other give 7.4@2000, 8.5@2400, 135 hp engine.

But MikeD spreadsheet gives over 11 kts with only 110 hp. including losses.

Why so many difference ?

BTW, 8.5 kts for a 16hp/ton boat is rather low.


Thanks.

 

If you are interested, I have got a newly finished design of a 14,4m. Oceon-going trawler which will be build for a german guy. If you want to built the boat I may help

 

It's design now, but building is probably not in the works...lack of $....