improve performance of 42C

[omecojh]

anyone have any experience on improving the performance o a 42C? I have heard of using larger trim tabs, wedges or decreasing the size of the keel.

 

[bostonhatteras]

Make the bottom as smooth as possible. Remove unecessary through hulls or change to flush as opposed to mushroom head through hulls. Fair or remove all old coats of lumpy bottom paint. Fair in struts. Remove as much weight as possible from the boat. You can only get a fat cow to move so fast. Get rid of the shaft couplings (ive heard they take 1knot off the speed). Horsepower vs weight and resistance is what to think about. No magical cures. Automotive racers consider weights as small as 1 pound and aerodynamics. In your case hydrodynamics.

 

[luckydave215]

Make the bottom as smooth as possible. Remove unecessary through hulls or change to flush as opposed to mushroom head through hulls. Fair or remove all old coats of lumpy bottom paint. Fair in struts. Remove as much weight as possible from the boat. You can only get a fat cow to move so fast. Get rid of the shaft couplings (ive heard they take 1knot off the speed). Horsepower vs weight and resistance is what to think about. No magical cures. Automotive racers consider weights as small as 1 pound and aerodynamics. In your case hydrodynamics.

Or add horsepower......

 

[jim rosenthal]

Ah, yes.....

Putting the boat on a diet will get you back to design speeds, more or less. Minimizing drag will help, too. Making sure your tabs work as intended so you can trim the boat for best speed helps, too.

And putting in big engines REALLY helps, if you love the boat and want to go fast. In a 42C you could fit Cummins C series, or M11s if you really wanted to go crazy......

 

[Colwyn D]

Do you have a speed in mind. Mine with Cummins 420's will do 25kts, full keel and plenty of bits sticking out but reasonably light I suppose. I think lightness helps all round, quick onto plane and minimum trim tab needed. I run less than 3* nose up with no down trim.
What year boat and what engines are we talking about.

 

[polarizer]

what is your goal by improving performance? fuel, speed, ride, all the above. What are your expectations on speed, vs spend. whats the budget? how do you use the boat, cruise, fish, both. if fishing, how far a run to the grounds? what power do you have? 903's?
lots of good recommendations here.
Lifting rails, Keel cut, larger injectors, fuel pump, cooling systems, air flow, prop optimization, carry less load, fuel, water, high performance bottom paints, shaft covers etc. etc.

 

[Passages]

Don't go nuts. A Hatt is not a hot rod. Overpower and you'll be keel walking. You don't want that.

 

[Avenger]

You might try taking a look at this thread. It's about a 41, but there were some comparisons to the 42 and performance numbers that may help.

http://www.samsmarine.com/forums/showthread.php?14286-1986-41C-Series-II-Poor-Performance

 

[jim rosenthal]

Don't go nuts. A Hatt is not a hot rod. Overpower and you'll be keel walking. You don't want that.

I agree, and a 25kt cruise ought to be enough for one of these older hull designs. They really weren't intended to go much faster than that.

 

[omecojh]

Do you have a speed in mind. Mine with Cummins 420's will do 25kts, full keel and plenty of bits sticking out but reasonably light I suppose. I think lightness helps all round, quick onto plane and minimum trim tab needed. I run less than 3* nose up with no down trim.
What year boat and what engines are we talking about.

I have 671TI's, 1.5:1 clutches turning 24 x 24 four blade wheels. DD rated these engines at 390HP, but JT went to 410HP by running up the revs.

The extra 60 HP you have must make a big difference. I can cruise at 17 kts at 20000/2100 rpm.
It would be nice to cruise at 20 kts but it wouldn't be worth the cost to repower.

I was looking for some suggestions to get a few more knots at cruise. I'll admit i could save a few pounds but fishing with 400 gals fuel, ice and people is typical of my trips.

Thanks for your comments.