slippery bottom

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bcarli

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C Dory Year
2006
C Dory Model
25 Cruiser
Vessel Name
Soulmate
Hi Everybody,
I am considering a new ( new to me anyway ) strategy to improve my fuel efficiency...I am planning on lightly sanding the bottom paint on my cd to a very smooth finish ( 220 grit???).. Normally when bottom paint is applied it's rolled on and that's it, but the roller leaves a rough surface which I'm thinking might create drag??? Anyway, if anybody has any thoughts about this I'd love to read about them. I want to feel like I'm doing everything I can regarding fuel/mileage and the price of gas.
see you in friday harbor.
 
It will be interesting to hear what the general consensus is, but I suspect that at the speeds most C-Dory's travel hull smoothness isn't a major factor.

With truly high speed boats (and aircraft) smoothness is a major factor, but that is because of the geometrically increased drag at higher speed.

On the other hand, while fuel economy may not be increased by hyper smoothing of your hull, a particularly dirty hull (e.g. marine growth, barnacles) WILL have a very bad effect, even at slower speeds. ...and if bad enough may even prevent planning speeds.

I suspect that for the time/money expended, learning to cruise at displacement speed, vessel loading, and honing-in on the proper pitch for your prop will give you optimum miles per gallon performance.

Casey
 
Casey":2yse4kgw said:
I suspect that for the time/money expended, learning to cruise at displacement speed, vessel loading, and honing-in on the proper pitch for your prop will give you optimum miles per gallon performance.

Casey
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Concur Casey. Bill, IMHO, I think your search for economy will be akin to driving around town looking for gas that is a penny cheaper and expending much more than you will save in the process! Let us know how your experience works out! Don't ask me how I know! :roll:

Charlie
 
I agree with Casey on this. Also, sanding the hull smooth will result in less bottom paint. On one sailboat we raced, we had the bottom paint sprayed on - it was as smooth as the manufacturer gelcoat. Of course, 1/10 of a knot might make the difference in that circumstance.

We ran our CD-25 for about 6 months before we pulled it out for bottom paint. The application was done with a roller and brush, and there was no noticeable difference in speed at given RPM before and after.

Prop the boat for the load and elevation. Keep the weight off as much as possible (not possible for those who do more than day-tripping). Keep the bottom clean; bottom paint doesn't mean no bottom cleaning, rather it means easier bottom cleaning. I still get in the water on occasion to scrub. A fuel flow meter will give you some guidance on most efficient running for given conditions.

Best wishes,
Jim B.
 
Alok":3iy0kkd8 said:
Dimpled golf balls fly further than smooth golf balls...

http://www.spruancegroup.com/blog/bid/3 ... innovation
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That was my thought too. I may be that small bumps on the bottom help to hold small bubbles of air and actually reduce friction in the water relative to a completely smooth surface. The swim suits with a rough skin to mimic that of a shark, actually provide better performance than other suits.
 
They mold many kayaks now with a finely textured bottom surface in an effort to allow hybrid laminar flow and decrease drag at kayak speeds. Not sure if this applies to higher boat speeds.
 
All kinds of theories! Not sure if any are proven. When I was racing sailboats, we also had the paint sprayed on and burnished. We would wipe the bottom with rags before races--if a little growth--the green scotch pads. As time wore on, we would start with 600 and then go to 1000 grit sand paper. I would start at 600, not 220 for smoothing.

Bottom paint does slow a boat down--and it is more noticable at higher speeds than displacement speeds...
 
I have had great success with Interlux with the UP additive.
It is rare , but worth the effort to find .When applied properly, it also has the unusual effect of bringing back great memories .
Marc
 
Wefings":27m1mbiw said:
I have had great success with Interlux with the UP additive.
It is rare , but worth the effort to find .When applied properly, it also has the unusual effect of bringing back great memories .
Marc
Click to expand...

Marc,

And I thought you knew what you were talking about :oops: :twisted: :xnaughty :P :lol: :smiled

Harvey
SleepyC :moon
 
I like the golf ball effect, saw it on Mythbusters last night.
 
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