dirty hull performance

[brunolund]

just how much does a dirty hull affect performance?

mine has a very rough sandpaper feel to it, and have yet to have time to clean it.

i think it is just hard water build up, but i'm not sure. hope to have it cleaned soon, nut i'm curious. i had it out this way last weekend, and it got 42 mph, which i'm quite happy with.

ps its a 1850 lund tyee aluminum hull.

 

[Gary H NC]

Re: dirty hull performance

I would think just a rough feel to it may drop you a couple MPH.
Mine has the same feel to it on the rear half of the hull.The previous owner let it set in the water for 2 years.The Starbrite hull cleaner took most of it off except the rough feel.
That will be my project for this fall.Taking it off the trailer and sanding and painting it a nice high gloss finish from the water line down..
Mine also runs out at 42 to 43 mph, 21 foot cuddy with a 175 outboard.Not bad for a heavy boat.

 

[LubeDude]

Re: dirty hull performance

Strange as it may sound, you may spend hours cleaning and smoothing out your hull and find that your boat is actually slower. If there is a growth of some sort on the bottom that will slow you down conciderably but race boats actually sand the bottom of the hull to break surface tension.

 

[Gary H NC]

Re: dirty hull performance

I have read that before LubeDude,I guess the rough surface creates tiny air bubbles and puts less drag on the hull. Good thing to think about.
I'm still painting mine this fall a high gloss white,more for looks than to try to get more speed..

 

[JCF350]

Re: dirty hull performance

Strange as it may sound, you may spend hours cleaning and smoothing out your hull and find that your boat is actually slower. If there is a growth of some sort on the bottom that will slow you down conciderably but race boats actually sand the bottom of the hull to break surface tension.

Yep! it's got a name too, called the Coanda effect.
http://en.wikipedia.org/wiki/Coanda_effect


The effect is used constructively in fluidics.

 

[180shabah]

Re: dirty hull performance

I doubt it is creating a huge difference in speed when we are only talking about 40-45MPH. I have a similarly sized boat that weighs in about 3k with myself, wife, full fuel, gear etc. It has been bottom painted, and I assure you my running surface is rougher than just a little mineral builup. It still runs 47-50MPH with 4.3LX (175hp)pushing it.

I have been talking about the sand it off and repaint thing for three years now, but I will probably just hit it with another coat black Ablative and be done with it.

 

[flashback]

Re: dirty hull performance

on a power boat, its not hardly noticable, on a sailboat, it is...