I don't get it. I don't understand why guys strip their bottoms. Sure mine has some build up, but I hit the uneven spots with 40-grit, touch up the spots where I power washed the paint off, paint the water line and she goes in. My neighbor took his boat down to bare glass, repainted it and the bottom felt just like mine. How does a build up of bottom paint make the boat perform inefficiently? I hear this often yet have never seen a case study to prove me wrong. In fact, in the Northern Chesapeake (brackash)I use the cheap paint; that Micron stuff is over $200/gal. I clean the bottom when we go swimming and other than a little slime she's clean as a whisle.
Bottom Love...
- Thread starter Tucker
- Start date
Each coat of paint probably represents a few pounds of weight. Each 'uneven' spot creates drag.
2 good reasons to strip old paint off.
My 23 y.o. Grady had many layers of paint on it when I got it. Did sanding and repainted, but it wasn't for a few years when I decided to start fresh and had it soda blasted, and wallah--- blisters. Paint is a great concealer, and things could be going on you don't know about.
I'm glad I stripped b/c it uncovered blisters and led me to barrier coat. And led me to Petit Ultima ablative paint, which is the bomb. Had the boat in the water 2 years straight, hauled last November, washed down, and looked great.
I'm sure you have absolutely nothing to worry about...Gradys never get blisters :roll: ....
2 good reasons to strip old paint off.
My 23 y.o. Grady had many layers of paint on it when I got it. Did sanding and repainted, but it wasn't for a few years when I decided to start fresh and had it soda blasted, and wallah--- blisters. Paint is a great concealer, and things could be going on you don't know about.
I'm glad I stripped b/c it uncovered blisters and led me to barrier coat. And led me to Petit Ultima ablative paint, which is the bomb. Had the boat in the water 2 years straight, hauled last November, washed down, and looked great.
I'm sure you have absolutely nothing to worry about...Gradys never get blisters :roll: ....
I have to agree with Tucker, people make too big of a deal about the bottom paint. I had an 88 Offshore that was painted each year until I sold it last season. Over that time, there was no discernable difference in performance. Figure a few pounds a year for 20 years and you have added 80 pounds to the boat - not noticable. For a race boat, a clean, waxed bottom helps, but a Grady? Now that there are new paints offered I will certainly use them to prevent build up, just because I am anal, but I don't believe there is a noticable difference in performace with old style, cheap paint - built up over years.
I use an Ablative paint and by the end of the season most of it is down to bare minimum so build up is not a problem
Gman25
GreatGrady Captain
Depending on how one paints the boat, especially near the keel, too much paint application will buildup thick and end up cracking, even ablatives. The thicker the paint, be it from one or more layers, the more it is likely to loose adhesion and crack and flake.
And some people just don't like seeing the contour changes between layers, rather have it looking like topside paint.
No matter what I do and what paint I use, always get flaking paint even when starting bare to hull. I have been know to apply too thick a coat since I'm lazy when it comes to pushng out the roller further before re-wetting.
And some people just don't like seeing the contour changes between layers, rather have it looking like topside paint.
No matter what I do and what paint I use, always get flaking paint even when starting bare to hull. I have been know to apply too thick a coat since I'm lazy when it comes to pushng out the roller further before re-wetting.
and without stripping down to gelcoat i might not have known about blisters until it was too late. I understand that performance-wise it probably doesn't make a difference, and aesthetically from more than 10' away it looks the same--and you really didn't say if your neighbor is just anal or he had major build-up of hard epoxy bottom paint--but there's a time to strip down to gelcoat and not just 'cover it up for another season'.
Yea, I tried that ablative paint. Problem is when you scrub the water line to clean the scum line you remove too much paint and by end of season you've scrub $50 worth of paint off and down to fiberglass.
89 sailfish
252 g with twin 175 suk 4strokes on bracket.
stripped to gel coat the 2nd year we owned it. found bad repairs that were allowing water penetration. found areas where the gelcoat was gone (cloth not wet out when built and gaps in chines where there was NOTHING behind the gel coat and impact areas where gel coat ws severley damaged) so i was able to proeperly fix those and prevent further damage. folks in the yard were busting my chops, "you ganna race that thing?" because I was being so anal about the finish.
6 double coats (6 gallons) of interlux 2000 barrier coat with light sanding between day one and day two and two layers of ablative. Result: increase of almost 5kts on top end and almost .5 miles/gallon.
I dont need a study to tell me the work was worth it. i did it because I wanted to know what was under the chipped and chunking paint; i expected barely noticeable changes in mileage or speed. the changes are incredibly obvious it even feels better underway. the only negative is the brakes don't work so well as they used to. :roll:
252 g with twin 175 suk 4strokes on bracket.
stripped to gel coat the 2nd year we owned it. found bad repairs that were allowing water penetration. found areas where the gelcoat was gone (cloth not wet out when built and gaps in chines where there was NOTHING behind the gel coat and impact areas where gel coat ws severley damaged) so i was able to proeperly fix those and prevent further damage. folks in the yard were busting my chops, "you ganna race that thing?" because I was being so anal about the finish.
6 double coats (6 gallons) of interlux 2000 barrier coat with light sanding between day one and day two and two layers of ablative. Result: increase of almost 5kts on top end and almost .5 miles/gallon.
I dont need a study to tell me the work was worth it. i did it because I wanted to know what was under the chipped and chunking paint; i expected barely noticeable changes in mileage or speed. the changes are incredibly obvious it even feels better underway. the only negative is the brakes don't work so well as they used to. :roll:
Thanks Bob, did it. I'm still trying to get over Buster's 5 kts & .5 miles/gal. That's freakin incredible! I din't think you could get that much difference between a painted and unpainted bottom.
Those are great performance number increases. I only get 1.1 to 1.2 mph with my express and am sure I wouldn't see that type of increase (but I would strip my hull and wax it daily if I could - cut my fuel bill in half). My numbers are in line with Grady's.
A WARNING FROM AN OLD SHIPYARD GUY. DO NOT SAND OR GRIND BOTTOM PAINT WITHOUT COMPLETE PROTECTION. PARTICULARLY DO NOT INHALE THE RESIDUE!
he indicated he had water penetration, so he was likely carrying around a bunch of extra weight in the form of water in the hull. Also the "bad repairs" he found underneath - could have been creating drag.
All just guesses.
I also had some of those voids where the gelcoat chipped and there was empty space behind it, mainly on the chines.
Unfortunately for me, I redid my bottom the same off-season I got a new engine put on, so I can't judge my performance from the re-doing the bottom.
All just guesses.
I also had some of those voids where the gelcoat chipped and there was empty space behind it, mainly on the chines.
Unfortunately for me, I redid my bottom the same off-season I got a new engine put on, so I can't judge my performance from the re-doing the bottom.
journeyman
GreatGrady Captain
On subject but maybe a different tilt - My hull was painted with a hard coat (non ablative) as it's first coat 2 years ago. Then, last year, I sanded the hull and used an ablative as it's second coat. The hull looks great. I pressure washed it last fall, no peeling, chipping etc. When I touch the painted area, the ablative paint rubs off on my hand or brush or jeans if I inadvertently rub up against it. Do I need to sand last years' ablative coat or just add to the ablative protection with another layer. The first hard coat is black and I'm using black ablative so I can't gauge the coverage. I know, I should have used a different base color but that's "water under the boat" now.
Journeyman the shade of black is different between an ablative paint and hard paint so it should be easy to see when you start wearing down. Yea, an increase in fuel efficency of .5/mile is a 40%-50% increase depending on the boat, again freakin incredible.
"MY RESULTS MAY NOT BE TYPICAL"
My bottom was horrible. I don't think it had ever been properly prepped. I started to strip it by hand/chemical and there were layers of every color and type of bottom paint sold since 89 on it and several layers of paint that appeared to be other than bottom paint. There were areas with no paint and areas with probably 20 layers. It was rough and I was not able to get to a stable layer without taking it all off. I averaged about 1 mpg my first year with twin 4 stroke 175s. I didn;t just remove paint; I resurfaced the entire wet surface of the hull starting with west systme epoxy and microballoons and sanding and fairing and then the barrier coat and then the bottom paint. i put probably 200=250 hours into it after the soda blasting.
My bottom was horrible. I don't think it had ever been properly prepped. I started to strip it by hand/chemical and there were layers of every color and type of bottom paint sold since 89 on it and several layers of paint that appeared to be other than bottom paint. There were areas with no paint and areas with probably 20 layers. It was rough and I was not able to get to a stable layer without taking it all off. I averaged about 1 mpg my first year with twin 4 stroke 175s. I didn;t just remove paint; I resurfaced the entire wet surface of the hull starting with west systme epoxy and microballoons and sanding and fairing and then the barrier coat and then the bottom paint. i put probably 200=250 hours into it after the soda blasting.