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View Full Version : Buffing and Waxing = Slow Boat
Mini Max
05-03-2004, 03:45 AM
Once you accept that a straight bottom is fast, then what is the surface left? Well, Its been sanded of course.
Don't Buff
Buffing heats the surface and can cause the sustrate under the surface to post cure and shrink here and there. You do not want that.
Don't Wax
Wax is Slow. How slow?
Take a piece of something, maybe 2 feet square that replicates the surface finish of the bottom of your boat, whether gel coat or paint,. Sand the whole surface uniformly with 220. Then tape off a 2” by 24” stripe down one edge. Sand the remaining surface with 320. Tape that off. Sand next with 4 something. I get tired by the time I get to 600 but I am old. Buff, wax, polymerize, and goose grease, whatever, the remaining strips.
Now for the test. With the sheet flat, place a drop of water on each surface treatment. Slowly slope the panel at an ever increasing angle. The drop that transits its surface treatment and that reaches the bottom of the panel first should identify what to do your boat bottom to go fast.
Where do you think the name “Turtle Wax” came from??
PS
accept that a straight bottom is fast
The only question I have is how the manufacturer makes that shiny new gelcoat hull without buffing it.
I wonder if someone has taken test panels and hung them in the water off a boat and measured resistance? I know water runs off a waxed car way faster than down my rough aspalt driveway, but does that show the true high pressure relationship of hull pad to water at speed? I sanded mine with 400 but could not tell if it helped (meaning it went less than 1/2 mph faster on the speedo of my slow boat). It didn't go slower however, from the shine it had before.
Mini Max
05-03-2004, 10:18 AM
Boatbuilders don't get more money for buffing their product. They have been known to use old or worn molds to make parts and post finish and buff them to compensate.
sho305
05-03-2004, 10:50 AM
I thought you could not make a molded gelcoat part without buffing it to get a nice finish.
Here is another wax/coating/sanding type post: http://forums.screamandfly.com/forums/showthread.php?s=&threadid=48059&perpage=15&pagenumber=1
Mini Max
05-03-2004, 11:15 AM
Go look at a Bayliner. They are nice and shiny and I guarantee that they fired the tooling department if production got a mold that produced parts requiring post finishing or buffing.
sho305
05-03-2004, 03:08 PM
I don't know much about molds, last someone told me even the release agent leaves a film you have to buff. Maybe I'll wax my bayliner pad just to see if it changes anything for kicks.
Travis Fulton
05-12-2004, 09:33 PM
SO WHICH FINISH IS THE FASTEST???? 500 OR 600:confused:
Kavalk
05-12-2004, 09:51 PM
The Gayliner's may be shiny, but they sure are thin, crooked, poorly built, and generally an embarassment to the boat building community.
And the shiny part sure doesn't last long.
I have no idea why you included their mention on a thread that was discussing speed.
Bayliner/Speed. Oxymoron. Mutually exclusive. Take your pick.
I guess they have they're place, but ................
FRED
Mini Max
05-13-2004, 06:36 AM
My reference to Bayliner was that shiny parts come from good molds. Bayliner parent company US Marine spends the equivilent of the GNP of a small country on "PD" (product developement and molds). The most popular small boat molds are "turned" (parts cycled) 3 times in 24 hrs. This means that they don't have any time whatsoever to achieve final finish or remidy cosmetic defects by patching, sanding or buffing
sho305
05-13-2004, 08:41 AM
The bayliner is no performance boat, it is cheap. But I have to say mine is an '83, over 20 years old and beside the bad unsealed transom I replaced and some other detail rot...the skin is fine. It was owned by someone who lives on a lake here and had it in the whole summer. The only things I can find are two spider cracks I'm guessing where the stringers end in the bow down low. It was faded, but came up to say 85-90% shine with a good buff. Pos it may be, but for a 90hp rated 16' open bow with lots of use I really can't say it just fell apart in a 'short' 20 years. I doubt people took care of yugos like they would a BMW either. I'm just saying it looks like it has done well for such a low cost item. Even the hardware is fine save for the plastic transom trim and the typical loose screws in the interior panels. Most of the half painted seat bucks were bad at the hinges but the stands are glassed and ok.
Beyond that, I have had at least four older boats similiar to this 16'/85hp in size/power/style/weight (not full-on speedy boats) and run others. None of them would break 40mph. This one shows 45 on a prop calculator.
Yes, I've buffed out much, much more expensive and larger boats that faded in only a couple years.
I'm sure if I ran in some rough water and pounded it something would break, but it is faster than all the other stock +15 yrs old boats roughly that class I been in. I think it is a great deal for the price, but that is not the point of this site no doubt. You people should still have a little pride knowing S&F could make it go faster with only tuning really, over 5mph faster.:) on a lowly bayliner.
I sanded this with 600 wet. I think it got 1/2 mph, but not sure. As soon as I have another hull ready, this will help pay for a motor.
blkmtrfan
05-13-2004, 08:50 AM
At a boy you tell em :D
Mini Max
05-13-2004, 12:38 PM
All other things equal, it appears that the experience of the board members is that surface finish only, is a benefit of a fraction of a knot faster. I'll take it!
Anti fouling bottom paint, however makes you go measurably more than a knot slower.
Its horsepower, weight and straight for the best bang for the buck.
sho305
05-13-2004, 01:02 PM
:D :D
Sorry, couldn't keep quiet like I'm supposed to:eek: But it was relatively easy to fix, and no core to mess with. The people at the lake love it, so I'm sure I will have no problem peddling it. With the same gearing as my inline, the force spins about 5700rpm with a 19p SS prop; nearly what my 1500 I6 does with a 20p laser on the checkmate 17'.
The key here is it was a good project to fix and sell because aside from the transom, the rest was easy to fix and shined up well. Even the transom wood was only 18" wide to replace.
btw, I did paint the bottom/pad to about 4-5' up from the transom. I used the VC epoxy with teflon in it and left it rough as sprayed, a little orange peely. That was before I ran it the first time so I don't know about gains. Later I ran it back to back when I did the pad with 600 and the LU; both just enough to take the shine off. It looked to go 1/4 - 1/2 mph better but it was splitting hairs at a speedo read around 45 at the time. Bottom looks straight to the eye.
capt.jim
05-19-2004, 07:45 PM
your best bet is to wet sand the bottom of your hull wiyh 800 the 1200 being careful to keep sanding motion from bow to stern. this works because the water gets directed through the tiny scratches left from wet sanding. it works pretty good
ps wet sanding with paper finer than 1200 is not necessary:D
10.5' Tunnel
05-19-2004, 08:00 PM
My farce is still going strong;) :D :eek:
sho305
05-20-2004, 08:10 AM
Mine is sitting here getting rained on near every day:rolleyes: Trying to get a nice 12 gallon tank off a friend for it now, but I don't work on it in the rain. I just can't figure what to do to make it faster this year. I have to run it again due to large non-boat projects.
staylor
05-28-2004, 09:35 PM
I've tried it both ways on various hulls running up to about 75mph top speed. I've never seen any appreciable difference in top end from running the stock bottom waxed or unwaxed or the stock bottom stripped of wax and sanded linearally with 600 grit. I suspect the difference may show up on much faster hulls, but not on anything that I've tested to date. Same goes for all the teflon and so-called speed coatings. As for Bayliner, its a mass produced entry level boat that a lot of people are quite happy with. You can knock them, but they've allowed many, many new customers to come to the marine markets. In the long run, this helps to keep costs down for everyone. Also, older Bayliners were not a mass produced boat. Our family had a very early one and it was well built with little evidence of a chopper gun being used. No signs of hull flexing or stress cracks after 15 years. It lasted forever with a series of good old "Tower of Power" Mercs on it.
FX10 Superboats
06-04-2004, 09:12 PM
The molds are highly polished. That is why there is no need to sand. This is a 30'Superboat Y2K deck coming out of the mold
capt.jim
06-05-2004, 01:21 AM
thats true if the boat is new but a couple years down the line is a different story it dosen't matter much as the speed gains are minimal wet sanding is better for sailboat racing no b.s.
Yamaha 70 c
06-10-2004, 12:10 PM
How much do anyone claim to have earned on sanding their boat?
What kind of speed range do you earn most, sailig boats or super-fast hulls?
By the way, who wants a sanded boat, in stead of shiny smooth gelcoat?
:confused:
sho305
06-10-2004, 08:28 PM
I think most sand the pad area only, that would be wet at WOT. Can't see it anyway unless you crawl. I might have gotten a half mph on my slow sled hull, not sure as it varies that much but seemed to vary a half higher on average. So at 45, I could see 2-3 at 80+mph if it extrapolates like that.
FX10 Superboats
06-13-2004, 12:22 AM
600 sanded my buddys Allison XR2000 , didn't'seem to make a difference. Maybe a mile an hour at over a 100. At least that's what he told me after he ran the boat. I was just hired to sand it. Bow to stern.
Bones
12-03-2005, 08:44 PM
Mini Max,
As far as your test goes which was fastest? Would this apply to an aluminum boat also?
Thanks
Tim
Jeff_G
12-05-2005, 10:14 AM
You guys aren't getting the physics or the reasoning.
If you run a normal pleasure boat, by all means run the original shiny hull. Wax it if you want. The wax will help prevent water absorbtion, water blisters.
If you are an all out racer and the boat is used exclusively for all out speed then the sandpaper will do the trick. First the bottom must be as perfect as possible. That is where the most speed gains are, the surface finish is secondary. Once the bottom is perfect then you can finish the bottom area. It is only necessary to do the final 3 or 4 feet in most boats. Offshore boats would take more.
Lightly sand with wet 220 to 400. Finer is not necessary. The theory being that water flowing aganist water is faster. The rougher surface of the boat holds the water aganist it. So the flowing water will run aganist the water, not the hull.
You would in all probably not be able to measure accurately enough any speed gains from the surface finish itself on most boats. You would be able to see it in lap times or elapsed times.
As someone racing you look for all the help you can get, every little bit, no matter how small, helps.
As for making boats first, shiny boats sell, secondly a properly made mold will produce a shiny part that with the proper release agent will allow the part to actually come out of the mold. A rough mold would not release the part, it would physically bond the part to the mold.
Bones
12-06-2005, 07:31 PM
Thanks Jeff,
That makes sense.
Mark75H
12-06-2005, 09:21 PM
Bob Wartinger who holds about 115 speed records (honestly) finishes with 400 grit
Dave S
12-08-2005, 06:34 PM
I went to Bill Fales, a guy that worked at Dupont and raced 1000cc FRR. He showed us the bottom of his race boat, which was sanded the last 1/3 of the boat. He gave me a wet rag and told me to push it on the bottom, and it was easyer on the sanded part. :) I went home Impressed after seeing all his neat 6cly loopers and more speedmasters than ******** :rolleyes: I went home and thought WHO races on wet RAGS....... :D Funny Story :cool:
SportJ-US-1
01-18-2006, 02:53 AM
Bob Wartinger who holds about 115 speed records (honestly) finishes with 400 grit
And all bet Wart doesn't wet sand either.
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