Does Waxing a boat hull increase speed?

[duflo]

I was wondering if waxing a boats hull would increase, decrease or have no effect on speed. Seems to me it would tend to help at least topside to shed the water droplets and the boat would be dryer. Dan

[T.S.Davis]

This is a pretty age old question. It usually is reduced to name calling.

Many think a scuffy bottom helps break surface adhesion. I'm in that camp.

Then I wax the tops. The trouble with that can be that it's hard to get the tape to stick if it's cold out.

[kfxguy]

ive never seen back to back gps proof. hopefully someone has done this. Im in the waxed hull camp. I dunno why but i think that because water doesnt like to stick to a waxed surface, tends to make me think it would help. think about it....water beads quickly off a fresh waxed car....effortlessly.....on a rough finish it sticks to it. Im not certain that water sticking to it is what you want. Sure there are those that believe there is a boundry layer of water and the water hitting the boundry layer moves past it easier....im not sure im buying that. Id like to see some back to back proof myself. Everyone has thier opinion, thoughts, theories....but proof is what i like to see. But then again, I could just be totally wrong. lol

[fox88gt]

Professional boat racers prepare the bottoms of their hulls by lightly scuffing the surface at a 45 degree angle to the keel. Its difficult to explain why (i'll give it my best chance here), but waxing the bottom will actually create more friction that a lightly scuffed surface. Your example of a freshly waxed car is a good example. The water does bead from the surface with minimal effort...but have you noticed how a dull, faded car will actually hold a sheet of water on the surface and not let it roll off? When you have that surface of water sticking to the bottom the hull, the water passing underneath the hull can actually do so easier because water-to-water friction is less than water-to-hull friction no matter how smooth or well waxed the bottom is. I dont have back-to-back proof (like gps data) but I figure if its good enough for the teams that spend major dollars to go boat racing, its good enough for me:) I have heard its a 1-2 MPH on a full size boat. I do wax the topsides for easy cleanup after a trip to the lake though.

[Rumdog]

Scuff. My aero marine sprintcat handled completely different after I scuffed the ride pads. Loosened right up.

[rickwess]

The proof is in the "shark skin" suits that swimmers used to use before they were banned for being too fast. Essentially, they provided a rough surface for air bubbles to form in and reduce drag in the water.

[madmikepags]

Do this test, take your hull with fresh gel coat and or wax, put your finger in water and slide it across the surface. Then scuff it w some 300-400 grit and do the same thing w your finger, you will be surprised to see the gel coated/waxed surface your finger will stick to, the sanded surface your finger will slide over with very little resistance.

[kfxguy]

Do this test, take your hull with fresh gel coat and or wax, put your finger in water and slide it across the surface. Then scuff it w some 300-400 grit and do the same thing w your finger, you will be surprised to see the gel coated/waxed surface your finger will stick to, the sanded surface your finger will slide over with very little resistance.

Now YOU have a GOOD point. I was just about to post that in my opinion, at 70, 80, 100mph. ....water doesn't have time to stick to the hull.

[785boats]

Mike.
That's the very test I make people try at the lake side to prove to them why I scuff the bottom of my hulls.

Fox88gt.
That's the first time I've heard of the 45 degree orientation. I've only ever heard of (and done) along the hull. I must give it a go.

I even scuffed the shine off all the bright shiny bits that drag through the water, on a couple of boats, like rudders, turn fins, struts, stingers, trim tabs etc.
I don't know if it made any difference. But the theory states that it should.

[kfxguy]

So what grit? im very tempted to do this but i want to be able to buff my carbon fiber hull back out. i dont care about 1 or 2 more mph but i would like to prove this theory one way or the other. 2000 grit?

[madmikepags]

300-400 grit is good, if you buff it back out you defeat the purpose of it? I do it on all my boats. The increase in speed is more noticeable on monos, especially in the corners when a lot of the hull is in the water.

[kfxguy]

300-400 grit is good, if you buff it back out you defeat the purpose of it?

I just wanted to do it to find out if it works or not. personally i dont want a scuffed bottom on my nice carbon fiber hull so id buff it back out. Id be willing to do it for informations sake, but im not doing 400 grit because it will be too much work to get the scratches back out.

[madmikepags]

It's not just speed, its also amp draw and the boats run more consistently too. I had a LSO boat that kept overheating and slowing in the corners and just not running right, I sanded the bottom and the boat was a completely different animal.

[Rumdog]

You only have to Buff the last steps in the ride pads. You can even use the red Scotch-Brite pads

[martin]

Im a firm believer in scuffing, I have noticed that my boats after cutting the power glide further & more on top of the water. Un scuffed they settle quicker into the water & glide less.

[kfxguy]

Man, you guys are kidding right? Placebo effect? :) Looks like I'm going have to try it. How high up do I need to go? Just the last ride pad? ��

[martin]

Personally on a v hull I scuff all of the underside & on a cat I scuff all the ride pads, so it has the desired effect also at lower speeds where theirs more hull in the water. As already mentioned I think you get a slightly reduced amp draw because of reducing the water tension when scuffed.

[kfxguy]

So......popular consensus says scotchbrite pad or 400 grit?

[martin]

I use 400grit wet & dry sanded with straight longitudinal (front to back ) strokes.

[madmikepags]

This is not a placebo effect, I don't race a boat w/out sanding the bottom, all ride surfaces.

[Fluid]

The "proof" is in what successful full scale racers do. On fast boats wax is slower, period. I tested a smooth versus sanded bottom at a SAWs race through timing lights (not a flakey GPS) and recorded a real difference. While a SAW rigger literally floats over the water with little sponson/water contact, other hull types do have significant hydrodynamic drag at speed.






.

[T.S.Davis]

Back in the dark ages, Dick Crowe used to say he used 80 grit to scratch angular lines in the surfaces.........well, I think it was Dick. Dick was the first guy in the states to hit 80 mph.

[flraptor07]

I was helping a guy down here at the Offshore Grand Prix in Sarasota, he was trying to set the Kilo record in B production with a 22' Maxim Stingray (V hull) I built the 355 small block for it. The 600grit wet sanded hull was good for almost 3mph, good enough to set the record for that class @ 81mph that year previous record was 77mph. Needless to say I'm a believer!

[T3Merc]

I run a Quartershot T3 and with a blue print job
and 400 wet sanding I gained a solid 1.5 mph.
stock 200 merc I run 104.5 for a best.
Sanding for sure.!!

Dago

[keithbradley]

This is news to me...I guess I had it all wrong.

So let me get this straight...

You guys are saying that the bottom of the boat is supposed to go IN THE WATER???
I knew I was missing something...
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Seriously, some have tested this and found a difference (for both sides, believe it or not), and some have tested it and found no difference. This applies to both models and full scale boats. I have met plenty of people who claim to gain a mph or two by waxing the bottom, and others who say scuff. I could see both having positive or negative effects and I don't really think there's a rule that will suit every application. Theoretically the smooth bottom boat (not even considering wax here) has more flat surface area on the bottom, while the scuffed bottom has more total surface area. The idea with the scuffed bottom is that air will hopefully get trapped in between the scratches and net a lower total surface area that contacts water. Whether or not this happens is debatable and has been debated here and everywhere else since Moses wore short pants. What is often not discussed is the difference in lift characteristics that may be realized and whether it may be beneficial or detrimental to a given hull, but not to another. If a smooth bottom really does displace more water, it may also increase lift, creating a bit of a paradox in regards to this notion.

If you're looking to get the last little bit out of a hull, try it. It's not going to cause a dramatic decrease in speed, that I'm sure of. More importantly though, pay attention to the design and quality of your hull. I've seen boats that have a nasty hook get the "light scuff" treatment, when they would surely benefit to a much greater degree if they were sanded with real sandpaper and a flatboard. I tested one hull last year that picked up 27mph after changing nothing but the bottom...seriously. Obviously that is an extreme case but it's definitely quite common to increase efficiency in a boat just by sharpening a few edges and straightening out some curved bottoms that shouldn't be.

[Fella1340]

It sounds like if your into high end racing this might be a option. It would be nice to see actual proof of just how much performance it does add in a rc boat application. I can't see it completely transforming the way a boat handles though. I grew up with and around fast boats, most were run for sport and I don't recall anyone taking sand paper or scotch bright to hull. If it was such a boost in performance it would have been picked up years ago by the top speed boat builders and some type of micro ridging would have been designed into the hulls. It was often debated and agreed it had potential but not to the point where it was worth damaging the hull. There's a lot of other ways to tune and setup your boat that will net better results. Come race day I don't believe it's going to make the difference in podium finish. By the way, there's absolutely nothing flakey about a quality gps system. There extremely accurate and the best option out there for 99.9% of us. Running through the traps may prove the boat is capable of obtaining the speeds in back to back runs but it's not a difficult thing to simulate on your own. For myself I like to make sure whatever I am running is able to consistently run a given mph, not just a blip on the screen. Most others are honest about it to. There will always be someone who feels the need to stretch the truth just so he can say his boat is xx fast. Saying gps is flakey is just not true. I really comes down to who is using them.

[Zach]

Interesting subject.......

[TRUCKPULL]

When Racing, it does not matter how fast your boat is in a straight line.
What matters is, Getting a good start, Driving the pins, and how many seconds it takes to do the 6 laps.

Larry

[keithbradley]

Running through the traps may prove the boat is capable of obtaining the speeds in back to back runs but it's not a difficult thing to simulate on your own.

Really? Running through the traps doesn't even give you a "top speed". It gives you a time that it took you to travel between beams that are 330ft apart, and that time is used to calculate the average speed that a boat would have to travel in a perfectly straight line to cover that distance. Top speed will ALWAYS be higher than trap speed, and sometimes the difference is more extreme than other times.

The hard part about running through the traps is not reaching a particular speed. It's accelerating to a desired speed before the first light, maintaining said speed for a long distance in as straight of a line as possible, and in whatever conditions that time on that day have to offer, without crashing the boat... then turning around and doing it again (assuming the equipment doesn't malfunction and it does pick up both of your runs), because if you mess up the back-up pass, you have to do it all over again. Only back-to-back passes going opposite directions count.

The idea of comparing a GPS speed to an event trap speed is silly. It's like comparing running 100yds on an empty football field to a 100yd kickoff return in a superbowl game. One of them is a lot harder to do than the other, even if both people can say they ran 100 yds.

[Bduncan]

I have read the pros and cons of waxing compunding hulls and also a mirror finish on the leading edge of a prop verses satin. I don't have the empirical data data to support it, but I have had my best runs with this Cheetah with a mirror bottom finish on the boat and a highly polished leading edge on the prop. No doubt! it would be hard
to compare the two given the conditions would unlikely be the same. not saying this is (boat truth) if there is such a thing. but as far as I know this cheetah is the fastest ever on gps. 86.1 on 8s.