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Tug
01-25-2003, 09:20 PM
Is there any type of wax or coating that can be put on the bottom of a hull to that may add a 1-2 mph. I have read some articles and they say that water on water makes you go faster. Since wax on the bottom of the boat makes the water to water option impossible since the water runs off the wax what is the best solution if any to add speed?

Greg Maier
01-25-2003, 09:25 PM
Tug,

There is a coating that West Marine sells called SeaSlide.

West Marine (http://www.westmarine.com)

Do a search on SeaSlide Bottom Coat

http://www.donzi.net/photos/SeaSlide.jpg

I have never used the product, so I have no opinion as to the validity of the claimed speed increase.

Paul Storti
01-26-2003, 11:51 AM
I tried that stuff supposedly guaranteed 2-3mph didn't do anything. and it wore off after one trip.

Bryan Tuvell 33ZX
01-26-2003, 12:12 PM
Paul, everyones say not to (speed reduction), but I wax my hull anyway, I have not noticed any gain or loss. So why not.....
....
Good old McQuires on my back a couple times a year. Just to help preserve it and keep it spotless.
Bryan

Chris-007
01-26-2003, 01:32 PM
Is that true... No wax on the hull?

Where do you stop?

Shanghied Again
01-26-2003, 03:18 PM
In Racing the the duller the bottom the better. Waxing just adds more slip to the hull, No speed loss are gain. I wax mine just to keep my boat clean and new! :D

Tug
01-26-2003, 05:37 PM
I hate to say it, but my interim boat between two donzi's (a BAJA) seemed to lose speed after I waxed the bottom with mothers wax. I thought I would gain but I think I lost 1-2 mph. I read the article soon after. Now I have a new '03 zx and am hesitant to wax below the waterline.

MOP
02-06-2003, 04:47 PM
I do not believe in smooth bottoms, one example. Stars & Stripes when it raced in Austrailia they added the Boeing rivlets to the bottom and gained 2/10 of a knot don't sound like much but did help them win. My own personal experiance when I was racing Rag boats, at first you could see your face in my boat bottom. Then after Fremantle I figured I would try a stipled surface, that year I won my division and boat overall at Block Island and got a write up in Soundings Mag. Today it is obvious if you introduce air under the hull it goes faster, point in fact look at all the step bottoms. However I have also poroved that a real bad bottom sick with paint is a fair bit slower than a freshly painted bottom.

Scott Pearson
02-06-2003, 09:05 PM
ok...few things. When I worked for PPG we where working on a clear that had no surface tension. Also called self cleaning clear. I dont know how this would work on a boat but it would be interesting.

Also...if you wetsand the hull with 1000 grit paper it will give you speed. Like Frank C said...the duller the better.

(NJ)Scott

RICPAZ
02-07-2003, 08:05 AM
Why would a dull hull give you more speed??? I would think a rougher hull surface would create more drag and friction along the water surface which would slow the boat down.

And a smooth hull, especially one that has been freshly waxed, I would think would slide across the water much more effortlessly thus increasing the overall speed.

Anyone have a technical explaination why you are saying the reverse is true???
-Rich

Greg K
02-07-2003, 09:02 AM
Something about a boundary layer with the duller finish...same principles with the dimples on a golf ball..if I'm not mistaken they fly farther with the dimples than smooth.

In other words...
When fluid flows over the surface at relatively low speeds, (speeds that a typical boat would run are relatively low compared to many other applications such as air over a jetliner wing), it flows in what is called a laminar flow pattern. Essentially it flows smoothly and evenly over the surface. This smooth flow has a particular drag coefficient. When the flow reaches a high enough speed the flow pattern changes to what is known as turbulent flow.
Under turbulent flow conditions the drag coefficient is significantly reduced as compared to the drag coefficient under laminar flow conditions. Here is where waxing comes in: Turbulence at the surface/fluid interface can be induced at lower velocities by roughness of the surface. In other words, a smooth surface would facilitate a smoother flow pattern and thus higher drag than a rough surface. One of the best practical examples of this effect is golf balls. The first solid golf balls were smooth with no dimples. It did not take the pros of that day long to figure out that a ball that had been hit several time, scuffing up the surface, would fly farther than a new ball right out of the box. Pros began to use their practice rounds to hit all of the balls that they would use in the actual tournament rounds to scuff them up before the tournament began. Once the manufacturers understood what the pros were doing they began to produce balls with the pre-made "scuffs" and thus the birth of the modern dimpled golf ball.

Also found that when the hull is blueprinted, the last 6 feet or so is sanded with 400 grit in one direction...front to rear not side to side.

BUIZILLA
02-07-2003, 09:03 AM
Scott Pearson:
Also...if you wetsand the hull with 1000 grit paper it will give you speed. Like Frank C said...the duller the better.(NJ)ScottThis is absolutely the truth. I used to sail in Junior Olympic competition, and we would wet sand the bottoms with 1000 paper routinely. It was a GUARANTEED picker-upper.
The wax actually is a protectant that adds *tension* to the surface. Wet sand 1/2 of a sample fiberglas item, and wax the other half...run your bare fingers across it,.... then put it UNDER water, and run your fingers across it again..amazing difference.
In fact, in the last Junior Olympics event that I sailed competitively in Europe,(when dirt was young) we actually sprayed the bottom of the hull with a graphite paint...

Jim

boldts
02-07-2003, 09:18 AM
Ricpaz, it's like when you trim the drive out and get the boat hull out of the water. Your speed increases because there is less material in contact with the water. Another example would be if you've ever noticed after launching your boat off a wave or wake it seems to accelerate just a tad and you can feel the drag as the boat re-enters the water. This feel for the water is what makes a race boat throttle person great or just average at running the boat.

Boat manufactures have developed slots in the hull bottom to do the same thing. By introducing air under the hull, you also get less wetted surface in contact with the water and speed increases with less HP required than a wetted hull would need.

I'm no expert by any means, but I guess the ruffness of the hull at speed would not effect drag because it is so small and would also be removed from the water by the air it is creating? One question I have though, if you use 1000 grit sandpaper on the bottom, you must have to put something back on the hull bottom right? Otherwise, wouldn't the pores created with the sandpaper attract blisters on the bottom of the hull?

In my opinion, elbow grease beats spending large amounts of cash to go faster if there is no danger of damaging my prize possesion.

boxy
02-07-2003, 10:47 AM
Bryan Tuvell 26ZX:
Good old McQuires on my back a couple times a year. Just to help preserve it and keep it spotless.
BryanBryan I think I speak for everyone in saying "If your back is so hairy that it takes a waxing with Meguires to keep it smooth and shiny" Thanks for thinking of us.... eek! eek!

MOP
02-07-2003, 11:03 PM
Smooth does not always equate to less friction. I worked for may hours on a set of small block heads. I took them to a renowned speed shop to flow bench them. The owner said the looked like crap, I had polished them like a babies butt and opened them up a bit. We ran one chamber and logged the flow. He handed me a aluminum dowel with same really rough cloth and said knock all the glaze off. When done that chamber flowed 7-8% better, So if you think Slick is fast you are a fool and will follow the rest!

Damn I like Drunk Nights!

tim b
02-08-2003, 11:02 AM
www.hyspeedkote.com (http://www.hyspeedkote.com) I was going to try this stuff this season on my Mako,
just sold my 16', but still have the need for speed.
Has anyone else had any luck/tried this stuff??

Tim

HyperDonzi
02-08-2003, 11:15 AM
M.O.P.:
I do not believe in smooth bottoms, one example. Stars & Stripes when it raced in Austrailia they added the Boeing rivlets to the bottom and gained 2/10 of a knot don't sound like much but did help them win. My own personal experiance when I was racing Rag boats, at first you could see your face in my boat bottom. Then after Fremantle I figured I would try a stipled surface, that year I won my division and boat overall at Block Island and got a write up in Soundings Mag. Today it is obvious if you introduce air under the hull it goes faster, point in fact look at all the step bottoms. However I have also poroved that a real bad bottom sick with paint is a fair bit slower than a freshly painted bottom.Hmmm.... Maybe I should keep the bottom paint on....

Air 22
02-08-2003, 10:19 PM
Dork hit the nail on the head. wink The friction at higher speeds creates tiny air-bubbles that you hull rides on...littles wheels between your hull and the water. The rivets on Stars & Stripes hull creates this effect even more. We tend to apply knowledge of wax on our cars although smooth etc... beading off the water but this is not the same principle w/ your hull. Air on water is faster than water on water. Being a jet pilot myself... Dork's right-on about laminar flow :D
smileybo

MOP
02-09-2003, 01:38 PM
A little more, it was explained to me years back that when cylinder head ports were shiney the the flow tended to bounce creating waves there by reducing the amount of flow. But when roughend a layer of tiny molecules formed along the surface stopping the bouncing and a much larger amount was able to flow. I saw the difference on a flow bench. And the difference in speed at Fremantle with Stars & Stripes. Led me to try the roughened surface on my race boat (sail bote) it worked very well for me. It is true most of our boats spend most of the time with 60-70% out of the water but whats left I feel should not be real smooth but slightly rough.

CDMA
02-09-2003, 08:43 PM
You guys are so close. Having a dull bottom will create a faster boat but the reason is slightly different. As said there is laminar and turbulent flow. Laminar flow should be considered smooth flow and turbulent flow disrupted flow. The drag coefficient of turbulent flow is considerably higher then the drag coefficient of laminar flow. Now when your boat runs you have what we call a boundary layer, which is a layer of speration between the water and the hull. The greater the boundary layer and the earlier is occurs the less resistance a ship/boat will encounter. By creating this matte finish we are influencing the boundary layer. By creating this dull bottom we are creating turbulence which while at first may seem counterproductive but in the end it is not.. By adding this artificial stimulation we force the separation, or boundary layer, to occur earlier. As soon as this initial stimulation creates the boundary layer the flow separates from the hull bottom. When this separation occurs since there is now no longer any disturbance the flow becomes completely laminar and therefore the lowest resistance is created.

Chris

They have entire courses on this stuff.... frown

HP 600SC
02-09-2003, 09:10 PM
Gald we have an in house expert on "Artificial Stimulation".........personally I prefer the real deal! eek!

CDMA
02-09-2003, 09:18 PM
Ted,

Maybe with some artifical stimulation we could get to see your boat????
:p wink :p wink
Chris

Air 22
02-10-2003, 09:41 AM
Chris..

Very similar classes in aviation! wink But now its 3 dimentional...

Drag types...
1- Induced Drag...decreases w/ speed. it is the portion of the total drag force that is created by the production of lift.
2-Parasite Drag...It is created by airplane surfaces that disrupt the smooth flow of air and create turbulence. The elements of parasite drag include form drag, skin drag, friction drag, and interference drag. Structures that protrude into the relative wind or impede the smooth flow of air are form drag. At the microscopic level, a wing's surface apperars quite rough. A boundry layer of air clings to this surface, creating small whirling eddies called skin friction drag. NASA research has pioneered techniques of boundry layer flow control, laminar airflow wing design, and microscopic surface refinements. However...skin friction drag can never be totally eliminated. Another contribution to parasite drag is interference drag, which occurs when various airflows over the wing meet and interact. for instance the air-flow along the wing root is delfected by both the wing and fuselage..
The total drag of an airplane is the sum of induced and parasite drag. Induced drag is the predominant factor at low speeds, and parasite drag is the predominant factor at higher speeds. the intersection of induced drag and parasite drag lines corresponds to a point on the total drag line where drag is at a minimum. This is the piont where the aircraft is operation at the best ratio of lift to drag, or L/D.max If all other factors remain constant, induced drag varies inversely w/ the square of the airspeed...ie if the airspeed doubles, induced drag decreses by a factor of four. For you math types here is the formula. Since lift varies in proportion to the square of the velocity, doubling the airspeed results in the production of four times as much lift, assuming you use a constant angle of attack. At higher speeds, drag also increases in proportion to the velocity squared.

L=CL S p
------------- V2
2

L= Lift
CL = Coefficient of lift
S= Wing Surface area square feet
p= Air density ( The greek letter rho represents the density of the air in slugs per cubic foot)
V2 = Velocity squared (Velocity is in feet per second)

Thats all folks...hope it helps :D