the Stock game

[Fear the Duck]

Totally hypothetical here, but let's take a look at the perfect world scenario of stock outboard racing. Let's say everyone has the perfect prop for their line, everyone's hardware is rigged and working perfectly, everyone's engine is singing like Dean Martin after half a bottle of Scotch, and everyone has attained the absolute minimum weight possible to make their strategy work. What else is there?
Well, we've got driver skill, driver temperament, water and weather conditions, racer proximity and a thousand and one other circumstances that can't be predicted or controlled.
But as far as things that can be controlled, we still have hydrodynamics, aerodynamics, and the properties of the structure of the boat as well as those of the materials used in its construction.
These are our best shots at making a real game-changer. So, keeping these things in mind, let's talk about those design aspects of hydros and runabouts that are variable, and can be tweaked to maximize or customize aerodynamics, change the way a boat handles a corner, or even tweak the way a driver makes the boat do what it needs to in order to win.
This is intended to be a free-for-all for hydro and runabout geeks. All ideas, concepts, and especially EXPERIENCE are welcome, but just to clarify--- I'm not fishing for trade secrets, so please keep them. I'm hoping we can all share some good ideas and learn from one another's thoughts and experiences.

[Dave M]

All Things Equal

The best tip one can give is:

Nail the start on the fly, and be the first to the first turn. Without this ability you can have the best rig in the country and you will still get beat. Without a good start you stand little chance.

[blueskyracer]

All things equal I have to agree with Dave. A perfect start with all others being early or late is so much fun you will have a big smile on your face and even a record holder will not be able to make up the diffrerence.

[Fear the Duck]

Thanks for the pointers. I was hoping for a little bit more of a design-oriented thread, though.

[Fear the Duck]

Okay, I'll kick this off.
Aerodynamics.
Anybody out there try anything funky with aerodynamics? I read somewhere that a dimpled surface like a golf ball causes the airflow to adhere to an object, reducing the drag caused by the vacuum effect at the trailing end. Anybody try anything with this concept? Also, the least amound of frontal area (picture a silhouette of a head-on view of a boat) will cause the least amount of aerodynamic drag. Within the limits of required measurements, how can a runabout or hydroplane take advantage of this?

[PROPDOC]

Aerodynamics?

Doesn't aerodynamics create the lift that we achieve with our boats no matter what class or size of boat?

We have lift on even the smallest J Hydro and they only go about 30 -35 mph. I agree on the deck side of the boat, aerodynamics may not have as much of an effect until you get into higher speeds, but on the underside it is everything especially the faster that you go.

[fcliff]

Bicycle racers discovered a long time ago that aerodynamics was extremely important to them. They use solid wheels, aerodynamic helmets, and they even flatten the tubes of the bicycle frame to reduce air drag. How fast can a good cyclist pedal a bicycle?

[Fear the Duck]

Extremely important to them, not quite as important to us. The reason they need it more is because they try to weigh as little as possible, so aerodynamic drag is huge for them.
Every little bit still counts for us too, though, in my opinion. In trial-and-error racebuilding, a design needs to show a very noticeable increase in performance to merit the attention and production that boats like the Hemp hydro get today. So why not build a boat with base measurements roughly the same as a Hemp or a Sorensen or a Fralick, but implement as many aerodynamic tweaks as possible on the top side. If it gets a noticeable increase in acceleration or top end, then it was worth it, right? Only thing is, a control group is needed. Same engine, prop, and skid fin could be ran on a "normal" boat with the same hull dimensions, weight, and materials, and the differences recorded. Anyone done anything like this?

[modhydro]

Aerodynamic test at home

Here is one you can try at home without a wind tunnel or any fancy instrumentation.

Hold a rigid notebook (8 1/2 x 11) out of your car window at 40 mph and tell me if aerodynamics don't make a difference at slower speeds. That is only about 5/8 of a square foot of frontal area. I bet you will be very surprised. If you want to see how much increased speed changes the forces speed up until the wind rips it out of your hand or you get pulled over for trying this crazy stunt! Science at home. Gotta love it.

Another thing to think about with smaller classes is that you don't have extra power to work with, so even a little gain goes a long way.

Disclaimer: not responsible for any moving violations that come from this post! I will laugh if you get a ticket though.

Steve

[daveracerdsh]

Stock

Very interesting thread....I also feel that wind resistance is a big factor in racing, but if you look at it the other way....water is something like 900 times denser then air....You can put your hand out the window of a car and hold it there at 80 mph...but there is no way you could do the same thing in the water....it is impossible. I have tried to design my boat and motor to have as little drag in the water as possible....no tunnel, shaped gearcase, as small a turn fin as possible, and so on down the line. Yes, aerodynamics are important, but hydrodynamics are much more important in my view. Just a few thoughts.

[Fear the Duck]

Dave, you bring up a great point with hydrodynamics being more of a factor. It's a fair bit more difficult to understand than aerodynamics, though. Anyone know any tricks to minimizing water friction? I've seen some boats out there running stepped sponsons, is that one of those tricks? What are the pros and cons of having stepped sponsons?

[PROPDOC]

Dave, you bring up a great point with hydrodynamics being more of a factor. It's a fair bit more difficult to understand than aerodynamics, though. Anyone know any tricks to minimizing water friction? I've seen some boats out there running stepped sponsons, is that one of those tricks? What are the pros and cons of having stepped sponsons?

In a word yes. The effect that the boat builder is trying to achieve is less surface area in contact with the water. This is why in offshore racing you see the big deep V hulls with stepped bottoms and planning pads at the back of the boat. Same thing is true with stepped sponsons on tunnel hulls and hydros alike. Key phrase here is "less surface area" this will minimize the friction created on the hull from the water.

[Racers Edge]

Bike/Boats not the same

Bicycle racers discovered a long time ago that aerodynamics was extremely important to them. They use solid wheels, aerodynamic helmets, and they even flatten the tubes of the bicycle frame to reduce air drag. How fast can a good cyclist pedal a bicycle?

This can take a while to properly explain. But since 30 hours a week my job entails properly fitting anyone from serious recreational cyclists to top level pro athletes on road and triathlon bikes, I will take a swing at this one.
To best explain I will break things down from a triathletes standpoint since in a triathlon there is no drafting allowed and aerodynamics is paramount.
First we will talk about the horse power/drag difference. The average triathlete that I fit can produce between 225 and 300 watts of constant power for a one hour maximum effort.(there are some less fit/less gifted athletes that will produce less and a few highly trained freaks of nature that will produce upwards of 200 more watts) A horse power is approx 745 watts. So on average a good athlete can produce about .35 of a hp once they have been biomechanically (not aerodynamically,I will go into that later)fit properly on a bike by me. Most people will see a 5-10% increase in watts through a proper fitting. The size of an athlete (height, width, weight and range of motion) will effect ones speed but on average one can maintain about 22 mph if they are producing 260 watts with no aerodynamic work done.
Most people are blinded by the cool technical features of a bike (aero wheels, tubes of the frame, helmet) as was f cliff. But in all reality the rider them self is 70 to 85% of the aero drag on the bike (85% when fit improperly). Once a rider has has his fit aerodynamically dialed in we can generally get his drag down to be in the lower 70% range. which will increase this speed at 260 watts to be about 24 mph. So a decrease in drag by approx 13% will increase speed by about 9%.
Even though from this one will assume that aerodynamics would make a dramatic difference. Daveracerdsh is spot on by saying how much more hydrodynamics makes a difference than aerodynamic due to the increased density of the watter vs. the air. Also a bicycle powered by the strongest of riders is still only dealing with about 2% of the HP of a stock Yamato 302.
It is more important to focus on decreasing hydrodynamic drag and increase the amount of time you can stay at or near full throttle to utilize the full horse power of your motor through better handling.

John Palmquist
theracersedge.net

[Fear the Duck]

That's where it gets tricky. The less boat you have in contact with the water, the more likely you are to dnf and end up on youtube with what happens in the next corner.
I read somewhere that using rain-x on a boat hull will actually cause it to "stick" to the water. Here's a thought--- find out exactly what points on your hull need to adhere to the water surface while cornering in order to give it the stability it needs to stay right-side-up. As long as these points are not in direct contact with the water while the boat is on straightaway plane, you could have small "sticky spots" that would hold you in a corner, but once the boat raises up on plane in the straight, these spots would be raised away from the water surface. Anyone know of anybody trying this?

[PROPDOC]

3 point hydro's

That's where it gets tricky. The less boat you have in contact with the water, the more likely you are to dnf and end up on youtube with what happens in the next corner.
I read somewhere that using rain-x on a boat hull will actually cause it to "stick" to the water. Here's a thought--- find out exactly what points on your hull need to adhere to the water surface while cornering in order to give it the stability it needs to stay right-side-up. As long as these points are not in direct contact with the water while the boat is on straightaway plane, you could have small "sticky spots" that would hold you in a corner, but once the boat raises up on plane in the straight, these spots would be raised away from the water surface. Anyone know of anybody trying this?

3 point hydro's do this very thing as do tunnel hull (OPC,F1) type boats. These types of hulls take a "set" when they turn and then upon accleration out of the turn the boat starts to "fly" thus getting as much of the hull out of the water as possible. I believe most of the modern designs out there are using this to some dergree or another. Basically what it boils down to is the set up for your particular design to maximize what the boat builder designed into the hull.