MJR and all other Pro Boat Builders

[HRTV]

Hey Marc or anyone else that might want to chime in on this thread, could you walk us non boat builders through the two different types of boats used in US Pro Boat Racing and European Pro Boat Racing.

The photos below are of a new European 250cc boat, can you tell us why they choose to lay so far forward etc.. Why are these types of hulls not raced in the states ?? I also have a few more thoughts but lets use these to get the ball rolling.

Thanks

[Composite Specialties]

Designs

Sure, here is the quick version.

European Boats:

They are designed for rough water and tight turns. They pack a huge amount of air in the front of the boat and relieve a good amount of air out the back. They do not use tunnels like the American boats do, they have rear pads or shoes that raises the rear of the boat off the water and these pads extend beyond the back of the boat by about 6" to 8". This extension from the back of the boat is the pivot point for the boat and allows the air to dump while the front of the boat continues to pack and flow more air from the front.

The drivers are so far forward lying down so they can balance the front end of the boat while it is packing and flowing air under the boat at top speeds.

They also have the transoms inset much more than American designs to help control the lift and balance of the front of the boat.

The rear chines start out at a specific predetermined degree angle and ends up at a totally different specifically determined degree angle at the end of the boat. This helps to enable the boats to get on plane much faster for lemans starts and allows the boats to turn very sharp on one pin turns.

The gear cases have to be much deeper in the water for the rough water and the rear pads that the boat is running on.

These boats are built with safety in mind, such as composites cockpit side that tie into the decks.

American boats:

They are designed for smooth water and wider turns. They are designed with flat bottom and tunnel built into the bottoms. They do pack a specific amount of air under the front of the boat but the air is controlled thru the bottom lift and the break in the bottom. These boats are much harder to control in rough water but are very fast in smoother water.

The drivers are lying down or kneeling down, a little further back towards the rear of the boat so they can balance the front end of the boat while it is packing and flowing air under the boat at top speeds. This helps to control the front lift of the boat.

They also have the transoms inset much less than European designs to help control the lift and balance of the front of the boat.

The rear chines start out at a specific predetermined degree angle and ends up at the same specifically determined degree angle at the end of the boat. This helps to hold the boats in the wider pin turns at high speeds but could possibly slow down the boats on very sharpe one pin turns.

The gear cases are much higher towards the surface of the water since the bottoms are flat on these boats.

These boats are also built with safety in mind, such as composites cockpit side that tie into the decks.

Summary:

I have always been very impressed with European designs and incorporate as much of the European technology as I can in my designs.

[racer4s]

Boat design

While your talking about boat design, I have acouple of questions that I would like explained to me.

Todays CSH - Seems that most of the fast boats have a bottom that uses a break about 34" or so from the transom. I know Sutherland, Hemps and I think Arlt uses this design on his composite boats. Why??? What is the reasoning behind this??

I have also seen D Murray run very well against some very good OSY boats wih a laydown giles that has the pads added to the transom. I think Lucas come over a couple of years ago and took second in Depue with a european style OSY composite boat. Does your previous explanation cover this??

Finally, I"ve watched in awe Shannon run away from everybody in his bezoats that has tunnel's in the bottom. What is the difference???

Thanks for any help in trying to figure this stuff out.

Brent Smmons
20-P

[DougMc]

Todays CSH - Seems that most of the fast boats have a bottom that uses a break about 34" or so from the transom.

What does "break" mean?

[racer4s]

What I really mean is a step in the bottom. It looks like about 6mm maybe?
Brent

[DougMc]

What I really mean is a step in the bottom. It looks like about 6mm maybe?
Brent

I don't know what a step is either. I'm boating term challenged, but learning. This is a good post from which I hope to learn.

How do I find the step or break on my CSH and how do I measure it?

[Sean Augustine]

Step

I don't know what a step is either. I'm boating term challenged, but learning. This is a good post from which I hope to learn.

How do I find the step or break on my CSH and how do I measure it?

Hi Doug

the "step" is a perpindicular (sp?) line from airtrap to airtrap,across the width of the bottom.

viewing the boat upside down (insert caustic driving ability remarks here) it steps down from the front to the back.

the purpose could better be explained by someone else.

hope this helps.

Sean

[Bill Huson]

break . . .

Flip boat upside down. From the transom run a loooonngg straightedge, or tight string line forward and even with the bottom near the transom. At some point the bottom will drop away from the string. You have found the break. From the break forward the bottom shape can assume many wiggles and curves depending on the design.

[racer4s]

Doug,
I think Bill Boyes has some great pictures of him building a CSH/OSY Hemp kit that shows the step in the bottom of the boat. I think it is under a new boats for 2006 thread.

Then there are the flat bottoms that are very effective like; Sorensen, Roper, Pavlick, O'Conner, Giles, Z-Craft, Keylard, Runne, Tec-craft, Furnal and I think Dawes. There's probably more that I'm not aware of.

I was just trying to get some of the great builders like MJR, Sam Hemp, Steve Roskowski(sp), Furnal, Pavlick, Bill Giles, Shannon Bowman, John Runne, Tom Cronk, etc. to educate some of us on what makes a great bottom work and why.

Brent

[David_L6]

I don't know what a step is either. I'm boating term challenged, but learning. This is a good post from which I hope to learn.

How do I find the step or break on my CSH and how do I measure it?

The step in the bottom of this boat can easily be seen in this picture. (Disregard the black colored pieces that have been added in.) The break can be seen also just not as easily as the step can be seen.

[jeff55v]

Step design...

That's a good photo David.
My first B&H D hydro was once owned by Jerry Weinandt. Jerry told me that step causes the air to roll and become turbulent as it passes by it. This turbulence helps to keep the back of the boat free. Jerry told me he had a lot of people ask him why he doesn't run a tunnel in the bottom of his hydro. Jerry would tell them, " I do have a tunnel... a 36inch wide tunnel!"

BTW, The boat worked very well.

[hydroplay]

If you have to ask if your boat has a step in the bottom, it doesn't!. If it had one, it would be obvious when you are sliding it up on trailer bunks, etc.

A step is a real step where the front piece is actually deeper than the rear piece. With a sharp edge there, it will create a low pressure area where the water will boil ( yes water will boil at low temperatures if the pressure is low) and form bubbles that decrease drag. While laminar flow may be great for the fluid flow, we want a very turbulant, mixed state flow for minimal drag on the bottom. The rear section may be at a slightly different angle to give the boat attitude desired.

David's boat pictured above does not have a step but it does have a number of breaks. A break is a hollow with a sharp edge on the front like a step but the two sections remain on the same plane, discounting the break.

Steps and breaks are different but both function somewhat alike to decrease drag when the bottom is dragging along in the water. Of course we really want to have the hull fly so as the boat gets up higher above the water as the speed increases, these devices become irrevelant. But at lower speeds, they may decrease drag.

[reed28n]

terms

I'll throw in another term. The S in the bottom of the boat, describes the shape or design of the lift in the bottom. Much like Mark mentioned the shape of the bottom is something people play with. The break locations can be moved for drivers weight or skill and is moved for the speed of the class.

All this plays into your set up. Kick in, kick out and in some cases going from boat design to boat design different props.

Everyone has many theories and there are some drivers who will work at it hard enough they will win with just about anything.

The boat design rarely gets you a good start.........

[reed28n]

thread killer

Man you guys are giving me a complex, everytime I reply to a good thread, everybody stops. Hello? Is this thing on?

[Richard K.C. Mo.]

Terminologie Challenged?

Whaat is the diff. in a stepp and a break and why are there no regulations as to these , as there once was/was once ohh heck you know what i Mean?
RichardKCXMo

If you have to ask if your boat has a step in the bottom, it doesn't!. If it had one, it would be obvious when you are sliding it up on trailer bunks, etc.

A step is a real step where the front piece is actually deeper than the rear piece. With a sharp edge there, it will create a low pressure area where the water will boil ( yes water will boil at low temperatures if the pressure is low) and form bubbles that decrease drag. While laminar flow may be great for the fluid flow, we want a very turbulant, mixed state flow for minimal drag on the bottom. The rear section may be at a slightly different angle to give the boat attitude desired.

David's boat pictured above does not have a step but it does have a number of breaks. A break is a hollow with a sharp edge on the front like a step but the two sections remain on the same plane, discounting the break.

Steps and breaks are different but both function somewhat alike to decrease drag when the bottom is dragging along in the water. Of course we really want to have the hull fly so as the boat gets up higher above the water as the speed increases, these devices become irrevelant. But at lower speeds, they may decrease drag.