Drag Boat Nationals

[Hot Foot]

I will be headed to the SDBA drag boat racing at Lake Bryan on August 27-28. If you have never seen this type of action in person, it is an awesome display of raw horsepower.

Here is a preview of what to expect!

http://www.dragboats.com/video/dsl/04_11_IHBA_619_1.wmv

http://www.star-cards.net/StarCam/schedule.pdf

Drag Boat Specifications!

These boats have unbelievable HP...

http://www.aquaholicracing.com/boat.html

[roneski]

There is a guy that I work with who runs in one of the "slower" classes. Open cockpit, not the capsule boats. He still runs 9 sec. That's just nuts.

[struan87]

FIVE SECOND quarter mile?
How can that even work? How do you get that much traction in water?

[partyman66]

Hey.... That boat sounds just like my G35!

I wish.........

[Jaylin]

Originally Posted by struan87

FIVE SECOND quarter mile?
How can that even work? How do you get that much traction in water?

No traction, just forward thrust.

[struan87]

Originally Posted by Jaylin

No traction, just forward thrust.

Holy crap!

So they work like jets?

[Hot Foot]

Originally Posted by struan87

Holy crap!

So they work like jets?

No jet pump, it's called a V-drive, direct engine HP to the prop. Which is that little gold thingee underneath the hull.

[struan87]

I still don't get it. If they apply that much power to the prop, wouldn't it just start spinning in the water without pushing? I know there's a term for that, when the prop spins without creating thrust...

[Hot Foot]

Originally Posted by struan87

I still don't get it. If they apply that much power to the prop, wouldn't it just start spinning in the water without pushing? I know there's a term for that, when the prop spins without creating thrust...

PROPELER PITCH
Pitch is measured in inches and it is a theoretical measure of how far the propeller should move through the water in one revolution if there was no slippage at all. For example, an 18" pitch prop would move 18" forward in one revolution (provided there was no slippage).

The primary effect of pitch on your performance is the same as the gear-shift in your car. Higher pitch numbers are like the higher gears (4th and 5th) in your car, more speed but less acceleration. Lower pitches are like lower gears (2nd and 3rd): more acceleration but less top speed.

http://www.solarnavigator.net/images...ers/pitcha.jpg

[partyman66]

-PROPELER PITCH
The throwing motion used in Warner Bros cartoons by animated characters where the thrower of an object(The pitcher) spins his throwing arm in a proper-like circular motion for several seconds before releasing the projectile in the direction of the intended target. Such a motion is typically accentuated by a comical sound effect and the pitch is often tailed by flames or other overly dramaticized visual indication of extreme projectile speed.

[AZ-G35]

Originally Posted by struan87

I still don't get it. If they apply that much power to the prop, wouldn't it just start spinning in the water without pushing? I know there's a term for that, when the prop spins without creating thrust...

Struan it is called cavatation.

Jets skis work in a similar way. Prop shaft connected directly to the motor. There is an opening on the bottom of the boat before the prop that allows water in and then forces it out through a nozzle in the back. When the prop turns it sucks in water from the opening and pushes it out the nozzel. There is a small tolerance between the prop and the nozzle so the water is forced out the back. The faster you get the jet ski going the more water that enters to opening before the prop. Speed of a jet ski is regulated through the pitch of the prop and the size of the nozzle and also the motor size. I would assume a jet boat to work similiar with bigger components.