Crossflow vs. Looper

[bradford]

Hey Skools, What about drug smugglers who clamp on four yamaha 250's to the back of a boat that looks like it was built in someone's backyard?

[Airslot]

Skools in 98% correct and BrainCT is a touch right as well. Technically you are looking at "diminishing returns" as the horsepower continues to increase the gains become smaller and smaller. There is a line, where when reached, it takes huge amounts of additional power to see very small gains. That is the area reffered to as hull speed. On a V-20 per say, with a 150 you can get 43ish mph, add 50 hp and you add 4 mph. Put 500 hp on one and you'll likely get mid 60's in theory. If you jumped it to 600 you'd likely see little or no increase. The hydrodynamics of the last little bit of drag just can't be overcome, efficiently at least. That's the main reason that the big boat speed records only inch up. HP is easy to find and stuff into a 40'er. For them the HP isn't the limiting factor, the hull form is.

Airslot

[Skools Out]

hey remember that pic tin posted of the drug boats with 6 non counter 250's wow

[THEFERMANATOR]

Originally Posted by Skools Out

hey remember that pic tin posted of the drug boats with 6 non counter 250's wow

There's one over on THT right now with 8 250's on the back.

[bigshrimpin]

Here's another . . . I thought max hull speed only applied to displacement hulls. I'm probably wrong but I know once you reach a certain speed . . . the power required to push the boat each additional MPH increases exponentially.

[bigshrimpin]

My dad had a 1969 johnson 55hp too on the back of a 17ft arrowglass. That motor had a green mid section a white cowling and roared like a nest of mad hornets.

[reelapeelin]

Originally Posted by bigshrimpin

Here's another . . . I thought max hull speed only applied to displacement hulls. I'm probably wrong but I know once you reach a certain speed . . . the power required to push the boat each additional MPH increases exponentially.

Don't remember the ratio, but remember hearin' same thing about cars...once to 100 mph, takes 10 additional HP to increase 1MPH...or somethin' like that...


...an' I'm not sure I buy into a hull having a "Max Speed"...maybe max EFFICIENT speed...but let's say a given hull speed maxes out w/ 150 hp and you strap on a jet engine ... I think it's gonna out run the 150 ;) ...

[randlemanboater]

I know when I got my Starcraft/140 combo, I tried several different props. *I could make the holeshot better or worse, change the RPM at WOT and throughout the range, but the boat would go 43mph (gps) no matter what prop was used. *I can see why it wont go faster, with all those rivits sticking out of the bottom.

Now the guy that had the boat before me had a 150 Yamaha 2 stroke, he said he got 50 mph. But I dont know how he measured his speed.

[randlemanboater]

Originally Posted by bigshrimpin

Fast or not, this boat scores a bunch of cool points, especially when this picture was taken, early 70's maybe?

The rest of us were being dragged around the lake by a Johnson 55 then.

[Blue_Runner]

I think every hull has a max speed. Its when the boat begins to break apart.