thanks for the tunnnel boat article

[David]

https://www.screamandfly.com/content.php

Very cool article. Thanks

I have a follow up question about V bottom boats. Where does the lift come from in a fast V bottom like the one in the picture. Can a V bottom get as much lift from the air as a tunnel? There is not much boat touching the water in the picture, so I'd think the water drag would not be more then in a tunnel. Or is the gearcase providing more lift, and therefore more drag, then in a tunnel?

[David - WI]

There's a v-hull article by Jim Russell here... there is a link on the page to request the full article by e-mail.

https://www.aeromarineresearch.com/p...y_Nov2013.html

[FUJIMO]

[Jimboat]

https://www.screamandfly.com/content.php

Very cool article. Thanks

I have a follow up question about V bottom boats. Where does the lift come from in a fast V bottom like the one in the picture. Can a V bottom get as much lift from the air as a tunnel? There is not much boat touching the water in the picture, so I'd think the water drag would not be more then in a tunnel. Or is the gearcase providing more lift, and therefore more drag, then in a tunnel?

David - thanks for the mention. Vee pad hulls, like the Allison in your photo, can be super fast, largely due to the efficient lift gained from a flat center-pad. Vee hulls can certainly be designed to generate aero lift. When a tunnel hull creates more aero lift though, then there is less wetted planing surface needed, so less hydrodynamic drag.

There is an article here on S&F on Vee Pad hulls, and more articles on performance boats here that might be of interest.

[Lake X Kid]

https://www.screamandfly.com/content.php

Very cool article. Thanks

I have a follow up question about V bottom boats. Where does the lift come from in a fast V bottom like the one in the picture. Can a V bottom get as much lift from the air as a tunnel?
There is not much boat touching the water in the picture, so I'd think the water drag would not be more then in a tunnel. Or is the gearcase providing more lift, and therefore more drag, then in a tunnel?

Can a V bottom get as much lift from the air as a tunnel? No.

The high-pressure air escapes up and away from the hull’s deadrise sides. Whereas - a Tunnel hull traps the air and creates a high-pressure for the boat to ride on. Also, some Tunnel hulls upper decks have a convex angle (like airplanes & birds) which create a low-pressure (suction to a degree).

Therefore, an Outboard pushing a Tunnel hull will use less power to get and keep the Tunnel hull above the waterline, than pushing a Vee hull with the same engine size. Thus, propelling the Tunnels and Tri-hulls faster than the Vee hulls.

[Lake X Kid]

Tri Hull riding on the center pad like a Vee hull, but also has a couple of Air Entrapment Chambers for added LIFT.
Whereas the Vee hull does not have the entrapment chambers/tunnels.

[David]

Thanks Jim and Lake X. I will start reading Jim’s links. The STV photo above shows perhaps less wetted area then the Allison picture. Less drag.

[CUDA]

And you can chop the throttle and you won;t make a U turn

Hookers, a friend asked me to drive his new to him Allison fishing skinny version with an old CLE, without added cone,

I had her aired out, too much trim and blowout, we stayed in a straight line, with some wiggles, I turned around and my buddy's eyes

were WIDE open

He didn't keep it long

[powerabout]

dont forget the deck is also part of the aero package once your going fast

[CUDA]

Backing the boat in for a race I was stopped by an official and told to remove my Tonneau cover, I said nothing in the rules that says so...

I found out that Mr. Darris Allison was the one who caused the action

Tommy Dunn my crew chief motor builder who grew up racing Allison's

He said take that as a compliment, He's Scared of your homemade boat.

[David]

Can you chop the throttle in an STV at 90 mph and not get into trouble? I would not try that in my SS2000.

[CUDA]

I've chopped the gas at 115 in a STV ... nothing...

If you have blow out nothing...

Very boring compared to an Allison

Tommy Dunn drove Docc Tripp's MP boat at Jasper after he died and won Mod Production

It was a rough day, and I said you made It look easy,

He said he was working his A$$ off to keep It Straight

Funny story, Doc Tripp was the president of ODBA, and he arranged to have two cops with radar guns at the finish line

On pontoon boats, that was the day Sky Walker hit 141 MPH on nitrous in a 1/4 mile, truly Airborne at the finish line, straight and true

Well I've seen Doc hook his boat testing a few times, But that day he hit the pontoon boat with the two radar Cops on it,

the next day the cop was back , put he had a cast on his knee

Doc's boat almost sank,

[Instigator]

No

Thats an lesson most learn early in STV ownership and I’ve proven it after loosing a gearcase on my STV at 95.

But my buddy who was w/me, both agreed if we had been in my Hydrostream Vector, it probably would have killed us both!

Thx for the reminder to read Jim’s story.

Jim is a friend of mine and I own and read his books when I need to be reminded of how much I DONT know!

On the Vee’s aero package, it depends on hull design and angle of attack.

IMO, w/a pad vee on its pad, @ speed, the more important aspect is reduction of aero drag.

The steeper the angle of attack, the more lift it creates but also increasing drag.
And struggling to punch a larger hole through the wind.

Aero and hydrodamics are a favorite topic of mine.
When I was racing kneel down boats I designed and built several 3 point hydros and one tunnel hull.

They we’re never the fastest but guarantee you that if put in a wind tunnel they would have the lowest coificient of drag ��

BTW, I built the one and only tunnel, unfortunately, many yrs before hearing of Jim’s work/research!

Though it was a flop, it was quite an interesting learning experience.

In the class I raced it, you needed to see mid 60’s between the turns.
But I miscalculated (guessed!) the tunnel aspect and it didn’t build enough lift for the lower speeds.

I was very good at flying a 3-point hydro and never blew one over.
I blew that stupid tunnel boat over 3 times in a yr!

Up to 63 mph, w/my ass as far back in the cockpit as I could get, it ran dead flat.
At 63 1/2 mph, it built lift and before I could react, over it went!

I finally put a 12” blade in my Sawzall, cut in 3 pcs and drug it out to the trash!

The hull/tunnel needed to be 6” longer.

Can you chop the throttle in an STV at 90 mph and not get into trouble? I would not try that in my SS2000.

[kelvin523]

Give this guy big credit; worth the listen, jump to 8m mark...