Forced air ventilated stepped hull?
 

Anyone know the story behind this boat? photo gallery



In this pic it appears to have some sort of forced air hull ventilation

Re: Forced air ventilated stepped hull?
 

I have been considering an air pressure system under a stepped hull myself. Theoretically, it should decrease wet area, reducing friction, and increasing performance. I know it will work. But, how much pressure, where the openings should be, their size and shape would have to be engineered. With 65 OSO views and only my reply since the 16th, it doesn't look like too many people know much about air under hulls, or they just have'nt seen your thread. Hovercrafts have been doing it forever.

If you've learned anything new since your post, please let me know. There must be knowlegeable people out there on the subject. Tony [email protected]

Re: Forced air ventilated stepped hull?
 

Firt off I know jack sh!t about this boat or anything to do with forced air hulls. That said it looks like a cool concept but will it be faster or not is the question. You need to build 2 hulls identicaly and test.

It looks to me like the intakes on the bow are connected to a system of ducts layed up in the mold. The air is then forced through the ducts simply by the speed of the boat. Just my guess. Air pumps would add huge weight.

Re: Forced air ventilated stepped hull?
 

Hallett has already been doing this on some of their stepped boats. The way I understand it it is not really forced air as much as a venturi effect of the suction behind the step drawing the air through the tubes layed up in the hull. The intakes can be on the sides above the steps. This also breaks of the vacuum sucking the hull down. This is possible more of a problem on single engine boats that have high prop torque and tend to lean to the torque side already. My understanding is the ventilated steps are faster than the nonventilated. I've seen this in person at the lake and it really is a pretty simple concept to incorporate while laying up in the mold.

Re: Forced air ventilated stepped hull?
 

We talked about this back in the early nineties when we were racing offshore. We raced an open cockpit conventional vee hull. I was the tallest member of the team and buffeted the hardest by the wind. My thought was to induct air from the deck at the base of the fairing, route down thru the forward cockpit bulkhead and out the bottom at the deepest part of the vee (keel). Our thinking was this would help reduce turbulence (resistance) in the cockpit and aerate the bottom of the hull. Unfortunately we destroyed the boat in Key West before we were able to test our theory.

Re: Forced air ventilated stepped hull?
 

Ask Tim Sharkey on this forum for information. He knows the boat and it's builder.

Re: Forced air ventilated stepped hull?
 

Outerlimits has been doing it for a few years now.

Re: Forced air ventilated stepped hull?
 

I saw a 50' Delta conic hull, made in europe. Looked kind of like an canopied infinity deck on a delta conic sigle step hull.At the single step it had large ventialated holes in the vertical section of the step.
Forced air was introduced fromj the exhaust of the 3 turbo diesels that powered it. My understanding is that it was not too sucessful since the bare hull was offered to me for under $10K.
Gary

Re: Forced air ventilated stepped hull?
 

If seen a few diesel powered boats where they designed a venturi for the exhaust. The the boat is underway the exhaust is being sucked out of the motor. On the boat that I saw tested it picked up a couple MPH in a 40 ft Trawler.

Re: Forced air ventilated stepped hull?
 

Diesel soot pumped under the hull. That should be nice looking after a long run.

Re: Forced air ventilated stepped hull?
 

I think the next step after steps is to go to a hydrofoil design....get everything up and out of the water but the sponsons and the prop...

Re: Forced air ventilated stepped hull?
 

That boat has been on the board before. There is a massive thread with build pics. I thought that some of the pics were posted by AudioFn.

Re: Forced air ventilated stepped hull?
 

The big open ducts at the bow look little scary if ever it even came close to a stuff. I've come plowing thru rollers at the mouth of a river and had water plowing right up to the rub rail - have that pressure hit the vents at speed would act like a hydro brake - no?

Re: Forced air ventilated stepped hull?
 

Panther makes a good point about Outer Limits. I've seen what they've done.

Re: Forced air ventilated stepped hull?
 

Gary

Let me know if that 50' Delta Conic hull is still available, and if you have any pictures, I'd really like to see them. That Delta. Conic hull is a remarkable design. It was the star attraction at the Miami Beach boat show back around 1980 when I was there. It's debute was on a 9 meter Trojan Express. I know why it didn't work. Delta Conic hulls cannot be stepped, as they loose stability, and completely destroy the design properties and characteristics that the Delta Conic shape was made for. Anyway, it's nice to see that you, and a lot of other OSO people know something about ventilated hulls, and have finally joined this thread discusion. Tony

[email protected]

Re: Forced air ventilated stepped hull?
 

Hasn't there been some Fountains with somewhat the same concept?

Vent ports in the step, with the tubes other end in the engine compartment. Not quite a forced air setup though.

Re: Forced air ventilated stepped hull?
 

was it Extreme that had this system on one of there boats a few years ago?
i remember seeing some pics .

Re: Forced air ventilated stepped hull?
 

My guess is there is huge potential effiency gains for v-hull given the proper method of ventilation. That boat looks like they might have it figured out. I'd love to see a shootout done by a reputable magazine where they test many hulls all pushed by a bone stock (verified by Merc) 496HO.

My thoughts were to mold the step into the hull and not put the vents thru it. Rather come in afterwards with some stainless steel tubing that could be easily replaced. That would allow one to experiment with different hole spacing, size, etc. without having to make a new hull or majorly rework it. The tube running transverse to the boat in the root of the step could be bolted on and off in a matter of minutes if the rig was on a custom trailer to allow access.

For each configuration of the tube (hole size, spacing, etc.) one would supply a range of air pressues (and therefore flows) and record data on the results. So, you would have a 3D performance map of hole size+spacing vs pressure vs performance (top speed).

Now, I just need the $$$ and time to modify a hull to run these tests!

Re: Forced air ventilated stepped hull?
 

I'm an inventor, have a few patents, sold a few, but have used all my profits to live on and try-out new ideas. It cost's money to perfect a new idea, or an old idea, that a lot of people had, but didn't do anything with. But I will tell you something...if you have a gut feeling about something, and...if you put your whole heart and time into it....IT WILL PAY OFF.
Beleive me...I've done it.

It took 3-Canadians from Toronto 6 YEARS to perfect the most sought after game ever, TRIVIAL PUSUIT. One of them had a heart attack, and the other two, went to Mexico for six months, and laid on the beach to relax, concentrate, and come up with the remaining 3,000 questions and answers that they needed to make the game work. Today, they are each worth about $100,000,000. There's a movie all about how they did it. Maybee some of you at OSO have seen it. It's a true success story.

I have a design for the PERFECT VENTILATED STEPPED HULL! If anyone's interested, please let me know. Tony

[email protected]

Re: Forced air ventilated stepped hull?
 

I find that...very hard to believe. When air is induced under a platform (hull), it acts like a hoovercraft...there's no fiction, except for air...not like the wet surface of water. THERE HAS TO BE...a significent increase in speed.

Re: Forced air ventilated stepped hull?
 

I would thing that racing offshore through large (6'+) rollers would be totally different than a lake boat - even a rough lake like LOTO.

Things that work best for a personal fast powerboat might not be the best compromise to a racer on big water.

For me, I'm thinking lake boat - one that could hand the LOTO channel on a July 4th weekend.

Re: Forced air ventilated stepped hull?
 

Winning a race with two identical boats, (except that one is ventilated and the other isin't), doesn't prove anything, except that the crew of the winner, the propellers, the wind and wave conditions, all contributed to who won and who lost.

The only way to prove that ventillation is better, is to run two identical boats (in every way), 100' apart, on a course, and record performace thruout the endurance of the run. Then you have to do that again, 2-more times, and average them out. Tony

Re: Forced air ventilated stepped hull?
 

That hull was built by Jack Domic at hydra power poats in Toms river NJ. It was rigged by its owner with a single crate Hemi motor. Last I had heard it was running in the mid to upper 80s

Re: Forced air ventilated stepped hull?
 

Thanks for the info...and if you know where I might get some photos, please let me know. Tony

Re: Forced air ventilated stepped hull?
 

"When air is induced under a platform (hull), it acts like a hoovercraft"

not the same...an engine supplies the thrust in this application. along with other important designs characteristics.

reducing surface tension and inducing air are different.

you can not have a 'forced air' system if you vent it to atmosphere...this will = NO pressure and NO lift!

Re: Forced air ventilated stepped hull?
 

If that's true...I wonder why so many boat manufacturers are using this principle...just look at the other replies to this thread....and all the boat names...like Donzi for example.

Re: Forced air ventilated stepped hull?
 

Not many more people have spent more time than me under a donzi??? i must have missed the holes!

i guess i need to mount a huge funnel on the bow with a hose going to the bottom....LOL

Re: Forced air ventilated stepped hull?
 

When a boat is 'up and running' it doesn't require any additional ventilation. Only when the step is submerged is it of any value. We used a drilled tube as the rear frame on the steps of the aluminum Cougars, but just to break the suction getting on plane. When the outboard edge of the step clears the water, the step is naturally ventilated.

Re: Forced air ventilated stepped hull?
 

Actually...I didn't think Donzis used ventilation either...it's just what I've read on OSO chat lines. Either people are making up stories...or maybeee...some were built with ventilation. I personally... have never seen them on any. Who knows....?

And yes...ventillation is only effective... from a dead start to just past planning speed. You'll get on plane at about one third the normal time it usually takes. And in a race...that would get you in the lead...out of wakes...and a better chance at winning.

Re: Forced air ventilated stepped hull?
 

who cares about getting on plane. In a race you start at about 70 mph or better...

Re: Forced air ventilated stepped hull?
 

Got a little mixed up there...was thinking of a drag boat race. Guess I'm not getting enough sleep.......ZZZZZZ

Re: Forced air ventilated stepped hull?
 

Challenger, yes the GL,T2x Challenger used ventilation ports on their 21 v back in the 80's. Didn't seem to do much.

Re: Forced air ventilated stepped hull?
 

I've got an idea for a ventalated hull that doesn't require steps but does the same job because it's not the steps that do the work, it's the air bubles under the hull that reduce the friction.

I'm not an engineer so who knows if it would work but a flat bottom boat could be easily re-configured to do a side by side test.

Design would be a derivative of a standard bottom boat but would have air holes underneath, the bottom would look something like this;

Re: Forced air ventilated stepped hull?
 

I was thinking along the same lines a while back....but wondered where to get the air from...and if it had to be pressurized with an air pump or compressor. I'm still waiting for my membership to be posted....so I can get those images..probably 2 or 3 more days.

Re: Forced air ventilated stepped hull?
 

Airpacker....just wondered if I could get any pictures or information on how Challenger did it.....as I'm still convinced that a ventillated hull would have better performance....just don't think that they were doing it right...it has to be perfected.

Re: Forced air ventilated stepped hull?
 

It wouldn't need an airpump, the air would be sucked thru vents located on the deck while moving at speed.

Re: Forced air ventilated stepped hull?
 

"It wouldn't need an airpump, the air would be sucked thru vents located on the deck while moving at speed."

you serious?...physics will not allow this.

EVEN if you had a ducked fan/air pump.....the air is GOING to the path of least resistance....which would be ANY one of the holes exposed to atmosphere and NOT the one under the water where (in your theoretical design) needed.

Re: Forced air ventilated stepped hull?
 

i think i (we) may hold records for a number of unmentionables!LOL

Re: Forced air ventilated stepped hull?
 

I guess you're a physics major then... :rolleyes:

Have you ever stuck your hand over top of the NACA ducts on the deck of an Outerlimits while under way?

If the holes were designed right with the proper leading and following edges, it would indeed suck air.

Re: Forced air ventilated stepped hull?
 

the holes would be desinged like this and the leading edge would be slightly raised (area shaded in black with arrow) which would create a vacuum as the water passes underneath.

That's my summation :rolleyes: