Hydro Blowover Accidents

[Bito]

Hello,
I wanted to know if there has been any formal research done on the subject of blowover accidents of high speed boats.

[FranklinRatliff]

Originally Posted by Bito

Hello,
I wanted to know if there has been any formal research done on the subject of blowover accidents of high speed boats.

A lot of wind tunnel and aero testing has been done on Unlimited (Gold Cup) hydroplanes. For many years now these boats have incorporated driver-controlled canard wings to temper blowover tendencies.

http://www.missmadison.com/photos/St...oming%20In.jpg

http://www.missmadison.com/photos/madison07032004/3.jpg

http://www.missmadison.com/photos/ma...7032004/55.jpg

I'm not aware of much similar research being done on the big offshore tunnel-type hulls.

[Bito]

Has any of that research been published?

[FranklinRatliff]

It is my impression it has been published but I couldn't tell you in what journal.

[Ike]

I imagine it has been published because I can remember reading about blow over somewhere. Back in 1978 I investigated three blowever accidents involving Hydrostream boats all of which were traveling at between 90 and 100 mph when the blowover occured. Four people died (one boat had two people in it). It's all in the aerodynamics. Essentially the whole boat is an airfoil that is from time to time touching the water. On a hydroplane it can be two or three points and on a single hull boats it's only one point and may be as little as 6 square inches. So the angle of attack of the foil (the hull)becomes critical. If the angle of attack exceeds a certain amount (varies from boat to boat) you get excess lift and the boat blows over. In some cases it actually lifts completely off the water and flies a short distance as it flips. I have seen film of hydroplanes actually blowing completely over and coming back down in an upright attitude. Of course it is not what anyone would call a soft landing.

The same thing happens to Flare craft. These are essentially aircraft that fly, just off the surface of the water, a few inches to a few feet. If the angle of attack becomes to0 great they blowover. I have seen a video of one that exceed it's angle of attack went straight up about 100 feet in a loop and then dove into water.

So on hyroplanes they used wings on the stern, mounted on vertical stabilizersl (like the stabilizers on an FA-18 fighter jet) that are controllable so that they can control the angle of attack. These are now computer controlled and blow overs have decreased in the unlimited races. On many of the hydros they now have pickle fork bows and the mount a litle wing between them as well to control the angle of attack. In smaller hydros and in drag boat and other races you still see them frequently especially in HOT BOAT magazine. They love to publish photos of this.

If you look at the Unlimited Light Hydrolane Racing Assoc site you see these little wings on the bow http://www.ulhra.org/ or on Unlimiteds.net http://unlimiteds.net/

[Bito]

I am looking for a graduate thesis topic and I thought that investigating blowovers would be an interesting project to do some CFD and wind tunnel tests on. Is this a topic that I should continue on, or has the solution already been reached with the wings? Is there a calling for this research for any specific boat types?

[Ike]

I would think that is a question best posed to the people who would benefit the most, the racing community. Maybe the American Power Boat Association would be the right group to ask. try http://www.apba-racing.com/index.html

[Goanna]

I understand that Georgia Tech did a lot of work on this problem and probably still are active in the field. They were also working on the problem of blow-overs for Le Mans cars. Mercedes Benz had two blow-over incidents at Le Mans a few years back. Sliding down the track on the roof at 200 mph is not considered good form!

Best of luck with your research and your thesis.

Regards

Gerald

[Bito]

I contacted APBA and I'm waiting for a response from their safety director

[FranklinRatliff]

Originally Posted by Bito

I am looking for a graduate thesis topic and I thought that investigating blowovers would be an interesting project to do some CFD and wind tunnel tests on. Is this a topic that I should continue on, or has the solution already been reached with the wings? Is there a calling for this research for any specific boat types?

As far as aerodynamics are concerned, the big offshore tunnel hulls are still in the stone age.