Bluebird K7 Latest

[Equus]

dhutch said:

I believe its against rules, but in a way it is surprising they didn't have a flap or two on the front that you could engage during deceleration.

That was at least partly the intention of the water brake that they fitted for the '66/'67 attempt: apart from slowing the boat down, because it was 'pulling' (dragging) from a point on the transom that was below the CoG, it theoretically caused a nose-down moment in operation.

It's a valid solution for a record breaker, where the thrust of the engine tends to pitch the nose down, so you only need an alternative when you kill the throttle... less so for an Unlimited circuit racer, where you don't necessarily want whatever is stopping your nose from pitching up to also slow the boat down, and you don't want to chew the water up more than necessary for the boats that are following you.

In fact, whereas controllable canards are now allowed on Unlimited hydros, water brakes ('devices that cause excessive spray') are specifically banned.

K7 had previously tried using a braking parachute, too, but it wasn't a great success (Arfon's Rain-x Challenger also used a drag chute - you can see it being deployed on the video I linked, above, but it was fired too late to save him).

Edited by Equus on Tuesday 16th April 11:34

[dhutch]

Equus said:

AW111 said:

I assume there's some rule-based reason WSR craft aren't true hydrofoils?

Nope. You're welcome to use hydrofoils if you think you can make one work.

I expect the issue is that, while they work very nicely at 40mph and in choppy water, at 300mph you just have far to much wetted surface.

A three-point hydroplane is half way to being an aeroplane!

[dhutch]

Equus said:

That was at least partly the intention of the water brake that they fitted for the '66/'67 attempt: apart from slowing the boat down, because it was 'pulling' (dragging) from a point on the transom that was below the CoG, it theoretically caused a nose-down moment in operation.

It's a valid solution for a record breaker, where the thrust of the engine tends to pitch the nose down, so you only need an alternative when you kill the throttle... less so for an Unlimited circuit racer, where you don't necessarily want whatever is stopping your nose from pitching up to also slow the boat down, and you don't want to chew the water up more than necessary for the boats that are following you.

In fact, whereas controllable canards are now allowed on Unlimited hydros, water brakes ('devices that cause excessive spray') are specifically banned.

K7 had previously tried using a braking parachute, too, but it wasn't a great success (Arfon's Rain-x Challenger also used a drag chute - you can see it being deployed on the video I linked, above, but it was fired too late to save him).

Fair.

[Equus]

dhutch said:

I expect the issue is that, while they work very nicely at 40mph and in choppy water, at 300mph you just have far to much wetted surface.

A three-point hydroplane is half way to being an aeroplane!

Nope. The issue is as I stated above: they cavitate and lose most of their lift and efficiency at speeds much above 70mph.

Boeing did a lot of work for the US navy, trying to make them practical for high-speed patrol boats, and simply couldn't overcome that limitation.

ETA: I'm struggling to find a link for confirmation, but my recollection from the days when we relied on books rather than Google is that the highest speed Boeing managed was a fraction over 100mph before an accident terminated the programme.

They built a testbed called FRESH-1 to specifically test different foil configurations: LINK

You can bet your life that if Boeing and the US defense budget can't make them go any faster, nobody else will, either!

Edited by Equus on Tuesday 16th April 11:10

[AW111]

Equus said:

dhutch said:

I expect the issue is that, while they work very nicely at 40mph and in choppy water, at 300mph you just have far to much wetted surface.

A three-point hydroplane is half way to being an aeroplane!

Nope. The issue is as I stated above: they cavitate and lose most of their lift and efficiency at speeds much above 70mph.

Boeing did a lot of work for the US navy, trying to make them practical for high-speed patrol boats, and simply couldn't overcome that limitation.

I can also see potential thrust line issues, with the majority of the drag being below the surface.

[Equus]

AW111 said:

I can also see potential thrust line issues, with the majority of the drag being below the surface.

In theory, if you could make them work, then you can counterbalance the nose-down moment from a thrust line above the surface, simply by generating more lift from the front set of foils than the rear.

We've obviously got sailing foils these days (including the Americas Cup boats) that are pushed/pulled along by sails that act well above the CoG.

...but the truth is that (although the Boeing testbed was jet propelled), you actually can't make them fast enough to really warrant jet propulsion, anyway: at the speeds they have managed, conventional immersed propellers are more efficient.

[Equus]

If we're doing weird and wacky ideas, here's one for you:

Russian supercavitating torpedos use hydro-ramjets fueled by hydro-reactive metals and have achieved speeds in excess of 230mph.

Maybe Noel Edmond's 'Excalibur' project wasn't as nuts as it seemed... he just needed to team up with Mr. Putin.

[sheppane]

dhutch said:

Equus said:

That was at least partly the intention of the water brake that they fitted for the '66/'67 attempt: apart from slowing the boat down, because it was 'pulling' (dragging) from a point on the transom that was below the CoG, it theoretically caused a nose-down moment in operation.

It's a valid solution for a record breaker, where the thrust of the engine tends to pitch the nose down, so you only need an alternative when you kill the throttle... less so for an Unlimited circuit racer, where you don't necessarily want whatever is stopping your nose from pitching up to also slow the boat down, and you don't want to chew the water up more than necessary for the boats that are following you.

In fact, whereas controllable canards are now allowed on Unlimited hydros, water brakes ('devices that cause excessive spray') are specifically banned.

K7 had previously tried using a braking parachute, too, but it wasn't a great success (Arfon's Rain-x Challenger also used a drag chute - you can see it being deployed on the video I linked, above, but it was fired too late to save him).

Fair.

The water brake on K7 was not designed to be used at a speed higher than 250mph. It also was not as constantly efficient as first hoped when trialed. Campbell used the water brake above 200mph on the trial runs of the 12th and 13th of December and it worked well. On these occasions the max speed K7 reached was 260 mph. It also reportedly worked well on the Christmas Day run, again from about a 270 peak. The 1st run on the 4th of January, it was used but our analysis suggests that the rear planing wedge hop that K7 suffered from on that run meant that it was not as efficient in slowing the boat down. It is therefore a moot point what the effect would have been if Campbell had engaged it as a last ditch attempt to avert disaster.

Here is an image of its successful deployment on the 13th December. You can apprecaite the enormous cataract of spray that results from deployment. This was not witnessed on the 4th after the first pass through the kilo.

[Eric Mc]

Equus said:

Maybe Noel Edmond's 'Excalibur' project wasn't as nuts as it seemed... he just needed to team up with Mr. Putin.

Hmm - if only Mr Blobby was dictator of Russia.

[AW111]

Equus said:

If we're doing weird and wacky ideas, here's one for you:

Russian supercavitating torpedos use hydro-ramjets fueled by hydro-reactive metals and have achieved speeds in excess of 230mph.

Maybe Noel Edmond's 'Excalibur' project wasn't as nuts as it seemed... he just needed to team up with Mr. Putin.

So technically could you do a WWSR fully submerged?

[Jordie Barretts sock]

Yes, I made many attempts when learning to waterski.

[Gary C]

Is fully active aero not allowed on a LSR car ?

All you would need is a cruise missile with some dangling wheels and a cockpit.

Of course a technical cruise is subsonic so would need a bit of a boost

Edited by Gary C on Tuesday 16th April 12:06

[Equus]

AW111 said:

So technically could you do a WWSR fully submerged?

Timekeeping might be a problem.

Perhaps you could tow a 'marker' above water to give the timekeeping system something to sight on? Maybe a rubber duck on waterskis, just for comedy value?

[sheppane]

Not sure Excalibur achieved much apart from making Mr Edmunds wallet about £40k lighter curtesy of a Mr Basil Wainright, who was behind the idea. When asked about it a few years ago, Edmond's didn't want to talk about it.

[Equus]

Gary C said:

Is fully active aero not allowed on a LSR car ?

All you would need is a cruise missile with some dangling wheels and a cockpit.

Dunno about the LSR - it's not something I've taken a particular interest in, but the UIM defines a 'boat' as '...a vessel that floats on the water when stationary and continuously derives support, directional control or propulsive effort from hydrodynamic forces' (my bold).

You only need one of the three, so you can run a jet or rocket vehicle in close ground effect so long as it derives directional control from hydrodynamic forces. I checked this with them for my design, back in the '80's, so I know it to be correct.

It also means of course, that you could effectively tow an aircraft behind some sort of 'tug' unit that derived only its propulsive effort from hydrodynamic forces (...so we're back to Russian hydro-ramjets ).




But enough of this silliness... Sheppane will think we're not taking his hero seriously!

[Equus]

sheppane said:

When asked about it a few years ago, Edmond's didn't want to talk about it.

Hardly surprising!

Wainwright was a very convincing con-man, mind you: I remember the mainstream press and media (Autocar and Motor magazines, and Tomorrow's World on the BBC, if I remember correctly) falling for his 'Butterfly' engine, which could apparently do 148mpg.

He later claimed to have found a cure for AIDS ( I kid you not)

[Equus]

Gary C said:

Is fully active aero not allowed on a LSR car?

In a serious response to your question (but again relating to boats), the UIM now has a rule:

UIM Rule 504.14 said:

All moveable surfaces allowed on the boat shall be under the control of the onboard crew without any sensors in
the control loop (i.e. no auto pilots, auto trims, gyros, accelerometers or other attitude or acceleration sensors may
be in the control system).

So for the WWSR, at least, fully active anything is now banned. I'm guessing that's at least part of the reason that the canards on current Unlimited Hydroplanes are driver controlled, by a pedal in the cockpit.

[hidetheelephants]

Equus said:

If we're doing weird and wacky ideas, here's one for you:

Russian supercavitating torpedos use hydro-ramjets fueled by hydro-reactive metals and have achieved speeds in excess of 230mph.

Maybe Noel Edmond's 'Excalibur' project wasn't as nuts as it seemed... he just needed to team up with Mr. Putin.

The Skvaal underwater rockety thing does raise the question; did Boeing just not get wacky enough? Perhaps the next water speed record holder needs to be developed from a really rubbish but very fast torpedo.

[Gary C]

Equus said:

Gary C said:

Is fully active aero not allowed on a LSR car?

In a serious response to your question (but again relating to boats), the UIM now has a rule:

UIM Rule 504.14 said:

All moveable surfaces allowed on the boat shall be under the control of the onboard crew without any sensors in
the control loop (i.e. no auto pilots, auto trims, gyros, accelerometers or other attitude or acceleration sensors may
be in the control system).

So for the WWSR, at least, fully active anything is now banned. I'm guessing that's at least part of the reason that the canards on current Unlimited Hydroplanes are driver controlled, by a pedal in the cockpit.

Crikey. Really old school

[Equus]

Gary C said:

Crikey. Really old school

Yes, but not really more so than the FIA, which AFAIK still ban both active aero and active suspension on racing cars (despite both now being commonplace on road cars)?

It does belie the myth that these sorts of projects lead to advances in engineering knowledge, though.