Bluebird K7 Latest

It looks like the paint on the flag here is untouched, yes.

Good evening, let me introduce myself: I'm Neil Sheppard, author of the 2011 book, Donald Campbell Bluebird and the Final Record Attempt. In seeking to understand the demise of Donald Campbell and Bluebird K7 and its context, I believe my book, with the analysis of the crash written by Dr Keith Mitchell, can provide most answers.

Here is a brief summary of our findings, which do not directly contradict some of the previous postings, but may help clear up some misunderstandings that have arisen along the way.

1 At speeds in excess of 310mph, Bluebird K7 was only marginally stable. The additive factors of ground effect and port spar damage were such as to reduce the stability margin further to the point where recovery beyond that speed was impossible once moderating engine thrust was lost or reduced. Episodes of ‘hovering’ on the last runs have been identified and, indeed, confirmed throughout Bluebird’s operational life.
2 The hoped-for stability benefits of a further forward CG resulting from the Orpheus conversion were all but lost by the addition of the compensating ballast to facilitate planing.
3 The angle of the wedges incorporated as part of the original design brief to obtain 250mph were suboptimal for speeds above that and contributed to the additional drag experienced.
4 The strident ‘rooster-tail’ spray pattern, evident in smooth or rough running conditions implies that Bluebird was near or at its dynamic stability limit.
5 The first run on 4 January was not without incident as has been generally claimed but demonstrated evidence of instability at the climax of that run and catastrophe was only narrowly averted.
6 Application of the water-brake following the first run was less efficacious than that predicted in earlier lower speed runs due to dynamic instability / rear shoe ‘hop’.
7. Campbell used ‘sighting lines’ off K7’s sponsons to aid his positioning on the lake. He also proceeded far deeper into the southern bay of Coniston than has been previously appreciated. The separation / divergence of the tracks on the first and final runs has also been confirmed.
8. The ‘bouncing’ phenomena observed on the final run are physically distinct to that of ‘tramping’ as they have a different cyclic frequency and form. Tramping was only observed to occur on the initial run-up from Peel Island and played no part in the critical stages i.e. from point ‘A’. The water conditions over the central part of the lake including that of the timed km were good.
9. The speed profile of the latter part of the final run reveals a serious decelerating episode following bounce ‘3’.
10 Engine failure has been confirmed at around 7 seconds prior to impact
11 No evidence can be found to indicate that the water brake was deployed in the final seconds.
12. It is asserted that Donald Campbell’s strategy on the final runs was to exploit the benefits of a quick turn-round given the good conditions of the water and his knowledge of how K7 itself disturbed the water during such runs. This approach was not unprecedented as he had exploited it on various previous runs.

The Gnat tail fin produced less drag than the previous fin K7 was equipped with from 1958 to July 1966.

Our book was written with the direct involvement of Mr AE James - project manager of the K7 refit and Prof. John Stollery, Professor of Aerodynamics at Imperial College and consultant aerodynamicist to the Campbell / Norris team.

I would recommend Keith analysis to all our are interested in understanding the dynamics of Bluebird K7 and the events of those last two runs made by Donald Campbell.

I shall!

Thank you for taking the time to answer.

Bit harsh?

The centre of pressure of that drag, however, is higher up (creating a larger nose-up moment around the craft's CoG). It's not the drag that matters, it's the moment.

I'm uncomfortable with the statement that tramping played no part in the critical stages. Even if the tramping had ceased (as it would of course, once the front planing shoes had lost meaningful contact with the water) by the time she passed the point of no return, it had already made a critical contribution to the pitch attitude of the boat. In plain English: once she'd started to pitch up, she tended to stay pitched up because there wasn't a whole lot to bring her back down. The only thing causing a nose down pitching moment was that part of the rear of the boat that was in contact with the water (the rear planing shoe and rudder), and that wasn't enough.

If you watch the film, she's tramping very noticeably (visibily rocking side to side) up until at most 3 seconds before she clearly passed the point of no return, so it would have taken some decisive dynamic factor in those few seconds to pull the nose back down, to overcome the harm that the tramping had already caused.

It's worth saying that, here in the UK, we tend to obsess about Bluebird's crash in isolation as though it was a unique, profound and unprecedented occurrence. If you spend any time watching American Unlimited Hydroplane racing (and I recommend that you do - it's quite an exciting sport to watch), you'll learn that 'blowovers' are relatively commonplace*, and you'll quickly learn to much more clearly read the signs from roostertails and the tramping/pitching movements of the boats that tell you things are getting out of hand. Having driven (much slower!) inboard-engined three-point hydroplanes in my youth, I can also tell you that once they start to 'hover' or 'float', there's not a whole lot you can do to stop them, other than to gently ease off and hope it sorts itself out**. The American Unlimited hydroplanes now have driver controlled front canards that give the driver a small amount of control, but such adjustable aerodynamic control surfaces used to be banned by the UIM.

I'd also say (having been through the same process myself) that it's easy to over-analyse film, beyond the resolution of its frame speed. You cannot fill the gaps between the individual frames, and it's particularly easy to be misled by cyclical motions (in the same way that the frame rate of a film will sometimes appear to make an aircraft propeller or wheel rotate backwards, or stand still, when in fact it's rotating forwards at many cycles per second). The film of John Cobb's crash in Crusader is a good example of this: from the film itself, you'd conclude that Crusader was pitching at a fairly slow rate, in terms of cycles per second. Because in that instance (and in contrast to Campbell's crash) we could see Cobbs head being thrown back and forth as he sat in the cockpit (with the motion of his head out of sync with the apparent pitching cycles, because of course it was accelerating and decelerating independently of the structure of the boat), it has been concluded that the pitching was actually occuring at a much higher frequency than the film suggested.

Because of all of the above, I'm afraid I'm somewhat sceptical of these sorts of 'expert' analyses: the very fact of wanting to present themselves as 'expert' means that very few are willing to say: 'actually, we don't know, because the evidence simply isn't good enough to reach a clear conclusion'. All we can say is that there were very probably a number of contributory factors, but if we try to pin their relative importance down too far, we're kidding ourselves. Sadly, such a conclusion doesn't sell books!


* and these days, now we have safety cockpits, fairly survivable: one of the characteristics of a 'blowover' is that, by definition, at some point in the loop (usually twice, in fact) the craft is presenting its whole plan area to the direction of travel, which results in enough drag to slow it down appreciably before it impacts the water. The damage is often quite limited, and on some freak occasions the boats actually manage to complete a near perfect loop, touch down and carry on almost as if nothing has happened.

** and even that would be less effective with a jet boat: with a prop-driven hydroplane, you rely on the drag of the slowing propeller to cause a nose-down moment to pull you back onto the water.

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

The record was once held by a hydrofoil (Alexander Graham Bell's 'Hydrodome', at 70mph):



The Norris brothers - who designed Bluebird K7- also designed a jet hydrofoil called White Hawk (note the similar 'fuselage' design to K7), but it failed miserably:





A certain Noel Edmonds was also conned into parting with large sums of money on an absurd design called 'Excalibur' that proposed a propeller-driven underwater unit that lifted the main hull clear of the water using hydrofoils (utter nonsense: the drag of the underwater unit would have been phenomenal). This shows the mock-up (the underwater unit with its hydrofoils is in the background and would have been joined to the cockpit section like the keel of a sailing boat):



If you Google 'Noel Edmonds Excalibur' you'll find a picture of Edmonds with a model, which makes more sense, but it's got Alamy copyright stamps all over it, so I'd better not link the image directly.

The problem with hydrofoils is that you get 'cavitation' on the upper (suction) surface of the foil section. Above a certain speed (typically 70+mph) the pressure becomes so low that a vapour bubble forms over the top surface, so you end up only getting lift from the lower surface of the foil: effectively the same as you'd get from a normal planing surface, but you're dragging along all the useless, turbulent flow over the top surface as well. People have dabbled with 'supercavitating' foil designs (basically a wedge section - similar to the sections you use for a supercavitating propeller) which raise the upper speed limit a bit further, but even they won't work much above 100mph.

I'm uncomfortable getting into debate with a party that does not identify themselves I'm afraid.

With regards to tramping, that on K7 was at about 5-6 hz per second. The bouncing exhibited by in the K7 before it took off was a totally different phenomena, at around 0.8hz per second and should not be referred to as tramping.

K7 was also equipped with a fixed stabilising fin at the transom.

Have you read the analysis? I believe you would find it informative. I'm not saying it has all the answers, but I am saying, and various experienced individuals have agreed, that it does substantially inform the debate about DMC tragic accident.

By all means visit my Facebook page https://www.facebook.com/bluebirdk7 and DM if you would like to correspond further on this.

Here is an image of the second bounce that lasted 0.5 seconds. It was followed by 3 more bouncing episodes before the bows of K7 left the water for the last time. At this point the engine is still lit.

My website is on my profile; you can identify me easily enough from there, if you wish, though I struggle to see why you consider it important: either an argument is supportable or it isn't.

Bill Smith once convinced himself on here that I was Jim Noone, which I found hysterically funny.

None of which I dispute (though as I have said, you should be wary of trying to accurately assess the frequency of an oscillation when your source data itself only has a very limited bandwidth... that's a lesson I've learned by much broader analyses than just the film of one specific accident).

I'm simply saying that the fact that she was no longer tramping immediately before she took off is not to say that the tramping that had occurred prior to that had had no effect on her stability, or did not affect the outcome.

Yes.

I've read lots of analyses of the accident, each of them by someone who had doubtless convinced himself that his was the best and most informative possible.

All of them, in my opinion, over-extrapolate the available evidence and reach conclusions that present themselves as less speculative than they really are... but I appreciate that's the nature of the game. As I said, you don't sell books by admitting that you don't really have the answers.

As Jordie Barretts Sock has said, whether you like it or not, PistonHeads is one of them.

In fact, we have specific rules (4 and 7) that prohibit individual members sharing their own personal information - even if they want to - or from trying to determine the identity of others.

If you don't like that, I can only suggest that you stick to other social media platforms: you signed up to the rules of this one when you created your profile.