Donald Campbell's restored Bluebird in museum home row

[Ernie Lazenby]

Keith I always enjoy reading your work and thoughts. I have an open university degree in applied physics required for my work as an accident investigator back in the day dealing with serious and fatal road accidents. Sometimes however theory needs to be put aside to consider something from an uncomplicated straight forward layman's point of view.
1. K7 suffered a hydroplane blow over- many have since and no doubt will again.
2. It blew over because the bows lifted allowing air underneath the front and when that happened nothing was going to stop the blow over.
3. The bows lifted because she was unstable. Going too fast.

That's pretty much the end of it really. K7 may have suffered fuel starvation resulting in loss of power, water brake factor, weight distribution factors or whatever immediately before 3 thus contributing to the end product. Facts 1-3 are what we know and I suspect all we ever know. Experts can theorise producing interesting points for debate, hands on empirical knowledge may help that debate but too many variables gone with the passage of time to be dogmatic in expressing an answer to the crash.. (cog, total weight- weight of sponsons- weight of fuel etc etc- all very relevant factors)

In accident investigation work empirical knowledge gained from hands on experience is every bit as useful as theory, indeed quite often more so, combine the two and hey presto we advance our knowledge but quite often even that combination fails to establish the truth.

BTW I get a little frustrated at some of the personal stuff on here, you are entitled to your opinion and views and its not helpful to read comments like 'self appointed' etc etc. In my work as an investigator I was quite often challenged about my conclusions however was always prepared to change my conclusions when presented with another's more compelling opinion; quite often at court! Having a large ego and being dogmatic does not serve justice well or indeed debate between grown ups.

Finally I have to say if the purpose of this forum is only to massage an ego or ego's it could be said its become irrelevant. Plenty of massaging of late.

[KW Mitchell]

Thanks Ernie - erudite as always. It’s a while since we caught up. Hope you are well...
Keith

[Renegadenemo]

Finally I have to say if the purpose of this forum is only to massage an ego or ego's it could be said its become irrelevant.

I assume that wasn't pointed at me as anyone who has ever worked with us knows of my fanatical insistence that there is no 'I' in 'team', that we succeed or fail as a team and that everything we have achieved has been very much a team effort.

As for the wonderful analysis of the K7 accident, well I have to admit I never got the end of reading it once I discovered that such basic values as the size of the planing wedges were incorrect. Tell me - what size is given for the wedges in the current version? I know it was hopelessly wrong in the first one.

[mtskull]

1. K7 suffered a hydroplane blow over- many have since and no doubt will again.
2. It blew over because the bows lifted allowing air underneath the front and when that happened nothing was going to stop the blow over.
3. The bows lifted because she was unstable. Going too fast.

With respect, if we're going to over-simplify to that extent, then point #1. would suffice on its own.

By definition, a "hydroplane blow over" is what happens when the angle of attack of the bows becomes sufficient to allow aerodynamic lift to overcome the combined downward forces and, because the 3-point hydroplane configuration is inherently unstable in that there is more "wing" area in front of the C of G than behind it, the condition becomes divergent, i.e. more angle of attack = more lift = more angle of attack = more lift until the craft, for want of a better term, "blows over".

K7's bows did not lift because she was unstable; the instability came into play once the bows had lifted to the critical angle of attack.

How, then, did K7 come to be in that divergent condition? Not simply a matter of "going too fast", more like "going too fast when subject to a specific set of unforeseen circumstances". We know that when K7 became airborne it was slowing down from its peak speed and (in theory at least) was being operated close to, but within, the limits of its safe operating envelope, so some other factor or factors must have been in play during the crucial moments. The entire purpose of all the analysis of the accident that has taken place has surely been to determine what these factors were and to what extent each one influenced the outcome.

True, we can never know for certain, but we may better understand.

[KW Mitchell]

Finally I have to say if the purpose of this forum is only to massage an ego or ego's it could be said its become irrelevant.

I assume that wasn't pointed at me as anyone who has ever worked with us knows of my fanatical insistence that there is no 'I' in 'team', that we succeed or fail as a team and that everything we have achieved has been very much a team effort.

As for the wonderful analysis of the K7 accident, well I have to admit I never got the end of reading it once I discovered that such basic values as the size of the planing wedges were incorrect. Tell me - what size is given for the wedges in the current version? I know it was hopelessly wrong in the first one.

Yes, it is incorrect - as Bill pointed out to us after the first edition was published - but chooses to again be quite unfair to me as he does not refer to the reason I gave him for that at the time. In my defence, here it is:

In preparation of my chapter in 2010, I was examining the post-crash analysis document :

'Bluebird Boat - Performance on the Last Run', KW Norris & JL Stollery,
Norris Bro's Report (Job No: D3/323C), 23rd January, 1967.

(This report, previously unpublished, was made available to me by Tony James from his private archive).

In it, Ken Norris states the length of the planes as 57.3" in a calculation to assess critical loadings on the planes at 312mph. I had no other information to go on - and remember at that time the sponsons were long lost and the rebuild had not started - so deferred to the great man's data. Who was I to challenge that? (incidentally, if anyone wishes to peruse a copy of the relevant page in these calculations, I'll be happy to mail such. I sent a copy to Bill at the time...).

I now know the correct length is 72" but I am sure you will forgive me for the error, as it was really not down to me. It will be corrected in a pending rewrite, as others, inevitable in any publication as nothing is perfect. That is why I do not sit happily with the words 'definitive', 'last word' etc., about any publication as refinements can always be made. I am thankful that over the last years since publication people such as the late John Stollery, Ken Wheeler and others have taken time to offer helpful criticism in an honest, but kindly way, so that we can all better understand what happened in those early days of 1967.

[Renegadenemo]

Yes, it is incorrect - as Bill pointed out to us after the first edition was published - but chooses to again be quite unfair to me as he does not refer to the reason I gave him for that at the time.

Erm, no - I flagged it before the book ever went to print but I was told, oh no, we have a Norris Bro's document that says otherwise. Didn't bother me, I only had an actual wedge, which, if you want to be accurate, is actually 72 1/4" along its long side. I also pointed out that the float wedges are not 12" wide at all as they're chamfered towards their trailing edges. And where did all the measurements to two decimal places come from? Another Norris Bro's document? And even if they were anywhere near what is the tolerance? plus or minus what?
And what about all the other significant factors that were flagged and either dismissed or ignored? The left hand side weight bias, for instance? Oh, that's insignificant. Try telling that to the boat when you pick her up with a crane. Or the engine torque reaction that counters her left-side heaviness at high power settings, or the gyroscopic precession that lifts her nose given a right-hand steering input.
The basic errors and lack of research are fine, ignoring very significant factors at the boundary of stability is fine. What isn't fine is using half the story to compile graphs and charts and tables and attempting to sound like an authority on the subject... So keep on adding members to the Oooh, look at the duck damage club, wibbling about floating in ground effect and the doppler effect on the faff-faffing and let our fourth year students do the back to basics engineering because they at least have the humility to say that the best they can ever achieve is an approximation with the data available.

[KW Mitchell]

Yes, it is incorrect - as Bill pointed out to us after the first edition was published - but chooses to again be quite unfair to me as he does not refer to the reason I gave him for that at the time.

Erm, no - I flagged it before the book ever went to print but I was told, oh no, we have a Norris Bro's document that says otherwise. Didn't bother me, I only had an actual wedge, which, if you want to be accurate, is actually 72 1/4" along its long side. I also pointed out that the float wedges are not 12" wide at all as they're chamfered towards their trailing edges. And where did all the measurements to two decimal places come from? Another Norris Bro's document? And even if they were anywhere near what is the tolerance? plus or minus what?
And what about all the other significant factors that were flagged and either dismissed or ignored? The left hand side weight bias, for instance? Oh, that's insignificant. Try telling that to the boat when you pick her up with a crane. Or the engine torque reaction that counters her left-side heaviness at high power settings, or the gyroscopic precession that lifts her nose given a right-hand steering input.
The basic errors and lack of research are fine, ignoring very significant factors at the boundary of stability is fine. What isn't fine is using half the story to compile graphs and charts and tables and attempting to sound like an authority on the subject... So keep on adding members to the Oooh, look at the duck damage club, wibbling about floating in ground effect and the doppler effect on the faff-faffing and let our fourth year students do the back to basics engineering because they at least have the humility to say that the best they can ever achieve is an approximation with the data available.

Sorry, but I must challenge some of the statements made herein. Re' flagging up issues, you did not see drafts prior to publication so could not possibly comment, and, only offered criticism after the book was published, a fact confirmed on the pages of this Forum.

The only issues ever flagged to me - via Neil - as you were not corresponding with me directly, were the aforementioned wedge issue and the asymmetric weight factor.

On the latter, I referred the matter to Tony James who was aware of the additional equipment along the port side of the hull. He said it was insignificant because when the craft was in the water, the corrective moments of the large and relatively heavy sponsons rendered that asymmetric weight effect insignificant. I did a calculation to that effect - which was checked by him - and then passed on to you.

Also, if the effect had been significant, the lateral shift in CG would take it away from the centre of buoyancy, and a list to port would be evident. Tony confirmed that no list was present in '66/'67 and all photographs taken of the craft confirm this. I note that at Bute the boat's lateral trim appeared to be likewise, unaffected.

[ace_chris]

Could it be possible that the maximum safe speed for Bluebird k7 to safely travel before becoming airborn had previously been miscalculated by the Norris bros etc? I hear 350 referrered to as the uppermost safe design speed, but if it was actually lower around the lower 300s then it was never going to end well. How much of a factor did the rear fin from the gnat figure in it all too?

[Renegadenemo]

It wasn't designed to go that fast - 250 would be closer, though as the speeds went up more study was devoted to what went on up there. She was pretty much maxed out at 330 with the Orph'. The fin gave fair stability in yaw but it's very intolerant of any cross-wind component. CFD studies give the max tolerable pitch angle at about 5 degrees around 300mph but, interestingly, disprove the theory that the inlets lift the front of the boat when the engine spools down - they only make a shedload of drag. The CFD studies also prove that the max lift never exceeds the mass of the craft in the zero trim condition so the theory of floating in ground effect doesn't work at all unless another explanation is offered.

The weight offset question makes me smile now as it did back in the day. Beginning at the cockpit you have the steering fulcrum, the radio and its battery. The steering rod extends all the way to the transom to the rudder and its bearing tube, which all together weighs double what the fin on the opposite side does. Then there's the swirl pot and LP pump plus a gallon of fuel and its associated pipework leading down the aux tank, with another LP pump and two thirds of its total volume on the left also filled with fuel. All the electrics run down that side as well as the entire hydraulic system and its reservoir and hoses plus contents. Aft of that is a heavy pair of fire suppression bottles with associated plumbing.
And down the right hand side... nothing.
If you put all that stuff on a pallet you'd need a forklift to pick it up and it's all rigged two feet from the centreline. The middle of the sponsons are only four feet from the centreline. Then you pick the boat up with a crane and guess what - she all falls over to the left. Surprise surprise.
But, hey - didn't Tony James say this was impossible? That'd be that then...

Next discussion - engine torque reaction as it's still being ignored. Who wants to go first?

[JohnTheBikeMan]

Bill (if I may be so familiar?). Remind me NEVER to get in an argument with you...!