Bluebird Runs 2019

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Renegadenemo
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Re: Bluebird Runs 2019

Post by Renegadenemo »

I read on another forum that the canopy was not made of strong enough perspex and this is why it blew off. Was that true or did you ever discover what happened to cause the accident?
Funnily enough there was some muttering within the plastics industry that the failure was due to materials or manufacture and we were asked to clarify that this was not the case.

There is a full account of what happened on the diary but not on the entry that actually dealt with us losing the canopy - it's on the one before about our preparations for Bute so maybe go have a read of that one. Basically, in trying to engineer out a potential failure we managed to engineer in another one but it's understood now.

Re the material - we recovered a chunk of the original from the impact site. A piece about six inches square, so we were able to properly identify it as quarter-inch Perspex. We built the new one from 7mm shatter-proof acrylic but it was no match for what happened to it. The one we built to replace the broken one withstood everything we threw at it but our pilots always ran with visors down in case of problems. We'll have a further look into how the canopy is secured when we come to build a new one.
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William Young
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Re: Bluebird Runs 2019

Post by William Young »

There is a full account of what happened on the diary but not on the entry that actually dealt with us losing the canopy - it's on the one before about our preparations for Bute so maybe go have a read of that one. Basically, in trying to engineer out a potential failure we managed to engineer in another one but it's understood now.
Thank you for directing me to that. Why was the explanation amongst your preparations for the pre trial and not included in the diary that recorded the actual event? I have another question if I may. I read with interest your mention of the holes beside the head rest being there in 1967 and that they were gradually enlarged and that Donald Campbell's mechanics were addressing some related issue. Did you ever deduce what this was?

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Re: Bluebird Runs 2019

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Thank you for directing me to that. Why was the explanation amongst your preparations for the pre trial and not included in the diary that recorded the actual event? I have another question if I may. I read with interest your mention of the holes beside the head rest being there in 1967 and that they were gradually enlarged and that Donald Campbell's mechanics were addressing some related issue. Did you ever deduce what this was?
Fair questions. The description of the canopy failure was written a long time ahead of the new Bute diaries and included in our preparations to have it explained as one or two false rumours (nowt new there) were floating about and it seemed appropriate to set the record straight. But it wasn't uploaded until much later than expected and then the Bute diaries came soon after so I just left things as they were on the basis that by the time the Bute diary that included the canopy loss came along the story of why we lost it would still be fresh in readers' minds. Really ought to copy it into the other one now that you've mentioned it, just in case.

As regards the holes in the headrest plates, that remains a theory to be tested- well spotted. We noticed that they were modified as time went on, so we drilled them circular based on one photo then, in another, we saw that they had been roughly filed to a larger size and modified them to suit - but what could it mean?

The 1966 crew presumably had a good reason for doing this and also we can presume that the holes were there to allow air to pass through the bulkhead one way or the other so based on that the questions are then then, which way was the air going, how did they know and why did they need to flow more of it?
If it was coming into the cockpit from behind and pressurising the cabin, as we assumed initially, then where was it coming from, how did they know it wanted in and why would they let it in?

The inlets were all sealed up back then with no passage from the bifurcated duct through which the engine actually breathes to the central plenum that remains at ambient pressure - or at least they were supposed to be, especially after the inlets were strengthened. Most of that part of the inlet couldn't be re-used and if it was leaking significantly the crash damage precluded any meaningful investigation but if it was leaking, did they discover this and choose to vent it into the cockpit and if so why didn't it blow the canopy off in 66/67?

We recovered the entire front edge of the canopy opening and it bears absolutely no hint of any extra device that may have tied down the front edge of the canopy with it in the closed position and that is backed up by the photo evidence. Our belief then and now is that the canopy was held down by outside air pressure only.

If there was excess pressure in the plenum it should have vented through a hole in the top provided for cooling the radio equipment that was originally housed in there so unless there was lots of pressure you'd never know.
They knew that the plenum exploded in the failure that wrecked their engine, but only because the ducts either side of it had the air pressure reduced by the engine at full throttle but it's not inconceivable that someone got their thinking wrong and thought that with a few holes popped in it, it wouldn't explode again but then what could happen to convince them that the holes weren't big enough and that filing them out was required? And then you still need a considerable leak in a structure that had just been heavily modified or, as we provided, a deliberate pathway but we saw no evidence of one.

Nothing really fits without asking more questions so let's look at it the other way and question whether the cabin was pressurising from without and the holes were to let the air escape into the plenum and thence out though the vent in the top. That would be easy enough to detect. Ted described the pressure building on his chest. So here's an alternate theory but it's virtually 100% speculation except for the fact that there were ever expanding holes in the headrest plate.

When the boat was re-engined in 66 there are pictures of it ready to leave Hayward's Heath quite clearly showing that there are no holes in that plate so they came after the Orph' conversion had been tested on water and by the time of the accident they'd been drilled then enlarged with a file so drilling them hadn't been enough. Bearing in mind that the only aerodynamic change was the Orph' and therefore, potentially what went on ahead of the inlets when the throttle was closed, so let's speculate that an area of high pressure air was building up around the inlet openings and forcing itself under the cockpit rails and that this effect was less pronounced or even absent completely with the Beryl engine. Perhaps air would still vent through the Beryl compressor but the Orph' offered much greater resistance. Then add in the much longer spray baffles and thickened inlet lips and you have to wonder whether these changes would make matters worse.

So now what do we have... Donald coming in from a run and reporting that his ears are popping when he comes out of the throttle so Leo decides a few holes in the headrest plate either side of his head will dump the pressure and allow it to vent through the top of the plenum. But Donald goes out again and complains that it's still happening - file the holes bigger.

It all fits - except the next question has to be, why did our canopy blow off and his didn't?

The simple answer to that - again, speculating here - is that the filed out holes were doing the job. Air was streaming into the cabin under the side rails of the cockpit where they aren't sealed from an area of high pressure air formed ahead of the inlets and partially trapped by the longer spray baffles whilst the lid was being held down by air pressure from above due to the forward motion. But the vent holes won the day and it all stayed down.

So what did we go and do? We deliberately created a passage from inside the inlets to inside the cabin via those same holes that didn't just eliminate the pressure gradient between cabin and plenum that would allow the cabin to vent, it actually increased the pressure in the plenum such that air began coming in the other way adding to the problem and at that point the canopy stood no chance. It would appear that as speed decayed the ram-air pressure within the inlet that we allowed all the way to the cockpit overcame the aerodynamic forces keeping the canopy down and off it went.

Another happening that initially confused us but which fits the above speculation perfectly is that we drilled those vent holes in the sides of the new canopy to make sure any pressure inside the cabin would vent out easily, yet both pilots reported the canopy attempting to lift against the bungees when slowing down. It was inconceivable that we'd not provided enough venting until you look at it from the opposite direction and realise that those vent holes - if the high pressure air ahead of the inlets theory is correct - were in fact perfectly placed such that instead of letting air out, they were actually letting more in!

All guesswork but it all hangs together nicely together and remains a fascinating puzzle to solve next time we run.
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mtskull
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Re: Bluebird Runs 2019

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William Young wrote:
Mon Mar 16, 2020 7:47 pm
I read on another forum that the canopy was not made of strong enough perspex and this is why it blew off. Was that true or did you ever discover what happened to cause the accident?
Would that be the same forum where Bill Smith is depicted as the spawn of Satan and your good self accused of being his alter ego?
-I wouldn’t set too much store by anything that is said on there; just delete the word “Piston” and substitute another word....
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Filtertron
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Re: Bluebird Runs 2019

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mtskull wrote:
Thu Mar 19, 2020 8:01 am
William Young wrote:
Mon Mar 16, 2020 7:47 pm
I read on another forum that the canopy was not made of strong enough perspex and this is why it blew off. Was that true or did you ever discover what happened to cause the accident?
Would that be the same forum where Bill Smith is depicted as the spawn of Satan and your good self accused of being his alter ego?
-I wouldn’t set too much store by anything that is said on there; just delete the word “Piston” and substitute another word....
Seems I'm not the only one! They thought I was Bill on Twatter too. I'd give them a wide birth, or perhaps offer them some foil to make a hat from. They certainly don't do their cause any justice.

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Richie
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Re: Bluebird Runs 2019

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I presumed from the lack of reply to my question, followed immediately by more questions of his own that we were talking to yet another ghost.

Had I known it was Bill all along I could have just asked him to his face 😂
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Renegadenemo
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Re: Bluebird Runs 2019

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Seems I'm not the only one! They thought I was Bill on Twatter too. I'd give them a wide birth, or perhaps offer them some foil to make a hat from. They certainly don't do their cause any justice.
They're great, I love 'em... abject cowards, every one. :lol: :lol:

No danger of any of them standing up to be counted under their real names as we do. No chance in Hell because they're unable to exist in a world moderated by their peers so they lurk in hidden backwaters like malignant cells awaiting their chance to replicate and nothing is more threatening to them than a stranger happening into that backwater and questioning their delusions - they don't deal well with others finding the cracks in their poisoned rhetoric so, in their crooked model of the world, the new guy absolutely must be their harangued, lonely victim in weakly constructed anonymity desperately fighting back - yes, that has to be it!

Seen it countless times.

I could write a diary on BBP's greatest trolls from the olden days of the 'Dear BBC' letters when the' Spawn of Satan' (love that, by the way - what a workshop shirt that would make!) and the rest of the crew first went looking for the wreck of K7, to outing a couple of Type III idiots who have never learned to spot that we have known for years who they are and when we're winding them but I have a confession here. I actually quite like our pet trolls.

It's a fascinating dynamic that's played out time and again. The great majority seem to enjoy what we do and we're always happy to share - warts and all - and we all have a good time but once every few years there's a bit of nonsense and the trolls immediately spring from their enclave and start trying to put the poison in (lots of fascinating scientific papers on the psychological traits of trolls, by the way) then they run out of ways to repeat themselves after a few weeks and go back from whence they came but when they're out and about it makes for fun times.

They're like the rats in my garden. I like my rats. They're vermin, obviously, and must be moderated with traps, rifle and poison but they are endlessly clever things that will very quickly learn that if you stand there you get shot, if you step on that a piece of powerfully sprung ironmongery it snaps your neck and if you eat too much of the blue or red grain you'll die a horrible death as your heart wears itself out trying to pump ever-thinning blood. Cunning little beasts to say the least but flawed and predictable should the need arise to exploit their failings.

But once I made the regrettable mistake of launching an all-out offensive thinking it would be an exciting challenge and wiped out my entire rat population.

FAIL! I regretted it immediately because I straight away spoiled my own fun and then spent several weeks gazing through the patio doors every five minutes in the hope of a new rat moving in. They were weeks in arriving but I was thrilled when at last I saw the familiar little form flit across the path.

Nowadays I carefully manage my rat population in order to enjoy the mental stimulation of pitting my wits against so interesting a foe and they do me the service of multiplying at an astonishing rate so there's always new ones to go after unlike the trolls whose population remains at a steady four or five, which as every geneticist knows, results in only hopeless in-breeding but late of an evening when the rats have gone to bed the trolls will do for practice. Not as clever as rats, but let's be honest here folks - hands up who doesn't occasionally enjoy handing a troll his arse?

Don't be too hard on them, eh.
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mtskull
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Re: Bluebird Runs 2019

Post by mtskull »

Renegadenemo wrote:
Fri Mar 20, 2020 2:09 am
‘Spawn of Satan' (love that, by the way - what a workshop shirt that would make!
https://photos.app.goo.gl/NcxCKNGNzHga2JWr8
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Renegadenemo
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Re: Bluebird Runs 2019

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Fantastic - want one... :lol: :lol: :lol:
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Re: Bluebird Runs 2019

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Coming to a coffee mug near you.
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