Technical Talk

[rob565uk]

With or without talc?

Most definitely without! The mess was horrendous, though the workshop did smell nice.

[Anthony1]

There are two things that puzzle me. How did Donald operate the water brake? Was it by a foot pedal or lever? I know that in order to get the K7 onto her planing points he turned the wheel to the left and jabbed the water brake. That suggests a pedal. Was any of this mechanism recovered?

Secondly, it has been suggested that, if he throttled back, that could have affected the stability of the boat and caused the crash. But, even so, he would have had to throttled back at some point, so how can that cause instability? If it does then how would he be able to stop? This still mystifies me.

Terry Crofts

[Mike Bull]

Hello Terry, welcome. To answer part of your question at least, K7's water brake was operated by a simple sprung lever switch mounted on the dashboard, which was marked 'HYD BRAKE UP' and 'HYD BRAKE DOWN'. The switch and the dashboard it was mounted in remain on the bottom of Coniston somewhere. The water brake itself was still mounted on K7's transom when she was recovered, and the hydraulic system for it was still inside the main hull.

(Incidentally, under Donald's right foot was his throttle pedal of course, and under his left, his radio pressel switch- he would brace himself against this and transmit continuously throughout each run)

[Renegadenemo]

I know that in order to get the K7 onto her planing points he turned the wheel to the left and jabbed the water brake.

Not sure about jabbing the water brake and turning left - I've often wondered whether this was untried or mixed up when it was written.
Certainly turning left with the Beryl engine ought to have lifted the front of the boat due to the gyroscopic precession of the engine but, (assuming the info I have about the Beryl's direction of rotation is correct) the Orph' spun the other way and either way, turning left with the Orph' installed would depress the nose - we know which way an Orph' spins.
This, of course, would have the opposite effect when turning right and we know that on the final run, Donald started further east than he was comfy with and had to head back to the centre of the lake and make right-hand steering inputs at very high speed to get back on track.
Jabbing at the water brake would, I suspect, do no more than pull the nose down if it had any effect at all at such low speeds so we may be seeing a bit of Campbell the showman there.

[Techteam]

I know that in order to get the K7 onto her planing points he turned the wheel to the left and jabbed the water brake.

Not sure about jabbing the water brake and turning left - I've often wondered whether this was untried or mixed up when it was written.
Certainly turning left with the Beryl engine ought to have lifted the front of the boat due to the gyroscopic precession of the engine but, (assuming the info I have about the Beryl's direction of rotation is correct) the Orph' spun the other way and either way, turning left with the Orph' installed would depress the nose - we know which way an Orph' spins.
This, of course, would have the opposite effect when turning right and we know that on the final run, Donald started further east than he was comfy with and had to head back to the centre of the lake and make right-hand steering inputs at very high speed to get back on track.
Jabbing at the water brake would, I suspect, do no more than pull the nose down if it had any effect at all at such low speeds so we may be seeing a bit of Campbell the showman there.

The quote about how Donald used to get her on the plane interested me when I first read it years ago. I often wondered if there was any substance in it. I suppose thinking about it that there are many more hydro dynamic forces involved in getting the boat over the hump than just relying on the rotational assistance of the engine. It could be that forcing the nose down was in fact what was needed when the beryl was fitted due to the differing weight distribution and the sponsons were changed considerably during the years so maybe the procedure changed considerably as well after the orpheus was fitted. I guess it will all be part of the steep learning curve yet to come. Good Luck.

[Renegadenemo]

We've had a lot of studies done on the boat over the years so we're hoping we have sufficient data to beat the odds. We'll see.

[sheppane]

DMC's use of the term 'brake' as far as I am concerned did not refer to the water brake.

In order to get K7 over the hump, particularly on absolute flat calm, Campbell would apply full power to build up momentum, he would then, when K7 was traveling north of 40mph lift suddenly from the throttle. At the same time, he would apply a sharp helm to port, this would have the effect of lifting the transom and starboard sponson, almost imperceptibly - he would then, before any real momentum had been lost, bury the throttle again, get the helm straightened up and as the speed incresed, Bluebird would rise to her points. The term 'brake' is to indicate backing out of the throttle, so unstick the suction of K7's floor, not an application of the hydraulic water brake.

If conditions were a choppy on the surface (say 1 - 1.5'' chop), and a sub 150mph run was planned, K7 was much easier to get up on to her points, providing she was not running into any swell. A swell would cause the boat to porpoise at relatively low speed, meaning that planing condition was difficult to maintain.

[Renegadenemo]

The term 'brake' is to indicate backing out of the throttle,

That makes much more sense.

[klingon]

So basically in flying parlance he did a bunt to get k7 up on the plane?

[Renegadenemo]

So basically in flying parlance he did a bunt to get k7 up on the plane?

That seems to be the theory... Not sure how well it would work, mind you. K7 is quite a bit lighter than most people realise but she doesn't have a lot of spare buoyancy.