Tales from The Cockpit

[kneeslider]

Ted in donalds book ‘ into the water barrier’ he said k7 pulled to one side when putting on the power due to the gyroscopic forces of the engine spinning, can you tell me if you experianced this your self?

There's two effects from the spinning engine. One is the precession of the rotatives such that a right hand input will cause the nose to rise and vice-versa. The other is the torque reaction - the compressor spins one way so it wants to rotate the boat around it in the other direction. With the Orph' this lifts the left sponson and counters the weight imbalance. There's a great shot on the Sky doco of Ted killing the engine after a slow run and the left sponson dropping like a stone. Can't comment on the Beryl, which is what was fitted when Into The Water Barrier was written but assuming the weight and balance was correct the tendency would be to dig in one sponson as the torque reaction increased with the engine loads and that may well have caused the boat to pull to one side. How apparent any effect is in the cockpit nowadays, maybe Ted can tell us.

Sounds like the sort of thing you have to cope with when flying a single engine piston powered taildragging light aircraft. Well, sort of!

You deal with all those pesky torque and precession forces with control inputs on the rudder. Unfortunately the fin on K7 is fixed in place. Maybe the ultimate solution would be a pair of rudder pedals, and replacing the foot operated throttle with a hand throttle as found in an aircraft??

[JfromJAGs]

There's two effects from the spinning engine. One is the precession of the rotatives such that a right hand input will cause the nose to rise and vice-versa. The other is the torque reaction - the compressor spins one way so it wants to rotate the boat around it in the other direction.

Hi Bill, Joerg, one of "the Germans" (and RC model boat guy) from the Isle of Bute here.

[/smart ass mode ON]
Actually there a 3 effects:

1. "dynamic torque" - when the rotating mass of the turbine changes its roation speed, when it accelerates or decelerates, then you see a force on the hull in the opposite direction of the rotation during acceleration and in the same direction during deceleration. If the rotation speed stays constant, then there is no such kind of dynamic force. Because a turbine changes its rotation speed rather slowly (compared to an IC or electric motor) such forces are rather small, so not sure of you see them.

2. "static torque" - when the rotating mass of the turbine rotates at constant speed and if the axis of the rotations does not change its direction, this is when the vehicle stands still or drives straight(!) in one direction, and the turbine - as a motor - produces thrust, then you might see forces due this thrust. In case of a water prop drive boat you see significant torque due to the rotating prop transfering forces to the water. In case of a turbine or a jet, be it an air or water jet, the amount of torque you notive on the hull depends on how much the spin of the air/water flow created within the thrust disc of the propulsion system gets removed behind it. Typically for such system designs is that they try to remove such spin completely - using fins behind the thrust disc - so in the end the complete drive system is more or less free of torque transfer onto the hull - good examples are jet powered boats. Looking at the stream behind K7 turbine, I didn't notice much spin in the air flow - if at all. Thus at power there should be very little torque reaction on the K7 hull. This might have been different for the older Beryl design - did this thrust cone show more spin?

3. "gyroscopic forces" - these are the typical forces everyone might remember from school when you spin a bicycle wheel and try to tilt the rotation axis -> the real movement is always vertical to both the axis and the direction you push it to - known as the right hand rule. K7 sees such forces when either turning - depending on direction it will either lift or push the bow - or when running over waves - when the bow tries to bounce up and down - but instead the boat turns left and right. So some effects which Ted described as side wind effects from tail fin might come from running in rought water.
[/smart ass mode OFF]

Ted, we talked on Bute about applying the water brake and how tricky this is - through the steering wheel. You might want to explain this again as this might be of interrest to understand why K7 was found with the brake down, but still flipping without any sign it beeing applied. Then, how does it feel when you apply it? Bill wrote somewhere you almost bit into the steering wheel, but at the same time it didn't slow the boat down much - how did that feel? Second, looking at old footage and also the videos of the first week on Bute it seams as if K7, once one plane and when more power was applied, pushes at first the bow down into the water again, creating a lot of spray. Is my oberservation correct? If so, did you ever find a way to avoid this, by either acceleration slower once on plane - or giving more power to get on plane and then directly accelerate from there?

Thanks,
Joerg

[Renegadenemo]

A smart ass and a German! That's going too far...

Thanks, Joerg, for expanding our knowledge.

[ted.walsh]

Did this all happen on week 2? as apart from 1 failed start due to failed fuse on the igniter circuit once yourself or Stew had released the air start button I had disconnected the power and air feed within 1.5 seconds everytime without incident for 7 days calmly and as we say in the workshop “perfect, but it will have to do” I was just wondering...

well that was just it! after the few close calls in the yard where the damp air from the new compressor with the bad drier caused to regulator to lock and bleed down to zero the start boat procedure was worked up on that basis where we knew there was potential along with a lot more water than the yard has , there wasn’t so much as a whisper of inconvenience until we started to swap the start crew about for training purposes and your super experienced hands took a back seat for a few days
all was good in the end and really showed the benefits of the training excercise in a low stress environment where there was no pressure or real expectation to deliver a ‘show’ on demand

[wbjohn]

Thanks Ted

[Canopener Al]

Joking apart - you can talk to yourself all you like Ted... it takes some proper planning, preparation and “right stuff” to do what you and Stew did, and I expect a fair amount of wear to the seat of your pants. Hats off to you both!

Hi Stuart, Was great to have you along for a day and to see the big boss on the tools and covered in grease. Sad that your inestimable contribution never officially took place but at least not a single drop of water made it past the grease-packed rudder post after you and the crew took it in hand that afternoon. Thanks for everything - you know what I mean.

A few years back my folks presented me with a picture of a much younger me, covered in muck and grease after rebuilding the suspension of an unworthy car. Underneath they had penned the inscription “never forget who you truly are”... Sadly, I get no chance to get mucky at work these days, but I look back fondly and really couldn’t stand by and let that one pass me by, so thanks for the chance to play!

Canopener Al - not sure why your Adours would overtemp... you must have the T6 limiter amp wired up or you’d revert to max trim. Is the limiter locked out during start? Not that I'd know anything about it of course

We have TGTs in the keel and they have been wired up to the T6 boxes. Driver is a well expericenced Sootie. Lucky to have TGT Amps. Hope they work, but if the EGTs go through the roof, quick hands on the HP shut offs.

[ted.walsh]

FLAMEOUT!
So… as far as I am led to believe a ‘flameout’ is the name given to the condition where the self-sustaining nature of fire going on in the burner cans gets quenched for some reason and goes out. Generally this is due to a lack of fuel or air or both. I dare say there is an endless list from the aerospace professionals but those are the biggies.
So it came as a bit of a surprise on the early trips that repeatably out went the fire and because we are using the off board air start bottles, that would be it until BB was recovered to the ‘Pit end’ of Fad or the start boat had chugged to the other end to deliver the reviving toot of compressed air to spin me back up. From the observations point of view the first real visual indication something was up was the low oil pressure warning light being illuminated on the dash in the corner of your eye by which time the motor had spun down below critical. Yes yes yes I hear you say ‘you should be looking at the rev counter’ but apart from the instrument being quite hard to read at a glance, the little numbers on the inside scale being the most important ones, it means dragging your eyes off the rapidly shrinking puddle of Loch Fad where the shore and a lengthy spell in hospital await.
After a bit of a debate and some looking about during a run it was simply that the ‘engine to idle’ or HP Fuel lever on the blocktube had moved backwards by about 15mm. The throttle pedal and the Idle control are linked together by a straight forward but unnecessarily complicated set of levers, tubes, ball joints, fulcrums, gates, and forks to allow the idle control and the loud pedal to do their thing on the single push pull rod that is connected to throttle quadrant on the bottom of the engine.
In terms of historical context things get interesting about now and the big deal with this one is the block tube control box. Ours is an exacting and faithful replica built by Barry Hares of the original which is now a museum piece, but it doesn’t have much of a lock or any real ‘detent’ to hold the Idle control in position once it is set. This means that if you come off the throttle with anything other than the slowest creep the momentum in the throttle pedal, its rod along with general vibration is enough to move the idle control to a position when the engine will shut down. You can put your hand on the lever as a watching brief when you throttle off of course and this is what we eventually learnt to do but it took a couple of runs to figure out. The foible caught us out on a few occasions even when we knew it was prone to happening and I cannot help thinking back to the transcript of DMC’s penultimate run where he comments about needing to relight on his way south…was the need for this caused by the same issue with his Blocktube and idle control as well?
The other flameouts or engine shutdowns as they might just have been, that are of interest are equally up there. It was on a run south away from the pits. I had brought BB down off the ‘High’ plane into a transition where the boat was still riding high on the sponsons but the tail of the boat had sunk back giving a pronounced bows up position (that we later got good at replicating). I thought it would be worth trying to turn the boat in this semi planning state. this would have had several advantages, firstly it would take a lot less time and secondly the helm authority is much better with some speed on rather than trying to get the big blue lump to turn when once she was back in full displacement mode. The other problem with a slow turn is that it is a little uncertain what sort of turning circle she is going to take as the big tailfin is so affected by any wind. Anyway with the boat in a semi planning state I attempted the turn to bring her heading back towards the pits, juggling the throttle to maintain the planning state where at a point about half way through the turn, in a cross cum downwind state I asked for more power and phut’ out went the fire and on came the lights, darn it… consensus seems to think that the wind coupled with the baffle configuration contributed to this and I’ll be sure to try it on again given a chance…
The last time of note that the engine ‘self-extinguished’ was on the last day of the training exercise, I had been out in BB for some demonstration passes the previous day, we had fully tanked the boat, brimming the 56 gallons that she will hold and done two passes in the pit end of the loch before the narrows, the team then put her to bed. Come the morning after the usual wait we went for more demonstration runs. This time the plan was to do two consecutive laps of the loch and I got the first cracked off with no issues so stick to the plan and off I went towards the narrows, throttling down to turn around before coming back onto the plane but then just as I powered her up to get up onto the wedges, phut, out went fire. Once back to the pit area the team brimmed her before we resumed the days activities.But hold on a minute… we had been full the day before, done a couple of demos and parked up overnight, we didn’t refuel yet had run out only one and a half passes later?. The historic significance question here of course is ‘is the fuel that marginal?’. We are on a much smaller body of water yet with barely and full lap on Coniston under our belts yet had run out of fuel and we weren’t even running wide open throttle for much of the time so… did DMC just run out of fuel on his return run just when it mattered the most?

Till the next one...
TED

[ted.walsh]

Ted, we talked on Bute about applying the water brake and how tricky this is - through the steering wheel. You might want to explain this again as this might be of interrest to understand why K7 was found with the brake down, but still flipping without any sign it beeing applied. Then, how does it feel when you apply it? Bill wrote somewhere you almost bit into the steering wheel, but at the same time it didn't slow the boat down much - how did that feel? Second, looking at old footage and also the videos of the first week on Bute it seams as if K7, once one plane and when more power was applied, pushes at first the bow down into the water again, creating a lot of spray. Is my oberservation correct? If so, did you ever find a way to avoid this, by either acceleration slower once on plane - or giving more power to get on plane and then directly accelerate from there?

Thanks,
Joerg

Yes Joerg, the momentary switch for the Brake is positioned in a place just to the right of centre pretty much hidden by the wheel once your in the seat. You can reach the switch above or below the rim but if your wanting to deploy it in haste its damm hard to find! http://www.bluebirdproject.com/index.ph ... p_gal]/78/ There is no real feedback on the switch, its a pretty flimsy period Lucas affair and when you apply it nothing really seems to happen when over 150mph for a couple of seconds, or an eternity which ever comes first. When i tried it the first time at about 100mph it really dragged me off the plane and I was impressed given that I had initially assumed it would be pretty pathetic. The spray pattern once deployed is very characteristic, see the latest return run pics now on the new cards in the shop, http://www.bluebirdproject.com/index.ph ... y=18889325 It would now be interesting to look at the old video again to see if there is any change in spray pattern indicating deployment.
Yes, powering up does push the bow down a lot that is why the initial 'negotiations' to get her onto the plane are quite subtle. if you just plant it she just buries the bow and too much water goes down the pipe killing the JPT and any power with it. you cannot recover from that situation there just isn't enough heat in the engine to push her over the hill and the only way out is to back off, let her settle then sneak up on her again...once she is climbing out there is no option but to apply 100% until doing 130+ otherwise there isn't enough clearance on the 'Chin' of the bow and it will catch giving the characteristic spray pattern for both Stew and I, oh yes and DMC as well if you look at some of the old footage!

[ted.walsh]

With the water being quite choppy on some days, what was your forward Viz like ?

to be fair even with the chop the ride is ok and not a jarring as it would first think but the extra spray it generates is a pain. As soon as any water gets inside the canopy and into the cockpit , and it is sucked in there by the intake vacuum leaking into the cabin, the vis becomes very marginal bit like going past a wagon on the motorway with no wipers along with a lot of fogging...
The first canopy leaked less for some reason, its replacement was a sieve by comparison...

[Renegadenemo]

its replacement was a sieve by comparison...

It didn't latch back onto the seals and it was a poor fit and full of holes. Don't worry - by the time you take her out next we'll have sorted the vacuum gotcha and made a much tighter canopy.

Great tales from the cockpit, by the way. Obviously I've heard them in the debriefs but I can imagine those who haven't really enjoying them.