|Role||Water Speed Record|
|Manufacturer||Samlesbury Engineering (hull)
|Primary user||Donald Campbell|
£25,000 (1955 value)
Bluebird K7 is a turbo jet engined hydroplane with which Britain's Donald Campbell set seven world water speed records (WSR) during the later half of the 1950s and the 1960s. K7 was the first successful jet powered hydroplane, and was considered revolutionary when launched in January 1955. Campbell and K7 were responsible for adding almost 100 miles per hour (160 km/h) to the WSR, taking it from existing mark of 178 miles per hour (286 km/h) to just over 276 miles per hour (444 km/h). Donald Campbell was killed in an accident with a much modified K7, on 4 January 1967, whilst making a bid for his eighth WSR, with his aim to raise the record to over 300 miles per hour (480 km/h) on Coniston Water.
- 1 Design
- 2 Bluebird K7 records
- 3 Final record attempt and death of Donald Campbell
- 4 Recovery of Bluebird K7
- 5 References
- 6 External links
Donald Campbell began his record-breaking career in 1949 following the death of his father, Sir Malcolm Campbell. Initially, he had been using his father's 1939-built Rolls-Royce 'R' type powered propeller-driven hydroplane Bluebird K4 for his attempts, but he met with little success and suffered a number of frustrating setbacks. In 1951, K4, which had been modified to a prop-rider configuration to increase its performance potential, was destroyed after suffering a structural failure, when its V-drive gearbox sheared its mountings, and punched through the floor of the hull.
Following rival record breaker John Cobb's death in his jet boat Crusader, which broke up at over 200 miles per hour (320 km/h) during a record attempt in September 1952, Campbell began development of his own advanced all-metal jet-powered Bluebird K7 hydroplane to challenge the record, by then held by the American prop rider hydroplane Slo-Mo-Shun IV. Designed by Ken and Lew Norris, the K7 was a steel-framed, aluminium-bodied, three-point hydroplane, built at Samlesbury by Samlesbury Engineering, powered by a Metropolitan-Vickers Beryl axial-flow turbojet engine, producing 3500 pound-force (16 kN) of thrust. Like Slo-Mo-Shun, but unlike Cobb's tricycle Crusader, the three planing points were arranged with two forward and one aft, in a "pickle-fork" layout, prompting Bluebird's early comparison to a blue lobster. K7 was of very advanced design and construction, and its load-bearing steel space frame ultra rigid. It had a design speed of 250 miles per hour (400 km/h) and remained the only successful jet-boat in the world until the late 1960s.
The designation "K7" was derived from its Lloyd's unlimited rating registration. It was carried on a prominent white roundel on its sponsons, underneath an infinity symbol. Bluebird K7 was the seventh boat registered at Lloyds in the 'Unlimited' series.
Bluebird K7 records
Campbell set seven world water speed records in K7 between July 1955 and December 1964. The first of these marks was set at Ullswater on 23 July 1955, where he achieved a speed of 202.15 mph (324 km/h) but only after many months of trials and a major redesign of Bluebird's forward sponson attachments points. Campbell achieved a steady series of subsequent speed-record increases with the boat during the rest of the decade, beginning with a mark of 216 mph (348 km/h) in 1955 on Lake Mead in Nevada. Subsequently, four new marks were registered on Coniston Water, where Campbell and Bluebird became an annual fixture in the later half of the fifties, enjoying significant sponsorship from the Mobil oil company and then subsequently BP. Campbell also an unsuccessful attempt in 1957 at Canandaigua in New York state in the summer of 1957, which failed due to lack of suitable calm water conditions. Bluebird K7 became a well known and popular attraction, and as well as her annual Coniston appearances, K7 was displayed extensively in the UK, USA, Canada and Europe, and then subsequently in Australia during Campbell's prolonged attempt on the land speed record (LSR) in 1963 - 64.
In order to extract more speed, and endow the boat with greater high speed stability, in both pitch and yaw, K7 was subtly modified in the second half of the 1950s to incorporate more effective streamlining with a blown Perspex cockpit canopy and fluting to the lower part of the main hull. In 1958, a small wedge shaped tail fin, housing an arrester parachute, modified sponson fairings, that gave a significant reduction in forward aerodynamic lift, and a fixed hydrodynamic stabilising fin, attached to the transom to aid directional stability, and exert a marginal down-force on the nose were incorporated into the design to increase the safe operating envelope of the hydroplane. Thus she reached 225 mph (362 km/h) in 1956, where an unprecedented peak speed of 286.78 mph (461.53 km/h) was achieved on the first run, 239 mph (385 km/h) in 1957, 248 mph (399 km/h) in 1958 and 260 mph (420 km/h) in 1959.
Campbell then turned his attention to the LSR, with the aim of establishing an LSR of 450 mph (720 km/h) plus. He also planned to set a seventh WSR in the same year, and so become the first person to establish the LSR and WSR in the same year. He set out for the Bonneville Salt Flats in August 1960 and was lucky to survive a 360 mph (580 km/h) crash in his Norris Brothers designed Bluebird CN7 turbine powered car later that September. Bluebird CN7 was rebuilt in 1961 / 62 and Campbell subsequently spent a frustrating two years in the Australian desert, battling adverse track conditions. Finally, after Campbell exceeded the LSR on Lake Eyre on 17 July 1964, at 403.10 mph (648.73 km/h) in Bluebird CN7, he snared his seventh water speed record on 31 December 1964 at Dumbleyung Lake, Western Australia, when he reached 276.33 mph (444.71 km/h), with two runs at 283.3 mph (455.9 km/h) and 269.3 mph (433.4 km/h) completed with only hours to spare on New Year's Eve 1964.
This latest success made Campbell and K7 the world's most prolific holders of the Water Speed Record, and in addition Campbell realised his 'double' when he became the first, and so far only, person to break both the Land Speed Record and the Water Speed Record in the same year. Following on from this success, Campbell stated that K7 would be most likely retired and become a museum exhibit. Her hull was ten years old, her engine fourteen, and her design speed of 250 mph (400 km/h)had been exceeded by over 30 mph (48 km/h) on a number of occasions.
Donald Campbell's Unlimited World Water Speed Records
|202.32 mph (325.60 km/h)||Bluebird K7||Donald Campbell||Ullswater||23 July 1955|
|216.20 mph (347.94 km/h)||Bluebird K7||Donald Campbell||Lake Mead||16 November 1955|
|225.63 mph (363.12 km/h)||Bluebird K7||Donald Campbell||Coniston Water||19 September 1956|
|239.07 mph (384.75 km/h)||Bluebird K7||Donald Campbell||Coniston Water||7 November 1957|
|248.62 mph (400.12 km/h)||Bluebird K7||Donald Campbell||Coniston Water||10 November 1958|
|260.35 mph (418.99 km/h)||Bluebird K7||Donald Campbell||Coniston Water||14 May 1959|
|276.33 mph (444.71 km/h)||Bluebird K7||Donald Campbell||Lake Dumbleyung||31 December 1964|
Final record attempt and death of Donald Campbell
In May 1966, Campbell decided to take K7 out of retirement for one more try for a water speed record: his target, 300 mph (480 km/h).
In order to significantly improve her performance capabilities, K7 was fitted with a lighter and more powerful Bristol Siddeley Orpheus 701 turbo jet engine, taken from a Folland Gnat aircraft, and lent to the project by the Ministry of Defence (MoD), which developed 4,500 pound-force (20 kN) of thrust. The modifications and refit were handled by Norris Brothers, designers of Bluebird K7, and Campbell expected to be at Coniston Water by September 1966. Campbell was working to a tight budget. Sponsorship from British industry, who had eagerly supported his earlier exploits, was not forthcoming this time. He was covering the estimated £10,000 cost of modifying K7 and mounting the attempt from his own resources. The almost inevitable delays in the modification work meant that K7 did not actually arrive at Coniston until early November, with only four scant weeks before the British winter would set in. On the plus side, Campbell and his engineering team, headed by Leo Villa, were vastly experienced, and given a spell of decent calm weather, Campbell was confident that the attempt could be wrapped up in no more than 2 or 3 weeks.
Bluebird K7: 1966 - 67 technical specification
The hull of Bluebird K7 was stressed to twice the factor of a supersonic aircraft (Max. 25 g). Constructor: Samlesbury Engineering, Space frame: Chrome-molybdenum seamless square section steel tubing by Accles & Pollock, Outer skin: Birmabright light aluminium alloy, Sponsons & spars: Fabricated light alloy angle and plate to form watertight square box section, Planing shoes: Machined solid alloy castings, Fasteners: Rivets, high tensile steel bolts, welding, and chromate assembly paste.
Type: Bristol-Siddeley Orpheus 701 turbojet single-stage turbine, 7-stage axial compressor, 7 flame tubes; turbine inlet temp 640 °C, Max. output (nominal) lb thrust / kN 4,500 / 20.02, Max. output (boosted) lb thrust / kN 5,277 / 23.53 (110% of max., 2 °C inlet temp,) Max. output bhp / kW at 328 mph 4,623 / 3,446, At rpm 10,450, Max. jet pipe temperature 720 °C, Fuel Kerosene (AVTUR DERD 2494)
Length inc. rudder (ft & in. / m) 26 ft 5.0 / 8.05, Width inc. sponsons (ft & in. / m) 10 ft 6 / 3.20, Width of main hull (ft & in. / m) 5 ft 2 / 1.58, Height inc. tail fin & rudder (ft & in. / m) 8 ft 0.4’’ / 2.45, Sponson length (ft & in. / m) 12 ft 9.5 / 3.90, All-up Weight: (lb / kg) 5,813 / 2,637.
Trials and tribulations
Bluebird was afloat on 4 November, for Campbell to get used to her again, after an absence of almost 2 years from the cockpit. A slow speed run confirmed that from a systems perspective, everything was satisfactory. Campbell promised to display Bluebird’s power the next day by carrying out a tethered static test of her engine. The new K7 had a vertical stabiliser (also from a Gnat Campbell had purchased) and a new hydraulic water brake designed to slow the boat down on the five-mile Coniston course. Any hope of an easy record evaporated the next day, when Bluebird’s engine was destroyed after her intake structure collapsed during the full power test. Campbell was now faced with delay and expense as the intake structure was rebuilt and the spare engine, Nº711, installed. The team worked in horrific weather, in the makeshift boathouse to replace the engine, and refit the repaired intakes. The original but now wrecked engine, Nº709, remained outside the team's lakeside workshop for the rest of the project, open to all the elements. By 18 November, after 2 weeks of frantic work, Bluebird fitted with a spare engine, which Campbell had purchased for £200, and the newly reinforced intakes, was again ready to take to the water. ‘There is no form of Record breaking where you get it smooth’ Campbell had been quoted as saying. The next week was to prove that statement only too true. Bluebird made daily trips out on to the lake, but the fitment of the lighter Orpheus engine had changed her configuration, moving the centre of gravity forwards, and she resolutely refused to plane. Campbell’s frustration grew daily, and he knew very soon the weather would close in. Eventually, in order to change her nose heavy weight distribution, two sandbags were lashed to her stern, and the K7 was towed back out on to the mirror like lake. This time, when Campbell applied more power, she did not wallow, but instead rose quickly onto her planning points, and sped off down the lake. At last the attempt was on back on track. The modification to K7’s weight distribution was made permanent by attaching over 170 lbs. of lead ingots to her inner frame at the stern. As if on cue, the weather now closed in. It was a pattern that was to be repeated almost ad nauseam over the nine weeks Campbell was at Coniston. Bluebird ready to go, weather abysmal. Weather suitable, Bluebird out of action.
Eventually after a further two-week wait Campbell as a last able to make some quick runs, moving the speeds up from 202 mph (325 km/h) on 10 December to 264.6 mph (425.8 km/h) by the 14th, but Bluebird was still not performing as expected. After prolonged investigation, a poorly performing fuel pump was identified as the cause of the lacklustre performance. By the time this component was replaced on the 15th, the weather closed in again and Bluebird was confined to her boat-shed. 5 days later Bluebird sat trapped in her boathouse, which had partially collapsed under the weight of rain and snow, while outside, the water conditions were perfect, It was as if Campbell was being taunted. It was by now close to Christmas, and the timekeepers press and TV crews were getting restive. Campbell was forced to postpone any further high speed trials until 28 December. The team made their way home for the holidays, but Campbell chose to stay at Coniston, almost as if he could not escape its grasp. Fate played two more cruel tricks. On Christmas morning, the lake was like a mirror. Campbell could not resist the temptation, and with the aid of a few local helpers Bluebird was afloat and two quick runs in excess of 250 mph (400 km/h) were completed. The 27 December brought a repeat, and Bluebird completed her fastest speed runs to date, at over 285 mph (459 km/h). It was to no avail, unobserved and un-timed, the unofficial speed, although in excess of the record, could not be recognised. To add to the sense of misfortune, Bluebird struck a duck on the second run causing damage to the fairing of the forward spar linking the main hull with her sponsons on her port side. After that, as if almost by some twisted timetable of fate, the weather closed in, and it would be some 8 days before Bluebird and Donald Campbell were afloat again. A static test of K7's engine was carried out on 2 January, to test a modification to the fuel system, incorporating a boost pump that was fitted after the run on the 28th. For the first time, the BS Orpheus, engine number 711, engine exceeded its stated maximum revs. Campbell was satisfied that once the weather improved, K7 would have sufficient power for a crack at the 300 mph (480 km/h) record
On 4 January 1967, Campbell mounted his record attempt. Bluebird had completed an initial north-south run at an average of 297.6 mph (478.9 km/h), and Campbell used a new water brake to slow K7 from a speed of about 240 mph, after reaching a peak speed of 311 mph (501 km/h) exiting the measured kilometre. This run, which was originally thought to have occurred in perfect trim and without incident, has been shown to demonstrate evidence of instability with pitch-up of approx. 3° and a 'bouncing' episode involving the starboard sponson leaving the water for 0.7 seconds, at the end of the measured kilometre Following this, an engine flameout was reported by Campbell and activation of the water-brake was found to be not as efficacious as had been demonstrated in previous, lower-speed runs.
Campbell's words on his first run were, via radio intercom:
|“||... I’m under way, all systems normal; brake swept up, er . . . air pressure warning light on . . . I’m coming onto track now and er . . . I’ll open up just as soon as I am heading down the lake, er doesn’t look too smooth from here, doesn’t matter, here we go . . . Here we go . . . [pause 3 seconds]. . . Passing through four . . . five coming up . . . a lot of water, nose beginning to lift, water all over the front of the engine again . . . and the nose is up . . . low pressure fuel warning light . . . going left . . . OK we’re up and away . . . and passing through er . . . tramping very hard at 150 . . . very hard indeed . . . FULL POWER . . . Passing through 2 . . . 25 out of the way . . . tramping like hell Leo, I don’t think I can get over the top, but I’ll try, FULL HOUSE . . . and I can’t see where I am . . . FULL HOUSE – FULL HOUSE – FULL HOUSE . . . POWER OFF NOW! . . . I’M THROUGH! . . .power . . . (garbled) er passing through 25 vector off Peel Island . . . passing through 2 . . . I’m lighting like mad . . . brake gone down . . . er . . . engine lighting up now . . . relighting . . . passing Peel Island . . . relight made normal . . . and now . . . down at Brown Howe . . . passing through 100 . . . er . . . nose hasn’t dropped yet . . . nose down ."||”|
Instead of refuelling and waiting for the wash of this run to subside, Campbell decided to make the return run immediately. This was not an unprecedented diversion from normal practise, as Campbell had used the advantage presented i.e. no encroachment of water disturbances on the measured kilometre by the quick turn-a-round, in many previous runs. The second run was even faster once severe tramping subsided on the run-up from Peel Island (caused by the water-brake disturbance). Once smooth water was reached some 700 metres or so from the start of the kilometre, K7 demonstrated cycles of 'ground' effect hovering before accelerating hard at 0.63g to a peak speed of 328 mph (530 km/h) some 200 metres or so from the southern marker buoy. Bluebird was now experiencing bouncing episodes of the starboard sponson with increasing ferocity. At the peak speed, the most intense and long-lasting bounce precipitated a severe decelerating episode (328 mph - 296 mph, -1.86g) as the airborne starboard sponson of K7 dropped back onto the water. Engine flame-out then occurred and, shorn of thrust which provided a nose-down moment, K7 experienced a gliding episode in strong ground effect with increasing angle-of-attack (AoA), before completely leaving the water at her static stability pitch-up limit of 5.2°. Bluebird then executed an almost complete somersault (~ 320° and slightly off-axis) before plunging into the water (port sponson marginally in advance of the starboard), approximately 230 metres from the end of the measured kilometre. The boat then cartwheeled across the water before coming to rest. The impact broke K7 forward of the air intakes (where Donald was sitting) and the main hull sank shortly afterwards. Campbell had been killed instantly. Mr Whoppit, Campbell's teddy bear mascot, was found among the floating debris and the pilot's helmet was recovered. Royal Navy divers made efforts to find and recover the body but, although the wreck of K7 was found, they called off the search after two weeks without locating his body.
Campbell's last words during a 31 second transmission made on his final run were, via radio intercom:
|“||. . . Full nose up . . . Pitching a bit down here . . . coming through our own wash . . . er getting straightened up now on track . . . rather closer to Peel Island . . . and we’re tramping like mad . . . and er . . . FULL POWER . . . er tramping like hell OVER. I can’t see much and the water’s very bad indeed . . . I’m galloping over (I can’t get over) the top* . . . and she’s actually giving a hell of a bloody row in here...I can’t see anything...I’ve got the bows out ...I’m going . . . U-hh . . .",||”|
- *This phrase is disputed, but the former is more consistent with events timed to coincide with it, when K7 was accelerating very hard on an almost perfect water surface. This interpretation has been arrived at by exhaustive analysis by the authors of 'Donald Campbell, Bluebird And The Final Record Attempt' in 2010/2011, and differs from the original interpretation arrived at in 1967. Donald Campbell's run commentary abilities had been likened, on many occasions, to those of a test pilot and should be interpreted as a stream of consciousness, where events are effectively described in real time.
The cause of the crash has been variously attributed to Campbell not waiting to refuel after doing a first run of 297.6 mph (478.9 km/h) and hence the boat being lighter; the wash caused by his first run and made much worse by the use of the water brake, (These factors have since been found to be not particularly important. The water brake was used well to the south of the measured distance, and only from approx. 240 mph (390 km/h) The area in the centre of the course, where Bluebird was travelling at peak speed on her return run was flat calm, and not disturbed by the wash from the first run, which had not had time to be reflected back on the course. Campbell knew this and, as discussed previously, adopted his well-practiced, 'quick turn-a-round' strategy.
Following extensive reworking of the original accident analysis carried out in 2010/11, the cause of the crash can be put down to Bluebird K7 exceeding its aerodynamic static stability limit, complicated by the additional destabilizing influences of loss of engine thrust, damage to the port spar fairing, and, the hitherto unappreciated contribution of ground effect lift enhancement. There is also evidence to point to the fact that K7s dynamic stability limit had been exceeded. The cause(s) of the engine flame-out cannot be established unequivocally. It could have been due to fuel starvation, damage to some ancillary structural / electrical element associated with engine function (following the worst bouncing episode), disturbance of the airstream into the intakes during the pitching episodes, or indeed a combination of all three. Further evidence of lost engine thrust may be seen in both cinematographic and still film recordings of the latter part of the run - as Bluebird left the water, jet exhaust from a functioning engine would have severely disturbed the water surface; no such disturbance or accompanying spray is evident. Also, close examination of such photographic and film records show no evidence to the effect that the water brake was deployed.
Recovery of Bluebird K7
The wreckage of Bluebird was discovered on the lake bed on 5 January 1967. A 10-man Royal Navy diving team led by Lt Cmdr John Futcher, had arrived at Coniston late on the day of the accident. They set off for first attempt to locate Donald Campbell and Bluebird at 12.30pm the next day. Futcher believed that Campbell's body would be either at the point of impact, in the main wreckage of the boat, or at a point between the two locations. Ken Norris had worked out some calculations to guide the dive team to its likely resting point. The first three dives that afternoon found small pieces of wreckage, indicating the dive team were on the correct track. On the fourth dive, the main hull of K7 was found in 142 feet of water, resting in her correct attitude but facing to the south east. A subsequent and prolonged search located many pieces of wreckage, and indeed items were brought to the surface including Bluebird's broken steering wheel and column. However, the body of Donald Campbell was not located, and the search was called off on 16 January. The Campbell family and team let it be known that they did not wish to have the hull of K7 recovered in the absence of finding Campbell's body. They also felt they would learn nothing from its recovery. The wreck sat on the lake bed for a further 34 years, its location known by a few people but never disclosed.
A diving team led by Bill Smith was responsible for relocating the wreckage and its subsequent recovery was handled by Smith's Bluebird Project team. The wreckage was recovered between October 2000, when the first small sections were raised, and May 2001, when Campbell's body was finally recovered. The largest section, representing approximately two-thirds of the main hull, was salvaged on 8 March 2001.
Controversy over the recovery
The exact date of the retrieval of Campbell's body from the lake was 28 May 2001. He was interred in Coniston cemetery on 12 September that year after a funeral services at St Andrews Church in Coniston.
Campbell's sister Jean Wales had been against the recovery of the boat and her brother's body out of respect for his stated wish that, in the event of something going wrong: "Skipper and boat stay together." This quotation is usually said to have been uttered by Campbell when, in the final week of 1964, he was waiting for good weather to attempt a record run, but a bid seemed so unlikely at that point, his colleagues were pressing him to leave. He refused, and broke the record on the last day of 1964. Jean Wales did not attend his burial or visit his grave although she did remain in daily contact with the salvage crew as the boat's wreckage was being brought ashore.
Forensic examination and causes of the accident
Because the boat's water brake was found to be extended when the wreck was recovered, it was generally assumed that Campbell had activated it to slow down before the boat had left the water on his final run. On dismantling the boat, however, a hydraulic accumulator from the donor Gnat aircraft was discovered to be still connected to the system, meaning that stored hydraulic pressure may well have deployed the brake after the accident.
The boat still contained fuel in the engine fuel lines and a quantity was collected and analysed using gas chromatography as part of the official investigation of the accident commissioned by Barrow Coroner. However, insufficient evidence was present to completely discount the fuel starvation theory. The engine could have cut-out as a result of intermittent fuel starvation caused by the untried fuel system or failure of the electrical supply to the low-pressure fuel-boost pumps. Full details of the boat's strip-down, and the conclusions drawn from it by the investigators, are lodged within the public domain in the diary pages of the Bluebird Project website.
Restoration and future running
On Thursday 7 December 2006, Gina Campbell, Donald's daughter, formally gifted Bluebird K7 to the Ruskin Museum in Coniston on behalf of the Campbell Family Heritage Trust. In agreement with the Campbell Family Heritage Trust and the museum, Bill Smith is to organize the restoration of the boat, which is now under way. Now the property of the Ruskin Museum, the intention is to rebuild K7 back to running order circa 4 January 1967. Bill Smith has said that this will take an undisclosed number of years to accomplish. Gina Campbell commented: "I've decided to secure the future of Bluebird for the people of Coniston, the Ruskin Museum and the people of the world". Museum Director Vicky Slowe spoke of Gina's generosity and then said: "Bill Smith has assured us he can get Bluebird fully conserved and reconfigured at no cost to the museum.As of 2008[update], K7 is being fully restored by The Bluebird Project, to a very high standard of working condition in North Shields, Tyne and Wear, using a significant proportion of her original fabric, but with a new BS Orpheus engine of the same type albeit incorporating many original components."
As of May 2009 permission has been given for a one off set of proving trials of Bluebird on Coniston Water, where she will be tested to a safe speed for demonstration purposes only. There is no fixed date for completion of Bluebird K7 or the trials. K7 will be housed in her own purpose built wing at the Ruskin Museum in Coniston, while remaining in the care of The Bluebird Project.
- Tremayne, David (2005). Donald Campbell: The Man Behind the Mask. Bantam Books. ISBN 0-553-81511-3.
- Sheppard, Neil (2011). Donald Campbell Bluebird And The Final Record Attempt. GL5 2QG, UK: The History Press. p. 256. ISBN 978 0 7524 5973 8.
- Holter, Steve (2002). Leap Into Legend. Sigma Press. p. 135. ISBN 1-85058-794-9.
- Holter 2002, p. plates between 118–119
- Sheppard, Neil (2011). Donald Campbell Bluebird And The Final Record Attempt. GL5 2QG, UK: The History Press. p. 256. ISBN 978 0 7524 5973 8.
- GRO Register of Deaths: MAR 1967 10F 692 ULVERSTON - Donald M. Campbell, aged 45
- "Last words from Bluebird". BBC News. 2002-12-10. Retrieved 2009-12-31.
- ‘Experimental Evaluations of the Aerodynamics of Unlimited Racing Hydroplanes Operating in and out of Ground Effect’, R.J. Englar, D.M. Shuster and D.A. Ford, SAE Technical Paper Series 901869, 1990.
- Application of Theory to Hydroplane Design, RL Schaffer, American Institute of Aeronautics and Astronautics, Paper Number 89-1532-CP, 1989.
- Personal Communications between RL Schaffer and KW Mitchell, March/April, 2014.
|The wreckage of the tailfin of K7|