IT WON’T TAKE OFF!
The two most likely causes are [a] poor u/c design and/or [b] not enough power.

TRICYCLE GEAR
Wheels should be big enough for the worst runway surface.  (George’s mower crew can’t be as good as ours ‘cause he finds on grass the practical minimum diameter is 63 mm!  We can comfortably handle 40 mm although he does go on to say)......With 50 mm or smaller wheels, the U/C acts like an anchor on landing and may do more harm than good.
Main wheel track of 1/4 to 1/5 of wing span is about right.  The U/C legs ought to allow prop clearance by one wheel diameter.  They should also allow the model to put its tail down far enough for the wing to reach its maximum lift angle of attack [AoA] which is also the stalling AoA.  At this point the main wheels should be touching the ground just under the centre of gravity [cg] 
You can decide this on the drawing board and decide whether to lengthen the leg or sweep up the rear of the fuselage.  If the main wheels are too far back, the tail has to provide a lot of downward force to lift the nose into the take off attitude.  If the model cannot get up enough speed to develop that much tail force it can’t possibly take off.
With the main wheels too far forward, nothing much happens except that the model can be left sitting on its tail with the nosewheel in the air.  Undignified.
The main wheels should not be too close to the nose wheel in the fore and aft direction, see sketch.  If the triangle becomes too flattened, the model is likely to nose over on landing.  Keep the wheelbase to at least 50% of the track but preferably about 60% of the track.

Fig.1 TRICYCLE GEAR SHOULD GIVE AT LEAST 1 WHEEL DIAMETER GROUND CLEARANCE

Fig.2 MAIN WHEELS SHOULD BE DIRECTLY UNDER REARMOST C/G POSITION WHEN MODEL IS IN TAKEOFF ATTITUDE

Fig.3 TRICYCLE GEAR WHEELS SHOULD FORM A BROAD TRIANGLE WITH THE WHEELBASE ABOUT 60% OF THE TRACK

THE "KOOKABURRA"

The Westland Widgeon
The Westland Widgeon was designed and built at the Westland Aircraft factory, Yeoville, Somerset, UK. The first Widgeon was designed for the 1924 Lympne air competition. A simple hugh-winged monoplane, the Widgeon was an advanced concept for its time. Its design incorporated the absence of rigging wires, using in place tubular steel struts to brage the wings which were hinged to facilitate storage in the hangar.
The semi-monocoque timber fuselage was strengthened by a sheath of glued and doped fabric. In 1927 Westland produced their Mark III Widgeon, which was fitted with an 80 hp Cirrus engine. The aircraft was offered with single or dual controls, with the seats in tandem with the pilot at the rear.
One of several exported to Australia, G-AUKA christened the "Kookaburra" - was purchased by Keith Anderson in Sydney on 22 February 1929 for 889 pounds.

The "Kookaburra" Story
The "Kookaburra" remains were recovered from the East Tanami Desert in 1978. They had lain there since 10 April 1929, when the aircraft was forced to make an emergency landing. It had taken off from Alice Springs earlier that day to take part in the search for the missing aviators Charles Kingsford Smith and Charles Ulm.

The Coffee Royal Affair
At 0945 on 30 March 1929 Kingsford Smith, Ulm and their crew took off from Sydney on what was to become a controversial episode in Australian aviation history. En route to Wyndham, WA, 28 hours after takeoff, the "Southern Cross" sent out a short radio message: "We are about to make a forced landing in bad country". The nation waited - there was no further message.
After 24 hours a full scale search was mounted, while Smith and his crew sat and waited unhurt on mud flats near the Glenelg River in the north-west of Western Australia. Stranded with limited supplies and no radio contact with the outside world, Smithy brewed coffee laced with brandy and cracked a wry joke about Coffee Royal.
Little was Smithy to realise the grim significance of his comment. The "Southern Cross" and its crew were to be found unharmed within the fortnight. Allegations were soon made that Smithy's forced landing was nothing more than a publicity stunt contrived with Anderson.
The tragic aftermath of the loss and subsequent rescue of the "Southern Cross" led to an official inquiry, in which Kingsford Smith and Ulm were exonerated. The incident was quickly dubbed the Coffee Royal Affair by the press of the time.

In Search of the Southern Cross
Keith Anderson - friend, colleague and sometime rival of Kingsford Smith - was convinced that the search was concentrated in the wrong area. On 4 April, Anderson and his mechanic Bob Hitchcock flew out of Sydney on a privately sponsored search for the "Southern Cross". His courageous venture was hastily prepared.
The Kookaburra recently purchased with the aid of a generous gift from Kingsford Smith, was barely equipped for such a hazardous trip. The compass was faulty, there was no radio, little food and water, and a limited tool kit. When Anderson took off from Richmond near Sydney on that still grey morning the "Kookaburra", laden with extra fuel tanks, was 180 kilograms overweight. The aircraft developed engine trouble south of Oodnadatta SA, and after a forced landing Hitchcock was able to adjust the loose valve tappet with a chisel and the end of a corkscrew.
At Alice Spring Anderson received advice a telegram the Department of Civil Aviation not to go ahead with his flight. He ignored the instructions and at 0735 on 10 April the "Kookaburra" took off from Alice Springs. It was still grossly overladen with fuel and its crew's supplies consisted of only 3 litres of water, a quantity of sandwiches and some cake. The men had neither axe nor spade and few other tools. 
The "Kookaburra" headed north, following the Overland Telegraph Line as far as Woodford Crossing, 160 km from Alice Springs. Anderson then decided to divert across country to Mt Davidson and follow a straight line to Wyndham. Due to navigational error Anderson drifted to the east of his proposed course and south-east of Wave Hill station the aircraft again developed tappet problems. Anderson made a forced landing 128 km from Wave Hill, causing minor damage to the aircraft. Hitchcock was again able to repair the engine, but the thick scrub and loose sand thwarted repeated attempts at take-off Anderson and Hitchcock attempted to clear a runway in the scrub with their bare hands and a penknife before lighting a fire in an effort to clear the scrub and attract attention.
A rough diary scribbled on a section of the rudder fabric indicates that the men were still alive on 12 April but that all attempts at take-off came to nought due to increased debility from thirst heat flies and dust. It also records that the men had no water to drink except solutions of urine (mixed with oil, petrol and methylated spirits).

In Search of the "Kookaburra"
On 12 April 1929 (the same as the last date scribbled on the rudder fabric of the "Kookaburra") a de Havilland search plane, the "Canberra", sighted the "Southern Cross" and sent the Message "Found, Found, All Safe". While the nation rejoiced at Smithy's rescue the relief was tempered by the realisation that the spotlight of tragedy shifted to Anderson and Hitchcock now long overdue at Wyndham. However while the aviators struggled for survival in the Tanami Desert a bureocratic struggle was developing over their rescue and valuable time was lost before a search was mounted.
An RAAF contingent of five planes, in addition to the "Canberra" and  a Qantas aircraft was dispatched to search the Tanami Desert. On 21 April, Captain Lester Brain, the pilot of the Qantas aircraft spotted a column of smoke south of Wave Hill. On close examination he observed the "Kookaburra" and saw a prostate figure under the starboard wing. He dropped water and radioed the location to the RAAF searchers.

The Thornycroft Expedition
Under instructions from the Air Board a ground party led by Flight Lieutenant Charles Eaton left Wave Hill for the "Kookaburra" site on 24 April. Guided by three RAAF aircraft the ground party reached the site on 29 April. There they found the bodies of the two aviators. Both had died of thirst and exposure. Hitchcock's body was found under the wing and that of Anderson several hundred metres from the aircraft. The bodies were buried where they lay and the RAAF planes dropped wreaths at the site. 
Although Eaton had planned to fly the "Kookaburra" back to Wave Hill, the ground party were running short of water and it was decided that they did not have time to extend the runway. The party then returned to Wave Hill. The tragedy of Anderson and Hitchcock dismayed Australia, and under public pressure, the Government ordered that the bodies be brought back.
A new ground expedition equipped with an A3 Thronycroft four wheel drive truck set off on its grim task. On 14 June the bodies were exhumed and placed in special lead lined coffins. Although the party were unable to retrieve the "Kookaburra" they cleared a runway so that it might be flown out at a later date. The party were running short of fuel, and as a safety precaution  they drained the fuel tanks of the "Kookaburra" and returned to civilisation.
Keith Anderson was accorded a state funeral in Sydney and Bob Hitchcock, at his wife's request, was buried at a quiet service in Perth.

In Search of the Night Parrot
Unlike its crew, the "Kookaburra" was destined to remain in the Tanami Desert. It was soon realised that the recovery costs would far exceed the commercial value of the aircraft. With the passage of time the cleared and burned scrub regenerated and the aircraft was swallowed up by the desert, suffering the ravages of bushfires and shifting sands, but the "Kookaburra" was not to be forgotten.
The little aircraft remained lost until 1961 when the remains were found by a surveying party, this led to a resurgence of interest in the "Kookaburra" story. Several privately sponsored searches were conducted, an official ground and air search (filmed by a crew from the Australian Broadcasting Commission) was mounted in 1975, but was unsuccessful. It is now known that the ground party passed within a few hundred metres of the "Kookaburra" remains. In 1976 it was classified by the NT administration to prevent its removal from the Territory.
The remains of the "Kookaburra" were eventually found by Sydney aviation enthusiast Dick Smith. His first search in 1977 involving a search party equipped with four wheel drive vehicles and a helicopter failed to locate the site. Not deterred, he returned in 1978 and on 31 August 1978 after six day's searching he located the wreck from his helicopter. He returned to Wave Hill and reported the find to Dr Hinton of the Northern Territory Museum before signalling Sydney of his find with the words: "The Night Parrot has been found"

The Last Journey
Within the week Dr Hinton led a ground party to retrieve the wreckage. On recovery the remains were transported to Alice Springs while a decision was made as to its display. The Kookaburra hit the headlines again when in 1980 its engine was stolen from Alice Springs, only to be found dumped on the helicopter pad of a Sydney television station four months later. It was taken with the wreckage to Darwin for conservation work and was then set up at a permanent display at Alice Springs in 1982 only 150 metres from the runway from where it took off for its final fateful flight. The Kookaburra Memorial is situated in Memorial Drive, Alice Springs