ORIGINAL: AmishWarlord
A guy in my club had a Great Planes Cherokee that did the same thing. That plane would stick to the ground like a F1 race car. Must be some thing with the wing incidence.
This rubber plane from 1936 had the same trait. When the motor was fully would and the model hand lunched it would fly as normal. However if it was lunched from the ground it would roll on the ground for 3/4 the motor wind then leap into the air vertical until the motor unwound then stall and crash.
When a tri-geared model tends to stick to the ground, it's usually the landing gear setup. The fuselage has a somewhat nose-down angle when the plane's on the gear. This tends to hold the model down until enough airspeed's built up that the elevator will work. Usually, then, the model will balloon into the air very quickly, and a touch of 'down' will be needed to put the plane into the proper climb attitude.
If the rubber model had a lot of downthrust, it's entirely possible that the relationship between landing gear position, wing incidence, and the amount of power produced early in the run caused the model to not be able to nose up enough to get into the air. As power bled off, the downthrust effect would have lessened. When hand-launched, the model was likely able rotate to the proper flying position, something prevented by the relationship of the landing gear to the rest of the model, when combined with the motor's downthrust.