Villa

I fly a flying lawnmower and believe the flying characteristics are similar. After not getting off the ground the first time you probably held a lot of up elevator the second time. When this is done you MUST expect the plane to suddenly lift and try to go vertical. You must be ready with lots of down elevator if this happend. My mower is very pitch sensitive. My guess is your's should get off the ground at a little higher speed than most planes with a normal amount of up elevator at rotation. If this is not happening look for problems with engine, prop, CG. Call the manufacturer for advice before you launch the second one.