I did the same thing with my 360 after performing some maintenance on it.
Luckily my prop was horizontal and the only damage was to the cowl paint,
the outboard main gear doors, nose gear door and the air box..  The irony
was that I had fitted a switch to inhibit gear retraction until a speed of
75 knots was reached BUT IT WAS NOT CONNECTED!!!!!!  It is now.  A fellow
builder was using this switch which is used to control water level in Sears
washing machines.  It is adjustable and is very easy to set.  You connect it
into the line from the pitot head in the vicinity of the ASI.  Blank off the
pitot head and  using a T  apply pressure to the pitot line by blowing
gently and I mean gently until you reach 75 knots, or whatever you decide is
good for you.  Pinch off your test line to retain the pressure and using a
meter or a test lamp adjust the switch until it closes.  Do it two or three
times to ensure that the switch is closing at the correct speed.  Seal off
the switch adjustment and fit an over ride switch across the contacts. If
for any reason the switch fails to operate you can close the over ride
switch and still be able to raise the gear.  Sears part# 26C110 and 660107,
cost $25 or so.  Works like a charm. Do not forget to remove the plug from
the pitot head and you test T

Ian Crowe