Just getting back into things, and want to know, if anyone knows (i'm sure someone out there does) What speeds do the planes reach before take off, .40 engine + high wing trainer, plane weight 8lbs approx,
hope someone can help, thanx

its just going to depend on the plane, the airfoil/weight/drag of the floats/ect
but at eight pounds (heavy for a .40 sized trainer) id guess maybe 25-35 mph
my 5.5lb trainer will take off at about 15-20 mph (on land), its a spad so its a little higher than some.
the tower trainer rtf, im guessing will fly at 15 mph, maybe less.

what is the reason behind this?

I said trainer, i mean its a trainer style design, made from corrugated plastic of sorts, weight is about 4.5lbs with the floats (not 8lb, my mistake) -3.5lb should help with the take off speed

A stock LT-40...high wing trainer, trike gear....will come off the ground at around 30 MPH and stall at about 28 MPH....full power level flight at around 70 MPH....I don't remember where I read that but it has stuck with me over the years.......I sold a modified LT-40 to my son in law's dad, he's a retired cop.......with a radar gun he was clocked at 72 mph in level flight.....kinda validates what I read

ahh ok, its a spad. i would guess would be around 15mph depending on the size of the wing and the prop you are useing.
my 48in, 5.5lb spad will takeoff at about 18-20mph.

I guess I'd ask how long is your runway to get 8 lbs moving up to take off speed?

You should be able to get an 8 Lb trainer style airplane powered with a 40 or 46 using a 10/11X 6 or 7 prop in the air in less than 30 or 40 ft I would think....