On Thursday, June 28, 2018 at 11:44:07 PM UTC-4, Ron wrote:
I'm thinking of making a motorcycle ramp 8 ft long & 3 ft wide with 3/4 inch
plywood to load a 600 lb bike on a car hauler trailer. Will the 3/4 " plywood
hold the weight?


Use the Load Span tables found here to determine the best type of plywood and
on-center measurements for the supports required to fit your application:

http://www.pacificwoodlaminates.com/...SpanTables.pdf

OTOH, why are you making a ramp from plywood?

You can get a 7.5' folding aluminum ramp rated at 750 lbs for under $60 he

https://www.discountramps.com/motocr...mp/p/AFP-9012/

Probably safer when wet than plywood.