Guy's I am gonna build a Sky Ray 1/2A  for our half " A "  day and I want to use power pro 20# test lines in 40' length using a Cox .049 Baby B engine, will this work and if not please advise and suggest..  Thanks

good plane...week engine (typically)....old guy I highly recommend a Medallion with screw in back plate Radial mount and simple balloon tank

line length dictated by plane weight, engine authority, prop, line drag*, and local winds

long draggy lines will turn a light under-powered plane into the circle

 Al, could I get some more info such as power plant,model weight and specs, as well as other info that you will share, and thanks...and line size..

Legs-in-boots,

Another data point:

SIG Baby Skyray with added gussets along wing joint (upper surface) and stab. Added landing gear (1/16" wire) and one inch Williams Bros wheels. Rubber tires, not foam. Monokote on wings, stab and elevators. KlassKote on the rest.

Cox product engine (twin port with the dual slit exhaust), standard glowhead, Baby Bee tank. No mods, no hop-ups. Mounted upright.

Weight is 184 gm (6.5 oz.) less propeller. That includes a whopping big fender washer (1-1/2" diameter) for tip weight, as I use the plane for ab initio training of kids I drag out of the parking lot.

I fly it on .008x42' lines using a Renger/RSM 1/2A handle that works well. The long lines are good for slower rotation for beginners. It will wingover and loop if not too breezy. It will fly mostly straight and level in a pretty good breeze with this combination. I might take a couple feet off the lines and reduce the tipweight if I was trying to do much stunting.

I think your choice of 20 lb test Spectra is a good one.

My Skyray has had a LOT of beginner flights, and is still capable....

Good luck with yours!

McDivot