Max weight for a Ryobi?
 

Max weight for a Ryobi?

Thoughts of a twin Ryobi have been bothering me for months. Don’t build worth a hoot so it will be necessary to find and modify an airframe already built. Knowing the all up weight of your single with a Ryobi would help to establish some design parameters.

What is the all up weight of your airplane with Ryobi?

Thanks.

Bill

RE: Max weight for a Ryobi?
 

Maybe a better question would have been:

Will a Ryobi pull a 20-pound airplane with 28oz/sq ft wing loading? I rechecked the weight and wing loading on another Ryobi project and have become concerned.

Bill

RE: Max weight for a Ryobi?
 

Hi Bill,
We don't know what type of airplane or airfoil you are using. If you are using a flat bottom wing with a strong Ryobi you should be fine. If you are using a weak Ryobi or symetrical airfoil you will be marginal at best. If the engine will spin an eighteen inch prop in the seven thousand rpm range I would consider it a strong engine. Spiiining a sixteen inch prop in the high six or low seven range might cause problems. If you put one strong Ryobi on each wing it would add six pounds and give a wing loading of about 35oz./sf. The power loading would be about 1/3hp per pound. This would be minimum aerobatics capable. If the 20 lb plane isn't a floater, you should look for a stronger motor like a Homey 33cc Bandit chain saw. Easy conversion and lots of power.

Dave

RE: Max weight for a Ryobi?
 

Thanks Dave,

The twin disease is bad and even an occasional fix doesn’t help.

I have a hand me down pattern airplane in reasonably good shape with sheeted foam wing (1580sq. in. or so). Original plan was to use a Ryobi and fly it as a single. I had already mounted the engine. While checking to see if it might be used as a twin the wing loading was checked. Surprise the airplane will weigh will be just short of 20#. Oops maybe a Ryobi won’t fly it at 20# and 28oz/sq ft. Engine far away from fuselage for prop/gear clearance, not much ground clearance along with 35oz/sq ft wing loading gives serious concern as a twin. It would probably work great with three 90 two strokes on glow.

So far my twins have been conservative and successful. With enough power 28 would be OK. But 35 in a twin is not conservative. Good news is the wing would be plenty strong.

The other airframe being considered is a 96” Stick with symmetrical wing and dihedral. It is 35# and flying with a 57cc gas engine. Rough calculations indicate that as a triple it will require 2# in the tail and as a twin 1 1/2# will be required in the nose. A triple would be in the 47# range. I didn’t build the overweight monster but have been flying it for years.

Thanks again.

Bill