<font color="#000000"><font size="2"><font face="arial,sans-serif"><font size="2"><font size="2"><font size="2"><font size="2">I'm having lots of fun converting weed wacker engines. I<font size="2">'m hoping to</font> fly with them this spring.
<font size="2">To <font size="2">get into the air, I was thinking of using my newly acquired Joss Stick <font size="2">that currently has a
<font size="2">Super Tiger 90 on it. The Stik has 877 sq. in. of wing and weighs under 9 lbs. with an est. wing
<font size="2">l<font size="2">oadin<font size="2">g of approx. 23.5 oz/sq. ft. I was thinking of replacing the engine with a 21cc wacker engine
<font size="2">(7200 rpm with 16x6 MAS prop). But this brings the est wing loading up 30 oz/sq. ft.
<font size="2">Think this plane will get off the ground? Should I scrap this idea and make a bigger plane
<font size="2">like a SPAD for my wacker engines? I<font size="2">'m trying to learn to build lightweight <font size="2">after coming
<font size="2">from a live steam hobby where adding an<font size="2"> extra 100 lbs. to a model steam locomotive for
<font size="2">more traction is not a big deal.
<font size="2">Your input <font size="2">and guidance will be greatly appreciated, t<font size="2">han</font>k you.</font></font></font></font></font></font></font></font></font></font></font></font></font></font></font></font></font></font></font></font></font></font></font></font>

At 30 oz's per sq in" puts the wing loading up around where some of the war birds fly at. You also have to consider the CG with the heavier engine hung out there in front, Has that occurred to you? you may end up adding more weight yet to achieve the correct balance point.
Myself I would look at a larger air frame to accept the heavier engine's.

The Joss Stick is on the heavy side anyway

Usually the guys shorten the nose of the plane some to compensate for the weight up front with the engine.
Usually for a .60 size plane, they are using .60 on up two stroke engines and .91 on up four stroke engines, with the .91 to 1.25 size four stroke engines being popular. With gas engines many people were going with something like the DLE 20cc gas engine. So using a 21cc converted trimmer engine shouldn't be a problem. There are several people at our flying field flying 20cc gas engine powered stick style planes already.

I have converted the Great Planes Big Stik numerous times with very good success, but it has nearly 1000 square inches of wing area. (966?) I usually put the lightweight and powerful Echo 24cc engines on them, with electronic ignition to lose the weight of the flywheel, etc. They fly great. My brother has one with a Stihl 20cc on it that I converted and he loves it. The heavier Joss Stik with less wing area would be marginal I believe. It would definitely fly, but it would be heavy...

Then there's the Giant Stik.... I have one of those with a 48cc twin I made on it, a smoke system, etc. Still floats like crazy. Always amazes me how long it will glide with power off.

AV8TOR

Smaller tank on the CG (8oz), two servos in the tail and a light weight muffler. Boom no problem.

Upgrade to a light weight electronic ignition for a new experiment.

I modified an Ugly Stick 60, with 4lbs of lead weight on the CG. The idea was to learn to fly a plane with high wing loading. I had recently finished a P-51 with a very high wing loading and used the Stick as as a learning tool. Good results, Stick took it with no problem. Good luck, red

I suppose the real question is here, is what type of flying do you want to do?