chikinman

My Feedback: (4)

I have a .40 sized, low-wing plane that has an indented firewall. Since I chose an oversized engine, I had to install a 2x4 block between the engine and firewall. This in effect changed the CG for the plane. Now, the engine is so heavy and forward-protruding, that any little bump in the runway causes the plane to tip forward.

The instructions say CG is 3 1/4 inches from the forward wing. How do I make adjustments to get this plane leveled?

Thanks in advance.

JS

edge_fanatic

My Feedback: (4)

You might consider adding a very small amount of weight to the botton of the tail, under the rudder...

There are stick-on weights that might work. Just make sure you put them on nicely...When I used those kinds of weights, I glued them on, the ensure that they didn't fall off in flight.

What engine did you end up using? On which plane?

chikinman

My Feedback: (4)

Thanks for the tip edge_fanatic.

I put a YS 91FZ on a .40 Great Planes Texan A-6 ... I love to take off in 12 inches!

I have placed some weights on the tale, however won't the CG change b/c the engine is now further forward? I've got 1 package of stick-on weights on it already and it still wants to tip forward!

FHHuber

Sounds like you may need 4 or 6 oz under the tail...

A .91 4-stroke on a .40 size plane is right on the edge of insanity.

kdheath

Trouble is, it's always going to be a 900mph bowling ball with that much engine weight on the front of it. Adding enough tail weight to balance it will only make the whole thing heavier and harder to fly. Estimating the YS at 12 ounces heavier than a good 46, plus 4-6 ounces minimum to balance it, you're easily a pound over the design weight. That's a bunch on a 40 size airplane.

jettstarblue

Go ahead and ad the 4-8 oz. of weight you need to the very end of the rudder so it acts as a counter-counter balance.
Get some 25% nitro for that engine you got so you get maximum performance, that way you'll still get off the ground pretty darned quick. (12-16"))
Don't worry if you crash, 'cause the "2X4" will absorb most of the impact, the engine will absorb the rest.
The wing loading may be a bit high, but it sounds like you got the high performance pilot thing down pretty well.
Make sure you video tape the first flight.

Jetts