Leggtech69

I have a low wing Lancair ES EP. Instuctions say to place plane upside down on CG 2" fron leading wing edge to balance plane. when i do this and turn plane right side up it is extreamly tail heavy. Am I doing something wrong? Please help I am eager to fly this plane but if balance is off I dont want to put it in the dirt on maiden flight.

fmw

How do you know it is tail heavy if you haven't flown it? My advice would be to follow the instructions to the letter and adjust only after you've flown the plane.

Leggtech69

it is tail heavy when we turn it over on the cg machine, up right like it would be flying

Leggtech69

I mean that t when i sit it on the ground the tail touches the ground, i dont think a nose wheel should be in the air just sitting there. LOL

Flypaper 2

Looking from the side with the tail up where it should be, how far back from the leading edge are the main wheels?? They have to be behind that 2 in. mark.

Lnewqban

Make sure that:

1) You are measuring the location of the CG on the top of the wing on both sides of the fuselage. The balance point, located 2" back from the leading edge of the wing, should be measured at the fuselage sides.

2) Your nose landing gear is not placing the nose too high. When supported by the gear, the central line of the fuse should be horizontal or slightly nose-down.

3) The point of contact of the main landing gear is behind the CG location (extended vertically).

Check these threads out:

http://www.rcuniverse.com/forum/m_94...tm.htm#9458568

http://www.rcuniverse.com/forum/m_95...tm.htm#9527315

http://www.rcuniverse.com/forum/m_91...tm.htm#9194804

http://www.rcuniverse.com/forum/m_86...tm.htm#8611378

Wish you luck!

Leggtech69

THANKS FOR THE ADVISE AND SORRY TO REPORT WE HAVE DONE ALL THIS. THE ONLY THING I CAN SEE THAT M9IGHT BE IT IS THAT WHEN THE PLANE IS UPSIDE DOWN ON THE CG MACHINE I AM PLACING WEIGHTS ON THE BOTTOM OF THE PLANE AND IT BALANCES PERFECTLY BUT WHEN I INSTALL THE WEIGHT IN THE SAME PLACE INSIDE THE PLANE AND SET IT ON THE WHEELS THE TAIL IMMEDIATELT DROPPS TO THE GROUND. I HAVE CHECKED ALL MEASUREMENTS AND DOUBLE AND TRIPPLE CHECKED. I HAVE NEVER HAD A PLANE DO THIS AND I HAVE BEEN FLYING FOR OVER 20 YRS? ANY OTHER SUGGESTION?

Lnewqban

As long as you keep the weights at the same distance from the CG when you re-locate them, the balance should remain the same.

As you know, with the location of the CG being in the closest to the tail, the position of the back wheels should avoid that the plane could end up in a nose up attitude, with the tail on the ground and unable to return to level by itself (due to a gust or extreme flaring).

This could happen only if the vertical line coming down from the CG touches the ground behind the wheels for that attitude.
The 0.05MAC distance is a safety factor that places the wheels beyond that critical point.

On the other hand, if that distance between the wheels and the CG is made too big, that will make the take-off rotation of the model around the back wheels too hard on the elevator, when the fuel tank is full and the CG is located toward the nose.

Note that is important to have the horizontal-vertical location of the CG.

Now, for normal horizontal attitude, it is recommended to make the nose to point down about 3 degree, in order to avoid any bouncing tendency during landing.

Leggtech69

Thanks to all who replied, what we found was indeed the mian landing gear attatment point was in front of the cg mark I am attempting to relocate main landing gear or possibly swing them back behind the CG mark to correct problem. I believe this to be a flaw in design but am not a areonautical engineer so??????? thanks for all your help will post how first flight goes as soon as the wimg dies down.

Leggtech69

sorry that was,,,,, as soon as the wind dies down.

Lnewqban

You are welcome.

May be replacing the original wires of the main gear for a little longer (in order to keep original height) new pieces that are bent back until the point of contact with the ground is as recommended in the schematics.

Again, best luck!

Lnewqban

PM sent.

Also check these RCU member's reviews:

http://www.rcuniverse.com/product_gu...fm?kit_id=3861