RCU Forums - My US 40 mods

After an awesome inverted flat spin crash with my US 40 using a Webra 120, I decided to modify my US to make it light !!!

First, ALL ARF's I've seen/flown are EXTREMELY heavy !!! With this in mind, I uncovered my stick and what I found was that a lot of superfluous wood was used to build this ARF kit. Also the used wood is probably the worst quality available to man kind :(

The mods I did to my stick follow:

a) Removed all the excess wood and replaced all the fuse-planking with contest-grade 1/8" balsa wood

b) Removed all the cap strips (inside the wing)

c) Made holes all over the fuselage & wing

d) Made the landing gear look like a gruyere cheese (drilled tons of holes on it)

e) Replaced the stock wheels with a pair of small sponge-like wheels.

f) Replaced the engine-mount with a nylon one

g) Placed the rudder & elevator servos in the back (hence removed 1 oz of lead)

h) Replaced the rudder, vertical tail, elevator & stabilizer with a custom, much bigger / lighter ones using contest-grade balsa. Ha, both the stab & rudder weigh less than the original vertical tail :)

My modified US weighted in at 4.05 lbs RTF with fuel. I could have probably gone 0.5 lbs lighter, but I ran out of contest-grade balsa :rolleyes:

Needless to say, the OS 50 SX-H w/macs tuned-pipe provides much more power than I ever dreamed of. The plane did not need any runway at all (it was hand-launched and landed completely vertical) and it tracked excellently through all the maneuvers I put it through. Harriers, hover and back-wards landings (with a little breeze) where all done with ease, and while hovering, the throttle stick did not go over 1/2 except for bailing out!

It looks like the rudder mod really made a difference for knife-edge & rolling harriers

I tested for over-all kit strength by doing several blenders & full throttle dives + full elevator 30' above ground and the plane survived them all.

One interesting issue is that I removed approx 2 lbs of weight by modifying the kit ONLY (I.E. no micro-servos nor micro-receiver where used) and the plane seems as sturdy as before !!!

I just hope H9 plans on making "better-quality" kits by using contest-grade balsa and refrain from using plywood-like balsa (in terms of weight/strength). A bigger engine is NOT always the solution to your problems, but less weight will ALWAYS be an answer.

FYI: There is much more vertical thrust in my modified US 40 using an OS 50 than there was with the original stick + Webra 120 + 2 oz of lead for balance !!!

In conclusion, when ever you think adding a bigger engine will make your plane fly better, its best to think the right way; remove some weight :D