My US 40 mods
07-10-2002 | 06:45 AM
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From: Houston, TX
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
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
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
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
11-11-2003 | 09:23 PM
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From: Lansing, MI
RE: My US 40 mods
Doing the "Buy a Bigger Engine" thing, and not trying to lose weight also, reminds me of. People will go into a fancy bike shop, and pay like $200 more for a bike that's 3 pounds lighter, when they are 30# overweight themselves... - Joe
- Joe
