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Recommended weight on tail

YKnot

I'm New Here
What is the recommended weight on the tail of a Harmon Rocket II? I just emailed John; haven’t heard back yet.

Thoughts? Friend has 41 pounds on his Rocket. Felt very solid.

Thanks
 
Are you asking what a scale would register if the TW was placed on it? If so, are you talking 3 point, level, or other? And if so, are you looking to do W&B calculations or just general info?

In the end, the weight on the TW is a function of gear geometry, total empty weight, and proper CG envelope. The weight on the tail tire is a "result", not a target.
 
the weight on the TW is a function of gear geometry, total empty weight, and proper CG envelope. The weight on the tail tire is a "result", not a target.

This ^^

I'm building a biplane and the "target" was 50-75 lbs of tailweight in level flight. Mine came in at 66. However, mine has a pretty high deck angle (12 degrees) and the resulting tail weight when sitting on the ground is 105 lbs. Certainly higher than I was hoping for but I'm happy with all my other numbers so we'll see how it handles when I fly it.
 
Weight on the tail means nothing if there’s variances in geometry.. I think Toobuilder was saying the same thing. The real question is where does the CG end up?
 
And to add...

I'm not sure it means nothing. I think it means nothing in flight but ground handling is a different matter. As I told a friend...I'll just taxi to my hangar with the tail in the air like the cool kids.:cool:;)
 
The rule of thumb is 5% of the empty weight of the aircraft. Harmon’s because of main gear placement can’t reach that number and as a consequence have a very high rate of nose overs. You can contact Vince below and the F1 group has a fix with a new engine mount. I highly recommend this change. If you were to have a nose over you might find the aircraft uninsurable going forward. This issue is one of the main reasons for high Rocket insurance.

http://f1aircraft.com/team-rocket-home-f1-rocket-f4-raider/
 
He is referring to my plane. Rocket #1. It is weighed in level flight attitude, has 41 lbs on the tail with an empty cg of 85.77. It had 19 lbs when I first got it. Finally got john harmon on the phone and he said throw a couple cases of oil in the back and go fly it. He said 30-35 lbs is about right with higher weight being much better. I installed a 4.5 gal smoke system tank, changed the rg-25 battery to an earthx 680 and added 20lbs of lead weight on the elevator spar. With all the changes, i have 41 lbs and it flies perfect with no nose over tendency unless rpms on run up is above 2100rpms. Then she starts getting light on the tail. Empty weight currently 1275lbs. Almost impossible for overload out the back of the cg envelope.
 
I have to wonder what your CG was with the 19 pound TWW? If you can add 20 pounds on the stab, a case of oil in back AND still not be able to go out the back of the envelope when fully loaded you must have been WAY forward. Do you have a lead propeller?
 
No lead prop. Just stock 80” hartzell. My airplane sitting on the scales, leveled at the side rails, with empty smoke tank and 20lbs lead on the tail.
 

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