Need your help fellows - fighting elevator on final

[Terryscustom]

In our case it created an up down fight while slowing down to land. It could not find a comfort zone until it was almost stalling. It also had a bad pull to the left under full power that was unaffected by changing thrust angles. When we changed to a prop diameter one size smaller it helped everything.

This raises a good point since we are talking about trim and all that good stuff. One thing you will find is that the larger the plane and larger the prop the plane will normally yaw to the left at full throttle. It does it all the time, but is visible on an upline. What I do with all planes is trim the rudder from up high, throttle at idle and straight down line. Trim the rudder for straight down. Now you set up a Throttle to Rudder mix so that at full throttle you have about 2% right rudder. Tweak that amount after testing but 2-3% seems most typical. Now you should be able to do a full throttle up-line and it should be straight, chop the gas and it should continue straight up, turn and power off it should be straight down.

This is a handy mix that helps the entire flight envelope. @witchfingers is correct that the larger the prop this seems to be more pronounced. I've seen people change thrust angle on the engine after noticing this and then they find out that the rudder is all out of wack and does not trim properly.

Anyway, just another handy tip to make your plane fly nice and straight.

 

[Hoosier06]

Taken from the manual of the Hanger 9 1/3 scale, 97 inch wing span, Cap. I have one downloaded in my computer if you need it.
Section 14: Balancing the Model

Correctly balancing an aerobatic model is critical to its performance
and flight characteristics. Checking the balance on giant scale
models is best done with two people.

Step 1.
On the top of the wing tips, measure back 4 1/2 and 5 ¾ inches
from the leading edge and mark both places with a felt-tipped
pen. This is the recommended center of gravity (C.G.) range.

Step 2.
Fully assemble the model. With a helper, lift the
airplane with your index fingers and find the balance point. The
balance point (C.G.) should lie between the two marks on the
wing tip. If not, add the necessary weight to the nose or tail to
obtain the correct balance

 

[Judge]

Like anyone is going to pay attention to the instruction manual!!

 

[Hoosier06]

Yeah I suppose when a guy knows it all he does not need to read the manual. That Cap did not need special settings. We flew them with DA 100's and ZDZ 80's. It flew like a Cap flies. Landings were never easy. What the owner describes was common with that Cap. It did not need the motor moved in any direction. Use the recommended CG as a starting point and do the 45 degree upline to refine the CG. If you can't land it practice, there is no magic in the settings. As mentioned earlier a slight bit of down elevator mixed with low throttle would help. If you really can't get it down "fly it down" meaning more speed on landing. Not everybody liked the Hanger 9 Cap and resales were popular when that plane was being sold by Horizon.

 

[IMAC FANATIC]

I 3rd the "check the wing to stab incidence".
every bit of the Goldberg/trim app will be off if this isnt checked, youll be mixing to no end without verifying they are zero-zero or at least match the recommendation of the instructions.
If your radio allows, set a take off- landing mode for rates , in this mode remove the throttle to elevator mix as throttle bumps will cause porpising every time the throttle is moved.

 

[skunkwurk]

Taken from the manual of the Hanger 9 1/3 scale, 97 inch wing span, Cap. I have one downloaded in my computer if you need it.
Section 14: Balancing the Model

Correctly balancing an aerobatic model is critical to its performance
and flight characteristics. Checking the balance on giant scale
models is best done with two people.

Step 1.
On the top of the wing tips, measure back 4 1/2 and 5 ¾ inches
from the leading edge and mark both places with a felt-tipped
pen. This is the recommended center of gravity (C.G.) range.

Step 2.
Fully assemble the model. With a helper, lift the
airplane with your index fingers and find the balance point. The
balance point (C.G.) should lie between the two marks on the
wing tip. If not, add the necessary weight to the nose or tail to
obtain the correct balance

I followed the steps, I've flown mostly Caps and Sukhois, so I agree with the comments related to the tendencies/characteristics related to the design. I still love Caps, it's part of the allure to the model. I've flown light ones, heavy ones, some that tumbled like nothing else and others which were a bear to land. I currently have a smaller Cap which I have spent a lot of time trimming and is a pleasure to land. I just can't avoid drilling down through all of the possible variables until I am certain there is no more tuning I can do in order to improve negative tendencies.

The rationale for the thread was to avoid making unnecessary changes, like thrust angles, when potentially CG might be the issue. Even though I was within range, and in-flight tests appeared ok. I decided to pause where I was and poke around on the site and solicit the crew's thoughts and consideration. I was looking for troubleshooting inspiration in case I might have missed anything in my initial testing and assessment. As expected, the fellows on the site have been great, and I'm very thankful.

Thanks guys...

sc

 

[sweetpea]

Let us know what ends up working

 

[skunkwurk]

Let us know what ends up working

Will do, I made a CG adjustment, will test on Friday.

oh yes, I had to pull out the old GP CG machine to test inverted on my own, worked quite well...

sc

 

[sweetpea]

Wait....you didn't say you were flying a 3 blade....that changes everything

 

[skunkwurk]

Wait....you didn't say you were flying a 3 blade....that changes everything

nice...