Acrowot Foam-e Incidence

[Stevo]

Hi Fellas,

One for the techies.

Looked at my Acrowot Foam-e. The one thats always climbing

Anyhow, flew it last week in heavyish winds. With the wind - quite nose up.. slow turn 180 degs. and now into wind. back off the power a little so speed over ground quite slow. What does she do? Climb like her life depended on it. Right up!!! Repeated it time and time again. Flew most of the session with quite a lot of down input.

Ive expermimented with CoG with no real conclusion (see my other thread) but decided to investigate further.

Put her on the bench, with a better motor installed. Reset CoG to 75mm - bang on.

Placed incidence meter on the wing and propped up the tail until 0 degrees.

Put meter on tail without moving the A/C. 2.5 degrees, thats sloping down at the front of the tailplane and up at the back.(not sure if that's positive or negative!)

Fetched up my spacewalker for a comparison. 0 degrees both wing and tail. I know diferent A/C have different design parameters of course but I used this to check my methodology.

Comments any one? I simply want this to go faster, or indeed climb a little when I throttle up.

I did look at an acrowot restoration thread on here and it stated a parallel incidence wing and tail.

Over!

[Stevo]

OK so I made some enquiries over the WWW.

Typical incidence is around 0.5 degrees, so made modifications to the tailplane (to do this to the wing would need really hacking the fuselage about!) and it's now 0.5. Before I did this I triple checked the 2.5 degrees I stated earlier.. yes it was

**LINK**

I can out this back if the need arises...

Now if it stops raining I'll go and fly it!

[Bill_B]

That's +2.5° incidence which does seem a bit excessive. I'm not sure what sort of incidence meter you have, but did you measure the wing angle at the root (inboard of the ailerons), lock the elevator and support the flimsy tail?

I just measured the incidence on my Foam-e and it's +1.25°. As the model is foam I would expect some variance in measurements, but not as much as you seem to have.

BTW, have you checked the motor mount for security and is the down thrust reasonable?

[Stevo]

Thanks Bill.

Understand what you are saying... I was quite concerned....

The incidence meter was a Great Planes one, tailplane/elevator was locked dead straight and fully supported - and all angles measured at the root.

Thanks for measuring your own Foam-e for me - that gives me a good comparison.

Steve

[Stevo]

Motor mount is secure, and down thrust is reasonable (as is side thrust but not an issue here).

Bear in mind it went right up at low throttle - but in high wind. 

 

Understand the variance on a foamie.. my two year old WOT4 foam-e needed more and more rudder as the months went on... the fuselege was shaped like a banana! 

 

Edited By Stevo on 06/09/2013 18:42:35

[Bill_B]

Rather than invasive butchery, how about carefully warming the rear fuselage with a hair dryer and then keeping some 'down' pressure on until it cools, that could maybe solve the excessive incidence problem.

Failing that, cut a thin slit in the bottom of the fuselage and insert a 12" length of 3 x 0.5mm carbon strip, secured with thin CA when you've achieved the correct incidence. Tricky to achieve perhaps, but manageable with care.

 

Edited By Bill_B on 06/09/2013 18:56:24

[Stevo]

OK!

1.5mm removed from extreme rear of the tail plane set and the whole mounting syste re-engineered to hold it all tight. reset CoG and all sub trims and movements to defaults.

Still windy today and took a chance but got someone with more hours on the clock to iron her out. He did this with 3 clicks of up and two of right. I took over and flung her around (or was it the wind?).

Full bore into wind and she climbed - around 5 degrees... inverted she took around 1/4" of forward movement of the stick to stop her dropping. Mission accomplished I think?

Hopefull less windy Friday, but rain forecast...