Piper PA-25 150 Pawnee

[ramses]

The aspect I find most challenging with an F4D indoor scale model is keeping the weight—and especially the wing loading—low. I have build a Fairey Firefly and a Spitfire for F4D this year. Although the Firefly shows good promise, it stays with that promise and i haven`t been able to let her fly succesfully indoors...

I was texting with Richard (Crossley), and he challenged me to build a plane with a maximum wing loading of 10g/dm². He suggested a plan—I think it was an Aeronca from Outerzone—but I preferred to try his Pawnee design.

The goal is a maximum flying weight of 67 grams to get a wingloading for the Pawnee of max 10g/dm2.

Cheers, Ramses

[Piecost]

Hi Ramses,

I see from the other forum:

https://www.modelbouwforum.nl/threads/piper-pa-25-pawnee-rubber-power.295987/

That you have flown the unpainted model. I am impressed in your confidence to perform initial flights in a breeze over short grass! The model certainly flew well straight off the board.

The model looks up to your usual high standard of workmanship. How much mass and additional noseweight do you expect the paint to add? Any details of the painting process would be appreciated.

Can you add some thoughts about building light? Wood selection, for example.

I employ 5 or 6 lb/ft^3 balsa for tailplanes, preshrink the tissue before covering then still need to sandwhich the surface between foamboard jigs to prevent warps in storage.

I came to the conclusion that structural complexities, such as seperate control surfaces, severely increase the mass. Since, much additional balsa is needed around the edges of the surfaces and on the surfaces themselves to prevent the the structure warping when shrinking the tissue.


Cheers

Tim

[OZPAF]

Beautiful flying model Ramses. Thanks for the link Tim.

John

[ramses]

@ Tim: Thanks!
The paint, full landinggear, cockpit glazing and a bit of noseweight added almost 20 grams. Wood selection is very important indeed, especially behind the CG! The Pawnee still flies great with the extra weight though! A very good and beautiful design by Richard!

@ John: Thanks!

I wanted to make a build thread, but i see that the source of my pictures (another forum) doesn`t allow linking anymore. I saw that all the pictures in my other build threads are gone too...

I will fix that, but it will take some time.

But i can show the two flight video`s i made of the Pawnee!

First pre-finishing test flights:

And the second series of test flights made yesterday:

I really love this quirky plane!!

Next to do is detail and weather the Pawnee.

Cheers, Ramses