1/12 scale Yak-3

First step was to make a foam cutter able to produce trapezoidal wings; it leads to this strange thing:

The brass rod follow the guide for the Clark YH airfoil:

Both axis are adjustable so that thickness ratio can be different at wing root and tip:

Brass rod and guitar tuner:

Guitar tuner for the hot wire:

Here it is, Clark YH section wing:

The position of each axis must be adjusted to compensate for the “melting gap” making the wing thinner than expected according to basic geometry:

Testing foam resistance thanks to 1 liter of milk (the wing weights 8 g):

Looks like the wing can be deformed a lot before it brakes (a video shows movements of the wing tips in turns with amplitude of 2 cm):

This is how I was cutting the wings with this old cutter; it’s quit the same with the new one).

First, draw large wing shapes:

Cut it with a simple gravity cutter:

Put the shape under the wing cutter at the right position (a whole mess):

Cut extrados :

And intrados:

Playing with sketch up:

First prototype:

The only plans I have:

Smaller “precision” cutter:

For the ailerons:

The wing of the first prototype, with unguided aileron rods (vibrations in flight):

Making guides for cutting the fuselage:

The new wing cutter, easier of use:

The first prototype with motor in position:

Here, I was estimating that the aircraft should weights 500 g in flight condition:

The motor mounting is very trash… here it’s 441 g almost ready to fly!

This pics was taken after the first flight:

Four days later… cold weather (4°C) makes foam fragile!

The wing hurt the cold ground, etc.

No problems! Back again, with paintings, 3 days later…

I expected gray not pink!

And stupid me! I forgot I had a spinner to put on that motor! 1 cm too far from the aircraft’s nose…

The karman is in adhesive paper tape:

Bullshit!!

One week later, crash on a soccer cage (stupid me):

(This aircraft was repaired and could fly again)

Improved aileron control rod (no vibrations):

Wings of the second prototype:

Cutting the curved parts that were missing on the 1^st prototype:

The 2^nd prototype:

Only 2 axis:

No (or very few) sanding was needed at this point:

The first proto is behind…

The air intakes:

The 3^rd prototype (all parts cut in one day):

I had troubles with the 3^rd prototype! A crash after hand launch while I was trying a bigger prop… repaired and back again.

I’m now trying to install the Elogger and pitot tube on it:

Tool for cutting the trenches:

An old aircraft!