CARF L39 - Build Guide

Place some tape and trace around the covers with a sharp x-acto knife. Roughen the surface of both the covers and wing and glue with thickened epoxy.

Ailerons: Prepare a 101mm pushrod. 

*NOTE: one end has a thinner ball link than the other.  The thinner connects to the aileron.

Ailerons: Use a 15mm servo arm.
(I cut, drilled and tapped a longer arm)

First, connect the pushrod to the servo arm (use locktite). Then insert a wire from the aileron to servo bay to guide the pushrod in place. 

There's no need to take out the aileron hinge. You might need to use some force and play with the wire until the pushrod is in place, but it's easily doable.

Carve a 5mm round opening for the ball link using a dremel. It can be done even when the pushrod is in place. The manual calls for 40mm up and 25mm down movement.

This picture, is taken from the manual. In my opinion, a better geometry would be if the servo head is closer to the aileron. However, it's not critical. (You would also, need a longer pushrod if you decide to go according to the original manual)

Fix the servo in place using a long extension driver from the root of the wing. I always put CA on the screws before I screw them in.

Use a drop of glue (5 minutes epoxy) to fix the hinge in place.

This is the flaps down position (Critical). 

Use a 15mm-20mm servo arm. I used 20mm which resulted  in a 146mm pushrod. a 15mm arm will result in a ~150mm pushrod.

You can expand the hole in the former to allow clearance for the pushrod and the nut. Make sure to use locktite for the clevis and nut.

Measure 82mm at the far end of the flap. Might be a bit more than what the manual suggest. but that's the way I like it. Anywhere over 60mm is acceptable.

Roughen the brass tubes and prepare it for gluing.

use some carbon to lock the tubes in place with some lightly thickened epoxy. I used a piece of tape to keep it clean. after an hour, I cut the carbon with a knife and remove the tap with the excess carbon.

I used a 20mm servo arm, and I had to shorted the rods by about 6mm.

I used actuators from actuonix: L12-30-210-6-RL12-R Micro Linear Servos for RC & Arduino 30mm 210:1 6 volts. Those can be operated directly from a receiver with voltage up to 2 cell lipo.

Sascha Euteneier used Electrons actuators 25 mm stroke

The actuonix comes with extra black plastic end screw attachement. I drilled into the center of it, inserted a plastic ball link, glued it with 5 -minute epoxy and screwed it in.

For the actuonix, the existing plywood holders were about 5 mm too far than what I needed. You can either solve it by using a longer ball links, glue them further away or, like me, remove the original plywood holder and make new ones with g10. 

Fix the air breaks in place with tape. set the actuator to about 95% of the movement and glue the mount in place. 

Position making sure a geometric lock is in place when the door is closed.

I prepared a slightly angled servo tray so the servo movement aligns with the pushrod movement.

Door closed servo position. I used a 20mm servo arm.

Door open servo position

You'll need to sand the bac part of the former to allow clearance for the wheel. When closing, the gear will touch the carbon part of the wheel bay. That's normal.

No modification is needed for the gear mount. With the gear retracted, align the gear, drill a pilot hole with a 2mm drill bit and use the supplied wood screws to fix it in place.

Use a large straight edge to align the wheels. 

Roughen the surface where you'll attach the mounts for the strut doors

Prepare the mounts

Test fit and fix with tape for easy gluing.

Glue the doors, trim the outer part (close to the pivot point) later.

I fixed the break cable in place with clear tape and some black heat shrink and CA in places.

To fit the nose gear you'll need to expand the mount.

34mm width

37mm height

I used goop to glue the cockpit sides.  you can also use velcro, but from my experience, there's no reason to take those out at any point.

The position should be about 12mm from the opening.

Use clamps to dry fit and then hold when gluing.