www.F3A.fr

balsa tube is very beautiful !

The rudder servo tray was added next. The receiver and digiswitch will also be installed on this tray. As usual, i started with a cardboard template to make sure it will fit perfectly, then cut the final part from nomex honeycomb.

The canopy latches seem way to large and heavy, so after some trimming and sanding here and there i managed to save about 7g. The metal pins are also much longer than needed, so i will save more weight later when i will figure out the exact length.

To attach the locking pins to the canopy, first i created a cross-member using a few pieces of plywood and balsa. I used a regular screw to create the threads in the plywood parts. The plywood ends with the pins attached were placed on the fuselage and a piece of balsa was used to join them. This way i was sure the distance between the pins is the same as the distance between the holes in the fuselage.

A few pieces of balsa were used to create some sort of spring that would keep the cross-member pressed against the canopy flange. This way i was able to move the canopy around a little bit to fit the fuselage properly while the cross-member was held in place by the locking mechanism. When i was happy with the position of the canopy, i added some tape to keep it still while the epoxy was curing.

I initially planned to go with 2 carbon pins at the back of the canopy and the locking mechanism at the front. As you can see in some of the images below, i attached the 2 carbon pins but found out this combination is not going to work. With the 2 carbon pins inserted in their slots at the back, it's not possible to make the 2 metal pins at the front to engage the locking mechanism. I had to cut the 2 carbon pins and use a canopy latch instead.

It's been a while since the last update; in the meantime there has been a "slight" change of plans but work never stopped. My friend at the composite workshop is busy molding a jet, so i didn't want to bother him with another set of composite wings. Anyway, instead of sitting around doing nothing over the winter i decided to start working on a new set of built-up wings and stabs for Audax. I also designed a built-up rudder because the composite one was a bit heavy.

The 3D design took about 3 weeks to complete, working every day for a few hours in the evening and maybe a bit more during weekends. The basic concept of the structure was borrowed from Radiance, which proved to be very strong, but decided to add a second spar around the carbon tube to help distributing the loads on a larger surface of the skin panels. I was a bit worried about bending the balsa around the compound curves at the tip of the wings and stabs, so the ribs were positioned closer together in this area. I added some secondary spars to the rudder structure, also to help the balsa sheets bend around the compound curves.

The balsa sheets available here are not very light, so i'm pretty sure i won't be setting any records with my final weights. For example, the lightest 2.5mm (~3/32) balsa sheets i can find here weigh around 25g, while other projects i've seen use 16g sheets. Since my balsa sheets are heavier, they are also probably denser and stronger, so i will use 2mm instead of 2.5mm balsa for sheeting the wings. It's still heavier, but other than that there's not much i can do.

I attached a few images of the 3D structure, building images will follow.



Large size images here:

http://s5.postimg.org/vctky7bjp/structure1.jpg
http://s5.postimg.org/k897qo379/structure4.jpg
http://s5.postimg.org/nqgm9beph/structure3.jpg
http://s5.postimg.org/572bvnv3r/structure2.jpg

Start of rudder assembly:

The plan is to use Robart pin hinges and make the rudder removable, so the rudder leading edge is rounded and will be partially hidden inside the fuselage. I also built a second jig to help me attach the balsa sheeting and checked its alignment with the rudder structure.

Hello Alex

Awesome job.
Have you planned to sell kits of wings and stab ?

Hello Claude,

Thanks for the kind words.
Yes, if there's interest for it, i can provide short kits for the wings and stabs.

Next step was detaching the rudder structure from the jig, cleaning and sanding the ribs where they were joined with the jig and add the balsa sheeting (only on the right side for now):

I added the balsa blocks to support the pin hinges for their entire length and, using the lasercut holes in the front spar as a guide, i drilled the holes in the balsa blocks. The block at the bottom will also support the control horns, so it is a bit larger.

I used only 1.5mm balsa for the skins, but now that it's sheeted on both sides, the rudder seems very strong. When pressing the rudder between the 2 jigs i used a lot of weight, so i had to protect the balsa skins with a piece of cardboard. The balsa skins were a little oversized, so in the end i sanded them flush with the edges of the rudder.

I wrapped a wet sheet of 1.5mm balsa around the wing tube, let it dry overnight and used it for sheeting the rounded leading edge. The balsa block at the bottom of the rudder has a 1.5mm plywood core with 2 tabs that will fit into the bottom rib slots to ensure the proper positioning and alignment. The plywood core also has slots for the tailwheel steering pin and the hinge axle. The balsa block was sanded to shape and in the end i added some light filler around the joints. The rudder is now done and i'll move on to the stabs.

claudecuinet a écrit :Hello Alex

Awesome job.
Have you planned to sell kits of wings and stab ?

Hey, Hey! Claude...

What do you think? An evolution of the Hamony with elliptical wings and stabilizers?... Why not!

Other than that, great wood structure, on the Audax; I like that.

Blue skies.

Bonjour Jean Claude

C'est une excellente idée.
J'ai déjà fait une aile BA arrondi (voir photo) qui a été montée sur l'Arixtra de Jacques et qui donnait entière satisfaction.
Mais celle d'Alex est encore plus belle.
Ce type d'aile pourrait se monter sur toute sorte de fuseau.

Superbe travail Claude !

Can you post more details about your wing construction? What was the final weight before covering?