1/4 scale Chris Williams Bergfalke

After the Ka6 and Ka8 kits from Flair and MKR, respectively, I started to look around for another vintage sailplane in  the same size category.

Since the market is somewhat limited in this, I finally settled for the Bergfalke, to be built from the well known Chris Williams plan.

Previously, I had already attempted plan builds on 2 occasions, for a 1/4 scale Reiher, and a 1/4 scale Sperber jr., but on both occasions, I gave up, since for one reason or another I just could not get the fuselages with their complex forms right.

I figured that the Bergfalke, with its  straight and fabric covered fuselage would less of a challenge, so I went ahead and ordered the plans, as well as Chris' building CD.

I drew up a set of ribs in Compufoil, using  the same airfoil as in the plans, and had them lasercut, as well as the fuselage formers.

The laser cutting files were prepared by Glenn at RC Plans ( rcplan@bellsouth.net ), and the laser cutting was done by Alex at AK Models ( http://ak-models.com )

The fuselage formers were cut from 1/8 and 1/4  liteply, the ribs from 1/8 liteply and balsa.

I started with the fuselage and tail feathers, to build the fuselage, I made this jig box, as suggested in the plans and building CD :

All the pictures are thumbnails, klick on them to enlarge

                          fuselage plans                                                        formers aligned in jig                                              another shot

                 installing the longerons

           Here the fuse is already removed from the jig, installing the lower longeron and wheel well                               rear area with cross-bracing          

                        tailboom                                                         fin & rudder installed                                      fuselage side planking installed

                 installing the upper fwd fuse planking           upper fwd fuse planking complete                           nose with self made tow release mechanism

     battery box and tow release servo installation                   rudder servo and bellcrank installation                                    rudder servo and receiver

     installing the lower fuselage planking, for this I drilled holes through the                                          lower side planking installed

     planking into the formers, the balsa bars are screwed onto the planking,

     thus pulling the planking tight against the formers, for a good bond.

     Once the glue has set, the screws and spreader bars are removed, and

     the holes are filled in.

Next was the installation of the landing gear wheel, 2 3/4 in diameter. I like to have the wheel removable, so I made the axle removable, by soldering a tab onto it,

a small screw secures the assembly to the fuse:

Horizontal stabilizer and elevator are of relatively simple built-up construction, only the curved trailing edge of the elevator presents some challenge.

I ended up laminating it from 3 3/32 balsa strips :

Fitting stab to the fuse, it is secured with 2 4mm nylon bolts :

                                                                                                                                                                     elevator drive mechanism

                                                               building the canopy

                                                                     It's starting to look like an airplane !

                         Weight at this point is 7lbs,7oz , with r/h spoiler and r/h wing servos still missing. But it lets me hope for a

                            reasonable AUW once finished, especially, since it looks like it will not need a whole lot of nose weight.