Delro Foka 4 @ 1:3 scale build thread

[Steve P]

This will be a limited set of posts to help catalog the pieces/parts. While at Spielwarenmesse this past January lamenting the sorry state of the RC hall, I decided I needed to support the local economy. Always loving the Foka and having multiple dead end email exchanges with their alleged US dealer Vogelsang Aeroscale, I reached out directly. A couple quick conversations and a wire transfer and the deal was done.

I elected to have Detlef at Delro and their crew do a fair amount of the work on what is very basically a kit. Finish the wings, install the carbon roots, insert the servo boxes, paint white tops and red bottoms, finish the fuselage and paint, install the rudder post and hinges, etc. Still plenty left for me when it arrives. While its it’s been a slow process, the fuselage is done awaiting final white and then red stripes, wings are in paint, etc. Canopy will be scale and slide forward instead of open sideways. Shipping should be in the next couple weeks. Fingers crossed.

There are several 4 meter Foka offerings out there, but precious few that are larger. The Delro’s 1:3 scale and 5 meter span works well for me. Bruckmann is also working on a gorgeous 6+ meter Foka that's around 40% so there is the future potential of choices.

I sold my trusty 4.4 meter Valenta Fox knowing this project was coming. I plan to also do an air show type decorations on the wings and fuselage, in this case a Zywiec beer scheme in honor of the Foka’s Polish heritage. Hence the white/red base colors. I'll be keeping Callie busy.

Initial three photos of the fuse work from Detlef”s shop as they get it finished and ready to ship...

[Asher Carmichael]

Nice! It’s always fun to anticipate getting a new model. Enjoy

[ARUP]

The Foka is a good looking sailplane! You've got a nice model!!!

[DennisB]

Should fly nice, they made my Dimona although I got the raw kit.

[Steve P]

Finally getting the Foka on the bench. I won’t be making many posts except to point out key aspects of the kit. Starting on the wings. Each wing is 96” in length and the root chord is 17.25”.

The "oops" on their end was forgetting the wing bottoms were supposed to be red!! And, not shipping the extra canopy I ordered. Still sorting out those issues. The red striping and black keel was done on the fuselage.

Given the level of work I asked them to provide, wire channels were pre-cut into the cores, but upon removing the servo covers I discovered (because I forgot that I ordered them) mounting frames are integral to the wing. JR NX8931 servos are going on the ailerons while the airbrake frame also accommodates a full-size servo in the frame with the arm facing downward. Right now I’m thinking a JR NX588 should suffice. Brakes are 16” Florian Schambeck.

Here's a shot showing how the aileron servo slides down into the wing mount




And ample space to drive the airbrake with a standard sized servo. Nice!

[stevekremer]

Very nice Steve.

Steve K

[Steve P]

Fuselage is ready for some Callie magic. Only interesting part of the install will be the rudder as it sits on top of the servo driving it. The Valenta Fox has a similar arrangement. I’ll post that when the time comes.

I painted the fuselage interior for looks and so that light does not shine through in flight. Sequence is gray primer, fine grain gray granite paint, then multiple coats of dead flat clear. You can see the finished result in later photos below showing the batteries and cockpit install.

[Steve P]

FYI FWIW, the December 2005 edition of RC Soaring Digest has an excellent walk-around and cockpit detail review of the Foka 4.

http://www.rcsoaring.com/rcsd/RCSD-2005-12.pdf

[Steve P]

A small bit of work was accomplished today including installing the main wheel. First up was getting the aileron horns installed. After debating if I wanted to bolt though the horns and input from Scot and Len, I went with a pair of thick G10 horns and base plate that will carry a ball link connector between. Hysol 120 was the epoxy of choice.

The ailerons and elevator will be driven by JR NX8931 servos.



The ailerons are knuckle-hinged, so I placed the pivot point over the hinge line that is actually inside the gap.


Next I turned to the fuselage installing the tow release and dual battery packs. I first painted the interior of the fuselage with gray primer, fine grain granite paint and then a coat of dead flat clear.

The packs are PowerBox 2800s and install with nifty frames. All of the charging circuitry is inside the packs. They simply plug into a 12V adapter. https://www.powerbox-systems.com/pro...tery-2800.html

The packs will feed a PowerBox Gemini II with double regulated output voltages. https://www.powerbox-systems.com/pro...-gemini-2.html The plane only carries 7 HV servos, so I figure the Gemini is a decent choice. I may change my mind and go with a bit more "mo."

The odd steel thing protruding from the right of the photo below is a drawer slide. It is how the canopy slides forward keeping with the full-scale canopy's function.

[Steve P]

Next up, attention to the tail. There were moments fiddling with the rudder that made me question if there is a God, but in the end the function was heavenly.

The first step is easy, making up the rudder drive. The rudder functions by sitting on top of a servo. The base of the rudder contains a blade molded into the structure. A series of G-10 discs are joined with epoxy, screwed together (belt and suspenders), the groove for the blade is then opened, and finally a servo arm (circular) is attached.

Here are the pieces for the drive. There are no instructions, just a simple photo of what the finished install should look like.



Making up the block




Adding the servo arm with epoxy and screws



A JR 8411HV servo was chosen for the rudder. I like this servo as the gear train has plenty of give when not powered. If the rudder is bumped in transport, etc, the rudder will easily swing, not resist and break something.




Laying out everything on the bench to take measurements. Getting the servo mount down inside the fuselage at the proper depth and orientation is a soul-sucking experience.

[Steve P]

It took a few failed attempts and head scratching until I realized this would be an easier task done sideways. The servo was screwed into the mount, I added some blocking to the side of the servo so that everything would sit flat and not tend to fall over, then had to slip the servo and frame into the fuselage, then attached the servo arm as everything assembled would not clear the space available to access the fuselage interior. I then fiddled for quite some time to make sure I had the geometry right.

"Measure twice, glue once" is more like measure twenty and keep measuring and fiddling. Finally, it was time to commit to epoxy and prayer. I used the carbon rod that serves as the hinge pin inserted back into the tabs to make certain the center of the servo was dead on.

Making gravity work "for" me...



The finished rudder operates smooth as silk...



Next up is the elevator, which will be a piece of cake as the access to the servo is huge and the mount is already in place.

[ARUP]

Nice rig for the rudder!

[DennisB]

Looking good Steve, I’ll ask for everyone, we want to see more of the sliding canopy mechanism, just calling it a “drawer slide” raises more questions then answers. Did Detleff use 2 part Epoxy style paint for the wings?

[Steve P]

Patience grasshopper. More will be revealed to you. As for the paint, yes. Very hard, matches the fuselage perfectly. The fuselage paint job is excellent. The wings have some flaws and the bottoms are meh, mostly because the final coat in red was forgotten. No matter, it going to be splashed with graphics and stripes. This will become a flying beer billboard.

[Steve P]

For Dennis...

No time for the workshop today, but I grabbed a couple photos to show the canopy slide. It actually is a drawer slide. The canopy bolts to the section that would typically be attached to the drawer side while the portion that would typically be mounted to the cabinet frame is mounted into the fuselage. While not "exactly" how the scale one operates sliding forward, the illusion works nicely.

Canopy open...



Canopy closed....



Canopy bottom, 2 bolts into t-nuts release the canopy from the slide....



The real deal...

[Steve P]

Fun with vinyl. Callie is a godsend...

Recall this is a straight leading edge wing with the taper on the trailing edge. All the graphics align to the leading edge since the main graphic will travel across both wings and the top of the fuselage.

Working around the airbrakes is always fun



Decided on layering the logo instead of cutouts in the red and blue



Two bottles of beer on the wing... two bottles of beer... you take one down...



What was once plain white, ain’t

[Steve P]

Fokafide...