Box Fly 20- electric build

[Frank v B]

When I visited family in Holland in October 2023, I visited Ton van Munsteren.  He is a prolific designer and has many models published in British model magazines.  The best way to describe him is to call him Holland's Laddie Mikulasko*. 
Ton had just designed and built the Box Fly 20 and gave me a kit.  I had to cut the pieces to fit them into my suitcase.

The first step was to re-glue all the cut pieces.  I pinned one piece to the board and aligned the other half by using a steel edge to make it straight.

Will let them cure overnight before starting to assemble the plane.

Photos:
1) photo of my visit to Ton's house and shop.  The plane is in the foreground.
2) the kit as given to me
3) all the pieces were nicely laser cut.
4) the pieces I had cut apart were glued together.  Note the metal ruler used to make sure the pieces were straight.

Frank

* Laddie flies with the Burlington group and has many designs published in RCM magazine.  He designed the Force 1, Laker, Northstar and Easy 100 put out by Balsa USA.

[GuyOReilly]

Looks like a fun kit to build.
Make sure you do not end up with 2 right sides as the picture indicates.

[Frank v B]

Yes, Guy.

Before I started building it I flipped one fuse side over.
Sounds like you speak from experience.... but so do I! 

This is not a kit.  It is a 3D puzzle.  Formers are marked on the plans and the formers have laser numbering (F1- F11) but the numbers do not match the plans.  The laser cutting is so precise they only fit one way.

Frank

ps: I had to line them up that way to join them because the steel ruler had to be on the bottom of each piece.  Otherwise I could not have fit all the pieces on the board in one sitting..

[Frank v B]

starting to assemble the fuse.

F.

[Frank v B]

- basic fuse build finished.  The motor is 450 watts for a plane requiring 400 watts.  Just about right.
- tail feathers glued.  Just need to be sanded.
- wing building finished on one side.  Note the 1/4" square balsa near the trailing edge (at the point of the knife).  This is a symmetrical wing shape.  By placing this 1/4" square on an angle, I am building in "wash-out". (trailing edge at the tip higher than the leading edge for stall protection).
- the hatch is finished.  Magnetic hold-downs still have to be added.

Next: the other wing half.  It will be built onto this finished half.

Frank

[Frank v B]

- Building the second wing half- onto the finished first half.
- adding the shear webs
- cut out the canopy and build the headrest out of 8 pieces laminated.

Frank

[GuyOReilly]

Why is the headrest have white lines in the picture #5311?
Are these for alignment?

[Michael]

Why is the headrest have white lines in the picture #5311?
Are these for alignment?

The dark parts are where the wood was laser cut (burnt), and the white (balsa wood colour) is where the wood was still attached to the sheet.

[Frank v B]

Thank you Michael! 

Frank

Guy, I decided to arc the headrest area to match the cockpit cut-out.  It cradles the pilot's head during high speed turns.  A built-in HANS* device. 

* https://flowracers.com/blog/how-nascar-hans-device-works/

[Frank v B]

Back to this project since my last post April 10.

Background
- the design is a Boxfly 20 adaptation by a Dutch friend of mine who publishes his designs in RCM&E magazine and has his kits laser cut by RBC kits.
- I gave him a box of small IC motors (.049's, .020's) and he gave me this kit to try out.  We both won on this trade.
- most of the frame was built, motor installed before the hiatus when flying got in the way.

Next steps: installing servos, sanding, fibreglass the center section, install the landing gear, covering.

Frank

[Frank v B]

Fibreglassing the wing centre section:

Materials:
- 3/4 oz cloth
- 5,20, or regular epoxy.
- a 2" wide brush
- de-natured (isopropyl) alcohol- available at drug stores. Photo 15 shows the Rexall brand.

step 1- order- bottom first, overlapping the top by at least an inch.  Top second, overlapping the bottom by an inch- this way the leading and trailing edges have 2 layers.  These areas get the most abuse.  I did one side at a time, letting one cure before doing the second half.

step 2- lay the cloth over the area to be re-enforced.  The green tape in the photo covers the aileron plugs.  Photo 11

step 3-  mix the epoxy parts A&B completely.  Slowly mix in the alcohol until it is about an equal amount epoxy and alcohol.  The consistency should be that of water. Photo 15

step 4- apply the epoxy with the brush starting at the centre. Photo 13.  Stab the epoxy onto the glass cloth.  Brushing it slips the cloth all over the place.  Once the centre is soaked with epoxy you can radiate the epoxy by brushing outward.  Do not use much pressure at all.  Brush until everything is soaked. Photo 14

step 5- let cure overnight.  It may be sticky for a day or two.

Frank

[Frank v B]

... no stickiness the next day.  Nice and smooth.  No sanding required.

Frank

[Frank v B]

a quick and dirty way to line up a split elevator on a stabilizer.

It is always difficult to connect elevator halves when the centre has to go through the rudder. I hate the piano wire centre because you have to add a brass tube in the middle and find "neutral".

step 1- take the full elevator and mark the middle, add the hinges.  This way everything lines up.  Mark "up" on the elevator and the stab since this one is symmetrical.
step 2- add the hardwood dowel into the middle of the elevator.  I cut out a slot and flattened the back of the dowel re-inforcement.  The dowel was a bamboo skewer from the Dollar Store.
step 3- add fibreglass cloth and 5 minute epoxy and fold it over the bamboo skewer and flat out the back.  This U-shape strengthens the middle.  I put waxed paper over the fibreglass and put waxed paper over the fibreglass.  The green tape is to put pressure on glass so there were no air bubbles. Photo 61 shows the full elevator with green tape.  The photo also shows the semi-circular opening in the rudder.
step 4- cut the "V" shaped slot on the band saw for the rudder clearance.  I cut out most of it but left some balsa about the same thickness as the bamboo skewer.
step 5- add a fibreglass strip to the "V" and roll the edge of the glass around the skewer so it is 100% covered in cloth.  Photo 64.
Step 6- cover the cloth with waxed paper.  I used the cut out portion of the "V" to put even pressure on the fibreglass.  It is held in place by green tape while the epoxy cures.

Photo 66- finished. The bamboo skewer is visible.

A lot simpler than "U" shaped piano wire.  Total time about 30 minutes and that included 2 mixes of 5 minute epoxy.

Frank