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1/4 Scale SZD9 Bocian**

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Peter Balcombe
Posts: 1348
Joined: 18 Mar 2015, 10:13
Location: Clevedon, North Somerset, U.K.

1/4 Scale SZD9 Bocian**

Post by Peter Balcombe »

This build was posted on the old forum, but unfortunately lost in the ether by the time Barry started saving as many as he could.
Luckily, I still had most of the build photos on my PC and scribbled a few words of build text.
This is much shorter than in the original build thread but hopefully the photos will tell most of the story anyway.
The build was the Cliff Evans short kit proving prototype of the Jilles Smits design.
This kit went together very well and I know that Cliff really likes the way the model flies.
The attached files comprise a number of zipped folders containing photos from several build areas as identified by the file names.
Note that the zipped Fuselage photo folder is too large to attach in one go, so will split this and add in a moment after I make sure this lot posts ok.

Build Summary:
Most of the supplied kit parts are ply and everything had been cut very well. I started off with the wing main spar webs, joining the multiple supplied pieces and bonding a pre-spliced lower spar to the rear of webbing. Note that it is advisable to fit a doubler across each webbing assembly joint, although not shown on the plan. This also applies to the dummy leading edge in due course.
With the lower spar/webbing assembly made up it is then easy to do a dry assembly of a lot of the wing components as the laser cut parts slot together very nicely.
Note that as the ribs do not fit at 90 degrees to the main spars/webbing, you with probably need to ease the slots slightly to allow the ribs to move around to the correct angle. I tend to use aliphatic glues for most wood joints to provide a sandable joint where needed. However, I use epoxy for stressed areas such as the joiner box etc.

I fitted 15mm brass joiner box instead of the 14mm type shown on the plan as this was what Gliders now stock owing to fit issues with the 14mm stel blade/brass box combination. I padded out the joiner box area with hardwood/ply fore & aft of the box plus between the box and the top & bottom spars to ensure that the box was well and truly bonded to the main spars. Use epoxy in this area.

The two aileron, plus airbrake servos were installed on plates as shown in the photos. The top & bottom skins were applied in tip & root panels as my 0.4mm ply supplies come in 4ft x 4ft sheets. A balsa doubler was fitted to the top/bottom of the joint position rib to provide a glueing land for each skin section.

Rolled paper tubes were made to house the servo wires and allow simpler removal/replacement in future if required.

The airbake arms were made from either 1/16" brass sheet or double sided PCB material (I think the latter) in the manner shown on the plan. This worked very well as long as you make sure that the outer pivots are at equal radii from the centre and the same on all arms.

I started my fuselage build on a 'Bridson' jig which allowed me to position all the formers at the correct height and separation. Note that some of the forward formers and wing root area parts are interlocking so that helps jig it all up.
Just keep checking that everything is straight by eyeing along the centreline.
Note that the wing joiner brass boxes and incidence pegs need to be put in as the former assemblies are made up.

I made up the fin structure separately (working up from the finpost lying on the building board) and then fitted this to the fuselage structure.
As you can see from the build photos, I built up the tailplane before I added the fuselage skinnning in order that I could check squareness of the tailplane seat with respect to wing joiners before finally glueing this into place.

I added balsa doublers around the outside of each former to provide an increased glueing land area for the skins. The skins were mostly installed on a former bay by bay basis using evostick as a contact adhesive. (Apply glue to both surfaces, allow to dry, then carefully place the skins in position and press down).

Local balsa backing pieces need to be added in certain places, such as the closed loop tube fixing areas and rudder hinge glueing blocks.

I feathered one end of each skin section on the inside and the opposite end on the outside of the piece rather than butt jointing, to provide a larger skin to skin joint area. The lower part of the fin was particularly difficult to skin due to the 3D nature of the curvature in that area.

The canopy was made as a fixed forward section, hinged centre section and sliding rear section, using the older multi sectioned glazing approach. More modern Bocians have less glazing pieces, but need 3D curvature mounded sections.
The rear sliding section uses brass Mick Reeves sliding canopy rails bonded under the fuselage canopy frame. A slot at the rear of each rail allows the canopy to removed if slid right back. A simple clip made from bent brass strip ensures a solid retainer when the canopy is slid right forward.

The tailplane was built in a similar manner to the wings, the main components slotting nicely together. Note that I fitted the elevator servo before adding the forward centre section parts in order to avoid locking out the servo fitting opportunity without surgery.

The tailplane cover is a bit fiddley to make & I used 'BigBoy' filler to mould the interface shapes to ensure good fits.

Once the fuselage build was complete, I glassed the inside of the cockpit area with heavyweight glass cloth/epoxy to provide strength and handling crush resistance in this area. The complete external fuselage/fin was glassed in lightweight cloth to provide the paint surface.

The wing, tailplane, elevator & rudder were all covered in natural Solartex & then painted using a 2" roller. I used Blackfriars QD90 enamel white metal paint plus Hammerite red for the ailerons and trim.

Cliff Evans supplied the decals, which he had made up in the U.S.

The model was balanced at the CoG position shown in the plan information and I think this has been left unchanged after the maiden flight.
Wing Build photos
(13.57 MiB) Downloaded 340 times
Tailplane build photos
(5.82 MiB) Downloaded 212 times
Overall structure photos
(2.85 MiB) Downloaded 253 times
Canopy build photos
(3 MiB) Downloaded 221 times
Finished photos
(4.81 MiB) Downloaded 259 times
Last edited by Peter Balcombe on 10 Dec 2015, 21:40, edited 1 time in total.
User avatar
Peter Balcombe
Posts: 1348
Joined: 18 Mar 2015, 10:13
Location: Clevedon, North Somerset, U.K.

Re: 1/4 Scale SZD9 Bocian

Post by Peter Balcombe »

Finally, the two zipped Fuselage build photo sets, split into the initial steps of jigging & skinning, then the rest.
Fuselage Jigging and Skinning
(10.82 MiB) Downloaded 306 times
Fuselage completion
(8.83 MiB) Downloaded 224 times
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Joined: 22 Mar 2015, 10:27
Location: Australia

Re: 1/4 Scale SZD9 Bocian

Post by Jilles »

Good to have this info on record
Just a remark on compressing files with photo's
It is not worth the trouble to compress photo's ,you will notice that there is hardly any difference between the Compressed and uncompressed version
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Joined: 01 May 2022, 10:45
Location: espana

Re: 1/4 Scale SZD9 Bocian**

Post by juankax »

Many appreciated folks, I'd never gone over the Multiplex wing locks. I'll likely do the lady trip with simply tape at that point, if all goes well, take a gander at retrofitting the wing locks.

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