JT-5B Spesifications: JT-5B is a development of the JT-5 autogyro I

Dimensions:
designed and built 1969-1973. The main differences are Roll Control Stops +8°
Rotor Diameter 7.0 m (23 ft) a 100 mm bigger propeller diameter for better propeller 8°
Length
Height
3.55 m (11 ft 5.3 in)
2.05 m (6 ft 7 in)
efficiency and a lighter rotor head. 8°

Areas:
Horizontal Stabiliser 0.82 sqm (8.82 sqft)
Vertical Stabilisers 0.73 sqm total (7.85 sqft)
Rudder 0.31 sqm (3.3 sqft)
Weights:
Emty Weight 165 kg (367 lb) 10° 10°
Gross Weight 280 kg (622 lb)
Power Plant:
Engine:1700-2000 ccm VW, 70-80 hp recommended Rotor control Stops +10°
Propeller Diameter 1300 mm (51.2 in)
Pitch, adjust to give 2800....3200 rpm
Static Thrust Requirement, minimum 1300 N (290 lb)
Rotor : Scale: 1:10
Rotor rpm range 380-400 rpm
Prerotator 5 hp to give 250-300 rpm for rotor
Rotor Brake included Blade Flapping Stops +8°

8°

8°
74

This dimension greatly depends on

the weight of the cockpit , canopy,
instruments and other equipment
Construction: forward of CG. Therefore, check the
CG position before final welding of
the rotor mast end fittings.
Rotor Blades:
Fiberglass sandwich construction
Polyurethane or PVC foam in trailing edge
Full span lead weights in leading edge
Fuselage:
Fiberglass/epoxy/honeycomb sandwich construction (vacuumbag method)
Load carrying structure of 4130 welded steel tubing.
Tail Surfaces:
Fiberglass/honeycomb and plastic foam sandwich construction. Carbon fiber
used in vertical and horizontal tail spars.
Propeller:
All fiberglass/epoxy
Landing Gear:
Scale: 1:10
Fiberglass/epoxy springs

Rudder Pedal Adjustm.

Throttle
Prerotator Lever
Wheel Brake
Control Lock
Ventilation
Canopy Latch

Scale: 1:5

Signature Date Version

Tervamäki Design Jan 29,1998 02
Jukka Tervamäki
Harmaapaadentie 12A
00930 Helsinki, Finland

Scale Projection

AUTOGYRO JT-5B 1:5 No:01

General View 1:10
 30
52 RUBBER MOUNTS AND BUSHINGS IN FULL SCALE
20
68

18

Ø10
30 20
3
R2 6
80° 35
83° 30
R5 R5
28

Ø60
M10
Ø14
This dimension greatly depends on the
weight of the cockpit , canopy,

Ø40
Ø60
instruments and other equipment

Ø40.5
forward of CG. Therefore, check the

Ø13

Ø60
CG position before final welding of the 3
rotor mast end fittings.

80x40x1.5 or 90x45x1 Engine mount studs to replace the

4130 steel tubing two original studs in the clutch
73° Bushing, 4130 steel, 3 ea flange of the cranckcase.
Rubber Mounts, 2 ea
Shore Hardness 75
35
36
R1 R5
80x40x1.5 or 90x45x1 2
4130 steel tubing 2
R1 1.5

Ø40.5
Ø13

Ø60
1584
55

362

56

48
Engine C/L

252
85
6
296

225
Rubber Mounts, 2 ea
Shore Hardness 75

120
215 Engine mount plates
4130 steel, 2 ea
85° 209

195
0
R3
30
20
0

560

480
Landing gear leg thickness
determined by aircraft gross 56°
weight. Add or remove extra
thickness as necessary after
test loading the aircraft.
85°
80x40x1.5 or 90x45x1
4130 steel tubing

1150
650
310

1200
511

MAIN LANDING GEAR LEG

WHEEL FITTING.
Unidirectional rowing. Three top
layers bidirectional fabric

285 70°
60°

200
13
0

200

Ø40
40 x 1
75 4139 Steel Tubing
10°
45

40 x 1
4130 steel tubing 80°
5°
This landing gear angle can
be 0....5° depending on the CG 18 x 1
position when fully loaded 4230 Steel Tubing
Ø40
55

(pilot & fuel)

Signature Date Version

Tervamäki Engineering Feb.20,98 02

Jukka Tervamäki Tervamäki
Harmaapaadentie 12A Engineering
00930 Helsinki, Finland

Scale Projection Drawing

Ø35 AUTOGYRO JT-5B 1:1 No:02
Steel Tube Structure 1:5
NOTE: The original JT-5 rotor head had a mechanical Rotor Blades are of glass reinforced plastics (epoxy). Rotor diameter 7.0 m, Chord 180 mm.
tachometer drive (VDO, Germany). Since advanced optical and Rotor weight including the hub 17 kg, normal rpm 380, max rpm 550. Preset coning angle
magnetic transmitters can be obtained today with electronic Needle bearing INA NA4900.2RS Bearing type 3205 2RS. 3°..3.5°. Blade profile NACA 8-H-12
tachometers, no details have been shown. http://www.ina.de/ http://www.skf.com
http://www.ina.de/ Aerodymamic Pitch 4° Blade root Polyurethane or PVC foam core
Axis of zero lift Geometric Pitch 1.5°
9 10 11 18 25 24 19 24 25 45° degree fabric laminate
Blade root bolt axis
4.0°

9
Trailing edge level 1.5°

50 Unidirectional glass fiber

180

Chordvise balance weight Ø8 mm lead rod

INA PAF 10120 P10

http://www.ina.de/
Flapping stop
s +8°(9°max)
16 8 7 17 1
23 12 13
INA HK4020/IR35x40x30
6 http://www.ina.de/
Use press fit for the inner 3
20 race on the gear base.
26 27

Turned and grinded to

25 Ø35.00+0.03
+0.02 6

25
22 1 2 Important! Drill a
5 mm hole here to
drain out possible 14
rain water! 13
3 4 Bearing type 6201 2RS.
21 http://www.skf.com
http://www.ina.de/
12
Seger J 32 DIN 472
28 Rotor Prerotator Bendix Drive, Lucas 10
P/n 25012 consisting of the following
parts: Lucas p/n 292241, 291970, 2
54296889, 54251921, 260404,
250837, 250848 and 250849. 25
http://www.lucasvarity.com/
The new idea shown on the left is
based on a Bosch Bendix Drive used in
small 2-cycle engines. Similar units are

107
videly used in outboard motors.
NOTE: This idea has not been tested
and, therefore, no parts or part
numbers are shown.

Universal Shaft: Lmin=570 mm, Lmax=770 mm 15

Willi Elbe Gelenkwellen GmbH & Co. KG
D-71732 Tamm, Postfach: D-Tamm, Germany
Telefax: (07141) 605095
Approx. 102 mm
Check carefully this dimension
for smooth running

161

INA GIKFR 10PW or similar

9 10mm rod end.
http://www.ina.de/

NOTE: All bolts, nuts, washers and similar hardware, which

have not been specified in these drawings are of standard
metric quality (DIN 912) in the 8.8 strenght class.

NAS, MS and other aircraft quality hardware can be used if

corresponding changes in dimensions are made, eg:
16 mm=5/8 in, 10 mm=3/8 in, 8 mm=5/16 in, 6 mm=1/4 in,
5 mm=3/16 in, 4 mm=5/32 in, etc.

Signature Date Version

Tervamäki Engineering Jan 29,1998 02
Jukka Tervamäki Tervamäki
Harmaapaadentie 12A Engineering

00930 Helsinki, Finland

Scale Projection Drawing

AUTOGYRO JT-5B 1:1

Rotor Head Assembly No:03
 Check the proper play
Ø185
with the Rotor Shaft
bolt, max 0.03 mm 20 69.0+0.0
-0.1
Ø12 Drill these holes in assembly 34
Ø16.0 Ø106
12x45 Ø4 45° 114°

15
13
Ø52 J7 Ø8

Ø22

Ø15
16
2

45

Ø27
1

Ø21

Ø24

Ø12.0
30

30

6
17

17
R2

Ø4

20
5
R0.8
.
R2
R0
25
14

25°
7

R5

36
.0
0.5x45° R2

91
7

2
Ø25 M8 Ø46

16
Ø42 R0.5

76
13 22 approx.30 25.00

73

57

49
2
Ø100 A-A
100
55.5
1 Ø168
Ø180
10

3.6
6
10

Ø50
A
34

.8
R0
10

0
10 2 4.
Ø Ø52.0 J7
10 R2
13 11 63.0

7
.5 M4

14
7
Ø8.2

Ø42.5 4
Ø1

84
Ø
Ø50

68
Ø4
1.2

14
10

69.0+0.0
Ø15

-0.1
48
27
Ø4,0

12
25 A 16.0

63

48
Ø30
Ø27

41
5,0°
Ø4

9.0

16,0
4 x 45
13
Ø8,0

107
80 48 +0,1
70,0-0,0
Ø22 H7

48.0
80
40°
63.0
Ø47 H7
63

SAE 4140. Hardened 20

50

Ø10
min HB 240-280
Ø4,1
72Z, DP 10 or m 2.5
30

0.4
22.6
14.5

7,5

18
10

31

Ø10
Ø50
3

3
58.0 Ø42 Ø28
M4
Ø50
12

-0.0
11.2+0.1
2

9
1.3
15

13
7,5

Ø0,5
R2

95
24.0
Ø32H7
Ø10
33.7+0.2 Ø10 94
36.1+0.0

24
-0.1

-0.0
Ø10 50
60

2 4 Seger J 32 DIN 472 42,0

2,3

Ø35
12
Ø3

Ø10
Ø

Ø14

Ø35
10

Ø14

20
Ø8
15.0

130
Ø5
0
14

Rotor Brake 3,0°

Ø
13

12.0 Cable Catch

M

14
12

10
15

27 310
58.0
22

15
8

Ø6
Ø10 K 7
Ø8
Trim Control Spring
R0.5 28 P/N PART EA Material Specs Notes
R2 Remove by machining 1 Torque Bar 1 SAE 4130
Ø

2 Control Arms & Bendix Housing 1 SAE 4130

20
Ø

3 Control Gimbal 1 2024-T3

22

Ø19,0 The rotor brake is made of 4 Bearing Housing 1 2024-T3

a light motorcycle brake. 5 Control Gimbal 1 SAE 4130
Ø30

Lmin=270 mm, Fmin=20N, Lmax=400 mm, Fmax=200N

3

This drawing can be used as 6 Driven Gear 1 SAE 4130 Hardened

R0.4 a quideline to modify similar 7 Bushing 1 2024-T3
4,76 H 10 16 units of various manufacturers. 8 Bushing 1 2024-T3
Ø15,8 However, check the thickness 9 Rotor Hub Plates 2 SAE 4130
0,2 x 45

for proper fit!

12
38

10 Flapping Stops 2 2024-T3

6-8 mm 11 Rotor Hub Block 1 2024-T3
Ø33 80
12 Bendix Drive Spindle 1 SAE 4130
45° 13 Bearing Retainer 1 SAE 4130
Ø13
14 Bushing 1 SAE 4130
5:1 15 Bushing 2 SAE 4130
10

R0.2
8
8

16 Rotor Brake 1 Union Light motorcycle type

,2
18

R0 13 17 Gimbal Bearing 2 INA Permaglide PAF 10120 P10

10

,8 22x1 Ø 10 18 Teetering Bolt Bearing 2 INA NA4900.2RS

4230 Steel Tubing
19 Rotor Main Bearing 1 3205 2RS
134,6

A-A
30

Ø16.0 20 Bendix Drive Bearing 1 INA HK4020 IR35*40*30

21 Bendix Drive Bearing 1 6201 2RS
Check the proper play
10

Ø25k6 22 Rotor Shaft 16*90 mm Bolt 1 DIN 912 Class 8.8+Nut and Washer
with the Rotor Shaft

Ø40
Ø16 H8 A A
bolt, max 0.03 mm 23 4 mm Bolt 1 DIN 912 Strenght Class 8.8
24 8 mm Bolt 1 DIN 912 Strenght Class 8.8
Ø25k6 25 10 mm Bolt 1 DIN 912 Strenght Class 8.8
22,3

Ø12
Ø16.0 26 Locking Pin 2 Ø 4 mm Hardened Steel
Ø4H11 27 Washer 2 Ø 35/14 mm 0.5 mm, Brass
2,3

8 R1,2 Ø10,3
0,
10.5

R
7 Signature Date Version
9,0

Tervamäki Engineering
10

Ø12h6
30.0

Jan 29,1998 02
B-B Jukka Tervamäki
19.5

Tervamäki
9
12

Harmaapaadentie 12A Engineering

Ø

18

15 00930 Helsinki, Finland

Ø1 10

B B
Ø

Ø33
4

Scale Projection
1

AUTOGYRO JT-5B 1:1 No:04

Rotor Head Parts
 41
30 Open lenght 250 mm
19 To obtain a gearbox which is close to
16 the dimensions shown here, contact Ø26

Ø20
Ø10

Ø14

M10
DZ Trasmissioni, Italy:
10 Ø6
http://www.dztrasmissioni.com
9.6°

R8
Ø10 h7
12
3

Ø8
6
Bearings Ø20 R2
0
6000 2RS

6 .1
35
3 4 BEARINGS
6301-2RS 38°

Ø26 H7
Ø70
Ø32

Ø20
Ø14
Ø10
15 Ø6
8 35 35 100
STEEL 4130
45°

10
2024 T3 AL 2024T3

3
AL 2024 T3

5 65
40° 216
Ø6

150
Ø12 H7

Ø130
Ø26
4

2
30 Ø12

3
Gears: Modul 2 8

20
No of teeth 16 0 Ø5

70
Outside Dia. 34.82 mm R10 R2

55°
10

30
10
35

80
95
R9 0
10 R2
38° 55 Ø8
16 35
Ø8 3 8

Ø6

Ø40
AL 2024T3 Ø6
1.5
FRICTION BLOCKS OF
PLYWOOD OR PLASTICS

R9
3.1
40

Ø8 H7
-0.00
41+0.03
20

Ø148
Ø70

Ø70
Ø118
Ø60

Ø29
Ø60
Ø70

35
9 17
CRANK SHAFT 28
45°
VW 1700 Ø5

30
20°

R
25
4 M6
15.8

1.5

Ø10
9.0

10
SAE 4130

10
9

16
Ø4

18

92 26
30

30 0
Ø12h7 R1
15

Ø10

Ø16 4130 STEEL

78

30
18°
30 THROTTLE
Ø
43
30
Ø4

14x2 mm
22 30
13

13
10

87

Ø12 h7
50

15x1 mm 33
23

Ø3

22
10x1 mm M6 13
PREROTATOR OPERATION:
18

Pull wheel brakes ON with the right hand. Advance the Throttle to 1000-1500
Ø3

22
10

engine rpm. Pull prerotation lever with left hand fingers. This causes the brake
wedge to release the driven wheel and tightens the V-belt. The power train to
12

Ø10 rotor head starts to spin and the bendix unit engages. The rotor starts to spin
Ø6

25 x 6 x 1 mm slowly. Advance the throttle until 250...300 rotor rpm has been reached, then
20° release the prerotation lever and wheel brakes simultaneously. The v-belt
6x1 mm becomes slack and brake wedge plunges into the driven wheel causing it to
50

Ø9.5 stop immediately which in turn releases the bendix drive gear. The machine
3

115 gains speed and the rotor accelerates to full flight rpm (about 400 rpm) Signature Date Version

30
51 Tervamäki Engineering Feb.10,99 02
38.0 0.5R
15

34 Jukka Tervamäki
18 12.0 Harmaapaadentie 12A Tervamäki
0.5R 0.5R Engineering
8.2 00930 Helsinki, Finland
3
Ø12 h7

4130 STEEL
M12
M12

Ø15

Scale Projection
TO PREROTATOR V-BELT CLUTCH
Ø12 h7

Ø10
AUTOGYRO JT-5B
Ø4 Ø20 6000 2RS
Prerotator Details 1:1 No:05
 Ø10

10

1.5
63

52
Ø5

2.5
30 2
15

Ø10 h6

ca. 200
Ø24

Ø22

Ø24

80
M10

Ø26
R0.5 Brake force equaliser

120
5 Wheel Brake
40

Ø24
Cables to wheel brakes
42 45°
83

80
98°
Wheel brake lock for parking
LATERAL CONTROL STOPS
Ø24 Adjust the dimension shown to
24 x 1 give +8° movement for the rotor
Ø22

110
4130 Steel head. 2.5 mm 4130 steel
Ø20 50

410
109

5
CONTROL STICK FORWARD LOCK

10
27
1.Useful to prevent rotor blade tips

10
to hit the ground during parking on
windy days.

Adjust
54
Ø10 2. Allows for more space under
the rotor to start the engine by
Ø13
hand propping.
Ø40
Ø26 SAE 4130 Steel 3.Unloads the pilot right hand
during taxiing.
Ø23
2

2
42
12
8

25 x 1.5
2024 T3 Aluminium
(6061 acceptable) Ø28
Ø30

2024 T3 Aluminium

AFT CONTROL STOP

100
E AT LINE
PILOT S
42
80

139
15

24

31

8°

Ø25
Ø22
Ø19

290
25
6130

FWD CONTROL STOPS

KEEL TUBE 40x1 mm

M10
Signature Date Version
Tervamäki Engineering 02
Jukka Tervamäki
Tervamäki
Harmaapaadentie 12A Engineering
00930 Helsinki, Finland

Scale Projection
AUTOGYRO JT-5B
Control Stick Details 1:1 No:06
 0
60 11

R1
5 1.5
8

6
20

8
10 118

10

40 6
123

132
110
13.6

50

140
80°

22
6.5

37
R10
33°
206

21
67
178

70
195
60 6
70.0

0
R1
62
60
103

40 300

20
6
33

210
60

264
10
10

Scale 1:1
R10

60 98
Scale 1:2
40

65

37°
M8
22

Plexiglass
Al 2324 T3
5
R1

Canopy Edge

2.5
Ø10

R1
250

Bronze 4230 steel 1mm 4130 steel

R13
90
Al 2024 T3
Ø4

30
3 3
R1

63
16
0

10
10

12
R4
Cabin Edge
4.5
7.5

15
3

R52
M6
12

24
8

12

45°
10
3

31
6

12
30
40

Ø4

R4 Canopy edge Signature Date Version

Tervamäki Engineering Feb.10,99 02
Jukka Tervamäki
Welded Harmaapaadentie 12A Tervamäki
Engineering

Scale 1:1 00930 Helsinki, Finland

R52

Scale Projection Drawing

AUTOGYRO JT-5B 1:1
Rudder Pedals and Cabin Latch No:07
1:2
 100
3rd layer of
fabric, 90° Spar rowings

758
PVC or Urethane
foam core

Two layers of glass fabric

300 gr/sqm, 45° and 90°

Engine cowling of
Aluminium alloy sheet

510
Vacuumbag molding used to fabricate most One layer of 300 gr/sqm
fuselage parts. Sheet metal and plastic tape glass fabric on each side.
used to make a temporary female mold for Honeycomb or plastic
the integral fuel tank. After removing the foam core, thickness 7 mm.
metal sheets, two layers of fabric added on Edges rounded with
the outside of fuel tank. microballoon/epoxy mix.
353

B
20

1465 A
5

575

311
Two layers of glass fabric
300 gr/sqm, 45° and 90°
B

631
PVC or Urethane

902
1879
foam core
3rd layer of
A-A B-B fabric, 45°
5 mm plywood edge stiffener
2 fabrics on each side, 45° and 90° A 1056
5 mm plastic foam or honeycomb core

Joints bonded with glass powder Main spar uni- 4th layer of
filled epoxy resin. directional roving fabric, 45°

3 Fabrics

B
658

Signature Date Version

B Tervamäki Engineering Feb.10,99 02
Jukka Tervamäki Tervamäki
Harmaapaadentie 12A Engineering
00930 Helsinki, Finland

Scale Projection Drawing

AUTOGYRO JT-5B
Fuselage and Tail Parts 1:5 No:08
 THE MOLD. Steel or brass ROTOR BLADE PRODUCTION PROCESS.
SANDING FIXTURE.
2. Sand or cut the foam core to shape in a jig 3. Layup epoxy+glass fabric on both mold halves.
in three one meter pieces NOTE! See also point 10b. 5. After curing, remove excess fabric by knife.
Sanding tool
Sandpaper
Glass/epoxy Wood

1.Apply release agent and then thin, white epoxy geelcoat onto the mold surfaces and let cure.

8. Layup the unidirectional rowing onto the leading and trailing edges
4. Press the foam on the wet fabric for bonding of the blade.
9. Add the lead weights into the still wet epoxy/unidirectional laminate.
10.Add a layer of epoxy+micro balloons onto all surfaces.

6. Sand the foam core into proper shape using a sanding tool. 7. Cut the foam core into proper width using a knife. 10b. Optional! You can layup the epoxy/fabric
Use a linear jig. CAUTION! Do not cut fafrics! on this side at this point instead of point 3. It
Sandpaper Jig will result in a better bond.

Mold root studs to fit the aluminium 11. Close and press the mold
blade root block for rowing layup. halves together. The excess
epoxy will flow out.

12. After curing remove the blade from the mold. 13. Postcure the finished rotor blade in a
Cut excess fabric and flash by knife and smooth the sturdy jig at an even temperature of 70
leading and trailing edges by wet sanding. degrees Celcius (maximum).

A B

Fiberglass skin layers of bidirectional glass fabric (240 gr/sqm):

Rotor 1) One full length layer in 0°/90°degree orientation
axis 2) One full length layer in 45° degree orientation
3) One layer 75 percent length in 45 degree orientation
4) One layer 50 percent length in 45 degree orientation Rotor balancing done
5) One layer 25 percent length in 45 degree orientation by drilling lead off
A
from the two lead
50 Unidirectional rowing is wound around B rods at the blade tip.
the blade root aluminium block
16

A B

Upper Surface (percent) Ø10

Lower Surface (percent) 100 Geometric Pitch
x y x y 1.5°
.147 1.229 .853 -.819
.358 1.520 1.142 -.946
.804 2.006 1.696 -1.128
70

1.980 2.941 3.020 -1.415 Unidirectional Glass

4.424 4.312 5.576 -1.736
6.914 5.380 8.086 -1.920
9.427 6.263 10.573 -2.059
14.497 7.626 15.503 -2.242
19.607 8.605 20.393 -2.351
24.754 9.243 25.246 -2.417
29.969
35.174
40.292
9.533
9.432
30.031
34.826
-2.455
-2.490
NACA 8-H-12 PVC or Urethane Foam Core

9.030 39.708 -2.494

45.360 44.640 180
8.420 -2.476
50.390 7.666 49.610 -2.436
55.387 6.795 54.613 -2.377
60.358 5.846 59.642 -2.290
65.311 4.850 64.689 -2.178
70.250 3.838 69.750 -2.034
75.184 B
2.838 74.816 -1.860 Rotor balancing done by drilling lead off A
80.118 1.895 79.882 -1.645 42.5
85.060 from the two lead rods at the blade tip. Signature Date Version
1.046 84.940 -1.384
90.016 .343 89.984 -1.051 Lead Tervamäki Engineering Feb.10,99 02
94.995 -.119 95.005 -.629 rod Jukka Tervamäki Tervamäki
100.00 0 100.00 0 Unidirectional Glass PVC or Urethane Foam Core Harmaapaadentie 12A Engineering
00930 Helsinki, Finland

Ø8 Scale Projection Drawing

50 30 AUTOGYRO JT-5B 1:1 (1:2)
Blade Root A-A Blade Tip B-B
Rotor Blades (1:5)
No:09
 JT-5B Autogyro Cockpit and Canopy Cross Sections
Jukka Tervamäki Dec.3.1999

46 1
4 16
3 64
256

30 4
154

2 35
1 62

455 534 564

23

498
98

407
82
18 6
24 5

2 45

256

27 0
341
9
2 89

3 23
8

3 51
7

3 74
4

39 5

41 4

4 18
5 6
1,2,3

13 14

57 0
5 69
15

5 62
10 12

54 9
11
52 8
4 98

586 606 639

622 634 640
1 22

1 80

23 7

28 6
29 6

3 11
43 0

43 9

4 43

4 53
45 9

4 60

46 3

4 62
4 81

5 02

52 2

54 4
16 17
5 63

5 50

5 33

18 19

51 2
20 21, 22, 23
621 583 512
633 467
552
605 415
70

36

36
2 04

23 5

282
3 26
36 5
39 8
4 25
44 4
45 6

564

58 5

60 6

6 27

Sections are perpendicular to the canopy edge in 100 mm

steps. A wooden plank of 50x100 mm (2x4 inches) is shown
inside (red) to fix sections made of plywood.
 JT-5B Autogyro Cockpit Cross Sections
Sections are perpendicular to the canopy edge in 100 mm steps. A wooden plank
of 50x100 mm (2x4 inches) is shown inside (red) to fix sections made of plywood.

21 22 23
18 19 20
15 16 17
12 13 14
9 10 11
6 7 8
3 4 5
1 2

Jukka Tervamäki Nov. 26. 1999