Jörn Meyer original text
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Jörn Meyer original text |
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Jörn Meyer: Joern.Meyer@otto.de Hi Erik, I saw some new pictures at the aerodesign.de pages and
at f3j.dk. Very interesting... but I wondered how much
resin+microballoon you use for glueing. I think we use only half of them.
By the way, f3j.dk is one of my favourite sites. They
are very, very good. Congratulation! Corella-"Klon" (Dieter's words) building
instructions? Hmm, how to start? Our normal weight is 2050-2070g for the 70dm2 wing area,
the v-stab area is similar to the Trinitus. Fuselage complete 740-750g. The extrem light version only for sunrise/sunset
conditions is nearly finished, 1850g will be very realistic. The wing mold is devided in 5 sections. Main 120cm
aileron 76cm
tips 35cm (outer aileron) Normal Version, Glass layers and 1,2mm Herex
supportmaterial Layers:
Out
80
80
49 Inner
80
49
25 Light Version, Glass layers and 1,2mm Herex
supportmaterial, tips 1,0mm Rohacell Layers:
Out
80
58
49 Inner
80*
49
25 *behind mainspar 58g Dieter uses 25 glass + 66 carbon/aramid for the outer
layers and 1,2mm Rohacell support material... Light version = advantage? One prototype (middle: out 105 in 58, ail: out 58 in
49, Esprit fuselage, 2050g) dominated last year with highest starts the
f3j-groups. Windspeed 1-2m/sec. During the contest the wind became appr.
3-4m/sec. I put some weight (260g) into and I was NOT the highest after
start!! I took my "normal version" and was back in the
competition. The torsion of the "weak" ailerons became a
handicap... We use the 287 hardener, so you can dry the wet glass
with a newspaper, but not too much... The inner, outer layer and the supportmaterial is put
into the mold in one step, the main spar is build in additional molds. Evolution of our middle section 1,2x(0,24+0,233)/2=0,284m2)
Stützstoff = support material (calculated weight) Herex 1,2mm (80kg/m3), 25,5g Balsa 1,0mm (from A. Hortzitz) 23,8g Schale oben/unten: weight of layers = weight of resin+hardener (calculated)
Flügel-Steg
Balsa The spar in front of the hingeline is 3mm Balsa between 80g glass under
45° (9-10g). The 18g-spar was made from 2x3mm Balsa + 3x80g glass. Klappen-Steg Aluminium 6mm At first we used 6mm Aluminium tubes for the spar behind the hingeline
(as Dieter did). Klappen-Steg Carbon sock No comment! Rumpfauflage Plywood rips for the screws mounting the wing to the fuselage Verklebung H+H (Harz+Härter=resin+hardener) Glueing the top and the bottom of the mold and the spars to each other. I
did not notice the weight of the micro balloons, (the light one’s from
r&g) it’s just experience… Kabel/Servos Weight of leads and servos + 3-4g for “Ruderhörner+Gabelköpfe” Ballastrohr=ballast tube ASD = Anschlußdifferenz Difference between Gesamt (=total weight of the
complete flyable wing) and the whole weight of the parts above. That
means: colour and all this little parts which you need and which are not
mentioned before you can find in this position. Gesamt (=total weight of the complete flyable wing) Servo/Kabel/Ballast All that parts which are necessary to fly. But if you
compare your hardware you have to exclude these parts Bereinigt The compareable weight of the wing without anything
additional. To support a D-box there are some "Rippen"
rips (?) from 2mm Balsa (vertical) in the wing parts. In the main
section 4-6 (2-3 right/left from the middle), aileron 2 rips. Near the
servo there is the rip also behind (!) the mainspar to fix the surface
if there increases pressure on the flap and the servo (start/butterfly).
(Maybe you know this problem from the “Corrado”, with its 1,6m
middle-wing, which is pretty weak in this area, especially in butterfly-
or start-condition you can sometimes see where the servo is glued to the
middle section…) 6 servos in the wing and lots of electric leads... The
most weight is the pvc isolation of the copper. Do you know "Kupferlackdraht"
with the transparent colour isolation? (It's that stuff which is used
for the anchor of an electric motor). Than you can safe more than half
of the weight!!! Column 1 Schale oben/unten. Layers: out 80g glass, in 80g glass Column 2 (in progress, not flown) Schale oben/unten. Layers: out 93g carbon, in D-box
2x49g glass, 49g glass Column 3 Schale oben/unten. Layers: out 105g glass, in 58g glass
Column 4 Schale oben/unten. Layers: out 80g glass, in 80g glass Column 5 (in progress, nearly finished, not flown) Schale oben/unten. Layers: out 80g glass, in D-box 80g
glass, 58g glass Column 6 (in progress, in mold) Schale oben/unten. Layers: out 80g carbon, in D-box 49g
glass, 27g glass Holm = mainspar 1x24cm The (main-) spar of the main section measures
20x13x1196mm. Supportmaterial sandwich: 3mm Depron (4x) + 163g glass
45° (5x) Glass bags/wingjoiner 9x14mm (by emc-vega) Rovings symmetric top=bottom: 13x120cm 1x114cm 1x108cm... Aileron mainspar: 2x76cm 1x70cm 1x65cm... 1x20cm Tip main spar: 5mm Balsa 90°, 1 Roving top/bottom We pull our wet rovings through a 1,7mm hole and dry it
then with kitchen paper, two (!) times. Not a very great idea but it
works. The mainspar has a weight between 185-190g (1 time dryed) and
170-175g (2 times dryed). It's ridiculous. Minus 15g for 53m rovings =
-0,3g per meter safed. Wiping with the kitchen paper is 1 important
point. Another maybe most important point seems to be the temperature. (Un-?)
Fortunately we forgot to stop the heating in our working room. The
hardener (287) and resin were standing on the heating. Temperature of
hardener and resin maybe 40°C, roomtemperature 25-27°C, we build our
lightest mainspar!! In the end 34g r+h for 53m (=85,5g) rovings. Instead of 3mm Depron we sandwiched 3 layers Balsa 90°
with 2 layers 163g glass between the Balsa or added carbon sock sc3140
(230g). The last is obviously the best. An intermediate is the Depron
spar as mentioned with the carbon sock (245g. This was the 1. attempt
with a carbon sock and I used too much resin. Normally carbon sock +
resin = 35g. The weight had to be between 215-220g). The f3b-guy Dieter
Perlick uses Balsa 90° with carbon sock. Dieter Köhler takes normally 8x1,5mm Balsa (0°) +
9x80g glass (45°). I think Balsa 90° would be better... Aileron There is no surprise. Depending on the light- or
weakness the weight is between 210-240g each part without rc. Tip 33-38g (1mm Rohacell-1,2mm Herex) without rc Fuselage Total length/weight (mm/g) Cone 355/44-60 (Corella 2000 = 300mm/?) Wing-mount-section 315/51-60 (wingroot 240mm. Notice:
from leading-edge wing to top of the cone max. 420mm!) Tube max. 850/58-72 (800 = max. useable length, we need
40-50mm for glueing to the part above, the rest can be shortened) Stab-mount-section 145/12-13 (stabroot 125mm) Servo-plate 55-60g (glued to the rear section) Most of the weight we reduced by vacuum bagging of the
rear section. We use a cnc cut iron cone/positive 900mm with 40-20mm
diameter. Best results with 1. layer carbon ud (emc-vega: cg 245) on the
positive 2. carbon sock (sc 3200) around. Without vacuum: 72-75g,
vacuum: 61-65g!! But we work with a positive. As you know we have to
finish it by sanding and filling the micro holes than comes the colour
(appr. 7-10g). The Corella 2000 distance between wing and stab is
760mm but a little too short. Maybe 780mm will be the optimum. Servoplate: similar to Trinitus, but we take: 4 rovings
around the plate and at the top (beside the plate) 4 rovings (1 at each
edge) every 5cm 4 additional rovings (1 at each edge). V-Stab The v-stab is very traditional, outer layer 49g inner
25g, additional 25g or 49g outer layer root until half of the
rudderlenght (only rudder). Supportmaterial 1,0mm Rohacell. The spar is
4mm Balsa 90° covered with 58g glass under 45°. To mount the stab to
the fuse we use one 3mm screw. We screw it in a 5mm cheap plywood rip
which is doubled with 1mm plywood in the center of the stab from the
leading edge to the hingeline. Total weight: 68-72g. For F3J it works
very well. A stab for a heavy duty f3j-soarer became with balsa and
“wet” clothes 82g. Dieter has a mold for his mainspar and does not use a
rip in the center… I think that’s it. Jörn by Reinhard. I mailed him already. Philip builds his f3b Sunburn with the prepregs, Reinhard his Europhia. As Philip told me the prepregs are ready for use 1,2 or 1,5 mm x 25mm (?) and long as you want (?). (By the way I saw 2 years ago Karl Vallant giving some prepregs to Gerhard Pollack who uses the prepregs for the Starlight 2000. The length maybe 2,5m). Vallant uses nf24 rovings which are pressed with high pressure under high temperature. The fibres are 100% unidirectional!! and part of resin (50%/50%) in this composite is ideal. Karl Vallant has a little commercial glassfibre production making some parts for these Cargolifter Zeppelin guys. Working with is a little different: instead of getting any rovings wet you have to cut the prepregs with a saw (happy carbon powdering!) at the size you need and glue it under vacuum to the outer layer. In the end it is stiffer with the same weight. So far Philips explanations. We did not have any problems with the paint the last years. We use for the wingparts wax and the paint I mentioned. If there is more than 1 day between painting and vacuum we take ACETON very very smooth with a kitchenpaper over the painting to get it a little rough. Sven Hollenbeck told something about ANTISIL (Anti-Silikon, because the carpaint includes wax) in addition to the paint.
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