Stryker F-27C Build

ToDo

Outstanding Questions

• can stryker be launched by the wing LE (for safety) - a bit like PK launches the Battlewing

Weights

• fuselage + nose 130g (minus screw in nose)
• aluminium motor mount + glue + binding + CA 25g
• 3-piece hatch 20g
• all velcro + glue 15g
• motor+prop+adaptor 80g
• battery 170g
• 2-piece receiver 15g
• ESC 30g
• servo x 2 + linkages + tape + CA 20+10g
• 2 fins + glue 35g
• 2 elevons 30g
• paint 30g ?
• LE tape 10g ?
• total estimate 620g 21.8oz ( wt = 130+25+20+15+80+170+15+30+30+35+30+30+10; print wt,'g ',wt/1000.*2.2*16,'oz' )
• design weight: 620g, 22oz

Weight Log

• fuselage + nose (without screw) + motor mount + 2 fins + 2 elevons + painted + velcro = 220g (predicted 130+20+30+30+20=230g)
• final weight is ~610g (~ original spec)

Build Sequence

• sand fuselage mold flashing off (esp. TE and LE)
• cut receiver antennae holes (melt with hot wire)
• melt oblique slot for servo leads
• melt trough in floor for ESC base
• build and attach elevons with white glue (acetone wash TE surface)
• build motor mount bracket (drill, bend, cut off excess, bevel front top edge, roughen with file)
• cut slot for motor mount and check fit
• hot-melt glue in motor mount (wood first, then metal)
• bind rear of motor mount (wood and metal) with cotton and seal with CA glue
• install 7" propellor and trim fin mounts as necessary
• CA glue velcro for nose and hatch, plus hatch hinge cloth (on foam) - (glue doesn't hold velcro well - use magnets next time?)
• test balance the plane with motor, ESC, battery, servos-rods-horns, receiver x 2 (adjust planned locations to get CG correct, remove screw from nose if possible)
• install velcro for battery (base and strap) and receivers
• fine-sand all parts to be painted
• attach fins (hot glue in slot, insert fin, hot glue top and bottom leading tips - need to revise: glue cooled quickly and was too thick to slide fin into place properly)
• wash foam surface with acetone and paper towel
• hand paint very thin coat of white acrylic undercoat on foam areas to be painted
• hand paint thin coat of yellow, wait to dry, second coat
• hand paint black parts, 2 thin coats
• tape LE with FG tape (4 segments per wing)
• centre servos using transmitter
• hot-glue servos and tape wiring (install servos with pushrods fitted, ensure rotor is centred in cutout)
• tape servo hatches and wiring (packing tape, iron on, CA LE of tape)
• install all electronics and hardware (AR7000 needs both receivers)
• check motor (freedom, direction) and elevon operation from transmitter
• CA dob on motor screws
• push in plastic fuselage "bridge" (above receiver)
• set elevator and aileron movement range (per Stryker manual)
• balance and fit 7x5 prop
• recheck balance point
• check motor and elevon operation from transmitter
• range check

Design Details

final setup

• 9mm deflection for aileron and elevator movement (top hole of long horns, longest 9g servo arm and top hole, 40mm wide elevons)
• CG ~10mm in front of recommended (finger holes in launch cutout)
• 7x5 prop (heavy)
• 1.0 kg thrust with 7x5 at max throttle (0.8 kg with 7x4)
• 45-50A HK ESC
• 2218 1860Kv heli motor

• 2200mA 3S 20C LiPo

• paint: 3 acrylic coats - undercoat + 2 x flouro yellow
• trim equivalent to 1/3 of the up elevator trim range on DX7

motor mount

• specs
  • 27mm diameter
  • 19mm and 16mm spaced mounting holes (M3)
  • needs 5mm hole for shaft, with 1mm deep countersink 8mm wide (Note: circlip must be free to rotate)
  • increase countersink diam and depth or add 2 washers to maintain clearance from circlip
  • need 5mm clearance between mount and motor for rotation and 2mm extra for thrust-line correction range
  • vertical segment = 27+5+2 = 34mm (includes rounded top)
  • horizonal segment = 60mm (includes chamfered end)
• materials
  • aluminium density is 2.7 g/cc

  • 8mm arrowshaft 57.5cm weighs 20g --> 0.35 g/cm

  • long wooden base to prevent fuse bending under full power (how far into fuse can I go?)
• alumunium strut 3mm (mount motor same height as original)
  • buy 3mm x 12mm strip
  • screw onto wooden base to allow shims (heavy! just bend strut or shim at motor mount?)
• how to prevent forward flex of strut under full power?
  • strut webbing? but motor in the way!
  • thick/wide strut

• stacked strip and wood

  • simple and neat, small metal shadow,
  • 110x12x3mm aluminium strip finishing at first slit in foam (wt=10g)
  • 6mm balsa underneath (all the way to the ESC heatsink position)
  • sand strip for glue and paint adhesion
  • sandwich with 2 x strips of 4mm balsa (to thicken and increase bonded surface area)
  • bind sandwich with cotton (especially adjacent to bend) to prevent separation of glue
  • consider underlay of FG cloth which overlaps sides of channel to increase surface area (will be heavy and probably not needed)
• single U-channel bracket (~120 mm)
  • single piece solution but large metal shadow
  • epoxied into foam and spread within ESC space to glue to sides (allowing room for ESC)
  • edge panels reduced to 3 mm total thickness for bend and motor mount
  • centre web removed for ESC cavity (to spread sides to foam)
  • est. aluminium weight 10-15 g
• full width mount fitted to FG tube arrowshaft
  • lightest solution (10g) and least metal shadow for RX?
  • 1.2mm sheet is strong enough (but will bend on impact) ~ 5g
  • 6cm FG tube with further 6cm of 1/3 sector tube ~ 3g (+ 2g glue)
  • alum mount epoxied into 30mm slot cut in FG tube
  • tube is bound at slot end to prevent splitting
  • consider a ply gusset in a slot on top of tube to reduce flexing of aluminium bend, especially if bracket is high to clear unmodified foam height
• wooden version of above?
  • No metal shadow, but may not be lighter than aluminium version
  • 3mm ply end plate, pierced by CF tube, and glued flat on back edge of fuselage
  • plate supported by horizontal and vertical gussets slotted into FG tube

hatch

• to change battery, rear hatch segment must be removed because of the short ESC leads
• aim to remove 2 hatch segments starting from back tip, with front section remaining in place
• front section removable for satellite receiver access
• hinge-cloth at front and connecting each segment of hatch
• attached by velcro (hooks on hatch or foam?)

elevons

• originals 30mm wide, 5mm thick?, weight for both w hinges and horn 24g
• 40 mm x 5 mm (stock is 30 mm, PK's are 36 mm, 2K says up to 50 mm is OK, fins are 5mm thick so stock elevons may be same)
• coat with dilute white glue for stiffness
• install with cloth hinges
  • thin gauze type used previously - narrow spacing to prevent distortion of foam
  • perhaps 6 pairs per elevon to help stiffen the TE
  • white glue and dope for TE and elevon respectively
  • may need to sand foam to roughen for gluing hinges

fuselage preparation

• LE glass tape
  • wrap around tips
  • to handle curves
    • slit edges of tap and limit width if unsightly on yellow, or
    • use segments and short overlap pieces
  • very sticky tape doesn't need to be ironed on (goes on top of paint)
• glue on velcro (assumes hand painting around velcro patches)

paint fuselage (colour on top only)

• paint (need to test on foam part)
  • testors model spray enamel paint, "Model Master"?
  • Tamiya spray cans
  • Faskote (cheap water-based)
  • general recommendation seems to be acrylic paint (light and foam safe (except solvents))
• may need an undercoat for tape on LE to get acrylic to stick to the plastic
  • what about fins (all greasy plastic!)
  • flat paint finish to allow repainting and no difference between hinge tape and foam?

  • can use acrylic house paint - http://www.rcgroups.com/forums/showthread.php?t=45571

    • thin 50/50 with a 50/50 mix of alcohol and water (water slows the drying process, is OK for flat)
  • practice painting to check how much to get coverage, colour opacity and evenness over foam and hinges
• base (purely to prevent stains and dirt ingress)
  • optionally no paint (smooth foam will be just as good at staying clean)
  • put masks over servo cavities
  • paint underside with clear enamel
• top
  • put masks over fin slots, canopy velcro spots, nose velcro spots, electronics box, motor mount
  • mask elevons
  • hand paint flouro chrome yellow
• trim (hand paint all black)
  • elevons, nose (avoid or mask velcro spots), fins, motor mount
• fins
  • hand paint black enamel (test) with masked slot zones
  • install with hot melt glue, especially leading points and
• hatches and nose

  • velcro for nose and hatch covers, and for holding battery (face & wrap), RX and ESC

• colour scheme
  • flouro chrome yellow on top with all-black nose, fins and ailerons; bottom unpainted (white)

References

• Bullet Proof a Stryker - http://www.rcuniverse.com/forum/m_8631014/mpage_1/key_/tm.htm

  • 0.74 kg AUW (orig 0.62 kg)

• Images (incl colour schemes) - http://www.rcuniverse.com/forum/gallery_thread.asp?threadID=2947262

  • and http://www.rcuniverse.com/forum/gallery_thread.asp?threadID=8631014

• 2K info on all aspects of Stryker - http://www.2kool4u.com/stryker/strykerelevons1.shtml

• web calculator - http://adamone.rchomepage.com/calc_motor.htm

• web calculator - http://brantuas.com/ezcalc/dma1.asp (this one doesn't predict current at all well)

• MANY FMS models

  • http://www.placedeleurope.fr/Modelisme/Modele%20FMS/

• light stryker building techniques - http://www.rcgroups.com/forums/showthread.php?t=866913

Combat modules?

These are to interface a normal electric setup to the ParkZone X-port Sonic Combat Modules.

• http://www.rcuniverse.com/forum/m_5863487/anchors_5863487/mpage_1/key_EZ%252DXPORT/anchor/tm.htm#5863487 - EZ-XPORT (general X-port interface)

• http://www.rc-cam.com/combat2.htm - RC-cam's PIC module, specifically for the SCM (still available ready-programmed?)

Misc Info

Turnigy 450 H2218 Brushless outrunner 1860KV (helicoptor motor from HobbyKing)

• Model: 2218
• Turns: 5
• Cells: 2~4S
• Kv: 1860rpm/V
• No load Current: 1A/10V
• Max power: 500W
• Weight: 67g
• Shaft diameter: 3.17mm
• Dimensions: 27.2 x 36.5mm
• Recomended ESC: 2~4S/50A

Fuselage servo box dimensions: 25L x 24.5H x 15D

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