GreyHound- 48"

-
A fast composite aircraft 
Span : 48"
Root Cord : 14"
Tip Cord : 7 & 3/4"
Sweep : 3/4"
AUW = 74 oz

This build stared much earlier but had stalled after the wings were made.. finally after delay of around 6 months the work on the fuselage was resumed. 

This was also a my experimentation with different aerodynamics and materials  and construction techniques... From an aerodynamic perspective, choice of airfoil, multiple control surfaces in each wing and their inter-relatedness in the control of the aircraft, factoring the fuselage for CG considerations .. From construction, materials, use of  composite uni Carbon fiber tape as the wing spar. Kevlar hinges, refinement of my fiber glassing technique, Undercarriage mounting, thin fiberglass cowl molding

There were many learnings, specially how the weight went much higher than expected due to wrong decisions and construction techniques, and how to avoid damaging kevlar hinges, 

The airfoil preparation for hotwire cutting.. note the LE leadins




The Wing with the Built-in Spar and the Kevlar hinges.. (before the covering). This is the stage the excess weight crept in due to the wrong construction technique of trying to fill the gap after the CF spar was laid out , with epoxy rather than lightweight putty. Note the very slight kink where the two different control surfaces (inner and outer) meet


The fuselage being glassed.. note the jig, basically the fuselage is temporarily glued to a wooden stick which is supported and pivots on sandbags. 

d 

The wing mated to the fuselage .. note the UC mounting lugs on the underside (it is a tricycle undercarriage). Also the four control surfaces (two in each wing) is clearly visible, as are the pockets for mounting the servos. In the lower pic the hollowed out front fuselage is also visible where the battery, Rx and others will go in

Below pic also shows the sunken blind nuts in the wooden inserts. Nylon bolts and these will be used to clamp down a Al plate which hold the undercarriage in place.. for the front uc, similar blind buts and nylon bolts are used to a ply plate on which a 4mm spring steel uc has been tied with copper binding wire and epoxied 




The covering of the front fuselage molded out if fiberglass



Coming up nicely


Some finished pic, the canopy is taped with carpenters tape


Ready for test flight.. The motor is 4238 780kv turning a 11.5X6 prop.. AUW including two 4S 1500 mah bty in parallel is 2.1kg..wing cubic loading is around 10 i.e in the region of scale 


 Pre-flight checks being carried out.. using OpenTX the inboard and outboard control surfaces in each wing have been configured  with different weightage.. for pitch the inboard surfaces have more weightage, while for roll the outboard surfaces have more weightage  (60/40)


Take off run.. it was looong.. courtesy the high wing loading.. was apprehensive of a prop strike during rotation, which fortunately did not happen due to the high undercarriage  


In the Air.. the 4 servos are visible, so is the undercarriage . The main undercarriage  is carbon fiber with 3.5" wheels.. the front is 4mm spring steel .. It required @ 60~70% throttle to maintain level flight


Coming in for landing.. and it landed

Overall it is a fast flyer, and the wing loading is high.. need to watch weight closely in future builds, specially when making the fuselage and built up carbon fiber spar.. and importantly not to over-engineer for unbrakeability and consequently add weight   .. the kevlar hinge worked well .. Future modifications would be to increase the wing span by about 20 inches



Comments

Post a Comment

Popular posts from this blog

Flipper - Plank flying wing SAL

-
Image
 This is a Plank flying wing for SAL or bungee The dimensions are  Span = 875mm, Root cord = 260mm, Tip cord = 160mm, sweep = 60mm. 20mm constant cord full length elevons The wing is hotwired out of EPP and then laminated with thin iron-on laminating film. The airfoil is PW51 7% thick at the root and PW51 7.5% thick at the tip. It has a 1.5 degree washout and a 45mm dihedral at the tips.  It has one 2mmCF spar glued to the bottom positioned at 40% cord. There is also a spar on the top surface biased to the rear to avoid elevon reversal. Two 9g servos are positioned vertically into slots cut on the top of the wing. The position of the servos are driven by the thickness of the wing at that part and distance from CG. The full length elevon is a tapered 3mm balsa with fiberglass lamination. ....Note I had to increase the elevon cord at the tips by 12mmto improve the control response (after the first flight trials) The fuselage is a 3mm CF rod glued onto the bottom of the wing...
Read more

Angor-Rot & Hot-Rod hotliner RC plane

-
Image
 Fast, hotliner design These two are built for speed, and unlike a 3 surface (wing , tailplane and rudder) design, they are wings (delta). The thought was having the max wing area for a given wt and strength and with the least friction/profile drag, and of course ease of construction. (ignoring  difference in Induced drag). Construction is composite, foam, glass fibre, carbon fibre and vacuum bagged,  resulting  in a very strong lightweight structure for its wt. Airfoil is PW 51, with a 1.5 degree washout at the tips. Small wing tips are added to draw out the tip vortex. The LE is reinforced with CF. The wings tips and the centre section of the underbelly has some CF  reinforcements built in. It has 2 layers CF tow of different lengths acting as spar. The paint pattern has been painted directly onto the skin and then vacuum bagged. The control surface hinges are live hinges built into the glass fibre skin. The servos and push-rods are embedded with the wing. All...
Read more

WitchCraft

-
Image
DESIGN This design explores the region between a plank and a swept wing flying wing, and to try and get the best of both worlds to whatever extent possible.... The major balancing acts were being efficient across a large speed range, good C l /C d , less twist, and maintaining good flight characteristics. PLAN & DIMENSIONS A span of 1200mm was chosen to keep it a one-piece plane.  - Sweep is a very moderate 13 degrees measured at LE, and even lesser when measured at 1/4 AC line. - - Aspect ratio =- 6.3... (adequate wing loading with the set span of 1200mm span) - Taper ratio= 0.65 and Twist - (-)1 degree..... (close to elliptical lift distribution, less induced drag, while maintaining decent Re and flow characteristics at the tips, good stall characteristics) - Airfoil is PW51.. (good cl/cd, adequate +ve cm, and minimum trim losses).  - A central tailfin is chosen over wing tip fins.... (due the the less moment arm and the issues arising out of a badly designed wing tip ta...
Read more