WitchCraft

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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 Cl/Cd, 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 tailfins, chances of which are high)
- Fuselage was kept to the minimum .. (reduce drag)
 Elevons is of constant cord. 
A sharply raked symmetrical wing tip.... (to pull the tip vortices outwards and have decent separation between the tip and elevon outer edge)  
---The design and parameters was tested and fine tuned over couple of iterations on XFLR 5.

CONSTRUCTION

Composite construction was chosen keeping in mind the strength, weight, and required dimensional tolerances, and of course ease of construction. 

The wing core is hotwired out of EPS foam. Top and bottom surfaces has a 15mm wide multilayer CF tow laid  out spanwise with a vertical 1x3 CF section beneath it acting as a shear webbing. There are CF cloth reinforcement at the wing root and tip. The LE and TE also have CF tow laid out spanwise for additional strength.  On top the the wing is laminated with one layer of 50gsm fibre glass at a 45 degree bias with an addition layer close to the root. The elevons and bottom hinged and have a fibre glass live hinge.  The whole thing is vacuum bagged and cured. This makes a light but very strong and rigid wing with good surface structure. Also the elevons are gap sealed with a strip of thin strip of mylar.

The front fuselage a balsa CF sandwich with is attached to wing in a slot cut in wing. The canopy, cowl and bottom cover is 3D printed out of PLA. The undercarriage is a mono wheel housed in a 3D printed wheel cover which is attached to the wing lower surface. The rear fuselage is just a 8mm CF tube attached to the top surface of the wing and a fixed tail fin, a balsa fibreglass sandwich, is slotted onto it at the rear. .. (the alignment has to be correct). All was done to keep drag to a minimum including a TE bat tail fairing.

  ELECTRONICS

As a fast plane, it is a 4S setup. Tmotor F60 1750Kv motor, 40A ESC, 6x5 prop, 2 x 9gm servos and a 4S 1500mah bty.

BALANCE AND TRIMMING

Balanced at 9.5 cm from root LE. Slight (around 3 degrees) uptrim. With a AUW of 715gms and a wing area of  22.8 dm sq, its wing loading is 10.28 oz/sq ft/ cubic wing loading at 6.57 oz/cubic ft, stall speed  around 25 km/hr.

FLIGHT

Maiden flight was on 28/09/2025. It climbs at 25% power, awesome glide, turns sharply without loosing height. A little downthrust would need to be added to prevent nose up tendency on power. I had to constantly push the nose down when adding throttle.... A blast and exhilarating aircraft to fly.  It retains energy nicely, characteristics are similar to a Swift.

some more pictures of the aircraft


coming in for a low pass w/o power.. (i need to get a good folding prop)
climbing out after the low pass




Here is a trimmed flight video of the maiden flight   https://www.youtube.com/watch?v=jeP0VKtGbyk   

and here is a "shorts" of the same          https://youtube.com/shorts/BudZwWl7bw8

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