PELICAN - 3 meters - Build log

 This is a build log for a large plank flying wing. I named it "Pelican".. loosely based on the Pelican mentioned in nestofdragons

The basic dimensions and calculations are as below.. 

The airfoil is phoenix

The central section and each of the outer section are meter each. The outer sections have a dihedral.  

It would has a central elevator and two outboard elevons/ailerons.. synchronized through TX mixing 

The wings are hotwired out of EPS (closed cell polystyrene- thermocole) . It has a 1.25 inch top and bottom unidirectional carbon fiber cap spar and a 3 mm ply compression web across the whole wing. The whole wing is laminated one layer of 100 gsm fiber glass (unfortunately that was the lightest FG I could lay my hands on).. with the LE having a extra layer to form a Dbox

The  wing is in 3 pieces (each of one meter), The outer panels are joined to the central portion by  rectangular aluminum bars and also locked with 4 x 3mm bolts 

 All the electronics , except for the battery are housed in pockets carved out in the underside of the wing. Only the battery will be housed in the fuselage

It has two tractor motors , on pods attached to the wing on either side of the fuselage

The fuselage itself is minimal,. Wanted to avoid molding a fuselage , hence made out of readily available material and shapes.. .. The prime structure is a FG tube (used in ht switching), which acts as a saddle for the wing. In the front there is a  ply keel which supports a pod made out of foam and fiberglass to house the battery,... the extension of the tube in rear is the the seat for the vertical tail.

Below are some pics

The wing panels, hotwired out of EPS

The  main Spar, the ply compression web,  the joining gloves,  the joining bar   for the inner and outer panels

The joining glove and the AL bar.. note the built-in dihedral

The full spar

The Front D box, along with the spar compression webbing .. which includes the wing panel joining glove. The uni carbon fiber spar would be on top of this to make the complete spar.. before being covered with fiber glass to form the D box

The front Dbox with the joining glove clearly visible

A dry fitted (just taped) central panel for better depiction

The whole wing with the panels glued , and joined using the AL joining bar.. they are not yet fiberglassed.

A close up of the facing ply ribs of the inner and outer panels.. the glove for the joining bar and the AL securing lugs are clearly visible

The tool used to make the shallow groove for the carbon fiber spar.. It is a layer of carbon fiber , covered with a layer of fiber glass.. the width being the same as the width of the uni carbon fiber tape

The wing panels being fiber glassed ...... Note the Carbon fiber cap strip faintly visible through the fiber glass covering. It is this which gives the wing immense bending strength,  the fiberglass covering providing additional bending and primarily torsional rigidity. 

The construction of the central elevator and the frise ailerons.. the elevator and ailerons are  cut out from the wing panels after it is fiber glassed .. joining is with Robart's hinges

Note the pocket in the lower side of the outer panel for  housing the aileron servo

The robart's hinge, and the LE of the frise aileron is visible below. For the ailerons the hinge is closer to the underside surface of the wing so that during the upward movement of the control surface , the leading edge of the control surface sticks out into the air flow to create drag.. which will counteract adverse yaw

Similar pics of the central elevator. In the central elevator the hinge is centrally located between the top and bottom surfaces. No need for a frise type of movement... the pockets for the electronics in the underside .. two of them in the central wing.. either side of the fuselage.. are clearly visible, along with the groove for wires

The Fuselage.. the main fiber glass tube with the three smaller dia vertical tube inserts is clearly visible.. The  three vertical tubes will pass through the wing and will be clamped down with three nylon bolts.. latter on the three tubes will be trimmed in length to match the thickness of the wing at the particular position of the cord

It is absolutely vital that the holes for the vertical tubes are in-line and  accurately aligned in the Y and Z axis (looking from top looking from tail to nose). Measured and rechecked it multiple times before committing to drilling . The vertical tubes pass through and through and stick out of the lower surface by 1 mm. The holes in the main tube are a tight fit and they are bonded with epoxy. This ensures that they are able to withstand lot of force on all the 3 axis.. specially in X & Y 

The plywood keel fixed to the lower part of the fuselage is visible below. The shape and space for batteries will be formed out of XPS foam (blue) which is glued to the keel and the tube. 

Note the wooden insert and the small hole .. the insert has a small dia Al\L tube inserted through it which is 1.5 in long. This is for inserting the 4mm spring steel undercarriage skid.. a similar insert and AL tube is fixed near the nose.

The battery compartment clearly visible below

The undercarriage skid  inserted in the holding holes .. (Pearl, the cat is a big supporter .. she sits nearby patiently observes whenever I am working on my aircrafts )

The OD of the main fuselage tube is 25 mm and thickness is 1.5 mm.

Finally completed it.. To make it transportable in my car the aircraft is in 5 parts.. 3 pieces of wing, and 2 pieces of fuselage.. and additionally a take-off dolly

At field on 28th Feb 2021

The controls 

Pitch - central elevator and additional 40% elevator inputs on the ailerons.. 

Roll - only ailerons

Thrust - no differential thrust.. both motors run on same speed

Rudder - no rudder

Assembly in progress

Me with the assembled aircraft.. the thing in front of the nose is additional weight to get the CG right

With the "gang" .. the size is apparent

Take-off... nearly ran out of runway when the dolly drifted to a side.. she is sensitive on pitch.. need to dial in more expo on elevator

In flight

First flight was with a 10% static margin

Basic flight characteristics.. 1) a bit nose heavy 2) No adverse yaw during roll 3) Thrust angle was fine (no differential thrust) 4) Yaw and spiral stability is adequate 5) sensitive in pitch, fixed with 30% expo

Here is a video of the first flight. ... the dolly has roller skate wheels

https://www.youtube.com/watch?v=EOoITrTrQ7k