Javelin - high performance flying wing

 Javelin is a high aspect ratio swept flying wing. It is designed for high performance  and uses modern airfoil and construction techniques. 

The planform of the wing is as above with inboard flaps and outboard elevons. It has a fuselage pod and wing tip vertical fins, 

Span : 1700 mm

Root and Tip cord : 175 mm

Sweep : 22.5 degrees or 353mm

Flaps : length 240 mm, cord 30 mm, starting 25 mm from root at the TE

Elevon : length 340 mm, cord 30 mm, starting 3 mm from tip

Airfoil : HS 522 standard thickness and camber. It is low drag , low Re airfoil . The details and the .dat file can be found here  https://www.aerodesign.de/english/profile/profile_s.htm#hs522

Twist : 4 degrees

AUW : 840 gms 

Electronics: 2212 1400kv motor, 30A esc, 9X4.8 prop, 4 x 9gm MG servos, 3s 2200mah bty. (the electronics used are more from what I have, rather than the most suited)

Wing Area : 297500 sq mm, 461.13

Wing loading : 9.36 oz/sq ft, and Wing cubic loading : 5.2

CG :175~177mm from LE at root cord... or 460mm swept spanwise from root LE

This is my design, you can use it freely

The wing is hot wired out of blue XPS foam. Formica templates were used

After considering the pros and cons of a three piece wing vis-à-vis a two piece wing , I decided  to go for a three piece wing. One central section firmly bolted to the fuselage, and two outer panels.

The wing has a carbon fiber top and bottom cap spar at 30% cord, and the leading edge also has a carbon fiber semi D box. It has balsa tips. The whole thing is covered with fiber glass and vacuum bagged. The tail fins are 3mm balsa carbon fiber cloth composite 

The central portion of the wing being vacuum bagged

The inner wing tip with the joining spar holes. They are covered with tape before being vacuum bagged

the central portion being vacuum bagged. I forgot to put a layer of tissue paper on  the top side to absorb the excess resin. This will be corrected when I bag the outer panels. Note the small hand vacuum pump used. This is a brake bleeder pump. I was able to pull 19 in of vacuum with this. Pay great attention in sealing the bag. Lookout for wrinkles in the bagging film , this is where I found my leaks

This is the outer sections being vacuum bagged. I found that the valve was unnecessary, and in fact another failure point in sealing. I eliminated it and inserted the tube straight, making sure it was sealed tight at the place where it entered the bag, and placing the open end inside the  bag between to cardboard pieces. Make sure there open end is placed on top of the bleeder cloth

Here is the wing with the central and the other panels joined. The mid wing joining and the flaps and elevons are visible

The hinge for the flaps and elevons is kevlar, which is sandwiched between the foam and the fiber glass outer skin

The tail fins, which balsa and carbon fiber cloth  composite (vacuum bagged)

Here is a view of the underside of the wing, the central portion, the two outer panels, and the tail fins

The top side view , note the flaps and elevons

A view of the end wing tip, where the tail fin will be attached. This is also covered with carbon fiber cloth 

A closer view of the mid wing tip. The joining spar holes are clearly visible

The wing without the electronics and wing tips comes to 295 gms

The fuselage is made of fiber glass  using "lost foam " method. 

The fuselage plug, being covered with packing tape, before being fiber glassed.. 

After covering with packing tape the whole plug was waxed, I used car polishing wax.

The fuselage has three layers of @100 gsm fiber glass, and a carbon fiber strip. Layering the fiberglass onto the plug proved to a difficult job. The fiberglass was sprayed with a spray on adhesive and tacked to the plug, but it was difficult to do it cleanly , specially over compound curves (the cloth weave not being satin, also made it more difficult). It was then wrapped with peel ply  and then with paper towel and then with bleeder cloth.. and then put in the vacuum bag.

The fuselage being vacuum bagged

After 24hrs the bag was opened. I realized that in some places the layers of fiberglass got detached  and had moved, resulting in wrinkles. A round of light sanding was done. The cockpit cut. The cockpit also provided an opening to pour in petrol into the fuse to melt the foam.  

Some places of the hollow fuselage required reinforcements. This was done by placing fiber glass cloth over the weak patch and covering it cyno and pressing them together. This is very effective method, it adds great strength  and is also light 

The fuse after the foam was removed. The two uprights (black and red) are wing securing posts glued to the fuselage

 V1 .... with the electronics in place it turned out to be very nose heavy, and had to add quite some weight at the back. 

Maiden take off...  Flew well, however after two test circuits it suddenly lost radio signal and crashed & the fuselage broke.. will repair it

The fuselage was repaired .. Here is a flight video after the repairs

https://www.youtube.com/watch?v=Kiij_BTFus0

V2. Changes

1. A wing fence was added 400mm from the root apex. 

2. Vortex generators were added on the wing tip extending 380 mm inward from the tip.. this covers the whole elevon

These modifications allows tighter turns at lower speeds