Author: Barry Twilton

Earlier this year I tried a new flying change – slope soaring using a Spectre flying wing. Following this initial experience, I decided I wanted to build my own conventional type of glider and started looking at kits and glass/carbon fibre planes. However, having spent many years messing with, building and racing cars, I thought it may be a interesting idea to try some of the techniques and methods used in developing and building car bodywork, hence this design and build exercise.

I started by researching designs using information from various sources including:
http://www.phoenixmp.com/articles/slope.htm
http://www.rc-soar.com/tech/perfanal.htm
http://charlesriverrc.org/articles.htm
http://www.flyingobject.com/

My first activities were to develop a design spec based on the phoenixmp article, full size wing drawing and produce a short piece of wing section from a split aluminium sheet mould to understand the weight and strength. The spec is attached to this blog, where ‘1850 Mk1’ is the current build which started with a target 12oz / ft2 wing loading (I was dreaming…) and ended up at 21oz to achieve the balance, hence the flying brick. The ‘1850 Mk2’ worksheet shows my initial thoughts for my next build with the primary focus on reducing weight.

Design Spec v0.2

To give an idea of the build, I have included some photos showing the wing moulds and views of the model.

Key points from this initial prototype:
– the tail and back end of the fuselage needs to be lighter;
– extend the nose length to reduce the ballast up front;
– reduce the size of the ‘V’ as this was based on the suggested ratio, hence change in ‘V’ tail spec;
– change the wing build method from two single sheets of 200g Woven Roving layed-up across both halves of the mould and folded over the spares, to producing two separate halves then join together over the spares;
– Use a metallic silver paint base coat instead of normal cellulose to reduce weight;
– reduce the diameter of the fuselage where the back used a split and tapered 1 1/4 “ waste pipe and rolled lemonade bottle for the front, this will necessitate putting the ‘V’ tail servos in tandem;
– Stiffen wing control surfaces.

The maiden flight was carried out at Burton Dassett with a westerly wind, not the ideal direction, limited lift and turbulent. flew my wing first and struggled with lift at times as it is 50% over the recommended weight, but in for a penny, in for a pound decided to try the brick. Before Robert threw it off the hill we checked the controls surfaces and put on a few degrees of flap. Much to my amazement it flew straight and level but did struggle to make height, eventually after a few turns landing on the slope. The second flight was better but still struggled to make height particularly on the turns, its 2.165kg weight was showing. It should be easier to fly with a more stable lift, Great Orme beacons or at least a true SW wind at Burton Dassett. In the meantime, build Mk2.