Footlaunchable Ultralight Sailplane

At the moment, this page is under construction and in time I will add more descriprions, drawings, 3D renderings and photos....


If you read "about me", you can see that I flew all sorts of flying crafts in my past, and allso design and fly some of my own. I gathered all sorts of skills, both designing, building and flying.

That is a base on which a dream of Footlaunchable Ultralight Sailplane arise.

 There was many different versions in my mind, but all of them evolve in that final configuration:

  • footlaunchable
  • it can be folded down for transport
  • very simple design
  • no ambitions for extreme performance - just having fun in the air
  • aerodynamic control
  • common materials and manufacturing methods
  • great safety over the entire flight envelope


Layout of the sailplane.

Some data:

Wingspan:11 m

Wing area: 12 m2

Length: 5,2 m

Empty mass: ~35 kg

Load: +4/-2

CL max 2,2



Basic materiasl used:

  • Composite laminates (D box, spars, tail boom, cockpit cage)
  • Aluminum profiles and plates (control system)
  • Dacron sailcloth (covering of surfaces)

It is made from a carbon fabric&epoxy resin, molded between mylar sheets and clamped in the styrofoam male/female mold.

It is made inside a simple wood&aluminum angles "mold". It consists from a shear web made from extruded styrofoam plate laminated with glass fabric, and carbon extruded profiles as a spar caps. At points where hardware will be mounted, some plywood inserts are epoxied instead of foam, to create necessarry hardpoints.

It is made as mooldles sandwich construction. Carbon fabric laminated over an extruded styrofoam core. Cross section of the spar is shaped so, that a slot is created between wing and flaps to achieve high lif when flaps deployed.

Diagonal spar is made from aluuminum alloy thin walled tube and introduce horizontal loads from the spar to the rear wing/fuselage attachment.Llater, if weight should be minimized, it can be substituted with a carbon tube.

Some estruded styrofoam ribbs will support the shape of the D-box skin, but at both end, D-box will accept strong carbon ribs. rest of the wing will have no ribs.

As wing will have no ribs, the wing skin (dacron) will be tensioned between D-box and rear spar by means of four strong compression struts. They are made as moldles styrofoam/carbon sandwich. At each end of those struts, hinges are installed. Struts are hinged to shear web and rear spar in order that complete wing can colapse to reduce its size for storage and transportation.


They are made like a simple sandwich construction. Styrofoam and carbon fabric, with lightening holes, covered with light fabric Oratex-UL. Diagonal wires serve to strenghten rigidity of the structure.



EDIT (jan 2010):

I change my mind about Ailerons and flaps structure. Probably will be tube leading edge and diagonal placed ribs. Trailing edge carbon. Non foldable, but deatachable from rear wing spar.

Hardware (brackets, hinges, connections..) are cut from aluminum profile and plates. Some of the hardware is just standard aircraft grade (quick pins, bolts, eyebolts..)

It is a simple sheet of Dacron fabric , cut and sewn to proper size and shape. It is attached to the wing structure by means of lacing, screws and velcro ribbons. It is removable for easy assembl and inspections. The attachment points are locally reinforced by multiple plies of fabric and textile ribbons. Eyelets are inserted at screw locations.

Flaps are acutated by push-pull rods at their root. Rods are connected to flaps by quick release heads. Aileronsdrive is mixed type; steel wires, and pushrod.

Wing can be transported fully assembled with flaps and ailerons just folded 180° lowering the chord by one third.

But they can be allso colapsed into a smaller size and put into fabric bags. There are four bags: left wing, right wing, left controll surfaces, right controll surfaces. Bags are unpholstered at cruical areas in order to prevent damage during storage, loading/unloading and transportation. Bahs areequipped withzippers and textile handles.


Basic elements:Styrofoam profiled nose, Aluminum tube as spar, Foldable root ribs with tensioning clips, Aluminum battens and some brackets.

Nose, spar, brackets and root ribs are permanently connected. Sail from Dacron fabric is screwed to the spar and root rib. Wing tip is a Dacron/mylar sandwich attached to sail with velcro. Battens are removable.

 They are of "full flying" type and colapsable for easy transport and storage. The main structural element is a tubular spar. It is aluminum thin wall tubing (possible replaced with carbon tube if weight will be an issue). In front of that spar there is a nose cut from styrofoam, glued to spar and covered with heat shrink plastic. The sail is made from dacron fabric, cut and sewn to proper size and shape. The sail is attached to the spar with small screws and pop rivets. The tension of the sail is assured by two battens(hang Glider style battens) that are inserted inside the sail. At root of the tail feather, there is a colapsable root "rib" that hold lengthvise tension on the sail and allso provide torsional rigidity of the whole tructure. The root rib is tensioned by a diagonal strup, that can be easy to install and secure. The main connection to the fuselage is made different on the horizontal and vertical tail. Horizontal tail has two hinges attached to the spar, and vertical tail has a sleeve conection on the first quarter from botom and a pin connection at its bottom. The controll system consists from steel wiresm tnat are attached to the control horns by means of hook clips and small carabiners, They are marked by different color, orientation and lengths, so false connections is avoided or impossible.
Both tail feathers are deatachable from the boom for transportation, and they can be caried assembled or they can be colapsed andinserted into fabric bags (again unpolsthered and equipped with zippers and handles)
Sail is tensioned by root rib and battens. Battens are Hang Glider style.


Fuselage consists from three main structural parts: BOOM, PYLON and CAGE
Basic fuselage structure. Details omited for clarity.

Boom is a hollow carbon tube with increasing wall thicknes (in steps) toward its root. It is made on the simple plastic tube, used as a mold. It is of 110mm inside diameter and 2800 mm long. No stingers and formers, just some local reinforcments (carbon wrapped around to create a sleeve reinforecment). At rear of the boom a fin is created. At lower side it will accept a sprung rod that will act as a tail ski, at upper side, the elevator hinge is placed, and at its rear end the rudder is attached.

Pylon is an element, that is connected to the tail boom and acept wing at its top end. It is a moldless construction, made from styrofoam/carbon sandwich.

Cage is made on flat surface from extruded styrofoam, covered with carbon/kevlar fabric and UNI ribbons for the strength.At points where some hardware will be installed, the metal, wood and carbon hardpoints are created below the laminated skin. The cage will be connected permanently to the tail boom and pylon assembly.

In order to lower the fuselage drag, the cage can be streamlined by additional streamlining, made from a fabric/foam/fabric sewn sandwich skin. It is attached to the cage by means of screws and velcro tapes. As it is build as sandwich skin, it holds its shape well, but can accept rough handling without damages. At its lower side a opening is made for the pilot legs and body ("bomb bay doors"), for ease of starting. The opening is closed in flight by means of zipper velcroed to the fairing "doors.

The fuselage is equipped with two lansing skids and one main wheel. The skids made from composite lamiane are placed at front and rear end of the fuselage. The landing wheel is placed a bit aft from the CG in order to prevent bouncing up on the air at landing. The landing wheel is retractable and released before the landing. It is locked in retracted position by simple locking device and tensioned into landing position by means of weight and rubber chord. It lock itself automaticly in lowered position for the landing.

They are streamlined and made from off shelve Hang Glider A frame uprights tubing. If weight will be an issue, a plain aluminum or even carbon tubing can be used, streamlined with styrofoam inserts and covered with plastic film.


Pilot is wearing a harness very similar to early para Gliding harnesess. near left and right hipy a carabiners are placed. Pilot, wearing that harness clip itself by means of that two carabiners inside the cocklpit cage at proper hang point. There are couple hang points in line, so pilot hang itself at proper hangpoint according to its weight. That way the proper C.G. location is obtained. Lughter pilots choose forward locations, and heavier pilots hang itself on rearward locations. After take of, pilot put his legs onto the ruder pedals. Then he pull a rope and slide a hammock style seat under his back to allow comfortable ride. At the same time, the "bay doors" are closed as rope will pull on the zipper.


They are allmost conventional type. Rudder pedals and control yoke. But the controll yoke is placed at right side of the cage. It controlls roll and pitch.

At oposite side of the cage, a similar yoke is installed, but it serves as a flap and rudder control. Moving it sideways it controll the rudder. This is used at the start, when pilots legs are not yet resting on the rudder pedalls. It allows to controll the glider yaw at the starting phase. When this yoke is pulled back (sliding motion), the flaps are lowered.

Connection of the flight controlls to their controll surfaves are done by meand sof hard and soft elemens. They consists from steel wires, routed trough pulleys and nylon bushings, some brackets and levers and pushrods.

System is designed at disconnection points such way, that false connection is impossible in order to avoid ctastrophic behaviour results in flight.



Some renredings of the Sailplane....

Not detailed and colored yet, but they represent the glider form...

Main wheel in retracted position

Fabric cockpit enclosure omitted 

Flaps and ailerons in neutral position.




 To be continued.....


Scale model of this design

You can follow the building process of n 1:2,5 scale RC model of this Sailplane here (click).

Project update, yanuarry 2014

There are some significant changes in the project from previous post, and here I will explain tehm in detail.

The aweral layout and structure has been changed:



Tapered D-box and spar

No secondary wing spar, neather colapsable compresion struts.

10 foldable wing ribs at each wing half. Design adopted from Impact Rigid wing (by its designer permission)

Flaps and ailerons with torsion spar and foldable ribs. Design adopted from Impact Rigid wing (by its designer permission)



Tapered D-box and spar

Foldable ribs, similar to flaps and ailerons.

No external sail tensioning ropes, but internal tensioners for cleaner aerodynamics.



 So far no major changes.




 Picture above: wing drawings in progress.


 Picture above:  Closer look at wing plans.

 Picture above: Wing ribs workshop drawing.

 Picture above: ful scale plans.

 Picture above: wing sail tensioner sample for testing.


Picture above: tube cutter in use.


 Picture above: sample rib, No 5.


 Photo above: wing rib detail


 Photo above: carbon laminate D-box ribs and foldable aluminum ribs.


 Photo above: airfoil comparision


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