Mac McGarrigle's Lifting Body
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Reusable Lifting Body Vehicle II (RLBV II)

The Reusable Lifting Body Vehicle II (RLBV II) is my next generation of radio controlled/auto-piloted lifting body model rockets.  It is based on the HL-10 NASA design that was built to evaluate an "inverted airfoil" and delta platform lifting body shape.    

For the RLBV II the aerofoil was designed using CompuFoil, aerofoil design software.  This version of the RLBV will be made from a foam construction.  CompuFoil documents the aerofoil shape and the printouts were used to create 'hot wire' templates.    This allows for better precision and repeatability of designs.

This is the front view of the RLBV II model.  This will change as I am considering making the upper body a little more rounded than shown in this CAD drawing.  I am happy with the lower body shape.  I will replace this drawing with a photo of the final design after some flight tests.   

Cutting the Foam Body   Click on Photo...
 As you can see this is basically a box (24" x 12" x 8") made from Medium Density Fiberboard (MDF) with the shape of the aerofoil section cut into the sides.  The template is protected by laminate strips stuck to the edge to stop the hot-wire burning through the wood.   

The hot-wire bow is powered by a 110/24 volt - 5 Amp transformer.  To achieve the correct cutting temperature the current to the wire is regulated by a light dimmer control (shown on top of the cutting box).

The Foam Body   Click on Photo...
This is the result after the foam blank is cut back to the required basic shape.  This is just the first step and great care is needed to get it into the correct lifting body 'flight efficient' shape.

The lines drawn on the foam blank are guidelines to help during sanding.  The body tube and the balsa trailing edge are already fitted.  The nosecone is removable to carry the sensors and battery pack for the Basic Stamp autopilot.

The Winglets and Fin   Click on Photo...
The winglets and the fin are made from 3/32" balsa sheeting covered with construction paper on both sides.  I glue the paper onto the balsa with a white glue stick, then place the resulting laminate under a flat piece of wood, and weigh it down while it dies overnight.  I then run a small smear of wood glue along the edge to seal and strengthen the edges.  The end result is a very flat, straight, strong, and paintable control surface.  I have made the control surfaces the same way.

Lifting Body Assembly   Click on Photo...
This is the starting point of the assembly of the lifting body itself.  Wings and fins are glued on using wood glue.  The control surfaces are fitted with plastic hinges and glued into the rear trailing edge.  I am really pleased with the shape produced using this method.  However, I am concerned with the weight as it is weighing in up to 25% of prior models and I still have not fitted the electronics.

Notice the shape of the elevons.  They are similar to the proposed X-33 with large flaps on the outside.  The control surfaces then tapper as they approach the center of the lifting body.  This is so that the airflows quicker across the center of the airframe thus creating even more lift.

The control surfaces will be brought to a vertical position parallel to the body tube during boost.  The large flaps on the outside of the control surface act as another pair of fins during boost.  This greatly helps boost stabilization.  The motor mount will also have fins mounted to it.  Once the motor mount ejects it will carry the booster fins with it along with the spent motor.  This will greatly reduce the weight and improve glide performance. 

Here you can also see the servos I am going to use for the control surfaces.  As you can see the control surfaces are mounted outboard and the lifting body itself narrows to the trailing edge.  This is to minimize 'base drag' that is a killer of lifting body aerodynamic performance.

More to come...