Sunday, 19 December 2010

The rig on the Baby Wingwalker Stearmans

The rig that supports the wingwalkers is quite a complex piece of engineering and has very accurate detail.

The main vertical tube is made from stainless steel tube and is custom made because nothing suitable could be found.  It was made from 20mm tube and flattened it into an aerofoil section.  Aluminium blocks were machined down to make the anchor points for the pivot. The seat is made from 5mm stainless steel round tube which is silver soldered together.

The cushioning on the full size rig is made from plumber's foam tube.  On the models it is made from the foam from hair curlers.  Orange electrical insulation tape (found by chance on the internet) simulates the orange gaffer tape on the full size rig.

The aluminium pulley wheel was machined.  The cables used to rotate the rig go over the pulley wheel to a sail winch servo with a 2:1 ratio.

The 5 point adjustable harness holds the wingwalkers to the rig.  It is an exact copy of the full size one because it is the most effective way of holding the wingwalker (human or model) securely. There are 9 buckles on each harness and each is hand made.  So too is the clasp that holds the harness together.

The rig is turned using a Supertech winch servo. It was important to have the smallest possible servo because it is visible.

It takes a couple of minutes to put the rig onto the aircraft frame.  3 bolts hold it to the wing and 4 rigging wires stop it moving in all directions.

Theres is a battery in the centre section of aricraft wing that powers both the rig and wingwalker.

The receiver for both the rig and the wingwalker is in the wingwalker's body.  2 cables run up inside the rig to take power to the rig and wingwalker. 

After checking the battery usage we have found that the rig/wingwalker batter uses as much power during a flight as the one that powers the rest of the plane.  There is a high load put on the servos as the rig moves and the wingwalkers move their arms and legs.

Monday, 6 December 2010

Landing the 30% scale Baby Wingwalker Stearmans

At the end of the flight you have to be on your toes with the Stearmans.  This is because the model wingwalkers are are full of radio gear and weigh more of a proportion of the overall weight of the aircraft than the slender full size wingwalkers!

Because of this you need to be landing into wind or as near to into wind as you can get. There are two ways to land the aircraft.  

One is to settle into a gentle three point landing when there is little or no wind to speak of. This type of landing looks really good on grass strips and you can afford to be a bit out of wind.  The wheels slip more than they do on tarmac and you are much less likely to ground loop. 

The second way is to fly them in faster and land only on the main wheels and use crossed rudder and ailerons to correct any direction changes as you slow down. This is the type of landing that Steve favours in stronger crosswinds especially when flying from tarmac.