get the air flow, but once it’s up in the wind the

breeze is supplying the air flow that makes it

fly. If you’ve ever watched a war movie where

there’s an aircraft carrier involved, you’ll know

they turn the ship into the wind so that the

planes taking off have air flow from the wind

passing over their wings as well as thrust from

their engines, helping their wings to generate

lift by the time they reach the end of the deck –

otherwise they would get very wet.

In the wind tunnel we set up the bike attached
to the HPA frame only – no wings or tail, just
the propeller on its tail boom mounting. I did
the pedalling to get the propeller spinning at
speed and the wind tunnel provided the air
flow. We hit a couple of problems, the first one
when the chain came off, something that every
cyclist has to deal with at some time or other –
usually in the dark when it’s pouring with rain
and you’re miles from home. We needed to get
the tension on the chain exactly right. Too tight
and it might snap, too loose and it would be
wasting energy and likely to pop off.

The next setback taught us a proper lesson.

I heard an almighty whack from behind me as

I was pedalling and then everyone yelling at

me to stop. It turned out that the propeller had

hit the rear of the cockpit frame. It seems that

it was flexing too much at low speed. At higher

speed it would be fine, but as we were building

up speed it had bent a bit, smacked the back of

the frame and one of the blades was broken.

Knowing how much effort we had put in to

make the blades, I was gutted, but Alex and

Ben were quite philosophical about it. For Ben,

this was a ‘bleeding knees’ lesson, and Alex’s

attitude was simply that it was better for this

to happen now than for it to happen when we

were out trying to fly our HPA. A crashed HPA

can take a lot of repairing, as I knew from the

length of time it had taken to make just one

wing section.

We decided to use the ‘reject’ blades to make

a stiffer propeller. We needed the quickest

solution because time was no longer on our

side. We were now working to a deadline,

with only a month to get our HPA in flying

condition for an event known as the

Icarus Cup.

BUILDING A RECORD BREAKER   113