Quorneng's build blog

Pol
I my defence it only weighs 3.5oz, flies at about 5mph and was in a wind close to its flying speed. Not really suitable weather for a maiden!

In addition the prop was wind milling as it glided in and even with a prop saver as soon as the blade touches the ground it almost stops the plane dead whilst its still flying.

Not so much a "spear in" more an "arrested" landing.

Well that's my excuse!

And just to continue the other build thread the Hamilcar is now complete - again!

It weighs 32.3oz with 2200mAh 3s. A wing loading of 7.5oz/sqft and has a good 120W/lb.
But until I have somewhere to fly it and the weather - it stays hanging on the wall!

The first ruduction in the Wren's fin & rudder area.
From this (as in the video)

To this

A reduction of close to 30%.
With a further 20% taken off it will have about the same area as the twin fins.

Quorneng wrote: Pol
I my defence it only weighs 3.5oz, flies at about 5mph and was in a wind close to its flying speed. Not really suitable weather for a maiden!

Well that would explain a few things ... A bit of Garry's flatulence would have that doing unintentional aerobatics.

A quick up date on the Wren.
As I hoped it flies just as well with the reduced fin and rudder, in fact in term of handling characteristics its rather better.
Still glides like a brick with the wind milling prop. Unfortunately the 10A ESC does not appear to be programmable.
So the fin and rudder are reduced some more.

Mostly from the rudder this time.
The remaining area is now quite close to the 'tall' twin fins I had on earlier so if this 'small' single fin is ok I will refit them but at least initially I might leave a small fixed centre fin - a la the Manchester!

Just managed to get a flight in yesterday afternoon as it was quite calm in the light drizzle!
It flies very nicely with the second fin reduction so the twin fins are back with a small central fin which can easily be removed if it proves unnecessary.

The only issue is the ESC (Hobby King 10A) as it does not appear to be programmable from the Tx so I cannot set the brake. The prop thus windmills and it glides like a brick but under power it has quite an impressive climb.

There is a spare Tx channel so the altimeter can go in.

A video of two 'twin rudders' Wren flights today. First with the central fin, second without.

So far so good.

Pol
Are the landings any better?

So how did it compare- with or without the central fin?

Looks wicked Simon

Removing the central fin did make a significant difference.

It is noticeably more 'wobbly' in the second flight. It was much more easily upset by even the smallest bit of turbulence and I did not feel confident to fly it as low as I did with the fin in place.

If and when I get a suitable folding prop (and the weather gets a bit warmer!) I will try to find out what it really can do.

Yeah saw that but wasnt sure if it was the wind or you wobblying Looks good though

At 4pm this afternoon the wind died down to about 5mph and it was relatively warm (8 degrees!) so an endurance flight with the 'tall fin' Wren.

It flew for 39 minutes and it was not at the LVC - but probably quite close to it.

From its 500mAh 2s that's an average of 0.75A which is 6W. Sounds quite good but at it only weighs 3.25oz it actually 30W/lb.
This rather shows how inefficient these small planes are as my 48" span Endurance also flies on 6W and it weighs nearly 4 times as much.

I would like to get it to fly for 1 hour.

Quorneng wrote: At 4pm this afternoon the wind died down to about 5mph and it was relatively warm (8 degrees!) so an endurance flight with the 'tall fin' Wren.

It flew for 39 minutes and it was not at the LVC - but probably quite close to it.

From its 500mAh 2s that's an average of 0.75A which is 6W. Sounds quite good but at it only weighs 3.25oz it actually 30W/lb.
This rather shows how inefficient these small planes are as my 48" span Endurance also flies on 6W and it weighs nearly 4 times as much.

I would like to get it to fly for 1 hour.

Heh, don't knock it mate, you're experimenting & that is the basis of how flight for man started in the first place .... someone has to try these things & record the data..... You keep going & leave the rest of us idiots to cock it all up!

Even better weather this motning - sunshine too - so a maximum duration with the altimeter on board.

Launch to landing - 47 minutes 30 seconds. The biginning and end of the trace cover the walk to and from the car. That's a 5W average.
It might look like I was using a climb and glide technique but with such a squashed time scale is was actually just the difference in power of one click on the throttle stick! The power was on all the time.

I would like to get it to fly for 1 hour. It currently uses a thin flat bottomed section so I might try a trace of under camber (the original had some) to reduce the flying speed and thus the drag from the rest of the airframe but at such low Reynolds numbers its anybodies guess as to what actually works best!

Using undercamber may help if you can grab a few thermals, but remember one basic rule .... the more you twist & bend any aerofoil section, the more drag you create ..... the best streamlined section is a flat sheet.

Pol.

47 minutes 30 seconds with power on constantly? Bloomin eck Simon, you got it plugged in on a long lead at Manchester airport?!?! What batteries are you using?
315foot in 12 mins? Remind me whats the fastest/furthest climb again (dont like logging into t'other place to see)

willowlea wrote: 47 minutes 30 seconds with power on constantly? Bloomin eck Simon, you got it plugged in on a long lead at Manchester airport?!?! What batteries are you using?
315foot in 12 mins? Remind me whats the fastest/furthest climb again (dont like logging into t'other place to see)

You don't want to know the fastest climb ..... we used to have competitions where you had 30 seconds of engine power to climb as high as you could .... then you had to glide for as long as possible.
Most models were out of sight vertically in less than 15 seconds so we had to change the rules a bit.
What's that regulation about the maximum height we can fly at?