Friday, September 4, 2020

Flying a small glider off a High Start: Lulu wing on Crofter

The Peterborough Model Flying Club specify a high start for small gliders as 7.5m of rubber (they recommend 1/8" strip) attached to 22.5m of line. This works beautifully. Here are some details of mine. First, this is how I store it, on a 1cm thick Depron foam board stiffened with a piece of wood (a bit of old fencing!):

This works very well. Simply remove the split ring from the knob of Depron, fix it to the ground with a decent stake, and unwind the foam board as you walk back downwind. To put it away, start by putting the glider end split ring onto a Depron knob, then wind it up as you walk forward to the stake, making sure that the rubber goes on slack. Use a hand over hand movement, otherwise the line will twist.  Knots wise, I use a Palomar knot to tie the rubber to the stake ring, a Figure 8 (Flemish) bend to join rubber to line, and an Anchor Hitch to join the line to the ring at the glider end. I also add half hitches and overhand knots on top of these to prevent slippage. If the kite line at the Figure 8 bend cuts into the rubber, then I'll do something else, but so far, it's held up well.  

Following on from posts about the CROFTER, I had a 24" wing that was made by my son for a school project. It's based on the LULU wing, scaled down.  Here it is attached to the CROFTER fuselage:

If you look carefully, you can see that all I've done is add a couple of 1/16" tabs in front and behind the wing platform, before banding the wing on. It means that the band pegs are a bit awkward to reach, but it's not a big deal. 

No idea why my son went for a German/Belgian flag look with the tissue! 

Balanced at 49% of chord (90mm, so at 44mm behind the leading edge), all up flying weight was 36.7g. That means it's about 10% lighter than the CROFTER with roughly 20% more wing area. Wing loading hugely improved. 

A quick shoulder glide, showed it needed a 1/32" shim of up on the stab, and it had a slight right turn which I encouraged with an Al foil tape trim tab on the fin. Then on to the high start. First flight was over 1min. I had a go at trying to take videos myself, but it was pretty lousy trying to do it myself and launch. First a 4s clip of the end of the high start launch. 

Now a longer video of part of one of today's flights. It starts off doing right hand turns, but then goes downwind in a straightish glide before turning a little and landing. 

It's abundantly clear that the LULU wing on the CROFTER fuselage is far better than the original CROFTER wing. A tribute to John Barker, who originally designed the LULU. RIP Hepcat. 


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