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. 

  

Crofter first flights

Evening hardly any wind, on the day I maidened the CROFTER 24" simple glider. I found it very hard to trim. Took me a long time to get it to tow on the High Start (30m), and the glide starts stally, then tends towards a spiral dive. 

I think the fin is too big, and have since cut it down. I've also experimented with moving CG forward to 40% (it was about 50% on the plan), but it didn't help very much. I may try to move CG backwards to about 55% and see if that helps. 

However, I now believe that this glider for a newbie would not be as satisfying to build and fly as compared with a simple well-designed model with tissue covered wing. 

So, to check that, my daughter has agreed to build a West Wings Merlin 35" wing span, which is a well regarded kit. We'll compare it with this one for ease of launching and trimming - and overall satisfaction. Not really a fair test though, because it has a bigger span and more complex construction.

But I also have a 24" wing that was built a few years ago by my son for a school competition. It's based on John Barker's famous LULU. Here it is after steaming, banded to a board to get a warp out:

I should be able to to fix this wing temporarily onto the CROFTER fuselage. It weighs 8.43g as compared with the CROFTER'S which is 12.3g - that's 30% lighter! It also has significantly more wing area (90mm chord vs. 75mm on the CROFTER, giving about 20% more area if my maths is right). I'll balance it at about 50% and see how it behaves. It will be an interesting experiment!

Newcomers need something that gives good results relatively easily, in my view.

Gambler AG mods, beginners RC discus launched glider (DLG)

The Gambler AG is a great plane. Elsewhere on this blog is information about its construction. I've used the model a lot. On flat fields, its discus launch or off a bungee, but it's also fun to slope soar it. For towing, it needed a tow hook, so here's a picture of the one I made for it:

The tow hook is reinforced internally as shown here. Also, as I mentioned in previous posts, I got rid of the rudder pushrod. Here, through the foam guide, you can see the diamond hook of the new rudder control rod, where it attaches to the pull string of the return spring arrangement:

The elevator servo has stayed firmly placed over time, simply being glued down. I guess that loads on the rudder servo are greater, because in contrast, the rudder servo tended to move. I've also had to replace it twice. Fed up with trying to re-stick replacement rudder servos, I decided to make a mount for it, and this is what it looks like:

The servo screws are tightened using a cranked star screwdriver (which is a flash way of describing "one wot I bent!"). The rudder servo mount has been a major improvement. Apart from making it easier to replace servos, it has also improved rudder control finesse and centering. Will it stay put over the long term? Time will tell...