DLG Plan: Part 4, Wing breaks and fuselage

Photo left is just a reminder of where I had reached at the end of Part 3 in this build. The wing high point is just visible as a dotted line and both wing and fin have denser wood LE reinforcement.











After cutting at the breaks and sanding, the photo right shows what the aerofoil looked like. The walnut LE shows up nicely. The TE is thicker than I would normally finish a HLG. However, I'm nervous about strength and kept the TE at just over 1mm thick to provide some surface area for the glue and to preserve some rigidity in the wing. Quite close to AG03.

Photo left is the wing drying. Glue is Araldite Precision slow setting epoxy. It's all standard HLG building so far. 109 mm under each tip (the convenient height of a tomato tin!) .

While the wing was setting, I glassed up some 1/32" (0.8mm) marine ply using medium glass cloth and two part epoxy. This will make the wing break reinforcing braces - it's cunningly sized to fit exactly within a tenon saw cut. I may also use it for the boom hinge plates (or 1/64 ply - haven't decided yet). Poly bag below and above, then weighted down with books overnight while it set. This is the first non-standard HLG bit.




A closeup of what the glassed ply looked like when dry. Probably too much resin this time. However, job done and it's much stronger and not significantly heavier than without the glass fibre.












Also while the wing was setting, I cut out the fuselage parts. Very simple: 6mm square spruce, a carefully selected coffee stirrer (thanks Starbucks!), and 1/4" (6mm) balsa 18mm wide. Glue these together with PVA and rubber bands, with the spruce butting against the coffee stirrer.



Then apply 1/32" (0.8mm) ply cheeks to reinforce the central part. This was standard marine ply, not the glassed stuff. Again, glue with PVA. The ply cheeks also act as the locator for the carbon fibre boom.










After cleaning up the glassed ply, and sawing the wing along the high point line from the underside with a tenon saw, test fit the glassed ply wing break reinforcer. Mark with a pen above and below the wing and trim.













Cut off the excess and lightly sand up the glassed ply brace. This is what it looks like - a sort of chevron. When happy, I glued it in place with Araldite Precision .













This is what the underside looks like after the glassed ply brace has been glued into the saw cut.


I hope it's strong. So far, this is easy and relaxing building. But will it fly, or is it destined to crash into the ground with a sickening crunch?....

DLG Plan: Part 3, More work on wings & feathers

For aerofoil section, I am trying to follow the AG03 by Mark Drela. He developed it for the Apogee RC hand launched glider. Unsurprisingly, it is remarkably like conventional HLG aerofoils. Walnut works well with plane and sandpaper - I would use it again.

The high point was marked with a fine felt tip pen dotted line. It is 28 mm from the front of the LE running parallel and then curving to the wingtip centre line. Use the wing tip template to draw it.

The sanded fully shaped wing weighs 40.8g. I've kept the TE at >1mm for strength.

The stab was given very little work. Just rounded off the LE and sanded the rearmost ~ 1" of the top in a taper to the TE (but not too thin, because I want to preserve some strength). A thin strip of bass wood was glued and rubber banded to the LE of the fin, wrapping it a little around the bottom edge.

Photo left is a close-up of the bass wood LE of the fin, after the bands had been removed and a bit of cleaning up with sandpaper.

Next, wing breaks, or shall I start the fuselage instead?

DLG Plan: Part 2, Cutting out the flying surfaces

At long last, I had a chance to put scalpel to balsa today and cut out the wing, stab and fin. Wing is from 1/4" (6 mm, ~ 6.5 lb/ft3), stab and fin from 1/16" (1.6 mm, ~ 8 lb/ft3). The first step was to print ellipses of the right size on to thick paper and cut them out to use as templates. In keeping with the design objectives, I will not be sanding the stab and fin to aerofoil sections, but will round the leading edges and lightly taper the trailing edges.

In the photo, hardwood strip has been glued to the leading edge of the wing with waterproof PVA. I use rubber bands and masking tape to clamp it while the glue sets. Normally, I would use spruce or bass wood for LE reinforcement, but this time I used walnut D strip simply because it was there and it was long enough - I used one piece for the whole LE. The walnut bends well using steam from a kettle and the dark colour makes a nice contrast to the balsa. Should be strong too.

Thanks Stevie B for the encouragement!

DLG Plan: Part 1, Design thoughts

"The time has come," the Walrus said, "to build a DLG:
Of wings - and fins - and carbon booms -

Of glass fibre - and pins -

And why the sky is bubbling -
And whether pigs have wings."

It is time for me to build such a pig. First question, shall I use an established plan or kit, like Spin Up, Round-A-Bout, Dynamo Hum, Turn Up, or other? Erm....No. Why? Because I wanna make my own! I enjoy designing. I cannot do better than the established designs. No, my objectives are different. I see this as a learning experience. I'm not going to ignore the exisiting designs. I'd like to create a free flight tip-launched glider that has the following attributes:

• Simple design
  
• Quick and easy to build
  
• Pleasant looking
  

So, ladies and gentlemen, I present to you LIPZOID, well, a back-of-an-envelope sketch of it.

DESIGN THOUGHTS

The original Monster DLG by Tetsuo Itoh in 2004 had 8 panel wings. Phew! At that time, it was the fashion in conventional "javelin" style launching HLGs to have multi panel polyhedral wings (5 or more panels). A few months ago, Tim Batiuk smashed the US HLG record with his 4 panel design, Turn Up. His plan is freely available at Kurt Krempetz' excellent AMA Glider website. If I was sensible, I'd make a Turn Up (er, affectionately, "Turnip"). It has a 4.5" root chord, four wing panels and is not my own design! Maybe later.

I have 4" wide 6mm balsa in stock and want to try to make a three panel free flight DLG. 4x36 worked on Dynamo Hum, Twirly Bird and the Monster was close to that size. Three panels works for the Gambler RC DLG. Most F3K designs are simple dihedral (though of course, they have aileron servos!). There is long history in 3 panel wings in Free Flight, such as the iconic, super-performing Keil Kraft Senator rubber model, many F1A glider designs and quite a few conventional HLGs. So why not a FF DLG in 4x36 three panel? The wing can be glued up in one session and the wing root fuselage joint is a simple butt joint (no need to sand a v in the fuselage). So time can be spent instead on that lovely glass fibre cloth stuff. Fewer joints means lighter weight too.

For a bit of style, and because capriciously, I'd like to call the model LIPZOID, I decided to utilise ellipses for all flying surface planforms. My excuse is that ellipse planforms have a long history in free flight, especially in HLGs. They are also easy to print on a pc! None of this fancy drawing package nonsense, no. I use old-fashioned PowerPoint. I'll use ply biscuit(s?) and GF cloth on wings, no CF tow. It must have bass wood or spruce on LEs (thread may be ok on the tail feathers). Fuselage from 6mm balsa reinforced with GF, spruce or bass and ply, aiming for light weight and simplicity. Probably a nylon bolt for the boom pivot. Button timer and probably 2 different thicknesses of fishing pole elastic to hold the boom yet create appropriate tension on the timer arm. No throwing peg - just sandpaper top and bottom - just like Mr Batiuk.

Will it fly? Who knows? But I'm gonna enjoy finding out!

Chuck Glider discus launches Gambler AG

This is not a free flight glider. I've been dabbling with the "dark side" and my chosen weapon is the Gambler AG from Wright Brothers RC.

Why am I dabbling in the dark side (aka radio control)? Well, there is method in Chuck Glider's madness. The main reason for playing with RC is to learn about discus launching - what it feels like and how bad launches go!

The latest thing in free flight chuck gliders is the discus method of launching, also called tip launching. This is a field of aeromodelling where free flighters have learned from our radio control cousins (not the other way round, as is usually the case ;) ).

The Gambler is a fine model and I've thoroughly enjoyed flinging it about to play with low level thermals. Best flight so far is nearly 3 minutes (in wintery conditions). I have not flown it in good thermic conditions yet and am looking forward to that!

The next stage would be to build a free flight DLG! So watch this space....

Polish Aircraft - Superb Scale Subjects

I've been a fan of Polish planes ever since I watched a full-size Ogar (SZD-45) taking off at an airfield. This is a motor glider designed in the 1970s and is simply hypnotic to watch. No wonder they issued a stamp picturing it (left).

After I had the fortune to fly in other Polish gliders, such as the SZD Junior and Puchacz, I was hooked. They were well made and handled superbly. The SZD-55 is to my mind one of the most beautiful gliders ever.

Now here is a fabulous Polish movie, probably from the early to mid 1960s. It seems to be about wave soaring in the mountains. You need to put the sound on, because the music (Moon River) adds to the effect. Watch out for the footage of an SZD-22 Mucha Standard glider, a model sailplane (at 3:50 minutes in), the Mucha Std being aerotowed by a Gawron (4:40 to 6:30) and the super streamlined SZD-24 Foka glider (8:25).



The Polish aviation industry has a track record of coming up with amazing, ground-breaking and eye-catching designs. PZL means "state aviation works" and no doubt, early on the industry was heavily state funded. After SOLIDARITY and the rise of capitalism, it seems that some of the aviation industry was bought by the European aviation giant EADS. I have never fully understood how the industry is structured and organised. Currently, there seem to be at least two glider manufacturers - PZL Swidnik (who make the PW5 and PW6) and SZD Allstar PZL Sp. z.o.o. (who have a long history in sailplane manufacture).

In the early 1930s, arguably the best fighter plane in the world was the PZL P.11 (photo right). It had these amazing parasol, gull wings. It is not difficult to see why it is a subject for scale modellers, though perhaps not common enough. At that time, the pace of aeroplane development especially in Germany, was very fast and the performance of the P.11 was soon surpassed.

The PZL 101 Gawron was designed in the late 1950s/early 1960s for agricultural and other civilian uses. (Photo left; the tug plane in the video above is one of these). I have not seen a free flight model of it, but it would make a fine subject with those wing tip plates and slightly swept back wings.



The PZL 104 Wilga (left and below) is a fairly common subject for RC models - both scale and semi-scale. With its slightly quirky but cute looks and short take off run, it would make a great rubber or electric free flight model. It makes a good glider tug, full-size and I suppose, as a model.

The PZL 130 Orlik (below) is a very small, ~10m span, 2 seater, highly versatile training plane. It is used by many air forces and the Polish Air Force display team.



The wing planform and the proportions are fabulous (see the three-view below). This would make a lovely model plane.

Unsurprisingly, Poland has produced some fine pilots and aeromodellers too.

Chuck Glider from one 1/16" balsa sheet: Part 5, FREE PLAN!

The final plan for PLAIN SAILOR is below. Right click to save it.

Flying the prototype revealed a weak point at the fin to fuselage joint. This is because the main strength at that point comes from one side of the fuselage, that is, 5mm of 1/16" balsa!

So, I cut the fuselage at the stab and trimmed the fin down, as it was too big. After re-attaching the tail feathers, the glider was much better behaved. I guess the moment arm of the prototype was too long. Compared to the prototype, the overall length (not including ballast) of Plain Sailor is 18".

Unfortunately, I do not have an indoor venue to fly in, but outdoors in the calm evening air I was getting flights of 25 to 30s. I'm sure that could be improved on with more work on the launch and transition trimming. However, this model was not designed purely for duration, but also for the other "tasks" that make up the one-sheet indoor competition, including longest glide and spot landings.

I used a small pea of blu tack on the left wing and a teeny bit of left rudder to get it flying conventional right - left. Take those trims off and it will go straight and level, since there is no stab tilt.

To make it suitable for outdoor, I would suggest gluing a thread on the LE with CA, increasing the dihedral to 2" under each tip and finishing it with 2 coats of sanding sealer with very fine sandpaper in between them. With its light wing loading it could easily fly away in thermal lift. Higher launches would require a decalage setting closer to 0-0, but as has been discussed before, that can introduce inconsistency in way the glider recovers at the top of the launch.

If you build this simple glider, please let me know how you get on.