Scale Soaring UK

Whilst browsing (on SSUK main site) for a suitable subject to build next, I spotted this design. I have never seen one built and it looks like an interesting subject.

There were a small number of GAL56 variants - all experimental and the programme was cancelled after the first prototype crashed in 1948 killing one of the two pilots, the other bailed out when the glider inadvertently ended up upside down following a stall test that caused both pilots to black out.

With that background, what could possibly go wrong...

I have chosen to build the 3rd variant, GAL56-03 which in my opinion is the least ugly. It also has a reasonable sweepback which should make it fairly stable.

It doesn't have the nicest side profile though - looking rather utilitarian


I did find a paper on the internet discussing the series of designs. Conveniently, a wing section was included in the document which was duly scanned and used as the basis for the design


I have slimmed it to 14% thickness and with the model scaled at just less that 1/5, gives a root wing section depth of about 100mm! The wingspan is just under 3m so not a bad size. Spars look absolutely tiny at the root. I am opting for about 3 degrees progressive washout.

I am still at the thinking stage. I have done the fus design (early pass) in DevFus but it needs a bit more work.The wing is in Profili Pro but still needs tweaking - for example, I need to add the flaps.

The model will not be exact scale, for example, the prototype had LE slats at the wing tips (about 30% span) which I wont bother with but I will probably add the flaps...

The undercarriage will be detachable so that I can fly it on a slope without risking ripping the wing apart.

Your thoughts please?

Martyn

Martyn, would love to see you make this! I happen to notice that Eric 'Winkle' Brown described it as 'the most difficult plane he had ever flown' - which really is saying something. There is an amazing description of it in his book 'Wings on my sleeve'. I look forward to you taming it in model form!

Thanks Nigel

I am going for the 'Maximum V' variant, TS-513 as shown in this photo...

The fus is at this stage at the moment. It would probably be quite nice if it was moulded




and with the skin stripped off


As you can see, it still needs a little more work

Martyn

This looks like a very interesting subject! Great to see someone doing something different.

The pilot who died was Robert Kronfeld who was a high achieving Glider Pilot and the pilot of such Gliders as the gigantic Austria built by Kupper. He was an Austrian Jew, who left Germany before the war due to the way he was being treated and settled in England to become a respected Glider test pilot.

Thanks for that Vince and also thanks for uploading that very interesting PDF

One thing I have spotted from the photo of TS513 that you uploaded is that the elevons appear much narrower than those shown on the artists impression. The fuselage is much more angular as well. Very, very helpful

Martyn

A bit more progress on the CAD work. A bit slow because of the Corvid problem but moving along slowly.

The Fus design is just about complete


This was conceived using DevFus than migrated to AutoCAD to produce a working plan


Its not quite 100% right at the moment but not a million miles out either. Certainly near enough to build from. The formers are built around 2 horizontal plates. The bottom section - below the glazing line will be skinned in 3mm balsa, the bit above will be open.

Its not carrying any load so I can keep it fairly light.

The wing was drawn up in Profilli Pro and then imported into AutoCAD. Again. its not quite 100% there, I am still puzzling on the flap hinges and making the undercarriage easily removable but I'll sort something out.


The aileron rib spacing isn't quite right either but I guess no-one will ever notice. Wing span is just a tad under 3m with the root Chord at 755mm with a wing root thickness of about 98mm.

Wing skinned in 1.5mm balsa. Probably quite a lot of it...

Wing spars are multiples of 1/2 x 1/4 spruce diminishing outwards from the root.

All ribs and formers are 3mm liteply, the fus longerons are 1/4 square balsa.

1" diameter ali tube wing joiner. That should be OK and I have a suitable tube in the shed.

Any thoughts or worries, please shout.

Next job is to prep the laser cutting files and get the wood cut up

Thanks

Martyn

Morning Martyn,stuck at home self isolating (is that legal).I built a 1/3rd scale Choucas,a French powered flying wing,with a slight swept forward sweep.I used the scale wing section.It flew wonderfully with about 20 degrees of up elevator for level flight.A friend built a Marske Pioneer again a slight forward sweep,he used the full size wing section,again a large amount of up required to keep it level.An American modeller also built a model of the Pioneer,same result,so he contacted the designer of the full size one ,the reply 'cannot understand that,you do have in flight adjustment of the Cof G in your models,don't you '.I am wondering that maybe we need more reflex on our smaller and less efficient wings.It maybe that as your subject has a large amount of sweep back,the elevators are further from the Cof G therefore less movement required.

Thanks Barrie

There isn't a great deal of reflex but the elevons are absolutely huge. I expect that I will have to crank in a few degrees up for flying but because the wing is so prominent against the fuselage, I don't want to add any more reflex as it would be quite noticeable. I can live with a trim that will be invisible from the ground

There is a lot of sweep-back anyway, this will provide a certain amount of compensation for the lack of a conventional tailplane, it will turn easier and should be quite spirally insensitive.

TBH, I am more worried about what will happen when the split flaps go down - they are huge as well, more like spoilers on the bottom of the wing which will give a pitch down effect

Are you going to produce a workable plan Martyn?

Hi Cliff

Depends on the definition of 'workable'. I tend to build from my plans then add bits of detail as I go along (usually because what I draw in 2D wont work in 3D or I have totally forgotten something or something just doesn't fit. At the moment, I am plotting the rudder, elevon and flap linkages, trying to make them all invisible. In some respects, I am lucky because I don't know how it was done on the full size so I can be creative...
Once I get the linkages sorted, I'll 'dismantle' the drawing so it fits on 33" wide paper used on the plotter I used at the print shop.