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Glasfugel H201 Libelle

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Simon Chaddock20/11/2012 12:20:59
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Whilst waiting for the weather (or should that be the winter!) to attempt more endurance testing you naturally start thinking - what next?

I do like building to scale.

I do like building high performance light weight structures.

I now have 3 powered gliders in the 2m range.

 

I was always very impressed with the design of the Glasfugel H201 Libelle.

small-3view.jpg

Simple, elegant, light and as one of the first all glass fibre jobs it had a pretty good performance for a 15m glider. 100+mph and still be in a pretty flat glide certainly impressed me when I flew one!

On the full size you locked everything into place by doing up one tiny retaining bolt on the tailplane and pushing one pin into the wing.

Oh! and you had to connect the aileron push rods with two 'pip' pins but that was it.

 

At smaller sizes the problem is always the scale wing chord. At 2m span a Libelle wing root chord would be only 128mm (5" ) and just half that at the tip. Such small wing chords are simply not that efficient.

2.8m span gives a 180mm chord (7" ) which although still on the small side should give a significantly better glide performance and the bits would still easily fit in my car.

So next I need a new 1.5m building board. wink 2

Edited By Simon Chaddock on 20/11/2012 12:24:58

Tom Wright 220/11/2012 13:22:55
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Indeed a beautiful sailplane Simon , do you intend to build in balsa or depron ?

Tom.

Ady Hayward20/11/2012 13:28:47
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Hi Simon,

A very nice choice of glider. I was very impressed by the one I saw at RAF Bicester in the early 70's. The elliptical section rear fuselage caught my attention, as did the humped canopy, but it shows all the features were there for performance, as you say the performance was fantastic for the time. Alas I never got that far in the glider tables, only graduating to the K6 at the time. Halcyon days.

Adrian

Tom Wright 220/11/2012 13:48:42
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Ady.

That's a huge improvement on my few hours in a T21 lol. Went on to "spam cans" after that embarrassed .

Tom.

Edited By Tom Wright 2 on 20/11/2012 13:51:00

Simon Chaddock20/11/2012 14:13:24
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Ady

I only just got on to the Libelle. Only flew it as a 'guest' and it was my first retractable U/C so actually doing something for the 'U' in the landing check pneumonic USTALL was quite novel.

Tom

Never flew a K6 but did many hours in an Olympia 2 and my favourite the big Skylark 4 although compared to the Libelle it needed a couple of champion weight lifters to put it together!

I am tempted to use Depron (again!) - mainly because it would be by far my biggest and it is very cheap!

Martin Harris20/11/2012 14:59:20
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That's brought back a fond memory of a delightful little glider to fly (and look at). I also had the privilege of being invited to fly one and although they had a reputation for having fairly ineffective airbrakes (due to being set rather far back) I didn't notice any problem at Booker. Might have been different into a postage stamp sized field of course!

I've never been sure whether the owner thought I had a share in the beautiful Moswey 4 that my syndicate partner in the Rhonbussard owned and was hoping for a go in the "Rolls Royce" of gliders (the finish inside and out had to be seen to be believed) but he declined my offer of a flight in it when he saw how awkward it would be to get himself and his artificial leg into the 'bussard's rather cramped cockpit lurking under the leading edge of the wing!

P.S. Just did a quick Google translation of the link and it's the same Moswey that I flew all those years ago!

Edited By Martin Harris on 20/11/2012 15:17:24

Simon Chaddock20/11/2012 16:32:48
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In the 70s I did produce a few moulded resin 'table top' Libelles from my own moulds.

libelle1.jpg

They were packed de-rigged in foam lined boxes and went together (but just a push fit) in exactly the same way the full size.

Lots of hand work to finish them so in reality cost many times more to make than I sold them for!

Edited By Simon Chaddock on 20/11/2012 16:33:37

Radge20/11/2012 17:14:32
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Marvellous Simon! Can't wait to follow the build log. I've got a couple of hours logged in a Libelle mostly when not instructing at Bicester. Ineffective airbrakes I seem to remember but good penetration in the air. To be honest I only flew it when the Astir or Discus weren't available though, Typical, you don't appreciate it at the time, but it's a privelage to have it in your log book.

Simon Chaddock21/11/2012 13:23:06
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At 2.8m span these are the dimonsions of the scale root section.

Root Section

At 16.6% it is quite thick for model glider where 10% or even less would be more likely for a 7" chord.

I would like to built short left and right 'test' sections of the wing root to see if it is possible to duplicate the forked spar joint of the full size.

Simon Chaddock24/11/2012 23:54:34
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Joining a two piece wing always adds quite a bit of weight and complication particularly on a balsa/Depron structure where the whole objective is to keep the loads spread out as much as possible.

I decided to build a short root section of a one piece scale Libelle wing using the same broad balsa flanged box structure I used on the 2m wing.

1 piece test build

The box spar is skinned in 2mm Depron, the rest in 3mm

1 piece test top

The step created in the skin to accommodate the 1mm balsa flange to the box spar. In the proper wing the balsa flange would taper to zero at the tip. Here only a part of the balsa flange is in place.

1 piece flange

The centre section is flat with dihedral at each wing root.

1 piece dihedral

The section is scale (Wortman Fx66).

Scale Wortman Fx66

At 18% it is pretty thick for a model glider. Good for strength but it would have to be thinned out considerably (<10%) toward the tip for an acceptable glide performance.

It would be light, strong and easy to fit but would a one piece 2.8m wing be manageable?

Simon Chaddock25/11/2012 21:20:30
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Building the 'test' centre section has convinced me to go fo a one piece wing to achieve the best benefit from a lightweight Depron build.

However I fear 2.8m would be just too unweildy so it will be reduced to 2m (actually 2160mm).

The RH wing 'tile' printed to 1080mm

2m wing plan

At this size the wing chord is rather small (5" root, 2" tip) however I expect I will retain the thick scale section at the root for strength although it will be quickly 'thinned' along the span.

I suspect by sticking religously to scale it will become more of a builders model than a high performance glider so the air brakes may not be required.

Those tiny strip ailerons will be a challenge!

Radge25/11/2012 21:52:04
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Great stuff Simon! With such a thick section you could accomodate the 250mm aluminium servoless airbrakes as sold by HK if you thought they would be any use. But to honest I've been rather impressed with the effectiveness of mixing in spoilerons instead, similar result less weight and engineering I suppose. Sorry, just rambling to myself again, watching this build with great interest and very impressed.yes

Simon Chaddock27/11/2012 00:06:48
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Built the fuselage first. By far the most tedious bit, When complete I will have to complete the rest.

'Tile' printed to 896mm long and the 13 fuselage formers drawn in.

Fuselage Formers

They are the finished size so will have to be cut 3mm smaller all round to allow for the Depron skin.
It will be built as a hollow 'half' fuselage over the plan and then the other side added.

Hope I can avoid a 'banana'! wink 2

I can only guess at the finished weight but I will be dissapointed if it comes out over a 16oz.

Edited By Simon Chaddock on 27/11/2012 00:07:34

Simon Chaddock27/11/2012 16:06:33
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A start on the fuselage.

Fuselage former start

The outline is not really the keel but the first plank. The plank creating the top of the rear fuselage is strongly canted over to give the characterisitc 'edge' that runs down the rear fuselage to merge into the fin.

4 formers cut to shape, another 11 to go!

Tom Wright 227/11/2012 16:24:42
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Simon.

I have found that the wing section ,at the thickness ratio you are using performs very well indeed at low wing loadings .Achieving a model that will float and go places is not easy with this type of scale plan form ,but a really interesting challenge well worth the effort.

Progress so far looks encouraging ,keep up the good work .

Tom.

Terence Lynock27/11/2012 16:58:04
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I have MIke Smarts plans for the Libelle but not got around to doing anything with them as yet, cant remember the scale but over 100'' span as i recall, if your interested just google MIke Smart Designs,

Simon Chaddock28/11/2012 13:05:24
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This is about the point where you begin wonder if you have done the right thing!

With all the formers cut out (and the other half as well) the fuselage planking gets under way.

Fuselage planking

At this size the former radii are quite small so the planks have to be as well - max 6mm wide - so the process is very slow.

About the only advantage is that is is easy to follow the shape with such small flexible planks.

This is going to take some time! wink 2

Simon Chaddock28/11/2012 23:36:53
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The last of 22 planks goes in!

RH planking complete

This of course this is only half the 'bare' fuselage so after 2 days solid the Chuchillian phase comes to mind:

"...it is not the end or even the beginning of the end but it is perhaps the end of the beginning" wink 2

Simon Chaddock29/11/2012 16:59:57
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After leaving the fuselage weighted down over night for the glue to fully harden the other half of the nose formares were addded, followed by the cockpit lining.

Cockpit lining

This not only provides a suitable platform the battery & ESC but also adds considerble stiffness to the cockpit area.

The bare half fuselage weighs 20g (0.7oz) so hopefully around 50g complete.

Edited By Simon Chaddock on 29/11/2012 17:01:26

Radge29/11/2012 17:27:42
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322 forum posts
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Beautiful Simon!smile Will there be any longitudinal carbon strengthening required?

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