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Author Topic: Lilienthal glider  (Read 2946 times)
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Pete Fardell
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« on: September 28, 2013, 05:54:14 PM »

Right, am going to get this started. I'm building this partly for the scale glider comp at next year's indoor Nats and partly just because I've always liked the Lilienthal gliders. With a basic construction plan in my head I shall build it more or less over the three-view and work out any finer design problems as I go along. My intent is to tow launch with a pin, probably more or less in the integral pilot's backside (sorry Otto). His legs will be stretched out in front to give me a bit of nose length. This is the best of the drawings I've found on the internet. Unlike some of the others it shows front and side views and both underside and top plan views. By cutting the two chord-wise ribs carefully I hope to be able to set the under-cambered aerofoil by just fixing the other starburst ribs/spars over these.

Another thing I like about this particular drawing is that it has a fairly long tail-boom, giving me a more promising shape than some of the other versions. I found it on this Hungarian webpage: http://sry.atw.hu/cikk162.htm
First step is to enlarge the drawing and I could do with some advice on size. My inclination is to go about 24" span.
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Russ Lister
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« Reply #1 on: September 28, 2013, 06:38:19 PM »

I can imagine this giving rise to the odd tricky problem .... but I'm sure that you will crack it Pete.  Smiley
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hastf1b
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« Reply #2 on: September 29, 2013, 02:38:07 AM »


I found this. It may help you?

http://www.collectors-edition.com/lilienthal_edition_seeamodelgrow.htm


Heinz
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billdennis747
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« Reply #3 on: September 29, 2013, 02:50:09 AM »

Pete, how will you do the trailing edge?
Bill
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« Reply #4 on: September 29, 2013, 03:48:31 AM »

Hi Pete - nice choice, and I'm really looking forward to see how you tackle it.
A few of us over here (Oz) have been reading the indoor scale glider posts with interest and remembering when we tried something similar a few years back. We started with roughly Peanut Scale sized models - the version that allows any span as long as the fuse is only 9inch. They were actually meant to fly outdoors for when it was too windy to fly bigger, floatier aeroplanes in the small local park. And so we tried them indoors of course also. Both using a thin rubber bungee line.
I'll try to find some pics if you're interested.
Anyway - we thought we might have a go again after seeing the topic come up.
The thing that blew me away was that I just came back from the photocopy place with the blow-up of an early lightweight glider I was going to try out at our next meeting - and saw your Lilienthal post!
Looking forward to see your model take shape.
cheers
Tim

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Tim
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« Reply #5 on: September 29, 2013, 07:00:05 AM »

 Smiley
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Tim
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« Reply #6 on: September 29, 2013, 07:43:24 AM »

Looking forward to this one Pete  Smiley
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Pete Fardell
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« Reply #7 on: September 29, 2013, 09:49:03 AM »

Thanks for all the above, which is very helpful. Heinz, thanks- that page does look useful to me yes.
I've never seen that Betteridge glider before, Tim. Looks like a very good possibility too, especially if you did a similar trick to what I'm planning with Lilienthal and make the pilot's legs swung right forward.

Bill, I've not entirely decided on the trailing edge yet. Any advice? My initial plan is to just reinforce the raw tissue with a thin hem of paper and hope it holds up.
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billdennis747
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« Reply #8 on: September 29, 2013, 12:41:49 PM »

Pete
No, no tips really. I did the silk wrapped around a cord trick on a diesel model and it worked well, but silk is 11g sq m plus the dope. I've seen it done with tissue but it wrinkles. As you say, I would cut the scallops into the tissue and then reinforce it.
Bill
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« Reply #9 on: September 29, 2013, 12:43:19 PM »

I think the trailing edge was made of hemp string.

Heinz

Otto Lilienthal Museum http://www.lilienthal-museum.de/olma/ehome.htm
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Pete Fardell
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« Reply #10 on: September 29, 2013, 03:50:46 PM »

Thanks.
I'd already found that Lilienthal museum site. The photo collection on there is great, and made me realise just how many variations there are in his gliders. It's just a pity the photos aren't bigger but there seem to be quite a few original gliders and replicas in various museums which give me clearer photos to go on. That said, I'm not going to get too hung up on accuracy.

I've now enlarged the drawing in my first post to the size I'm going to build it. I printed it out on nine sheets of A4, carefully stuck them all together and then cut it up again into the different elevations to make it more convenient to work with.  I went a little smaller than first planned. It's going to be 22.5 inch span which, with such a broad wing, looks pretty big.
By happy chance, this month's 'Aeroplane' magazine has a nice little double page article on Lilienthal, just to get me in the mood even more. Funny how often that seems to happen.
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yagua
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« Reply #11 on: September 30, 2013, 10:41:18 AM »

Hello Pete!
Last year I did the model of the patent for static display for a birthday present. As soon as I find pics, I´ll send them to you.
The point of this reply is: THE tricky part is the oval ring, that is actually twisted.
The way I did it: once scaled the drawing (with photocopy), on the frontal view trace a line under the lower point of the ring (at the center). Then, meassure how much do the tips curl-up (about were all the "ribs" come togheter in the hinge).
Then took a piece of cardboard and glue a copy of the top view of the ring, cut it , and curl it up as measured. Just to make sure of it keeping the shape, I´ve added some lower "gussets" or reinforcement following the longer axis of the oval. Also put cyano glue all the way around the edge as a stifener.
All that is for the jig.
To buil the oval shape, as I was working with pine stripes (about 1/25 x 1/12 inch, or 1x2 mm), I sand them thinner, wet them, and slowly work around the jig for one complete turn. Leave "on" the jig with small adhesive tape stripes.
Then, add the second stripe around the first. And here is the trick I used: once the second stripe is about the shape, and still wet, I cyano-glued it to the first stripe. Cya will adhere them, even if they are wet  Grin.
Aloud it to dry for a couple of days, and then sand it to a round section (as I was working with flat stripes, the final section was square). Before you remove it from the jig, trace small lines or spots on it, to mark the correct place of the "hinges" for the ribs, and also for the central axis of the glider, so you can set the tail in the proper place (don´t ask me how I know..  :'( :'()
And VOILA´!! you have the twisted oval support!
Didn´t meant to higjack your thread. Just telling you the main problem I´ve found with this model  Undecided.

PS: mmmmm!!!! a flying model of this one....... another one in my "to do" list!!!  Roll Eyes Roll Eyes
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Pete Fardell
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« Reply #12 on: September 30, 2013, 12:26:17 PM »

Thank you- that will be really useful if my own method doesn't work! I had noticed that the ring is not flat. My own way, which I have just started on, is to bend thin wet balsa laminated strips round a flat almost circular jig. Then, once it's dry, I will soak it again and force the whole oval round a cylinder, such as a bottle, to get the warp in the hoop.
Thanks for the tip about marking the positions on the ring before taking it off the jig- I bet I'd have forgotten to do that!
I'd love to see pictures of yours if you can find them.
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« Reply #13 on: September 30, 2013, 12:34:19 PM »

I believe there was a discussion in one of the books put out by Bill Hannan about a CO2 powered version of this glider by Otto Kuhni that flew OOS.  He used the pilots body to hide the tank, and I think the pilot held the motor in his hands.
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Pete Fardell
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« Reply #14 on: September 30, 2013, 12:37:11 PM »

You're right. I've got that Hannan book. The aircraft has the legend 'Brown meets Lilienthal' on the fin. A very nice model indeed!
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« Reply #15 on: September 30, 2013, 02:06:14 PM »

There was a plan for a biplane version chuck glider in one of the mid-'70s Aeromodeller annuals. Loved the CO2 version in the Hannan book...

Cheers,

Dan.
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Pete Fardell
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« Reply #16 on: September 30, 2013, 06:48:00 PM »

Thanks again yagua! Your description of your jig to make the central ring got me to rethink my own method just before I started winding on the balsa strips. I've now curved my jig too so that, hopefully, it will give an accurate shape first go. I used the front view on the drawing to get the correct curvature as you suggested. I've used thickish (1/8") balsa to give a decent edge, but still managed to curl it by slitting the underside and sticking it to paper to stop it falling apart. Thanks again for the suggestion. Tomorrow will see whether it is still possible to train the laminated strips around the edge.
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yagua
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« Reply #17 on: October 01, 2013, 07:15:05 AM »

I forgot to mention!! (and your pics remind it to me!): after a couple of fails, I end up using 2 reinforcement, 1 on the top (like yours) and 1 on the bottom side, both with a small thoot at the ends like yours. This is because that */&&%$%/&!!! thing keeps sliding away (up or down-way) Tongue Tongue
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« Reply #18 on: October 01, 2013, 11:03:30 AM »

Well it worked out okay. I used little strips of paper to temporarily hold the first layer of strip balsa to the jig and then CA glue for the other two layers. I only had to cut through the paper strips to remove it. I also sanded it a bit to get a rounder section- more like a willow branch. Thanks again for your very useful input.
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yagua
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« Reply #19 on: October 01, 2013, 11:46:34 AM »

nice pretzel  Grin Grin
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« Reply #20 on: October 03, 2013, 09:00:59 AM »

Hello Pete: found some pics of mine.
At that stage, it wasn´t complete. Still without the upper sticks, and pads between the X shaped structure (they are hard to see at the plans, but act like cushions for the arms when holding the frontal bar. I put 2 no each side of the X, 1 up and 1 down).
Also, as it´s for static display (and thinking about careless handling) the wood end up beeing pretty thick for the scale, as well as the fabric covering.
But the point is to show you how this one end up.  Undecided
I hope this pics are usefull for you  Undecided
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« Reply #21 on: October 03, 2013, 03:58:20 PM »

Thanks yagua.
Those pictures certainly are useful as my basic structure will be quite similar, albeit made with balsa and bigger. I really like your model. Any pics of the finished article?
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« Reply #22 on: October 04, 2013, 07:34:08 AM »

Sorry! no pics of the finished model  Undecided
I hardly finish it on time to send it to my brother via postal package (600 milles away) for his birthday.. (fortunately, he receive it exactly at his birthday!!).
With the final rush, I completely forgot to take more pics  Roll Eyes Roll Eyes
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« Reply #23 on: October 07, 2013, 07:08:09 PM »

Not to worry. Did you make a pilot for it by the way?

Bit of progress on mine. The hardest thing was deciding which order to do things in.
 I made the wings over the drawing before removing them. Then I laid the tissue flat on the drawing and stuck down the paper scalloped edges (which I'd made by tracing) and then glued the wing frames down onto the tissue. Next I took it all off the board again and glued the cross part to the funny hub things.
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Pete Fardell
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« Reply #24 on: October 07, 2013, 07:10:35 PM »

 I fixed in the circle piece before before adding some more bits and trimming the tissue. The wing will get its camber once I put the two ribs on each side. These ribs go on the topside and I've made them by laminating strips which I will sand a bit thinner tomorrow before fitting them on.
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