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Old Jan 13, 2015, 03:52 AM
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Build Log
Akaflieg Stuggart FS-26 Moseppl - 2.5m 1:5 scale

This model is a 1:5 (semi)scale version of the FS-26. The plans that I am basing the construction on are by Modellbau Wanitschek. Unfortunately, I don't actually have the construction notes - only 2 pages of the plans. This means that inventive thinking is required along the way!

As I will explain later I am going to stick fairly close to the original plans. However, like all projects I am going to change some things along the way. I have a 3D CAD model for the aircraft, and from this I can CNC cut the parts that I require.

My projects tend to move at an erratic pace, so we will see how this one goes...

Key Statistics - from the modellbau-steinhardt web site
Profile: E-182
Root Chord: approx: 270mm
Wingspan: about: 2.52m

Previous threads
http://www.rcgroups.com/forums/showthread.php?t=1176788 (General info request)
http://www.rcgroups.com/forums/showthread.php?t=1182068 (Re: airfoils in Modeling Science)
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Old Jan 13, 2015, 04:01 AM
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NSW, Australia
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General Notes

Because I have a number of molded fibreglass parts that are already designed to fit E182 I am not proposing to alter the root airfoil. Although there may be many other airfoils that would be as good, or better, I don't really want to modify the glass work. In addition, I did some modeling in XFoil and I think that E182 will work OK.

Although the FS-26 is a sailplane, the model is not going to be the lightest thing in the sky. So we will also take that as a given.

Interesting Challenges

1) Keeping the weight down! At this stage I don't really know what the AUW will be, so I am going to try and keep the weight down as best as I can during construction.

2) Attaching the fins. I have two glass fins that need to connect to the central wing section and the plans do not describe this attachment in any way - so this will require imagination when I get to that part.

3) The CG. In line with keeping the weight down I don't want there to be any lead in the model for the correct CG. Because of the totally unknown nature of this model I am going to construct the wings first and then try and work out the aircraft balance and complete the construction in a manner that gets the correct CG.

Intended Modifications

a) I am going to use direct servo control and separate rudder servos rather than the original bowden cables.

b) I am going to try and construct an all moving tailplane (in line with the original aircraft), rather than the horizontal+elevator shown in the plans. I have decided that this will be more compatible with direct servo linkage, so we will see how this works.

c) The model will be electric. This may well affect the model balance, and thus obtaining correct CG without lead, which is one reason that I want to build the wings and then see how the weights look.

d) The plans have fixed undercarriage (wheel front and rear). I would like to make the rear wheel, which protrudes the most retractable. I have a nylon retract to suit a 2.5m scale model that looks exactly the correct size. So, weight permitting, I am going to build this into the model.

e) Wing joiners will be CF tubes in a glass sleeve. (PBG 95TS 1/2" tube).
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Last edited by TugBoat; Jan 13, 2015 at 04:18 AM.
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Old Jan 13, 2015, 04:20 AM
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Construction Weights

Parts as delivered:

Body: 182gm, 199gm
Left Fin: 89gm, 90gm
Right Fin: 85gm, 97gm
Rear Deck (solid): 41gm
Rear Deck (openings): 32gm
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Last edited by TugBoat; Jan 13, 2015 at 04:38 AM.
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Old Jan 13, 2015, 04:24 AM
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Obtaining Key Parts

A complete set of glass and carbon/glass parts are available from www.modellbau-steinhardt.de. I decided to purchase these parts (and the plans) as this is the simplest way to get all the required molded parts. See: http://www.modellbau-steinhardt.de/rumpf/fs26.html for details.

Due to the high cost of transport I purchase two sets of parts. Because there were two possible rear deck - one is solid, and the other has holes for access - so I purchased one of each. The canopy is available in various colours, I ordered "smoke" as the canopy colour.

The glass work is good, although the finish is not high gloss like a modern composite model. So I may paint the parts once the model is complete, I have not yet decided.

The parts (except the canopy) are glass & epoxy. The base of the fins is untrimmed - ie. the various parts have a different 'foot print'.

I also ordered the plans, and they arrived as two sheets - no instructions are included. The plans are good, however, not all parts are shown in detail, so you can't really proceed directly from the plans. Also, as is typical of plans from this period, they are not computer drawn and so some of the parts that should be symmetrical are not quite symmetrical.
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Last edited by TugBoat; Jan 13, 2015 at 04:32 AM.
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Old Jan 28, 2015, 03:53 AM
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Vertical Fins

One of the slightly unknown aspects of the construction is the mechanism used to attach the fins to the centre wing section.

As supplied the fins have quite different trimming around the base. This isn't a problem, however, I will need to trim the two that I use the the same shape once I get a bit closer to determining exactly how this works.

The fins also have a section on the rear that is on the lower surface of the airfoil.

The plans have a dotted line that I am taking as representing the base of the glass/epoxy fin.

At this stage the feeling is that the fin should sit on top of the balsa sheeting for the wing. It looks to me as though the fin should 'hook' over the rear of the airfoil and then is glued to a former that sticks up into the fin. Although I have to admit that I don't quite see how this is going to work.

Additional work that involves the fins:

- build some rudders
- add some fill in balsa at the rudder hinge point
- mount the servos for the rudders and horizontal surface
- make the attachment point/mechanism for the horizontal surface
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Old Jan 28, 2015, 04:05 AM
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Central Wing Section

The wings are in three parts. The central section attaches to the body, and also the fins. This central section is approx 440mm wide, then the outer wing sections are just over 1m each.

The first step is to cut the main spar, then assemble the ribs, sheer webs, fin attachments and the rear spar.

I want to be able to remove the wing from the body so that I can access the retract etc. so I have included 3 location points for 5mm nylon screws to hold the wing to the body.

Also, I have added a rear spar and an extra fin mounting point.
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