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Jul 07, 2006, 02:00 AM
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Build Log

GUPPY electric sailplane Building&flying PART 1

EDIT, JAN.31. 2012
As photos were linked from other internet source, and that source change some settings, photos are not visible anymore in the Guppy Building thread. Sorry for that.
Please visit my website to see Guppy, or check Guppy 2 building thread on rcgroups.



I decided to show you my design of electric sailplane here. I made also the plans for it.
The sailplane could be build also as pure sailplane without motor.

Model is build entirely from balsa, only the boom is build from balsa glued around carbon tube stiffener. Covering could be Oracover or similar.

There is also a version of "Hotliner wing" for this sailplane available.

Model could be build from plans, but there are available also the CNC laser cut parts.

Proud designer

"Bare bones" in front and finished model in back. The uncovered model is biuld as sailplane (look the nose)




NOTE: Some of the pictures in this presentation of the model are from different prototypes, so you can find here hand carved parts, CNC laser cuted parts and also parts made on CNC router. Don`t be confused also by fact, that there are included also some pictures of Guppies, that other modelers build and some are slightly modified or different from the "original".
Please use freely here presented information in order to gather as much useful information, so building your Guppy will be a piece of cake.

EDITED on 1. jun 2007:
I made a table of contents for this thread, so you can easily search for the particular part without wasting much time:
Last edited by ultralajt; Jan 31, 2012 at 01:37 AM. Reason: Add the link for plans on
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Jul 07, 2006, 02:09 AM
Nice work. What is the approximate wing span, area, and weight? What power system are you using, and how is the performance?

I'm finishing up a 40" bagged wing electric sailplane. See my thread in this forum for details.
Jul 07, 2006, 02:11 AM
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Now some technical data:

Wingspan: 1500 mm (59")
Wing area: 20,4 dm2 (316sq")
Length: 805 mm (31,7")
Take-of mass: ~480 gr (16,93 oz) depends on powerplant
- propeller: Graupner cam prop 6x3"
- motor: SPEED 400 6V
- ESC: Kontronik SUN 1000 (BEC 2A)
- batteries: 7x GP 1100

Servos: 2 x GWS naro (8,8g 0,31oz)


And some of construction details:

All parts alnost done. Final assembly next!
Last edited by ultralajt; Jul 07, 2006 at 02:27 AM.
Jul 07, 2006, 02:16 AM
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There are CNC laser-cut parts available!

Laser cut balsa parts for Guppy sailplane.

Yes! The fuselage is also from balsa wood!

But looks like it came from mold!
Jul 07, 2006, 02:22 AM
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Well, it is time now to describe assembly of this model.

Lets build a horizontal tail!

It is build from balsa sticks, but also covered with balsa. It is light, but very strong too, what is somethimes very usefull quality during bad landing or handling with glider.
The elevator itself is build from solid balsa, with some lightening holes and it is sanded into triangle cross section.

Making the horizontal tail.

Elevator detail...cross section and lightening holes.

Finished tail, waiting to be mounted.
Last edited by ultralajt; Jul 07, 2006 at 02:49 AM.
Jul 07, 2006, 02:44 AM
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Lets make the wing parts!

If building from plans, there is a solution to print ribs on paper, glue them (3M spray glue) on the balsa and carefully carve them with modelling knife.

The wing sections are build on the lower part of D box. It is a 1 mm balsa sheet.
I use some rubber bands that help me to hold parts on place until glue hardening. It is kind a funny aproach, but the end result is without flaws.

Wing after asembly under rubber bands pressure, with help of some balsa longerons to apply pressure to front and rear part of D tube sheeting.

Carving the wingtips from solid block of balsa.
Last edited by ultralajt; Jul 07, 2006 at 02:57 AM.
Jul 07, 2006, 02:51 AM
North East England
That's a beautiful model, Mitja - looks very elegant. The fuselage looks more like a fibreglass moulding than carved balsa. Look forward to seeing more of your build.

Jul 07, 2006, 03:30 AM
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Thanks Redbaron25!
Indeed many of observers on the field dont believe that is wood! And many of them dont believe even when they take model in their hands!

Well, we will return to fuselage manufacturing later.

Lets finish the wings first!

When stock triangular wing trailing edge balsa is not available, we can make it by carving one from flat balsa of apropriate thicknes. I usualy start with modelling knife, then with plane and at end with sanding paper glued on the piece of plywood.

Sanding triangular section of elevator...same as TE of the wing.

Sanding the wingtip curve with help of CA glue bottle.
Jul 07, 2006, 03:43 AM
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Wing twist is needed because of strong trapezional outer wing panel, to avoid permature tip stalling. LE of the wing tip is rised for about the thickness of slim CD cover (5 mm typical)
This dramatically improove the wing behaviour on sharp circling or at minimum speeds.

Wing twist of about 5 mm (0,2") but of course the same on both wing sides
Last edited by ultralajt; Jul 07, 2006 at 12:21 PM.
Jul 07, 2006, 03:55 AM
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The fuselage.

The fuselage is basically a balsa box with triangle stock glued on inside corners. From outside is simply sanded to oval cross section shape.
It is not so hard to shave all materials from outer corners as it seems at start. We start first with rough planing the corners, and later we use sandpaper on the wooden plate, and later we use fine graded sandpaper with "bare" hands, to feel the shape. We dont use much measurements or templates here...we just finish with sanding, when fuselage starts to look good!

Basic fuselage parts...cockpit parts!

Bottom of the fuselage is laminated from 4 strips of 2mm balsa in template made from styrofoam.

Initial shaping of fuselage.

Finished product
Last edited by ultralajt; Jul 07, 2006 at 06:57 AM.
Jul 07, 2006, 04:04 AM
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Rear part of fuselage (boom) is build around carbon tube (6/4mm) and incorporate the vertical fin at rear end.
Inside the carbon tube, there is place for two control pushrods. They are 0,8 and 0,6 steel wire inside plastic bushings 2mm OD. 0,8 wire is for the ruder, and 0,6 wire is for the elevator.

Vertical fin and boom internal structure.
You can see the curved pushrod for the elevator, going trough the "ribs" in the fin. The curve should be done as smooth as possible, to minimise friction.

Joint between cockpit and boom parts of fuselage.

Finished fuselage with saddle for the horizontal tail on top of the vertical fin.
Last edited by ultralajt; Jul 07, 2006 at 06:58 AM.
Jul 07, 2006, 04:28 AM
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Almost finished!

We should cover the model with our favorite iron-on covering.
If you are affraid not to achieve smooth fuselage covering, you can cover it with light filler, sand smoth and then paint with apropriate paint. But this will add more weight than just pure iron-on covering.

I opted for nontransparent covering, but if you want to admire your skill for the details assembly, you can use one of the transparent coverings.
For the finishing touch I use self adhesive orastik, to make some water wawes, name and silhouete of small fish.

Now, we need to install the RC equipment and power!

Each of the servos are put in heat shrink tube. Servos are then glued to inside fuselage sides. Ona a little bit higher than other in order not to interrupt one with another when in action. There is a plenty room for the reciever, battery, ESC and motor.
On the picture, the battery pack is 8x KAN 750, and the reciever is Graupner R700.
Last edited by ultralajt; Jul 07, 2006 at 12:23 PM.
Jul 07, 2006, 04:52 AM
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And now, lets go flying!

You can download some of the videos here:

The second prototype build by my friend based on my first set of blueprints:

Flying the Guppy for fun (it is the final version of this sailplane and blueprints):

More to come!
Last edited by ultralajt; Jul 07, 2006 at 07:00 AM.
Jul 07, 2006, 05:35 AM
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Many RC modellers starts to build this sailplane after I published the blueprints and assembly instructions in our RC modelling magazine.

Maj/Jun issue of magatine TIN with plans and instructions.

Blueprint details:

Isnt a beauty?
Jul 07, 2006, 06:18 AM
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As I mentioned before, there are "hotliner" wings (with ailerons and speedy airfoil) also available for the Guppy sailplane. It is apropriate for the modellers that want more fun on the slope, or just playing under power on the plains.

Hotliner wing for free downloading:

And you can download also asembly manual for the Guppy...sorry, only in my native language for now, but pictures tells more, so... free to download:
But if the interes for this sailplane will grow, I could translate to English.

Jo to fly on sunny day!
Last edited by ultralajt; Jul 07, 2006 at 06:26 AM.

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