Slingby Hjordis, scale 1:5 with e-drive

[bocorvin]

Hello everyone,

Why a new glider? I enjoy building, but also because I had some tense moments with slope flying, trying not to land down the slope. Changes to our field had also made towing more difficult. With some mixed feelings, I thought about a scale glider with electric drive. I found that a difficult compromise. Fortunately, there was is coincidence and also Martin Simons' book. It featured the predecessor of the Slingsby King Kite, the Hjordis.
The Hjordis has an almost round fuselage, which I thought would be perfect for a e-drive.
First, a some notes about the real Hjordis, a prototype, only one built. In England, the development of gliders was less spectacular than in Germany. Due to the peace treaty after WW1, a great deal of energy was put into the development of gliders in Germany. In England, this changed in the 1930s, resulting in this more or less successful attempt. Only one Hjordis was built, and it had its shortcomings. For the full story, see the link below.
https://all-aero.com/2025/04/11/slingsby-hjordis/













The designer, Buxton, sought optimal performance and drew an extremely slender round fuselage with a pylon on which the wing was mounted. The pilot just about fits (not 😊) and the cockpit canopy fitted nicely to the pylon. The wing was beautifully slender, with a chord of 117 cm at the root tapering to 30.5 cm at the tip, with a wingspan of 1555 cm and a aspect ratio of 21. However, it had a thick and curved profile, from Gottingen 652 at the root to RAF 32 at the tip. It was a fairly revolutionary aircraft for its time. To be able to reduce speed, Buxton had come up with the idea of making the rudder double, which could then be folded out. There were other gliders (the Elefant) that tried this, but unfortunately it did not work. As a result, it had no spoilers or anything like that, which in hindsight was a great loss. I am definitely going to install spoilers.
Another problem was the very small cockpit. The fuselage was 660 mm in diameter and the pilot, Phillip Wills, suffered from cramps and splitting headaches in that claustrophobic and hot cockpit. By scutting out a few “chunks” out of the fuselage at shoulder height, he was able to sit a little better and the ventilation was also improved






I haven't read anything about getting cold shoulders... Martin Simons' book tells the whole story beautifully.
Now for the model. I am very happy with the size of my Nemere, scale 1:6, wingspan 330 cm. When I build the Hjordis on a scale of 1:5, it will have a wingspan of 311 cm and weigh between 2.5 and 3 kg. Hopefully it will be possible to launch it by hand and it will also be easy to transport. Because the wing is mounted on a neck, a modern profile is not so noticeable. The wing is covered up to the rear spar with ply, then transparent to the TE, as can be seen in this photo.






I started drawing the fuselage, with Devfus, based on the existing drawings. I couldn't get the nose to match the photos. In the photos, the nose looked more pointed than in the drawing, so I decided to make the nose a little more pointed, which also meant that the e-drive with spinner would fit. A little bit of cheeting is allowed now and then.....









A three-dimensional image of the fuselage gives a good impression and, no, it's not a submarine! The internal reinforcements for the pylon, battery and removable cockpit can also be seen here.





I want to make the frames from 3mm light plywood, with 3x3 pine stringers.
I plan to build the fuselage on a jig, like my other models. First sheet the bottom with 0.6mm plywood, remove the fuselage from the building jig and then sheet the top.
I was enjoying myself and decided to draw the wing as well, using Devwing.
For the airfoil I wanted to choose HQ 2.0-9 at the root to the aileron, then tapering to HQ1.0-1 towards the tip, in the hope of avoiding tip stall.










It would be nice if I could get a model that flies well in thermal, it is all flat over here, no slopes.
Since I was sitting at the computer anyway, I used Ecalc to calculate the main spar, 2 mm x 20 mm spruce upper and lower, which would give it a strength to withstand 14G.

I was also able to calculate the wing connector and opted for a rectangular tube that fits nicely into the spar, 12 mm high x 15 mm wide. Made of UD glass with epoxy, it should be able to handle 20G, which will not fail, I presume.

To be continued,

Vincent (DB)

[VincentB]

Salut Vincent
On va prendre du plaisir à suivre ta construction merci de nous la partager

[sebastian92]

Vincent D. l'infatigable
You said : "I enjoy building" : I'm not going to tell you otherwise
ça a l'air vraiment génial ces logiciels devfus & devwing !
Un jour il faudra que je regarde si c'est compatible pour un Mac…
Nice to follow your new building !
Seb

[bocorvin]

Vincent et Sebastian,

Merci pour votre reaction aimable (nice words)

Vincent (DB)