Hi,

it's been a long time since I posted the last time here (been quiet busy and out of town). Anyway, having th spar caps ready in place, I moved on to the shear webs, which are up to the first one 0.6 mm birch ply. The first shear web is 3mm poplar ply, which we use normally for the ribs. We decided to thread mill this one to fit in the thin pultrated carbon joiner tube. I also attached a 1 mm birch ply band on the leading edge. This piece closes together with the shear webs and the sheeting the torsion box. The final leading edge will be glued on this band later after sheeting the top and bottom sides. After fixing the band, I was able to start with sheeting the top side.

@Stuart: No idea how they got the the airfoils. I guess it was by trail and error
@Miguel Ángel: Good to hear that you're enjoying it

Cheers,
Andrés

Beautiful work as usual Andres,and you make it look soeasy!
Regards Stuart

Adres

I agree, super job made look easy. I know how difficult it is to make a nice clean build.

John

Stuart and John,

the first couple of times it's difficult and the result does not always match one own's expetations , but after settling into a routine the crucial points are clear and it works each time better and better

Cheers,
Adnrés

Hi,

time for some more pics of the H-I. After having done the upper side, I started with the bottom. At this stage, it looks almost done, you turn it around and have always the same surprise of still having lots to do .

I used some balsa wood at the trailing edge to support it. The thin strip of ply on top and bottom would else give a fragile edge. Then you follow essentially the same steps as for the upper side: planking and scarfing. The wings are kept in a jig with weights on top. The sheeting of the torsion box is fixed on leading edge using clear parcel tape. Having done the bottom side, I went on to finish the centre section.

The centre section is tricky. The cabin is a sort of short wing section on top of the main wing and the intersection of these needs some care. Luckily, the main piece can be used as a jig for the cabin. I started with pre-bending a piece of wet plywood for the trailing edge of the cabin, which was easy to glue after having dried. I started then to plank the rear of the cabin with 3x7mm balsa strips. I used mostly UHU-Hart and instant adhesive sometimes for pieces which were hard to keep in place (only on the inner side). Using thin strips produced more work and it took a while until the cabin was closed, but the result was convincing. After sanding the balsa, I scarfed joined the last pieces. Note that the cabin is still not fixed on the main piece, allowing to work well on the the main piece (sheeting and servo installation).

Cheers,
Andrés

That's a complex part.Planking looks good,last pic it's ready to hitch up for a sleigh ride

More pics of the sledge

After having done the cabin, it was time to install the servo for the tow release. I would do a couple thing differently now.

Most important is that the release is too high at the moment. The angle between the airfoil chord line and the line connecting the CG and the release should be about -5° to -8°. This means in clear english that, the release has to be installed slightly below the wing. At the moment this angle is almost zero, which makes an aerotow difficult: the pulling force produces a negative pitch torque sustaining the wing at about 0° AoA. Thus, resulting in high take off speeds. In a tailed airplane the aerodynamic pitching moment produced by the long fulcrum "tail" is high enough at low speeds, which gives a chance to counteract this effect. However, the flying wing is short and has (ans needs) in general a smaller pitching moment derivative dMy/dalpha. The pitching torque produced by pulling cannot be counteracted as easily. So in essence it means that, we have to take care and estimate the CG position on the Z-axis sufficiently well to select the position of the release. Next time!

Wolfgang adapted his wing and installed the release with the angle mentioned. By the way, the release is selfmade and just a couple of pieces of brass tubes (Ĝ6mm outside) and steel wire (Ĝ1.2 mm). It releases perfectly, even in stressfull situations

Having installed the servo and the release, I started to sheet the bottom side. I used 0.8 mm and 0.6 mm plywood for the front and rear, respectivelly. The pieces meet on the bottom spar cap and need, thus, no scarfing to be joined. The sheeting of the top side is 0.6 mm. The loose cabin was used to mark the opening for the canopy, which was carefully opened with a sharp knife. I used this time another type of wood for the leading edge (normally I use spruce). I got a couple of years ago some birch from Johannes. It's very hard, was a lot of work to shape with the plough but looks great. I fitted carefully the canopy to the shape of top side of the center section and glued these together.

There are a couple of things to take care in the wings now...

Cheers,
Andrés

Looking forward to your flight report about towing with the nose mounted tow hook location. IIRC, Brian tried the nose mounted tow hook and reported that he had to be pulled off the ground by the tow plane. Not sure what happened with Brian.

Without much study or research, I tried a tow hook location on the belly, way back from the nose. Using a towing sled it just jumped off of the ground. With the fantastic speeds that my tow plane pilot flew, the glider was placed at a very high angle above the tow plane, without elevator input from me. I just kept it pointing the right direction. Happily without a stall.

Kent

Looking great Andres.Neat work cutting in.
I see what you mean about the release(neat idea)although you lost me with dMy/dalpha should make for some "interesting" launches.
Stuart

Hi Kent,

the angle should be between the best glide and least height loss. If you go further, the wing might stall . The problem lies in having a good estimate on the CG position about the yaw axis. We've done a couple of towing tests. Some went bad because of not enough power, and others because of the tow release position. We'll have to test more. I'll probably will have to pull full up during the first meters, against my normal instict...

The new position looks like in the picture below. The difference seems to be small, but I expect a great change in behaviour. We will see how Wolfgang's does. He is at the moment very far from home (China) and wait eagerly to get back home to build. I hope in summer we are going to have two H-I in the air - we have plans of meeting in Bremen.

@Stuart: sorry for the technicality, it's a "work related disease" . I meant just that the pitching moment that restorts the AoA to a steady value is less dependent on the AoA in flying wings than in tailed airplanes, i.e. small torques change more easily the AoA in flying wings.

Cheers,
Andrés

Thanks Andres,I got the gist of what you meant.The last pic illustrates well how such a seemingly small adjustment can make a good deal of difference.
I certainly hope you'll eventually do a kit of some sort for this,I'll be first in the queue if you do.
Stuart

Stuart,

at the moment we have no specific plans on making a kit. We are still optimisig the CAD plans. Wolfgang has to finish his and we have to do some more testing. If we should do make a kit, we'll surely think about you.

The last pic illustrates well how such a seemingly small adjustment can make a good deal of difference.

Yep! Due to its smaller sweep back, the lift of this wing reacts strongly to changes in AoA (also felt in the high elevon sensibility). BTW, this effect should be an issue in planks too, which have a much smaller pitch stability in general...

Cheers,
Andrés

Originally Posted by andrecillo76

Stuart,

at the moment we have no specific plans on making a kit. We are still optimisig the CAD plans. Wolfgang has to finish his and we have to do some more testing. If we should do make a kit, we'll surely think about you.


Yep! Due to its smaller sweep back, the lift of this wing reacts strongly to changes in AoA (also felt in the high elevon sensibility). BTW, this effect should be an issue in planks too, which a much smaller pitch stability in general...

Cheers,
Andrés

I consider myself forewarned!
Stuart

Lads,

another hard week is finally over (12-14 hours of work per day and up to 16-17 hours on Thursday ). Anyway, I don't want to weep around . Posting here is the right thing to relax!

Having finished the cabin and the center section, there were some minor details to finish the wings. To make the wing tip, I watered thin spruce strips and let these dry on the edge. After having dried, I glued the strips onto the edge and shaped these with a plow and 80 grit paper.

It was then time to install the elevon servos. Not my favorite job . I used Graupner's DES 488 digital metal gear servos. Strong enough and reliable. I made the mistake once of using nonmetal gear servos. Never again! Anyway, the wing is sufficiently thick to have internal links. I bent the links to have the right shape and made 1,5 mm glassfiber reinforced epoxy elevon arms. The kinematics are slightly nonlinear, but hey, why else should we have computer TX-RX systems for .

Having wired everything - I use green MPX connectors for the wing/center section connection - I covered the wings. I painted the wings with water based scumble and parquett floor varnish before. I like to use a noncertified fabric designed for ultralight airplanes (Superflite 104A), which weights about 60g/m², is heat shrinkable and comparably cheap. The fabric has to be glued with adhesive varnish. I used tape to cover the wing and to appply the glue only on the edge of the open sections. The adhesive has to be applied at least three times!The fabric can then be glued on the open section by rubbing with acetone. With a very sharp knife, the fabric is cut in shape. The tapes are then removed and the fabric is shrinked carefully with a hot gun or iron (not too hot!). Then varnish is applied a a couple of times over the whole wings.

I was almost there. Only a canopy was needed for the maiden!A positive for the clear vivak canopy was sanded with 80 gri down to 200 grit sand paper out of green Styordur. Before I finished the clear canopy, I decided to use the unfinished workpiece of the positive for a maiden

Erstflug H-Ic 1:8 (1 min 22 sec)

The rubber we had was very strong and only short flights were possible. Nontheless, the wing seems to fly well and it was worth to do more testing and to go further with building the fin found on the original H-Ib. At this stage we named it the H-Ic, a later finless design of the H-I. It was almost impossible to pull the rubber and keep the wing in hands without a fin, so we really needed the fin!

Cheers
Andrés

Originally Posted by andrecillo76

Nontheless, the wing seems to fly well...
Andrés

Congratulations on the maiden !!! The finished plane looks great. Nice job on the wing tip and the railroad engineering in the blue carpet photo.

Flight testing any prototype always provides some surprises...especially true of Hortens. Everything has to be just right or you'll have many MANY surprises. At least that has been my experience.

Did you happen to shoot a video of the recent maiden? Although I've manage to fly a couple of different Horten style ships, it always amazes me to see a new design fly. I am sure that the production studio that produces your epic videos will need time to produce. The drunkards that produce my videos can't even manage to clean the lens before shooting...

go further with building the fin found on the original H-Ib

By fin do you mean the lower "main skid" type fin? Yes a big fin is handy for a high force bungee launch. I believe it was your Sept. 2012 video that taught me about holding the nose of a Horten for the high force bungee launch. With this technique, I was ultimately able to hang on to the model at about 60 lbs of force...and as you can see from the video, I'm no body builder. As I recall, footing on the dry grass was more of a problem.

Kent

Horten Launch (0 min 3 sec)