Another bit of Black Magic

 DLG  Comments Off on Another bit of Black Magic
Jan 042017
 

During our holidays in the home country I was entrusted with a handful of carbon, with the request to ‘just build it and enjoy’. Over the last few weeks that building process was finished. Even though the total amount of hours spend are not that many, it all adds up. Today I finally got a new receiver, so after the new batteries arrive, we should be all set to go. All up weight is 220 grams, which probably is a bit on the light side, if I compare it with the Tweagle. I ended up adding some extra weight to that one too. At 245 gram it has better penetration, and it fits my style better.  For this one I decided to make the wing detachable with a home made connector. The pins originated from a scrap cable assembly. (Good thing about working with medical equipment is, that there’s lots of good stuff that we throw away.) Of course I have read stories about bad connections. This one will not have bad connections!  

 

More after the first flights!

 Posted by at 3:35 pm

DG800-4

 DG800, Gliders  Comments Off on DG800-4
Jan 042017
 

It has been some time, but today is as good a day as any other day for a wee update. A lot of time has gone into designing and building a retractable u/c. The final result is good, even though I say so myself. I still want to make a mudguard but that can wait.

Making the wheel doors work properly was alo a lot of work, where I had to made a negative from the fuse, and build the doors into that. (The old vacuum installation was a great help here! )

 Posted by at 3:11 pm

DG800-3

 DG800, Gliders  Comments Off on DG800-3
Aug 252016
 

20160824_210436-1Mounted the elevator servo, I found a one in the box that will do nicely. I wanted to use a beefier link to the elevator, but there was not enough space. So a 2 mm version will have to do for now. Maybe change it for 3 mm if I work out how to do it.

I also cut slots into the rudder for hinges, but in hindsight I want to redo them in such a way that there is less visible ‘hinge’  on the outside. The whole rudder needs to be removable, there is a plastic rod for a 1.5mm steel wire built into the rudder, so this is easy.

20160824_210410-1Next task will be to think of a way to make a quick disconnect link to the elevator. I don’t want to use a standard quick-link, they do fail with repeated opening/closing. It has to be simpler, and less fiddly in daytoday use.

Let the mind think about it for a bit, it will find a good solution!

Flying this week is a bit of torture to be honest. 30 C plus and clear blue skies, with a slight haze is not the best weather, simply because it is very hard to see the plane beyond 200 meters altitude. No doubt I will regret saying this soon.

 

 

 

 

 Posted by at 11:07 am

DG-800-2

 DG800, Gliders  Comments Off on DG-800-2
Aug 202016
 

20160820_190758-1Part 1 is a bit back, describing how I did a quick and dirty cockpit frame. Today was the start of more serious stuff, like drilling the holes in the fuse for the all important bit in the middle! First I created a jig that holds and aligns the fuse, and made very, very sure that everything is perfectly level and square. Lasers and camera’s don’t seem to like each other, hence the lack of quality in the pic. I will probably be able to do another one, once the first expoy has hardened. To tricky to touch anything at the moment.

Once the sleeve is in position, I can cut off the outer parts, which will go into the wings. The manufacturer states in the manual they kept the hole in the wing slightly oversized to allow for wiggle room. What slightly worries me, is there anything other than the sleeve in the wing holding things up? Do I need to add something? Glass the wingroot maybe? Time for more research!

 

 Posted by at 6:54 pm

Logging your flights

 Gliders, Insider  Comments Off on Logging your flights
Aug 202016
 

Soaring leagueI discovered a fun website the other day, where you can ‘virtually’ compare your achievements with other pilots. Of course I am no match for 6 meter ships, but it is fun. Soaringleague.net is the place to visit. It is a pretty new site, I guess it’s real goal is to log GPS flights, but it works fine for me too!

Tagging the flights is a bit of an adventure yet, but I am sure things will improve over time, since the admin, Pascal is working really hard on it!

BestFlight from 2016-08-20 20-39-20My best flight sofar was a mindbogling, neck hurting flight of altogether 33 minutes. I defenitely need to invest in an easy chair to sit through long flights, standing and looking at the sky does not work!

Up to this point in life I had been concentrating on 10 min fligths, which are not to hard, but stretching things beyond 10 min is hard work when you start from 200 meter or less. (my trusted lady always tell me when I cross 150 meter, so usually I switch off at that altitude and a bit. )

 Posted by at 6:37 pm

DG800 from Rödel modell

 DG800  Comments Off on DG800 from Rödel modell
Aug 072016
 

DG-800-cockpitframe-trial1One minute you contemplate building yourself a nice big glider, next time you wake up you have a shed with a few big fish! So far it’s only a 5 meter ASK21 en a 4 meter DG800. Both in need of minor assembly. Since the DG800 is the smaller (and cheaper) one, I am going to try to get that one started first. The DG800 is a Rödel Modell kit, probably something that was made 10-15 years ago. (Haven’t been able to get details yet) However, the ”kit” is in pristine condition. The only giveaway of its age is the papertape holding various bits together.

DG 800 von Rödel
  • Spannweite: 4150 mm (mit Winglets 4400 mm)
  • Länge: 1790 mm
  • Gewicht: ca. 5700 g
  • Profil: E 207
  • Steuerung: Quer, Seite, Höhe, Störklappen, Einziehfahrwerk, Schleppkupplung erstanden.
Die Maschine fliegt an sich sehr gut. Ich bin sie einmal in den Alpen am Hang geflogen und hatte viel Spaß!
Leider habe ich sie bei diesem Erstflug fast verschrottet.
Das Problem ist, dass die DG, wenn du schon sehr langsam bist (z.B. Landeanflug) und dann die Störklappen voll ausfährst, schlagartig abreißt. Ich habe meinen Absturz zufällig auf Video aufgezeichnet und ihn x-mal angesehen. Kollegen von mir haben alle bestätigt, dass die Maschine nicht zu langsam war. Da scheint es wirklich ein kleines Problem zu geben, da der Abriss exakt mit dem Ausfahren der Klappen kommt.
Sobald die Klappen drin sind besteht keinerlei Gefahr und man kann die DG herrlich langsam fliegen.
Auch wenn sie es nicht zugeben, ich glaube das Problem ist bei Rödel bekannt, da ich nach dem Absturz von Rödel folgenden Rat bekam:
“Die Klappen nur halb ausfahren und gut Tiefenruder beimischen”
Kurzum wenn du die Störklappen voll ausfährst mußt du immer auf deine Geschwindigkeit achten.

Die Serie E-205/207/209 hat bei den typischen Modellflug-Re-Zahlen starke laminare Ablöseblasen bei mittleren Geschwindigkeiten, d.h. deutlichen Zusatzwiderstand beim beschleunigten Gleiten.

Die Ablöseblase kann man sichtbar machen, wenn man an einem ruhigen kühlen Abend, bei dem Tau entsteht, einen Flug mit gleichmäßiger Geschwindigkeit macht; man sieht dann nach der Landung einen “Tau-Streifen” auf dem ansosnten trockenen Flügel. Das ist das sog. “Totwasser-Gebiet” der Ablöseblase, in dem sich der Tau am Flügel absetzen kann, obwohl der Flügel eigentlich umströmt ist.

Warum erzähle ich das? Weil es sich gerade beim E-205/207 lohnen wird zu versuchen, die Ablöseblase mit einem Turbulator zu zerstören. Es genügt ein gerader Tape-Streifen (Zierstreifen aus dem Autozubehör), 2 mm breit, 2-3 Lagen übereinander, bei ca. 25 – 30 % der Profiltiefe (kurz vor dem “höchsten Punkt” der Profiloberseite). Der Leistungsgewinn kann spürbar sein, erst recht die (gerade bei Vorbildgetreuen zu beobachtende) Verbesserung des Überziehverhaltens.

Wenn man das Ablöseblasen-Problem löst, sind die Profile E-205/207 gar nicht schlecht; sie haben recht ordentliche Allround-Leistungen.
hab folgendes gefunden:
Das Profil ist für den gleichen Einsatzzweck gedacht wie das E 205, jedoch sollte wegen seiner größeren Dicke die Re-Zahl sicher über 100000 liegen. Das bedeutet Flügeltiefen möglichst über 240 mm. Das E 205 wurde für RC-Segelflugmodelle berechnet, die sowohl langsam in der Thermik kreisen sollen als auch schnell fliegen müssen, ohne daß die Sinkgeschwindigkeit zu groß wird. Es war daher bei seinem Erscheinen ausgezeichnet für die Klasse F3B geeignet. Inzwischen gibt es leistungsfähigere Profile. Auch für den Hangflug ist das Profil gut geeignet, da es bis hinunter zu ca = 0,1 recht niedrigen Widerstand aufweist. Die Polaren wurden im Stuttgarter Windkanal gemessen. Zum Vergleich wurden die theoretischen Polaren mittels des Eppler-Programms errechnet. Weiterhin sind die Ergebnisse der Messungen im Delfter Windkanal und die der Messungen in Princeton von zwei von verschiedenen Erbauern hergestellten Meßmodellen aufgeführt. Die theoretischen Polaren für den Einsatzbereich von HLG im Re-Zahlbereich von 50000 bis 300000 wurden mittels des Winprof-Programms errechnet.

Entwurf: Prof. Eppler
Quelle: MTB 1 und MTB 1/2; Model Builder 5/1982; Soartech Nr. 8 “Airfoils at Low Speeds”; H. Eder “Mehr Leistung mit dem Hand-Launch-Glider”, Verlag für Technik und Handwerk GmbH, Baden-Baden 1996, S. 106.

Clear enough: It’s good enough for a Flatlander!

Anyway, since a challenge is only a challenge if you create on, I decided to try and make a 2016 scale canopy. The original blow-molded plastic afair will be kept for nostalgic reasons). First I wanted to see if my idea sort of works. (My idea: likely something I read somewhere on ye interweb. )

DG-800-cockpitframe-prep1I want to create a well fitting carbon frame. Easiest way to make it well fitting, is to build it on the existing fuse. I stuffed some foam in the inside, and some foam on the outside to create a channel in which to stuff the carbon/epoxy/microballoons. Since it is a trial, it does not yet have to be perfect.

First impressions are: This works! Now I need to order some fresh epoxy, and do it for real. This time I will try to make the frame an even thickness, and offset it a bit to the inside, leaving enough space for the hood.

 

 Posted by at 5:31 pm

Does not time fly!

 Gliders, Uncategorized  Comments Off on Does not time fly!
Jul 272016
 

674It’s been a while, I must admit. We have the odd bit of summer, interspersed with bouts of autumn and spring and winter. That’s summer for you! Given the general uncertainty of the results of the plans of our minister Dobrin (He who wants to put a ceiling on all model-aircraft activities of 100 meters, so that amazon can deliver their stuff) I have decided for the moment to go gliding. That way I will most certainly be above 100 meters! Once you set the mind to gliding, big ones, all of a sudden the universe throws a lot of them at you. Looking to acquire an 5 meter ship, and possibly 2 pieces 4 meter something. All of them in ‘GFK fuse, and the rest is up to you!’ format. I love it.

So, plans for large biplanes are shelved for now, plans for more F3A-X/Imac planes are shelved. We goes gliding!

I have motorized the PURES a while back, and I must admit that e-PURES makes life easier on the bones. And I get to go up real quick, because I did not have a suitable size motor in the box, I took something that looked about right. On a small 1000 mAh battery it goes up like a homesick angel. Almost as fast as the Orion. And I can repeat that a dozen or so times on one charge. What more do you want?

677Speaking of Orion, it’s getting there too, being tuned in that is. We had a few quiet evenings, which allowed me to tweak CofG without too many disturbances. I am getting to the stage where hands-off circling is happening. Move the battery just a tad more to the front, and we are there. (at least in quiet conditions) This flight was on a Sunday, around 4 in the afternoon. Not bad for one of the first outings!

 Posted by at 5:59 pm

Out with the old, in with the new..

 DLG  Comments Off on Out with the old, in with the new..
Dec 242015
 

DSCN0106‘t Is the time of year to indulge in a nice wee present for oneself. Given that I need more exercise, I decided to treat myself to a fresh new DLG. The present Blaster is still flying well, but the new breed of DLG´s is just that, totally different animals. Rather then go for something ”foreign”, I decided to call Alex Hoekstra from Tweagle fame, to see if could make me a Xmas present. Lucky for me, the answer was yes. So a quick trip was organised ”up north” and soon afterwards I was able to take posession of a shiny black DLG. First thing you notice is: It weighs nothing! At home I quickly located my scales to find how much nothing is. Wing is 104 grams. (This is the D-box version), El/Ru together 10 gr. Fuse is 38 gr. All added up, we are talking 152 grams for bare carbon! At the moment, the fully assembled glider RTF sits at 230 gr on the scales.

DSCN0102I have 4 KST-08‘s fitted, a Jeti 5 channel RX, a small 2 cell Lipo from ”way long ago”, and my Openaltimeter found a place too.

I updated my Multiplex Cockpit to Jeti, but even though the setup works flawlessly, I might start saving for a true Jeti. Setting up the Cockpit is just so tedious compared to the a proper Jeti system.

Once I do some fine tuning I will probable loose a few more grams. (Wiring is bulky at present, I can also loose the connectors on the receiver, might still change the guitarstrings to a bit of kevlar, we´ll see.

Building a plane like this is not to be undertaken if you have never built something high tech like this. Do take you time planning your build. Everything is just strong enough to do the job, it is not designed to be bashed about in your typical overfilled hobby hideout! Look on RCG for tips. (or RC-Networks).

One thing to note, is that the weight mentioned on the website, is probably ReadyToFly, not bare carbon!

I do not have a lot of build pics, it turns out that fotographing carbon is difficult. Tomorrow we have a midwinter-spring, temps are predicted to hit at least 14C, good enough for a spin I would say. This will be the second outing, the first spins I made 2 days ago in 8 m/s wind, not really that good for a maiden flight. All I can say it went up like the proverbial homesick angel! The third toss showed a respectable 30 meters on the Altimeter, and this was just a gently flip of the wrist!

Merry Xmas everybody, and a Happy NewYear!

RES in the making too

 RES  Comments Off on RES in the making too
Mar 102015
 

IMG_20150517_182205872As a first build in our new residence I got myself a few RES kits from Josef Gergetz. RES stands for Rudder Elevator and Spoiler. It´s a class of glider measuring 2 meters span, and it is very restricted as to the materials and construction used. It is intended as a low cost platform for lots of fun.

specs are:

Name: PURES V2
SPW: 1990 mm
Länge: 1120 mm
Profil: AG 35 – AG 36 Strak (Mark Drela)
Flächeninhalt: 35,7 dm²
Abfluggewicht: 670 g
Flächenbelastung: ca. 19 g/dm²
Steuerung: V-Ltw: Seitenruder, Höhenruder, Bremsklappe
EWD: 0,7°
Schwerpunkt: 75 – 80 mm

There is a long article on RC-Networks, you can go and look at the pictures there and here.

We finally have a maiden! during the first fligths there was a mild westerly blowing from the lake. This usually goes together with turbulent air caused by the trees that line the shore. So lots of bumps are expected 😉

After a few tosses,  I felt a bit more gravity was needed in the nose, and feeling brave, decided to try my bungee. This one was originally intended for the little DS-Birdie, but who cares. First launches were made with approx 30 meters rope, enough to get up and see what happens.

Things were a bit confusing at first. I had decided to slave my aileron stick to the rudder (dual control really) since the standard recipe sets everything up on rudder/elevator. I feel more comfortable having my directional control right, and elevator left. However, I did not check if wiggling my right stick did produce the same effect as wiggling the left stick. Anyway, you figure out pretty quick when things do not turn in the direction you anticipate. No harm was done to plane or pilot, so after teaching the tranny to move surfaces the same direction on both sticks, more fun was had.

Due to the freshening wind I could not really do much more then hang in there. Adding enough rope to span the entire field gets me up to approx 40-50 meters. I am not sure yet what the correct way to get rid of the rope is once you are at altitude. My feeling is that I should fly past the vertical, at wich point I should have reached maximum height, give a bit of down to release the tension on the wire to let go, and off to blue skies above. Due to the strongish wind I have the feeling I was more or less flying like a kite, untill pushing down pretty hard to release.  Anyway, we will learn this trick too.

After lunch and a quick dash into the shed, I made a few bits of ballast. The main wingspar is a hollow 10 mm carbon tube, so it is easy to simply insert something. I had a few sizes of alu tube, which give me 60, 100 and 150 grams of ballast. (The plane RTF is 450 gram) . With the added weight (150 gram) the performance improved, I could fly against the wind and even make a few turns!

I just noticed that the stated RTF weight is 670 gram. Mine weighs RTF 450-ish. No wonder I needed to add ballast!! I must have forgotten to add some major parts to end up that low?? And I was contemplating making it even lighter! (Like get rid of the steel wires/tubing to drive the v-tail,  use ligther servo’s etc. I now have 60 gram ballast up front, I can probably reduce the RTF by that much if I try hard.

Next time I hopefully will be able to try in more favorable conditions, after all this is a glider for these long windless summer evenings 😉

Todo: probably a good idea to stick this one on the same tranny as my DLG, it is a bit of overkill to use a Jeti tx for this. I will also move my little altimeter/vario here, to see what happens during launch.

IMG_20150517_094324257

 

 

 

 Posted by at 8:50 pm  Tagged with:

When Insider meets Stork

 Gliders, Insider  Comments Off on When Insider meets Stork
Jun 272014
 

No, nothing exciting is going to happen. It just so happens that a family of those beautiful birds was passing, lazily circling near our field. Luckily I had my Insider at the ready, so a quick launch was followed by a very rewarding ride up the elevator! I am pretty sure I went up much faster then the birds, they just got their alitmeter set and are happy where they are. The weather was overcast, and under the white clouds I could see the Insider without a problem, going into the blue bits between the clouds was another experience. As you see I chickened out at 468 meters. This is the highest I´ve been, and I don´t think I am going to repeat the experience (until I find myself in favourable conditions again, of course!).
Meanwhile the Stork family left for Germany, I guess a silent orange bird is not that interesting.

I could not do this without listening to the vario, you try to keep a steady tone, so you know your speed is ok. Ocasionally I get the GPS speed, just for comfort. Depending on the wind I fly approx 10-11 m/s while circling. Going down is a matter of dialling in a nice steady tone on the Vario, it takes a while to see things getting bigger, but it does happen!

 Posted by at 6:17 pm
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