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, Insider  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!

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_182205872

As 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

A case of No_glue

 Epsilon  Comments Off on A case of No_glue
Apr 242014
 

IMG_20140422_142127Yeah it happened again.. Somewhere in the forums you read that the original might have a bit of a problem getting into the air when it is windstill. Yes, I remembered after launching (not hard enough) in near zero wind. Result: An unscheduled landing (to use a phrase I hear ´mericans use when they crash something). The motor sprung loose. Now it was really not a hard touch, but enough for the no-glue to give up.  During the repair , I could not discover anything that could pass for glue at a 100 yard distance.  Anyway, whipped up a bit of my magic potion, and now the motor will never break loose again!

Today I had a few more flights, no problems to report. More work on the CG, I am getting closer to the ´Right Spot´.

With the present setup I reach 100 odd meters in 30 seconds. Compared to the 3 secs on the Insider, that´s an eternity. A Plan is needed. I made a quick set of jumper wires so I can plug in the current sensor that I use in the Extra. When I know what current I use, I can try to find a better setup. (Even one that runs on 4S if needed!)

Update: A fresh new Unisense-E does the job: 61 peak, 50 Amps in climbout. It also tells me starting power is 736Watt, at the top I’m at 550 Watt. This is a plane that weighs probably 3 kg’s!

I’m pleased with the unisense thingy, it’s all you’d ever need for a e-bird.

When the weather changes, I’ll get the vario sorted, I think I’m dropping 70 cm/sec in still air, but hopefully that can be improved upon. Slow speed is not the answer here, keep it moving to get the best sink-rate. It does not really matter too much if it is not accurate, at least not until I get the hang of the sounds.

 Posted by at 7:22 pm

Gliders gliders everywhere…

 DLG, Epsilon, Insider  Comments Off on Gliders gliders everywhere…
Apr 232014
 

IMG_20140420_194858-1Due the the fact all noise has been banned from our field, (except of course from the geese, motorcycles, tractors, mopeds, powerboats etc..) one has to adapt to the situation. Therefore no moaning, just use whatever you can. I´m having lots of fun with my Orion/Insider. After the mishap a while ago, things seem to have settled. I´m using a 14*10 prop now, and get up there ´real fast´. Could do verticals, but it is sometimes hard to see what goes on, so simply going up at an 80 degree angle is good enough. Last time I looked at the logs, I think they show that power is switched off at 100 meters (says the Vario) but it keeps on ascending to 140 meters. Once it goes, it goes!  (For my own record, CG is at 97 at the moment.)

IMG_20140420_133811 Last weekend the poor Blaster suffered a mishap from a pretty violent wind-gust, that lifted both my small Extra and the Blaster in the air and smacked them right into the fence. Not a happy day for the Blaster. There´s some damage on the tailfeathers, so far I´ve fixed things with some tape and it flies again. I´m contemplating if I should repair,  trade up or order new parts.

IMG_20140422_142127

I revived the Epsilon. Never got the hang of it last year, mostly due to lousy batteries. Today´s efforts were positive, we go up at a reasonable speed, but it is not an Insider! I also need to find more ballast or a bigger battery, but things are manageable. I find the flaps extremely effective. You can only deploy them for a few seconds, the plane really stops dead in the air. Fun to watch, but maybe that explains why the manual says to deploy them only. There is a long thread on Rc-Network-de, basically it boils down to:

  • It´s heavier then it´s predecessor. The weight mentioned in the sales-blurb is grossly wrong. I figured that out! Think 3.5 kg.
  • People quickly convert to a 4 cell setup.
  • Flaps need modifying to be able to follow the ailerons.
  • Braking is really effective.
  • Wings are a pain to mount.
  • Mounting stabilizer is questionable
  • Soldering of the elevator wire!
  • Use decent servo´s

Pic below was taken on a Saturday, but due to the restrictions I can not tell you when it was taken.

IMG_20140329_145107

 Posted by at 6:17 am

‘t was a lovely day..

 Insider  Comments Off on ‘t was a lovely day..
Mar 112014
 

..but it was cut short by something unexpected. When I launched the Insider for the first flight of what promised to be a lovely day, I got as far as 10 feet up, then a loud bang, lots of stuff falling from the forward area of the glider, unsettling silence, and then nothing.. Luckily I did have full control, and was able to land safely. My first hunch was that the prop clipped the canopy, but I can’s see any signs of the prop hitting the canopy. One blade of the prop broke off approx 2 cm from the root, it was later found approx 30 meters back from where I launched. Puzzling. The canopy support pin in the front was sheared off, so if it was not the prop, it was something on the inside trying too get out that broke it. After doing a lot of thinkings last night, I feel what could have happened, is that the motor wires got caught in the motor (there’s not a lot of space there). That caused the controller to follow the wires, hitting the on-off switch, and finally the cockpit. Altogether not good.

Or could the prop have sheared, causing some violent movements up front, that threw things around? I checked the max prop RPM, it’s rated at 9000 RPM. Not sure it I got close to that or not? Ecalc tells me I’m only doing 6500 RPM, so it’s not that.  (But I do have over 2:1 power to weight ratio)

Moral of the story:  if you ignore the little voice, that tells you to do a proper pre-season, take it all apart check, then punishment is to be expected!

Since I’m in the dark about the cause it’s going to be a try again and see what happens.

 

 

 

 Posted by at 7:49 pm

Two hundred twenty in 10 secs.

 Gliders, Insider  Comments Off on Two hundred twenty in 10 secs.
Mar 012014
 

Screen017No cheating! So with approx 40-48 Amps on the clock I get up to a very nice altitude in 10 secs. I’m sure someone will laugh at these numbers, but for me they are quite acceptable. I now need to dial in the ascent a bit, make sure it stays on track. For the rest, the weather is not the best for checking out the gliding part, but hey with 10 min plus flights on a miserable windy day, I’m happy.

Power4SLooking at the plot, you can see I have a rather soft/slow motor turn on.  That gives me a second to make sure nothing funny happens before launch. Peak power 700 Watt on launch, settling down to 550 Watt on the climb. Don’t really think I want to try that big prop yet! (Btw, the horizontal axis is not seconds, just x-number of samples)

Screen018

4 Cells it will be!

 Gliders, Insider  Comments Off on 4 Cells it will be!
Jan 262014
 

IMG_20140126_123343Grabbed the battery by the leads, and did some radical surgery! The truth is, I did not have a 4S handy, but 2 pieces  of 2S were waiting to be used for something. It’s one of these things where the warning label says: Only do this under the supervision of a responsible adult.  Since I’m slowly converting to the yellow connectors, I went from there. My Unilog current sensor is one with 4 mm connectors. Therefore some surgery was required. The end result is a more compact unit, where one side still has my 4 mm anti-spark connector, while the other side has a matching yellow bit.  Size and weight wise I am more or less close to where I was before. The only trade-off is the capacity of the battery, it’s slightly lower of course. But since it’s a glider, who cares. I just finished charging and gave it a try.  57 Amps! Now we’re talking 😉 That’s approx 850 Watts static. Slightly higher then the previous 300 Watt. My battery is a Nanotech 2650 mAh, rated at 20-50C. 20C is 66 amps, so I am safe there. My controller is a Robbe BL 690 , which is good for 70 Amp peak. I know the motor is good for 450 Watt. Ouch!  Got another prop somewhere: 15 * 8 in stead of 17 * 8 Aeronaut. Testing again (static) I read 45 Amps or 675 Watt. That feels slightly safer for now. It used to take 15 sec’s at a leisurely pace to get to 100 odd meters.  Double the power is double the height? I’ll go for a 10 sec run first!

What happened to all the Big planes? Nothing, we are in an nature conservation area,  not allowed to fly combustion engines from Nov-April.  Never mind that my Carden makes less noise then a 1000 geese! It’s something we have to live with.