Kees

Noise (again)

Sound Comments Off

Feb 152016

I found myself volunteering for a role in the Noisy-committee of the club. We have to abide by the rules, so the first question is ”what are the rules?”

Following is just a collection of bits and pieces, just to get started.

Excel sheet for calcs (download to your pc)

LMFC

All about audio: audio-stuff

https://www.modellbau-bocholt.de/images/mbg/dokumente/flugplatzordnung_2011.pdf

Paragraph 9: 60 dBa at the nearest house!! Which is rather an important fact. Whivh would translate into 78dB(A) at our site!

https://www.laermorama.ch/m1_akustik/schallpegel_w.html#rechnen

Equipment: anything under 200 Euronen is not worth looking at.. It needs to be a Class 2 certified one.

Laserliner (various prices, from 160-270, so shop around. ) Can be calibrated!! wich is Very Important! Of course those calibrators are not cheap: calibrator. Why you need one (This site has a lot of good ”howto” info.

Wiki: Sound meters

Calibrator

We also have a very high back ground noise at the field, caused by the Betuwe Lijn. I have measured in excess of 60 dBA when the train passes on a quit afternoon. The houses that we want to ”protect” are much closer to the railway, so they already suffer from much higher noise then whatever we can add. That’s another story!

These guys did a lot of measurements, so use them to our advantage 😉

https://www.umweltbundesamt.de/sites/default/files/medien/461/publikationen/4005.pdf

Our location:

https://www.emmerich.de/c125747b002691ea/files/isophonenkarte_elten.pdf/$file/isophonenkarte_elten.pdf?openelement

https://www.google.nl/maps/@51.8666569,6.1551396,769m/data=!3m1!1e3

Worth mentioning is that the allowed noise level at this location is 59dBA during daylight hours. (in the LautstärkeGleichenkarte Elten above.)

source: https://www.emmerich.de/de/inhalt/drittes-gleis-und-laermschutz/

So, what is the max level that we are theoretically allowed to produce to reach the 59dBA level?? The distance to the houses is 200 meter (centre of field), therefore a max level is 77dBA is theoretically allowable. This is not to say that we should be lower!

Of course, knowing the level does not help you any further if you want to fix_it. Some kind of octave-filter app is almost a must, but most I-phone/Androids have plenty gadgets to held you find the offending frequencies. (Needless to say, it almost always is the prop/exhaust noise that is the cause of the problem.)

Procedure: from https://www.mfc-hameln-lachem.de/flugsicherheit/laermmessung

Die Messungen sind unter folgenden Bedingungen durchzuführen:

Das Flugmodell ist so zu positionieren, dass sich der im Abschnitt Lärmmesspunkte definierte Bezugspunkt in einer Höhe von 1 m ± 0,1 m über dem Boden befindet und die Flugzeuglängsachse parallel zum Boden verläuft. Das Luftfahrtbundesamt kann in Sonderfällen eine andere Aufstellungsgenehmigen.
Zur Vermeidung von Reflexionen dürfen in einem Umkreis von 30 m um das Mikrofon sowie um das Flugmodell keine die Messung beeinflussenden Gegenstände vorhanden sein.
Die Lärmmessung muss auf einem kurzgemähten Grasboden erfolgen.
Das Flugmodell ist so zu positionieren, dass sich die Flugzeuglängsachse in einem Winkel von 90° ± 30° zur Windrichtung befindet. Die Lärmmessung hat auf der zum Wind abgewandten Seite des Modells zu erfolgen.
Die Windgeschwindigkeit darf 5m/sec nicht überschreiten.
Die Messung muss an jedem Punkt über einen Zeitraum von mindestens 30 s erfolgen; maßgebend ist der höchste in diesem Zeitraum gemessene Pegel.
Die Umgebungstemperatur muss zwischen 10°C und 30° C liegen; keinNiederschlag.
Das Umgebungsgeräusch muss mindestens 10 dB(A) unter dem vom Modellerzeugten Geräusch liegen.
Die Messung muss bei Vollgas erfolgen. Eine Limitierung von Leistung und Drehzahl, die zur Erfüllung der Lärmschutzforderungen vorgenommen wird, ist nicht erlaubt.
Für die Messung muss ein Präzisionsschallpegelmesser nach DIN EN 60651 oder nach DIN EN 60804, in beiden Fällen mindestens Klasse 2, in der Betriebsart „langsam“ („slow“) und im Anzeigemodus „dB(A)“ verwendet werden. Die Kalibrierung der Messanlage mit einem akustischen Schalldrucknormal zur Überprüfung der Empfindlichkeit der Anlage und zur Ermittlung des Bezugspegels darf nicht länger als zwei Jahre zurückliegen.

Auf unserem Gelände gelten folgende Werte:

Kolbenmotor 82 dB (A) >> in our situation it is 78
Turbine 90 dB (A)

Also part of the whole thing a flightlog? (automated/RaspberryPi?)

Find a meter with a usb connection to a laptop and use USB extenders. (For safety mostly)

Make a decent test stand

Out with the old, in with the new..

DLG Comments Off

Dec 242015

‘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.

I 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!

Winter is here again, time for an update

Skybolt Comments Off

Oct 142015

It all of a sudden feels cold and miserable out there, so this is a good time to start a new project. For many a year I have wanted to build a nice biplane. The thoughts have gone from a Waco to a Starduster, or Acroduster. I finally settled on a Skybolt. The main reason for this choice at the moment is that I do have a set of Wendell Hostetler drawings, and I have located a live example not too far from home. Those two things should be enough to get started. The Hostettler plans says it has a 77¨ span, (194 cm in real money) 170cm long. This makes it transportable. Recommended engine says ´Quadra´(Don´t think you needed to spell out the size of the engine in 1997, there was only one size.), all up weight supposed to be 10 kg. Prop something 20×6. Of course this all sounds as if my trusty MVVS58 will do very nicely indeed. I even found an engine template stuck to the drawing already 😉

I have been tossing this around for a while, on the one hand contemplating making a new 2015 version of the plans, on the other hand, just start building. If you like it, you can build a round version with all the mods you think you need. And of course, building it the original way from the plan is in itself a ´historic´ job.

There appears to be a large amount of info available on ye interweb, so I will have to weed through all that too.

Anyway, with the mind set into gear, it is now a proper project. First some links I found for inspiration:

I probably do the smart thing and make a mockup of the engine/cowling/exhaust, just to see if it will all fit. The Quadra used to have a NoExhaust, I won´t get away with that! First thoughts are to try and hide a custom exhaust somewhere on the inside of the fuse.

Just spotted this add on Barnstormers.com, and this bit: Aeroclub NRW. I hope they are not selling this one!

more to come..

I built myself a 3D-printer

Quads Comments Off

Aug 132015

..after maiden fligth at Herwen.

..and a whole new world opens. This has been a project, both rewarding and frustrating. but I have learned a lot, and at present I am able to make quite acceptable printed parts. Of course this whole thing of 3D printed parts means you have to learn how to fit those parts into the modelling universe. Over the years you have build up a good feeling of material properties that work in different scenarios. This plastic stuff requires you to learn new tricks. On the one hand you seem to be able to make very complicated parts, but on the other, you find that the materials properties degrade very fast with higher temperatures. But it will be great to make little bits and pieces, as you need them for traditional moddeling applications.

might as well print a few spares

To start off I build a quadcopter. This is a PEON230 which I found on thingiverse.com. Seems a rather straightforward project. I choose to use a NAZE32 as the controller, running Cleanflight Kamikaze software. (As in the latest stuff, guaranteed to have bugs 😉

So far I have had 2 destructive crashes, both from 30 meters high. 1st one happened on the first flight (of course) because I lost orientation. The quad is rather small and at 100 meters it was hard to see which way it went. Rather then ending in the drink, I thought it safer kill throttle. NotGood when you fly a quad. Ah well, one has to learn! I have since added some LEDS from a led-torch to help me see which way we go.

take a selfie with your quad.

..added some headlights

Damage was actually minor, the top plate where the battery is mounted, cracked. I had printed it with 20% fill, obviously not enough! Since then I have had approx 5 hours airtime, and no major mishaps until last Sunday. I had been messing with my PID settings, and I thought is was a good idea to increase signal-loss RPM. supposed to prevent a fly-away when you loose signal. Somehow the opposite happened, it took off like a homesick angel, until I recovered from my shock. By then it was going towards the water, and much as I like a nice swim, I did not fancy taking any chances. So I chopped the throttle, this time knowing I was asking for a solid crash. However, the damage was again minor. Both the upper and lower support plates were cracked, (by the weight of the battery) but the arms were all ok, and no other damage was done.

The great thing about 3D printed parts is, is something breaks, you just fire up the printer and you get a fresh part! So after some minor disassembly I have now copter #2 in the air, looks the same as #1.

I’ve also started the construction of a tri-copter, looks like that is mechanically a bit more of a challenge. As always, in the beginning (the first few projects) you use what is there, then you start to modify the designs, then you make your own. The Brocopter (google Thingiverse) uses a servo to rotate the rear arm, the construction to rotate it is not exactly something I would trust, so this is the first part that needs redesigning.

and a tri-copter in the making.

RES in the making too

RES Comments Off

Mar 102015

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.

The new shed is taking shape..

Uncategorized Comments Off

Mar 102015

..and so is the house. Took a while, but hey, all good things come to those who are patient. Spring has been here during the weekend, and it could be nice tomorrow. If the weathergods are kind to me, I will be off for a few flights. Last weekend I had the Insider in the air, and after a first test-flight, I got an almost perfect 10 mins flight from 150 meters, landing within a wingspan from my feet. That´s not bad after a few months´ abstinence. No doubt that will be the last time this season I manage that trick. 😉

Above is a view of the chaos in the shed, just to prove I have a shed! The Carden looks almost small on the 2 meter table. When I took this pic, I was just installing some lights, hence the glare.

2014 is almost history..

Website Comments Off

Dec 232014

..only minor assembly required..

These last few months I have been rather occupied with a different sort of kit, the sort that only requires me minor assembly of a few bricks 😉

Anyway, we are now at the stage where the workshop is closed to the elements, the rest of the house is warm, and only minor items like bathroom, kitchen and doors need to be installed.

Of course a major item to get ready is the whole workshop. (I had a bit of a hard time convincing the contractor I needed 20 odd sockets minimum in the garage) I haven´t even tried to explain the need for vacuum/compressed air and general dust collection, and at least a dozen or so good lights. I´ll show him when it is done.

Sounds of silence

Carden Comments Off

Jul 242014

Finally got a 3 blade prop, because of availability I selected an Elster 26*12. Thanks to the nice sunny weather I was able to do some empty field noise tests. The plane was placed at the center of the field. The air temp was 30C, wind between 2 and 4 m/s. Humidity around 80%. I performed 4 measurements at 25 meter distance, placed at 90 degrees around the plae. Of course it would have been nice to have the plane sitting 1 meter high, but that’s impossible without a lot of effort. Rear of the plane: 68-70 dBA, Front, 80-82 dBA, left and right in line with the prop also 79-82 dB. I only ran to engine to max rpm long enough to get a stable dB reading. RPM readings (per Jeti) were 5760). As with all these measurements, it is very inaccurate, it produces nothing more than a guestimate. (Meter +/- 2 dB, wind, geese you name it..) The only way to really measure is in a ”dead” room, and that’s not going to happen. This is all about getting some kind of feel for ”is it loud or not”. So my average would be between 77-79 dBA. at 25 meter. I feel that this is quite acceptable, when I compare it to some of our small electric models. (mine is quieter!) A single flight was performed, and I can honestly say that many times I could not hear the sound of the engine when flying less then full throttle. From the previous post:

..72 dB at 25 meters in front of the plane, but 84 at 90 degrees, in line with the prop. This is with a Mejzlik 28*10 2 blade, running at 6150 RPM (temp =20C or thereabouts). In the air I see values of almost 7000 RPM,

So in short, switching to a 3 blade cuts down the noise by half (-3 dB) and costs me 400 RPM. Performance wise I think I am ok. I still run the engine on the rich side, it needs further tweeking. (I’m forever tweaking, so what’s new?)

Fun at the Neighbours.

Carden Comments Off

Jun 272014

Our neighbouring club held it´s annual fly-in the other day. It´s a really laid back day where every one does what he likes to do, which is mostly fly..
I took the opportunity to bring along my Carden, just to get it used to ´foreign lands´. The club is really only a few miles away, and they do have a nice field, although it is lined with trees on one side, and a nice big tree on another corner.
For reason only know to my inner self I did not fly there, but enjoyed myself anyway. The next weekend it did become clear why I had this nagging feeling something was NotRight.

This is what was left of the throttle servo, I made a stupid mistake, I left the original choke/throttle contraption on the carb, which resulted in the wrong bits blocking free movement of the carb arm at the wrong time. At least it explains the ´low voltage´ warning I got! Lucky enough the batteries had enough oomph to perform a quick kill! The engine was at idle at the time, so other than a fried servo, no harm was done. Since then I´ve had a few fligths without problems. I also did some sound measurements: Getting 72 dB at 25 meters in front of the plane, but 84 at 90 degrees, in line with the prop. This is with a Mejzlik 28*10 2 blade, running at 6150 RPM (temp =20C or thereabouts). In the air I see values of almost 7000 RPM, and you can hear that for sure. So, waiting for something with 3 blades now, and of course, keep the finger on the throttle!

When Insider meets Stork

Gliders, Insider Comments Off

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!

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