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Author Topic: Stevens Aero Granger Archaeopteryx  (Read 4325 times)
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Hank G B Z
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« Reply #50 on: September 29, 2014, 02:58:33 PM »

Yeah, i know.  Next time i'll bring the slr. 

here are two more pictures.  ONe is of the archaeopteryx before the test flight in the sun.  The other is of all the stevens stuff I brought to the field.  The rign rat is my dads but the fly baby and sky buggy are mine.  The fly baby does the coolest touch and goes and the sky buggy will do almost axial rolls with just rudder elevator. 

Hank

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Konrad
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« Reply #51 on: September 29, 2014, 03:47:58 PM »

Wow, she looks like a giant scale model!  Roll Eyes

Ringrat, isn't that a Control Line model?
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« Reply #52 on: September 29, 2014, 04:33:44 PM »

Konrad,

  Yes the ring rat is a CL model too.  This is an r/c version of the ring rat.  Flies like a r/c version of a control line stunt plane. 

Hank
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Konrad
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« Reply #53 on: September 29, 2014, 04:39:10 PM »

… Flies like a r/c version of a control line stunt plane. 

Hank
Is this code for is not as stable in roll and yaw as one might want?
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Hank G B Z
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« Reply #54 on: September 29, 2014, 05:01:46 PM »

Well, it flies well for being a 4 ch aerobatic plane.  It has no dihedral so yeah not much roll stability.  I haven't noticed any problems in yaw onther than maybe wanting a bigger rudder to do knife edge work.  However it will loop like a c/l model and flies inverted very well since it has a fully symetrical airfoil. 

Hank
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stevensaero
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« Reply #55 on: October 10, 2014, 08:34:29 PM »

Mark suggested that I chime in here regarding the CG.  I've flown the Granger with the CG at various positions from 20% MAC to 30% MAC.  One observation is that rather small changes to the CG produce somewhat larger variations in the elevon neutral set-point.   The prototype models flew quite nice balanced at 25% MAC which I believe became the recommended start point. 

As I lost my personal model due to an unfortunate travel incident I recently snuck the show model out of it's container of peanuts to scratch the itch for an Archaeopteryx flight.  The show model was setup quite nicely just aft of 20% MAC though still forward of 25%, for giggles I dropped the CG aft to 30% which required about 11.5g of 1/8" dia. music wire slung along the bottom of the rudder.  I had to dig into sub-trims as I had used up all of my available down elevon trim making the CG shift without reseting the neutral point.  That said, the model flew quite well and required noticeably less throttle (felt like a click under one half vs. a few clicks over for the forward position) in cruise and exhibited a touch better glide.  I do think the stability of the 20-25% MAC position was welcome but the further aft CG really didn't present a problem.

As I believe was mentioned, it's great fun and quite the head turner at the field.  I take a lot of heat from the engineers at the field (and actually, our local soaring group is full of them) regarding the inefficiency of the abrupt transition to tip-elevon control from the win center section and how this might have been solved in an aerodynamically cleaner fashion… Most are shocked to learn that this is a scale iteration of a full-size craft… and that the tip elevon transition and control was per the scale subject.  This starts even more head scratching followed by a few shout outs from the peanut gallery to the effect of "what the heck is that!", at which point I explain that the model was of British origin, to which they give me a knowing "ah hrmmm" and corresponding nod… then leave me alone to enjoy myself… (I still don't know what the nod means but I have my suspicions)

Here's a few great shots R. Avery took of the Granger in-flight at our last club outing.  I noticed the skid was dis-lodged from the music wire "axle" after returning from the field.  I'll blame that on our "glue monkey" and not make it an inditement of my flying abilities.

He also nabbed some video shorts that I'll try and find a way to clean up and post.

Back to the CG the prototype was balanced with a spot of clay embedded in the tail.  I much prefer a chunk of music wire taped/slung/covered under the rudder… I think you can see in the photos where I had a few of them in place to play with the CG in response to a few of the questions Mark had presented me.  Mid way through this session I lost the HS-35 servo in the rudder, I violently bumped the rudder and from that point on it chattered like mad.  Back at the shop I installed a trusty old HS55 and a new larger diameter (1/32) push-rod.  I ended up dropping my ballast to 5.5g and have maintained a balance just forward of 25% MAC.  I think I like it best here as I can pretty well pull full aft stick and the model will just mush along happily without missing a beat.


-Bill
Stevens AeroModel
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stevensaero
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« Reply #56 on: October 10, 2014, 09:01:07 PM »

I uploaded the raw video shorts from R. Avery to YouTube.  Nothing too exciting… just round the pattern.  I realize that there was quite a headwind when I was flying but something just feels off about the speed.  After landing I realized that I lost the rudder servo and grounded the model.  We obviously need to dig up our footage and put together a jazzy video… maybe something to a Green Day song… then again maybe not Green Day.

https://www.youtube.com/watch?v=RmFeUD5vXI0&feature=youtu.be
https://www.youtube.com/watch?v=EhrGDrZfRxg&feature=youtu.be

-Bill
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Hank G B Z
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« Reply #57 on: October 13, 2014, 11:47:19 AM »

Hi Bill,

  thank you for posting here.  I've been a big fan of your stuff for a long time now.  My concern with the CG came from a friend who also built an archaeopteryx, to get to the 25% of the mac he had to put the battery behind the cockpit, then on his test flight it seemed really tail heavy.  I don't know if he's flown his again or not. 
What p
  Now i balanced mine at 25% of the MAC and i needed full up trim to fly level.  That's a lot of drag. I had to hold at least 75% throttle for cruise and full throttle gives a very shallow climb.  I know this is probably very scale flying.  YOur description of flying at 30% MAC sounds like the kind of performance i'm after. 

  I was hoping to get over to the hobby shop yesterday to order the gears for the hs 35,  that didn't happen, but i hope to get some time in the garage over this week to start taking the model apart to rebuild the tip servo. 

  My skid popped off the carbon fiber "axels" several times during the build so i fixed it by wrapping it with string and soaking with CA. 

A good video on youtube would be nice.  Maybe not Green Day though.  Unless you went with something from the Kerplunk album, but straight skate punk doesn't seem to go with your companies philosophy.  Maybe Mumford and Sons?  British folk seems for fitting to the plane. 

Hank
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Hank G B Z
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« Reply #58 on: December 16, 2014, 07:23:54 PM »

Well after two months of not much happening i finally fixed the granger.  I replaced the one gear that broke in the flip over.  It was the biggest gear in the whole drive train and it only broke one tooth.  These has 35's are odd servos.  they have both corbonite and brass gears and the gear that broke was actually spline drive press fit onto a brass spline that was pressed onto the steel shaft.  Anyway if they break again i'll probably be looking really hard into putting servos in the fuse and driving the tiperons with torque tubes.  I have also installed the pilot and windshield.  If the weather cooperates this weekend hopefully i'll get a few flights in.  We are actually getting rain so i won't complain if I can't fly. 

Enjoy the pics,

Hank
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Hank G B Z
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« Reply #59 on: December 21, 2014, 01:31:22 PM »

Well the flight was canceld yesterday.  I got to the field and was ready to go and I did the control direction it turned out that the servo i "fixed" wasn't working right.  After moving back to neutral It kept moving about a 1/2 inch in what ever the last direction of travel was.  So i think i'll be trowning that servo out.  I'll pick up another servo after christmas. 

stay tuned...

Hank
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Hank G B Z
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« Reply #60 on: September 24, 2018, 05:25:25 PM »

Well it's been almost 4 years but i thought i'd post an update on the Arechaeopteryx.  I don't have any new pictures, i'll post some soon.  I changed out both tip servos to some small eflight ones that fit.  these haven't given the trouble that the HS-35s gave.  I've made several flights on the model and recently.  I've made a few changes.  I broke the scale landing gear fixture so many times that i've decided to delete that detail and just fly with the wire landing gear.  I've also gone to a prop with more pitch 3.5" pitch instead of 3" and i've gone down in battery size from 800 mah to 450 mah.  Losing the drag of the scale gear detail, more prop pitch and less weight with smaller battery has moved the CG back a bit and i've taken out some of the up trim.  The model is flying more reliably now and landings are much easier since i don't run out of elevator during flare now.  It's not exactly a plane I fly every weekend, but it does get attention when I bring it out and it looks great in the air.  I might try moving the CG back a bit more yet just to see if i can get rid of a bit more reflex.  I'll take it out again soon and try to take better inflight pictures. 

Hank
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Konrad
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« Reply #61 on: September 24, 2018, 07:02:14 PM »

Can you tell us more about the E-flite servo? And how much space it there to add another brand of servo? It looks like the wing profile really is limiting the options.
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« Reply #62 on: September 26, 2018, 04:37:35 PM »

Konrad,

   I'll have to take a picture of the servo.  It was one that had a Jst connector on the end and i soldered a standard "JR" type plug on.  It took some re work of both the wing and the servo to make it fit.  It seems to be working just fine.  While looking for some pictures i found these videos of the old girl flying.  IN the first video you can hear me crank up the elevator trim.  Both of these videos are from 2016 and before i added the new prop and lighter battery. 

enjoy

Hank

https://youtu.be/41GHv4qWWFU

https://youtu.be/txdfKRWduVo
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Konrad
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« Reply #63 on: September 26, 2018, 05:44:36 PM »

WOW, looking at those tipperons she looks nose heavy!

It looks like the Stevens Aero prototype only has half the deflection.

Are there any photos of the full size in flight?

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« Reply #64 on: September 26, 2018, 06:37:26 PM »

Konrad,

   Yeah I don't fly with that much deflection these days.  With the smaller batter 450mah instead of 800 the CG is back around 30% mac and I think it could go back a bit more.  There are pictures of the Full size one in flight earlier in this thread.  The reflex is much less due to the fact that the full size one had a semi symmetrical reflexed airfoil and the tips had what looks like a fully symetrical airfoil on the tips.  This makes comparing the model to the full size one difficult.  I thought about adding some clear plastic to the trailing edge to simulate some reflex see if that would help lower the ammount of tip reflex needed. 

  Onward to making more improvements.

Hank
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Konrad
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« Reply #65 on: September 27, 2018, 09:29:59 AM »

Thanks.
It looks like the full size has again half as much deflection as Stevens's  Prototype.
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