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Old Jan 13, 2011, 03:33 PM
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mikmerl's Avatar
Athens, Greece
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Build Log
TOPMODEL CZ GRAFAS glider

I just purchased a TOPMODEL CZ 3070mm wingspan GRAFAS full house glider from MODELLBAU BICHLER in Germany .
Opening the stout box revealed a very well thought out packaging layout with each component in its own nylon bag and each of these were tac glued to the interior of the box to prevent the parts from “bashing” each other during transport.

Further examination led to even more grinning on my behalf.
The build quality is excellent and I am anxious to start the assembly so that I can get that beautiful translucent wing high up in a thermal.
The 3 piece wing, stabilizers and rudder are expertly (wrinkle free) covered in ORACOVER and the white gel coated fuselage is simply perfect. Also a very comprehensive accessories package is included.

I have not yet decided on the motor/prop and battery combination but there is ample room for just about anything in the nose (within reason). I will trial fit the glider together (with servos etc) to see how much weight will be need up front for balancing. Then I will decide which motor/battery according to that weight.

mike
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Old Jan 25, 2011, 01:04 AM
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Athens, Greece
Joined Apr 2010
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Decided that an AXI 2826/12 brushless outrunner with a Aeronaut 15x6 folding prop should get this glider to altitude very briskly.

As the nose ring is narrow I flipped the motor using the AXI prop adapter and a new custom made firewall. This way the wires exit the motor further aft where the fuselage widens and the wires fit easily.

See my past thread on how to make a new firewall for such an installation.
http://www.rcgroups.com/forums/showthread.php?t=1264158

An added advantage to this mounting method is enhanced cooling to the motor. Adequate cooling holes must be cut into the firewall to allow incoming air to flow through the fuselage to cool the ESC and battery as well.

mike
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Old Jan 25, 2011, 02:49 PM
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Valdosta, GA
Joined May 2006
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I just wanted you to know that I am following your thread with interest. Not only have I thought about buying this plane, I even have an unused Axi 2826/12 at home.
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Old Jan 31, 2011, 02:04 AM
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Athens, Greece
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Now for my least favorite part.

Soldering the wiring to servos and plugs.

This step is time consuming and requires meticulous attention for long life (the models).

Make sure that there are no cold solder joints and map all your pin designations on a piece of paper for future reference.

Moosey-UK (aka Mike) has done a great job of describing this wiring project in his AVIA build thread http://www.rcgroups.com/forums/showt...1123536&page=6

I am using Hitec HS-125MG wing servos for the ailerons, Volz Maxx servos for flaps (I just happened to have them but Hitec HS-82MG would work great) and Hitec HS-82MG for the rudder and elevator controls.

The use of plugs for the outboard panels is necessary in order to be able to disassemble the wing for transport and storage. The 9 pin plugs allow all of the wing servos to be plugged into the receiver very easily and most importantly without the possibility of plugging servos into the wrong channels.
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Old Jan 31, 2011, 04:50 AM
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Chipping Norton, UK
Joined Jul 2006
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Hi Mike,

Nice model, looks like it should fly well.

Out of curiosity why use the 6 pin multiplex plug and socket rather than a normal 3 pin servo plug and socket for the aileron servos?

Graham
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Old Feb 01, 2011, 08:30 AM
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Graham I had decided to do something completely alien to me and that is to follow the instructions.
The end ribs of the wing panels have slots milled into them to accommodate MPX plugs which are also called for in the assembly manual. (see attachment)
When I was rummaging through my wiring odds and ends box just before I started soldering I came up with a pair of MPX to J type servo plugs that I had made for my Dragonfly Strong but they were too short (I had to send a trained hamster into the fuselage to get to the receiver). However these turned out to be perfect for the GRAFAS glider so I decided at the last moment to simply solder the adjacent MPX plugs to the wing servo ends as well and use them as seen in attached photo. One plug is for the aileron servos and the other is for the flap servos. (and yes I did simply use servo plugs for the outer wing panel aileron servo connectors after all) (see attachment)
I had already deviated from the manual anyway by modifying the firewall to accommodate a larger outrunner motor.
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Old Feb 01, 2011, 08:37 AM
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Also following. Waiting for flight reports actually. I have her little sister Avia and have been flying her for over a year and am very happy with her.
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Old Feb 01, 2011, 08:42 AM
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leadchucker you can imagine how anxious I am to get to that stage as well
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Old Feb 02, 2011, 01:03 AM
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I received my Grafas yesterday (purchased directly from Topmodel cz), so I'm anxious too. How much you put down draft to the motor and did you put any to the right?
Where is the cooling air inlet of the AXI motor installation? The slit between hull and spinner looks very norrow in the picture.
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Old Feb 02, 2011, 07:43 AM
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Quote:
Originally Posted by Manu59 View Post
I received my Grafas yesterday (purchased directly from Topmodel cz), so I'm anxious too. How much you put down draft to the motor and did you put any to the right?
Where is the cooling air inlet of the AXI motor installation? The slit between hull and spinner looks very norrow in the picture.
I put no down thrust nor right thrust on my Avia and it flys fine. Any fight path tendancies under power are easily corrected with the controls. Also I made no provsions for cooling as it really isn't needed. With the climb rate the motor only runs about 20 seconds before I'm at 200 metres altitude.
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Old Feb 02, 2011, 12:54 PM
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Athens, Greece
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Manu I have ordered a hollow nose spinner which has not yet arrived. I will rely on whatever air enters through there for cooling. I agree with Leadchucker the climb out is very brisk with these motors 15 to 20 seconds and you are at the desired height. I do not believe that there is any significant heat buildup in such a short run.
As for the down and right thrust I rely on the fuselage nose ring and carefully align the firewall/motor so that I have a good close constant gap between the fuselage and the spinner. That way you get whatever the manufacturer has built into the design.
If needed I simply compensate for any climb/tendencies the glider exhibits under power from the transmitter.


mike
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Old Feb 02, 2011, 01:45 PM
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I did a bit more work on the fuselage as follows.

Marked the required diameter for the hole on the starboard side of the vertical fin for the elevator servo. (the firewall in the kit is good for that)

Cut out and dressed the hole to a diameter of 43mm as specified in the manual. Do not cut all the way to the molded circle but allow a lip of around 3-4mm for the white adhesive cover.

Cut two slots 3mm wide low down of both sides of the fin for the rudder pull/pull cable exit guides. (visible in photos)

Checked fit of the elevator bellcrank in the preinstalled wooden bushings inside the vertical fin. The fit was way too tight and required a little “reaming” with a rolled up piece of wet and dry sandpaper passed through the bushings and gently twirled. Do this gently and check the fit often until you get a free rotation without any slop.

Readied the preinstalled elevator servo wiring for soldering to the servo.

Soldered the connections on both ends towards the servo and towards the receiver.

mike
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Old Feb 02, 2011, 04:32 PM
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Chipping Norton, UK
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Quote:
Originally Posted by mikmerl View Post
Graham I had decided to do something completely alien to me and that is to follow the instructions.
The end ribs of the wing panels have slots milled into them to accommodate MPX plugs which are also called for in the assembly manual. (see attachment)
When I was rummaging through my wiring odds and ends box just before I started soldering I came up with a pair of MPX to J type servo plugs that I had made for my Dragonfly Strong but they were too short (I had to send a trained hamster into the fuselage to get to the receiver). However these turned out to be perfect for the GRAFAS glider so I decided at the last moment to simply solder the adjacent MPX plugs to the wing servo ends as well and use them as seen in attached photo. One plug is for the aileron servos and the other is for the flap servos. (and yes I did simply use servo plugs for the outer wing panel aileron servo connectors after all) (see attachment)
I had already deviated from the manual anyway by modifying the firewall to accommodate a larger outrunner motor.
Instructions, a nice touch often ignored by manufacturers, its no wonder youu were nearly led astray. I presume your Xplorers came without instructions?
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Old Feb 03, 2011, 12:58 AM
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There was not even a “Congratulations on your purchase” or “this is not a toy” note in the boxes.

Obviously these models are intended for builders with a few simpler projects as prior experience.

They arrived in two very well protected boxes one for the two fuselages and the other for the wing panels and stabs.

I don’t even know where the CG range is.

mike
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Old Feb 03, 2011, 02:17 PM
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Chipping Norton, UK
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They really could put a few details like c of g and surface movements in just for piece of mind for the first launch, still I suppose since you got a spare it dosn't matter too much

But seriously you are gonna have trouble choosing which toy to take out.
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