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bzfrank's blog
Posted by bzfrank | Mar 25, 2013 @ 12:45 AM | 2,040 Views
I just finished the springtime maintenance on the Cobra and though I post some images. Its based on a Mikado Logo 10 and the AH-1F Cobra fuselage kit from Approach Engineering. Pilot figures by McFarlane Military Series 3 ("Helicopter Chief").





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Posted by bzfrank | Oct 09, 2012 @ 09:32 PM | 2,323 Views
Towing a flag is fun and can be done quite easily. It works exactly like towing a banner but requires less power and can be done by smaller planes (depending on the flag size of course). The following works for me:



Above images my biplane (loosely based on an Udet Flamingo) with 1.80m wingspan towing a 90x60cm flag. Also a 120x90cm one works fine with this setup.

This scheme describes how to attach the flag. It also works for a banner.



For takeoff place the flag flat on the ground, straighten the line and slowly increase speed. It will move to an upright position once in the air automatically.

Attach the line to the tow release, which should be located about 10-20% of the fuselage length behind the GC. Now for the important part: Be sure the line runs below the elevator! In the air the flag is always below the airplane, so the line will otherwise press on your elevator and that can ruin a perfectly good day. Also don't fly too fast, the flag will add quite some drag and will flutter at higher speeds, beside it does not look good.

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Posted by bzfrank | Oct 08, 2012 @ 08:46 PM | 2,749 Views
A while ago I built a Windrider/HK Mig-3. A wonderful bird to look at but it turned out to be a beast in the air. When flying at lower speeds it did just fall out of the air - tip stall without any warning, its name was Mig-3.



After some crashes and rebuilds I gave the Mig-3 to a colleague and forgot about it.

Well, almost - when I stumbled over a HK Mig-3 on eBay I know I had to try again and this time make it fly, and fly well.

Isolate the issue

The Migs tip stall issue comes from several causes.



One is the wing geometry, a wide wing in the center and quite small tips. While scale in appearance (and true to it - the original Mig had quite unpleasant stall characteristics) its always cause for alarm. Its problem is that on such a wing the tip tend to stall before the root. Several things can be done to prevent this from happening:

- reshape the wing - gives good results as the VQ Mig-3 shows but impossible to change later for an ARF bird (and besides it does not look scale anymore!)

- geometric twist, decrease incidence of the outboard leading edge by some degree - usuall works fine but also impossible to change later as well. The Mig-3 has no such increased incidence at the tips.

What is possible later is to raise both of the ailerons a few degrees. This reduces lift but also the tendency for a stall however only slightly.

- different airfoils tip / root. Likewise impossible to change for a ready-made plane.

Well, that leaves one more thing: Tubulators

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Posted by bzfrank | Apr 06, 2012 @ 11:51 AM | 3,515 Views
This is an old model I have restored over the winter, a "Pelikan" designed by Robert Schweissgut, Austria.
Composite fuselage, 3.7m wingspan, 500W HCS Roton brushless motor and 15x7 folding prop:





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Posted by bzfrank | Apr 04, 2012 @ 10:12 AM | 2,470 Views
I recently got a key cam #16 for areal photography. While this tiny camera can be just attached by a strip of velcro, I thought a real camera mount makes it look nicer and will produce better movies due to better decoupling from vibrations and optimized camera angle. (And I was right! ) Made from carbon fiber with a total weight of 28g (incl. the camera):



The smaller one is the counter weight for the other wing.



Key cam #16 In-flight clip (6 min 56 sec)

Posted by bzfrank | Mar 15, 2012 @ 05:38 PM | 2,553 Views
Big wheels look really good on a Cub:





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Posted by bzfrank | Feb 29, 2012 @ 01:51 AM | 2,544 Views
Got this plane in a very damaged state. The aft section of the fuselage was completely broken. After a few weeks rebuilding the fuselage, elevator and rudder its back in full glory. Also added a towing release and magnet locks for the side door. Recently also changed the wheels to 6" bushwheels but thats not yet in the pictures.

2.05m wingspan, 3800g AUW, flies great.




Posted by bzfrank | Feb 29, 2012 @ 01:44 AM | 2,673 Views
Finally finished this baby. Full composite Spirfire Mk. IX by Jim Fox (Fox Composites), 1.4m wing span and 2800g AUW, scale pilot and cockpit and electrical retracts:





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Posted by bzfrank | Feb 29, 2012 @ 01:38 AM | 2,128 Views


It can also turn:



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Posted by bzfrank | Apr 08, 2010 @ 04:50 PM | 3,523 Views
My Grumania SU-27 EDF Jet is slowly but surely getting ready. Fully glass fiber / carbon fiber and scale painted.

Length 1400mm (55.1 inch), wingspan 1000mm (39.7 inch), AUW 3500g (123 oz), 2 x HET 6904 2w25 will drive the bird fed from a 5000mAh 6S 40C lipo battery.
Posted by bzfrank | Apr 08, 2010 @ 04:34 PM | 4,336 Views
A few weeks ago I finished the build and maidened the Cooler autogyro this week.

I always was a fan of autogyros, ever since I saw 'You only live twice' as a child on TV, where James Bond flys the 'Little Nellie'. An autogryo flies a lot like a normal airplane, but as the rotor is not powered and only driven by the airflow the pilots job is to make sure it never stops rotating. As a bonus you cannot stall an autogyro and in a light wind it can do 'on-the-spot' landings.

The Cooler is normally made using a PET bottle. I choose to cover the fuselage with balsa and paper instead and add some scale looking touches.

Link to the video, rough grass demanded a punch-up start:

http://www.wizards.de/~frank/images/...irst_Start.avi

The Cooler is driven by a Turnigy AerodriveXP SK 3536 910Kv / 310W with Turnigy 40A ESC @ 3S2500 mAh / 25C. 3 x Hitec 5645 servos for the rotor and the rudder.