I modeled my Houston Hawk in X-Plane tonight. Here is the file if you wish to download it.

http://wkleinsasser.net/download/Hou...awk_Xplane.zip

For fun, I modeled the Vivace 100" plane today in X-Plane. The airfoil is not accurate, but close enough for the model to fly. All controls are modeled (no motor) and winch launching in X-Plane is interesting--quickly the plane is too small to fly. Pretty realistic, maybe.

As with my non-virtual first flights, the CG location and airspeed make all the difference. Using the virtual plane, I was able to practice the CG dive test and really get a feel for how decalage and CG relate. I was also able to better understand the idea of using inverted flight to test CG location. I'm not sure these are really true-to-life but X-Plane is pretty sophisticated so it seemed to model flight characteristics pretty well.

The 7º outer panel dihedral as modeled seemed a good compromise. With enough airspeed, the plane was solidly stable and held turns well. I was able to model mixing rudder to the aileron control and find when spiraling occurred in thermal turns (quickly when mixed in). I was also able to play with flap-elevator mixing for level flight transitions. Again, I don't think these will transfer to real model trim and mix, but it was interesting to play with it.

If anyone is interested, here is the X-plane aircraft file. [UPDATED 5-12-13]

http://wkleinsasser.net/download/Viv...ane_glider.zip

If you are interested you can download a free demo of X-Plane and take the plane up on the winch launch.

http://www.x-plane.com/downloads/x-plane_10_demo/

Now I need to find wind tunnel data for the AG35 airfoil to import its likeness into the X-Plane model.

UPDATE: I have entered the Reynolds number, thickness percent, lift coefficient and drag coefficient for AG35 into the wing's airfoil definitions in X-Plane. I don't notice any real difference.

Today I received the box of laser cut parts and wood from National Balsa to build the larger 126" wing for the Vivace. The plan is in a post on April 26th below. This wing will increase area and also increase the percentage of chord allocated to the flaps and ailerons.

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I took out the electric Vivace this evening for her first flight. Decades ago I used to fly power 4-ch pattern and sport planes, including a biplane so I was pretty ready for the aileron, rudder, elevator part and the flaps seemed a pretty easy thing to take on. Well, the plane was harder to fly than I expected. It was breezy (8-10 mph) and with the rather conservative control throws on the ailerons (including differential), I found that the plane would not turn well without a lot of rudder and then tip stalls were always close by (darn those pretty pointed wing tips!). I was able to climb and I was able to glide and turn a bit but the whole time it felt only partly under control. The landings (2) were fast and steep.

I have some thinking to do to sort out what was trim (I didn't really even have time to attend to this in flight due to the stability issues), what was CG (this seemed OK), and what was design (I have already modified the wing drawings for next time to increase the chord percentage of the flaps and ailerons from this original), and what was pilot error (this plane needs more air speed than I expected). More soon as I progress.

I also need to rethink the dual battery approach. The small 3S 65C 350 mAh LiPo for the motor, even fully charged, was cutting out on the climb so I think I need to find the room for the larger 500 or 850 mAh LiPo and run one battery.

UPDATE: I have had some time to remember and reflect on this and I think that I was flying...Continue Reading

I have been fooling around with wing options for the Vivace. Here are pdf drawings of a 126" version and a clipped-wing 100" version with a higher wing area than the original elliptical wing.

126" wing
pdf: http://wkleinsasser.net/download/Vivace_126.pdf

100" clipped-wing
pdf: http://wkleinsasser.net/download/Viv...ipped_wing.pdf

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Twelve Months, Four Planes Built

Because of the six servos, while it may not be necessary, I decided to go with separate power and radio batteries for the Vivace so I could use a small high-C 3S LiPo (52mm long 3S 65C 350 mAh) to power the EMP 3536 outrunner motor and not worry about charge to run the radio. The calculations show this should give about 1 1/2 minutes WOT running time. The UBEC outputs 3A and is powered by a very small 2S 350 mAh 20C LiPo. I also plan to try a slightly larger 55mm long 3S 45C 850 mAh LiPo for power (giving about 3 minutes total WOT) and maybe also for the radio without UBEC if it will fit the tight confines of the pod. The smaller 350 mAh power battery, 36A ESC, UBEC, radio battery, and 7-ch Spectrum Rx with satellite, and wiring all fit snugly behind the motor separation bulkhead and forward of F2, which is just at the wing LE.

Vivace - 100" Elliptical wing glider/eglider prototype design:

Influenced by Dr. Mark Drela's Allegro Lite design with high aspect ratio elliptical flying surfaces. Vivace (lively) is a musical modifier of Allegro (as in Allegro Vivace - fast and lively).

Updated 3-30-13

Modified April 7, 2013 -- larger wing control surfaces, corrected shear web dimensions, and redrawn wing ribs.

Modified May 5, 2013 -- edited the wooden fuselage design for longer nose moment.

Modified May 12, 2013 -- Moved indicated CG

Modified May 18, 2013 -- Straightened center section spar so that no angled joint is needed at the center of the CF spar caps.

pdf: http://wkleinsasser.net/download/Vivace-100_Elliptical_glider.pdf

Drawing files and part cut sheets:
http://wkleinsasser.net/download/Viv...Elliptical.zip

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126" larger wing option

pdf: http://wkleinsasser.net/download/Vivace_126.pdf

100" larger area clipped-wing option

pdf: http://wkleinsasser.net/download/Viv...ipped_wing.pdf

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If you have an Allegro Lite and just want to try out the Vivace wing with it,
here is a modification I have drawn that should mount directly on an Allegro
Lite fuselage (the bolt-beam mounting holes should align). I'm not certain that
the Allegro Lite fuselage has room for the wiring from the four-servo wing,
though.

pdf:
http://wkleinsasser.net/download/Viv...e_fuselage.pdf

Drawing file with parts cut sheets:
http://wkleinsasser.net/download/Viv...e_fuselage.zip

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As...Continue Reading

I have posted several design ideas for wooden fuselages to fit Jack Womack's Houston Hawk, Yardbird, and Bantam wings and tails. These fuselages are not official parts for the Houston Hawk, Yardbird, or Bantam and planes built with them need to be understood to be modifications and not true planes bearing Jack Womack's design names. They are just drawn up as options that can work as wooden versions for those wings and tail sets.

Here they all are. The revision date is listed on each plan. I have not built and tested some of these yet (I hope to soon) and I am not an engineer, just a modeler, so these are use at own risk drawings. There are photos at the bottom of the ones I have built.

Before printing be careful that the printer results with 100% scale at the bottom right of each drawing to confirm that you get 1:1 (1 inch on drawing equals one inch on printed page).

** My suggestion is that before printing, have the person doing the printing double check that the scale will be correct for their file+printer. Sometimes printers shrink or expand the drawing when printing. I have received a report of the Yardbird fuselage pdf printing at a result that was 68% of full scale. This may have been because I had too much on one page for the drawings so I have split the large drawings into two sheets, one that is the plan and the other that shows the profile and dimensions.

If reduction persists with these new files, I believe that you might be able to avoid that by...Continue Reading