Greg Covey

Hi,

I converting the World Models Ultimate 40S Biplane ARF from [link=http://www.airborne-models.com/html/productdetails.asp?ProductID=84]Airborne Models[/link] to clean and quiet electric power. The bipe comes in two color schemes and has the following specifications and key features.

Specifications:
Wing Span: 42.0 in / 1060 mm
Wing Area: 578 sq in / 37.3 sq dm
Flying Weight: 4.5lbs / 2025 g
Fuselage Length: 39.5 in / 1000 mm
Engine Required: 2C 0.40 cu in / 4C 0.48 cu in
Radio Required: 4 channels, 4 servos

Key Features:[ul][*] Top quality balsa and plywood construction[*] Light weight but strong for aerobatics maneuvers[*] Hand painted fiber glass cowling and wheel pants[*] Built-up wings with symmetrical airfoil[*] All necessary hardware included
[/ul]

Greg Covey

The ARF Bipe comes very well protected in its box and every part is sealed in plastic. The plane is beautifully covered and detailed. The fiberglass cowl is painted and comes with a plastic guide for cutting sections away when a glow engine is used. All wheels, fiberglass pants, and a pre-painted pilot figure are also included.

Greg Covey

A quick peek at a page from the manual reveals detailed linkage assembly and instructions to properly set incidences along with a wing guide set for checking the alignment between the two wings.

Another page clearly states the proper throws and CG settings

Greg Covey

A few closeups of the fuselage show the solid but light contruction techniques. The firewall has pre-mounted T-nuts that I'll move to position the electric motor mount.

Greg Covey

For the lower wing servo, the Hobbico [link=http://www2.towerhobbies.com/cgi-bin/wti0001p?&I=LXPB33&P=7]CS-35[/link] Mini BB Servo was a perfect fit. All the linkage was supplied including the keepers.

The ailerons are glued to the wing by soaking the fiber hinges with thin CA.

glover1482

I'm interested in doing this also. It's been a while since your last post, so how is your project coming? I've send the vendor a note asking them for the differences (other than covering) between the 40S and the 30 versions of their Ultimate. I'm also considering the Dave Patrick version of this toy for $50 more.

Glover

wollins

Yeah Greg ... what's the latest ... I've been looking to get this one to convert as well. Since you're the "conversion guru" we're waiting on the progression and conclusion of this thread! Don't keep us in suspence!

Greg Covey

Hi guys,

Sorry for the delay in updates on this thread. I've been traveling for FMA and would say that work keeps getting in the way of my R/C, but that would not be accurate, since R/C is my work now.

I hope to work on my bipe this weekend, so I'll post some updates along with my selected power system and mount.

glover1482

Perfect! I ordered mine last night. But I'm still looking for an Aveox 27/39/2 to shove up its nose.

Lots of lift, Glover

Greg Covey

I typically jump out of the manual's building sequence to my favorite part of power system design and motor mounting. The power level on a high-performance biplane like the Ultimate must be able to overcome the large drag of having so much combined wingspan and provide awesome aerobatics. To achieve this, I recommend using a 150w/lb to 200w/lb power system. Assuming an all up weight of 5lbs, this puts us in the 1000w motor class.

I had originally wanted to use an AXI 4130 motor with a 6s Lithium pack but did not have one available. What I did have available in the 1000 watt motor class was my Kontronik 600 geared motor. I have used this successfully in 9-10lb conversions like the Great Planes Lancair ES and Lil Toni Pylon racer. My Lil Toni Cosmic Wind racer has recently undergone a 2000w power system upgrade so my 1000w Kontronik power system was available and a perfect choice for my World Models Ultimate 40S Bipe.
[link=http://www2.towerhobbies.com/cgi-bin/WTI0096p?&N=P&C=&S=0000000&P=7&F=KONM4060&L=KONM3130&S1=KONTRONIK&S2=&S3=&S4=]Kontronik at Tower Hobbies[/link]

My motor is from the Kontronik Brushless 600 set which uses a Kontronik Fun 600-18 motor, KPG27 Gear Drive with 4.2:1 ratio, and a Jazz 55-10-32 Speed Control. Since I had problems with the Jazz 55 ESC over-current cutoff tripping way too early, at about 800 watts, I do not use this controller.

I ordered the Type 8 front and back plates from [link=http://www.espritmodel.com/]Esprit Model[/link]. Instead of using the expensive extension rods and spacers from Esprit, I connected my plates using four standard #8 standoffs (7/8" long) and #8-32 hardware from Home Depot. The Kontronik 600 gearbox connects to the front mounting plate using four M3 screws about 10mm long.

Greg Covey

My experience with using the Phoenix HV 85 ESC on my power system upgrade for the Great Planes Lil Toni racer made me want to try the Phoenix HV 45 ESC for this project. The [link=http://www.castlecreations.com/]Castle Creations[/link] Phoenix HV 45 ESC can handle up to 2250 watts (or 3 h.p) of power using 45amps continuous current draw.

The lack of arcing when you connect the battery and the unmatched smooth throttle control put the new Phoenix HV ESCs in a class by themselves. It is a great value at $136 from [link=http://www2.towerhobbies.com/cgi-bin/wti0001p?&I=LXLBY3&P=7]Tower Hobbies[/link].

Greg Covey

Mounting the motor assembly was as easy as moving the four stock T-nuts in the firewall. Since the top T-nuts were close to the upper wall, I used a Dremel tool to flatten them on one side for easier mounting.

The motor assembly mounted using the stock hardware. I used a [link=http://www.hobby-lobby.com/propadap.htm]MJ4705[/link] collet prop adapter for 5mm shaft from Hobby Lobby. Alternatively, you could also use the Great Planes [link=http://www2.towerhobbies.com/cgi-bin/wti0001p?&I=LXUA39&P=M]5mm Prop Drive[/link].

Greg Covey

Although the manual recommends a distance of 4-1/2" from the firewall to the spinner backplate, this provides what most people would consider an excessive gap.

My motor mount provided a perfect 4-3/8" distance and a perfect gap for the supplied spinner.

Greg Covey

The wing strut supports were installed with white glue after first cutting away the two slots in each wing.

Greg Covey

The tail cutouts were supported by two balsa wedges. The elevator was installed first using thin CA drops as before.

I used thick white glue (that dries clear) to install the stabilizers. The Aileen's Origial Tacky Glue won't yellow over time like 5-minute epoxy does. A thin plastic wedge was needed to correct the horizontal stab incidence.

Greg Covey

The stock spinner fit nicely with an APC 14x10 e-prop. This size will make a good starting point for my power testing based upon previous experience with the Kontronik 600 brushless motor on a 6s Lithium voltage. I may change the pitch to a 14x7 depending upon the testing results.

The cowl is held by the 4 stock screws and rubber grommets to keep the paint from chipping.

My Ultimate 40S bipe starts to take shape.

Greg Covey

I was very happy with the linkage assembly because most of the work was already done for you. The control rod tubing is pre-installed and the little bags of parts are numbered to match the step in the manual. Pin holes were already drilled into position for the control horns so I simply opened them a bit larger with a drill bit.

The control horn screws fit nicely into the anchors on the other side. Everything seemed to fit perfectly!

Greg Covey

The tailwheel assembly came in its own bag and installed easily. The rudder bottom needs to be drilled and a channel cut for the control bar of the tailwheel. I roughed up the control bar with sandpaper and epoxied the assembly in place. The black plastic base is secured to the fuselage bottom with two screws.

Remember to add some Locktite to the set screws before you tighten them.

Greg Covey

When installing the gear mains, I needed to drill two holes where the cowl covered the t-nut openings in the covering. The wheel and pant assembly installed without issue. I could now stand my Ultimate 40S Bipe on its own three wheels.

wollins

Looks like its going really smoothly Greg! Question: What's the typical/optimum wing loading for a aerobatic model biplane? Is there such a thing as "scale" wing loading? Reason I ask is that I have a Aeronauth Models M-12 Pitts ... a wee little thing at 33" ws and 30" length and its a great flyer but lands real hot! Its wing loading is about 14.73ozs per sq foot which I thought was reasonable? So whats up with the hot landings?

Colin.

algutkin

My Feedback: (1)

Greg:

How did you do all that work, and there are hardly any tools on the table? The project looks really good so far.

Al

Greg Covey

Colin,

The Pitts and Ultimate designs are known as "Muscle Bipes" because of their extreme aerobatic capability. They fly fast and land hot. The smaller ones like your 33" span model are the most difficult to handle. In recent years, due to lighter construction techniques, the 40" span and up bipes have become less of a handful to fly and land. Only intermediate flying skills are needed to handle these bipes as they are designed to fly very well and land slower with some power required until touchdown. The key to a good flying aerobatic bipe is to have proper incidences. The World Models ARF design and incidence guides make the task a whole lot easier.

Al,

These new ARF designs are easy to assemble and just make me look neat.

ropowell

Hi,

Just a note of warning. I just flew this aircraft with a four stroke 52 for the first time and had a problem with the CG location given in the instructions. The published CG is at 36% of mean aerodynamic chord and the aircraft was unmanageable. If interested in details, let me know

Dick

Greg Covey

Hi Dick,

If your 36% corresponds to the 3-3/4" back from the top wing LE center line, as per the manual, then lets hear what went wrong.

Biplanes can get squirrelly if the CG is too far aft or if the incidences are wrong. It sounds like we should start out with a CG forward of the manufacturer's recommendation.

ropowell

Hi Greg,

Here are the details of the CG problem. I'll go step by step so you can check my measurements and calculations. The effective chord of a biplane is the projected chord that you would see looking down on the wings. For this biplane, this may be found by taking the chord of the lower wing and adding the stagger between the two wings. I measured the chord as 6 7/8 inch and the stagger as 1 inch so this gives me an effective chord of 7 7/8 inches. Since the two wings are fully equal, and of constant chord (even though there is a sweep of 1 3/4 inches) the mean aerodynamic chord (MAC) is also 7 7/8 inches and it is located exactly half way out the wing panel. The suggested CG point would be 25% of the MAC or 1.97 inches back from the leading edge of the wing AT THE LOCATION OF THE MAC which is 10 1/2 inches out from the center of the fuselage. I called this 2 inches for convenience and now it must be projected over to the CL of the fuselage. So to get the CG location at the CL, we must add half of the sweep or 1.75/2 = 7/8 inch added to the 2 inch which gives 2 7/8 inches for the CG measurement at the CL of the fuselage. This is the measurement I plan to use when I rebuild, not the 3 3/4 given in the documentation. I can't help but wonder if the engineer at World models just forgot to divide the sweep by two and got 2 plus 1 3/4 equals 3 3/4 inches. OK, he worked in millimeters and got 3.74 inches without rounding off! I do know that no engineer would assume the MAC occurs at the wingtip so he wouldn't add the full sweep!

Just for some extra information, I really fell in love with this little bipe even though my entire flight felt like I was walking a tightrope. I had a 4 stroke 52 engine with a 11x8 wooden prop and the AC really liked the power and airspeed that this gave at about 1/2 to 3/4 throttle. If I slowed a bit, it would try to drop a wing but I now know why. My final problem came when I pulled up into half a loop and then pushed nose up -- planning to fly out inverted and half roll to normal -- but no, when I pushed the nose up, I snapped into an inverted spin. I neutralized the controls but forgot to chop the throttle (pilot error!!) and the little bipe recovered to a straight down line after maybe two turns. I started to pull some up elevator to recover and the AC snapped into a positive spin. I again neutralized the controls but this time, no effect!! I spun another three or four turns into the ground doing nothing. I never chopped the throttle and I think that may have helped the spin -- but who knows?

I hope this helps and if you have questions I'll try to answer.

Best wishes, Dick