Ultimate 10-300

One day over a cup of coffee Paul (he of totally unsuitable indoor models) suggested that a scaled down version of my original Ultimate 10-300 would be a superb purpose built indoor model. Also I had recently received a new motor from Robotbirds in the shape of the 18mm diameter Baby out runner C18-15-17 weighing a massive 13 grams it was simply calling out for a sub 6 ounce model to test it in.
My original Ultimate model was my first shocky/foamy type model and served me well for a couple of seasons, it took a few attempts to get the power train right but when I did it proved a great introduction to the 3D foamy world of very light models with very high power to weight ratios

.The original model was built from a downloaded plan from the Foamy Factory in the US. Their plans are designed to be printed out on A4 sheets of paper, which you then tape together to make templates.

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Construction was from 6mm Depron with 6 mm carbon tube down the centre of the fuselage. Wings 30” span again 6mm Depron with 10mm wide thin carbon for stiffening.  Sadly I only painted part of the wing (with the wrong paint) and the foam eventually deteriorated with the action of UV light, the model was scrapped in early 2006.

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An idea of size.

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So Christmas eve I brought out the original templates and set about making scaled down versions, I went for a 75% size to give a 22.5” wingspan. Construction is from 3mm Depron sheet (half a sheet to be exact) with 3mm carbon fibre strip wing spars and strut members.
 For the fuselage I used the well-tried and tested cruciform layout with a balsa triangle stiffening the fuselage.

 Tail surfaces were just scaled down again in 3mm Depron. All fixtures and fittings are from an Over-tec (was Overlander) shocky accessory pack plus some 1.5/2mm carbon rod for pushrods and landing gear.

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Ready for flight.

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Majority of the radio bits

 At this point I needed the original drawings to show the strut locations on the wing, I couldn’t find it, so a quick visit to the Foamy Factory web site and there what do I find but a scaled down 23” version of the original available as a free download! 

The servos are 4 X Saturn 44’s, these are quite expensive compared to some on the market, but they are a genuine 4.4 grams each, have very consistent centring which is very important in small models plus they keep working unlike some cheaper micro servos. Spare gears are available but fitting them can reduce a grown man to tears (I was that man). 

I used a servo for each aileron as I have always used this on my shockies for three reasons. One; it makes the ailerons easier to set up as the geometry is far better plus one can centre each and set travel adjust at the transmitter. Two, better load distribution, especially with four ailerons. Three, it keeps the cut outs in the fuselage to minimum (just a small rounded hole for the servo leads). My first shockies were from Icarus Kits but I found these a bit weak with the fuselage and wing having to many cut outs for radio gear and battery pack.  

The receiver is a Hitec HFS-05MS 5 channel, weighing in at 8 grams it is the best micro Rx around in my opinion. Although 5 channels, channel 5 is in fact the channel 6 output (second aileron for aircraft or collective pitch for helicopters) when used with most makes of TX. Thus it is perfect for use in small models with dual ailerons, it uses standard Hitec or Futaba crystals and at only 17.00 it has to be the “dogs xxxxxxxx” of micro RX’s. Disadvantage, very hard to get hold off, most shops and web sites have them as “sold out” possibly because when the do become available people buy several at a time. 

Motor is as stated a Baby out runner C18-15-17 this is the smallest of a new range being sold by Robotbirds. Propeller is a GWS 6 X 3 lightweight plastic. A Castle Creations Phoenix 10 speed controller drives the motor from a FlightPower EVO 20 300 ma/hr 2 cell Lipo battery. 

The top surfaces were sprayed in blue and red RC Styro Colours acrylic paint. These paints special formulated for Styrofoam & ABS cover well and seem to offer protection against UV deterioration of Depron. Final all up weight came in at 140 grams just over 4.5 ounces.

  First flight was straight of the floor, model flies superbly, like all biplanes the power has to be kept on though out the flight or drag just takes over. At 22.5 inches it make the hall look very large and is a lot more relaxed to fly indoors than other models. 

Come along and see it fly.

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The other radio bits

The soft underbelly.

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The test flight

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