Roy's RC Hobbies

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1/8 Scale Martin Baker MB5

This was a project that was along time in the making.  I'd started dreaming about building a model way back when I was a school boy, but to do it properly it needed a motor that could drive contra rotating propellers. so that's as far as it got, just a dream until late in 1999 when electric flight was starting to show promise as the next big thing in radio controlled model flight.  

The main man behind this was my old club mate Dave Chinnery with his Team Gear Units. A simple set-up of multiple brushed can electric motors driving one shaft. Or in the case of the contra rotating motors two shafts.

Buy the year 2000 Dave had successfully built and flown models of the Boeing XF8b and the Bristol Brabazon, so proving the concept. 

It was another 2 years before I had a workable brushed motor unit of my own, the TCM1. Using two colbolt motor and a boat prop shaft. It could spin two 14" props off 16 Ni-cad cells at a 1000 watts input power. 

I started to build the model of the MB5 in 2002. My original plan was to design it from the ground up, but then I came across a set of American plans by Bob Holman of an 1/8 scale IC powered MB5. However after buying a copy of the plan I was a little disappointed with the lack of detail & some of the liberty he had take with the  design.

Starting again, this time using Bob's general layout I redesigns the plans for electric power. The fuselage profile was corrected and I did away with much of the balsa planking shown. The engine firewall was moved back to cope with the longer motor assy. The wings were also modified back to the real original slimmer airfoil of RAF34.  

Not being the fastest of builders, it was to take me until 2005 before the model was anywhere near ready for the first flight. It eventually came to a point were I needed to know if all the work was worth it, and if there was any point caring on with the project.

So on a dull afternoon in October 2005, I charged her 16 cell NiCad pack & took my 13Lbs monster to the flying field. I was hoping that I would have the place to myself, Just in case the worst happened! As it was, as soon as I was ready for the big off one of my club mate arrived. So no turning back now, and somebody to record the momentous moment.

Much to my relief she did indeed fly, after a long run up she was airborne. Not the fastest, or with the greatest rate of clime but airborne, and rock steady. All the controls were fine with little in the way of trim needed, & the retracts work perfectly.

 

After 3 circuits or so, I decided not to push my luck & go for a landing. Having proved all that I needed to, I was grinning from ear to ear. The only down side to the flight was my less than perfect touch down, on the very weak and spindly undercarriage leg's, ended with the model sat on her nose. But I dint care, she flew, she flew & I was over the moon.   

Since then there has been a constant mod program of upgrades & improvements. An up-rated  undercarriage, more cells (20 cells) then NiMH cells, then better NiMH & finally LiPo’s (5S).

The next big update was then the change to a Brushless Contra Motor, the TCM2(1000W motor). This took what was a very marginal model and transformed it into the GT version, with the All Up Weight (AOW) down to 10lbs & power to spare. The only thing now missing was the 3-blader propellers.

So the following season saw her with yet another new motor the TCM3 (1500W motor) with more power and a pair of 3-bladed propeller. This is the final upgrade for now; I have done all that I had set out to do. All that I had dreamed about doing when I was a school boy