CTx2 Twice Size Cloud Tramp
Washing the dishes after a pleasant meal I was pondering what my next design project might be…I wanted something simple but satisfying (just like the meal I’d just cooked!)…what would fit the bill?
All of a sudden the pieces fell in to place…..some time ago I had purchased a GWS Cub and been amazed at its slow flying performance…I had immediately wanted to duplicate that performance with traditional methods rather than foam……What about a big Cloud Tramp????
The original rubber powered Cloud Tramp flew EXACTLY the way I wanted….surely it could be scaled up and still perform in a similar manner? Also appealing was the idea of all sheet construction just like the original, with the promise of coloured tissue doped on the sheet, a finish I particularly enjoy doing. And finally this could be a quick design and build so that I could be flying it this summer.
The first and most important job was the wing…..Jedelsky construction was the obvious choice……. time for a bit of research on the net and in my archives. To be honest this was a bit inconclusive…..there is information but its sort of patchy…so I decided on a what looks right etc. approach.
I applied that to the dihedral as well, the original looks excessive but works well, I have a suspicion that it’s actually the key to the whole design. Why?-well because it places the centre of effort of the wings (the mean point that all the forces work through) well above the fuselage. I believe this gives a pendulum effect and thus the stability so although I reduced the dihedral a little it wasn’t by much.
For the technically minded that aerofoil section was developed using the latest hi-tec processes…..i.e. use the top curve of a Clark Y!!
I slightly lengthened the wing from the original to give a wingspan of 50″ and area of 266 in² and at this point with nothing else designed, the balsa stock was raided.
Suffice to say lots of balsa shavings and dust later a rather attractive wing was being whirled around in the garden so that I could feel the lift and balance. Certainly keeps the neighbours interested…but then they think I’m very strange anyway as this type of occurrence is not infrequent and may even take place at night if the winds calm….Hmm you can see their point!!
I should add that for motive power I had decided on the A type 5.9/1 Ratio IPS System which turning a 10 x 4.7 prop would give me 4.6 oz of thrust. From experience I knew that this would fly 11 ozs so that gave me a target weight. Weighing the wings showed that this would probably be optimistic as I had ‘spent’ over 4ozs already.
Eventually the aircraft was fitted out…….finished and weighed…..as anticipated very heavy at just over 13ozs…..oh well fly it anyway….design and build time, six weeks.
I must add that careful weight selection of the balsa would reduce the weight significantly….I had simply used what I had, which was all medium weight approx 11lb/cu ft……. if light medium say 9lb/cu ft was used an 18% reduction could be expected to about 11ozs which is the target weight. A careful combination of light medium and light (say for the tail feathers) would take it down below that…all depends on how far you want to go with such a simple design…interesting challenge though!!
Guidance system used:- Futaba R114F micro Rx
Tower 6gm Servo’s (cos they are very cheap!)
2mm dia Carbon Rod used for pushrods.
GWS E300 8A Li ESC (cos I had one already)
Needn’t have worried the first flight was fine……slow, stable & majestic, just what you would expect with such a fine heritage…..a bit underpowered as expected, although not drastically so, just nothing in reserve. Flying of course is in the powered glider sort of envelope…. thinking large Rubber duration, but under your control is about the experience i.e. smoothly guiding, certainly NOT one for the adrenaline junkies …..for anybody with a free flight background, its actually a bit spooky to have that kind of control of what amounts to a sort of ultimate free-flighter and see the results in action.
In short the whole project met, if not exceeded my expectations and strangely enough was something of an anti-climax as there were NO issues other than the lack of power….it’s just a darn good aeroplane!
further CTx2 Development
There’s been no need to change anything (would make rudder a bit bigger to give a bit more authority) major to the aircraft its just excellent as it is. On the suggestion of Walt (a trusted supplier of GWS bits) I up-rated the IPS to a IPSD (Dual Motor) Type 1 4.1/1 Ratio on a 10 x 4..7 prop, this gave 7oz of thrust at 3.7A on a 2S1P LiPo.
This solved the marginal power problem but of course duration went down a little.
I’ve now fitted an IPSD Type 2 5.9/1 Ratio with an 11×4.7 prop which provides 8 oz of thrust at 3.3A – duration is fine as I can carry up to 640mAh LiPo’s and without the undercart many a happy, relaxing LONG flight has been made chasing lift from rough fields.
Surely I’m not the only person to have done this OR AM I ??
1.5X RC Cloud Tramp
I subsequently made a 1.5 size RC Cloud Tramp as the twice size is a bit on the big size for my small flying field…..of course it flies just as well…..
Den Saxcoburg firstname.lastname@example.org