Christchurch and District Model Flying Club
 

E-Flite Electric retracts

By marting burr

 I have a Ripmax Spitfire it is an ARTF model and is an excellent flyer. It was originally designed for a 600 brushed motor and NiCads, and has quite a generous wing area, and very lightweight built up construction. So when you add more up to date power, in the shape of Brushless/ Lipo it really comes alive.

I have flown it many times, and the only real problem is in launching it, as it has no wheels you have to launch by hand, this is quite difficult as there are two small, flimsy, finger holds under the wing, and as soon as you run the motor the plane tries to rotate downwards putting the prop into your wrist ! The only way I have found to stop this, is to put your little finger forwards under the cowling then launch on half power adding the rest as soon as you can. This is all easier if you have an assistant of course, but not always possible.

So I decided to make a wirework undercarriage that would stay with the plane, I glued a tube in each finger launch hole then triangulated back to the wing bolt and across to the other wheel. This proved to be a good solution as the launch was much easier and less dangerous, and it always looks nice to see a plane rise from terra firma. I have flown it like that for quite a while, but it always niggled me that I couldn’t put the wheels away in flight. So I set about trying to remedy this.

I bought some retracts from Giant Cod, these were just moveable legs and needed servos, but I couldn’t get them to work satisfactorily on the bench.Then I bought a plane from E Flite, a Mini Funtana X which is a superb 3D beastie, this led me to look at their website, and there was the answer to the retract problem.

They were advertising their latest creation, self contained electric retracts ! They showed them working on the site, and demonstrated one of the features of the units… if they get jammed, they don’t just sit there stalled, they stop and wait until the next signal comes, then re-sequence themselves so they don’t burn out, or drain your battery. They only use 5mah when idling and 150mah max.

I thought, “Ok looks good, how much” so I looked at price through one eye, then opened both. £50 for a pair, they come complete with wiring harness, and axles for wheels of your choice. I think that’s pretty reasonable, if you think that 2 half decent servos would cost £30 / £40. They are well made, and robust and seem strong in use. There is a tricycle version too with a steerable nose leg for (I think) £80. (69.99 – Ed) So a call to CH 4 Models had them ordered and on their way, John had not heard of them so he was interested too.

They soon arrived and looked to be a winner. I tested them on the bench, with sons helping, they survived that, so they must be indestructible! They need only need 4 screws to mount, the rest was up to me to provide a suitable home, so after gathering a bit of courage, (and some wood) I cut into the covering of my lovely Spit. I opened her up, and added bracings to the main spar to take the mounting plates, then after lots of “try it, sand it, try it again… try it, sand it, try it again” I glued them in each side. then made sheeting up to re glue the covering to. I cut out enough to let the legs clear, then came the wheel wells….ummm…… how do you make wheel wells ? Then a brain-wave (that’s it for this year then) I used spray can caps, the large 500ml can size being spot on, and allowing a bit of clearance all round, they even came in black !

Well “how do they work in service” you ask, (that’s if you read this far) the short answer is “perfect, no problems at all” they do exactly what it says on the tin. I have repeatedly stalled them on purpose to demonstrate this feature with no ill effects and they have had several landings, with no bending of the legs, so have needed no repositioning. Mind you, I did make sure that the mounting points I made are almost impossible to move, without destruction of the wing. I am sure that this firm base helps a lot.

They have added a bit of weight, but I have not actually noticed any real difference in flight or landing, so it can’t be much. I needed to move the fight battery back a bit to keep the CG about right. As I said earlier the plane was designed with heavy Nicad and brushed motor power train in mind so, I don’t think things are over stressed.

And the best bit is…. I can flick the switch, and put them away after a take off, (I love that bit on the full size) now I can pretend in miniature, and after the sortie, I can put the wheels down again and land.

Martin Burr

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