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Old Nov 22, 2015, 08:38 PM
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Airbus E-Fan, work in progress

Having been tempted by an Inductrix in the lhs, I began to wonder if I could find a suitable scale-ish model to suit the fans. A couple of quick and dirty measurements showed 8gm. thrust per unit, and an efflux velocity of around 6m/s so a micro of 30 gm. or so was possible. A chance find of a photo of the E-Fan lead to downloading a few photos and the dimensions, and revealed that with a wing span of around 500mm. the fan diameter was around 30mm., or just right. One set of drawings later, and a bit of depron slicing gave a chuck glider so I could find the cg, and I was quite surprised to find thet even with both fan units behind the cg I could still achieve balance with the battery and brick both well forward but no nose weight. On to assembly. The fuselage is a cf tube with 1/16 balsa formers and 1/32 skin, with the tail unit 2mm. depron with cf rod reinforcement, canopy is clear heatshrik molded over a plug, the wings were 1/32 balsa curved top skin on 1/16 ribs, with a 1/16 basswood spar to tie things together a bit. Brick came from a Whipit, fan and ducts cut from an Inductrix frame, battery a standard E-Flite 150mah. First test glides were reassuring, first powered attempts not so. Any thing over half throttle resulted in the nose going up, and the plane trying but failing to prop hang. Back to the workshop to put some upthrust on the fans, which showed up the next problem of seriously ineffective tail surfaces and weak wings. Increased tail areas (I'd already enlarged them by about 20% over scale), and new foam wings with proper airfoils and an increased chord and dihedral were the other stage of a cure, the downside is weight is up to 40gm. A couple of power off glides have shown its still capable of flight, so I'm now just waiting for a wind and rain free day for more tests.

chris
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Old Nov 22, 2015, 09:33 PM
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Nice build! When I was living in Vancouver I was never able to find a proper indoor venue except for an empty warehouse at work. Outdoor flying of micro model was only possible early in the morning or late evening when the wind died down. Your weight is very good with a build-up fuselage, do you have a link to that Inductrix unit and were did you find it in Vancouver?
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Old Nov 25, 2015, 02:05 AM
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The fan unit is from a Blade Inductrix micro edf quad, and my local source is the excellent Norburn Model Aircraft in Burnaby (Broadway and Holdom). I've got no indoor site, but the forecast is for 4 days of arctic outflow, which means cold dry and windfree!
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Old Nov 25, 2015, 05:37 PM
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Very Nice !!!
You should post in the Micro EDF forum as well.
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Old Nov 25, 2015, 05:55 PM
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Nice design!

16g of thrust for an AUW of 40g seems a bit weak.

2 airhogs fans (11-12g of thrust each) would maybe suit better.

Just my 2 cents....

Good luck for the maiden.
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Old Nov 29, 2015, 09:37 AM
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I've seen the efan too. Fascinating project!

In the micro jets forum I've posted my P80 shooting star using one inductrix fan. Plans from Mutcake. I flew that model with a 150mA lipo after I tried 30mA. With the heavy battery it ended up at 16 grams and it wouldn't climb and I needed full throttle just to keep altitude. At 12 grams it went much better though cg was not ideal.

My expectation is that you'll end up with a slightly extended glide. As a general rule for basic flight you need 2/3 thrust to weight ratio. Otherwise don't bother.

Aim for 25gr max. Cut weight and reduce span to 35-40cm. It can be done!
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Old Dec 02, 2015, 02:16 AM
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Weather held off enough today for new tests, however increased weight meant I had to add even more to get the cg in the right place! Performance best described as poor, now back in the hanger for another rebuild, this time from the ground up, to try to get back to 32gm. I've got other similar size planes that fly quite happily on 1/2 throttle with full power t/w of less than 0.5 so I don't see that as a show stopper, however I am losing control effectiveness due to no nice propellor induced breeze over the tail!
Chris
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