Indoor Design, non traditional, not foamy but electric

[Ratz (Bruce)]

I am embarking on a project for indoor. I want to move away from the traditional Foamy style of airplane and do a conversion of a outdoor free flight design to stick and tissue RC.

I have obtained a very small E-Flite Park 180 2200KV Out-runner motor model EFLM1120 and the E-Flite 10 amp 2-S lipo speed controller. I am hoping to build this system into a Micro-X Hornet P-30. Hopefully I can hit my target weight of 130 grams max with this setup. Hardware and systems weight is looking like around 78 grams, that leaves me with an air frame build of about 52 grams. I feel that the 55 grams air frame weight is generous and it's not an overly complicated design. Others are building this airplane for outdoor free flight at about 70 grams. The 130 grams AUW puts this air frame in the Sport flying category. I am not a real sporty flier, so this may give me power for spiritedly climbs and minor aerobatics. So we will see.

I am slowly trying out projects in the electric airplane class of modelling and this is a good place for me to start. Once I work out the hardware and performance parameters, I think that this setup will make for a good base line to build into lots of 130 square inch wing area airplane designs that come from the outdoor rubber free flight class of airplanes.

I have chosen common brand components so that the setup is not overly complicated.
Flysky Radio, typical 9 gram servos, and small 130kwh 2S1P lipo batteries.

I will be using single line control system with spring loaded rudder and elevator for a spring loaded pull thread control system. I used this on a number of small RC sailplanes and that is proven in the Discus launched glider airplanes.

So is the plan.

I have been energized lately with the operation of the forum and that has made me excited to do more model aviation. The last few years have been a low point in my model aviation.

Cheers

Bruce (Ratz)

[Monz]

You could easily get away with 1.7g servos instead of the 9 grammers. Just make sure the springs are quite weak. I fly DLG and those servos have mucho gusto. And extend the span by a rib bay or two.

[Ratz (Bruce)]

Ok, good tips, I will add a bay of wing area easy. I will look into the micro servos I have, and see if I can get smaller ones. I am using the bits I have on hand at the moment. But a bit more WA will be reasonable.
I have some really thin .008 or .006 wire from some Guitar stuff... I wont need much springy.

Bruce

[USch]

Take any reasonable wire size to make the Z-type spring. It is the length of the intermediate leg that's matter on torsional stiffness.

Urs

[Tapio Linkosalo]

Why not use pull-pull -threads? Would reduce the load on the servos and thus cut down power consumption. Using some thin dyneema thread should provide accurate control.

[Slowmatch]

You could easily get away with 1.7g servos instead of the 9 grammers. Just make sure the springs are quite weak. I fly DLG and those servos have mucho gusto. And extend the span by a rib bay or two.

I agree that smaller servos would be a good weight saving but I might be tempted to use the slightly larger Emax ES9251 which are only 2.5g (3g including plug and wire) but have quite a bit more torque for aero loads in more exciting flying. I've used them very successfully with pull/springs on a 30" DLG. And they should (?) have the correct plugs for your rx too.


Jon

[Ratz (Bruce)]

I am using this servo, SG90 9G Micro Servo. It's a bit less than 9 G on the scale. I had 10 of them sitting around. Since I am not going to use wire pushrods but cable torsion spring loaded controls I will save weight without any pushrods. I have used the spring loaded control surfaces before with .006 single strand music wire and that worked famously before. I may test some spring wire even thinner if I can. This fine monofilament cable system is so light I save weight there. The rest of the most weight is in the lipo battery so I build my batteries for these things using Lipo batteries scavenged from the discarded cigarette puffers that people throw out I find on the street. I have any number of good lipos for these kinds of things in the 200mah up through the 1200 mah lipos that come from the puffers. Free is good, so when you find those discarded puffers, pick them up they contain 1S chargers and 1S lipos in them that make great batteries for these kinds of simple airplanes. I will weight the other parts of the control/power system in a bit and report. I hope to keep the control/power package under 70 grams. So then I have to build  a light airframe. Since this plane is used indoor RC I will make it covered with wallmart craft tissue and EasyDope for goos results. I have used this tissue and easydope to good effect. This airplane will not be a 3D plane but be flying on it's wing and will be a cruiser. Perhaps enough excess power to manage the odd loop. The name of the game is to show up at the venue with something completely different than the typical indoor foamy. I am not a fan of foam, I like my wood for the flexibility in construction that it avails, your mileage may vary.

Thanks all for the points of view that help me make informed decisions.


Bruce