Motor recommendations for high efficiency and endurance

[thrasher0815]

Hello Flighttesters,

I've recently discovered this great hobby and thanks to FT quickly had a look at all the varieties and the possibilities to complicate matters.
My plan is to build a foamie with 60" wingspan, able to cruise great distances and am looking for the right motor for it. I was wondering if someone could recommend me a motor that's able to push against some moderate breeze and be as gentle as possible to the battery, together with an 8x6 prop.

How would you go about selecting a motor for such a purpose using ecalc? Yes, I can look at different motor/prop combinations and compare the Thrust vs. Amp but do I have to do this one by one or are there some indicators to limit the motor selection beforehand?

Thanks
Robert

 

[offaxis]

http://www.flitetest.com/articles/60-wingspan-old-fogey
I hope this helps.

 

[eagle4]

Hey mate, welcome to the forum and the hobby

the thing to think about is also your airframe. if you build something big and draggy it will require more work by the motor, but something like the simple soarer which is more of a slick fuselage will require less effort to fly, which means your battery will last longer as the motor isnt working as hard to pull it through the air. also the weight of your plane. build it light and your battery will last longer.

what kind of distances would you like to achieve. you say you want to go great distances, but some people think 1km is a great distance, others consider 20km a great distance. i think once you work out what plane you're wanting to build, then you can work out how much battery it can carry, and then that'll give you a rough weight and will help get you the best motor for the job.

 

[thrasher0815]

Hi and thanks for the replies!

the thing to think about is also your airframe. if you build something big and draggy it will require more work by the motor, but something like the simple soarer which is more of a slick fuselage will require less effort to fly, which means your battery will last longer as the motor isnt working as hard to pull it through the air. also the weight of your plane. build it light and your battery will last longer.

Those where exactly my thoughts. I built an Armin wing prototype out of two DTFB sheets which will make my first test flights, but in the end it will need more stiffness and an optimized profile. I'll probably shoot for coated XPS with carbon spars.
aerodesign.de is a great source for known profiles with aerodynamic tests.
The airframe itself will be a slim tube, similar to the simple soarer.

what kind of distances would you like to achieve. you say you want to go great distances, but some people think 1km is a great distance, others consider 20km a great distance. i think once you work out what plane you're wanting to build, then you can work out how much battery it can carry, and then that'll give you a rough weight and will help get you the best motor for the job.

I'll start off with endurance flights in line of view but would love to extend the range together with my experience. Ultimately, 20-30 kms would be an achievable goal. Trent from MyGeekShow managed 72 kms with a Turnigy D3542-4, maybe I should give that one a go?

 

[quorneng]

Thrasher0815
It may sound obvious but for endurance you need to optimise the airframe weight rather than the aerodynamics although minimising drag is still important. Power to fly is measured as the product of weight and sink rate.

If you can get a complete plane to carry a battery equal to its own weight (and still have a practical reserve of strength) then really long (several hours) endurance can be achieved so even flying slowly you will go quite a long way.

This small 48" span plane only weighs 14.5oz (413g) despite having a 5000 mAh 2s LiPo on board but it can maintain height on just 7.5W (tested) thus giving a potential cruise endurance approaching 5 hours.

Even though it only flies at a modest 10 mph it would still go along way in a straight line - particularly down wind!