smchale

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I'm looking at <slowly> putting some dwgs down in CAD for a future project and am seriously considering electric power for the first time. Being this is would be my first construction project for electric, are there any good sources for it's design? I've scratch built many IC scale models, some of my own design, but this is me first electric. With electric you don't have the 'vibration' and added strength considerations, etc. Weight for function only is key so the goal is to keep it light. Guess i'm looking for some scratchbuilding tips with electric design in mind. maybe even a good set of warbird plans is the 85-90"span range designed solely for electric that I could glean some ideas from?

Also, battery access, cooling considerations, etc etc....any thoughts/experience?

Dsegal

Take a look at Keith Shaw's four articles posted on the Ampeer website at http://members.aol.com/KMyersEFO/page3.htm/
He is the master and has done it all.

whitecrest

Given your previous experience, you should find designing for electric very enjoyable, especially utilizing a CAD program. The lipo-brushless power system in wide use is very powerful, flexible and offers many advantages over glow. You should not have to alter many of the design parameters you no doubt are already familiar with and will not, as you have stated, need to design for vibration tolerance or the glow engine power stroke. You will be able to design for very light wing loading and still have great strength.

Your biggest problem might be in selecting the right amount of power appropriate for the airframe you desire. The following online calculator greatly simplifies this task:

[link]http://flbeagle.rchomepage.com/software/webocalc_0.9.0/webocalc.html[/link]

It lets you quickly determine how much current will be required using a given prop to fly a described airframe at a desired performance level. With this information in hand, it is easy to select the right motor, ESC (electronic speed control), and lipo battery from the multitude of brands and ratings for each of these essential components of the power train.

The following web site ought to give you many design ideas:

[link]http://plans.aerofred.com/[/link]

All kinds of plans are available here using many different construction methods. Many warbird plans are on the site.

As an example, I used TurboCad (excellent program) to design a light park flyer (very simple design) using standard balsa, built-up construction with wingspan 48" and area 360 sq. inches. I used the Clark Y airfoil (hundreds of others to choose from) and standard RC model design dimensions. My ship weighs about 14 oz AUW and has a wing loading of about 7.5 oz/sq.ft. To power this, I selected an 800ma 3S lipo, 18 amp ESC and a 1.8 oz 1000 KV brushless outrunner swinging a 9x5 GWS direct drive prop. This setup provides much more power than needed. With the power off, the glide is very flat and the model handles very well in 10-15 mph winds with excellent penetration. I had originally planned for rudder-only but found that it turned poorly, probably due to inadequate dihedral (@ 4 degrees). Converting to ailerons solved the turning issue. It now turns in a very tight radius and is very responsive. It will easily fly over 20 minutes with no thermals. I use a timer to limit flights to 15 minutes and avoid automatic LVC which is kinder to the lipos. TurboCad has made ongoing changes very easy to implement. It also makes it possible to have a laser-cutting service cut the most-used templates.

Good luck with your electric design project. You ought to enjoy it a great deal.

ron_van_sommeren

Group:
www.yahoogroups.com/group/GSwarbirds

ron_van_sommeren

A suggestion: would it be wiser to start of first with a smaller plane i.e. smaller motor and batteries, to get the hang of it and the routine?

Several calculators, most of them freeware:
http://www.rcgroups.com/forums/showthread.php?t=606703

Dedicated subfora:
http://www.rcgroups.com/electric-warbirds-248/
http://www.rcgroups.com/giant-electric-planes-477/