Speedo125

Hi guys: I'm giving EDF jets a try after many years of glass/foam gliders and both glow and electric sport models. I've used MotoCalc to great advantage for drive system selection. My question for you guys is: What is a "reasonable" wing loading figure for a jet? I'm coming up with numbers in the mid to high 30's (oz/sq ft). Is this a reasonable ratio to fly with assuming that I'm a proficient flyer? Sounds like a shotput to me.....
Thom

Al Stein

Can you tell us more about what you're building? What size and type jet are you planning?

30-40 oz/sq ft can be fine for a large plane -- I believe it's not at all unusual for prop-driven warbirds in the 7 to 8 foot span range -- but that's a lot of wing volume. A smallish plane would need too much speed at that loading to be very pleasant to fly.

Speedo125

Sure Al:
I'm building a 55" span, 7-8 lb. F-86 Sabre. The one from the Nexus plans. According to MotoCalc my EDF drive system will power it OK. I just wonder if it's gonna be a real pain to fly (other than very fast). What kind of wing loading the other jets and fighters are flying at?
Thom

stefanP

My Feedback: (2)

What fan&motor?? What is the cell count??With that kind of wing load you better have at least 700watts of OUT PUT POWER! Good luck

Speedo125

Hi, StefanP:
The fan is a WeMoTec "Midi". The motor is a Hacker B50-15L. The juice is 20 cells, SR 2400's. Per MotoCalc, the output wattage is 734 at 33K+ fan rpm.
I figured heavy on the built-up airframe weight and hope to bring it in well under the estimated weight of 4 pounds. I'll probably leave the retracts out to save a few additional ounces and opt for a screamin' bungie launch.
Thanks for the info, Thom

stefanP

My Feedback: (2)

Thom,From what I see your going to be rite on the line of flying or failing 20cells weigh almost 3lbs. One standard rule of E-flight is that the power system is half the total weight of the plane or jet in your case.So 3lb for battery,now the rest of your system needs to be 1lb(motor/esc,receiver battery,servo's&receiver).If you can get the jet in at 3lb then you will be safer.Check the what the hacker motor max amp's are.According to what you posted your motor will be around 31amp.(voltsXamps=watts)Another thing I always do is a STATIC THRUST TEST! This is a simple way to check static thrust. I use a inexpencive fishing scale tie it on to the tail of my plane secure the other end to the ground (or something that wont move ) .With a fully charged pack and I also have my Astro Watt meter between esc and battery pack(I am also measuring total amp draw &watts) push the throttle stick to wide open and read the scale.Generaly you to pull AT LEAST 1/3 of the total plane /jets overall weight.For you I would want at least half or better.Say it comes out 8lb,you want 4lbs min.But 6lbs is what I'd look for.It may sound complicated but at least when you go to fly the jet you wont have to worry about a disaster.I hope I wasn't to long winded.Again good luck,stefanP

Speedo125

Thanks StefanP: I've gone back into MotoCalc and switched to 2000 mah SR cells and reduced the number to 18. Total weight of pack is now 37.20 oz. Hacker B50-15L = 8.81 oz. ESC = 1.5 oz., so total drive system is approx 48 oz. I plan on using mini servos as well. I've calculated the thrust to be 50.8 oz for a T/W ratio of .55:1. Wing loading at conservatively projected airframe weight of 48 oz is now 32.2 oz/sq. ft. Unfortunately, my Watt meter is back in the States on my buddy's workbench. I'll be extra careful with my balsa selection and avoid ply wherever possible. Thanks, Thom