No Name Plane

The wing has moved on a bit, all the electronics are fitted and working. Motor is SK3 3542 1250Kv. Max amps 54, 3 to 4 cell. Aerostar 60 amp ESC - max burst 70 amp. On a static test with my favoured 4 cell 30C lipo my ammeter recorded 69 amps WOT using a APC 9x6 pusher prop. Seems a lot and not much thrust to me. The next available prop in pusher config is 11 x 7 (all the 10s are slow fly). Retest - if you take a look at the screenshot from the flight Controller (verified by a clamp meter too) WOT was 58 amps (791 watts). Could definitely feel thrust now! That would do okay as WOT would not be generally used.

However, using the bigger prop has brought about some issues. I have been mulling over which way to go with the wing fins placement. Original plan was to fit profiled twin fins in the slots pre-cast in the wing shown by the arrows. but there is not a lot of prop clearance. I could move the fins outward by 18mm each side maybe. Looking at various designs of wings from custom made to arf, etc, etc which only makes the decision harder. It appears that for stability, especially at slow speeds they should be on the wing tips which reduces the stall. Also I noticed that some designs have vortex generators along with wing tips and i understand why they are there. But as it is a big wing, 1500mm wingspan it is going to be awkward to load into the car. Probably knock them off!

Then I looked at inboard fins, say at 33% in from wing tip? Maybe add small winglet at the wing tip to stop the air flowing over the edge?
Note: AUW is approx 1.9 kgs depending battery pack

Any comments that will help me decide on way or another gratefully accepted. More balsa turned up today!

As a footnote: notice how much the battery voltage drops when asking for high current. This was a fully charged 4 cell 30 C pack. Thinking of you EDF pilots....:lol:

Phil - Cannot understand why you are getting involved with "Pusher " props,why not just reverse the motor rotation
and use a standard prop with a wider choice of sizes.
Looking good so far, fins & winglets , really cool.

Colin.

4Pedalsfly wrote: Phil - Cannot understand why you are getting involved with "Pusher " props,why not just reverse the motor rotation
and use a standard prop with a wider choice of sizes.

There is one very good reason Colin. Looking at normal tractor prop on IC or electric from the front. It turns CCW. The thread on the locknut is right-handed so the torque from the engine helps keep the nut tight (usually ) I have tried using standard props and reversing the motor and have usually got away with it but there was a few times a while ago on earlier versions of my powered wings, albeit with smallish props when the prop spun off in flight. :ohmy: I may however try it and make some form of locking device if any of my other ideas don't come to fruition.:lol: Oh, the fun of it!

Phil - Good point, but I've never had a prop come loose on my Zagi which is now over 10 years old."
Couple of thoughts on locking devices, easiest "Loctite" lower strength, or try a Castle nut & when tightened
drill a small hole through the aluminium adaptor shaft and wire lock it.

Colin.

This is what I am thinking too.
Progress is moving forward on the wing two steps but sometimes back one step. If dry weather lasts long enough I will try standard 10 inch prop for thrust and amps. If reasonable then I can then move on to making the fins and finalising their position.

Things have moved slowly on. Gave up on the idea of a 9x6 prop and fitting inboard winglets. Keep it fairly simple! Designed some balsa wing tips but just as I was about to profile them I had a sudden thought. The 2M Opterra has plug in wing tips and by comparing the photos and scale I swanned over to Wheelspin Models and managed to acquire a pair of spare wing tips. I am now working on a way of making them slot on to my wing. I have a plan but whether it works in reality we will see.

Colin, now not using inboard winglets this leaves all options open for prop size. At present I am using a standard APC-e 10 x 6 CCW and have reversed the motor. Plent of thrust and only at WOT does the power consumption exceed the motors 55 amps but not by much. But then again it may not need WOT for anything except vertical climbs....:lol:

A thing to note: I really wanted to paint the foam and then laminate it. But when I had trouble getting the 50mm glass fibre tape to stick to the rough Hobbyking foam wing a few years ago I used some 3M adhesive. It has really stuck it down so any attempt to lift it would probably ruin the wing so leaving it "au naturelle" or "As is" is my policy.