Hello,
I fly currently two indoor electric models (MP Bee1 and Wasp: see the attachment).
The third model shown, LGWII, with white fuselage and uniformly yellow wing, is the outdoor electric trainer for Cobra 2814/12.

MP Bee1 resembles Igor Burger's indoor Gee Bee, Wasp is modified 330 SC foamie (http://www3.towerhobbies.com/cgi-bin/wti0001p?I=LXYSC1). Respective RTF weights are: 9.1 oz. for Bee and 7.8 oz. for 330 SC.

Bee's wing is stiff enough but 330 SC wing lacks torsional stiffness and twists during flights. I will add more carbon composite struts and this will fix the problem but I started thinking about build up 36" rectangular wing for the indoor foamies.

Such wing, with say 24% symmetrical airfoil, can be build as thin shell using 3 mm. grey Depron when it becomes available (http://www.rcfoam.com/depron-and-epp-foam-suppliers/depron-foam-sheet/). I have this material and it is more flexible than original white Depron Aero. After the sheet is properly heated with the covering iron, it can be carefully wrapped around balsa ribs and glued together. Such wing does not need spars and L.E and T.E beams - it will be sufficiently stiff and strong for the indoor flight having only ribs and the Depron shell. The grey Depron shell can be left uncovered and this will save some weight.

Building the indoor wing using the method described above may be a bit difficult and may require some form of fixture to temporarily hold the ribs in place while wrapping Depron but such wing will be much stiffer than flat Depron wings.

I wonder if anybody tried this method before and, if yes, what was the weight of the finished 36" wing?

Thank you,
Matt

Hi Matt, airfoiled wing will not work well in slow indoor flight. The reson is called critical reynolds number. If you are curiouse, try google. The point is that flat wings does not have any critical reynolds number, they fly the same slow of quick.

Kim is right, the weight is high, but unlike R/C with counterprops, we need some weight, looks like 180 to 200g is good weight for models of that size. I tried to make it lighter with smaller battery and motor, but I did not get anything better flying, reason was too low line tension, simply I was not satisfied with lighter model.

Regarding stifness - you have to use either reinforcing like I have on my GeeBee (foam plate - it will give also little bit area), or you can use also carbon rods, but they have to be organized so, that they do not allow wing flexing (that mentioned triagles, not rectagles etc), it is not bad to look to real GB, it has also such things.

We fly lap times aproximately 5.3 ... some of us 5.5 and some 5.0, I will attach my old vide showing speed on 5m lines

I have Maxbee page here:

http://maxbee.net/index/index.htm

But if you mean home page for indoors, then here is link to Tania's home page:

http://www.indoorgeebee.com/

But there are also "more alive"  FB pages which we update more often:

https://www.facebook.com/MaxBee-363984487112995/

https://www.facebook.com/IndoorGeeBee/


 

Igor,
I know that 4 deg. down thrust is used in many Bees using the normal props.
I believe you recommended 4 deg. up thrust when the pusher props are used.

I think so, but I have never tried pusher ind that configuration

If this is so, the motor torque must be somehow reacted using the geometric ( thrust angle) or/and aerodynamic means (ailerons?).

That is real problem, while precession is relatively easy to deal with, the reaction torque of 10" prop on such small model, is difficult to compensate. Yes you can twist wing to keep it in level in normal flight, but when you slow down, reaction torque will be much stronger and aerodynamic compensation weaker, so it will "fall in" in negative maneuvers, the only way is to create artifical line tension which will keep wing and lines paralel - means cancel effect of that reaction torque.

Merry Christmas and the Best 2017 to Everybody!

I did not touch the motors yaw angle. This angle is zero degrees w/r to the fuselage longitudinal axis.
1. I have increased the surface area of the front portion of Wasp's fuselage by 4 sq.in.
2. I have removed the air brakes from both models.
3. I have added the outside wings Depron ailerons ( 3 sq.in.) that are bent down ~7 degrees.
4. I have replaced the prop.saver style mounts (with rubber o-ring) with the collet style, aluminum prop.adapters.

I did these changes in the order listed above and flight tested both models after each change flying the outside loops and vertical eights.
1. Had positive effect
2. Had strong positive effect: the turbulent wake was adversely affecting the tail surfaces. Now, both models react in the predictable manner to the smallest elevator movement on top of the outside loops
3. Had very strong positive effect. Now, the motor torque is reacted by the aerodynamic moment. I was wrong with my free body diagram and confused myself.
Comment: because the aerodynamic moment is the function of velocity, it weakens on top of the outside loops but the remaining moment is sufficient to prevent the excessive inside rolling motion of both models. The tendency to roll inside is still there when and if I almost stall the models but "normal size" outside loops look and feel fine now.
4. Very strong positive effect. The gyroscopic moment of the propellers in sharp corners that was stretching the rubber o-rings is reacted now by the motor shaft.
The buzzing sound that could be heard while executing such corners disappeared. This sound was caused by the propellers rattling on the ring of the prop.mount when the o-ring was stretching and contracting. Comment: this behavior appeared when I started flying sharp corners. Sharp corners have higher pitch angular velocity, therefore the gyroscopic moment exceeded the "holding" strength of rubber o-rings.

I have also increased the flight time of both models to 5 minutes with my 2S 800 mAh batteries used only ~60% and the no load (after landing) voltages about 3.79V per cell.

Comment: with 4.6 sec. laps on 5 meter long lines, both models are faster than typical indoor bees. The way they fly is much closer to the outside C/L stunt models and I am finding this very useful for my pattern practice.

Please go to: https://www.youtube.com/my_videos?o=U to see my flights.

Regards,
M