CG Gentle Lady re-do and Electrify
I picked up a Gentle Lady used at the Lebanon Swap Meet, and a few other things. :D
GL rebuild completed 03/29/09 and test maidens in not so good of weather are done and approved!.
Gentle Lady Project
Gentle Lady, the RC love of my life over 20 years ago. Ok....It was the only thing I flew successfully back then, had to get another.
I found a great thread for the Electric GL,
a little girl named Hanna <doing a GREAT job> is building a GL that will be electric powered. I hope to get my oldest daughter into the hobby with this one.
We sort of chattered up the thread with some discussions around power and weight, as with any thread, I hope it provided information for others that was helpful, I learned much.
Pictured below is the GL when she came home, she was tattered, had been .049 powered I think, but there was no sign of holes in the fuse to provide fuel of anything to the power plant. Her H Stab had been repaired badly, tail looked fine but once the covering came off the history was clear.
The Fuse to start was 236 grams or 8.32 ounces, with just the original push rods and the Wing is 320 grams or 11.287 ounces for a total weight of 556 grams or 19.61 ounces.
The task was to strip the fuse, clean everything up. Rebuild the H Stab, ended up needing to work over the V Stab and Rudder, getting it all apart meant parts needed replaced.
Front hatch fit poorly and I did not like the design, changed it and glued together the old hatch with a new sheet of balsa, curved while the glue set, so it would follow the contour of the nose.
Removed the over built firewall and the 4, 1/4 ounce lead weights on the back of the firewall.
Tail section rebuild went very well, I bought a very large box of Balsa and Parts last year at the end of the RC Flea Market for 5 dollars, it had everything I needed. The way I redesigned the V Stab to go all the way through the fuse to the lower tail, there is no need for the gussets and additional bracing for the H and V Stab. Not using the original push rods meant this would not be an issue for the elevator control. I went with Golden Rods from Hobby City. I did use the original bent push rod end for the rudder so it still looked and functioned as the original parts.
I used only PU Glue <Rhino Glue> that foams, I did not add water to speed it up, I wanted a good long cure with less foam expansion. This is the first mono cote I have used in 20 some years, but it turned out ok. The GL came with some mono cote that was left from someone already doing the wing. I also purchased this year a large box of monocote for 5 dollars that had a brand new role of the orange and scrap roles of orange and yellow. Very low cost rebuild on this bird.
I cut a 1/8 inch piece of lite ply a little larger then the firewall. I cut a near 1/4 the same size of balsa. I cut a 1/16 the same size of lite ply and made a Blasa sandwitch with the PU glue and clamps. I made is so the 1/16 lite ply set just inside the fuse side and the rest went forward of the fuse. The firewall was configured 0 down and 0 right thrust. Sanded and shaped it to match the nose and drilled it for the X mount and the wire access.
I used small servo rubber bushings and 4-40 X 3/4 inch machine screws to mount the motor. According to Carl Goldberg's online information, the .049 motor was to be mounted with 0 degrees down and 0 degress right thrust. By using the rubber servo bushing and some Locktite on the threads I can "tweak" the thrust if it turns out needed.
Motor and ESC was in stock, bought used and they were too heavy for my other foam projects.
E-Flite Park 400
Park 400 Brushless Outrunner Motor, 920Kv Product Specifications
Size: Replacement for 370/400
Bearings or Bushings: Bearings
Recommended Prop Range: 9x7 to 11x4.7
RPM/Volt (Kv): 920 (rpms per volt)
Shaft Diameter: 1/8 in (3.17mm)
Weight: 56 g (2.0 oz)
Overall Diameter: 1.10 in (28mm)
Diameter: 1.1 in (28mm)
Continuous Current: 10A
Maximum Burst Current: 13A
Cells: 2–3 Li-Po
Speed Control: 10–20 amp brushless
Park 400 BL, 920Kv EFLM1305 140W .10 ohms .70A 10A 13A 6-10 2-3 2.0 oz
(56 g) 1.10 in (28mm) 1/8 in (3.17mm) 1.15 in (29mm)
20-Amp Brushless ESC (V2) Product Specifications
Brake: Yes, programmable
Continuous Maximum Current: 20A
Input Voltage: 7.2–14.4V Ni-Cd/Ni-MH; 7.4–11.1V Li-Po
Dimensions (WxLxH): 36mm (1.4 in) x 24mm (.95 in) x 9mm (.37 in)
BEC Voltage: Dual BEC circuits
Auto Cutoff: Programmable
Weight 14 grams
Folding props are new to me, I have ordered one from Hobby City
Folding Propeller w/ Alloy hub - 10x8
I test the motor with;
Eflite Park 400 920Kv 56 Grams
Eflite 20 amp esc
Rhino 3S750 topped
10X5 APC E Prop <not folding> 110 Watts pulling 9.8 amps
11X7 APC E Prop <not folding> 142 Watts pulling 13.2 amps
We will see what the performance yeilds and decide if the HC prop is the answer. It looks like I may have to maiden on one of the test props since the other has not been shipped yet.
Sanded the fuse after striping, built up and widened the lip of the wing saddle so it would have a slighly thicker wing tape to meet the wing, worked out very nice and elevated the wing by 4mm. The saddle tape is a weather strip I found at Wal Mart that I just love, lighter in weight then what was on it, softer texture and ribbed and VERY good sticky to hold it in place.
I also before covering drilled out 6, 3/4 inch holes in the fuse to lighten it and also help get my fingers in places while working on the fuse. These holes only took off around a 1/2 ounce.
The innereds are nothing thrilling. Front hatch has the ESC held in the top with a couple touches of hot melt to keep it off the direct heat of the Lipo. The Rhino 3S750 <very nice 8-10 dollar lipo at HC> has a velcro strip to hold it to the bottom of the fuse with room for the 3S1250 I ordered <with the folding prop>. My 3S2150 fits as well but it has the Dean and not the micro dean.
Under the wing we have;
<disclaimer>Servos not recommended for faster or heavier applications
Turnigy 16 gram Rudder Servo
Under 6 dollars each.
HXT 14 gram Metal Gear Elevator Servo
Under 9 dollars
Corona 6 Channel 72mhz Dual Conversion Synth <no crystal> DSP Long Range RX 10 grams and full length antenna.
Golden Rod connecting rods.
Servos: Rapped the bottoms with 3M Blenderm Tape <best hinge tape EVER made for foamies> and used a spot of Hot Melt on the bottom, side, and the horn mount touching the forward bulk head. Tape will come off the servo later so the Hot Melt doesn't damage the case.
RX has the same on its bottom side with a small amount of Hot Melt to keep it from sliding about.
Center of Gravity
Designed to CG on minimum requirements, with the smallest Lipo I would use, all items were placed to make CG as close as possible.
Accordning to the Carl Goldberg site;
CENTER OF GRAVITY
Balance Point on fuse,
measured back from
wing leading edge
3-1/2" to 3-3/4"
I marked my wing tape at the 3-1/2 inch mark, the GL with the current APC E 11X7 prop, it CG's at the 3-3/4 mark. I am assuming the Spinner and folding prop will add a touch more weight to the nose bringing it back to the 3-1/2 mark. <i hope :D >
Weight........... The verdict is in
737.6 grams AUW or 26.01807433 ounces
Folding Prop and Spinner was not included and I only had one rubber band, 3 may be more suited.
Not the best photo location, I took the caps from a video which is too big to just upload.
Video File Here
Please, no motion picture awards.
Weight verses Weightless
According the the Carl Goldberg site, the GL flying weight is
"Flying Weight: 25 oz."
All in all, I really did nothing major to save weight, I cleaned up some bad past repairs, cut a few holes, used a very strong but light glue for repairs and used electronics suited for this weight craft. I did not "over" over lap the mono cote, that builds weight quickly.
What I didn't do was use the servos I used 20 years ago, <I still have them in a box> :eek: they are 50 grams each. I did not have to add extra structure for the heavy battery or High Torque Motor. With a much heavier craft, the lighter servos are not a good option.
Not having the full size radio RX <40 grams> saved an additional ounce.
Wing Area: 663 Sq."
Flying Weight: 25 oz.
Fuse Length: 41"
Engine: Right 0
CENTER OF GRAVITY
Balance Point on fuse,
measured back from
wing leading edge
3-1/2" to 3-3/4"
I just have to tighten up the mono cote on the wings, validate there is no twist in the wings and that the tip Washout is set correctly. I could use some tips on that part, it has been a while.
Maybe some mono cote graphix to spice it up?
Looks like the sky has a weekend long leak of water planned. Maiden and Video to follow.
In between showers I took the GL out to the field. Weather.com stays 10-15 mph winds today and rain / t-storms possible. Wind at home 4-6, wind at club field 10 gusting 15.
I used a 3S800, my 3S1000 wont fit well due to the charging tap and the direction if comes out of the pack. <must correct> Still had penitration with power, the 1000 or 1250 would have made more difference.
1/3 throttle was more then enough to launch and hold forward motion into the wind. Once the nose turned, seemed to lack rudder authority even on the high rates, also need to drop the expo down. Elevator has plenty, may need a bit of down trim but with the gusts, to hard to tell at this time. Very impressive power, slow vertical is possible without issue.
Being on a mountain, I kept it no higher then 30 feet, winds aloft could have been much stronger. Has anyone ever thought about inboard ailerons? I know that is not a high functioning item in a Dehydral/Polyhedral wing, but it would be nice to atleast be able to level the wings on command.
The GL is not really a high wind worker. what is the torque of your servos? you also might try supporting you pushrod tubes under the wing saddle they might be deflecting with air pressure on the rudder in a turn. I am taking a guess here but it look likes you have rudder servo on the right you have connector pretty far out on the horn this will reduce the power the servo exerts on rudder. This is all I can guess at without hands on the glider.
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