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Building Carl Goldberg Gentle Lady for electric.

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Old 01-10-2016, 01:26 PM
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Capt. Bill
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Default Building Carl Goldberg Gentle Lady for electric.

I haven't seen any recent posts for this so thought I would bring it up. I am building an original Gentle Lady and plan to convert it to electric. The original kit is a lot better than the current one, lighter wood and better parts fit. I build one of the new kits and put an OS .10 engine on it and it does well. The original kit should come in at around 22-24 ounces without motor or battery. Any tips as to motor and battery choice would be appreciated.
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Old 01-10-2016, 08:21 PM
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Hi;
Well I don't have a Gentle Lady, but I am building a Riser 2 Meter Sailplane and this is the electric system I am going with. Motor: http://www.hobbyking.com/hobbyking/s...ess_Motor.html

ESC: http://www.hobbyking.com/hobbyking/s...ontroller.html

Battery: http://www.hobbyking.com/hobbyking/s...dproduct=58837

Programming Card: http://www.hobbyking.com/hobbyking/s...ming_Card.html if you want to put a brake on the motor so that that folding prop will fold. Sometimes the air will continue to turn it creating a drag.

Watt Meter is a must. This is the one I use: http://www.hobbyking.com/hobbyking/s...dproduct=34137

Last edited by Aquila1954; 01-10-2016 at 08:24 PM.
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Old 01-10-2016, 08:44 PM
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Thank you very much. I have been a glow engine guy for 44 years but never made the jump to electrics but the Gentle Lady seems like an obvious choice. I don't want to go electric for my sport planes so not looking for anything expensive. This is gives me a good starting point.
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Old 01-10-2016, 11:49 PM
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Back in or around 1980, I flew a Gentle Lady off a high- start or I stuck a .049 "Black Widow" Cox motor in a power pod above the wing.
This was mine plane back then. Don't have it anymore, I should buy another one and do what you are planning to do.
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Old 01-11-2016, 07:16 AM
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Want a complete layout for that Lady? Take a look at a clone that comes with motor/folding prop/esc/battery, basically answering every question you'll have:

/http://www3.towerhobbies.com/cgi-bin...&I=LXENWS&P=ML

They show a 3535-1000 motor. $52
30A ESC $39
2"spinner/folding prop 12x6.5" $20

The motor matches up with their .15 Rimfire, which is a touch more expensive, but probably less of a gamble.

Almost every 2m glider is going to work really good with components that match that list, although maybe a 45A ESC would make sense.
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Old 01-11-2016, 08:14 AM
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I also had a Gentle Lady from the 80s that I built back then but it sat around for about 20 years before I got it flying. I had a couple of old Cox 0.49s that put on it but had trouble with. I put on an OS .10 but when I redid it and moved the servos to add throttle I did not get the elevator pushrod secure and it crashed. I got one of the newer kits but the wood was heavier and when they changed to laser cut the parts fit was not as good. The kit I am building now is one of the original kits that I picked up on Ebay a few years ago for about $30 dollars. I like Aquila1954s set up since I don't want to much that much into it.

My Lady from the 1980s
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Old 01-11-2016, 03:28 PM
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The Vista is not a bad plane, except I read that the esc will burn out and might take the motor with.

I have a Great Planes Electrify Spectra (ARF) that my brother bought back in 2004. I ripped the brushed motor system out of it and put in a brush-less system instead. I recovered it now. This is what it looks like now. It was White and Blue first.

This has a http://www.hobbyking.com/hobbyking/s...3_5_960kv.html
(it has the same dimensions of the brushed motor I took out) and a Turnigy 40amp ESC, and I run a Turnigy 2200 3S 30C Lipo battery in it and a 11x6 folding prop with a 5mm spinner. Had a lot of fun with it last year. Caught a lot of good thermals.



I am looking to get this plane from Hobby King, around March maybe. http://www.hobbyking.com/hobbyking/s...dproduct=65978 I am putting the same setup in this as the Spectra has.

Since I am really heavyset, I have to have all my sailplanes electric.

Oh and on that 2830-11 motor I suggest. Someone on another forum suggested a 10x4 - 10x6 folding prop.
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Old 01-11-2016, 03:35 PM
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I know most sailplane flyers hate the idea of any kind of engine on a sailplane, but for me a Gentle Lay is a nice chance of pace from my 40 size pattern and sport planes. For me using a high start is just practicing landings. I have had a lot of fun with my newer Gentle Lady with an OS 10 glow engine but I am looking forward to going electric with one.
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Old 01-11-2016, 03:40 PM
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Originally Posted by Wblakeney View Post
I also had a Gentle Lady from the 80s that I built back then but it sat around for about 20 years before I got it flying. I had a couple of old Cox 0.49s that put on it but had trouble with. I put on an OS .10 but when I redid it and moved the servos to add throttle I did not get the elevator pushrod secure and it crashed. I got one of the newer kits but the wood was heavier and when they changed to laser cut the parts fit was not as good. The kit I am building now is one of the original kits that I picked up on Ebay a few years ago for about $30 dollars. I like Aquila1954s set up since I don't want to much that much into it.

My Lady from the 1980s
Nice color design.
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Old 01-12-2016, 04:29 AM
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Not sure if you remember it or not but there was an electric version of the GL called the Electra. It came with a huge can motor that, along with the recommended battery pack, weighed in at almost 16 oz. I have an unbuilt all original kit that I'm thinking about building, one day anyway. Getting back on subject, here's a post from BMatthews on recommendations for my Electra:
The overall weight for an Electra or Gentle Lady is best kept to 30 oz give or take a couple. It truly is a model where "lighter is righter" due to the choice of airfoil section. It's definetly not what you'd call a windy weather penetration model by any stretch.

At 32 oz or two lbs it means that you can achieve a "nice" but not rocket like climb with as little as 50 to 60 watts per lb. Or 100 to 120 watts total. On a 3S Lipo pack at 11.1 volts that's a mere 120/11.1= 11 amps. At this power setting the model would climb at or just a bit faster than it's normal gliding speed with an angle of climb of around 40 to 50 degrees.

For the heck of it lets "overkill" a little and go for a system that'll run at 70 watts/lb or a total of 140 watts running. From the Electrafly Rimfire series the Rimfire 400 looks pretty good with a continuous power rating of 160 watts and a burst at 220 watts. So with any sort of airflow around the motor it'll run cool at 140 watts. Now 140 watts on a 3S pack will pull around 12.5 amps. A 1250 mah pack will thus provide 1/10 of an hour of run time or 6 minutes. At the sort of climb you'll get with this setup at 140 watts this will easily give you 3 to 4 climbs up to around 400 to 500 feet and leave lots of power for running the radio gear. The good news? A setup of this sort will weigh in at 1.9 oz + 4.5oz = 6.4 oz total in a model that really cares about its wing loading.


This was edited to reflect all information relative to the GL and remove some that was based on the original weight given for the Electra that wouldn't apply. If you want to read that thread, it's at Need Some Advice On A Goldberg Electra

One other thing to consider is that this post was made long before the advent to LiFe packs. With a LiFe pack, your flight duration could be much longer and/or with more climbs than with a Lipo pack

Last edited by Hydro Junkie; 01-12-2016 at 04:40 AM.
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Old 01-28-2016, 01:39 PM
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Finally got all my parts. I went with the D2830-11 1000kv motor, Plush 30 ESC and Turnigy 1.6 3s battery. I just did some bench runs and got 6 minutes at full throttle and 17 minutes at half throttle. That should keep it in the air longer than I care to be flying. I don't like the idea of a BEC on sailplane since no telling how long you will be up after the motor stops. I just took a servo extension and cut the red positive wire so can use an external receiver battery,

Originally Posted by Aquila1954 View Post
Hi;
Well I don't have a Gentle Lady, but I am building a Riser 2 Meter Sailplane and this is the electric system I am going with. Motor: http://www.hobbyking.com/hobbyking/s...ess_Motor.html

ESC: http://www.hobbyking.com/hobbyking/s...ontroller.html

Battery: http://www.hobbyking.com/hobbyking/s...dproduct=58837

Programming Card: http://www.hobbyking.com/hobbyking/s...ming_Card.html if you want to put a brake on the motor so that that folding prop will fold. Sometimes the air will continue to turn it creating a drag.

Watt Meter is a must. This is the one I use: http://www.hobbyking.com/hobbyking/s...dproduct=34137
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Old 01-29-2016, 02:32 PM
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Wblakeney,
In lieu of an external receiver battery you might try Scorpion Backup Guard. This device functions as a battery backup in case the BEC fails for some reason. If the BEC or any other power source fails then the Guard kicks in similar to emergency lighting unit found in schools, hospitals, etc. The unit supplies regulated 5 Volt power with a 10 Amp peak from a self-contained 2S/500 mAh Lipo to your receiver and servos for continued flight but without the E-motor. It plugs into a spare receiver port or can be connected to the receiver via a Y harness. It is about the size of a package of stick chewing gum and weighs 1.2 oz or 38 g. The price is about $ 25 USD and available from gravesrc.com. I use it on all my e-sailplanes and EDFs to prevent a flyaway or crash.
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Old 01-29-2016, 05:16 PM
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I will look into that. One thing I found when bench testing every thing is that the motor started if I turned off the TX, not something I would normally do but I wondered about it., A little checking showed that my throttle fail safe was set at 26% so it was normal for the motor to start on loss of signal. I reset it to 4% and that stopped it.
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Old 01-30-2016, 01:34 AM
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Glad that you found the throttle fail safe glitch on the bench instead of at the field. My Gentle Lady was built from the original Goldberg kit about 30 years ago and is still flying. I designed a simple power pod mounted atop the wing and used an Astro 075 can motor powered by the then-new Sanyo 800 mAh NiCds. It flew-just barely, but I was able to achieve several "All Seasons" patches by logging flights every month of the year- in Michigan. Electric guru, Keith Shaw gave me a Leisure 05 motor which improved the flight performance somewhat. Recently I installed a 3S 2200 mAh LiPo and the Scorpion Backup Guard further weight reduction. The power pod works well in snow covered field conditions- ROGs are even possible on a hard crusted surface. Incidentally, the preferred prop for my setup is an 8 x 3 1/2 wood prop and the design is flies best in relatively calm conditions-less than 10 MPH. Good luck with your Gentle Lady.
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Old 01-30-2016, 01:58 AM
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Correction on the current battery on my Gentle Lady- I use a 2S 2000 mAh Lipo, not 3S. I once tried a 3S 1100 mAh Li Fe and smoked the ESC and some of the wiring. You should be OK with a 3S if you're within the wattage/current limits of your motor/ESC. A quick check with a watt meter would be helpful.
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Old 01-31-2016, 04:28 PM
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I have got to glue the firewall in. Did you use any down or right thrust. You used the term glitch but this is a case where at first you thing there is something wrong with the ESC but actually every thing is performing just as you programmed it. Though you don't realize it is programmed that way.
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Old 02-01-2016, 01:49 AM
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Glitches can be mechanical, electrical or mental.
On the GL firewall I would add a couple degrees of down and right thrust. If possible design the mount so that you can shim the motor a few degrees either way. Note that my GL has a power pod mounted atop the wing and I have about 3 degrees of UP thrust designed in. The up thrust is to counteract the pitch-down effect at the initial launch due to the location of the power source. I also fly an Electricus sailplane with a nose-mounted motor and a couple degrees of both right and down thrust are incorporated with this design. Reaching (way) back to my free flight days, motor thrust settings are applicable to the initial stages of flight or until the aerodynamic forces prevail.
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Old 02-01-2016, 12:20 PM
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One thing to keep in mind with the GL or Electra is that the airfoil used and the way the covering sags between the ribs does not like a heavy wing loading. On the other hand the airfoil and wing really floats in a lovely manner when the wing loading is kept on the lighter side. Carl was a dyed in the wool free flight sort of guy back when he designed the original GL and that shows by his choice of airfoil.

This is one of the reasons why the original Electra with can motor and heavy NiCd battery pack was such a dog. The whole essence of what made the GL such a joy to fly was totally lost due to the rise in the wing loading.

But that was then and this is now. With today's motor and battery options we can produce an electrified GL or update an Electra and actually have the total flying weight MATCH the original setup. This is mostly due to the fact that the original GL NEEDS at least 4 oz of nose weight. Most of this came from the 4xAA flight battery used by the radios of the day and the rest came from somewhere up to a couple of oz of lead shot as required and based on the weight of the wood used in the tail surfaces. With today's motors and battery packs we can swap out the old 4 oz NiCd 4xAA pack for the motor and Lipo and sometimes even come out lighter. Particularly if we select the wood for the fuselage and tail surfaces to be in the lighter 6 to 7lb/cu-ft density range. And that is basically the lighter premium stock you'll find at a better hobby shop.

With care it should be quite doable to produce a nice flying and good climbing GL running with around 70 to 80 watts per lb that hits the scale at around the 20 to 22oz mark.

One of the lighter park flier films for covering will aid in this. The classic films such as Monokote and Ultracote are surprisingly heavy. You stand to save a good 1.5 to maybe even 2 oz if you start with a parkflier film of some sort.

Taking this even further I just recently learned about Fibafilm from BP Hobbies. https://www.bphobbies.com/view.asp?id=V037439

It's supposed to be much like the old style Micafilm. I've not seen any of it yet but if it's more like the old original Micafilm then it would have much the same appearance as clear doped coloured silkspan. And on a model like the GL that's something worth doing. If it's more like the last of the Micafilm where it looked like fogged on paint then I'd want to pass on it in favor of something else. I simply don't know because I haven't seen the product in person.

Either way though I'd still suggest one of the lighter park flyer films for the basic wing and tail covering. And for trim if you can find Solarfilm I think you'll find that the low heat needed and softness of the film makes for a nice option for trim work. It's also a much lighter film than the usual Monokote and Ultracote. But it's SO flexible that I would not use it for overall covering. The open structure of the GL needs the skin stiffness of a good low stretch covering to aid in avoiding it twisting in the air.
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Old 02-01-2016, 12:59 PM
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After I crashed my 1980s GL, I got the new kit off Tower Hobbies and noticed they used much heavier balsa especially the ribs. I put on OS .10 on it and it did fine. The one I am building now is the original die cut kit with much lighter wood. Without covering I am coming in at just under 20 ounces with all the equipment
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Old 02-01-2016, 02:06 PM
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BMatthews/WBlakely,
Just for grins I weighed my 30+ year old Goldberg GL, kit-built, and the All-Up Weight (AUW) was 34 oz. This included the Monokoted airframe, Leisure 05 Pattern Motor on a power pod, 8 x 3 wood prop, 25 Amp brushed ESC, JR 6 Channel FM receiver, Kraft KPS-30 servos, Scorpion Battery Guard, Venom 2S 2000 mAH Lipo and some nose ballast. This combo is a bit on the heavy side but still flies well in light-to-moderate wind conditions. No doubt it would fly better if lighter.
The original GL/Electra airfoil is derived from Goldberg's free flight designs. Note that RA Cores, in Southbridge, MA offers foam cores with spars and sheeting in the modern SD 7037 or S 3021 airfoils. Cost is $35 plus $ 10 shipping. I'm building up a modernized GL with a V-tail and a SD 7037 full-house wing to be named the "Wicked Lady". Hopefully it will fly later this year.
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Old 02-01-2016, 04:10 PM
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Art, something I've always thought could be fun is a GL but with the AG airfoils used on Mark Drela's Allegro Lite. It's still all balsa that way and the builder could opt for Mark's hella strong carbon spar buildup or go for an easier spruce spar "high start and light winching" wing to skip the advanced composite aspect.

But at that point I sort of figure that with the extra cruise speed this would all give that I might as well oval shape the fuselage with a nice upper nose block and triangle stock in the corners to allow shaping. And then make the fuselage more skinny to hold the modern gear... and on... and on.... and suddenly it doesn't look at all like a GL anymore.

.... I'm weak that way when it comes to "improvements"
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Old 02-02-2016, 01:56 AM
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BMatthews,
My "Wicked Lady" will retain the look of the GL/Electra except for the V-tail. I was seriously debating on a conventional tail but the V-type just grabbed me one day and it was built. An E-sailplane does not require the strength of a high start or winch launched wing. My Electricus, built from Larry Jolly's plans, features the rounded skinny fuselage and sports an E-205 airfoil- a big step up in performance from the GL/Electra. I've done loops and rolls with the built up Electricus wing with no problems whatsoever. So many choices-not enough time to try them all. I do appreciate your comments though.
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Old 02-02-2016, 07:53 PM
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Art, I'm sorry if my post came across with a bit of "my idea is better than your idea". That certainly wasn't the intent. I was just tossing out my own concept that has fluttered through my own mind on occasion. Since you were looking at a GL based mod I thought it might be fun to also toss out some other options.

I'll be looking forward to reading your build and flying thread on your Wicked Lady project. You just be sure to "meet our expectations" by posting when it happens. Deal?
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Old 02-03-2016, 03:35 AM
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BMatthews,
No problem and again I appreciate your concepts on GL upgrades. My "Wicked Lady" is currently on the back burner until other projects are completed.
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Old 02-03-2016, 03:58 PM
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I take a slightly different view on wing covering materials, and some of the weight savings people have quoted are over the top for a 2M sailplane.

Monokote varies from between 62 and 81 grams per square meter in the opaque colors while the transparent Monokote colors run around 57-58 grams per square meter.

In comparison the opaque Coverite Micafilms run between 35-40 grams per square meter, while the transparent colors are in the 25 gram range. Light silkspan and tissue papers are in the 20 gram per square meter range, so it doesn't get much lighter than that.

On a model like the Gentle Lady with about 670 sq inches of wing area, times two for the top and bottom plus some added area for the tail surfaces and fuse, you're probably in the neighborhood of 1500-1600 square inches, or around 1 square meter in covered surface area.

Which means you're saving about 20 grams with one of the lighter colored non metallic, colors or a transparent color Monokote compared to an opaque Micafilm cover, and about 25 grams if you go with a transparent Micafilm. That's all of .7 to .9 oz in weight saved.

There is however no free lunch, and the cost of using a lighter covering that does't incorporate it's own adhesive is in having to apply an adhesive like balsa rite to the airframe first. And, in some cases the film won't offer the same structural strength.

That's not a real issue on a park flyer and lighter is probably better. However on 2m or 99" sailplanes with light, open wing structures like the Gentle Lady, I've encountered problems with tip flutter if I let the speeds get too high when I've used light covering films, where it's much less of a problem with Monokote.

If we're talking about a D tube wing design where you've got a fully sheeted wing structure ahead of the main spar, such as on a Bridi Windsurfer, then covering is less of an issue as the structure resists the torsion loads a lot better, or at least the structure cycles at a much lower frequency.

-----

I'm also not in the school of thought that feels a properly sized high start will pose any particular problems for even a light weight wing - provide the covering is doing it's job to add some rigidity to the wing. If I'm in doubt, or if the wood for the spars feels a little more flexible than I'm comfortable with, I'll add some shear webs.

The speed on a high start launch is after all still controlled by the elevator as any excess thrust is converted into a higher angle climb. If you add in too much "up" trim, it'll start to wallow from side to side and unload itself as the wing roots stall, so it's a self limiting process where the wing stalls before it breaks.

Of course, that assumes the thumbs aren't being operated by an idiot, as if you push the stick forward on the launch it will unload the wing and accelerate, and it's the excess speed that will cause the tips to start fluttering. Plus with excess speed you can also add enough back pressure on the stick to over g the wing and cause a failure of the wing spar. The same thing can happen with an electric as well, as too shallow a climb angle for the power being applied will result in excessive speed.

With the 05 motor, heavy 1200mAh 7.4v Nicad pack electrics of 20-30 years ago, like the Electra, GL or Sophisticated Lady with a power pod, it was more of an issue as the climb angle was pretty flat and the climb speed needed to be comparatively high due to the weight. And once you powered off at altitude the heavy weight would result in the glider picking up speed in a hurry if you lowered the nose and you could quickly reach speeds where flutter and over g'ing the aircraft were possibilities.

In those cases (as well as in unpowered sailplanes with open structure wings where I wanted to use ballast for better penetration) I've not only added shear webs all the way to the tips, but also modified the upper surface of the ribs to accommodate sheeting the upper surface of the wing ahead of the main spar and adding cap strips behind the spar.

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So...the short story is I tend to stay with Monokote and accept an extra .7 to .9 oz of weight in exchange for the ease in covering and the greater rigidity on an open wing structure. I've seldom found conditions where that slight extra weight evenly distributed across the airframe caused a problem, and in many cases, in anything other than no lift conditions you're adding weight anyway if you've got any kind of breeze, so it's a wash.

Even in cases like the first generation electrics, the extra weight of Monokote was a fairly small percentage of the total increase due to the electrics, and you needed the extra strength. The weight problem was such that you weren't going to resolve it with slightly lighter covering, but the extra strength was nice to have. With those same planes today, weight just isn't much of an issue as the radios, motors and batteries are smaller and lighter, and they are largely replacing the 500 mAh receiver battery and 2-4 oz of lead weight you needed to put in the plane anyway to establish the proper CG.
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