View Full Version : Converting Thermal Gliders to Electric Power

Sky Sharkster
02-27-2006, 07:18 AM
Got a Gentle Lady stashed in the garage? Is there an Olympic in your attic? A Flinger in the basement? Then this thread is for you!
We'll be talking about converting thermal duration (TD) gliders to electric power. No winches, Hi-Starts or dislocated shoulders. Hit the throttle and go! In a previous thread (Getting Started In Electric Powered Gliders) there's suggestions for E-Glider ARFs and Kits; Here we'll help convert existing TD gliders, regardless of age and condition (within limits).
To start, we'll focus on two common sizes; 1-1/2 meter and 2 meter gliders.
The 1-1/2M (59") wingspan gliders are (were) usually hand launch gliders, and lend themselves well to the Speed 400 size direct-drive motors. In most cases the fuselage is too narrow to fit the battery. If the wing and tail surfaces are in good shape (maybe a re-covering job with a new super-light transparent film?) it will be well worth it to build a new fuselage. On a clean sheet of paper, lay the spinner, motor and battery in a row. Draw a fuselage shape, similar to the original but large enough to accomodate the new components, around the existing wing location, tail moment arm and tail location. The nose should end up the same length as before, the battery will be (mostly) under the wing. The fuselage can be either taller or wider (or both) than the original but do try to maintain the wing/stab angles and locations. A bit of strengthing under the battery compartment and around the motor is a good idea, 1/8" square balsa in each corner should do it. Add a spot for the receiver and servos. The ESC can either sit on top of the battery or behind it. Now blend all into a nice smooth aerodynamic shape and you're halfway home!
A couple of decisions before you begin cutting balsa; Wing held on with rubber bands or bolts? Battery hatch or remove wing to access battery? I like the bolt-on method, a 3/16" dowel at the front and (2) 4-40 nylon bolts at the rear. If you go with rubber bands, here's the time to draw in the dowels and make sure they clear the electronics. If using a hatch, draw in the location now and leave room for a couple of doublers or cross-pieces at the front and rear of the hatch area.
Many of the HLG's used 1/16" balsa for fuselage sides; I'd suggest you go up one size to 3/32" balsa for the E-conversion. The (conversion) weight increase will be putting a substantial load on the fuselage, especially during landing. Hard nylon "glider skids" are a big help, too.
From here it should be a pretty simple build; The few bulkheads are easily drawn using the height and width at key locations like wing front and rear, the firewall shape should be a near-match for the spinner (30mm) made from 1/16" hard (not "lite") plywood drilled to front-mount the motor and the rest will be the same as the original glider build. I've listed my recommendations for the power train, this is the inexpensive route but a brushless motor and Lipolys would work, too! Most of the listed items are available from Hobby-Lobby.com.
Motor- 6.0v Speed 400
Prop- 6" x 3" Graupner CAM Folder w/spinner
Battery- 8 cell 600 mAh NiMh
ESC- 15A-20A brushed
Servos-Micro, 5-7 grams each
RX- FM Dual conversion Full range
That's about it for the 1-1/2M conversion, next we'll work on the 2 meter gliders.
Good Luck and find a thermal!

03-21-2007, 05:17 AM
How did the build go?

Sky Sharkster
03-21-2007, 01:38 PM
Hi Ed, I've made this conversion to a couple of HLGs, most recently to a Dynaflite "Skeeter". With a direct-drive 400 the climb takes a few seconds to get going, then it moves out pretty well. Climb altitude is better with a gearbox, later I tried an MP Jet planetary 3.3:1 and 9" x 6" folder.
But the BEST combo (as you might expect!) is a Hacker B20/15L with 4:1 Maxon GB. Also tried 3s x 1350 LiPOs. What a rocket! This combo was also much lighter than either of the brushed systems. At $150.00 more, I might add.

03-21-2007, 04:29 PM
I just got done converting my Gentle Lady to a motorized glider for our club competition this spring/summer. I used a no-name outrunner with specs nearly identical to a Eflite park 480, 10x6 folder, electron 6 RX and power it with a 3S 2100 pack. I haven't flown it yet but a friend using the identical setup in a similar plane and the performance is impressive.

I'm putting my high start up for sale :D

Sparky Paul
03-21-2007, 06:31 PM
These are 2Ms converted...
Power varies... SpeedGear 480, Speed 500, AXI 2820.
7 and 8 cell Nicads, 3C Lipos
And two poopy ducted fans..:)

03-21-2007, 07:28 PM
Ducted fans? Do you have a photo of that set-up?

Sparky Paul
03-21-2007, 10:34 PM
The motors/fans are from the GWS B-2.. which in standard form could not takeoff.
I put them on the Gentle Lady to irritate the jet guys with their real ducted fans and turbines..
"Launching my jet" I'd yell out..
It performed modestly.

03-21-2007, 10:56 PM
That's great! I love the launch call.

03-22-2007, 09:59 PM
Hi All,

I recently converted my 10+ year-old Gentle Lady to electric using an E-Flight 400 and a 10/7 folding prop. It works great! Flew it a couple times last weekend and actually caught a thermal (with Ron wispering "turn right, turn left"). Not bad for March here in Colorado. The coolest thing is that it sat and sat waiting for me to untangle and lay out the penalizing high-start for that exciting 80', 1.5 minute flight... Now I just hit the throttle and off it goes! It was so nice to scrape off the layers of dust and actually fly again!


Sparky Paul
03-25-2007, 05:32 PM
Having that built-in thermal/hi-start is handy. :)
My latest attempt at building a Gentle Lady..

03-26-2007, 05:08 PM
Here's my old Dynaflite 2X4 with a power pod. Uses a well broken in GWS SS motor 300c with D gears and 9X4.7 prop. I am useing 3s salvaged lap top li-ions for power and Hi-Tech 555 RX and servos. I need to get a folding prop for it, way too much drag. Have been flying it for about a year now, thermals well or just cruises around if you want to. Get it up to altitude and then throttle back and you get 25-30 minute flights. Best part was no money invested, used all on-hand stuff
Happy Flying