I just received what I thought was going to be the build version of a Bird Of Time 3M sailplane. Turns out it is an ARF... A very nice ARF at that. The Fuselage is fiberglass with what looks like a reasonable hunk of metal in the nose. Anyway, I would like to convert it to electric and I was thinking of using an E-Flight 400 outrunner and a 3S 1320mA pack with a folding prop. I don't need incredible performance, just enough power to get up into the cleaner air here in Denver. The box sez 60oz, but that ofcourse will change. Whada ya think? 150W-ish? Also, I was thinking of retro fitting spoilers, but that may not be necessary. Dunno.
I'm guessing I would lop off the nose and install a bulk head and mount the motor from the inside. Add a spinner to the prop to replace the removed nose portion. Weight and balance might be an issue, but if there is as much weight in the nose as I think there is then it might not be such a bad swap.
I've never used a folding prop... Any suggestions? I'm thinking the CC speed controls can be programmed for a hard stop. Is this enough to get the blades to actually fold back?
What does the kit weigh out of the box? I would suggest at least 50watts/pound for the climb performance you are describing. If you can post at least an approximate weight I think we can help on the specifics.
Franny, I also went the same route. My ARF BIRD conversion began with sawing off ALL that lump of steel in the nose, allowing for some right and downthrust, and adding a ply bulkhead to mount the outrunner, which is forward of the bulkhead to restore the nose length. It required no additional lead to rebalance.
I made another nose skid blister from balsa and glass cloth, since the original gets cut off with the nose section, saving the belly from a lot of landing abrasion and helps keep the motor out of the dirt on landing.
Power is a Python 200HT outrunner, 200 watts. Anything less would not be real impressive. Battery is a ZAGI Hi Rate 1800 NIMH 8 cell, all the way forward. Prop is a Turbo Spinner (with a cooling hole in the nosecone) and a 14-10 CAM folder. The ESC is a Jeti Advance 30Amp. The ESC brake function is very effective and I have used it for all my E Sailplanes. It is an excellent feature- folding cleanly and restarting effortlessly.
It climbs ok but is not a hotliner- but weighs no more than the pure glider setup. I suggest no less than 200 watts- I actually peak out at a bit more than that!
I had considered using my two 2aH lipo 3 cell packs but they were a bit large for the space in the fuse and would have required extra weight to balance. The NIMH pack is good for just a few climbs but it stays up so well on a single climb that there is plenty of time to charge the other pack.
I had originally used a HS81 servo for the stab- but the gears stripped. I changed it to an HS-81 Metal Gear servo and all has been well since.
I love the way it rises in lift and is so easy to see, so graceful to turn, so willing to soar. I like it better every time I fly it. It has given me some very long enjoyable flights. The glide, handling and sink rate are very satisfying. Landing is a bit of a bear so I will be adding spoilers this winter. You will like this one!
Here are my conversion detail pix. The lexan cover (painted white from the inside) really cleans up the nose section. It was made from a paper template trimmed to fit.
The scoop underneath was carved out of balsa block and feeds air to the cooling hole in the firewall for the batteries and ESC while providing protection for the motor.
The landing blister was balsa block carved and sanded to shape, glassed, painted and epoxied.
It was a thrill to find that with the small NIMH pack and motor/prop, it weighed exactly what the glider did with all that dead weight. I have 2 worn hacksaw blades that prove it is STEEL, not lead they have cast, and epoxied into the nose of a glider that could not self launch. Now that weight is put to far better use than merely balancing the tailfeathers! Penalty for adding electric power? None!
Be sure to cut the weight off the nose just aft of the metal with 5 degrees right and 5 degrees down - not cut thru it like I tried at first, thinking I might have to keep some of it. Forget that!
I relocated the rudder servo to the next to last bay in the fuse to allow any size battery pack to be used with a lot of fore/aft room for balance in the nose.
One useful feature is that the fuse balances in the same place with the wing on or off.
The small ZAGI 8 cell 1800 HiRate NIMH I use is made for twin Speed 400 foam delta speedwings and is the lightest battery possible to use- since it balances with it all the way forward against the firewall.
This is a very worthwhile project and a great ARF that is beautifully prebuilt. If they included spoilers and an electric option they would sell a million of them to 2 meter glider flyers who want a big glider that is easy to fly without a lot of expense- with the unique wing design of the Bird. Add the fact that electric conversion has no weight penalty and cutting into this beauty is well justified. Until they offer this gorgeous glider with power and spoilers, we will make this the perfect powerglider ourselves.
The idea behind the unique BoT wing planform is that altho the center section is the hardest working part of the wing, the airflow there is relatively stagnant. Increasing the aspect in the root section improves that. The side benefit of carrying a larger chord outboard with the BoT's unique 'trailing edge cut' is to provide more area to the heavily tapered tips which would otherwise be prone to tip stall in soaring turns. Simple elegance.
My EBoT showed no sign of being overly susceptible to tip stall- and soaring turns are a joy. Rudder/Polyhedral works perfectly for lateral control and the full flying symetrical foil stab couldnt be cleaner.
I love the workmanship and Monokote covering- which I will soon cut into to add spoilers so I don't need to worry about losing it to the lift- or the end of the field trying to land a sleek glass slipper that wants to do everything but land...
So, are you pretty happy with that motor? There are so darn many to choose from... Oh, did you have any problems with cutting the fiberglass? Did you tape it up pretty well fiirst? This may be a job for Mr. Dremel. I really am psyched about this project! I have adored from a far the BoT for years. The kit looks to be of very high quality. I too will be adding spoilers as my field isn't super huge and model in the RealFlight sim acts like it has an anti-grav unit installed
Thanks again for all int great info! I'll let you know how I progress...
Yeah, Franny, the motor is fine- and there are a lot to choose from! Anything 200 watts or over will climb nicely- 300 watts would be a thrill to behold! I like the outrunner's simplicity since you can run a larger prop without a gearbox and its efficiency losses, weight and cost. Simplicity is its own reward- and larger props work much better.
Run the biggest prop you can and enjoy the gain in efficiency with larger disc area props. I have a 14"x9.5 folder and have a set of 18"x 10 for 6 cell use with the Marathon 200 HT- which I had misidentified earlier.. Thank goodness for labels!! LOL
I borrowed the ESC for my Queen Bee power conversion so the Bird is on vacation for a month or so! A set of Graupner spoilers will be accompanying the ESC on my next order just in case its gonna be Winter for awhile yet...
I used a hacksaw with fine teeth on the fuselage and the glass was just fine, wrapped in masking tape, cut in a miterbox with the fuse blocked in position.
The motor was mounted to the left of center on the firewall so the center of mass of the motor was in line w the fuselage, considering the 5 deg right and down thrust angle built into the firewall.
The lexan cowling strip cleans up the nose area- not as sleek as the original nose but still reasonably clean for a big blunt motor with serious cooling needs and power to spare!
Anti-Grav? I thought it was hydrogen in those gigantic wings...
I think it looks like a bass swallowing a motor... what it lacks in aerodynamic perfection it makes up for with character!
The mirror chrome finish on the motor is a nice touch...
Thanks for the link, Bill. I didnt know there were other versions of ARF BoTs out there! The aileron version is strange with the flat wing! I am perfectly satisfied with polyhedral/rudder control and its inherent stability- even if it throws a bit of lift away with those upbent wings.
Well, I finally finished the conversion. So, here is a run down:
I sawed off the nose and left about 3/8" of the steel nose plug for a bulkhead. The reasoning was two fold... I figured I would still need a little extra nose weight (I was right) and also, that seemed like a good diameter for the spinner. I ended mounting the AXI 2820-10 inside the fuselage. That was interesting, but I managed to get the steel firewall all drilled out. Steel is harder than wood. Must of forgot that somewhere along the way Anyway, that left me the problem of cooling. I didn't want to add some huge scoop that would just add drag when I only need it really when the motor is running. Then it dawned on me... I could hinge the canopy and add a servo to the throttle channel and have the front raise and lower with the throttle. What do ya think? It turned out pretty cool. At full throttle, the canopy sticks up about 3/8" and when the motor is off, it is all the way down. The little set screw thingie is easy enough to take off and then I have access to my battery. I am using a 3S 3300 mAh Li Poly pack that fits in nicely. The other mod I did was to add magnets to the outer ribs in the wing panels so they will stay together. I actually used two magnets instead of a magnet and a washer for twice the holding power. I probably will augment with some scotch tape just to be safe. That’s about it... I'm running a Gruniper 11-6 folding prop. Maybe a little small for the motor, but I don't want things to heat up. I ran it for several minutes and the motor got a little warm, but the battery was cool and the speed control was fine as well and that is just a static test. I might think of putting the canopy servo on it's own channel and mixing it with the throttle so I don't forget to open it. Dunno... I'll have to see how it works in practice. I’ve included some pictures. I hope to fly it maybe Sunday? We’ll see. I have a late night gig Sat night and then there’s the weather. Holy Cow that is one big bird!
Ya know... I don't know... I thought I was biding on the kit version as I thought it would be easier to modify but they sent the ARF instead and it was so nice I didn't make a stink (also more expensive). There was a bad crack on the top of the fuselage starting at the front of the canopy, but I was able to patch it with epoxy and cloth and touched it up with Krylon H2O which was an amazing color match. I think I'm somewhere around 250W-ish. Neat kit. Well made and actually covered with Monokote. great quality and the ARF has a fiberglass fuselage - pretty sweet. All up weight is 66oz, so not too bad... I think the kit calls for 60oz. I'll let you know how it flys...
No kidding! It is a great Bird for the money! That motor of mine turned out to be Russian junk and it ate the bearings!
I'll find another outrunner and redo the lexan motor fairing to smooth it in if need be.
I got 2 sheets of coroplast from a sign company and used part of one to make a coroplast carrying case with velcro closures to keep the Hangar Rash at bay! Plenty of room for the extra NIMH battery and a roll of tape for securing the outboard wings or even the tx and charger if you wanted to!
This is one bird that requires some serious thought if you wanna display it assembled! It is a MOOSE. A magnificent moose, like Bullwinkle!
Hello Guys and Gals
I hope your still reading / reviewing posts on the Bot...I've jumped in and purchased one with the intent of making an e conversion. The motor I've chosen( st models- 2908-10) shows 240watts on the watt meter with a 10x6 graupner folder. 25/35 amp brushless speed control and I've made a 4200 ( 2100mah x 2 in parallel) lipo's from apogee)I mounted the pair -one on top of the battery tray-one underneath the tray..lifting off with the canopy...spring latch system added to the canopy. I cut the nose off with a diamond chipped dremel wheel with my dremel. I marked the fuse after measuring the depth of the steel into the fiberglass nose of the fuse.Used masking tape around the glass nose as not to chip & flake the glass. Worked well. I've epoied a ply firewall to mount the outrunner on. When I'm finished i can post some pic's if anyones interested.
Hi Franny...I took all the steel out..gone. I severed the fuse right at the rear of the steel in the fuse. It took me a week to get enough nerve to cut the fiberglass...I kept thinking if this doesn't work out I've ruined a beatiful plane. I finally did it and we are moving ahead.The motor will mount on the outside of the new plywood former/firewall. Cooling for the motor will be a non issue... if the drag from the motor is too great,I'll enclose it and hope the electrics will cool enough.I'll need a small scoop to vent/ cool the batteries & speed control. I do like that idea of hooking up the canopy to the throttle servo.quite inovative.I thought after I read this that I'd use my own canopy as an airbrake( taken from the servo to canopy idea. I'm thinking of installing an airbrake to help bring this bird down , at least before it gets to Denver ...I'm at work on lunch right now so when I get back home I'll start taking a few pic's to post.
Awesomke idea for the cooling, Franny. I hope I can remember it for when I build my first big electric sailplane. Thanks for sharing. Also, that motor should not let you down, it should have plenty of power. It may be worthwhile thinking about a 12 X 6 if you batteries can handle the amp draw.
I hope that's soft water......
Meddle thee not in the affairs of dragons, for thou art crunchy and wouldst be tasty with ketchup.
Welcome, Don- and congrats on finding the nerve to cut the beak off the Bird! Yeah, I remember the same feelings before the nosejob (am I having funnn?) but it went very well.
I used the forward mount but I must say I like Franny's internal mount. After burning up an internal Speed 400 once a month in my little Ascent I felt it was safer to let it breathe outside so I could push it hard on the climb. Keeping the motor forward let me forget about adding noseweight to balance it but its not the cleanest thing in town with the motor out in the breeze. Oh well, something had to give!
You're gonna love this one!
Denver? That ain't so far- Turn at Denver then glide in on final- or mount spoilers!
Well..home from work now and catching up on the posts. Thanks for the welcome Tw and Franny .I'll get the camera going here soon and post a few picks. Probably wont take too long as I've cleared the build table and I'm focusing on the Bot to get ready for a break in the weather & a first flight on the BoT.Now,Keeping my motor cool was first in my requirements so I chose the drag penalty of keeping things mounted out front and thought this would be an easier mounting choice. I also thought of spoilers too but being an arf and having to dig into the main spars and removing covering isn't high on my list. I'll have to see what the air breaking will do before we tackle that mod.
A thought occurred to me Franny, I could leave a message under the canopy incase the BoT strays a little. Something like when people used carrier pigeons. LoL...anyway, hitting the hay now and we'll hit the build table in the morning.
Tomorrow will be a no fly day. It's predicted to be minus 20 with wind shield factor of minus 30 .20c below presently this eve.For those in imperial measure..minus 20c = minus 20 F ....and i'm thinking I should have stayed 3000 kilometers to the south where I was last week at this time, in the Carribean Islands...That's cold even for us Canucks!
I have just gotten my new BOT together - maiden flight tomorrow
Thanks to Franny's description and pictures, I got up enough nerve to cut the nose off and put in the motor. From a link on RCGroups I found pictures in the October issue of Soaring Digest that showed how to add spoilers. Thanks to a another local flyer who showed my how to use MonoKote, I recovered the plane in colors my older eyes can see at thermal height. A big thanks to all who have contributed to this thread and convinced me to get the BOT.
What it has:
Mega 16/15/3 in a Kontronic 5.2:1 planetary gearbox
3S2P MaxAmps 2100 HV lipos
HS-81MG for rudder servo, HS-65 for elevator servo
CC45, Hitech 555, Turbo Spinner and Aeronaut 15x8 folding prop. (16x10 on order)
Spoilers - Hand made 0.75oz glass/30 min epoxy blade held in place with rare earth magnets and lifted with HS-55 servos in a Y-harness.
AUW = 65 oz.
With the current prop MotoCalc says 66 oz of thrust @ 40 mph tip speed from 30A gives 1100 ft/min ROC. With the correct 16x10 prop it should give 78 oz of thrust @ 46mph at 40A with a ROC of ~1500 ft/min.
It should get about 7 min of WOT which is about 8 to 10 climbs to winch launch height. While not LMR performance, it should be entertaining
It was really too windy for a maiden, but I just couldn't resist.
Spool up the throttle, toss it into the air and it climbed right up - a little too much "up" because it seems that the three degrees down I put into the firewall is not nearly enough. Adjust the elevator/throttle mixing by putting in LOTS of down and it smoothed right out, climbing just fine on about 70% throttle. It may take a little adjusting the total amount of movement and size of the initial dead zone being mixed in before it will be neutral, but that is just a matter of dialing it in. The smaller 15" prop is very adequate and I might just keep it to decrease the current draw and increase the number of lifts. It needs full rates when under power to keep it under control.
Once to altitude and switching to low rates, after a little bit of trimming it just hung in the air...well like a bird; like a gull riding the uplift over the cliffs at the beach. The wind was very gusty from a base of about 6 mph up to 20 mph and the plane would rise and fall with the wind speed, but not make much headway. I could nose it down converting altitude into speed and bring it back to me, but at this weight it does not penetrate very well. We don't see conditions like this here very often and I have a Sleigers Electric Storm that is heavier with a SD 7037 wing that is much better suited to these conditions, so I won't ballast up the BOT. I will just bring the plane that matches the conditions..
After hanging in the air for a few minutes, I tried the spoilers. When they open to 90 degrees, the plane drops like a rock, going nose down about 30 degrees. Three bays long on the spoilers is plenty. Not wanting to take my eyes off the plane to switch the Tx over to the spoiler/elevator mix- without constant correction in the gusts the plane would change direction and roll a little - I brought it in for a nice smooth landing to do the adjustments.
After setting the Tx so I could dial in the up spoiler/up elevator mix on-the-fly with one of the Tx control knobs, I threw the BOT in the air again. Oh no! No rudder control I tried to nurse it to level by hitting the throttle, but no go. It finally rolled over and I could not bring it back, so it cartwheeled into the tall grass.
The keeper on the rudder clevis had broken (it was gone, probably breaking during the initial landing), allowing the clevis to pop off. When testing the control surfaces before the second launch, the rudder worked fine since the clevis must have still been attached, but open. When I asked for hard over rudder to compensate for a gust, it popped off, leaving me with no rudder control. On a R/E plane that can ruin your day.
Fortunately, there is only minor damage. I can feel at one place on the TE on the outer wing panel about half way down the panel where a rib intersects, the glue has popped off, and the sheeting forward of the spar may have broken along that rib. The covering in wrinkled but the spar feels solid. I will cut open the covering and drip in a little CA and it should be fine. This was a mechanical failure that I should have noticed on the pre-flight. I will probably switch to a metal clevis with a locking tab to prevent this from occurring again.
My initial impression is that I like the way this plane flys. It responds a bit slowly to control inputs from what I am used to, but it is a R/E/S 3m after all, so you would expect things to be a bit slower than on my super light 2M aileron plane. I will NOT be using it on windy days, however - without ailerons there is just not enough roll control. Even with what appears to be a very large rudder, the fuse is rather short for the wingspan and thus leverage is minimal, so the rudder lacks control in these conditions. To be fair, it was really too windy for this plane, and I knew it. In calmer conditions it will be a dream to fly.
Great to hear you got your BOT going. Sounds like the little mishaps were minor. I am switching everything over to metal clevises as well - much easier to adjust and a bit safer. I would agree about the winds and slow response to the rudder. I found that as well, but I think, as you mentioned, it was designed for thermaling and not for nuttyness. My BOT is finally on the bench and I have a pair of the "pop-up" Graupner spoilers to install.
Did you have any issues with the main dihedral? Also, how did your color scheme work out? Any flight photos?