Butterfly

Just got a Butterfly motor glider from a swap meet. I have a 25fp OS for
power. Will that be too much engine? What would a good prop to use?
Andy
Reply to
Andy & Carol
Loading thread data ...
Hello, Andy.
I'm going to build a Butterfly, and put my OS .40 on it. Of course, the Butterfly calls for a .10 to .20 sized engine, so mine will be overpowered. Others have evidently flown a Butterfly with a .40 sized engine and gotten away with it, though. I simply could not resist purchasing the engine, and I will also not be able to resist purchasing the plane. I remember reading a post by someone who was able to get a Butterfly to rise off of the ground with a .25 sized engine.
Mike Mandaville
Reply to
MikeMandaville
Unless your field elevation is above 6,000 feet and the plane will be carrying a heavy payload, what is the logic in this power choice? It will fly fine with a .15 . . a .40 will just over stress the airframe.
formatting link
Reply to
aeropal
I thought about a .40, but it just looked too big... I took off a 15 and put in a 25 and like it.... it balanced very well with just a bit of lead.....
Arne
Reply to
Arne
airframe.
Hello, Andy.
If you can find me a sailplane kit with a wingspan which is greater than that of the Butterfly, then I will be happy to purchase it. Eventually, I will be scaling the Butterfly up, at which time I will then have a more appropriate power match. In the meantime, I will be flying.
Mike Mandaville Austin, Texas
Reply to
MikeMandaville
Sorry. That should have been "Hello, Aeropal", since I was actually addressing my remarks to Aeropal this time around, rather than to Andy.
Reply to
MikeMandaville
If you can't find something with more than 99 inches, you're not looking very hard. My 25 year old Legionnaire has 140 inch wing.
Here's a couple of sites a quick search produced:
formatting link
formatting link
And one of my personal favorites:
formatting link
4 inches shy of a 20 FOOT wing.
Reply to
Chuck Jones
Say, fellows, I just realized something. The Bird of Time has a wingspan of almost ten feet. Perhaps this would be a better match for my engine, even though I would probably still be overpowered. Does anybody have an opinion about this?
Mike Mandaville
Reply to
MikeMandaville
Andy,
I also bought a Butterfly at a swap meet and it had an old OS15 in it. This engine is Ok but marginal in windy weather.
Your 25 will be more than ample. I have been very pleased with my Butterfly as it seems to pick up thermals with ease and I have been getting 40 min flights easy. Usually end up bringing it down as either my neck is giving up or I get worried re battery or excessive height. prop size should be about 9 by 4,5,6 pitch for a 25 engine
enjoy
john
Reply to
John Laird
In case it was overlooked, the bird of time is a real non-motorized sailplane and the butterfly is a gas airplane with a big wing.
Not that you can't put a motor on a bird of time, but it is drawing much farther outside the lines than putting an oversized motor on a butterfly. Proceed at your own risk in any event.
P.S. In any event use lightweight radio equipment (servos,batteries,reciever) if possible to compensate for the extra engine weight and put it towards the tail. You might want to build it, hang the motor, and then figure out where to put the radio equipment and linkages so it will balance at the designed CG without adding even more weight just to balance it.
One of the appealing aspects of the butterfly is it's gliding ability, making it heavier with a larger engine (and larger/draggier prop) will of course compromise that. Not to discourage you, by all means give it a go, it should climb like a .
Reply to
Steve Banks
Thank you ,John..I had a 9by 5 on the engine, testing it, I picked up the tail a bit, and snappped the prop,on the cement driveway. I was wondering wether that was a good prop size, and I guess it was. I am having trouble hand launching it. It seems as though it is to heavy, and wont rise, and and hits the tall grass without climbing. My first Butterfly would rise at the slightest toss. Andy
Reply to
Andy & Carol
That's exactly the rig my son learned to fly with. It will fly the batteries dead at 1/4 throttle, and will climb like a c-gas FF model if you want to power up.Big, vertical spiral climb. It climbs well at 1/2 throttle. You can overload the wing if you try to get aerobatic at high throttle settings--I know that for a fact. You can easily hand launch it with that engine, and not have to heave very hard. Great set-up. BTW-that was at 3500' MSL. It performs a little better here in Texas at 800'...
Reply to
Roger G
Andy, Saw about 20 of the Butterfly IIs scratch built over a two year period from RCM plans. About 15 of them flew. All well with OS .20FPs 9X5 props and a Higley heavy hub for balance.. The scratch built BFs are much lighter than the currently kitted BF by DynaFlite. A friend built the DynaFlite kit and it was a bit underpowered with the OS .20FP therefore he switched to the OS .25LA and a 9X6 prop. It flys extremely well now. My own scratch built BF II is powered by an OS .26FS with 10X6 prop. I highly reccomend this power combo. As well I am in the process of converting a second BF II into "E" power using a brushless Astro 020 w 4.4:1 planetary gearbox and matching speed control. Planned prop is 12X8. Calculated flight times with this combo and 1320mah 3 cell LiPo pack, hands-off light @ 62% throttle are expected to be in the 31 minute range. I have also seen this plane fly many times with floats and in the dead of winter on skis. All in all a great all around plane. Have fun, Cheers, Tom
Reply to
Thomas & Erin Skoropad
I am one who has done the Butterlfy with a .40. Here's the changes:
1) the firewall needs to be heavier and more firmly mounted. 2) the wing center sections need to be strengthened and stiffened chose to fill the area in the center surrounding the main wing joine tube with "Bondo lite" (its a BLUE automotive filler) and double-webbed the spars THen I sheeted the center section completely eaxtra bays each side and the full center panel from LE to main spa top and bottom out to the polyhedral break. 3) the outer panels also need to be strengthened and stiffened. Shee the upper side from LE to main spar. 4) Fiberglass the portion of the polyhedral break where the sheetin meets using 0.5 oz cloth 2 inches wide. (thats almost a square o cloth) 5)The tailplanes need help.. double the 3/8 X 1/4 stock at the hing line with another piece. (just add it on and gain the stab area.. it the easy way and it works well) Do the same for the vertical stab.
Now the Butterfly has the strength for 1/2 throttle in level flight. Full throttle aerobatics will still rip the wings apart. Jsut go ahea and use an APC 12.25 X 3.75 to help prevent you overspeeding it. The it should climb like a rocket. (I used 11X5 and shattered the win pulling out of a dive using it to train Cub Scouts. (picture available... has a few more mods, not related to just putting a .4 on)
It makes a good piggy-back carrier or towplane for up to 100 inch spa LIGHT sailplanes (such as Gentle Lady or Spirit) with a .40
-- fhhuber50677 ----------------------------------------------------------------------- fhhuber506771's Profile:
formatting link
this thread:
formatting link
Reply to
fhhuber506771
Sheet
Hello, fhhuber506771.
This is really some excellent advice! I will study your post very carefully, and make similar changes in my own Butterfly. I like the idea of being able to fly at a lower throttle setting, where my engine will be making less noise. In fact, I intend to eventually do a diesel conversion, which should lower the noise level even more. If I break the crank shaft, or other internal parts, I am prepared to replace them, since I recently purchased a lathe, which I haven't even used yet. Again, thanks for the excellent advice!
Mike Mandaville Austin The United States of Texas
Reply to
MikeMandaville

PolyTech Forum website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.