Official Freewing Twin 70mm AL37 Airliner Thread

[Hugh Wiedman]

My mod on the winglets was simply to eliminate the lower section on the supplied parts, but as you can see from the pictures the latest version os the PA8 uses a different wing tip, no idea as to the reason, what little I know about wings those should provide some additional lift and perhaps add some drag as a consequence of the additional lift. Now that I’ve flown it and I know how it behaves I will be making some like the new PA8, no 3D printing just some old fashion balsa and ply covered in fabric. I think this latest version looks very cool, any thoughts on how it may affect the AL37 based on your tests?

Hey Roger, we missed you flying that last Friday. The runway is now outstanding, better than before at less than 1/2". All my jets got off with ease, me one happy camper. Your AL 37 should now take off in 10 feet instead of 20! And you missed the kielbasa as well, but more for us!

[Slowflight]

GliderGuy is right, the winglets do affect the AL37. In full size, winglets are optimized to reduce drag. In a model of this scale and made from these materials, the efficiency is less noticeable (don't expect to fly a minute longer with the winglets on versus off, for examples). What is more noticeable, however, is how the wingtips behave in space. As GliderGuy observed, the increased lift needs to be equal, so I would never recommend flying with only one winglet. We did that in the test phase and it was, let's say, "less effective".

As for adding aftermarket winglets, we're not pursuing optimal math here, so I think the approach mshagg used with his 3DP design is more than acceptable. There of course will be a threshold where too tall or too thin or too much sweep becomes problematic, but in general, extending the wingtip's shape (converging existing LE and TE) and extending it upward is fine.

More important for this model than the shape itself of a wingtip device is its positioning. You'll want both winglets to encounter the airflow in a consistent manner, so ensure that the mounting pegs are consistent (3D Printing solves this problem where back in the day we had to fabricate symmetrical pairs!). If one is canted outward or inward compared to the other, you'll notice a difference in flight behavior and should expect to have to trim for it.


We could talk for a long while about winglet design. To summarize, the objective is to reduce the tip vortices, which will in turn reduce drag and impart stability. The variables at play when shaping a winglet include twist, toe, sweep, and cant. The root cord, tip cord, and sweep help design the overall shape of the winglet, while relative AoA (cant) and its origination point along the root chord help position the winglet vertically in reference to the wing. Tweaking that base angle, and also the tip angle, further complicate things, as does variations in the radius' angular transition from wing to winglet (obtuse or even acute!). All these variables will affect an aircraft, a full size moreso than a model. "Optimum" performance also depends on an airspeed range. This is where model-specific design diverges more noticeably from full size aircraft design, but I digress.

I enjoy reading of everyone's exploits and additions to our bird!

My mod on the winglets was simply to eliminate the lower section on the supplied parts, but as you can see from the pictures the latest version os the PA8 uses a different wing tip, no idea as to the reason, what little I know about wings those should provide some additional lift and perhaps add some drag as a consequence of the additional lift. Now that I’ve flown it and I know how it behaves I will be making some like the new PA8, no 3D printing just some old fashion balsa and ply covered in fabric. I think this latest version looks very cool, any thoughts on how it may affect the AL37 based on your tests?

[mshagg]

Im biased but agree they look so much better. It's the backwards sweep that makes the radius of the blend look larger than it really is from certain angles.

[Aros]

I'm not finding a lot of photos of them but I am partial to the blended (not canted) winglets that have a significant curve at the base like the ones below. Most I see are more angular. Not sure what the aerodynamic difference would be however...

[Aros]

Finished the paint job today. Looks great in the air.

Just plain gorgeous. I've said it before and it's worth repeating...These custom liveries have been outstanding! No other RC model that I am aware of in mass production has ever had near the diverse, fantastic custom offerings from customers.

[mshagg]

Mounting an action camera at the base of one of the winglets is also a terrible idea if you like a plane which behaves consistently throughout its roll axis. Or, so i hear.

But it does make for some great shots, as demonstrated by QF667 on short final into YPAD (notwithstanding bank angle far in excess of SOP).

[Ian H]

Finished the paint job today. Looks great in the air.

[Alpha]

GliderGuy is right, the winglets do affect the AL37. In full size, winglets are optimized to reduce drag. In a model of this scale and made from these materials, the efficiency is less noticeable (don't expect to fly a minute longer with the winglets on versus off, for examples). What is more noticeable, however, is how the wingtips behave in space. As GliderGuy observed, the increased lift needs to be equal, so I would never recommend flying with only one winglet. We did that in the test phase and it was, let's say, "less effective".

As for adding aftermarket winglets, we're not pursuing optimal math here, so I think the approach mshagg used with his 3DP design is more than acceptable. There of course will be a threshold where too tall or too thin or too much sweep becomes problematic, but in general, extending the wingtip's shape (converging existing LE and TE) and extending it upward is fine.

More important for this model than the shape itself of a wingtip device is its positioning. You'll want both winglets to encounter the airflow in a consistent manner, so ensure that the mounting pegs are consistent (3D Printing solves this problem where back in the day we had to fabricate symmetrical pairs!). If one is canted outward or inward compared to the other, you'll notice a difference in flight behavior and should expect to have to trim for it.


We could talk for a long while about winglet design. To summarize, the objective is to reduce the tip vortices, which will in turn reduce drag and impart stability. The variables at play when shaping a winglet include twist, toe, sweep, and cant. The root cord, tip cord, and sweep help design the overall shape of the winglet, while relative AoA (cant) and its origination point along the root chord help position the winglet vertically in reference to the wing. Tweaking that base angle, and also the tip angle, further complicate things, as does variations in the radius' angular transition from wing to winglet (obtuse or even acute!). All these variables will affect an aircraft, a full size moreso than a model. "Optimum" performance also depends on an airspeed range. This is where model-specific design diverges more noticeably from full size aircraft design, but I digress.

I enjoy reading of everyone's exploits and additions to our bird!

[GliderGuy]

I designed those NG winglets on thingiverse (the lawn is much healthier now lol) - they're reasonably true to scale based on some diagrams I found online and have the same aerofoil shape as the AL37 wing (literally took the existing aerofoil profile, extended, shaped and bent it). Flying without any winglet at all makes the AL37 marginally less wobby if there's a breeze about IMO. Havent noticed any difference in flight characteristics between the stock Max-8 winglets or the 3D printed NG style winglet, although the stock winglets that came with mine never really sat flush on the wing which had a minor impact on trim.

In full scale the winglets offer marginal efficiency improvements, which i guess is important if you're burning 800 gallons of avgas an hour. I'm not appropriately qualified to opine on their impact at our scale, alpha probably has some insights though.

Not the easiest part to print; so unless you absolutely must have the 'blended' look of the NG winglet I'd recommend just modifying the ones it comes with.

I can absolutely state that the stock AL37 winglets do have a significant impact on the aerodynamics. While I was waiting for the glue to dry on one I had slightly damaged, I decided to make a flight with only one winglet in place. Since a winglet, in effect, aerodynamically extends the wing span of the wing (also reducing the drag), the AL37 had a bad roll in the direction of the wing without the winglet. Said another way, if the right winglet is not in place, the roll is to the right because of the "in effect' longer left wing.

Needless to say, after that rather interesting experience...I waited for the glue to dry on the repaired winglet before making another flight. I anticipated a roll, but not as much as I encountered.

-GG

[Aros]

I concur, Alpha would be more qualified to answer your question themudduck concerning those winglets in regards to performance on the AL37. I just like the way they look better than the clam shell ones they come with. I will probably take mshagg's advice and modify the stock ones.

[mshagg]

I designed those NG winglets on thingiverse (the lawn is much healthier now lol) - they're reasonably true to scale based on some diagrams I found online and have the same aerofoil shape as the AL37 wing (literally took the existing aerofoil profile, extended, shaped and bent it). Flying without any winglet at all makes the AL37 marginally less wobby if there's a breeze about IMO. Havent noticed any difference in flight characteristics between the stock Max-8 winglets or the 3D printed NG style winglet, although the stock winglets that came with mine never really sat flush on the wing which had a minor impact on trim.

In full scale the winglets offer marginal efficiency improvements, which i guess is important if you're burning 800 gallons of avgas an hour. I'm not appropriately qualified to opine on their impact at our scale, alpha probably has some insights though.

Not the easiest part to print; so unless you absolutely must have the 'blended' look of the NG winglet I'd recommend just modifying the ones it comes with.

[themudduck]

autotecart someone in this thread a ways back pointed me to this link since I want the same winglets when I do finally get mine...

[URL="https://www.thingiverse.com/thing:4059280"]https://www.thingiverse.com/thing:4059280

Dear Aros, that is very cool! Let me ask, since I am sure you might know, do these winglets have any affect on the aerodynamics, do they affect the way this model performs?
There's certainly nothing wrong with them if they just look fantastic, but I was just wondering.

[Aros]

Can anyone point me in the direction of where I can get updated winglets for this model. The ones that curve upwards instead of having a step in them like they have now

autotecart someone in this thread a ways back pointed me to this link since I want the same winglets when I do finally get mine...

https://www.thingiverse.com/thing:4059280

[xviper]

Take those and cut the down part, I did sanded it primed it and painted it. I dont think there is one available, or some one can print one for you.

There isn't one "available". It all started when someone like yourself just cut the bottom winglet off and did the finishing work himself.

[Slowflight]

Can anyone point me in the direction of where I can get updated winglets for this model. The ones that curve upwards instead of having a step in them like they have now

Take those and cut the down part, I did sanded it primed it and painted it. I dont think there is one available, or some one can print one for you.

[autotecart]

Can anyone point me in the direction of where I can get updated winglets for this model. The ones that curve upwards instead of having a step in them like they have now

[GliderGuy]

AS a novelty R/C aircraft or "Vanity" aircraft - LOL.....this model is well worth the money in both fun factor and flight performance. I am noticing my Motion R/C 50c 6s 5000mAh LiPo and the EC5 connector and the UBEC power supply are hot to touch after a 4min30sec flight. I am flying off of grass field with touch-n-go's and trying to stay out of the throttle as much as I can.....not quite ready to see how it does at 50% throttle in the turns yet. Our club is having fun with me as other pilots are joining up for F-16 Thunderbird, A-10 Warthog escort flights for laughs......quite entertaining stress free fun. I am interested in what LiPo brands and sizes are being used and flight times for grass field flights.

Thanks in Advance,
TwistedGrin

Flying in hot summer conditions, I became concerned about the heat being generated (flying Admiral Pro 6000 50 C). So, I made a cooling fan unit from a 24-volt, 80 mm, high-speed, 4,500 rpm, 60 cfm PC case fan which i mounted on the non-wired end of an old Admiral 6 s battery I am no longer flying in combination with a push-on/push-off SPST switch...taking care to only charge the cooling fan's battery to 4 volts per cell (6 x 4 = 24 volts). After I landing and removing the flight battery, I place this whole unit (battery with the fan at one end) in the fuselage with the fan placed over the rear opening in the plywood. This circulates air down into the ESC bay area and also blows air around the electronics at the front (BEC, EC5 connector, etc.). A 2-to 3 min exposure to the airflow cools everything down nicely. If you wish, you can also set the cooling fan unit under the fuselage for another 30 sec for blowing air directly on the ESCs. Using this blower/cooler removes the need for a longer cool-down period required otherwise.

I typically fly for 4 min with the 6000 mAh pack to ensure i have plenty of juice for a go-around should that be needed. This also shortens the charge time to about 45-50 min (4.5 amp charge rate). Remember that drawing less from a LiPo extends the life (number of charge/discharge cycles) of the battery before it dies. Draining a LiPo down a lot both increased your charge time and shortens the life of your LiPo batteries considerably. And...cooler electronics = happier electronics!

One last note: A 4 min flight at less than 1/2 throttle along with with some occasional acrobatics and speed dashes consumes about 3500 mAh to 4000 mAh...helping ensure a longer life for your LiPo.

-GG

[TwistedGrin]

AS a novelty R/C aircraft or "Vanity" aircraft - LOL.....this model is well worth the money in both fun factor and flight performance. I am noticing my Motion R/C 50c 6s 5000mAh LiPo and the EC5 connector and the UBEC power supply are hot to touch after a 4min30sec flight. I am flying off of grass field with touch-n-go's and trying to stay out of the throttle as much as I can.....not quite ready to see how it does at 50% throttle in the turns yet. Our club is having fun with me as other pilots are joining up for F-16 Thunderbird, A-10 Warthog escort flights for laughs......quite entertaining stress free fun. I am interested in what LiPo brands and sizes are being used and flight times for grass field flights.

Thanks in Advance,
TwistedGrin

[walkerm45]

The BEC, use to be called a"Voltage Regulator" connect any battery, 5 cell nicad or greater, and it would regulate the voltage to either 5, or 6 volts. Hence battery eliminator circuit. I still use them in my electric planes, and power them with a 5 cell Nickel metal hydride battery. I never use the main motor power battery. Always seem to have bad luck with them off the 6 cell lipos....They also were used extensively for ignition motors, with the appropriate regulated voltage.....

[TwistedGrin]

Received mine on Friday afternoon, had it ready to go Saturday morning at the field where I set up my rates and expo on the transmitter. I found the low rates not quite enough for our grass field and my own personal taste. The maiden was uneventful with a smooth landing. Subsequent flights I discovered the white aircraft in the white clouds was easily dis-appearing.....it's amazing how small the profile is coming in for runway passes and final landings. Four flights in total today all very easy and big sky sorti's....the last flight was complete with several touch-n-go's on grass field.....no issues at all. Removing the wings for transit is a bit of a hassle fiddling with the landing gear.....simplify with just leaving the mains down. Motion RC 50c 6s 6000mAh Lipo right at 5minutes with taxi back leaves at or near .3.70v per cell and a very warm battery......I hope to get a little better at throttle management in calm winds and more stick time on this bird.