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Jun 15, 2011, 01:57 AM
"We're in the pipe, 5 by 5"
Lupus78's Avatar
Thread OP
Build Log

3d printable micro Hellcat

This arrived quite some time ago. I think I need to finally continue with this one. Wingspan about 16" / 40cm. It's roughly based on Guillows 16" Hellcat, as well as Truckerboy's balsa plans:

Previously I've been doing these 3d printed detail parts for existing planes by modeling them myself and ordering them from Shapeways. Shapeways is a Dutch 3d printing company, which prints out 3d models of anything you want and ship it to you by UPS courier. Very nice service, I'd say. And their printing costs have been decent, considering everything is printed on demand and manually finished, well packed and then shipped. The WSF material they use is incredibly tough, flexible (doesn't snap too easily) and doesn't weight too much. Pretty good for RC I'd say!

Here's more info about my previous works (cockpit kits, pilots and detail parts):

At this phase I've printed out my first test sample. And I quite like how this Hellcat turned out, if I can cover it with some proper film. And I might need to polish the outer surfaces a bit (so they won't seem so rough through the film), add some carbon fiber spars here and there to make the frame a bit more rigid, as the thinnest spars (about 1mm thick) are almost rubber-like. They seem to give too much when film tension is added. I guess I made the stringers a bit too thin just to save some weight. But as you can see, I've modeled the elevator and rudder servo horns, servo mounts, motor mount, 4x3mm magnet attachment for cowling, screw & nut slot for wing assembly (I'm using a nylon bolt). All the wing parts are separate items, for covering purposes. The battery strap will be placed on the forward section, topside. Battery will be replaced by removal of the wing. There's also thin slots for the wing hinges. I'm using some disk material from old floppy disks as the hinges for ailerons, rudder and elevator.

Weight distribution I've tried to make as forward as possible with the rigid cowling and leading edge of the main wing. This structure should also make it really tough in crashes. The wings has about 3 degree washout and deep camber airfoil, about identical to 16" Guillows Hellcat which I've used as an example. For the motor I'm using either 10 gram or 16 gram hextronic outrunner (they have identical mounts). First I might try the bigger one. I'll see if I can make this thing fly. (No quarantees!) Weight shouldn't be a huge problem, but it will be pretty fast. On our field where wind is often a big factor, the heavy weight is a good thing and there's lot of space to fly (as you can see from the P-51 video) so I don't mind if it's a bit fast. The overall weight should settle around 4-5 oz. It's on the heavier side with a plane this size and has lot's of power, so it won't be an indoor model for sure.

For the next print ("version 2") I'll most likely reinforce some parts and formers, remove the thin stringers and make ready slots for some thin 1mm carbon fiber stringers(?), which should make it more tough and rigid. I'll print it out with the new Shapeways "WSF Polished" material. It's a lot more smooth than their previous WSF material which I've used before and not much more expensive. This would remove the need for any polishing and additional finishing.

Here's a list of electronics I've got waiting for testing. All the mounts has been designed for exact measurements of these components. They're cheap and should keep the price of the final plane decent.

16 gram outrunner:
10A ESC:
4ch Receiver:

Battery option 1 (heavier):
Battery option 2 (lighter):
Last edited by Lupus78; May 21, 2012 at 12:54 AM.
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Jun 15, 2011, 07:20 AM
Registered User
speedy01's Avatar
Extraordinary -- in all respects!

I'd like to join the queue if you decide to market a few.

Gene K
Jun 15, 2011, 08:00 AM
"The Uzitalo nine millimeter"
Uusitalo's Avatar
Brilliant stuff!
Jun 15, 2011, 09:30 AM
Registered User
Chrizz's Avatar
Outstanding! Well done :-)
Jun 15, 2011, 11:11 AM
"We're in the pipe, 5 by 5"
Lupus78's Avatar
Thread OP
Thanks! Quite a lot of modelling and though has gone into making it happen. After all the things I've done before, I just wanted to try out IF this kind of thing could be even possible. So I'm experimenting with new technology...

After this first print I've still got quite a lot of little changes here and there to do. Especially after the first flights (if it even stays in the air!)... I want to make it as ready to put together as possible, before it's made available for everyone. And it needs to be somewhat fun to fly and balanced with the recommended gear. The beauty of Shapeways is that I can make all my stuff available to order, straight from Shapeways. I will have nothing to do in producing and shipping it to you. It's all Shapeways. You'll receive the parts neatly packed and shipped to home door. The price for the airframe of this Hellcat will be around 80-100 dollars (purely based on volume of material used in this plane), shipped. So with electronics it should settle to around 120 dollars.

After this more challenging Hellcat (even if it fails to fly), I think I'll do some simplified superlight airframe, kinda "Shapeways Ultimate trainer" or similar. I'd love to have an easy to put together simple trainer that's small, light, easy to fly, four channel and would be made for the ultra-cheap HK gear.
Last edited by Lupus78; Jun 15, 2011 at 11:17 AM.
Jun 15, 2011, 04:09 PM
Registered User
speedy01's Avatar
Originally Posted by Lupus78
I'd love to have an easy to put together simple trainer that's small, light, easy to fly, four channel and would be made for the ultra-cheap HK gear.
Well, the T-6 is a trainer....although not the type of trainer you had in mind. But still, there are so many possible schemes for that venerable aircraft.

Why are you targeting HK gear vice ParkZone?

Gene K
Jun 15, 2011, 04:26 PM
Registered User
Dude, that looks awesome! I can see where you got most of the inspiration to this model! And you've made quite a lot of optimization, I guess mostly because this plastic is heavier than balsa? What's the weight of the airframe as is in the pictures?

I have to point out that your wing needs to be stronger in the center. The LH and RH side spars need to be connected, otherwise the wing may break mid air or during a hard landing. It WILL break mid air if you aim for 4-5 oz and a quick model. Wouldn't be that nice to see such a lovely model break during the first hard turn.

As for the motor, if you're aiming for 4-5 oz, definately go for the 16 gram HXT motor. The 10 g motor won't cut the mustard. These models are prone to tip stalling (no matter how much washout you add!) and need to fly fast as heck. Also the CG needs to be really far forward. There is no such thing as a nose heavy "guillows" RC model! Nose heavy is good in this case. And definately go for a 3s 360 lipo. This combo is KILLER, and paired with an apc 4,75x4,75 the plane will climb vertically until your eyes start to bleed. Well almost . No but seriously, the 10 g outrunner keeps the model in the air, but it'll feel sluggish and heavy. The more powerful motor sets the CG just about right, and alos gives the extra oomph that's sometimes needed.
Last edited by Truckerboy; Jun 15, 2011 at 04:32 PM.
Jun 15, 2011, 07:12 PM
Check out my Shapeways Shop
ICU's Avatar
Wow, very nice. I've known about shapeways for years now and have always wanted to get something made there, just never done it. Even though I've seen some really incredible objects made there on their website, that has to be one of the coolest.

Best of luck on the maiden.

I do agree with Truckerboy. You will need some support for those wings.
Jun 15, 2011, 11:08 PM
"We're in the pipe, 5 by 5"
Lupus78's Avatar
Thread OP
Thanks for the suggestions! Keep those ideas coming.

It's great to have Truckerboy around! And yes, there's a lot of optimization. Still I think the weight is more than twice of a similar balsa model. It should be around 40 grams, haven't measured it yet, though. There might be point in reinforcing some parts of the wing. Especially the connections I've tried to over-optimize. But for the main spar reinforcement, you really need to see how tough this material really is. And it doesn't just break, it flexes. There's really no way the wing would break very easily mid-air. The fully sheeted LE acts as a really tough "spar". It's not like balsa cover, which can't take any pressure. But I guess I could always make it super-strong. One idea I had was to make ready slots for a carbon fiber main spars that you could just slide and glue in place.

The electronics options I've made because they are cheap, easy to get to Finland (without taxes) and the regular spectrum gear wouldn't have the power needed. Also these motors were proven by Truckerboy to work great on his gorgeous little balsa planes.
Last edited by Lupus78; Jun 16, 2011 at 12:30 AM.
Jun 16, 2011, 06:52 AM
vtol fan
nadine's Avatar
I want one of this! much cost is and shiping to italy,if is availble??!!
nice work....
Jun 16, 2011, 07:41 AM
"We're in the pipe, 5 by 5"
Lupus78's Avatar
Thread OP
I think THIS must be the most incredible 3d printed item from Shapeways. (But not something I'd buy.)

As when the Hellcat is available and how much it will cost; It's still in the early "prototype" phase. I'm hoping that the final "production version" will be below 100 dollars, shipping included. Material & production costs are dictated by Shapeways and I can only affect on how much material my model uses. As this is an highly experimental, I can give no quarantees it will actually fly well. But I'm definitely going to try! If the design ends up being successful, I will make it available for everyone. And I will post detailed instructions how to build it. Only harder part will be the covering phase and setting up the torque rods for the ailerons. I will support the model after (possible) release by updating parts. All the feedback is really appreciated, so we can tweak it as good as possible. Good thing with Shapeways is that I can upload just the updated parts and offer all the parts separately if you happen to crash any beyond repairs.

PS. Any ideas for servo rods, covering options etc. are appreciated. The wing has readymade holes for a torque rod setup for ailerons and regular push rod setup for the tails.
Jun 16, 2011, 12:27 PM
Registered User
Brent Slensker's Avatar
WOW!...This plane looks great!
Jun 17, 2011, 01:33 AM
"We're in the pipe, 5 by 5"
Lupus78's Avatar
Thread OP
"White, Strong & Flexible" is the material I've used. It has proven to be quite a wonderful material. It can take a LOT of abuse, flexes and does not break very easily. I've tested to drop the fuselage onto hard surface and it takes it without a scratch. Main problem at the current version is that certain places are way too thin and so they flex too much. For the next version I'm most likely removing all the thin stringers in the fuse, improving all weak spars and adding some guides and slots for carbon fiber rods. (Maybe 2 or 3mm spars on wings and one on the bottom spine, plus 1mm stringers to cover the fuse?) I'm planning of making loops that you can slide the rods into and then just glued into place. Simple, and should make it the structure rigid enough.

I've just ordered some 1, 2 and 3mm carbon fiber spars, which I'm planning to use to reinforce the plane. Also some dark blue Solarfilm Lite, which I'm gonna test.

Finally I weighted the parts. Wing 16.3g, cowling 5.6g, fuse 11.8g and all the rest 10.7g Seems to be where I estimated them to be.
Last edited by Lupus78; Jun 17, 2011 at 02:48 AM.
Jun 17, 2011, 03:19 PM
Check out my Shapeways Shop
ICU's Avatar
One thing you can try doing with future versions without adding much weight or material. Is to add fillets (radii) to all of your high stress areas. All those 90* angles will be a weak point. Adding just a small fillet there will help reduce the stress in a crash tremendously.
Jun 17, 2011, 05:29 PM
Founder of the EDF20 club!
all4smallrc's Avatar
I have a feeling Shapeways is going to revolutionize the way we know micro airplanes. That is just too cool! Makes me want to design a model to get printed by Shapeways.

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