Houndpup Rc
Legendary member
Would a Ender 3 pro be big enough for this?
Saab 105 64mm 3D Printed EDF Jet
- Thread starter telnar1236
- Start date
telnar1236
Elite member
Should be - all the parts should fit in a 220x220x220 build volume
FlyerInStyle
Master member
I am in no rush to build it, as on the printer I was planning to use for this, the computer for klipper decided to not boot up. It will take me about that long to get around to fixing it, so no rush. Thanks for designing this plane at all! Are the wings removable or is it fixed?
telnar1236
Elite member
I'm glad you introduced me to the design - it's a pretty neat plane and I'm happy to have a model of it now.
The wings are removable with three screws per wing (6 to remove both wings) although one of those is there for redundancy in case one strips during assembly so if you need to remove it a lot you could safely go to 2 per wing. The whole plane is modular, so you can separate the parts along each of these green lines just by removing a couple of screws.
telnar1236
Elite member
Flew the plane again today and unfortunately uncovered one of those possible problems I was worried about. Given the possibility of a deep stall with a more aft CG and the way the plane can tip stall, I suspected it might spin, and it does, quite badly in fact, with that more aft CG.
It seems like the CG I had on my first flight is about as far back as it's safe to go. The good news is that the fix is easy - just don't fly with an aft CG and you're golden. I also wasn't flying very well today, and it's certainly flyable with that aft CG so long as you don't stall. I'll probably modify the battery tray to make it easier to keep the CG forwards and reduce the likelihood of someone installing the battery too far back.
The plane also crashes surprisingly well for a 3D printed design. It landed in some tall grass right next to a drainage ditch, which probably helped, but I was still expecting it to be in many small pieces. Instead, the flying surfaces (wings and tail) are completely intact except for some easily fixable damage to one aileron. The nose fuselage, where it hit, was destroyed, as expected, but the core fuselage was mostly ok and should be easily repaired. The tail fuselage cracked, probably due to the weight of the tail, so it needs to be reprinted too, but for how nasty the crash looks, it should only be a couple days of printing and less than an hour of actual work on my part to get it back in the air.
It seems like the CG I had on my first flight is about as far back as it's safe to go. The good news is that the fix is easy - just don't fly with an aft CG and you're golden. I also wasn't flying very well today, and it's certainly flyable with that aft CG so long as you don't stall. I'll probably modify the battery tray to make it easier to keep the CG forwards and reduce the likelihood of someone installing the battery too far back.
The plane also crashes surprisingly well for a 3D printed design. It landed in some tall grass right next to a drainage ditch, which probably helped, but I was still expecting it to be in many small pieces. Instead, the flying surfaces (wings and tail) are completely intact except for some easily fixable damage to one aileron. The nose fuselage, where it hit, was destroyed, as expected, but the core fuselage was mostly ok and should be easily repaired. The tail fuselage cracked, probably due to the weight of the tail, so it needs to be reprinted too, but for how nasty the crash looks, it should only be a couple days of printing and less than an hour of actual work on my part to get it back in the air.
FlyerInStyle
Master member
good to know, good luck with the imporvements!
telnar1236
Elite member
Rebuilt and ready to fly again tomorrow - and the weather is finally good again.
I don't think I ever posted a picture of the v1 with the canopy painted, but this is what the plane looks like finished.
The only change in the design is in the battery tray in the nose which now extends a few inches further forwards, both adding a bit of weight to the nose and letting the battery balance the plane more easily.
I don't think I ever posted a picture of the v1 with the canopy painted, but this is what the plane looks like finished.
The only change in the design is in the battery tray in the nose which now extends a few inches further forwards, both adding a bit of weight to the nose and letting the battery balance the plane more easily.
telnar1236
Elite member
Got in two flights today with the Saab 105. Overall, the improvements to the battery tray seem to have fixed most of the issues with the plane. It's quite stable in the air and actually has more power than I thought from the first couple flights - it doesn't have unlimited vertical, but it does climb quite well. With the forward CG it's more resistant to stalls, though it does get a bit squirrelly at higher AOAs. I'm revising my speed estimate up to around 70 mph from 50-60 mph. Takeoffs are also good.
However, it still has one major flaw which is that it really really wants to bounce on landing. In the video you can see it bounces and flips, despite a quite reasonable touchdown. I repaired the minor damage and flew it a second time, and it did exactly the same thing again. I think the solution will be to either reduce the stiffness of the main gear struts, or to add in rubber band suspension. I'm leaning towards the latter at the moment. I also got a new banner out of today's flights.
FlyerInStyle
Master member
the rubber band suspension would be really cool, maybe TPU could also work, or use the inherent flexibility of PETG
telnar1236
Elite member
I've had issues with PETG landing gear. On my modular F-104 I started out with PLA struts which broke, so I switched to PETG, but to my surprise they were even worse. As a whole, PETG landing gear has a tendency to shatter even more than PLA which surprised me given its reputation for impact resistance. The final version of the gear used ABS which has worked pretty well, but I suspect it was more a geometry change that made it more reliable.
FlyerInStyle
Master member
Any updates @telnar1236 ?
telnar1236
Elite member
Just waiting to fly it with the improved main gear. I increased the width of the wheelbase and reduced the strut stiffness to try and reduce the bounce. Now we're mostly into the time of iterative testing and minor improvements which mostly depends on when I can manage to get out to fly.
telnar1236
Elite member
The new landing gear fixes the tipping problem, so I think the design is now pretty much ready to release. No video since I forgot my Run Cam, but it's a lot more stable on touch down now. The new struts are wider and less stiff than the old struts. I also replaced both wings, since I assembled the right wing badly meaning it really wanted to roll left without trim in case that was contributing to the bad landing characteristics. I'm not sure which of these fixed it, but fixed it is, so I'm not going to go back and try to break it again.
This plane doesn't particularly like wind, but once it's in the air, it handles ok, albeit with some wing rock and wind definitely makes landings trickier with this one.
This plane doesn't particularly like wind, but once it's in the air, it handles ok, albeit with some wing rock and wind definitely makes landings trickier with this one.
FlyerInStyle
Master member
I am almost ready to get my printer up and running so I would be happy to build it once you release the files!
FlyerInStyle
Master member
Has there been any progress with files being ready to realease? My printer works, and Toolchanges! Hopefully I can apply it to this build too
telnar1236
Elite member
STLs are good to go if you want them - I just need to take some time to buckle down and write a good instruction manual before I release this as a resource
FlyerInStyle
Master member
I would appreciate it if you would give the stls. What slicer do you use? (Do you happen to have 3mfs saved from it). also it should be built from PLA, right?
telnar1236
Elite member
Here you go - the majority of the plane should be printed with 2 perimeters and 4% infill. Some of the tail parts (tail fuselage but not tail boom and horizontal stabilizer) should be printed with 1 perimeter and 3% infill. All the control surfaces should also use 1 perimeter and 3% infill. Structural parts (the landing gear, inserts, wing spars, and control horns) should use at least 4 perimeters and 60% infill. The tires should be printed in the softest TPU you can manage with 2 perimeters and 20-35% gyroid infill depending on your preferences for how soft you want them.
For most of the parts, the orientation where they are printable should be clear, but for the fuselage parts, they should be rotated so that the arrow on each one is pointing up.
If you've got any questions, let me know and I'll do my best to answer.
telnar1236
Elite member
PLA should work so long as it's a light color and you're not somewhere with very hot weather. I used ABS which is a bit lighter and is a lot more heat resistant.
Similar threads
