F-106 3D Printed Jet

[telnar1236]

This time I have video of the flight! With the plane fixed up and mostly ready to go, I decided to risk leaving it in my car during the day since it's still not too terribly hot out and the plane is mostly ABS which should stand up to even the worst weather. I wasn't expecting to get video today, but someone else at the field caught the takeoff and landing, so I figured I'd share it. The middle of the flight is cut out, but it was mostly just circling and getting the plane trimmed and playing around with the stall.

Despite it being quite windy, the plane flew beautifully. It is generally quite gentle handling and retains its energy pretty well for a delta. It also flies and lands much gentler than the 70mm version thanks to its much lower wing loading and improved wing design. Now I can focus on minor refinements and getting everything just the way I want it.
The biggest issue during these flights was the wheels. While the PLA wheels showed a bit of wear, the PETG wheels were far worse. The right main gear wheel was tilted at a 10 degree angle after just two relatively gentle takeoffs and landings and the left wheel managed to bind itself to the bolt I'm using as the axle and make it back out a bit each time it landed.

 

[Mr Man]

This time I have video of the flight! With the plane fixed up and mostly ready to go, I decided to risk leaving it in my car during the day since it's still not too terribly hot out and the plane is mostly ABS which should stand up to even the worst weather. I wasn't expecting to get video today, but someone else at the field caught the takeoff and landing, so I figured I'd share it. The middle of the flight is cut out, but it was mostly just circling and getting the plane trimmed and playing around with the stall.

Despite it being quite windy, the plane flew beautifully. It is generally quite gentle handling and retains its energy pretty well for a delta. It also flies and lands much gentler than the 70mm version thanks to its much lower wing loading and improved wing design. Now I can focus on minor refinements and getting everything just the way I want it.
The biggest issue during these flights was the wheels. While the PLA wheels showed a bit of wear, the PETG wheels were far worse. The right main gear wheel was tilted at a 10 degree angle after just two relatively gentle takeoffs and landings and the left wheel managed to bind itself to the bolt I'm using as the axle and make it back out a bit each time it landed.

How about getting some Du-Bro wheels? I’ve heard they’re really good.

 

[telnar1236]

How about getting some Du-Bro wheels? I’ve heard they’re really good.

That was my original plan. I actually have the wheels sitting on my shelf, but the problem is that there isn't quite enough space to fit them into the very thin wing or fuselage with the gear retracted. The current wheels are almost bicycle wheel like in their proportions and I haven't been able to find an OTS equivalent. If anyone has any recommendations on either very thin wheels or on wear/melting resistant filaments I could use, I would welcome any suggestions.
I've been trying to avoid nylon since it's a pain to print, but I get the feeling that might be the direction I end up stuck with.

 

[Mr Man]

That was my original plan. I actually have the wheels sitting on my shelf, but the problem is that there isn't quite enough space to fit them into the very thin wing or fuselage with the gear retracted. The current wheels are almost bicycle wheel like in their proportions and I haven't been able to find an OTS equivalent. If anyone has any recommendations on either very thin wheels or on wear/melting resistant filaments I could use, I would welcome any suggestions.
I've been trying to avoid nylon since it's a pain to print, but I get the feeling that might be the direction I end up stuck with.

How about adding some O-rings for cushion?

 

[telnar1236]

How about adding some O-rings for cushion?

Like inside the hole in the wheel between the 3D printed part and the axle?

 

[bisco]

great build and flight, well done!

 

[Mr Man]

Like inside the hole in the wheel between the 3D printed part and the axle?

No, on the outside of the wheel.

Sort of like one of @L Edge ‘s formula 1 racers from back in the day.

 

[telnar1236]

No, on the outside of the wheel.

Sort of like one of @L Edge ‘s formula 1 racers from back in the day.

Not sure how much that would end up helping. The wear is occurring on the inside of the hole itself instead of between the wheel and the strut. This is the current arrangement with the strut on both sides of the wheel, then metal washers between the wheel and the strut, and then the wheel in the middle. The wear is happening along the orange lines between the wheel and axle

I've started trying to print a nylon wheel but it's not going too well. I suspect the 0.4 mm nozzle I'm using is just providing too much resistance since the filament seems to want to stop flowing even when I put the temperature up to 280 C which is the max recommended on the spool. I've tried the whole range in 10 degree increments, but the only way I've had luck so far is to print ridiculously slowly

 

[telnar1236]

great build and flight, well done!

Thanks, pretty happy with how this one has turned out

 

[Mr Man]

Not sure how much that would end up helping. The wear is occurring on the inside of the hole itself instead of between the wheel and the strut. This is the current arrangement with the strut on both sides of the wheel, then metal washers between the wheel and the strut, and then the wheel in the middle. The wear is happening along the orange lines between the wheel and axle
View attachment 250050
I've started trying to print a nylon wheel but it's not going too well. I suspect the 0.4 mm nozzle I'm using is just providing too much resistance since the filament seems to want to stop flowing even when I put the temperature up to 280 C which is the max recommended on the spool. I've tried the whole range in 10 degree increments, but the only way I've had luck so far is to print ridiculously slowly

Ah ok, 👍🏼

 

[L Edge]

Thanks, pretty happy with how this one has turned out

That was nice landing in that crosswind. With the trees and hill, do you get very much turbulence as well?

 

[telnar1236]

That was nice landing in that crosswind. With the trees and hill, do you get very much turbulence as well?

Thanks, fortunately it's not too bad most of the time, especially if you perform a steep approach. Close the ground it can get a bit bumpy, especially for smaller planes, but with something the size of this F-106 you don't notice it too much

 

[telnar1236]

Nylon was the answer for the wheels. I performed four more flights with no noticeable damage and the ground handling was also noticeably better without the wheels going all over the place. It's a pain to print, but fortunately the wheels aren't too big so it's very manageable and seems easier than ABS overall so long as you keep the speed very low.
In the more recent flights I started exploring the performance envelope a bit more. It's no 3D plane, but I haven't run into any fast jet maneuvers it can't do. Loops and rolls are easy as are half Cuban 8s and split S maneuvers. Inverted requires some down pressure since the wing is trimmed for upright flight and it's a delta, but is quite easy and the down pressure is not excessive or unmanageable. High alpha is great, as expected for a delta. Unlike some planes, the elevons remain effective up until stall. The rudder rolls the plane as well as generating, so knife edge might be challenging and I haven't tried it yet, but the rudder is also very effective so I suspect it might be possible.
The real F-106 had the risk of entering an unrecoverable flat spin at high angles of attack, so I have been a bit wary of any flat spin or J turn like maneuvers. The plane does seem to want to sideslip as it approaches a stall, although it's quite easy to fight, so I suspect that the possibility of flat spinning might carry over from full scale. I definitely want some more experience with flying it before I try anything that crazy, so I have a fighting chance of recovering.

 

[telnar1236]

I spent another four flights playing around with high angles of attack and it turns out that a lot of my fears were unfounded. Specifically, flat spins aren't really even proper spins and are more of a nonevent than anything. With a CG about as far aft as is reasonable, you can force it to spin, but even then, throttling up immediately pushes it back into a dive and it recovers very easily. I'm hoping to get some video this weekend, TFRs and weather permitting, of more of a performance flight to demonstrate just how aerobatic this thing is.
In less good news, the PLA gear struts are also starting to show signs of getting more wobbly, specifically around the pivot point for the trailing link suspension. I'm probably going to need to make them out of nylon too, unfortunately, but at least I now know that nylon is manageable and works very well. I don't think any of the issues are insurmountable.

 

[telnar1236]

As promised, a performance flight of the F-106. I struggled a bit with the landing, but otherwise I think the video speaks for itself.

The flight performance is great, and once I get the functioning air brakes installed, that should make it easier to bleed speed on landing.
Beyond learning to fly the F-106 better, I've continued to fill in the various parts that aren't strictly needed for flight but that I want anyway. First off, I got the payload bay working. Having one servo per door instead of the servo shared between both doors in the 70mm version makes them much more reliable.

I also mostly fixed the problems with the landing gear. I printed them in glass fiber nylon and the much higher performance material seems to have significantly boosted the strength and durability. I flew six flights with very little noticeable loosening.

There will be one more iteration on the gear to improve tolerances, increase the width of the tire, and bring the tire more in line with the retract unit. While the gear held up, it still felt a bit wobbly on the ground, and this should help with that. Using glass fiber nylon which stronger than some types of aluminum makes geometry I wouldn't have considered with PLA possible, so I have a bit more room to play with now.