Mr Man

Elite member
How about adding a hidden duct on the bottom? Have the edf swivel to the new duct on a servo.
 

telnar1236

Elite member
It would end up being a bit more complicated than that. In normal flight, thrust balances drag and lift balances weight. In an aerodynamically stable plane, the center of lift is behind the center of gravity so the pitching moment from the wing needs to balance out the moment from the location of the center of lift (you can also look at it like a big lift force a bit behind the center of gravity and a small downforce well behind the center of gravity - or a small lift force in front of the CG in a plane with canards).
1735261956140.png

If you add in thrust vectoring, the line of action of the thrust shifts so it's no longer through the CG. This creates a larger nose down moment which needs to be countered (this is why thrust vectoring is so useful for maneuvering).
1735262059210.png

The EDF unit is here in the fuselage, so there is no angle it could be rotated to have a lift force through the CG due to the EDF.
1735262168549.png

Therefore, you would need a second EDF or fan or similar in the nose to counter the moment from the main EDF or a fairly complete redesign to give the plane nozzles like the harrier at the CG and move the EDF forwards.
1735262306979.png

This would add another couple hundred grams of weight to the already heavy design. Doable, but it would hurt the performance a lot and the already difficult plane would be all but impossible to land without using the thrust vectoring. I've played around with the idea of VTOL in my head quite a bit since it would make a plane that I could fly in more locations and without a prepared runway which would be really nice, but it always comes down to the limitation that it would end up dragging a ton of weight around after transitioning to normal flight (or need to be a model of a harrier or similar design). The complexity of designing a system like this would also probably mean it would take longer to build than the complete redesign I've settled on instead.
 

Mr Man

Elite member
It would end up being a bit more complicated than that. In normal flight, thrust balances drag and lift balances weight. In an aerodynamically stable plane, the center of lift is behind the center of gravity so the pitching moment from the wing needs to balance out the moment from the location of the center of lift (you can also look at it like a big lift force a bit behind the center of gravity and a small downforce well behind the center of gravity - or a small lift force in front of the CG in a plane with canards).
View attachment 247235
If you add in thrust vectoring, the line of action of the thrust shifts so it's no longer through the CG. This creates a larger nose down moment which needs to be countered (this is why thrust vectoring is so useful for maneuvering).
View attachment 247237
The EDF unit is here in the fuselage, so there is no angle it could be rotated to have a lift force through the CG due to the EDF.
View attachment 247240
Therefore, you would need a second EDF or fan or similar in the nose to counter the moment from the main EDF or a fairly complete redesign to give the plane nozzles like the harrier at the CG and move the EDF forwards.
View attachment 247242
This would add another couple hundred grams of weight to the already heavy design. Doable, but it would hurt the performance a lot and the already difficult plane would be all but impossible to land without using the thrust vectoring. I've played around with the idea of VTOL in my head quite a bit since it would make a plane that I could fly in more locations and without a prepared runway which would be really nice, but it always comes down to the limitation that it would end up dragging a ton of weight around after transitioning to normal flight (or need to be a model of a harrier or similar design). The complexity of designing a system like this would also probably mean it would take longer to build than the complete redesign I've settled on instead.
Gotcha
 

telnar1236

Elite member
The work on the CAD continues to progress, if slowly due to the holidays. The core fuselage is done and the nose cone is modeled.
1735358109429.png

The size of this new version keeps throwing me off. I'm used to designing planes at the largest about 2/3 this size, so I keep needing to remind myself that the various parts of the structure are bigger than I'm thinking and needing to add in geometry to allow supportless printing. Or on the other hand, I can add holes to reduce weight into parts of the plane I normally couldn't because they are just overall bigger. I think this size of plane is probably actually better suited to 3D printing than the smaller ones I'm used to since it means it can be less overbuilt while being printable.
Another feature of this design, although one I may or may not decide to use depending on how the plane flies and how heavy it ends up, is that the nose cone is designed with provisions for a working pitot-static tube.
1735359999038.png

This is an idea I've been playing with and even occasionally posting about for years, but up to this point I have not built a plane both big enough and reliable enough to carry one. If I end up including it, it will communicate with an Arduino which will also have an accelerometer and GPS shield to log the flight performance of the plane. I built most of this setup for my modular planes, but it ended up being too big for them. I also want this plane to eventually be capable of FPV in some way or other so having airspeed could be useful for landing, but that will be some ways down the road.
1735360210555.png

I've also been working on the conceptual design of the landing gear. In the previous iteration, the gear was a bit too far forwards which meant the CG couldn't be set as far back as I would have liked and that the plane could end up stuck in a wheely on landing. In this version, the gear is just a bit further back which means it should be able to sustain a wheely but will always settle back onto all three wheels as it slows down even with the rear most CG position.
1735358641153.png
 

Mr Man

Elite member
The work on the CAD continues to progress, if slowly due to the holidays. The core fuselage is done and the nose cone is modeled.
View attachment 247266
The size of this new version keeps throwing me off. I'm used to designing planes at the largest about 2/3 this size, so I keep needing to remind myself that the various parts of the structure are bigger than I'm thinking and needing to add in geometry to allow supportless printing. Or on the other hand, I can add holes to reduce weight into parts of the plane I normally couldn't because they are just overall bigger. I think this size of plane is probably actually better suited to 3D printing than the smaller ones I'm used to since it means it can be less overbuilt while being printable.
Another feature of this design, although one I may or may not decide to use depending on how the plane flies and how heavy it ends up, is that the nose cone is designed with provisions for a working pitot-static tube.
View attachment 247268
This is an idea I've been playing with and even occasionally posting about for years, but up to this point I have not built a plane both big enough and reliable enough to carry one. If I end up including it, it will communicate with an Arduino which will also have an accelerometer and GPS shield to log the flight performance of the plane. I built most of this setup for my modular planes, but it ended up being too big for them. I also want this plane to eventually be capable of FPV in some way or other so having airspeed could be useful for landing, but that will be some ways down the road.
View attachment 247269
I've also been working on the conceptual design of the landing gear. In the previous iteration, the gear was a bit too far forwards which meant the CG couldn't be set as far back as I would have liked and that the plane could end up stuck in a wheely on landing. In this version, the gear is just a bit further back which means it should be able to sustain a wheely but will always settle back onto all three wheels as it slows down even with the rear most CG position.
View attachment 247267
Nice job!
 

telnar1236

Elite member
Everything is starting to come together. The white parts are ABS, the gray PLA, and the yellow don't have an internal structure defined yet so are assigned 5% the density of PLA to get an approximate weight.
1735970246927.png

The nose section of the fuselage and core section of the fuselage are also printed and everything prints nicely and fits together well. The only real thing to note here is the cooling vents which will blow air over the battery. They are something I frequently forget to add, but something that starts to become really critical with 6s power systems.
1735970430938.png

It's also fun comparing the original 70mm version with the new 80mm version. The fuselage is divided a bit differently since my printer didn't get bigger even as the plane did, but this is the closest comparison between them I could manage. The new airframe is much bigger which should help enormously with the stall speed and overall handling.
1735970650559.png
 

telnar1236

Elite member
The fuselage is now fully printed! This is the majority of the printing required for the airframe, so everything else should go a bit faster now. Like with the smaller 70mm version the first flights will be without some of the more fiddly peripherals like gear doors.
20250119_210429.jpg

This is definitely one of the larger airframes I've ever built. Here it is next to the modular F-104 for comparison. Both are built to the same scale (~1/12) so the real F-106 was also this much bigger than the real F-104.
20250119_210635.jpg

Even though the 80mm fan will have plenty of thrust for this plane unless I got something very wrong with my weight estimate, it still is a little hard to believe such a small fan can propel this large an airframe.
 

Mr Man

Elite member
The fuselage is now fully printed! This is the majority of the printing required for the airframe, so everything else should go a bit faster now. Like with the smaller 70mm version the first flights will be without some of the more fiddly peripherals like gear doors.
View attachment 247634
This is definitely one of the larger airframes I've ever built. Here it is next to the modular F-104 for comparison. Both are built to the same scale (~1/12) so the real F-106 was also this much bigger than the real F-104.
View attachment 247635
Even though the 80mm fan will have plenty of thrust for this plane unless I got something very wrong with my weight estimate, it still is a little hard to believe such a small fan can propel this large an airframe.
Cool!
 

Tench745

Master member
The work on the CAD continues to progress, if slowly due to the holidays. The core fuselage is done and the nose cone is modeled.
View attachment 247266
The size of this new version keeps throwing me off. I'm used to designing planes at the largest about 2/3 this size, so I keep needing to remind myself that the various parts of the structure are bigger than I'm thinking and needing to add in geometry to allow supportless printing. Or on the other hand, I can add holes to reduce weight into parts of the plane I normally couldn't because they are just overall bigger. I think this size of plane is probably actually better suited to 3D printing than the smaller ones I'm used to since it means it can be less overbuilt while being printable.
Another feature of this design, although one I may or may not decide to use depending on how the plane flies and how heavy it ends up, is that the nose cone is designed with provisions for a working pitot-static tube.
View attachment 247268
This is an idea I've been playing with and even occasionally posting about for years, but up to this point I have not built a plane both big enough and reliable enough to carry one. If I end up including it, it will communicate with an Arduino which will also have an accelerometer and GPS shield to log the flight performance of the plane. I built most of this setup for my modular planes, but it ended up being too big for them. I also want this plane to eventually be capable of FPV in some way or other so having airspeed could be useful for landing, but that will be some ways down the road.
View attachment 247269
I've also been working on the conceptual design of the landing gear. In the previous iteration, the gear was a bit too far forwards which meant the CG couldn't be set as far back as I would have liked and that the plane could end up stuck in a wheely on landing. In this version, the gear is just a bit further back which means it should be able to sustain a wheely but will always settle back onto all three wheels as it slows down even with the rear most CG position.
View attachment 247267
Are you thinking of printing the pitot-static tube, or using an existing unit like Fr-sky and others offer?
 

telnar1236

Elite member
Are you thinking of printing the pitot-static tube, or using an existing unit like Fr-sky and others offer?
I'm currently using/designing around this pitot tube.
I got it for a different project a couple years back but never got around to integrating it into any of my modular designs. I would eventually like to figure out how to resin print a pitot tube too, but for now that's beyond my skill set.
 

L Edge

Master member
@telnar1236
Have you ever thought about using a reversible ESC after you land. No extra weight and all you do is flip a switch after time delay, the edf reverses and will definitely slow your delta's length down!!!!!!!

Should experiment it on model you already have. I used a Freewing ESC on a 5 bladed 64mm EDF up to max 1/2 throttle( didn/t want blades to explode) and it worked. Then backed up plane for the fun of it.
 

Mr Man

Elite member
@telnar1236
Have you ever thought about using a reversible ESC after you land. No extra weight and all you do is flip a switch after time delay, the edf reverses and will definitely slow your delta's length down!!!!!!!

Should experiment it on model you already have. I used a Freewing ESC on a 5 bladed 64mm EDF up to max 1/2 throttle( didn/t want blades to explode) and it worked. Then backed up plane for the fun of it.
Sounds like fun.
 

telnar1236

Elite member
@telnar1236
Have you ever thought about using a reversible ESC after you land. No extra weight and all you do is flip a switch after time delay, the edf reverses and will definitely slow your delta's length down!!!!!!!

Should experiment it on model you already have. I used a Freewing ESC on a 5 bladed 64mm EDF up to max 1/2 throttle( didn/t want blades to explode) and it worked. Then backed up plane for the fun of it.
That's a good thought. It definitely works well in the planes I've seen with it, so I should look into it. For the 80mm variant, with the size and print time (200+ hours) anything that can prevent damage and make less than perfect landings manageable is worth it. For the 70mm version, though, that could be the difference between a flyable plane and something too difficult to land. Stability was never really an issue, just the speed that needed to be carried, so thrust reverse could make it just about possible for a skilled pilot to get it home safely reliably, although even then, a 50 mph landing speed is very high.
1737521296411.png
In good news, the 80mm plane is right on track to be around my target weight. I'm guessing between 3200g and 3300g. With its size and at that weight, it should hopefully be a pretty easy landing plane, though I won't really know till it's done.
 

telnar1236

Elite member
The wings (except for the elevon surfaces) are now fully designed.
1737947758813.png


Each wing will weigh about 320 g without the servo, retracts, or elevons installed which I'm ok with on such a big plane. All the flying surfaces are also very thin. While not ideal for RC scale planes in general, for a delta it matters a lot less and will reduce the drag at high speeds. Mostly, they're just like that to look scale though.
1737947861237.png

The internal structure is fairly complex with each wing being printed in 6 pieces which are then glued together. You can see where the section breaks are by the "ribs" at the breaks.
1737948109894.png
 

telnar1236

Elite member
The wings and tail are printed!
1738283554902.png

Now it's time to start moving into the design of the smaller more nitpicky bits. The remaining items I need before a maiden flight are as follows:
  1. Elevons
  2. Rudder
  3. Elevon servo trays
  4. Rudder servo tray
  5. airbrakes
  6. Nose gear and nose gear servo mount
  7. Main gear struts
  8. Main gear outer doors
  9. Main gear inner bays (no doors for maiden)
  10. Nose gear strut
  11. Cheater inlet block
  12. Payload bay cover (temporary until payload bay can be designed)
  13. Battery tray
  14. Battery hatch
I'm guessing I'll be ready to try flying in a week or two which is just as well since I'm stuck under a TFR this weekend.