The Other XB-70 Build | Valkyrie V2
Pieliker96
Elite member
While I do like the idea, I think that the short time between maiden and upload would be worth the increased quality. Livestreams, especially given the terrible cell coverage of the field, wouldn't be worth it purely for the live nature of the video. I'm sure we can all wait a couple hours for a flight video
.I realized that I didn't post Pt. 4 here, so Here it is. It mainly covers the electronics that I'm using as well as the ducted fan thrust test data.
And part 5, covering everything from the gear bogies to the taxi test:
Michael9865
Elite member
Wow! Great progress!
Pieliker96
Elite member
Made a little progress today.
Got the main gear aligned so that I'll no longer be sideslipping on takeoff. The original axle that went through the strut was slightly too small, the new one fits much better. There is much less wobble in the gear.
I also installed the servos for the primary flight control surfaces (elevons and rudders).
I ended up with a pull-pull system for the elevons, using a linkage stopper on the bottom for tension. It seems to work pretty well and there's no binding. If the linkage stopper fails then I'll still have up-elevator authority.
Got the main gear aligned so that I'll no longer be sideslipping on takeoff. The original axle that went through the strut was slightly too small, the new one fits much better. There is much less wobble in the gear.
I also installed the servos for the primary flight control surfaces (elevons and rudders).
I ended up with a pull-pull system for the elevons, using a linkage stopper on the bottom for tension. It seems to work pretty well and there's no binding. If the linkage stopper fails then I'll still have up-elevator authority.
Pieliker96
Elite member
Wiring is tedious.
Here's a diagram showing the complexity:
I opted to have the servos and retract controller directly wired to the positive and negatives of the ESCs and BEC, meaning that I won't have to run all of that current through the receiver. (Exception: nose steering servo) This also means that the electrical load is distributed across multiple sources, decreasing the potential for overload or brownout. In addition, I'll only have to run one wire from the receiver to each servo.
And all packed into the small space I have:
I've gotten to the point where I can permanently attach the upper fuselage to the nacelle, which I'll do tonight. Tomorrow is figuring out where the batteries need to go, final retract alignment, and sheeting of the fuselage.
I'll also need to calculate (or at least approximate) stall speed and acceleration in order to determine the length of runway I'll need for takeoff and landing. I've already scouted two sites close to my house and they have plenty of space to fly in. Their runways are 50 feet wide and 300 (or 400) feet long, which should be plenty, but we'll see.
I'm also working on some checklists and general rules for operating the plane. This includes pre-flight checklists, takeoff and abort scenarios, and flight plans for the maiden. I'm also thinking of procedures to be followed in the event of an engine out, servo failure/malfunction, structural failure, loss of signal, etc. Ideally this wouldn't happen, but I have to be prepared for anything.
It feels good to finally make some real progress on this thing after around two months
Here's a diagram showing the complexity:
I opted to have the servos and retract controller directly wired to the positive and negatives of the ESCs and BEC, meaning that I won't have to run all of that current through the receiver. (Exception: nose steering servo) This also means that the electrical load is distributed across multiple sources, decreasing the potential for overload or brownout. In addition, I'll only have to run one wire from the receiver to each servo.
And all packed into the small space I have:
I've gotten to the point where I can permanently attach the upper fuselage to the nacelle, which I'll do tonight. Tomorrow is figuring out where the batteries need to go, final retract alignment, and sheeting of the fuselage.
I'll also need to calculate (or at least approximate) stall speed and acceleration in order to determine the length of runway I'll need for takeoff and landing. I've already scouted two sites close to my house and they have plenty of space to fly in. Their runways are 50 feet wide and 300 (or 400) feet long, which should be plenty, but we'll see.
I'm also working on some checklists and general rules for operating the plane. This includes pre-flight checklists, takeoff and abort scenarios, and flight plans for the maiden. I'm also thinking of procedures to be followed in the event of an engine out, servo failure/malfunction, structural failure, loss of signal, etc. Ideally this wouldn't happen, but I have to be prepared for anything.
It feels good to finally make some real progress on this thing after around two months
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Pieliker96
Elite member
Well, I did get one of those things done today
I intended to do some more wiring. To do this, I had to find out where the CG would need to end up (and where it currently was) in order to find where the batteries would have to go. I used an online CG calculator and compared it to the scaled-up CG from my test model, and they matched (~26" back from the wing's leading "point"). I then assembled the plane and moved the batteries around to find where they would have to go.
They'll all have to go in the nose.
I was expecting to have to put them in the junction between the neck and the front fuselage. Putting them in the nose means that my battery leads will have to be much longer and the neck will have to have much more supporting structure for the extra ~1kg of batteries. When I was finding the CG, the nose tended to droop by an inch or three
Considering that it'll be a significant portion of the aircraft's mass, any sudden changes in momentum or hard maneuvering could cause excess bending in the neck's structure leading to breakup. The real B-70 had some flex in its structure due to being so large (to the point where paint would flake off), but what I'm dealing with is unacceptable. I opted to reinforce the neck area with a massive amount of stringers, which are a small mass penalty for their structural gain. I also preloaded them to bend the nose slightly upwards, meaning that the small amount of droop from the batteries will bring them back to the intended level.
Here's the neck prior to reinforcement (remember, this would be skinned with foam):
And after:
Beyautiful.
I also laser-cut and glued on the engine nozzles:
Here's the mid-fuse. Wiring is around halfway done overall, i just need to run the leads for both of the rudders and one elevon. Unfortunately, I have lots of stuff planned for the remainder of spring break, so I don't think I'll end up finishing this within the next few days, as I intended to do.
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Pieliker96
Elite member
Got the wiring finished and the rudders installed today. I also ended up doing a short controls test and run-up. All that's really left is to sheet the fuselage and modify the nose to hold the batteries.
Here's the spaghetti around the receiver:
And the rudders installed (note the gap for sheeting):
And the control check/runup:
While trying out the retracts I ran into some issues with gear door clearance that I hadn't had before. I might end up removing them like Ben did, or modifying them to work better.
Here's the spaghetti around the receiver:
And the rudders installed (note the gap for sheeting):
And the control check/runup:
While trying out the retracts I ran into some issues with gear door clearance that I hadn't had before. I might end up removing them like Ben did, or modifying them to work better.
Pieliker96
Elite member
I got the fuselage sheeting done today. It's nowhere near perfect but should look fine in the air.
The neck section is extremely strong now. I have no doubt that it'll be able to hold the nose filled with batteries, but now I'm concerned with all of that weight being held by two foam spars.
I also redesigned the retract mounts so I could remove the units themselves to secure the pins. The oleos don't twist anymore, the rest of the slop is where they meet the bogies, which is negligible. I've decided to forego the gear doors for now, mainly because they proved to be way to much of a hassle to get right. I'd rather get the plane flying first and add them later.
What's Left (W/ regards to building):
-Final alignment of the Mains
-Receiver hatch
-Sheeting of the cockpit/nose area
-Hollow out the front fuselage for the batteries
-Get the wings to fit tight, add mounting screws in the spars
-Clean everything up (Sand surfaces, remove dripped glue, etc.)
What's Left (W/ regards to everything else):
-MAKE SURE CG IS IN THE PROPER LOCATION
-Finish pre-flight checklists / abort criteria
-Extensive electronics testing (ex. installed thrust test, servo loading, etc.)
-Taxi tests
-MAIDEN
I'd also like to know your guys' thoughts about the new image formatting. I feel like the "thumbnail" size is too small, but the "Full image" option takes up the whole screen. About halfway between, on the old site style, felt like the sweet spot. Coincidentally, this seems to be about the size as the video in the post above, at least as I remember it. Not too intrusive, but not too small as to hide detail.
The neck section is extremely strong now. I have no doubt that it'll be able to hold the nose filled with batteries, but now I'm concerned with all of that weight being held by two foam spars.
I also redesigned the retract mounts so I could remove the units themselves to secure the pins. The oleos don't twist anymore, the rest of the slop is where they meet the bogies, which is negligible. I've decided to forego the gear doors for now, mainly because they proved to be way to much of a hassle to get right. I'd rather get the plane flying first and add them later.
What's Left (W/ regards to building):
-Final alignment of the Mains
-Receiver hatch
-Sheeting of the cockpit/nose area
-Hollow out the front fuselage for the batteries
-Get the wings to fit tight, add mounting screws in the spars
-Clean everything up (Sand surfaces, remove dripped glue, etc.)
What's Left (W/ regards to everything else):
-MAKE SURE CG IS IN THE PROPER LOCATION
-Finish pre-flight checklists / abort criteria
-Extensive electronics testing (ex. installed thrust test, servo loading, etc.)
-Taxi tests
-MAIDEN
I'd also like to know your guys' thoughts about the new image formatting. I feel like the "thumbnail" size is too small, but the "Full image" option takes up the whole screen. About halfway between, on the old site style, felt like the sweet spot. Coincidentally, this seems to be about the size as the video in the post above, at least as I remember it. Not too intrusive, but not too small as to hide detail.
Namactual
Elite member
Pieliker96
Elite member
Saying it's been a while since I last updated this thread would be an understatement.
I still expect to finish this plane and maiden it before FFE, but some issues have come up that will make that a little more difficult:
-The voltage drop across such a long run of wire from the batteries to the ESCs, especially at such a high current draw (~300A), is massive.
-The nose will have to hold 2kg of batteries (~35% of the plane's weight)
To remedy this, I'll be doubling the amount of battery wiring currently in the plane (going to 8 runs of 12-gauge solid core total) and rebuilding the entire nose section with better load-bearing capability. This will also allow me to add canard flaps if I can find a servo extension long enough, now that I have a proper programmable radio.
I still expect to finish this plane and maiden it before FFE, but some issues have come up that will make that a little more difficult:
-The voltage drop across such a long run of wire from the batteries to the ESCs, especially at such a high current draw (~300A), is massive.
-The nose will have to hold 2kg of batteries (~35% of the plane's weight)
To remedy this, I'll be doubling the amount of battery wiring currently in the plane (going to 8 runs of 12-gauge solid core total) and rebuilding the entire nose section with better load-bearing capability. This will also allow me to add canard flaps if I can find a servo extension long enough, now that I have a proper programmable radio.
Pieliker96
Elite member
Fuse prior to sheeting, with canard flaps.
There's plenty of space for batteries, with 10" of adjustability fore and aft.
The original two foam spars probably won't cut it as an attachment method, so I'm reinforcing them.
There's plenty of space for batteries, with 10" of adjustability fore and aft.
The original two foam spars probably won't cut it as an attachment method, so I'm reinforcing them.
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Pieliker96
Elite member
Got the wiring upgraded, twisted together to avoid electrical interference.
I also added 14 gauge silicone leads to the end of the wiring to make them more flexible, making the batteries easier to plug in.
I also installed the flaps servo and linkages. It's on a 3-position switch, giving me 0° , 15° or 30° of delfection.
I also added 14 gauge silicone leads to the end of the wiring to make them more flexible, making the batteries easier to plug in.
I also installed the flaps servo and linkages. It's on a 3-position switch, giving me 0° , 15° or 30° of delfection.
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Pieliker96
Elite member
I hope to maiden before FFE, but it's coming up fast. The only thing that really need to get done for the plane to fly is sheeting of the fuse, but I expect the smaller bits (wing mounting screws, receiver hatch, final landing gear alignment, and other bobs and ends) to still take a significant amount of time.
I slid the front fuselage into the main section and then put the batteries into their farthest-forwards position. This puts the most stress on the interface between the two parts, and I'm glad to say that it doesn't flex at all, even when rocking the plane back and forth on its gear. I also used some nylon spacers to preload the nose gear spring, as it was nearly bottoming out from the load. I'll leave the batteries in for another hour or two to see if anything begins to sag and then inspect for wear, but everything looks good so far.
I slid the front fuselage into the main section and then put the batteries into their farthest-forwards position. This puts the most stress on the interface between the two parts, and I'm glad to say that it doesn't flex at all, even when rocking the plane back and forth on its gear. I also used some nylon spacers to preload the nose gear spring, as it was nearly bottoming out from the load. I'll leave the batteries in for another hour or two to see if anything begins to sag and then inspect for wear, but everything looks good so far.
Pieliker96
Elite member
Made some progress on sheeting.
