Pieliker96
Elite member
Thanks all. It's been great so far seeing you all at FFE.
Here's some pictures worthy of being full-sized:
The Other XB-70 Build | Valkyrie V2
Thanks all. It's been great so far seeing you all at FFE.
Here's some pictures worthy of being full-sized:
Namactual
Elite member
No, what ^^ he ^^ said!
kilroy07
Legendary member
Was there a maiden and I missed it?!
I was the guy with the red shirt in the cart that kept telling you to quit goofing off and get that thing in the air!
@Pieliker96
Wait, I just checked your profile, you're from Illinois?!!
Where at (I'm in Springfield!)
I was the guy with the red shirt in the cart that kept telling you to quit goofing off and get that thing in the air!
@Pieliker96
Wait, I just checked your profile, you're from Illinois?!!
Where at (I'm in Springfield!)
Pieliker96
Elite member
Not yet. There's still some cosmetic stuff to get done before that, I don't really have a set date yet either.
Yep, Chicago suburbs.
Pieliker96
Elite member
Final part of the build log. I'll do an overview of the entire plane prior to the maiden, which'll include every small detail for those who are looking to pursue their own giant-scale builds.
Pieliker96
Elite member
Not yet. I was actually planning to surprise you all with a video of the maiden to make up for my rather lengthy inactivity. I have it scheduled for the next day I have free that has good weather. Hopefully it'll be on my winter break before I have to go back to boarding school. i.e. within the next two weeks, assuming all goes well.
What have I been doing in the meantime? Some of my own projects, being away at school, college applications, finals, you get the general idea. Anyways,
Progress:
1) Full thrust test, simulating a worst-case scenario of amp draw. Max static thrust was ~3kg, around 65% of what I was expecting. not a biggie, since dynamic thrust matters more to EDF planes in-flight, but it'll mean that I use up a bit more runway on take-off. Worst-case estimated take-off distance is currently ~60 feet, with a ridiculous amount of friction and drag (See the video below @ 4:38 for calculations), so I'm fine with that. The thrust test was also designed to be a torture test for the batteries, as thrust (& therefore amp draw) is highest at zero airspeed. The thrust test consisted of:
-30s of full throttle, simulating a takeoff
-2 min of 1/2 to 2/3 throttle, simulating flying a pattern
-30s of 1/4 throttle, simulating an approach
-30s of full throttle simulating a go-around
-30s of 1/4 throttle, simulating a landing
Results of the thrust test:
-Battery voltage sagged significantly under load, likely contributing to the reduction in thrust. I am abusing these batteries a bit (supposedly 50C, although no battery can really attain those levels in practice) in order to attain my weight limit and takeoff performance. They were just warm to the touch after the runs. Not uncomfortably hot, but warm. The ESCs were slightly warm to the touch.
-Battery voltage rebounded very well under lower current draws. My flight will consist of a takeoff, a minute and a half of flying, and then landing, allowing for two missed approaches and one landing. I may extend flight time in the future if the plane proves to be easy to land or the proposed flight plan leaves significant unused battery capacity.
-Wow. This thing moves a lot of air.
2) Improved main landing gear. Instead of relying on gravity to tilt the bogies to their landing configuration, I've attached a total of six rubber bands to tilt them into place. They are attached to the strut using a plastic wire holder bit that is retained by a raised section of the gear strut.
3) Taxi testing!
More details in the video below, showing taxi testing and modified main gear. A bit grainy, will probably reshoot in daylight
To Do:
-Clean up wing attachment
-CG check (either by balancing or sum of moments, with gear up and down)
-Finalize rates, throws, expo, etc.
-Finalize checklists and stuff (who am I kidding? It's just a foam plane)
-Add extra capacitors on the battery inputs to the ESCs?
-Other stuff that I've forgotten but can't remember at the moment
-Send it
What have I been doing in the meantime? Some of my own projects, being away at school, college applications, finals, you get the general idea. Anyways,
Progress:
1) Full thrust test, simulating a worst-case scenario of amp draw. Max static thrust was ~3kg, around 65% of what I was expecting. not a biggie, since dynamic thrust matters more to EDF planes in-flight, but it'll mean that I use up a bit more runway on take-off. Worst-case estimated take-off distance is currently ~60 feet, with a ridiculous amount of friction and drag (See the video below @ 4:38 for calculations), so I'm fine with that. The thrust test was also designed to be a torture test for the batteries, as thrust (& therefore amp draw) is highest at zero airspeed. The thrust test consisted of:
-30s of full throttle, simulating a takeoff
-2 min of 1/2 to 2/3 throttle, simulating flying a pattern
-30s of 1/4 throttle, simulating an approach
-30s of full throttle simulating a go-around
-30s of 1/4 throttle, simulating a landing
Results of the thrust test:
-Battery voltage sagged significantly under load, likely contributing to the reduction in thrust. I am abusing these batteries a bit (supposedly 50C, although no battery can really attain those levels in practice) in order to attain my weight limit and takeoff performance. They were just warm to the touch after the runs. Not uncomfortably hot, but warm. The ESCs were slightly warm to the touch.
-Battery voltage rebounded very well under lower current draws. My flight will consist of a takeoff, a minute and a half of flying, and then landing, allowing for two missed approaches and one landing. I may extend flight time in the future if the plane proves to be easy to land or the proposed flight plan leaves significant unused battery capacity.
-Wow. This thing moves a lot of air.
2) Improved main landing gear. Instead of relying on gravity to tilt the bogies to their landing configuration, I've attached a total of six rubber bands to tilt them into place. They are attached to the strut using a plastic wire holder bit that is retained by a raised section of the gear strut.
3) Taxi testing!
More details in the video below, showing taxi testing and modified main gear. A bit grainy, will probably reshoot in daylight
To Do:
-Clean up wing attachment
-CG check (either by balancing or sum of moments, with gear up and down)
-Finalize rates, throws, expo, etc.
-Finalize checklists and stuff (who am I kidding? It's just a foam plane)
-Add extra capacitors on the battery inputs to the ESCs?
-Other stuff that I've forgotten but can't remember at the moment
OliverW
Legendary member
Can you release plans?
Pieliker96
Elite member
There aren't any complete plans, in the typical sense. I have a bunch of google sketchup files linked below, which includes the scaled CAD model that this was based off. The more simpler shapes (ex. wing profile) were transferred to the foam by hand, whereas the curvy bits (ex. fuse formers) were either laser cut or printed and traced (although sketchup's print scaling can be screwy sometimes).
All of the skins of the formers were gradually brought into a decent fit through trial-and-error.
A good bit of the craft was improvised, and the "plans" don't reflect those changes that I've made.
With that said, the "plans" can be found here.
All of the skins of the formers were gradually brought into a decent fit through trial-and-error.
A good bit of the craft was improvised, and the "plans" don't reflect those changes that I've made.
With that said, the "plans" can be found here.
Pieliker96
Elite member
Doing some final checks here as I wait for the weather to clear up. One of the limit switches in the right main gear broke, causing it to be stuck down. I'm not really willing to wait for a replacement to ship at this point, so I've trimmed the gear switch in my radio such that the gear is always extended. Not that big of a deal, but not ideal.
I've taken a look at where the CG should end up. Scaling my 6-foot long prototype up to this size gives me 25 inches back from the start of the main wing, although I expect that this is a tad bit nose-heavy of optimal. eCalc tells me 26in with the 23% MAC of the real B-70 and a ~11% static margin, which is not far off from my estimated values. To achieve this, the batteries have to be nearly as far forwards in the nose as they can possibly go - farther than I was expecting, meaning more access hatches will have to be cut.
I've decided not to use the canard flaps on the first flight because I don't want to have to deal with the potentially drastic changes in elevator trim required. These, of course, could be automated with a tuned mix during later flights. However, the first flight is simply planned as a quick "get up, get down" mission with as little configuration changes and distractions as possible in order to maximize the odds of success.
I've taken a look at where the CG should end up. Scaling my 6-foot long prototype up to this size gives me 25 inches back from the start of the main wing, although I expect that this is a tad bit nose-heavy of optimal. eCalc tells me 26in with the 23% MAC of the real B-70 and a ~11% static margin, which is not far off from my estimated values. To achieve this, the batteries have to be nearly as far forwards in the nose as they can possibly go - farther than I was expecting, meaning more access hatches will have to be cut.
I've decided not to use the canard flaps on the first flight because I don't want to have to deal with the potentially drastic changes in elevator trim required. These, of course, could be automated with a tuned mix during later flights. However, the first flight is simply planned as a quick "get up, get down" mission with as little configuration changes and distractions as possible in order to maximize the odds of success.
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Pieliker96
Elite member
Got a couple high-speed runs in today, see video below.
I had to bring the wings back into shape (they had warped over a year or so in storage), which was accomplished by using weights to form their underside to a flat surface.
I'm happy with the fitment of the wings and fuselage and think that they will be strong enough to take the loads of flight. The CG ends up in the right place now. I have 20% expo on the elevator, -20% on the ailerons (to counteract the effects of high wing sweep that I observed on my test model) and 30% on the rudder.
I had to bring the wings back into shape (they had warped over a year or so in storage), which was accomplished by using weights to form their underside to a flat surface.
I'm happy with the fitment of the wings and fuselage and think that they will be strong enough to take the loads of flight. The CG ends up in the right place now. I have 20% expo on the elevator, -20% on the ailerons (to counteract the effects of high wing sweep that I observed on my test model) and 30% on the rudder.
Pieliker96
Elite member
Had the maiden flight today. Overran the runway on landing, causing a nose gear collapse, nothing that isn't fixable. Overall very successful.
Video to come.
Video to come.
Paracodespoder
Elite member
Woohoo, it flies! Now pat yourself on the back and give us that video . JK, looks good, good job on the build.
. JK, looks good, good job on the build.
CarolineTyler
Legendary member
Congratulations! Looking forward to seeing the maiden video!
Pieliker96
Elite member
First impressions / preliminary analysis of flight characteristics:
-A bit underpowered, but can get up to a good speed. I likely flew faster and carried more throttle than necessary.
-A bit floaty during landing.
-Was pretty far out of trim. I didn't end up trimming it during the flight. I held quite a lot of down elevator, combined with quite a bit of both left aileron and rudder. Despite this, the CG felt spot-on.
-As is characteristic of a delta wing, flies at a really high AoA at low speeds. Looks like it's on the verge of a stall a good bit of the time, which is a bit scary.
-Wing-rock in the straightaways was a thing.
The batteries recovered to just over 3.7v/cell, meaning that my flight was nearly perfectly timed (allowing for more go-arounds), despite me forgetting to start my timer until after the first two turns.
Looking at the undercarriage view, two of the eight wheels on the mains were near falling-off. I'll secure these better, by proper wheel collars or some other means, for later flights.
The sun reflecting off of the underbelly was beautiful. I surprisingly wasn't that nervous during the flight, after having flown my FT-22 as a warm-up.
Photos:
Video:
-A bit underpowered, but can get up to a good speed. I likely flew faster and carried more throttle than necessary.
-A bit floaty during landing.
-Was pretty far out of trim. I didn't end up trimming it during the flight. I held quite a lot of down elevator, combined with quite a bit of both left aileron and rudder. Despite this, the CG felt spot-on.
-As is characteristic of a delta wing, flies at a really high AoA at low speeds. Looks like it's on the verge of a stall a good bit of the time, which is a bit scary.
-Wing-rock in the straightaways was a thing.
The batteries recovered to just over 3.7v/cell, meaning that my flight was nearly perfectly timed (allowing for more go-arounds), despite me forgetting to start my timer until after the first two turns.
Looking at the undercarriage view, two of the eight wheels on the mains were near falling-off. I'll secure these better, by proper wheel collars or some other means, for later flights.
The sun reflecting off of the underbelly was beautiful. I surprisingly wasn't that nervous during the flight, after having flown my FT-22 as a warm-up.
Photos:
Video:
