Official Freewing B-2 Spirit Bomber 86" Twin 70mm EDF Jet

[F106DeltaDart]

A few more detail shots of the gear modifications

[F106DeltaDart]

As I still haven’t had the time or weather to maiden my B-2, I’ve continued working on some mods to the landing gear. I finished up moving the nose gear forward and have installed a servo to control the nose gear door. Since that change effectively shortened the nose gear by around a 1/2 inch, I decided that I’d need to shorten the mains to get enough AOA for takeoff. The shorter mains would also look more scale. There was just one problem.. If I shortened the mains by 1/2”, the folded gear trucks would hit the retract motor. I decided to do something I have done successful a few times before the remedy this; flip the retract to fold the other way around. I did this on my FMS P-39 mains which had a very similar issue.

After a few hours with a belt sander and some leftover styrene, I was able to reconfigure the retracts to fold away from the motor. I then shortened the struts by a 1/2”, re-tapped the set screws, and reinstalled them on the model. Then I realized that with shorter gear legs, I could move the retract units mounting point a bit farther forward. I did this by using the forward screws in the stock mounting plate to mount the aft retract screws, and adding some plywood to mount the forward screws. While it was a lot of fiddling (most of the day), I’m pretty happy with how it turned out. I’ll get to detailing the cockpit next with some more scale sized 3D printed pilots. Here’s how it looks so far:

[James]

Hey guys! Sorry I have been absent but it was with good reason. Alex and I spent the week onboarding our newest marketing team members, Wesley and Lori Miller of the Merry Boozers. They are now officially working for Motion RC and will produce more content, helping us better attend events and provide you with more information on all our RC products.

Let's welcome Wesley and Lori to the Motion RC family!

Wes and I had so much fun formation flying the B-2s and look forward to bringing you more content! Have the CG correct and 10% throttle and she lands slow and gentle.

I have some catching up to do in the threads, but we filmed our maidens and such and I will provide my write-up either over the weekend or Monday.

[xviper]

Warning: Some may consider this post to be a bit off topic, so skip it if it offends you.

Comparison between the B-2 and X8 flying wing.

This is about my old X8 Skywalker flying wing from many, many years ago. Went over some of my older YouTube videos and found quite a few vids of this plane. I flew it a lot and did all kinds of experimenting with it. I bring this up because the B-2 bears a vague resemblance to the X8. They are both about the same size (B-2 is 80mm larger wingspan), so I can compare things like flight characteristics, visibility, landing style and effectiveness of airbrakes on landing. I find it an interesting comparison.

The X8 wingspan is 2120mm, black with fluorescent markings for better visibility, pusher prop, big winglets, pop up airbrakes, flying weight was over 3000g with a 5000mah, 6s LiPo (similar to the B-2) but could haul as much as 20,000+mah, no gyro back in those days.

X8 was a big, floaty wing that was able to float "forever" as I'm sure the B-2 also can. Back in those days, on a native reserve I got the X8 up to 3100 feet (with several spotters helping). It took nearly 5 minutes to get up there and over 11 minutes to glide back down, no power. As far as visibility was concerned, those fluorescent markings faded to grey at about 200 - 250 feet. Nevertheless, even though it was barely visible at 3100 feet, there was no mistaking what it was doing and in which direction it was flying. I believe it was primarily due to its shape. (This was at a time when an aerial video survey company was doing autonomous flight testing with the X8 at the same flying site. They launched theirs with a very large, powerful and dangerous catapult.) With a 5000 battery, it could fly for an hr, with minimal throttle and good use of the glide. With 20,000+ mah on board and a load of equipment, it could fly 50 miles out and 50 miles back and land.

Landing was tricky until one got the technique down. The X8 suffered from ground effect once it got to about 3 feet off the deck. When you thought it was about to touch down, it would continue to glide for another 50 to 100 feet. Bringing it down with elevator became a very abrupt maneuver, oft-times resulting in a "slam dunk". Installing airbrakes and using them at the right moment helped tremendously with the landing - made it nearly child's play.

I mentioned about the potential for squirrelly ground handling of the B-2 because another guy put retracts on his X8 and the configuration looked very much like the B-2 - very short wheelbase, very "darty" on the ground roll. It did NOT do well with wheels. The fact that this B-2 appears to be solid on the ground is a testament to what went into it.

With those fairly large winglets, the X8 was extremely stable with no hint of a wobble, even with no gyro. There was no yaw capability, just a "bank and yank" plane but it worked very well. Banked turns were graceful and tracked solidly thru the turn - didn't need yaw control.

Here is one flight of my old X8. I'll only leave a link so don't click on it if you don't like the idea of this post.

https://www.youtube.com/watch?v=fGBj5pEo8fI

[xviper]

With 55mm front wheels your raise the AoA by 5mm.

I'd love to hear how your grass ops go. I don't really need bigger wheels for my GeoTex runway but I like the idea of a higher AoA for this wing and how it will affect the way it takes off. I have a box full of wheels that I could try primarily for the front. I also like the "Big Wheel" look. Reminds of the Big Wheels for kids back in the day. Goofy looking but cute. (Yeah, I'm ready for the scale police to come for me.) I won't mess with the mains (bigger tires) as I really like those as they are.
I can take off from grass with my stock AL-37, so I might give that field a go with the B-2.

[GliderGuy]

Thank you - that makes perfect sense! So 45mm diameter it is - (and I assume the axle diameter is 4mm?)
So does anyone have recommendations for an equivalent 55mm wheel (preferably Freewing) having a similar width and style that will easily fit inside the B-2 gear cavity?

See posts #536 and #552

-GG

[ridgerunner]

That is the description of the plane, not the part. Twin 70mm B-2 Spirit Bomber is in front of the part listed so you know what it fits. That is not the wheel measurement.

Thank you - that makes perfect sense! So 45mm diameter it is - (and I assume the axle diameter is 4mm?)
So does anyone have recommendations for an equivalent 55mm wheel (preferably Freewing) having a similar width and style that will easily fit inside the B-2 gear cavity?

[crxmanpat]

I am now confused - the B-2 spare parts page lists the main and nose gear wheels as 70mm.
So what are they - 45mm or 70mm? (I'm guessing that the MRC product pages for the gear diameter is incorrect, but I'd like to know for sure. My B-2 is scheduled to arrive tomorrow.) I'd like to order some equivalent style larger nose wheels that will easily fit into the nose gear compartment without any modifications. Note that I'll be having the nose gear steering servo on its own dedicated channel that will remain in a fixed centered position when the gear is retracted (it will be tied to the rudder stick with a LOT of expo and only steer when the gear is down).

I think all wheels on the B-2 are 46mm.

[JamesonC]

I am now confused - the B-2 spare parts page lists the main and nose gear wheels as 70mm.
So what are they - 45mm or 70mm? (I'm guessing that the MRC product pages for the gear diameter is incorrect, but I'd like to know for sure. My B-2 is scheduled to arrive tomorrow.) I'd like to order some equivalent style larger nose wheels that will easily fit into the nose gear compartment without any modifications. Note that I'll be having the nose gear steering servo on its own dedicated channel that will remain in a fixed centered position when the gear is retracted (it will be tied to the rudder stick with a LOT of expo and only steer when the gear is down).

That is the description of the plane, not the part. Twin 70mm B-2 Spirit Bomber is in front of the part listed so you know what it fits. That is not the wheel measurement.

[ridgerunner]

Bigger diameter wheels
I too have a grass rwy and I suspected some take-off problems, so 2 days ago I looked at the front wheels. Those are 45mm diameter, you can easily change those with 55mm diameter (which I did already) there's plenty of space in the front gear bay to install even bigger wheels but more than 55mm will rub/bind them against the bottom of the wooden battery floor.

The wheels of the mains can be easily changed to 50mm diameter instead of the stock 45mm diameter.

I'd like to give it a try but our grass rwy won't be accessible untill mid next week.

With 55mm front wheels your raise the AoA by 5mm.

I am now confused - the B-2 spare parts page lists the main and nose gear wheels as 70mm.
So what are they - 45mm or 70mm? (I'm guessing that the MRC product pages for the gear diameter is incorrect, but I'd like to know for sure. My B-2 is scheduled to arrive tomorrow.) I'd like to order some equivalent style larger nose wheels that will easily fit into the nose gear compartment without any modifications. Note that I'll be having the nose gear steering servo on its own dedicated channel that will remain in a fixed centered position when the gear is retracted (it will be tied to the rudder stick with a LOT of expo and only steer when the gear is down).

[kallend]

I wish to correct some information. It was NOT Pittxxxxx that was able to make the HE programmer work but was another person whose post I have linked below. (I still think Pittxxxxx is "odd" but that's another story.)
https://www.rcgroups.com/forums/show...&postcount=695
It should be noted that she (I think it's a "she") was using an A3S2 programming card, so a big goes here.

The A3S2 card is not compatible with the A3S3 one. They even have different USB connectors so I'm not sure how the cable would work.

Anyhow, it could be that E52 is A3S2 based, I suppose, all the connection to the Rx are the same.

[KevinMar]

This plane is sweeeet!

Maiden + 2 more flights today! I don't think this will be coming with me every time I go flying, but she sure is a special bird.

Maiden was uneventful. I forgot the vertical stabilizer at home, so I just used my field's ID badge (credit card) as the stabilizer, and it worked just fine. I chose my 3 oldest batteries for this bird because I know she's just meant to be a cruiser, and she did just fine.

I had some moderate winds with gusts, so sometimes the B-2 would become a bit more pitchy than expected (when in head wind), but I really didn't feel any bad tendencies in any of the 3 flights. Most interestingly was that I could not feel any yaw washout at all. Very solid flyer.

Landings weren't difficult, but they were different. Can't do a standard EDF jet glide slope with a flare. I found that bringing it over the runway nice and level with only a last inch flare (if any) was best. She sits down on her mains as they articulate, and then the nose touches down pretty quickly. Not difficult, just different.

Happy flying everybody!

[Gravythe clown]

So after all the videos, I decided on one mod before maiden, I agree the siting AOA is to flat. My last B2 had a little more upward nose AOA and she lifted her self off with no effort. I’m guess this may also be why for the addition up trim suggested. All the videos I’ve seen so far are pop ups.
so I too found some 10mm in my stock taller wheels and threw them on. Doors still close and now I can see a noticeable AOA as she sits.

I’m wanting to maiden her this weekend but looks like another high wind and possible rain. If I get dunked out I’ll spend the time building my Combat reaper. It’s been to long that I haven’t gotten up in the mess with the guys.

Gravy

[xviper]

That guy Pittxxxxxx made it work on the second power up with the HE programmer. However, I think he's a bit "odd", so who knows exactly what he did or saw.

I wish to correct some information. It was NOT Pittxxxxx that was able to make the HE programmer work but was another person whose post I have linked below. (I still think Pittxxxxx is "odd" but that's another story.)
https://www.rcgroups.com/forums/show...&postcount=695
It should be noted that she (I think it's a "she") was using an A3S2 programming card, so a big goes here.

[xviper]

I dont think you will need it unless you separate the steering from the rudders. I ground tested and the aircraft steers great at full throttle when the aircraft is set up correctly. I did not test to see if when the gear are down if the gyro also corrects the steering along with the rudders.

I'm at a loss to explain why Amahoser's plane was wandering so bad. Is his an exception to the "norm" for this plane? Even though we see that the rudder gain is at 100%, I'm curious how this relates to the set gain in an Assan steering gyro. Perhaps 100% gain in an "air" rudder is meaningless for a steering wheel. I'm looking at the Pulsar gyro from X-Fly and it has a separate plug for the nose steering. If the setting for the air rudder was applicable for the nose steering, then why use a separate circuit? However, the Pulsar does recommend to start with 30% gain so perhaps 100% gain for the B-2's rudder may in fact, be enough for ground steering correction.
Anyway, I'll get to see first hand when my buddy maidens his what the ground handling looks like. Mine won't get here till after that happens (unless winter drags on).

[MeyerVW]

Mine will get the Assan steering gyro before it goes to the field. It's already waiting on the table for its new home. I've been very surprised by all the videos that this plane doesn't do the wandering minstrel thing. It's got such a short "wheel base", I would have expected it to wander all over the runway.

I dont think you will need it unless you separate the steering from the rudders. I ground tested and the aircraft steers great at full throttle when the aircraft is set up correctly. I did not test to see if when the gear are down if the gyro also corrects the steering along with the rudders.

[kallend]

I hear you, good point, although I will say that I won't use a battery with individual cell IR over 3. The SMC's are all in the 1.5-1.8 range and my "worst batteries" the HRB's/Roaring Tops/Admirals are in the 2-3 range (never use them anymore). I've not left the GT power meter hooked up in flight and yes, as the voltage drops, so does the Ah/Watts, as I've also tested them on the bench at 50% charge, but with a decent battery, it is not dropping down in the 90 Ah range. I'm no expert on EDF's, but I can tell you the the twin 70mm E-Flight fans EF2860-1850 Kv inrunners that came stock in the SU-30 were horrible fans and 1/2 the time I could not get it off grass. A fully charged 6000 still produced 120Ah and about 2800Watts, and at 50% charge it was 107 Ah 2400 Watts. I know the FW fans in the B2 are much better than those and top end your at 100 Ah and probably 2500 watts. The 70mm FMS fans together in the SU-30, 151 Ah/3700 watts, and at 50% charge 138 Ah/3100 watts. If you're only pulling 100Ah on a fully charged battery with those fans, somethings not right. Bench testing is one thing, only a place to start at. Since I fly off grass, the only real indicator is ground speed on take-off and there the bench testing has confirmed actual in-flight results.

I'll get a power draw reading on Monday of the stock B2 fans with an SMC 5300 and let you know what we're getting as we're about to find out if it will get off our grass runway.

Ah is the abbreviation for Ampere hours. A is the abbreviation for amps (amperes).

[mshagg]

If the box configuration has the steering and drag brakes y-d then the nose wheel would be benefiting from that very high gyro gain on the yaw axis.

[xviper]

I did (as I do with all my planes) separate the rudder from the nose steering and have that on a different channel. I'll try an Assan steering gyro and see if that helps. Overall, very impressed with its flying abilities.

Mine will get the Assan steering gyro before it goes to the field. It's already waiting on the table for its new home. I've been very surprised by all the videos that this plane doesn't do the wandering minstrel thing. It's got such a short "wheel base", I would have expected it to wander all over the runway.

[Radar-Guy]

Radar-Guy , I'm not trying to be argumentative, I'm just trying to figure out if there is another reason you could not get off grass other the the gear (obviously could be a combination of things) because I'm in the same boat. Rudy just tested his above and you can see the results he got and just from the numbers you had, especially the batteries at 4 or > IR value when both of us use batteries in the 1-1.5 range, something didn't seem right. And only pulling 100 amps stabilizing at 90 amps just sounded way too low. You can see he's at least 20-25% higher. Is there any way your ESC is just not functioning correctly or lost it's calibration?

Neither am I. Saw Rudy numbers. I set up the ESCs as usual and my figures were in the same ballpark as the ones reported by Icarus. I will check some things here.