XB-35 Flying Wing RC Model

[jjr2001]

Time for some more build pics.
First photo shows a bus connector made from two terminal strip contacts. With 4 positions I can connect 4 #12 wires in parallel and be able to later unconnect them. I need 4 sets of these to connect the 4 speed controllers in parallel with the two batteries that I plan on using.

Second photo shows the primary battery to ESC (speed controllers) wiring with all 4 bus bars completed and heat shrink tubing applied.

Third photo shows the control signal wiring harness in the very back of the receiver area. That bunch of wiring is just to feed the signal to each speed controller and to provide power to the receiver. A diode has been added to isolate the power feeds from the ESC's to the receiver. With this setup I have 4 redundant power supplies that are diode isolated to power the receiver. I can loose power from three ESC's and still control the surfaces and steering.

Fourth photo shows the access hatches (3) for 2 batteries and 1 receiver. The cooling inlets are visible on the leading edge that has been partially formed.

Fifth photo is the present state of affairs with most of the wing sheeting complete. Like waiting for paint to dry!

Sixth photo is the 1/8" music wire landing gear. No retracts on this one.

Cheers, JR

[PJs]

Oh My JR, That must have been a site and a good package check after. Funny sometimes how we learn about physics! Back in my days the ST60 was about the biggest you could get and remember it having just over 1hp. I see now the 90's have 2.5. Also remember experimenting with props on Dad's Rat Racer and seemed like we went just undersized with a 10x8 because we started mixing our own fuel then and could spin it a little tighter and get more giddyup once up in the air. Dad was POL officer then and knew such things and got the Sembach club on board because it was cheaper than premixed by a long shot. I still love the smell of nitro, castor oil and model airplane dope...but don't miss the prop dings when we went to nylon props, but more costly if you augured in...cranks aren't made for that kind of abuse.

We used the McCoy's for my B Rat, combat and balloon bust because of that giddyup, but used Fox's (25-40's) for stunt back then. Didn't do too much with .049's till we came back to the states but did learn to fly with one...I glued that thing back together till the splinters were to small to work with. Seemed like I was caught in a continual loop from launch...ground hog day at it finest. They can be real fun but a bit persnickety in my book, especially that Super Bee.

I had a couple of question about your XB-35 build (Beautiful BTW) and the extended shaft lengths on the motors. Are there any mid support bearings on them and How fast are you going to spin them? I can see now how valuable your layout/gluing table is!

about all I did for the build was take the lawnmower engine, strip it down to almost nothing polish out the exhaust ports, radically rework the intake and the reed valve add a larger carb and a hotter spark plug them machine a hub to mount the prop

Taking no credit eh, ~¿@ for lifting your friend off the ground with a Xhp Clinton Dragon Mower you built...Good one Frank! Amazing build and story!!

[C-Bag]

Thanks for the vids JR! That sound.....wow. I kinda don't get those things control line or R/C, no throttle and going like crazy. The first video of the pulse he said it went lean, dunno. He was a lot jerkier at the controls than I ever saw John(the pulse jet owner) ever get away with. Any quick movements caused bubbles in the fuel line and that made it shut off. And yeah, it was a dragon by the tail and he had to really lean into it to not get dragged around.

I've tried to fly some of those fast things on RealFlight and its crazy how quick it gets to that range where you can't tell which way it's headed visually. And you can cheat in RF and use the little magnified window to see which way it's oriented. In real life do you have somebody with binoculars helping you out? Truly above my pay grade and insurance rates as if you lose it at that speed you could kill somebody.

The only challenge my uncle ever got whipped by was R/C choppers. When he passed his will said I could take pick of either his Kavan Jet Ranger or Ugly Stick w/an Enya 60. I took the Ugly Stick. Never flew it, never felt like I was qualified and the whole drive for R/C left me after he passed. But that Ranger 'bout killed him for real. He had my cousin holding the box while he was tuning the engine with it tethered. He wanted her to adjust the throttle and she hit the cyclic and the rotor clipped his arm! Took many stitches to close his arm back up.

His first copter was an egg beater with a chain saw engine. He had just graduated from the tethers and was hovering successfully and all the sudden it went to full throttle and forward. He ducked out of the way and everybody else scattered except of his tiny wife who ran between two parked cars directly in front of it. She just cleared the cars and it plowed into her basically flat, vertical, whatever. She ended up on her face with it on her back with body spinning frantically. She was completely unscathed. Talk about lucky!!!

Great update pix JR. There is a lot of stuff that is not evident after the plane is built. Like all the wiring and the extension shafts on the motors. Also the air intakes for the cooling of everything.

[jjr2001]

PJ, I never brewed my own fuel but I did make some nice match head rocket motors. Great fun. I had some seamless aluminum tubing and plugged one end with a rounded dowel rod. Then stuffed the thing full of match heads. Used some hobby rocket motor fuse and light her off. Actually it was more like a mortar since I used a 5 foot length piece of 3/4 inch galvanized pipe for the launch tube. Woooosh and I could never find any of them. The made a nice smoke trail and again you could hear the leaves being ripped through.


I do have extensions on the motors. They are 1/8 music wire encased in 5mm carbon fiber tubes. Took a couple of attempts to get them straight but they seem pretty good now. No center supports. I added one bearing for each shaft at the back end and used locktite to fix it to the music wire. Crazy fast on the motors. They are rated at 2200 Kv. So for each volt they rotate at 2200 rpm. With my 12 volt batteries they have a no load speed of 26,000 rpm. The props are small 3 blade 5x4 so they really need to spin up to get much thrust.

C-Bag, When the speed gets over about 90 mph I know it is not for me. Heck, I can loose orientation of my plane when it is going slow! I try to keep them in fairly close and keep the speed to 60-80 mph most of the time. I am not a speed guy. I have seen electrics pushing 160 mph and once a guy was flying with a glow engine at over 200mph. There are so many things that can and do fail on these models that I just don't care to fly that fast myself.

The choppers are like flying swords. I saw two of them disintegrate at an RC flyin on the same day by the same guy. Seems he was missing the fasteners for the body. He started to really put on a show and the body hit the blades. Blades ended up 100 feet from the point of impact. Half hour later he was at it again and the same thing happened. Quick way to loose $1000.

[C-Bag]

Wow, JR the chopper guy was rich or something. How do you jump right back at it after something like that, or am I just a sissy? And then have the second one eat it and it sounds like in the same way. Some folk just don't have the patience or OCD to build a long project like a chopper or an all balsa build like your wing. My brother was one and he had the good sense to know that after he had an engine mount he didn't dowel after gluing come off. Luckily there was nobody in front of it, but after that I did the building, he did the flying. He was 100x's the pilot I was but he had no patience for building. I also did the engine polishing.

How did you decide on CF tubes to run the motor shafts through, and what are you using for lube? Good job on the gear and your wire former. This might be out in left field, but I've been using an old HF bushing driver kit I've had forever to form the different radii for my rod and wire projects. It's a easy way to pick and choose when I want a different radius. I first came on that when I wanted to make a new oven rack for my powdercoat oven bending 1/4" rod. And ever since it's really come in handy for all kinds of bending and forming.

Curious about CG, was it marked on the plans? Got to be super critical on something this radical I would think.

[PJs]

Thanks for the updated Pics JR! I can see it's been a ton of work to wire all that up and keep it neat, let alone handle those currents. Nice job on the 12Ga. coupler's! Was surprised to see the magnets for the hatches. I assume they hold up well in flight and keep the weight down. I don't have a good feeling for the length of those extension on the inboard motors but seem to me at those RPM's you could get some whip in the middle. Is the CF tube like a sleeve bearing with an ID of 5mm? Good idea on the loctite to the inner races to handle the torque and speeds. Looking forward to your next pics of the build!

Unfortunately I have to admit to a short stint in match head rockets/grenades. Still have all my body parts thank goodness. We used empty CO2 cartridges with the cap removed...it's a wonder we didn't lose a hand packing those things. Biggest was 3 strapped to a dowel and some how managed to light all three pretty close together...I think it ended up in the following week sometime/somewhere. Never found ours either. Did get into rocketry in college out in your neck of the woods because of the desert....chased them down on dirt bikes, Way Fun! Later when my son was about 8-9 we got into them again...great fun and after a year or so he built a beautiful FireFox and I built an SR-71. He took his to show and tell at school and the teacher called me to see if we would do a demo for the class. Was very cool and 2-3 classes set up in the bleachers and we lit off 3-4 for them, including the SR-71. They loved it and we got a charge for sharing our fun with them. Think he was a hero of the class after that.

Funny thing is my oldest Gson got a kit for Christmas and now my sons candle has lit again and wants to dig them out of storage. Guess I will, because you are lighting mine with this model stuff again, although I have enough projects to keep me busy till I kick...but do like the twinkly lights and fun from the past. Think I still have a couple of Jasco/Jetco glider kits and other plans in storage as well as that old PT22 too.

Think I had my fill of scary choppers and speed would be an issue with me any more. Although I remember the A Speed guy's back in the day running berrylium pans on mono-lines. I did get to fly a club friends B Speed on mono-lines...got to be steady with that stuff and not over react on the push/pull. Dad's Rat was fast enough for me and that was on 100' lines...can't imagine doing that RC!!

I'm curious too about the CG on a Wing and what about torque from the motors...are they counter rotating? Also is there some kind of sync controller for them?

[jjr2001]

C-Bag,

Thanks for the bushing driver idea. I checked one out at HF and for $10.00 it is a quick way to get various radii.

I was fairly sure that the 3/32 shafts that the designer specified would have a tendency to whip. Actually the 1/8 music wire was pretty floppy also. So, I just used epoxy and added the CF tubes to the shafts. Quite stiff and I did not need bearings other than the prop end. Seems pretty good so far. CG is marked on the prints but I always look at that as a starting point. We will find the real CG in a grass field near the house prior to flight..( If I can get up the nerve to throw it!).

I think the chopper guy just wanted to perform for the crowd for the air show. It was an electric 4 day event and it was chopper time. They were limited to a 1 hour show each day at noon. The rest of the time it was all planes all day. Fun but with over 200 people there you did not get much time to fly and it was a bit dangerous. One day a fellow from Chicago was hit in the head by an electric A-10 that was taking off. Put 20 stitches in his head. Next year the same guy from Chicago was back and in the porta potty.....Someone hit that porta potty with another jet...Man did he get out of there. From then on he was known as an EDF magnet....

Cheers, JR

[jjr2001]

Hi PJ,

The magnets are the neo type and they are extremely powerful. These are small .250 dia and maybe 1/16 thick. They are placed back to back so there are two magnets at each station. They hold so hard that I had to put a 6-32 blind nut in each hatch so that they can be removed. If this plane was going over 100 mph I would use rods for the front into a bulkhead and magnet the back side only. I tried to balance the torque on the motors by having them rotate cw and ccw on each side of the wing. Should be able to loose one, cut power and limp home.

The CF tube is about 5mm OD and about .125 ID. They are a fairly close sliding fit for the 1/8 music wire. Quite stiff once cured and I have not noticed any tendency to whip. I think they will work ok.

Co2 cartridge match head rocket! Wish I could have been there. SR-71 sounds very neat. Could add a small receiver and servo so it would be guided upon "re-entry".. Great fun.

My control line efforts were limited to the Ringmaster type with a .35 motor. Thought I was doing great to make figure 8's so I did not have to get dizzy going in circles.

I know what you mean about enough projects to last a lifetime. I am in the same boat...(airplane?)

Cheers, JR

[jjr2001]

Picked up a fresh can of DAP LWS or light weight spackle for grain filler and after two sessions with that and some sanding we are ready for paint. I can't find the original DAP LWS anywhere. The new "improved" type has "primer" in it "so you do not have to prime" and that is hog wash. The original DAP would dry much faster and was very good at filling grain. It would last much longer in the can than this "new improved" variety. Oh well, I guess you just get to buy a new can of it each year! Oh yea, you still have to prime this stuff or you will get a very rough finish...

Landing gear has full time constant "adjustable" friction brakes installed. They are quite simple using aluminum for the plates and a bit of velcro (smooth fuzzy side only) applied to the aluminum plates. Friction is set when you install them. I only need a small braking force but I like to install two of them on the mains and not the nose wheel. It allows me more latitude on where I can touch down on the runway so I don't run off the end. Brass tubing was used for bushings for the plastic hubs.

Now if it would just warm up a bit.

Cheers, JR

[C-Bag]

Makes you wonder what's up with products like that. Is it an EPA reg or just cutting corners to add a couple of cents per unit or somebody just had a bright idea? Either way they always make it sound like it's an improvement which it seldom is and there's just too many products that if they'd leave it alone and spend less on useless advertising they could actually make the 2c that way.

I'm trying to think back how we made filler/sealer. I don't think we bought any(too cash challenged). I just assumed you'd mono coat the wing(is that dating me?) but with electric you don't need special paint like dope do you? Looks like you're going to spray it, that's why the mention of the temps eh?