35" Xb-70 - RC Groups
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Jun 18, 2008, 01:08 PM
agriebel's Avatar
Build Log

35" Xb-70

Not wanting to hijack hellrazor_77 build log I have started my own. It is a slightly larger build with a wingspan on 35" rather than the 25" hellrazor is doing. it is based on Steven Wongs plans and fuelsguys plans. I have most of the parts cutout. I ran out of depron and have to wait for more to come in. I am in a building mood also!

Not many parts, should be a quick build. Canard up front, but I forgot to not cut the elevons out to the tips of the wing, so no wing tip droop for me. I plan on following hellrazor_77 bomb bay technique and add a bomb bay. I guess a cruise type missile might be the best choice for something to drop.

I am thinking about making the nose solid rather than hollow. Should give me more room for shaping the nose.
Last edited by agriebel; Jul 31, 2008 at 07:47 AM.
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Jun 18, 2008, 01:20 PM
agriebel's Avatar
Because of the size (60" long), it would be difficult to hand launch so I plan on setting up a dolly landing gear arrangement like hepdog did on his SR-71.

Power will be provided by a Little screamers super park jet with a 7x5 prop and thunderpower 1320 battery.
Jun 18, 2008, 11:41 PM
Supersonic hover
Esprit440's Avatar
Cool project - I just happened to run across this XB-70 site today, really fascinating. Good luck!

Jun 19, 2008, 08:27 AM
agriebel's Avatar
Wow, I learned more new info about the XB-70 in that article than I had previously known...thanks
Jun 20, 2008, 08:10 AM
agriebel's Avatar
The depron came in and I am at it again. There was a previous thread where the person was confused about the notches in the bottom of the fuselage sides. He didn't know what they were for. When the plans were tiled the notches were removed. Well, it turns out that you need those notches. The neck of the fuselage sets on top of the wing. So, what the notches do is allow you to glue the fuselage bottom to the sides then attach them to the wing and get a smooth line.

Also the plans show the whole forward canard moving like a taileron, however if you look in the picture you can see that it is clearly set up like a horizontal stab and a conventional elevator.
Jun 20, 2008, 12:20 PM
agriebel's Avatar
I have been thinking about the wingtip droop and was never happy with the other system that was developed. It required 2 servos and looked like there could be some slop in the mechanism. I came up with a different way that only requires 1 servo and is really tight. Best of all, it is simple!
Jun 21, 2008, 08:30 AM
agriebel's Avatar
More progress today. Glued the wingtip pushrod tubes into position. Cut a small slot to make it fit in the wing better. Also glued on the sidewall doublers.
Started working on the truck type landing gear. I'm just now sure the best way to attach the landing gear frame to the fuselage.
Jun 21, 2008, 02:45 PM
agriebel's Avatar
Update on the notches! The notches caused a problem, there was a large gap on the bottom of the fuselage caused by the notches. So, I recut the pieces without the notches. But that is not exactly right either. If you look at the fuselage attachment on the real aircraft you see there is a gap between the fuselage and the wing. So, the notch is correct if you want that gap, it is just in the wrong spot. It was too far back. I recut it and now it fits great.
Jun 25, 2008, 01:08 PM
agriebel's Avatar
I have made some progress today. Test fitted the elevons and wing droops. Then reinforced the upper fuselage with some basswood and epoxy. Looks like about 15oz without battery or paint.
Jun 26, 2008, 12:24 AM
Registered Plan-a-holic
Hepdog's Avatar
WOW, I didn't think many of my ideas were useful Thanks.

This has been the best dolly I have ever built - 20+ flights and not a single hang up or glitch - even on rough grass.

Whatever you want to know just ask.

Here's 2 interesting pics showing liftoff - very cleanly. The XB 70 should do the same.

Nice build BTW
Jun 26, 2008, 12:46 AM
corsair nut's Avatar
hep, those are AWSOME pics. that is one GORGEOUS SR.
Jun 26, 2008, 07:28 AM
agriebel's Avatar
That's the great thing about this site, you pick up bits and pieces from other builders that you can use on other birds. I've always admired your Black Bird projects. Some really great work that has helped to inspire me.
Jun 26, 2008, 09:01 PM
agriebel's Avatar
The servos for the elevon's and wing droop are mounted along with the servo for the canard. I had some problem getting it setup correctly. My spektrum receiver has a channel labeled aux1 but when I tried to mix elevator with aux1 all I could find in my spektrum transmitter is aux2. I ended up mixing it with the rudder channel and reducing the rudder end point to zero. That way if I bump the rudder I don't get elevator!
There is a video of the wing droop movement here https://www.rcgroups.com/forums/show...5#post10034524
Jun 27, 2008, 04:28 PM
agriebel's Avatar
Some progress today. Glued the upper fuselage to the wing and attached all of the control surfaces permanently. I need to finish up the landing gear so I can place the supports for it in the lower fuselage. I came up with an idea for the engines. I'll post it when I get it finished.
Jun 27, 2008, 04:40 PM
corsair nut's Avatar
ag, looking good dude! a couple things though...regarding the SPJ...have you run it on that e-fltie esc yet? reason i ask, was that mine didnt run well, err all all on that esc. the CC TB 18 or 36 will work GREAT with it. also, airflow..tha motor wont be getting any airflow at all like that...with SPJ's its pretty criticle that they get good flow. id suggest getting some cooling to her. try a stick mount, they work best for cooling, as they dont block the air.

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