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Old Mar 22, 2014, 06:51 PM
Proto morlock
Australia, QLD, Brisbane
Joined Mar 2008
180 Posts
Build Log
BBCC4 - Steve Bage Bachem Natter

Amongst my stash I have a small stockpile of Estes rocket motors. For a bit of fun I thought I'd try a rocket powered build this time around.

Steve Bage was kind enough to send me a copy of his plan for a Bachem Ba349B Natter for rapier power. This is a redesign of Richard Crossley's plan that appeared in Aeromodeller magazine.

I'll be scaling up around 30% for a wingspan of ~280mm. I'll also be skinning in balsa and substituting ply in a few places to strengthen. The peak thrust of an L2 Rapier motor is 135mN, while the C6 motors in my stash top out at around 15N...

Estes quotes the max lift for a C6 motor as 113g. I'll be aiming for half that with an rx and a couple of micro servos.

Much like the original aircraft, the plan is for an uncontrolled boost, followed by a controlled glide. Luckily, the criteria for the contest is "proof of flight", not "proof of controlled flight"
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Old Mar 22, 2014, 07:33 PM
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United States, KY, Taylorsville
Joined Mar 2010
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Cool! You gonna put the motor in the tail?
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Old Mar 22, 2014, 09:17 PM
Proto morlock
Australia, QLD, Brisbane
Joined Mar 2008
180 Posts
I'd like to, and it might be doable for a larger version, but for this one it's going on the belly per the plans.

To be stable, a rocket needs the c of g to be a long way in front of the aerodynamic centre, i.e. nose heavy. If you put the rocket in the tail, as the propellant burns the plane would get progressively more nose heavy, meaning the glide phase would be ... interesting.
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Old Mar 22, 2014, 09:54 PM
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Canada
Joined Nov 2000
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You are aware that the ONLY 'flight' of a Natter... killed the pilot.
Plans aside, it never achieved aircraft status.
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Old Mar 22, 2014, 10:20 PM
Proto morlock
Australia, QLD, Brisbane
Joined Mar 2008
180 Posts
The only powered manned flight, yes, though there were a few test glides launched from a He111 (hmm, that's an idea...)

In fact, given the boost phase was meant to be automated and a large part of the airframe was disposable, I'd argue that the concept was more manned surface to air missile than aircraft, which made the whole thing a bit of a dead end.
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Old Mar 23, 2014, 05:31 AM
Ad eos qui nesciunt crepitus
Old_Pilot's Avatar
United States, TN, Memphis
Joined Dec 2012
1,304 Posts
Rockets and Balsa

Jim,

It would never have done for you and I to have grown up together. We would have burned up the sky, not to mention several neighbor's back yards. I affixed Estes rocket engines to clipped wing toss gliders, cardboard tubes, Tonka trucks.....you name it, I put a rocket on it. Even thought of trying to make a rocket squirrel (Rocky and Bullwinkle), but the little buggers wouldn't hold still long enough......LOL

I can't wait to see this one fly.....wonder if it would take a D or E series motor ? (Evil smile)

I'd bet my Bristol 138 could act as the mother ship ( 66" of wing with a current wing loading of ~ 8.4 oz /ft2).....that'd be cool !
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Old Apr 24, 2014, 06:20 PM
Proto morlock
Australia, QLD, Brisbane
Joined Mar 2008
180 Posts
Ah, fond memories of childhood pyrotechnics. I don't know if it makes me a bad person, but I laughed picturing an estes powered squirrel...

I've sheeted the wing and framed up the fuse. For some reason I seem unable to build straight at the moment, but I think I saved it in the sanding.

One problems is that all the motors in my stash have ejection charges, being originally bought for rockets. The motor tube is paper wrapped in carbon tow and plugged with a half inch of cork epoxied in so hopefully the motors will self eject, but it still could all end in a bang...
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Old Apr 24, 2014, 07:30 PM
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United States, TX
Joined Jun 2011
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You can still have an ejection charge if you provide for a fireproof route for the ejection gasses to escape, like maybe an aluminum tube?
Looks very light. Do you think it'll be okay for the rigors of rocket power?

I built a rocket powered plane I called the Kestrel, and man did I over-design it! LOL.
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Old Apr 25, 2014, 06:25 AM
Proto morlock
Australia, QLD, Brisbane
Joined Mar 2008
180 Posts
How did the Kestrel fly?

The idea of the tow wrapped tube is that the ejection charge blows the motor out. When I was younger, I made a couple of rocket planes that did the same. On one the motor mount was a thick cardboard tube, and the other had a solid balsa fuse with an appropriately sized hole bored out. Hopefully this version will do the same with a bit less weight.

Skinning the fuselage is next, which should help the strength. I'm more worried about the motor trough, and the estes efflux burning the tail off...
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Old Apr 25, 2014, 10:35 AM
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United States, TX
Joined Jun 2011
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Jim, I haven't yet even maidened the Kestrel.
Our half-gale force winds on a daily basis 80% of the year where I live are not conducive to ANY type of glider. I am going to have to maiden her in another part of the country.

I wrapped my tail in reflective automotive tape that is used to wrap around wiring harnesses so that they don't melt in close proximity to exhaust headers. I bought a roll of that stuff, and it is aluminized on one side, with fiberglass insulation and is adhesive on the other side. Works really well. I should have gone with a twin-boom tail, probably with a V or T-tail, but because I didn't, I used that reflective heat tape.

Let's see if I can find a picture for you...
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Old Jul 08, 2014, 06:39 PM
Proto morlock
Australia, QLD, Brisbane
Joined Mar 2008
180 Posts
Hmm, it has been a while since the last update. Progress since then

- tow hook installed
- radio gear installed
- fuselage sheeted
- airframe assembled, filled and tissue papered
- wing tips and nose added from pink f**m

I've been reluctant to post because sheeting the fuselage was a bit of a disaster. I used 1mm balsa, planked the bottom half and sheeted the top, then ended up in an endless loop of filling, sanding, sanding through, filling...

It's ended up presentable, but heavy : (

Still to do:
- line trough
- canopy
- paint
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Old Jul 08, 2014, 08:45 PM
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Canada, ON, Lindsay
Joined Nov 2013
166 Posts
Quote:
Originally Posted by Jim_the_Sane View Post
Hmm, it has been a while since the last update. Progress since then

- tow hook installed
- radio gear installed
- fuselage sheeted
- airframe assembled, filled and tissue papered
- wing tips and nose added from pink f**m

I've been reluctant to post because sheeting the fuselage was a bit of a disaster. I used 1mm balsa, planked the bottom half and sheeted the top, then ended up in an endless loop of filling, sanding, sanding through, filling...

It's ended up presentable, but heavy : (

Still to do:
- line trough
- canopy
- paint
As my father once said, if you've never screwed up you havn't done much. Besides, it looks pretty good. Nice work .

And also if it ends up being heavy...put a bigger rocket on......
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Old Jul 10, 2014, 11:21 AM
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United States, TX
Joined Jun 2011
2,976 Posts
Boy that's going to be a bullet! It's going to fly fast, unless it's a real light weight.
Good luck!
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Old Jul 11, 2014, 04:23 PM
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United States, TX
Joined Jun 2011
2,976 Posts
You know what would be a good alternative to EDF?
Jetex.

Yeah why not? I know they're not making them anymore, but I have seen Jetex motors and fuel pellets available on Ebay for not too outrageous a price.
Can you imagine how much fun some of those old Jetex planes would be to fly with today's micro-RC?

In fact, Jetex would be a good way to fly this plane too. (Or winged rocket, as it may be).
It would be lighter, less complex...seems like a win-win.
I might have to consider that myself one of these days.
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Old Jul 18, 2014, 04:57 AM
Ad eos qui nesciunt crepitus
Old_Pilot's Avatar
United States, TN, Memphis
Joined Dec 2012
1,304 Posts
WOW.....a bullet with wings ! I can't wait to see this one fly..or would that be " streak". Nice work

Suggested nose art.....
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