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Old Oct 31, 2006, 04:07 PM
Superhero, Third Class
astroboy's Avatar
Carson City, NV
Joined Nov 2000
888 Posts
Discussion
8-foot B-24 finished

Well, it seems everybody's building one of these, so here's my contribution to the effort. It was scaled up from Eric Clutton's 62" WS plan. I originally was going to build it the same size as glue_sniffer's, with similar power, but somehow I decided that the IPS drives might not be up to the task, so I scaled it up some more and went with GWS 300Cs at 6.6:1. I am using the same GWS 9x7x3s that he is. The pack is 12 CBP 1150s; the motors are wired in two series pairs(inboard and outboard)--2s2p, if you like. The fuselage and nacelles are sheeted; the wing is about 2/3 sheeted. The belly pan is reinforced with fiberglass and extra formers, and the control linkages are concealed. All-up weight is 51.5 ounces; wing loading is about 8 ounces.

Since the model would be somewhat ungainly to hand launch, I built the dolly you see it resting on. Haven't tested it yet; I usually like to use the parking lot where the photos were taken for taxiing tests, but I couldn't get a good range test, so that hasn't happened. I've since (I HOPE) resolved the radio interference issues. Weather permitting, meaning "dead calm", its maiden flight will be at the electric fly-in at Sepulveda Basin this Saturday, the 4th.
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Old Oct 31, 2006, 04:11 PM
OCD: Old, Cranky and Disgusted
challenger_i's Avatar
United States, TX, Sweetwater
Joined Mar 2005
1,612 Posts
Beautiful machine! I envy your abilities! Please, do post videos of the old girl in the air.
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Old Oct 31, 2006, 04:14 PM
Arc, spark and smoke...
desmobob's Avatar
upstate NY; Lake George region
Joined Mar 2006
615 Posts
Beautiful job! Looking forward to seeing some video of her in action!

Good luck with the maiden,
desmobob
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Old Oct 31, 2006, 04:50 PM
Balsa is love....
glue_sniffer's Avatar
Los Gatos, CA
Joined Aug 2004
1,039 Posts
Fantastic!! I'd love to see more building pics if you have them. FWIW I decided to bump mine up to EPS-100 units as many advised me the IPS units would be pretty underpowered. Can't wait to see some inflight pics, best of luck!

-Sky
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Old Oct 31, 2006, 09:01 PM
Registered User
dottney's Avatar
United States, NY, Fairport
Joined Jun 2000
2,600 Posts
Beautiful job! I've been eyeing B-24's all over here and this one provides more inspiratioin. My dad did 30 combat missions with a couple more aborts in 1944-45 and I'd love to do a model of his plane.
Please more building pics and info.
Dave
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Old Nov 01, 2006, 08:14 AM
Registered User
Joined Sep 2005
674 Posts
Beautiful workmanship astroboy!!! Good luck this weekend at the basin-I flew there many years. Please say hi to Tony for me. :-)

Dale Sebring
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Old Nov 01, 2006, 09:58 AM
Light and floaty does it
Work in Progress's Avatar
Cambridge, Great Britain (UK)
Joined Sep 2004
2,859 Posts
That's a fine looking model. I particularly like the transparencies.
Have you put the motors on the tach and ammeter yet? With those big paddle 3 bladers on multi-engine types, it is always a good idea to check the pitch speed which is available on the kind of amperage you are prepared to subject the motors to.
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Old Nov 01, 2006, 03:53 PM
Superhero, Third Class
astroboy's Avatar
Carson City, NV
Joined Nov 2000
888 Posts
Thanks for the kind words, all. As to specifics:

WIP:
Yeah, I had trepidations about the props, too. Static current draw is 10.3 amps, meaning each motor is only drawing a little over 5 amps--so they should be right in their comfort zone. I was hoping for 4000 RPM, and ended up with an average of about 3960. On the other hand, my target weight was 53 ounces, and I beat that by an ounce and a half, so that's not too bad. That RPM translates to a pitch speed-to-stall speed ratio of about 2.3, which should be adequate. According to Dr. Kiwi's, graphs, static thrust-to-weight is about .6, which should be okay, too. Theoretically, then, it should fly.

Dave:
I haven't been too good, especially the last couple of years, at documenting a model's progress, but I think there's a few construction photos I can dig up. I can take a few more to illustrate how certain things were done, so I'll leave additional info until then.

Sky:
That's probably a good move. Good luck with a speedy reconstruction of the fuselage.

Jeff
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Old Nov 01, 2006, 07:34 PM
Turrets Syndrome?
Bomberguy's Avatar
Marina Del Rey California
Joined Dec 2003
1,543 Posts
Looks fantastic Jeff, hope I can make it to the Basin to see it fly.
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Old Nov 03, 2006, 03:32 PM
Superhero, Third Class
astroboy's Avatar
Carson City, NV
Joined Nov 2000
888 Posts
Well, the "few construction photos" turned out to be exactly one. This is how I like to build fuselages for bigger models. I lay out a spine and a keel, all the way around the perimeter, with temp pieces where canopies and whatnot go. Bass sticks are glued lightly (I use Ambroid) to the structure, and then the sticks are glued to the 2x4. It makes a good, stable base, and makes it really easy to work on. I do as much as I can with the fuse attached; in this case, the tail was glued on, the tail control linkages installed, and even some of the sheeting was done before I broke it loose from the sticks.
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Old Nov 03, 2006, 03:38 PM
Superhero, Third Class
astroboy's Avatar
Carson City, NV
Joined Nov 2000
888 Posts
I did take a few after-the-fact shots. This one shows how the wing panels are joined, with two 3/16" carbon fiber tubes, that slide into 7/32" aluminum tubes. It was a little nerve-wracking, as the entire assembly was built separately with the aluminum tubes uncut, then mounted into the wings. I didn't know for sure if the tubes were parallel until I cut the aluminum tubes in half and inserted the carbon fiber tubes. If they hadn't been, there would have been trouble, as the aluminum tubes were already glued into the wings. You can also see the pegs at the leading edges of the wind roots. These pegs, along with two 10-32 nylon bolts near the trailing edges, are what hold the wing down.
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Old Nov 03, 2006, 03:42 PM
Superhero, Third Class
astroboy's Avatar
Carson City, NV
Joined Nov 2000
888 Posts
I'm never sure where the pack is going to end up, so I generally build cages for batteries. Here you can see the rails that the pack can move back and forth on; they're balsa with 1/32 bass caps. After the model is balanced, I made a foam box to prevent the pack from sliding forward, and installed the two dowels into the fuselage top sections, to keep it from moving backward in flight. To the right of the ESC is the slot that receives the right wing peg.
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Old Nov 03, 2006, 03:46 PM
Superhero, Third Class
astroboy's Avatar
Carson City, NV
Joined Nov 2000
888 Posts
A couple of the vacuform plugs: The canopy and the astrodome. I couldn't get a good canopy, as I didn't have a thin enough sheet that was also large enough to cover the largest size my vacuformer can handle, so I had to use the next smaller size, which didn't have enough margin around the edges of the plug to keep it from failing. So I ended it doing it the old-fashioned way, mounting the plug on a stick, clamping that into a vise, and slowly working a sheet of the the plastic around the plug with a heat gun. THAT was a bit of a job, and my fingers were medium rare by the time it was finished.
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Old Nov 03, 2006, 08:47 PM
Lori, hey, you're home early
CarreraGTSCS's Avatar
United States, NJ, Trenton
Joined Jan 2004
9,129 Posts
Wow, nice! If it flies as good as it looks you've got yourself a winner. I'm going to build a similar sized Lancaster so I'll be interested in your flight experience. Good luck.

Mike
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Old Nov 03, 2006, 10:36 PM
Registered User
Boomerang1's Avatar
Sydney Australia
Joined Mar 2005
917 Posts
Hi Astroboy, having undertaken a large project like this myself, including vac forming, I can understand the amount of work involved, well done! - John
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