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Building Tips and technical articles. => 1/2 A building. => Topic started by: Ed Carlaw on February 23, 2021, 10:46:30 AM
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I am in the finishing stages of a Brodak Baby Ringmaster. I haven't decided yet whether to use a Baby Bee or Golden Bee. I'm thinking that will depend on the run times between the 5cc and 8cc tanks. Anyone know the approximate run times for these tanks? Thanks,Ed.
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Remember the Baby Bee tank is shorter than the Golden Bee and will change the C/G
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Hi Bob, the CG I can adjust. My concern would be the duration of the flight if I should get a relative newcomer on the handle. I know I could adjust the amount when I fuel up. I was just curious about run times between the two tanks. Thanks, Ed.
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the Baby Bee tank is plenty long enough for a newbee
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If you fuel from a syringe, you can short-tank the bigger tank AND take advantage of the forward shift in CG towards more stable. Then swing back to the Babe Bee for a truly shorter tank/duration.
The real trick would be to get the CG right for the short tank, and flip the plane to keep the same CG with a bigger tank. That could be as simple as a spacer with the Babe Bee, and no spacer for the GB/BW with longer tank.
In the end, I'd recommend filling from a syringe where you can observe just how much was put in the tank short or full regardless of which engine/tank.
Enjoy the build...enjoy the flights!
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Both are old school engines, one from the early seventies and the other a little bit newer. I'm going to try a 6-3 wood prop if I can find them. I've always been a little leery of the older plastic props. Had a couple if incidents with them. Ed.
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Ed,
You can get new plastic props in different sizes. One source is Windsor Propeller's Master Airscrew GF series.
https://www.masterairscrew.com/collections/gf-series
Dave
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Both Bernie and Matt have appropriate propellers
https://coxengines.ca/
http://www.exmodelengines.com/
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6x3 wood is okay. A 5x3 prop will make the reed valve engines happier. I have two Baby Ringmasters that I fly with the yellow 5x3 "rubber ducky" safety tip props that I get from Bernie (https://coxengines.ca/cox-.049-propeller-5-x-3-safety-tip-yellow.html) or Matt (http://www.exmodelengines.com/product.php?productid=18361&cat=257&page=1). They don't break like a wood prop if you biff the plane, and they spin up well on the reedies. I like the yellow because it makes a nice, visible prop arc so I (and any beginners) can see where not to put my fingers.
Like Motorman says, just use the Golden Bee. You can short tank it if need be. Assuming both engines are stock, they're both single bypass engines and will make about the same power, even though the Golden Bee has a slightly larger venturi tube. In reality, old Cox reed engines have so much run history, that fuel burn and power output vary from one engine to another. So what I get for run time on my Golden Bee might be a half minute or more different from what you get. Because of this, I don't really pay much attention to specific run numbers on my Bees. I just take one, clean it up, and put it on a plane. I know I like the performance of a 5x3 on a plane like the BRM over a 6x3. Per the Feb. '59 American Modeler review, the Golden Bee will get 13,000 RPM on a Cox 6x3 prop, and 16,800 on a Cox 5x3 prop. YMMV
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I used to try to short tank but any more I just let some fuel run off before releasing the plane. Also I exclusively use the stunt tanks because of how the fill tube and vent work. That being said, any style tank will work. Just fill it up, fire it up, and enjoy.
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Thanks for all of the help. Ed.
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just a question does run time vary if you add nitro ?
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Hey Walt, maybe next month HB~>
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When we flew PT19s for training, I took a hand lotion bottle and made a fueler out of it. Two pumps was just right for a training flight. The bottle proved to be quite fuelproof. Easy to epoxy a brass tube into the output nozzle and that was all it took. 🤪