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Is my Goldberg Cub too heavy?

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Old 01-01-2019, 11:44 PM
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jdporker
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Default Is my Goldberg Cub too heavy?

Just completed construction of a Carl Goldberg Anniversary Cub. The empty airframe weight is 5.5 lbs. WITHOUT RADIO and ENGINE. The radio (receiver and six servos) and Saito .80 FS will probably add another 2 to 2-1/2 lbs. bringing its total weight to 7-1/2 to 8 lbs. Does anyone know if this is typical for a Goldberg Cub? If any members have built or are flying Goldberg Cubs, could you please advise me of their ready-to-fly weights? Is 8 lbs. too heavy? I covered the airplane with Super Coverite and sprayed it yellow. It seems heavy, so, Im wondering if I should just hang it up and start over. Would greatly appreciate any feedback you can provide. Many thanks.
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Old 01-02-2019, 06:21 AM
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scale only 4 me
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Is 8 lbs. too heavy
Nope,, these fly anywhere from 12-14lbs with floats on them,, 8lbs is nothing
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Old 01-02-2019, 06:25 AM
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Yes it is heavy.

Too heavy to fly no.

But be careful not to slow it up or to make tight turns unless you are high enough to recover from a snap roll.
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Old 01-02-2019, 06:45 AM
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At 8 pounds you're running 25 ounces per Square foot wing loading. Which is probably the sweet spot for wing loading on this model. Neither too heavy nor too light.

At 10 pounds you would be just over 30 ounces per square foot wing loading. Still well within the range this model can handle though you should start to notice the extra weight in the flight characteristics. i.e. it will feel more solid and need to land a bit faster. But not exceptionally so.

An 80 four stroke is going to be more power than necessary. It will probably do everything you need right now at half power.

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Old 01-02-2019, 08:45 AM
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Built according to the plans, this Cub will fly well with your setup. Mine was set up in a similar fashion, and was over powered.
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Old 01-02-2019, 04:06 PM
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Tom Crump - Thank you for your feedback. Much appreciated. Paul
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Old 01-02-2019, 04:07 PM
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Appowner, Many thanks for your advice. Much appreciated. Paul
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Old 01-02-2019, 04:09 PM
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j. duncker, Thank you for responding. I appreciate your comments. I'll fly two mistakes high. Paul
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Old 01-02-2019, 04:11 PM
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scale only 4 me, Thank you. 12-14lbs. -- WOW! Thanks for making me feel better. Greatly appreciated. Paul
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Old 01-02-2019, 04:19 PM
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I used to fly mine with an OS .40 two stroke with bushing and it flew fine. If you never had a Cub before, remember to use rudder for turns or you will be learning about adverse yaw too late

Have fun

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Old 01-02-2019, 04:26 PM
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Thanks you all very much for responding. Here are some pictures...

Flaps and ailerons.


Front view with slightly beefed-up cabin area. Cowl cutout for Saito four stroke .80


Friend made custom landing gear with toe-in.


Another view.


Servo tray and wing saddle area. Nylon bolts used for wing hold down. Unlike metal screws, the nylon bolts will snap and absorb much of the impact of a crash like a ground loop.


No decals or markings yet -- did not want to waste the time if the Cub was too heavy.
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Old 01-02-2019, 04:27 PM
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Thank you. WILL DO!
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