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Jul 28, 2021, 01:10 PM
Corsair Monty
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UC-78 Bamboo Bomber build


I'm going to build a UC-78, the old Sky King plane. The plan has a 68" wing span and I am upscaling it to 85" wingspan. The old plan calls for 2 K&B .35 glow engines, these plans are from the 1970's. I want to build this for electric. Has anybody ever built this plane? I know that a lot of information is needed in order to size the motors correctly, but I'm wondering if electric is a practical way to go. Any ideas?
Thanks, Monty
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Jul 29, 2021, 10:41 AM
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E-Challenged's Avatar
There is a short kit for a smaller Pat Tritle "Bamboo Bomber" sold by Manzano Laser Works. For your 85" version, I would contact Lucien Miller , Innov8tive Designs, by phone, for recommendations on a pair of Cobra motors, speed controls, props and battery pack. Be ready to provide estimates for wing area, prop clearance, total weight of airframe less motor and batteries and desired performance. You can go to his website and peruse motors and prop charts to get a general idea of what you need.
Jul 29, 2021, 03:34 PM
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Zipman's Avatar
Monty, The old RCM UC78 plans from the 1964 issue is 1/8th scale at around 64inches span.
Designer Don Smith has a plan in 1/5th scale at just over 100 inches.
You are looking to build one at 1/6th scale, 84-85 inches. Here are a couple build links for the above sizes to give you an idea what you can expect building this model. Don't know your building skill level so these build logs will help you determine what you want to take on based on size and expense.

I am currently building(slowly) the RCM 64in model. If you enlarge these plans you need to consider the construction upgrade needed going from a 64in twin (RTF weight - 8 lbs) to a 85in twin (EST wt - 15 plus lbs). Many parts of the enlarged model will need to be re-engineered to handle the flight loads and larger motors and batteries. Going electric vs glow, 4 cyc or gas motors should allow lighter construction and only minor changes in wood components from the 64in plans.
As far as the power system is concerned, you will have help here from the Electric flyers here but, you will need to provide certain model specs for them to help select the proper motor and prop combos. A good way to see what power works is to look at other twin models in the size you are building and see what power equipment is being used. This forum is a good place to start as well as looking up kits and ARFs in your model size.
Here are the links.

RCM 1/8 UC78 plans build E-powered
https://www.rcgroups.com/forums/show...78-T-50-Bobcat

Don Smith 1/5 scale Cessna t-50 plans build
https://www.rcuniverse.com/forum/gia...na-t-50-a.html

Sweet Caroline (Cessna JRC-1 Bobcat) DS 100 in E-powered
https://www.rcgroups.com/forums/show...9#post18273604

There are laser cut kits available for the 64in and 100 in models as well as some smaller scale Bobcats.
Good Luck
Stan
Aug 03, 2021, 12:10 PM
Corsair Monty
Thread OP

Uc-78


Thanks you guys for the information. I will continue to do my home work before I start the build. I hate to do things twice when it could have been avoided ih the first place.................measure twice, cut once!


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