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Jun 13, 2015, 12:56 PM
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Build Log

BBCC-7 Bristol Beaufighter 28" FF->RC 36"


This is a 28" rubber FF to electric power RC. I will scale up to 36"

Submitted for consideration BBCC6 - link here

Rolled over to BBCC-7 here

Plan is on Outerzone

I've never built a flying model of a Beaufighter, but I did build a solid balsa model from a kit, decades ago. This was before plastic kits became popular - my friends and I despised those; we felt vastly superior having made our own from scratch. We rode to school in the city bus, and held our planes out the window (not legally!) to watch the hand made props spin, and feel the effect of wind on a plane. Cheap thrills!

My intent is to have counter rotating props and no rudder. I plan to use differential thrust to get yaw via the rudder channel. Learning experience for me, although well known for many.

I think I'll build a profile model from 1/4" balsa to set up the electronic wizardry, then transfer everything learned to the built up model.
Last edited by victapilot; Nov 22, 2015 at 08:50 AM.
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Jun 13, 2015, 12:57 PM
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Aug 06, 2015, 08:28 AM
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Maiden


Maiden was not good. I tried underhand launch, it stalled and rolled left into the ground.

I have 10g lead on the port wing to balance the battery pack on the starboard side of the fuselage. It seemed balanced laterally with that, but I'll cut it back to 5g. Lots of power, I was expecting it to climb out, but no such luck.

It is already fixed. Glad it wasn't a built up model, it would be totaled

I'm looking forward to at least one high speed pass with it - it sounds awesome!

Beaufighter Maiden (0 min 23 sec)
Aug 08, 2015, 04:45 PM
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Wheels


The problem with hand launch is that it must get above stall speed to fly, and that would take an athletic toss. Maybe with wheels, I can get above stall speed and ROG.

Here's a first taxi test. Seems the wheels, which are close to scale size are a bit small for our runways at present. Also I have too much rudder to motor mix. To be continued

Beaufighter Wheels (1 min 13 sec)
Aug 09, 2015, 07:56 AM
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Hey VP,

I have that plan in my digital stash as a "one of these days" build; it's going to be fun watching you do yours.

What are you using for motors and props? Your battery seems a little bulky for the size of the model; maybe you could sub in a lighter one for your test flights?

Steve
Aug 09, 2015, 09:40 AM
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Originally Posted by Steve85
Hey VP,

I have that plan in my digital stash as a "one of these days" build; it's going to be fun watching you do yours.

What are you using for motors and props? Your battery seems a little bulky for the size of the model; maybe you could sub in a lighter one for your test flights?

Steve
Hi Steve

The motors are Funfighter type with 5.5x4.5 APC props, one tractor, one pusher running in reverse to give counter-rotation. 30A Blue HK ESCs. I have several of these in Funfighter foamies, and with that setup they pull about 20A on 3s each. They can also tolerate 4s.

You are right about the battery, it's 1600mah 3s. I could try a high C battery about half that, and get several minutes flight. I have been thinking of two 2s in series, one on each side of the fuse. That would eliminate the lead on the port wing tip, but would be scary powerful until I get the setup figured out.
Last edited by victapilot; Aug 09, 2015 at 12:54 PM.
Aug 09, 2015, 02:56 PM
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More taxi


Using 2 1/2" wheels, rolling much better on our coarse grass. Also with 850mah 45C 3S lipo, saves 2oz. The speed shown is about 1/2 throttle, the plane left the ground for a few yards.

Mixing rudder to throttle is reduced to 15%, that seems plenty for ground control

Beaufighter Taxi 2 (1 min 34 sec)
Aug 10, 2015, 06:25 PM
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Quote:
Originally Posted by victapilot
5.5x4.5 APC props, one tractor, one pusher running in reverse to give counter-rotation.
Hmmm. I wonder if they're both producing the same rpm/thrust? Depending on how the airfoil on the two props is set up (pusher vs. puller), could there be asymetric thrust? Would that explain the pull to the left on take-off? Then again, it seems to track straight on the ground...

Steve
Last edited by Steve85; Aug 10, 2015 at 06:32 PM.
Aug 10, 2015, 07:38 PM
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Quote:
Originally Posted by Steve85
Hmmm. I wonder if they're both producing the same rpm/thrust? Depending on how the airfoil on the two props is set up (pusher vs. puller), could there be asymetric thrust? Would that explain the pull to the left on take-off? Then again, it seems to track straight on the ground...

Steve
I think they are quite close, based on powering up while hand held.

The setup is as follows:

Starboard motor with tractor prop connected to throttle channel
Port motor with pusher prop turning reverse connected to gear channel
Throttle channel mixed 100% linear to gear channel
I could change the mixing % if there was asymmetric thrust.

Also

Rudder channel mixed 15% to throttle channel so left rudder increases thrust on that side and vice versa.
Rudder channel mixed -15% to gear channel so left rudder decreases thrust on that side and vice versa

That is trimmable as necessary.

So I have control to compensate, hopefully

The problem with the underhand launch was too little speed. The plane weighs 15oz without battery, and I was using the big battery. Probably 25oz per sq ft, maybe more. I did leave the ground and stay straight and level in one of my taxi tests, so I'll give it another try soon, weather permitting.
Aug 11, 2015, 05:10 PM
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Sounds like you've got it covered! Good luck on the re-maiden!

Steve
May 08, 2016, 03:57 PM
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Cutting balsa


Time to get started on the build.

So far, I have transferred the motors and speed controls to an old beat-up Formosa. It is in the pic below. It flies nicely on 4s, weighs 30oz without the battery. The motors and 30A ESC's are heavy but generate plenty of speed. I need to build light but strong, landings might be a bit hot and if the plane is not strong enough, that will be the end

Ribs shown are as plan but cut short because of wide trailing edge / ailerons. The plan shows rubber motors running at an angle thru the wing into the fuselage. Very creative, but I don't have to go with the designed spar and half ribs so will add some extra 1/16" ribs
May 08, 2016, 06:30 PM
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Re-subscribed!

Steve
May 10, 2016, 06:50 AM
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Wing


Wing is polyhedral. I will build it flat, then cut and set.

Main spar is 1/8" square spruce top and bottom. I'll web with 1/32". Trailing edge and ailerons 1/4x1" will need to be built up to fit. Leading edge will be partly sheeted
Last edited by victapilot; May 20, 2016 at 07:14 PM.
May 26, 2016, 07:39 AM
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Fuselage


I will build the fuselage onto the wing, while having the wing removable for electronics installation and battery change.


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