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Lockheed Twins Model 14 and 18


rob Lyttle

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The KLM picture on Airliners.net is a good one. 

There's a visual "thing" going on, and the t. e. doesn't line up with a ruler as dead straight. But the Tailplanes taper towards the tips and the elevator must get thinner too. 

So, is that creating an illusion? 

 

On the other hand, if the slope of the aerofoil section remains constant across the whole elevator end to end, but it is thicker in the centre, then THAT would automatically create a slight V angle along the t. e. of the elevator. 

Which means the MPM /Revell piece in the picture above would be correct. 

 

I'm surrounded by styrene shavings as I write.... 

Edited by rob Lyttle
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I've seen all the surviving RAAF ones, which ended up with Adastra (which is where I saw them, way back when at Mascot). The elevator/horizontal stabiliser line was straight on all of them.

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Think it through. Either the elevator is split with a variable gap in the middle when it is deflected (and some potentially interesting aerodynamics), or it has to have a straight hinge - otherwise it can't move.

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50 minutes ago, Admiral Puff said:

The elevator/horizontal stabiliser line was straight on all of them.

 

12 minutes ago, Lazy8 said:

or it has to have a straight hinge - otherwise it can't move.

Check and check, guys. 

 

The hinge line has to be straight, and I've straightened the odd Airfix one... 

But the trailing edge of the elevator... 

 

Does the slightly thicker section in the middle (the planes tapering towards the tips)... Does that produce a longer projection rearward to the trailing edge, given that the surfaces come together at a constant angle? 

@Admiral Puff are you saying the t. e. line is dead straight, or the hinge line?

 

Here's what I've done, 

IMG_20190318_215148

 

and it pretty much tallies with the MPM piece in the background. 

But it's shaveable 👍

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Yes, there is a slight taper on the trailing edge - the centre chord is slightly larger than the outboard. There's not much in it - the deviation from square to the fore and aft line is only a degree or so - but it's there.

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Good one @Admiral Puff. Thanks for that!

So what I've done is probably a bit exaggerated, but I'm on the right track? 

Comparing with the MPM moulding, their shape is probably about spot on and mine needs easing a fraction. 

 

When I started into the little Airfix kit, for a quickie, I didn't even know there was a question, never mind what the answer is!! 

Thanks for the insight 

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7 hours ago, JWM said:

That is the first photo I have seen which clearly shows how part of the aft fuselage fairing is attached to the elevator! Thanks for posting.

Edited by Space Ranger
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4 minutes ago, Space Ranger said:

That is the first photo I have seen which clearly shows how part of the aft fuselage fairing is attached to the elevator! Thanks for posting.

I totally missed that, I don't look to good. Also the trim tabs work opposite of the elevator. I guess they "fly" the elevator. Always wondered how TCA personnel kept their white coveralls clean.

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1 hour ago, busnproplinerfan said:

Also the trim tabs work opposite of the elevator. I guess they "fly" the elevator.

That's exactly right. Per Wikipedia:

 

"When a servo tab is employed, it is moved into the slipstream opposite to the control surface's desired deflection. For example, in order to trim an elevator to hold the nose down, the elevator's trim tab will actually rise up into the slipstream. The increased pressure on top of the trim tab surface caused by raising it will then deflect the entire elevator slab down slightly, causing the tail to rise and the aircraft's nose to move down."

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29 minutes ago, Space Ranger said:

That's exactly right. Per Wikipedia:

 

"When a servo tab is employed, it is moved into the slipstream opposite to the control surface's desired deflection. For example, in order to trim an elevator to hold the nose down, the elevator's trim tab will actually rise up into the slipstream. The increased pressure on top of the trim tab surface caused by raising it will then deflect the entire elevator slab down slightly, causing the tail to rise and the aircraft's nose to move down."

Thanks, I think it makes he load on the controls lighter.

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I'd already come across this type of design when building a Beech 18, (Expeditor), 

Beech used a similar thing where the rudders intersect Tailplane, in addition to the elevator fairing. 

Clever and stylish. 

Who was first, Lockheed or Beech? 

Edited by rob Lyttle
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  • 2 weeks later...
On 23/03/2019 at 19:08, Space Ranger said:

That is the first photo I have seen which clearly shows how part of the aft fuselage fairing is attached to the elevator! Thanks for posting.

These are tucked away in the BM walkaround section, under "Hudson". 

30.jpg

 

31.jpg

 

The intro acknowledges that the airframe is an Adastra civilian L14 dressed up as a Hudson - hence the correct elevator for this issue. 

 

Some great information refs on the fowler flaps too, which are a bit of a feature on these planes. 

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36 minutes ago, Space Ranger said:

walkarounds.

I know! 

I think the section needs to be pushed more to the front of the forum. 

It's very "tucked away" and easily overlooked. 

There's a load of great stuff on there, and it's OK to paste anything in there onto your build thread or whatever. P

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