What do these Lines Mean

[bjk896]

Way back in 2014 a bloke called Electriflier outlined his 98" depron C130 Hercules build on these pages.

This past year I decided to come back to modelling and a Herc was high on my list. It is actually happening and in  depron at 48/63 inches.

 

I use Electriflier's journal as an illuminating guide to my activities as he often explained why things were done in the depron context and had a beaut way of talking thru his activity.

 

However, when it came to wing ribs, he showed something that didn't get an explanation and I couldn't reason one out.

In his picture, attached and taken from his story, there is a dotted line which is roughly in the middle of  each rib. It also shows the 6mm strip to be cut out and  removed from the rib so they  can be glued to fit on either side of the wing.

What has me whacked, is what are these dotted lines for. Any ideas, help or explanations please??

 

 

bjk896

 

 

[Cuban8]

Can't see very well from the photo but it looks like the rib profiles do not have a flat underside as you get with say a Clark Y, so no easy way to correctly align them on your building board to take account of the varying sizes and taper.

The dotted line gives the datum point from which the aerofoil is plotted and hence a jigging reference for correct alignment and washout (if any).

Not sure about the 6mm strip -another alignment aid perhaps.  Another picture ?

 

Edited December 29, 2021 by Cuban8

[Don Fry]

Think he means there is a 6mm strip cut out, so each half can be glued to a 6 mm central wing plate plate. The wing plate would be clamped to give flat, or washout as needed.

And as you say, the dotted lines are datum marks.

[Gary Binnie]

The dotted line is the Mean Chord Line or MCL. Taken from the centre of the leading edge to the centre of the trailing edge.

 

Wikimedia Commons image.