Marking out aids.

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Well-Known Member
Jul 15, 2014
North Carolina
I'm working on a mockpit when I have some spare time. I got the last of my important bulkheads lofted today, and then wanted to transfer to cheap ply. I managed to loft everything with straight lines and circular arcs. That will make alterations and flat wrapping far easier to calculate when I get to that point.

For marking out large circles, I've often used the string and pencil technique. Anyone who has done this knows how tedious it is to get the string the right length. I want my mockup to be fairly accurate, so 'about right' wasn't good enough. I also have a LOT of arcs to draw, so tedium wasn't appealling, either.

One tool I've made before is my 'radius stick' Tonight's iteration is a paint stirrer with 1/16 holes drilled in it at my various small radii. But tool of the week is my adjustable steel compass string. I don't know why I've not made one before. It was not hard and works great. It is a scrap of ply, a 1/16 hole in one end to take a push pin. A second piece of ply is screwed to it which clamps a length of 24ga wire with a loop on the end. To use it, a push pin goes into the origin through the 1/16 hole in the ply. I pre-push the hole in the ply as it's hard to see where it is going otherwise. The screws are adjusted to give 'about right' sliding tension on the wire after setting it short and the wire is pulled out through the clamp until the push pin I am using to pull it lines up with my desired radius mark. I then fully tighten the clamp screws and draw my arc with an automatic pencil. No doubt there's a fancy commercial version of this, but it was probably faster to make than it would have been to find online...

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Well-Known Member
Log Member
Jan 30, 2011
Las Cruces, NM
My favorite (quick and cheap) layout tools...

The compass is good for a max radius of about 30". I made to layout wing roundels but it comes in handy for all sorts of stuff. If I'd know how much I was going to use it I'd have taken a little more care in making it. The thing in the middle is great for transferring the frame outline to the outside of the ply (ply on stick construction).