The Rocket Formerly Known as Black
Fin Location Marking Jig
Compared to marking the fin slots on a regular tube-shaped rocket, marking the slots on a cigar-shaped rocket is a nightmare. I've had a lot of time to think about how to do this since the last one I made, and this solution worked well -- although the rig I came up with was a horrific contraption that would have made Rube Goldberg shudder.
I saved the used Masonite scrap from the construction of the Cutting Fixture and reinforced the backside with angled aluminum to make it rigid. This created a negative outline of the airframe and gave me an edge to trace against. I clamped this rig to a framer's square so it would stand perpendicular to the work surface and stood next to the fuselage.
I also made an alignment guide to assure that the marking jig was properly aligned. The circle at the the top (circle x) is to align the fuselage (it is centered in this circle) aligned to the fin markings on the aft ring of the fuselage (the forward and aft rings were marked after installation). The perpendicular blue line (line y) is to align the marking jig. The green line (line z) is for a second check. I stood a framer's square on this line and marked a point midway up the fuselage, so I had aligning points forward, aft, and center.
The light purple line is not part of the alignment guide, but shows the outside diameter of the the airframe as it stands on the template.
Once all the components were aligned and the marking jig was perfectly perpendicular to the fuselage, I traced a line along the jig onto the airframe, then rotated and repeated the process.
Notice how nice and smooth the shaped foam looks after the hand sanding is complete.
TRFKAB Index
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