OK, let's a have a got at those control fins.
As you can see in a photo, the fins (which rotate to provide directional control of the missile) have smooth bulges at the bottom center where it sits on the actuator fairing:
I was determined to recreate this; I have no precise specification of the curve, but I wanted it to at least look roughly correct. What follows is my third attempted technique (my pile of discards grows ever larger; I'll devote a post to it at the end of the build).
First up: cut lots of pieces. The primary fin cores are 1/16" basswood, while the rest is 1/16" balsa:
The basswood cores were coated with TBII to provide a bit of a sanding barrier.
Two balsa pieces are stacked on top of the fin to create the contour. I did one side at a time, to avoid excessive handling of the balsa on the other side from where I was working.
Next comes sanding. Lots of *careful* sanding. The two stacked pieces gave me a visual guide of what I was doing, rather than completely freeform sanding of a thicker piece (something I did on an earlier technique test, and I wasn't happy with the results). I roughed it out with 220 (not too aggressive, didn't want to oversand) and then worked the final shape with 440. Each side of each fin took several minutes of sanding until I was satisfied. Here's the first one, viewed from the bottom so you can see the shape I was going for:
After I finished each round of sanding, I coated with TBII, again for protection.
A big question was whether this was repeatable. Could I make four fins on two sides each, and achieve consistent results? I would say the answer is "mostly". Here's the completed set; you can see the the base curves are not perfectly symmetrical but pretty good. I don't think you'll be able to notice the difference in the final model. The one on the left is not as pointy as it looks in the picture, couldn't figure out why it looks that way here.
Thinned CWF was applied to everything and sanded down. Then, I decided that these were the one part on this rocket that I would apply filler-primer to (since these were the only components that were completely constructed off the rocket). After spraying, I could better see how the contours looked:
I would say: pretty great, that's exactly what I was hoping for. Which is a relief given how much work they were. Finally I sanded off the filler/primer, a task which I fairly loathe, and here is the finished set:
Whew. Gluing them on should be routine..... mostly. That'll be next.
As you can see in a photo, the fins (which rotate to provide directional control of the missile) have smooth bulges at the bottom center where it sits on the actuator fairing:
I was determined to recreate this; I have no precise specification of the curve, but I wanted it to at least look roughly correct. What follows is my third attempted technique (my pile of discards grows ever larger; I'll devote a post to it at the end of the build).
First up: cut lots of pieces. The primary fin cores are 1/16" basswood, while the rest is 1/16" balsa:
The basswood cores were coated with TBII to provide a bit of a sanding barrier.
Two balsa pieces are stacked on top of the fin to create the contour. I did one side at a time, to avoid excessive handling of the balsa on the other side from where I was working.
Next comes sanding. Lots of *careful* sanding. The two stacked pieces gave me a visual guide of what I was doing, rather than completely freeform sanding of a thicker piece (something I did on an earlier technique test, and I wasn't happy with the results). I roughed it out with 220 (not too aggressive, didn't want to oversand) and then worked the final shape with 440. Each side of each fin took several minutes of sanding until I was satisfied. Here's the first one, viewed from the bottom so you can see the shape I was going for:
After I finished each round of sanding, I coated with TBII, again for protection.
A big question was whether this was repeatable. Could I make four fins on two sides each, and achieve consistent results? I would say the answer is "mostly". Here's the completed set; you can see the the base curves are not perfectly symmetrical but pretty good. I don't think you'll be able to notice the difference in the final model. The one on the left is not as pointy as it looks in the picture, couldn't figure out why it looks that way here.
Thinned CWF was applied to everything and sanded down. Then, I decided that these were the one part on this rocket that I would apply filler-primer to (since these were the only components that were completely constructed off the rocket). After spraying, I could better see how the contours looked:
I would say: pretty great, that's exactly what I was hoping for. Which is a relief given how much work they were. Finally I sanded off the filler/primer, a task which I fairly loathe, and here is the finished set:
Whew. Gluing them on should be routine..... mostly. That'll be next.
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