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  #71  
Old 04-22-2018, 08:03 PM
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neil_w neil_w is offline
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Default Finishing the wings

All four wings are on. The last two were a bit of an adventure, requiring a lot of careful sanding to get the root edges to sit flush on the body. During lamination they must have picked up a bit of a curve; I had certainly checked that the wood cores were square before lamination.

I also found I wasn't really able to do anything about the warp on the fins (also no doubt a side-effect of lamination). I don't think anyone will notice, although you can definitely see it if you sight down directly from the front or back.

I added some CWF to the spots in front and back where the skirt tapers back to join the core (that's a gap in the cardstock). Seemed to come out OK on most, although I might hit one or two spots with another round of CWF. Like many areas at this point, it's tough sanding in there. [picture 1]

Picture 2 shows the finished assembly. Note the slight waviness to the seam between the cardstock and the body on the fin nearest the viewer. Tried my best to avoid that but only so much I could do. I don't think it'll be too noticeable once everything is flat grey.

Overall I'd call the whole wing construction technique a success. Everything fit together well, and it has the profile I was looking for (which is to say, the profile of the IRIS-T wings.) We'll see how it looks when the model is painted.

Next up are the control fins, where have been another adventure (this build is full of them. )
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  #72  
Old Yesterday, 08:37 PM
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neil_w neil_w is offline
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Default Control fin construction

Lets build those control fins. Small parts, large effort.

As shown in picture 1, each control fin has a bulge at the bottom where they mount to the actuator fairings. I was determined to capture that in the model, even though it wouldn't be practical to reproduce the geometry precisely.

Picture 2 shows all parts cut and ready to go. The fin cores at the bottom are 1/16" basswood (subsequently coated with TBII to provide a sanding barrier) while the contour pieces are 1/16" balsa.

Picture 3 shows the balsa contour pieces stacked and applied to one side of each fin.

Next comes lots and lots of careful sanding. The contour pieces provided a visual guide of what I was trying to do. Picture 4 shows the result of sanding the first piece.

The big challenge here was trying to create 2 sides each of 4 fins consistently. I think I succeeded pretty well; they're not 100% identical but close enough that you won't see the differences on the finished model. See picture 5.

These were the only components constructed off the rocket, so these are the only ones that will be getting filler/primer on this build. After spraying I could really see what the finished contours looked like, which is to say pretty good. See picture 6.

And finally, picture 7 shows the completed set after sanding off the primer (I really hate that step). I am very happy with the results here. It was a lot of work, and I discarded a lot of experimental pieces until I got exactly what I was after.

Gluing them on should be *mostly* straightforward. That'll be next.
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  #73  
Old Yesterday, 11:44 PM
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blackshire blackshire is offline
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Default

Museum model makers, as G. Harry Stine pointed out in his "Handbook of Model Rocketry," not uncommonly have to work with incomplete scale data (and the IRIS-T's mostly-classified details definitely put it in that category), so your model is probably no less accurate than any museum model of the IRIS-T would be--but yours flies!
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  #74  
Old Today, 07:54 AM
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neil_w neil_w is offline
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Quote:
Originally Posted by blackshire
but yours flies!


We hope.
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