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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 04-24-2018, 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 04-24-2018, 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 04-25-2018, 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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  #75  
Old 04-26-2018, 06:28 AM
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blackshire blackshire is offline
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Quote:
Originally Posted by neil_w
We hope.
Unless its first launch suffers a huge CATO, it *will* come down, even if it proves unstable--the only question is, "from how high up?" With enough forward ballast it should, like other scale, semi-scale, and scale-like models of rear fins & strake-wings-equipped missiles, fly just fine. I still think it would make (especially if built in a somewhat larger scale, to ensure enough internal volume for the electronics and moving parts) a great actively-guided, Sun-seeker scale model. Also:

If you launched it when the Sun was on the local North-South meridian, or within about two hours of the meridian in either direction (Local Noon +/- 2 hours), the IRIS-T model would climb nearly straight up (and if you had enough horizontal space and not too much motor impulse, launching it earlier in the morning, or later in the afternoon, would give a more scale-realistic flight path without risking losing it), and:

While there is, of course, the "only within 30 degrees of local vertical" launch angle rule, if you have an isolated location with nothing except moist (*not* dry and flammable) pasture or sod that the model could hit, it would be like (in relation to the public nudity laws) walking around Skyclad (sans clothes) in a deserted and un-illuminated place at 3:00 AM, where the effects on others--caused breaking the rule--are nonexistent, because there's nothing and/or no one to harm or shock.
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http://www.lulu.com/product/cd/what...of-2%29/6126511
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  #76  
Old 04-27-2018, 08:20 PM
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neil_w neil_w is offline
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Default Lugs

I gave up on doing anything fancy with the lugs. So here they are, just plain old lugs, on 1/16" standoffs so the rod will clear the front strake that's in line with it.

I thought about a *lot* of different schemes to integrate lugs into hanger-like structures, but I just wasn't happy with any of them for a variety of reasons.

The two lugs *are* in the same locations as the middle and aft hangers would be, and are approximately the correct scale length. So there's that.

Efforts will focus on the front hanger assembly, which is more visible, more interesting, and not actually a functional launch lug.
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  #77  
Old 04-28-2018, 10:45 AM
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Default Fin can finished

The control fins went on routinely. Quick and Thick fillets finish the job.

The rear fin can is now complete.
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  #78  
Old 04-28-2018, 07:31 PM
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Default Front hanger assembly

The front hanger assembly is a weird and complicated beast. The pictures I have show it... kind of. One problem is that the hangers are rail guides, but I'm using lugs and a rod. So I needed to keep the center of the hanger open to keep clear of the rod. Here's what I did.

Picture 1: start with a nice little pile of parts, the result of a bit of cutting and a lot of sanding.

Picture 2: The little rail guide extensions are glued to the side pieces

Pictures 3 and 4: The airframe is prepared: first 1/32" balsa pieces are mounted in front of and behind the first body band, to create an even platform for the side pieces. Then another long piece is mounted down the center.

Picture 5: The side pieces are glued on. Almost there.

Picture 6: Two little fillet-y pieces brace the sides of the assembly and blend down into the body band. Here's a closeup of one of the pieces before installation. It's mostly but not completely sanded to shape; the remainder will be done after it's glued in place.

Picture 7: A bunch of sanding, fillets, and CWF later, and the assembly is finished. It's a bit janky in some ways, but I'm happy with how it turned out.
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  #79  
Old 04-30-2018, 03:41 PM
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neil_w neil_w is offline
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Default Major Milestone

Exterior construction on the airframe is complete. By my count that is 71 pieces of cut wood and 17 pieces of cardstock. Not bad. Those bare lugs are practically begging for some embellishment, though. Hmm...

It'll be a while until I get to the nose cone, as I have some parts acquisition to attend to.
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  #80  
Old 04-30-2018, 11:48 PM
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I'm impressed with the amount of effort you've put into this! You may end up with Iranians wanting you to build some for them!
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