Build thread: Sport-scale IRIS-T missile, 1:3.8-ish

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I have thought about this.

I have three options I can think of:
1) As Nytrunner says: "Land on grass". This is generally true of my usual launch sites, but there's no guarantee.
2) Cover up the dome with tape or something for flying. That would be sad, but probably no worse than those who remove the towers from Redstone or Saturn models before flying.
3) Don't worry about it. I have materials to make at least a couple more domes if necessary.

I think if I could come up with a not-too-ugly mostly-transparent temporary cover, then I would go with #2. I am not sure how to do that, though. Odds of finding another clear dome that would fit well on top would be slim to none. If anyone has any ideas I'm open.

Option 4) Balsa or plastic nose cone for flight, contact lens nose cone when on display. I have "flight only" nose cones for all my birds with escape towers, after reading about how susceptible they are to landing damage. After spending hours assembling dowels into trusses and getting them to fit just right, you don't want to repair them after the first flight.
 
Option 4) Balsa or plastic nose cone for flight, contact lens nose cone when on display.
That would make me sad but it is a possibility. I think that, given all I'm trying to avoid (I think) is surface scratching, I should be able to go with just taping over the clear front if I don't care how it looks.
 
And now, from the department of "you've gotta be kidding me":

I had just finished applying my fin can decals, and applied the final coat of Micro-sol. Then, while tidying up the workbench I managed to knock the rocket off the stand. My first thought was to see if I had messed up any of the decals. Well, one was knocked off... but wait, something's not right... Oh: the fin had been broken off. :mad::mad::mad:

Yes that's right, the simple active of falling off a 6" stand (admittedly, it was thrust rather forcefully, by accident of course) broke off one of the control fins. This is the second control fin that has broken off, making me wonder what the heck is going on with the glue joints. I did the only thing I could think to do, which was glue it back down as quickly as possible. The paint will now need touching up, and then I will have to replace the final decal (the one that wraps around the back of the fin).

brokenfin.JPG

I'm starting to wonder if any of the control fins are going to survive a landing. Fortunately, they're almost 2" up from the rear of the rocket, so they shouldn't touch first, but still I'm going to be crossing my fingers at this point.

*sigh*
 
Sorry about the fin. I love your OCD attention to detail and all the techniques you've applied making your model. Nice model and great stuff!!! Looking forward to the launch report! :) :) :)
 
This is part two of three on the actuator fairings.

First, the tail pieces. The exact shape of these is not clear from the pictures I have seen, so I just picked a shape and am going with it. Start with some pieces of 1/4" x 1/2" balsa and beveled off one corner:
View attachment 341358

Then I hollowed out the ends, this time with 220 grit wrapped around a spend D engine:
View attachment 341359

Finally they are attached to the ends of the pieces from the previous posting.
View attachment 341360

Now they are glued onto the airframe:
attachment.php


The spacing around the motor hook is tighter than I expected, just barely fits!

From this angle they look great. I am not showing from directly behind because from that angle they look like garbage. Despite all my checking and double-checking, they are not sitting even, and as a result they are perfectly placed and oriented. You can't really tell unless you look from directly behind, so it's not a disaster, but I am still pretty pissed off about it. I'll have to do something to flatten the tops so the fins stand straight on them, but I'm not sure there's much more I could do. I'll just take solace in the fact that most folks won't ever notice. But I will. :bang: No pics of the f-up until I cool down a little and/or have a plan to deal with it.

Other than that, they are looking good ("Other than that, how did you enjoy the show Mrs. Lincoln?"). There is still one more step to complete them.


looking awesome!
 
While on a break from making a mess of my fin repair, I thought I'd do something useful. So I cobbled together this here laundry shelf out of a plywood 5055 centering ring and a couple strips of 1/8" basswood. Slathered on a nice layer of 30 minute epoxy to the underside for protection. There will probably be a piece of coupler involved in gluing the thing in, but can't do that until the epoxy is cured.
shelf.JPG

The kevlar is still attached to the motor mount, so it'll feed through this, and hopefully not destroy it. Even if the cross pieces break at some point, it's no big deal. I figured they'd be sure to hold the barf, which would then be sure to hold the shock cord, which would keep some weight forward.
 
Well, apparently I've reached the phase of the build where every thing I touch I destroy, sort of an anti-Midas touch. I had to wait a day before telling this particular tale of woe, until I cooled down and had a little distance. In other areas of life this would be something that I do not tell anyone about, but on these forums...
mistakesdemotivator.jpeg


Before I go on: yes, I still have a rocket. No, I didn't throw it in the garbage, or stomp on it, or light it on fire. I did however come dangerously close to one or more of these.

It all started with a laundry shelf, one stupid little laundry shelf, as pictured in the previous posting. While waiting for some suitable weather to do my next touch-up job on the repaired control fin, I figured it was a good time to finish up the shelf.

First I glued a short piece of coupler to it, just long enough to ensure it stays straight in the tube when I push it down in there.
shelf2.JPG

[Note that crossbars goes in to the tube first, because I thought that would ensure that the ejection charge could not blow off them off. Had I decided to put it in the other way, this would be very different posting.]

Anyway, I got ready to glue it in... about 9" down into the body tube. I applied the glue inside the tube with a chopstick, and got ready. Hmm, how to push that thing in there? Maybe if I use a dowel pushing along the inside of the body tube on one side... Well, that didn't work too well. It wouldn't budge past a certain point. Apparently it needed more even pressure around the perimeter of the coupler. So I tried nudging it on alternate sides, back and forth... making just a little progress, all of a sudden I heard something rattle. I looked in and one of the cross-pieces was gone. I had really glued those things in pretty well, and hadn't (I thought) hit them too hard (by accident), so how did it break out? Later examination shows that my glue joints held just fine; instead, the top layer of the plywood ring delaminated. Yay. Sorry I don't have a picture of this to show; I later threw it in the garbage with some serious gusto before it occurred to me to take a pic.

So now my laundry shelf was about 6" into the tube, and no longer useful. What to do next, I wondered as my glue was in the tube drying. Well, let's try to get that thing out. How? Well, I've always had good luck using a wire hanger as a hook. So, working more quickly than I should have, I tightened up the hook hanger hook and shoved it down there, hoping it would grab the thing and allow me to pull it out. However, I realized that the hook was a little too tight for the BT, so I tried to remove it. And here is where disaster struck: while pulling the hanger out, the end of the hook actually punctured right through the BT, and in a most inopportune location:
hole.JPG

What happened next? Well, because this is a family-oriented forum, I cannot properly recount the dialog that ensued between myself and the powers that be. Suffice to say that it is a good thing I was alone in the house.

Apart from feeling an almost uncontrolled rage at this stupidity, I also still had to figure out what to do with the hanger stuck in the body tube and the half-broken laundry shelf stuck in there below it. I put the whole thing down for a few minutes to let my head clear, lest I do something even more foolish. Eventually I got the hanger out safely, although not before almost doing more damage to the inside of the body tube. The only think I could think to do with the laundry shelf at that point was to finish destroying it, so I took some whacks at it with my dowel until almost all the wood was gone, and eventually it just became a short piece of coupler abandoned there in the tube, no way to get it out, but also not hurting anything

After this happened I stayed out of the basement for 36 hours, not wanting to look at it or even think about it. I have not figured out what to do about the hole. Whatever type of fix I attempt will almost certainly look like crap. Fortunately(?), the second paint touch up on the control fin repair also looks like crap, so the rocket's front and rear will be balanced out.

I've tried to think about where I went wrong here. It's hard to say. Some things I just wouldn't have realized in advance, like how hard it would be to push the piece of coupler in, or that fact that the plywood centering ring would delaminate. The ability of the hanger to puncture the body tube is something I should have foreseen, but I admit at the time I was shocked. Overall, I really only take a few concrete lessons that I would pass on:
1) Be very careful trying to glue something down deep into a body tube (at least one that is too small for your hand to fit in). Glue stuff like that in advance, cutting the BT. That's how baffles are typically installed AFAIK, using them as couplers. That would be easy.
2) If you think something is going to be hard, practice it first if you can. I could have practiced pushing the shelf into a scrap piece of BT55, and would have realized immediately that it would not work, and saved myself a good bit of misery.
3) Don't take up model rocketry.

Thanks for reading, I think. Anyone want to take this thing and finish it for me, before I wreck it any further?
 
It's like reading a story about myself, except the part where the protagonist remembered to cool off.

Good luck w/ the repair! I keep meaning to find some battle damage stickers to cover random imperfections.
 
Neil,
Don't despair, all is not lost! Seems to me that all of that is repairable. You can still have a laundry shelf. Try this: cut a piece of tubing of the same dia. as the main tube vertically. Overlapping the cut edges, slide it into the main body tube and see if you can push the unglued coupler down to the dried glue. Use a centering ring for your shelf: use a dowel to apply some glue just above the coupler in the tube. Using the split scrap tube, push the centering ring down to the glue and coupler. Careful, it will want to flip if it doesn't stay flush with the scrap tube. Inverting the main body and pushing from the bottom is an option.
For the hole, if the coupler is behind the hole then all you need to do is fill and sand: sand off paint and level the surface. Your choice of CA, putty, or Bondo to fill the hole. Sand again and refinish. If there is nothing behind the hole then cut a piece of scrap tubing and glue it on as a backing, then fill, sand, and refinish.
We've all been through things like this. I remember my frustration when the parachute shelves in my TLP kits wound up crooked in the tube. But experiences like these are learning opportunities. "What doesn't kill me makes me stronger". Good luck!
 
.... she swallowed a dog to catch the cat, she swallowed a cat to catch the spider, she swallowed the spider to catch the fly.......

Finish the rocket. Do enough repair to make sure the fin stays put and the hole isn't a structural hazard. Do minimum if any touch up. Take pictures that show the most attractive sides of the rocket away from the repairs. Fly and enjoy the rocket. Be proud of all the cool things you did to make this look awesome (which it still will despite the defects) and chalk up the lessons learned so you can find NEW mistakes to make on your next rocket!
 
Yes, to paraphrase BABAR and the great Alan Shepard : time to move on and light this candle.
 
Good luck w/ the repair! I keep meaning to find some battle damage stickers to cover random imperfections.
I only *wish* I could cause some damage in a location where a battle damage sticker would work....

You can still have a laundry shelf.
Now that you've suggested the split tube as a "pusher", which would have worked great, I've also realized another couple of ways I could have done it that would have also worked, and not resulted in the expulsion of expletives at 110 dB.

Would a 2055 ring work OK as a shelf with something like a D12? I never know how much open air space is needed in the shelf (or baffle for that matter) to avoid excessive back pressure and blowing the rocket apart. I've asked this a couple of times before but never gotten a clear answer.

kuririn said:
For the hole, if the coupler is behind the hole then all you need to do is fill and sand: sand off paint and level the surface.
Two problems:
1) there is a decal there.
2) paint repair is clearly a skill I have not mastered. Filling and sanding would just result in a larger repair area that I would then butcher when touching up the paint.

I think the only reasonable thing to do here is put a patch behind the hole (maybe some card stock), then put some white glue onto the outside of the patch and then wrap the whole thing tightly. Whatever is left sticking out... I dunno, figure out some way to sand it *carefully* and then apply messy horrible touch-up.

.... she swallowed a dog to catch the cat, she swallowed a cat to catch the spider, she swallowed the spider to catch the fly.......
I continue to inch ever closer to the horse.

BABAR said:
Finish the rocket. Do enough repair to make sure the fin stays put and the hole isn't a structural hazard. Do minimum if any touch up. Take pictures that show the most attractive sides of the rocket away from the repairs.
If only the hole weren't right over the logo. That *is* (or was?) the most attractive side.

Yes, to paraphrase BABAR and the great Alan Shepard : time to move on and light this candle.
I was so incredibly close to being finished before I broke the rear fin. Now I seem to be getting further and further away. It is kind of driving me nuts at this point.

In any case, thank you all for the moral support.
 
"Would a 2055 ring work OK as a shelf with something like a D12? I never know how much open air space is needed in the shelf (or baffle for that matter) to avoid excessive back pressure and blowing the rocket apart. I've asked this a couple of times before but never gotten a clear answer."

Short answer, I don't know. I suppose there may be a formula but that's over my head. But if you want "insurance", you can punch some holes around the central hole with a single hole puncher. I do know that the TLP kits use either a centering ring or baffle type ring as parachute shelves.
 
I have several half moons and rings as a quasi baffle in the BT20 of my Blackstar Voyager. Back pressure isn't such a big deal (that being said, I had an estes threaded retainer also)
 
If I'm going to try again with a shelf, I need to do it before I patch the hold in the BT (since the interior patch will interfere with trying to get the shelf down in there). I'm preparing a new shelf with a 2055 ring. Rex R. once posted that he uses BT20-sized holes in his shelves without problem, so I'll give that a whirl and cross my fingers. I will certainly have plenty of air space above the motor mount below the shelf, which I believe helps.

I scouted out the position of the abandoned piece of coupler. It's almost exactly 6" below the end of the BT. That would be a bit tighter than I would like, so I'm going to have to see if I can push it down a little further, like at least an inch (using a smart and appropriate method :oops:). I don't know if it's glued in at that position or just sitting there.

I'm a little unclear exactly how much room I need for the recovery stuff. The nose cone shoulder will take about an inch. The barf will take at least 1.5-2", although it could conceivably be compressed down a bit by the parachute. A 15" plastic or even a thin-mil chute can fold pretty small, probably 3-4". I'm thinking 7" down from the BT end is bare minimum, with 8" better. I think I was shooting for 9-10" the last time, so there's at least a chance that the existing coupler did not reach the glue, although if there was even a tiny bit of inadvertent glue on the inside of the tube it'd probably be enough to ensure that it's not going to move, ever.
 
Well, I was able to push the ring down to just a bit over 7" from the end of the body tube, which I guess I'll call "good enough". it was so easy to push it down in a safe manner, now that I had my head on straight. I stuck in a 2055 plywood centering ring and used a piece of PVC pipe to push it. Why oh why didn't I take the five extra seconds to thing about this the first time. :mad:

Anyway, installing the new shelf, which is basically just another 2055 plywood ring, should be routine.

But back to the hole in the side of the BT.

WARNING: THE REMAINDER OF THIS POST CONTAINS AN IMAGE THAT ROCKET BUILDERS MAY FIND DISTURBING
hole-closeup.JPG

The good news is that the hanger actually seems to have missed the blue part of the decal, which will have implications in my repair strategy. The bad news is, well, self-explanatory.

So, how do I fix that. I think the first part of the fix will consist of a cardstock patch on the inside of the BT. That will seal the tube and also provide a platform for whatever the rest of the fix is.

The tough part is that it seems very hard (impossible?) to get the little flap back flush with the body tube. One approach I was thinking was to lay a little TBII into the hole (supported by the interior patch), and push the flap down. Then wrap the whole thing tightly with something or other (waxed paper surrounded by a tight velcro wrap, maybe), and see if will hold down enough to look satisfactory. The problem is if it doesn't, and sticks up too much, then I could have an ugly job trying to scrape off the bulge and then refinish. This approach has the advantage of if it works, it will minimize the amount of touch-up painting I'll need to do.

Or, I could just cut off the flap right from the get-go and fill the hole (again, supported by the patch) with putty or CWF or whatever, and then paint over it. This should yield me a pretty smooth surface, but the paint touch-up will be ugly.

One thing I will *not* be doing is sanding around the hole, or doing anything else to enlarge the repair area. I've learned enough to know that that is a Bad Idea for me.
 
I'm concerned about what might happen when you do the wrap, i.e. glue might spread beyond the repair area.

For your consideration: Cut off the flap with tweezers and a sharp hobby knife. Glue a small backing behind the hole. Fortify the area from inside with a coat of CA. Place a small dab of unthinned CWF in the hole. Should be slightly larger than the hole. Sand to level when dry. I know you are averse to any sanding, but it can be done without appreciably enlarging the repair area. Touch up by brushing on primer then paint. Touch up the edge of the decal with a blue Ultrafine Sharpie. Clear coat when dry.

For sanding in tight areas, I couldn't afford to buy a pen sander, so I made a pencil sander. Punch out holes of sandpaper with a hole puncher, and glue to a pencil eraser. Great for sanding in small areas. Invaluable for my Micro Maxx builds. Works better on curved surfaces than an emery board.

IMG_20180818_192121.jpg

Just food for thought. Use whatever you feel most comfortable with.
 
Here's what I did.

First, I installed the laundry shelf. I pushed it down with the piece of PVC pipe and actually was able to get it a bit further down than I had original expected, maybe 7.25". That will hopefully leave enough room for all the recovery stuff.

Then I applied a patch on the inside of the body tube. I used a piece of folded-over 65 lb card stock; the double-layer was probably overkill, could have done with one. Shouldn't make much difference either way. This pic shows the shelf and the patch:
Shelf-and-fix-1.jpg

Next, I trimmed the exterior flap of BT on the outside of the hole. The flap consisted of several layers; I concluded that it was the inner layers (corresponding to the inner layers of the BT) that were preventing it from laying down flat(-ish). So I carefully trimmed just the inner brown bits. Then I laid a bit of TBII into the hole with a toothpick, and pressed down what remained of the flap. Because this all was only about three inches in from the end of the BT, I was able to squeeze it between my fingers (index finger inside the BT, thumb on the outside). I held it for a while until the glue had set up. It doesn't feel *smooth*, but it's also not sticking out in any appreciable way. Here's what it looks like right now:
Shelf-and-fix-2.jpg

Not great from close up, but also not a disaster. Tomorrow I'll apply some touch-up paint over it and hopefully that'll make it a bit better. I'm willing to live with this result.

The fin repair still looks like garbage, I'm going to apply some more touch-up paint there too. Shoulda left it alone after the first fix. Dunno why I need to keep learning the same lesson over and over.

Anyway, I'm off the ledge for now. We're in the home stretch.
 
Since it won't match your "purist" scale ethic this probably won't do, but what if you make a stylized sci fi iris flower decal and put it over the hole?

Sort of one of those
"Oh I meant to do that!"
things
 
Is it possible to make a DECAL the same color as the rocket and use it to cover the defect?

Interesting idea, and I would totally try it except I just don’t have it in me to do another round of decals just for that. I will definitely keep it in mind for the future.

Tonight I applied the touch up paint, and I think it looks good enough. Another two coats of paint also seems to have gotten the fin repair area to be “un-bad enough that I’m willing to stop fiddling with it”.

Further build updates (including pictures of the repairs) will now pause while I head to the beach with my family for a while.
 
Back from the beach, here are the final results of the fixes (including new decal for the trailing edge of the fin):
Fixes-final-3.jpg

Fixes-final-1.jpg Fixes-final-2.jpg

Everything looks kind of bad from super-close up, but overall I'm satisfied. I'm sure that if I were sufficiently motivated I could have done more to fill and smooth out the ding above the R, but in the interest of not making things worth and moving on with my life I'll leave it as is. At least now that it's all painted to match it's must less ugly than before unless you're really close up (like that picture). I might have to fight the urge to photoshop it out when I take beauty shots though. ;)

And thus decals are declared finished. Two final tasks are the nose cone weight and eyelet, and flat-coating the whole thing. Almost there!
 
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