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-   -   IRIS-T paint and markings info wanted (http://www.oldrocketforum.com/showthread.php?t=17158)

neil_w 03-15-2018 08:38 AM

IRIS-T scratch build (was: paint and markings info wanted)
 
I'm scratchbuilding a sport-scale IRIS-T over on the other forum .

UPDATE: I will post brief summaries of the build to this thread. For full details see the TRF thread. Build updates start here

I have collected a lot of pictures of it from the web, but I still have some questions on the paint job and various letterings and serno plates. This is sport-scale so I'm not demanding everything be 100% accurate, but I'd like to do the best I can within reason. Was hoping someone here might have some insights.

The paint job I'm working in a hybrid of others I've seen, but most closely modeled after this one:
.

Here are some questions:
  1. Would the blue IRIS-T logo be on both sides or just the one? I've never seen a picture of both sides of the same missile.
  2. Between the main fins, just in front of the aft blue stripe, there's a "WARNING" box. Anyone know what the text might be in there?
  3. Anyone have any concrete info about the various serno plates all over the missile? I have a reasonable idea about the Guidance Section plate at front (shown in some pictures); the others I'm really guessing at at the moment.

If anyone has any info about this stuff or could point me to someone else who might, I'd appreciate it. I tried posting these questions on the Finescale Modelers forum but have gotten no responses so far.

tbzep 03-15-2018 08:48 AM

The logo won't be on any operational missile, just the ones that are on display or the mockups and demonstrators at air shows, etc. My guess is that the ones meant for "show" have it on both sides so it can be loaded on either side of the planes. Either that or they just do a mirror logo version for the opposite mount.




neil_w 03-15-2018 08:56 AM

Quote:
Originally Posted by tbzep
The logo won't be on any operational missile, just the ones that are on display or the mockups and demonstrators at air shows, etc. My guess is that the ones meant for "show" have it on both sides so it can be loaded on either side of the planes. Either that or they just do a mirror logo version for the opposite mount.

Yeah, I considered that possibility. I guess that it would look kind of goofy with logos on both sides, given that the logo is already near the top of the airframe to keep clear of the side... stuff.

blackshire 03-15-2018 08:48 PM

Thank you for posting this! (It looks like large numbers of retired Sidewinder rocket motors may soon become available for sounding rocket use...) The IRIS-T is an historic missile, because it was developed to be a "drop-in replacement" for the venerable AIM-9 Sidewinder. (The Wikipedia article about the IRIS-T (see: http://en.wikipedia.org/wiki/IRIS-T ) contains some interesting scale-related material:

It includes a video that shows--and well--the cylindrical infrared seeker moving (scanning) inside the transparent..."lidome?" (the optical equivalent of a radome, transparent to infrared--and also visible--light) nose cap. This would make an interesting Sun-seeker scale model, using a photocell, a solar cell, a photodiode, or a phototransistor as the optical sensor. Also:

A surface-launched, radar-guided IRIS-T variant, with a sub-caliber ogive/cylinder/transition forward section (see: http://en.wikipedia.org/wiki/IRIS-T...IRIS-T_SL-2.jpg ), is also being developed. It comes in two versions, the IRIS-T SLS (short-range) and the IRIS-T SLM (medium-range). The IRIS-T can also be used as an air-to-surface missile (the Royal Norwegian Air Force has tested this capability), simply by using different software, and:

A navalized, fiber-optic-guided IRIS-T variant (with shorter-chord wings, see: http://en.wikipedia.org/wiki/IDAS_(...le:BGT_IDAS.jpg ) for launch from German Navy submarines' torpedo tubes, called IDAS (Interactive Defence and Attack System for Submarines [the Wikipedia IDAS article can't be accessed via a posted link due to its URL's format]), is also under development. Four IDAS missiles will fit in each torpedo tube, stored in a magazine. With an official range of approximately 20 kilometers, IDAS will enable the launching submarines to engage enemy aircraft while submerged.

neil_w 03-15-2018 08:57 PM

Quote:
Originally Posted by blackshire
It includes a video that shows--and well--the cylindrical infrared seeker moving (scanning) inside the transparent..."lidome?" (the optical equivalent of a radome, transparent to infrared--and also visible--light) nose cap.

Figuring out how to model that is taking an inordinate amount of my time. At my scale (BT55) nothing will move, but I'm going to take my best shot at making it look reasonable.

Quote:
A surface-launched, radar-guided IRIS-T variant, with a sub-caliber ogive/cylinder/transition forward section (see: http://en.wikipedia.org/wiki/IRIS-T...IRIS-T_SL-2.jpg ), is also being developed. It comes in two versions, the IRIS-T SLS (short-range) and the IRIS-T SLM (medium-range).

The SL version is pretty spiffy too, I thought a bit about choosing it instead of the regular air-to-air version, but ultimately trying to do something with the nose seemed like fun. On the other hand, the SL would look more "realistic" launching vertically.

I'll leave it to someone else to model the SL, based on the way things are going so far one of these is going to be more than enough for me. :)

blackshire 03-15-2018 09:26 PM

Quote:
Originally Posted by neil_w
Figuring out how to model that is taking an inordinate amount of my time. At my scale (BT55) nothing will move, but I'm going to take my best shot at making it look reasonable.
One thought: In PSS (Power Scale Soaring, a variant of RC soaring--usually slope soaring--in which people build and fly gliding scale models of powered aircraft [with somewhat enlarged wings and tail surfaces, when necessary]), cockpit windows and canopies are often depicted as painted blue, green, or gray-green opaque objects. The Estes Space Shuttle kit and their foam Shuttle Orbiter used such decals (blue, if memory serves) to simulate the glass cockpit window panes. You could depict the IRIS-T's nose tip window like a PSS glider's cockpit windows or canopy.
Quote:
Originally Posted by neil_w
The SL version is pretty spiffy too, I thought a bit about choosing it instead of the regular air-to-air version, but ultimately trying to do something with the nose seemed like fun. On the other hand, the SL would look more "realistic" launching vertically.

I'll leave it to someone else to model the SL, based on the way things are going so far one of these is going to be more than enough for me. :)
The SL version does look pretty nice (rather sounding rocket-like). I know what you mean regarding "one and done" with demanding scale subjects (especially ones with conduits, like the IRIS-T) that require a lot of sanding and hand-fitting work to sculpt parts.

eljefe 03-15-2018 11:53 PM

1 Attachment(s)
Quote:
Originally Posted by neil_w
Here are some questions:

  1. Would the blue IRIS-T logo be on both sides or just the one? I've never seen a picture of both sides of the same missile.
  2. Between the main fins, just in front of the aft blue stripe, there's a "WARNING" box. Anyone know what the text might be in there?
  3. Anyone have any concrete info about the various serno plates all over the missile? I have a reasonable idea about the Guidance Section plate at front (shown in some pictures); the others I'm really guessing at at the moment.
Being a European missile, it's not one I've seen up close or know much about. But the photo you ask about is just a mock-up to show off at public events, so its markings are not representative of operational missiles.

Attached is a photo that may be more realistic, if you are interested in modeling an operational version. The warnings are fairly readable.

The one around the seeker dome reads: CAUTION NO SUPPORT OR HANDLING FORWARD OF THIS LINE

The one around the rocket motor reads: WARNING ROCKET MOTOR ARMED IF INDICATOR NOT GREEN

Also as a general note on ordnance markings, the two blue stripes in your photo indicate the round is inert. Note in the picture I posted the stripe around the warhead is yellow and the one around the motor is brown. These colors indicate live ordnance. Any bomb or missile component in blue markings is for display or training but is incapable of use in combat. At least that is the convention in the West.

neil_w 03-16-2018 08:00 AM

Quote:
Originally Posted by blackshire
One thought: In PSS [...] cockpit windows and canopies are often depicted as painted blue, green, or gray-green opaque objects.

That's what will happen if I admit defeat on the clear nose tip. :) But I am going to try *very very hard* to get the clear tip to work. I'm pretty sure I can do it, may not be perfect but I'll still feel better with it.

Quote:
Originally Posted by eljefe
Attached is a photo that may be more realistic, if you are interested in modeling an operational version. The warnings are fairly readable.

That's a great photo, somehow one I hadn't seen among all the ones I had found so far. Where's it from?

Quote:
The one around the seeker dome reads: CAUTION NO SUPPORT OR HANDLING FORWARD OF THIS LINE

Yup, that one I had already.

Quote:
The one around the rocket motor reads: WARNING ROCKET MOTOR ARMED IF INDICATOR NOT GREEN

That's a new one for me.

Quote:
Also as a general note on ordnance markings, the two blue stripes in your photo indicate the round is inert. Note in the picture I posted the stripe around the warhead is yellow and the one around the motor is brown. These colors indicate live ordnance. Any bomb or missile component in blue markings is for display or training but is incapable of use in combat. At least that is the convention in the West.

Fantastic info, thanks! That's exactly the sort of thing I'm hoping to learn. I had seen some pics with the yellow and brown vs. some with the blue, but wasn't certain of the meaning.

I don't have any preconceived ideas whether it's more desirable to go with the operational or display paint. I guess I had sort of settled on the blue theme because I wanted to include the logo, probably gonna stay with it.

Any idea what the warning box might say between the main fins on my original picture?

blackshire 03-16-2018 08:18 AM

I certainly wouldn't encourage you to give up on the clear nose tip. There are clear (diisocyanate) polyurethane casting resins (the Por-A-Kast [originally made by SynAir Corporation] product line included--and may still--a clear resin, and PolyTek, Ciba-Geigy, and Alumilite [and/or other manufacturers] may offer clear casting resins). There are also epoxy casting resins, and clear ones may be available. Bare-Metal Foil also carries numerous resins and RTV mold-making rubber formulations. You could use the nose cone itself to create the nose tip mold, and the nose cone--or a shallow, hardened "pour" of resin poured into another nose cone of the same type, then removed--could (after being sprayed with a wax-based mold release compound) be used as the inner window mold plug.

eljefe 03-16-2018 08:52 AM

Quote:
Originally Posted by neil_w
That's a great photo, somehow one I hadn't seen among all the ones I had found so far. Where's it from?


It came up in an image search. Source is http://www.lima.com.my/saab-iris-t/

Quote:
Originally Posted by neil_w
Any idea what the warning box might say between the main fins on my original picture?


It doesn't seem to show up in any other photo, so I'm not sure. Since it's a mock up, here are a couple guesses on what it might say:

WARNING DO NOT LIFT BY THESE SURFACES

WARNING FOR DISPLAY ONLY

neil_w 03-16-2018 08:59 AM

Quote:
Originally Posted by blackshire
I certainly wouldn't encourage you to give up on the clear nose tip. There are clear (diisocyanate) polyurethane casting resins (the Por-A-Kast [originally made by SynAir Corporation] product line included--and may still--a clear resin, and PolyTek, Ciba-Geigy, and Alumilite [and/or other manufacturers] may offer clear casting resins). There are also epoxy casting resins, and clear ones may be available. Bare-Metal Foil also carries numerous resins and RTV mold-making rubber formulations. You could use the nose cone itself to create the nose tip mold, and the nose cone--or a shallow, hardened "pour" of resin poured into another nose cone of the same type, then removed--could (after being sprayed with a wax-based mold release compound) be used as the inner window mold plug.
I confess my ambition stops short of casting my own pieces. Rather, I shall use a "found" piece of clear plastic and graft it on there. I've been scouring the world for items of the appropriate characteristics (hemispherical, clear, rigid, about 1" diameter) and have found a few. The best pieces I could use are these: https://kitkraft.com/products/1-25-4mm-clear-domes. The only reason I'm not jumping at them is the shipping charge, which would make it like $14 for just for that one part. Instead, I've found packaging for some toy items that should fit the bill. I think. :) I will start experimenting with that stuff sometime soon, right now I'm still sand-sculpting a seemingly endless string of balsa parts. :)

eljefe 03-16-2018 09:13 AM

1 Attachment(s)
Quote:
Originally Posted by neil_w
Any idea what the warning box might say between the main fins on my original picture?


Actually, found another picture at Nammo, a large Norwegian defense company that supplies the rocket motor, showing this detail.

https://www.nammo.com/what-we-do/ro.../amraam/iris-t/

WARNING DO NOT ROLL, TUMBLE OR DROP

(always good advice for a multi-million dollar explosive item!)

Quote:
Originally Posted by neil_w
  1. Anyone have any concrete info about the various serno plates all over the missile? I have a reasonable idea about the Guidance Section plate at front (shown in some pictures); the others I'm really guessing at at the moment.
Also shows some detail on this question. Those section details follow a similar format.

neil_w 03-16-2018 09:26 AM

Quote:
Originally Posted by eljefe
Actually, found another picture at Nammo, a large Norwegian defense company that supplies the rocket motor, showing this detail.
[...]
WARNING DO NOT ROLL, TUMBLE OR DROP

By golly you're right, I had that picture but couldn't make out the writing. It is consistent with your wording though.

Interestingly that render shows a hybrid paint job with the yellow and brown stripes but also with the logo.

Would the plates typically be copied on both sides, or just on one? (e.g.: the control section plate)

eljefe 03-20-2018 12:25 AM

Quote:
Originally Posted by neil_w
By golly you're right, I had that picture but couldn't make out the writing. It is consistent with your wording though.


This wording was borrowed from the Sidewinder IRIS-T is meant to replace. I found the same warning on an AIM-9M displayed at work.

Quote:
Originally Posted by neil_w
Would the plates typically be copied on both sides, or just on one? (e.g.: the control section plate)


Based on the American missiles I've seen, these markings only appear on one side of the weapon.

neil_w 03-20-2018 09:16 AM

Thanks, I think I now know enough to do a reasonable job with this. It won't stand up to educated scrutiny, but it should pass the basic sanity tests.

Should I post build updates here? I'm not gonna completely duplicate the build thread, but if folks would like periodic summary pictures here I'd be willing. It is an interesting build IMHO.

jetlag 03-20-2018 09:20 AM

Yes, please!

blackshire 03-21-2018 02:57 AM

Quote:
Originally Posted by neil_w
I confess my ambition stops short of casting my own pieces. Rather, I shall use a "found" piece of clear plastic and graft it on there. I've been scouring the world for items of the appropriate characteristics (hemispherical, clear, rigid, about 1" diameter) and have found a few. The best pieces I could use are these: https://kitkraft.com/products/1-25-4mm-clear-domes. The only reason I'm not jumping at them is the shipping charge, which would make it like $14 for just for that one part. Instead, I've found packaging for some toy items that should fit the bill. I think. :) I will start experimenting with that stuff sometime soon, right now I'm still sand-sculpting a seemingly endless string of balsa parts. :)
You could also vacu-form the entire nose cone in clear styrene (or maybe clear ABS plastic, if there is such a thing), then mask off the tip and spray-paint the remainder. Many PSS glider (and scale sailplane) builders do this, to create canopies (after vacu-forming, they heat the molded canopies moderately for a few minutes, so that the molding stresses are relieved; this prevents cracking of the canopies later). The IRIS-T's rounded nose would lend itself well to vacu-forming.

neil_w 03-21-2018 08:31 PM

Build intro
 
2 Attachment(s)
OK here's the start of the actual build.

OR model images are attached. The render looks pretty good, but OR limitations preclude many of the details that I'll be building into the actual rocket. I have found no drawings for this rocket so everything is derived from looking at pictures. The end result should be reasonably close but certainly not exact. Sport scale.

The model is BT55 and just under 30" long, for a scale of roughly 1:3.8.

neil_w 03-21-2018 08:53 PM

4 Attachment(s)
First bit of assembly is the "conduit" (or whatever) that runs along the bottom of the airframe, almost front to back. Started with 1/8" balsa, hollowed out the bottom and shaped the top. Came out pretty good.

blackshire 03-21-2018 08:55 PM

Quote:
Originally Posted by neil_w
OK here's the start of

OR model images are attached. The render looks pretty good, but OR limitation preclude many of the details that I'll be building into the actual rocket. I have found no drawings for this rocket so everything is derived from looking at pictures. The end result should be reasonably close but certainly not exact. Sport scale.

The model is BT55 and just under 30" long, for a scale of roughly 1:3.8.
Thank you! (I don't know what OR means ["something" resolution?], though). Looking at these images, I wouldn't be surprised if this model would make a good "tail-slider" boost-glider. (Also, a sufficiently lightweight IRIS-T model might even glide normally, having such a large--for a missile--wing area.)

neil_w 03-21-2018 08:58 PM

OR = OpenRocket

blackshire 03-21-2018 09:09 PM

Quote:
Originally Posted by neil_w
OR = OpenRocket
Ah--thank you. If your conduits feel like they're adding more mass than you think your selected motors can comfortably lift, they can be hollowed out--even quite a bit--without losing enough strength to matter. Smearing white glue or yellow wood glue (or thin CA or epoxy, although they're heavier than white or yellow glue) on the insides of the carved-out voids would reinforce the conduits.

eljefe 03-21-2018 10:03 PM

Quote:
Originally Posted by neil_w
First bit of assembly is the "conduit" (or whatever) that runs along the bottom of the airframe, almost front to back.


I can't guarantee what the Germans call it, but this is usually known as the "wiring tunnel." It allows the guidance section near the front to send actuator commands to the control section at the back. Most every currently produced air-to-air missile has this feature since canard control has lost favor to tail control.

neil_w 03-22-2018 08:46 AM

Quote:
Originally Posted by eljefe
I can't guarantee what the Germans call it, but this is usually known as the "wiring tunnel." It allows the guidance section near the front to send actuator commands to the control section at the back. Most every currently produced air-to-air missile has this feature since canard control has lost favor to tail control.


Awesome. Please hang around and correct all the other terminology butcherings that are to come. I don't know what hardly anything is called on this thing. :)

neil_w 03-22-2018 11:10 AM

"Body bands"
 
4 Attachment(s)
There are four "body bands" (eljefe, help me out here). They are implemented by wrapping 1/32" balsa sheet around the body. Wrapping with the grain, the balsa can easily conform to BT55 diameter without any special steps taken. Because I could only get 1/32" balsa 3" wide, I needed to use two pieces for each band.

Then, because I am insane, I papered them, using my standard Avery label paper technique.

Final picture shows confirmation that everything is in the right place by holding up a paper fin template.

ghrocketman 03-22-2018 11:14 AM

Missiles/Rockets/Bombs with blue stripes SUCK.
Inert rounds are lame even for display.

blackshire 03-22-2018 11:17 AM

Quote:
Originally Posted by neil_w
Awesome. Please hang around and correct all the other terminology butcherings that are to come. I don't know what hardly anything is called on this thing. :)
Both terms are equivalent, and are synonymous with each other, but I share your fascination with "alternate terms." Also:

Another German one is "brennschluss" ("end of burning," which refers to either the cessation of thrust itself, or to the time when this is to happen), whose English equivalent is "burnout." In his classic 1949 book, "The Conquest of Space" (illustrated by Chesley Bonestell), Willy Ley introduced "brennschluss" to the American public. He also pointed out that it is more accurate than "burnout" (which was often also used to refer to the burn-through of a rocket combustion chamber's wall [or the case wall or nozzle wall, for a solid propellant rocket], as well as the successful cessation of thrust via shutdown or consumption of all of the propellant). Whether or not "burnout" refers to a failure, or to the successful and planned cessation of thrust, is expressed and understood by connotation, depending on the circumstance, while "brennschluss" doesn't contain this ambiguity. In addition:

As well as referring to an "afterburner" (and "afterburning") as "reheat," the British often use "firing pad" instead of "launching pad," and also "blade" to refer to one fin (as in, "a three-blade fin assembly" [the way the Skylark sounding rocket's 3-fin tail assembly was described in a BAC--British Aircraft Corporation--booklet]). They also commonly refer to a "booster motor" (as for the Skua, Petrel, INTA-255 [which they built for INTA, Spain's space agency], and some Skylark variants) as a "boost motor" or just a "boost."

neil_w 03-22-2018 11:19 AM

Good stuff, thanks!

blackshire 03-22-2018 11:34 AM

Quote:
Originally Posted by neil_w
Good stuff, thanks!
You're welcome. There are others, like C-stoff and T-stoff (which referred to the Me 163 Komet rocket interceptor's fuel and oxidizer [I forget which was which])--even some postwar British hydrogen peroxide/hydrazine hydrate (or kerosene) rocket engines, which German scientists and engineers helped develop, had their propellant inlets stamped "C-stoff" and "T-stoff." Also:

I wonder what terms the Germans use for IRIS-T components such as the infrared seeker? I wouldn't be surprised if they use their words for, say, "heat eye," or "viper pit" (the U.S. Sidewinder got its name from its Sidewinder-like flight pattern [which is reminiscent of the way the Sidewinder rattlesnake moves], and from its pit viper-like infrared seeker).

blackshire 03-22-2018 12:05 PM

Quote:
Originally Posted by ghrocketman
Missiles/Rockets/Bombs with blue stripes SUCK.
Inert rounds are lame even for display.
What about green bands? (The inert motors of Australian sounding rockets in museums have such bands, and other countries may also use that color coding [and those countries will probably use the IRIS-T missiles].) Also:

I once had an inert MK4 FFAR (Folding-Fin Aircraft Rocket), which was also called the Mighty Mouse. It was *all* blue.

ghrocketman 03-22-2018 12:21 PM

If it's INERT, I don't like it.
Worse than a DUD, it's an intentional dud. :D

neil_w 03-22-2018 08:49 PM

Forward vanes
 
4 Attachment(s)
Each of the four forward vanes is cut from a 39 cent piece of 1/16" x 1/16" basswood.

The two side vanes are mounted on these bulgey things that were once again sculpted from 1/8" balsa. The first attached picture shows the profile after sanding and before attachment. After being mounted on the BT, the pieces were sanded down further to flatten them down some more.

The top and bottom vanes are mounted to very small and thin rectangular plates. These were made from 1/32" balsa, and sanded down further after attachment.

These came out pretty good I think.

eljefe 03-22-2018 10:25 PM

Quote:
Originally Posted by neil_w
There are four "body bands" (eljefe, help me out here). They are implemented by wrapping 1/32" balsa sheet around the body.


I remember there being a term for these, but it escapes me at the moment. I have a friend who'd know, so I'll ask the next time I see him.

The purpose of these becomes apparent when noting they line up with the hangers (called "rail-buttons" in model rocket lingo) that attach the missile to the launch rail. A lot of loads are transmitted into the missile body through these hangers, both during captive carriage and launch. The thicker "bands" in these regions provide a stronger structure to diffuse those loads and reduce the chance of the hangers being ripped right off the missile.

eljefe 03-22-2018 10:56 PM

Quote:
Originally Posted by neil_w
Each of the four forward vanes is cut from a 39 cent piece of 1/16" x 1/16" basswood.

The two side vanes are mounted on these bulgey things that were once again sculpted from 1/8" balsa.


Ha! I'd probably call these "fairings" but rather like the term "bulgey things." But I've been wondering what these are fairings for. My best guess is they are associated with the fuzing system. Any bomb or missile needs a way to detect when it's time to set off the warhead, and this is particularly important for air defenses where it is usually difficult to directly impact the target. It's easy to fly right by, so most missiles are equipped with a proximity fuze that detects a close approach and detonates the warhead to create a cloud of fragments. The goal is these fragments will intersect the target and hopefully do enough damage to bring it down.

The vanes, which I'm guessing may also be called strakes, could be part of that fuzing system. I'm not sure if they are antennas used by the fuze sensors or just simple aerodynamic plates to generate a little extra lift. They kind of resemble vortex generators, so they may be used to add energy to the airflow off the nose and help keep the air over those big wings attached at high angles of attack.

neil_w 03-23-2018 08:10 AM

Quote:
Originally Posted by eljefe
The purpose of these becomes apparent when noting they line up with the hangers (called "rail-buttons" in model rocket lingo) that attach the missile to the launch rail. A lot of loads are transmitted into the missile body through these hangers, both during captive carriage and launch. The thicker "bands" in these regions provide a stronger structure to diffuse those loads and reduce the chance of the hangers being ripped right off the missile.

Ya, I did notice that the hangers are all mounted to the bands. The main fins (itself a suspect term) are also apparently bolted to the bands in some fashion. The second band has no hanger, only the bolts to the fins.

It's interesting to me that all four bands are different sizes, but I guess each one is made exactly as large as it needs to be and no larger.

Quote:
Ha! I'd probably call these "fairings" but rather like the term "bulgey things." But I've been wondering what these are fairings for. My best guess is they are associated with the fuzing system. Any bomb or missile needs a way to detect when it's time to set off the warhead, and this is particularly important for air defenses where it is usually difficult to directly impact the target. It's easy to fly right by, so most missiles are equipped with a proximity fuze that detects a close approach and detonates the warhead to create a cloud of fragments. The goal is these fragments will intersect the target and hopefully do enough damage to bring it down.


Although I admit I haven't looked too hard, I haven't seen these bulges on other missiles.

Quote:
The vanes, which I'm guessing may also be called strakes


That is certainly possible. The term "strake" seems to be used somewhat flexibly to refer to some IMHO rather different items.

Thanks again for all the good info, I'm learning lots.

blackshire 03-23-2018 09:51 AM

Regarding the meaning of "strake," I found these two items:

[1] From Google's dictionary:

strake
strāk/Submit
noun
1.
a continuous line of planking or plates from the stem to the stern of a ship or boat.
2.
a protruding ridge fitted to an aircraft or other structure to improve aerodynamic stability.

[2] From Wikipedia in the article "Strake (Aeronautics)" [entering "Strake" on Wikipedia's search line will take you to it], the section of the article about strakes on weapons ["Munitions"] says (the two paragraphs are copied below):

"Certain air-deployed munitions, particularly "dumb" or unguided 500-pound bombs, are often retrofitted with bolt-on strake sets. Designed as an open collar with strakes fitted to the outside face, these strake sets are used to alter and normalize the aerodynamics of the weapon, yielding greater accuracy. As most such munitions were manufactured with only tail-mounted stabilizer fins, the addition of longitudinal strakes proves a much cleaner flow of air around the weapon during its glide, reducing the tendency to yaw and improving terminal accuracy.

"Strakes are also often found on "smart" or guided munitions as an aid to the guidance system. By stabilizing the slipstream of air traveling over the weapon, the actions of control surfaces are much more predictable and precise, again improving the accuracy of the weapon."

I hope this information will be useful.

neil_w 03-23-2018 11:10 AM

Strakes it is. :)

neil_w 03-25-2018 08:40 PM

Motor mount and tail cone
 
5 Attachment(s)
There's a lot to do in the rear of this thing. First comes the motor mount and tailcone.

The 24mm motor mount was installed with about .6" protruding from the rear. Rear centering ring is slightly recessed into BT.

Fluted ring of cardstock was installed into the trailing CR fillet while still wet. This will anchor the tail cone.

Tail cone is a single ring of 65lb cardstock. Fortunately, in this instance the seam will be covered by other stuff, so no need to smooth it out.

Glue is applied to the tip of the MM and the fluted ring, and the tail cone is installed.

blackshire 03-27-2018 11:13 AM

Quote:
Originally Posted by neil_w
There's a lot to do in the rear of this thing. First comes the motor mount and tailcone.

The 24mm motor mount was installed with about .6" protruding from the rear. Rear centering ring is slightly recessed into BT.

Fluted ring of cardstock was installed into the trailing CR fillet while still wet. This will anchor the tail cone.

Tail cone is a single ring of 65lb cardstock. Fortunately, in this instance the seam will be covered by other stuff, so no need to smooth it out.

Glue is applied to the tip of the MM and the fluted ring, and the tail cone is installed.
That's beautiful work (and the notched tailcone anchor ring is a prudent--and rugged--design feature)! If you want to further strengthen the tail cone, since there are no supporting triangular "ribs" under it (I'm not criticizing; it isn't a 'huge scale' model), thin CA or epoxy will work, but thin polyurethane glue or polyester resin (it stinks until it cures, but it wicks in very well and is very strong [RC model glider and airplane fiberglass fuselages often use polyester resin with the glass cloth]) would also work.

neil_w 03-27-2018 11:54 AM

Quote:
Originally Posted by blackshire
If you want to further strengthen the tail cone, since there are no supporting triangular "ribs" under it (I'm not criticizing; it isn't a 'huge scale' model), thin CA or epoxy will work

The interior of this one is actually coated with CA (other than the edges that were left clear for TB gluing). The area around the hook is CAed on the outside as well, for strength.

Also, this particular shroud is going to be very well protected (and to a certain extent reinforced) by the crap that is going to mounted on top of it. I'll get to that soon.

I don't normally put ribs under shrouds in my LPR builds. The one time I did ribs (and in that case I *really* did ribs) was under the ginormous main shroud in my APRO Lander II build. But that one was special. :)


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