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  #31  
Old 03-22-2018, 12:21 PM
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ghrocketman ghrocketman is offline
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If it's INERT, I don't like it.
Worse than a DUD, it's an intentional dud.
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  #32  
Old 03-22-2018, 08:49 PM
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Default Forward vanes

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.
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  #33  
Old 03-22-2018, 10:25 PM
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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.
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  #34  
Old 03-22-2018, 10:56 PM
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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.
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  #35  
Old 03-23-2018, 08:10 AM
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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.
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  #36  
Old 03-23-2018, 09:51 AM
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blackshire blackshire is offline
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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.
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  #37  
Old 03-23-2018, 11:10 AM
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Strakes it is.
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  #38  
Old 03-25-2018, 08:40 PM
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Default Motor mount and tail cone

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.
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  #39  
Old 03-27-2018, 11:13 AM
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blackshire blackshire is offline
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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.
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Black Shire--Draft horse in human form, model rocketeer, occasional mystic, and writer, see:
http://www.lulu.com/content/paperba...an-form/8075185
http://www.lulu.com/product/cd/what...of-2%29/6122050
http://www.lulu.com/product/cd/what...of-2%29/6126511
All of my book proceeds go to the Northcote Heavy Horse Centre www.northcotehorses.com.
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  #40  
Old 03-27-2018, 11:54 AM
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neil_w neil_w is offline
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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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