Problem...

[Dr. Quigley]

I've been spending my afternoon designing a scale rocket of the soviet "Dvina" SAM missile, but I've run into a bit of a problem.

See, the missile has a short section at the bottom (about 1/5 of the length of the rocket) that is larger in diameter than the rest of the rocket. This presents a problem in the way of launch lugs. I've attached the .ork of my design if you need to see it.

Any solutions? Or will this have to be the second attempt at scaling a soviet missile I've had to scrap? (I started with the Topol ICBM before noticing it had no fins. I can see the conversation that would have made with the RSO now...)

[eggplant]

You can't simulate it in OR, but you could put the lug on a bit 1/4 wide wood that extends out so they are in a straight line. It won't be perfectly to scale, but it will work.

[fyrwrxz]

Hey Doc! Not elegant by any means. but if the fins are in alignment, you could go to the base (fillet) of the bottom fin put a lug there and run a line to the upper fins to attach a short (aerodynamically faired) lug on the fin spaced away from the body tube by the lower dimension. FWIW

[hornet driver]

Mount the upper lug externally--mount the lower one internally--easier than it sounds. I'm doing something similar on my stealth-ceptor build.

[[POW]Eagle159]

have the lug go THROUGH the shroud and in/ under the fatter tube...
Like....
http://modelrocketbuilding.blogspot....-trimming.html
http://2.bp.blogspot.com/-p9orJX-ZIP...%2B003_WEB.jpg
or
http://2.bp.blogspot.com/-p9CfkbC5MT...%2B003_WEB.jpg
like that!!!

[hornet driver]

159 has the idea

[[POW]Eagle159]

The driver hit ''submit reply'' before me....! ( I was looking up links!)
yes good idea.

[Dr. Quigley]

have the lug go THROUGH the shroud and in/ under the fatter tube...
Like....
http://modelrocketbuilding.blogspot....-trimming.html
http://2.bp.blogspot.com/-p9orJX-ZIP...%2B003_WEB.jpg
or
http://2.bp.blogspot.com/-p9CfkbC5MT...%2B003_WEB.jpg
like that!!!

I think I'll do that. It'll still stick out the tube, though, but it isn't much, and it's not a problem for me. As long as it goes UP, and not LEFT, RIGHT, or if a portal to hell opens up beneath it, DOWN. (Hey, it MIGHT be possible... There's no definitive proof that it can't summon a portal to hell...)

Thanks!

[[POW]Eagle159]

I think I'll do that. It'll still stick out the tube, though, but it isn't much, and it's not a problem for me. As long as it goes UP, and not LEFT, RIGHT, or if a portal to hell opens up beneath it, DOWN. (Hey, it MIGHT be possible... There's no definitive proof that it can't summon a portal to hell...)

Thanks!

You can cut the LL at an angle so its flush with the transition...

[luke strawwalker]

I've been spending my afternoon designing a scale rocket of the soviet "Dvina" SAM missile, but I've run into a bit of a problem.

See, the missile has a short section at the bottom (about 1/5 of the length of the rocket) that is larger in diameter than the rest of the rocket. This presents a problem in the way of launch lugs. I've attached the .ork of my design if you need to see it.

Any solutions? Or will this have to be the second attempt at scaling a soviet missile I've had to scrap? (I started with the Topol ICBM before noticing it had no fins. I can see the conversation that would have made with the RSO now...)

Ummm... okay...

Either of these are a NON PROBLEM... just put the lug on a STANDOFF-- a short piece of wood the lug is glued to, which is subsequently glued to the surface of the rocket tube (I usually wrap a piece of 220 grit sandpaper around an equivalent size tube and sand it lightly up and down the length of the tube to make the wood conform to the rocket tube nicely (slightly concave). This will move the lug out from the centerline of the rocket enough to clear any increased size anywhere along the side of the rocket.

The largest standoff I've used to date is about 1 inch in length, almost like another fin at about the midbody of the rocket, with the lug glued on the end. It was necessary to clear the large round clear globe of the whirlygig toy "nosecone" on my "Warp Drive" night-flying Big Bertha clone. A lower launch lug was glued about midway out on one of the lower fins as well. The main thing is to just ensure both lugs are perfectly aligned with each other and use the same offset from the rocket centerline.

The other alternative you could use is, sand or cut a notch in the bell-shaped bottom part to clear the rod when the rocket is on the pad. If the bell-shaped part is constructed of balsa or fiberglass, simply sanding or cutting a notch to clear the rod would be easy enough. If the conical part is made of cardstock it's even easier... Such methods are commonly used on large conical shaped rockets like the Russian N-1, the X-24 Bug, the old Quest Lifting Body glider kit, and the old "Vulcan" kit.

As for prototypes with no fins, again this is no problem... you just have to be creative... you can either simply glue clear fins directly to the body tube, or use insertable fins that are installed below the main body of the rocket on either side of the rocket motor into special tubes added to the motor mount (like many of the Dr. Zooch kits with Flame Fins-- check out Dr. Zooch Rockets website for pics or any of my Dr. Zooch build threads). While Flame fins are made from regular balsa fin stock and paper body tubes, the same thing can easily be done using clear tubes rolled from plastic sheet stock obtained from the hobby shop or online, and clear plastic lexan material, or clear fins glued to short paper tubes that fit into the "fin mounts" in the motor mount much like Flame Fins. There have even been clear plastic fin units sold with some kits, but they're kinda hard to find. One alternative I came up with was an insertable motor mount that simply friction fits inside the missile, extending a couple inches below it, with clear fins glued to that... the missile is then completely unencumbered by any of the fins or anything else for flight that is ugly on display, yet quite well equipped for flight with fins and motor mount in one piece. Do a quick search for my Minuteman III and/or Ares I 1/100 scale rocket build thread in the archives to see either one-- a picture is worth a thousand words!

Later and good luck! Looks like a REALLY neat project!

OL JR