byoungblood's 4" RIM-66 Standard Missile build thread

After attending a few club launches, I got the high power bug and started drafting up plans to scratch build a RIM-66 Standard MR Missile, one of my favorite SAMs.

Madcow's short 4" nosecone was the closest I could find for length, and I ended up buying their 4" Patriot to use as a basis for my project. I picked up an extra centering ring and an extra 19" length body tube to make the longer payload section I would need.

It will have a 38mm MMT, and will initially be single deploy for my L1 attempt. At the recommendation of another member here, I increased the rear fin size by about 20% to improve stability. With a AT H123 I have right around 2 cal stability with this design. If I should try to get my L2 with this rocket, it still has about 1.6 cal stability on a J510.

byoungblood said:

After attending a few club launches, I got the high power bug and started drafting up plans to scratch build a RIM-66 Standard MR Missile, one of my favorite SAMs.

Madcow's short 4" nosecone was the closest I could find for length, and I ended up buying their 4" Patriot to use as a basis for my project. I picked up an extra centering ring and an extra 19" length body tube to make the longer payload section I would need.

It will have a 38mm MMT, and will initially be single deploy for my L1 attempt. At the recommendation of another member here, I increased the rear fin size by about 20% to improve stability. With a AT H123 I have right around 2 cal stability with this design. If I should try to get my L2 with this rocket, it still has about 1.6 cal stability on a J510.

View attachment 249431

Click to expand...

I'm in! op:

First order of business was fabricating the rear fins. I printed up a template in Open Rocket, tacked it to one of the 1/4" blanks I cut out, stacked the other blanks underneath, then drilled holes through the tab area for alignment dowels. A few minutes on my band saw, and a lot more time hand sanding the leading edges, I had my rear set of fins.

Next, I started on the motor mount tube. This picture shows the forward ring in place, and waiting for the epoxy on the middle ring to cure. The fins will be sandwiched between the two rear centering rings. I installed the eye bolt for the shock cord and secured the nut with some red Loctite.



Here is a mock up of the rocket thus far. I still need to do a little sanding on the base of the tabs to get the fins flush with the body tube.

A speed trick you might think about... I tack the centering rings with CA (usually 3-4 drops per side), then do my fillets with epoxy, and tack the mount in place with few drops of CA. When I do my internal fillets, I use enough CA [EDIT]correction: glue (often Epoxy)[/EDIT] to make the fillet, and add a little more to lock the CR's in place.

Awesome!

Any chance you might post the .ork file? I'm also curious where you got your dimensions from (as I've not been able to figure out the lengths between stations (STAs) to firm up my numbers).

Thanks!
Jim

Here's the latest ORK file. I made some tweaks to it to accommodate the pre-cut fin slots.

View attachment RIM-66_4inch_v2.ork

Looks great so far!

After some further investigation, I just realized I forgot to compensate for the length of the nosecone when I put in my body tube length! So its going to be a tad bit (about 8") shorter! At least I caught it before I started epoxying couplers and body tubes in place!

Are you going to leave it open for DD for when you use it for your L2 cert (or just L2 launches)?

Well, losing that length is going to make it difficult to fit an av bay in there unless I cut the strakes in two and possibly shorten the MMT. I can't fly anything larger than J motor at my club's field, and it looks like a J500 puts it at about 3500'. Several of the guys in the club have put theirs up that high on single deploy, so I may just keep it that way.

Looking great so far!

Looking good. I have looked at building one, but the av bay always seems to be a problem. Consider using a cable cutter with electronics in the nose if you want dual deploy...

I think that will probably be beyond the scope of this build. I may still put an altimeter in there just to not rely on motor ejection.

byoungblood said:

Well, losing that length is going to make it difficult to fit an av bay in there unless I cut the strakes in two and possibly shorten the MMT. I can't fly anything larger than J motor at my club's field, and it looks like a J500 puts it at about 3500'. Several of the guys in the club have put theirs up that high on single deploy, so I may just keep it that way.

Click to expand...

You could always put the AV bay in the nosecone.

A little update.

Got the motor mount and rear fins epoxied in, pictures to follow.

For the strakes, I'm going to cut them out of 1/8" plywood, then laminate them with 1/16" balsa to get them to the same thickness as the rear fins. I think it would have looked funny having thinner strakes than the rear fins. I'm probably going to drill through the plywood in a number of spots to lighten it up since it will just be a frame for the balsa which will be the actual aerodynamic surface.

For recovery, I'm going to stick with a single deploy system for the moment, however I'm thinking about going with a cable cutter system to switch to dual deploy. Anyone have any opinions on a relatively fool-proof cable cutter system?

These photos show how I built the strakes. Because they are 25" long, it was going to be hard to build them all in one piece. I laminated some 1/8" balsa to make the forward, shorter part of the strakes. After I laminated the 1/16" balsa onto the 1/8" ply (that's a piece of rail I'm using to clamp everything together), I glued the two parts together, then papered the whole strake.

I was a little concerned about keeping these long strakes aligned while epoxying them to the airframe, so I took some small tacks and nailed them into the forward CR and cut the heads off the tacks. I did the same with one closer to the aft end of the strake, but secured them with some CA. It seemed to get the job done well enough.

And here is the progress so far. 3 out of 4 strakes epoxied, I'll probably get the last one done tomorrow and start doing fillets and filling spirals.

Are you going to add any detail to the root edge of the strakes?

I may or may not. I haven't made up my mind on it right now. It probably wouldn't be that hard to do, but I don't know if I want to add the extra weight or not.

Wow, this looks really cool. Very nice work! Can't wait to see the rest.

Something else you can do with long fins to keep them aligned is to clamp a piece of angled aluminum along the length of the fins, about 1/4" above the root so epoxy won't stick to it. I had to do that with an original design rocket I built (The SkyRazor) with a complex, single piece fin that has a total length of 25".



I had thought about tacking it the way you did, although I was going to leave the heads in place and attach the tacks from the inside to provide more anchoring strength, but decided it was going to involve more swearing that I was willing to utter.

The Standard missile is looking pretty cool. (That SkyRazor is no slouch either.)

I like the tack trick. For mine (I'm still in the contemplation stage), I've thought about making the strakes TTW at a couple of points along the length. Not long tabs, just enough to penetrate the body tube and anchor it there.

EeebeeE said:

Something else you can do with long fins to keep them aligned is to clamp a piece of angled aluminum along the length of the fins, about 1/4" above the root so epoxy won't stick to it. I had to do that with an original design rocket I built (The SkyRazor) with a complex, single piece fin that has a total length of 25".

View attachment 253027

I had thought about tacking it the way you did, although I was going to leave the heads in place and attach the tacks from the inside to provide more anchoring strength, but decided it was going to involve more swearing that I was willing to utter.

Click to expand...

Cool-looking bird. I'd like to see that fly.

OK...been a while since I posted about this, but never fear, I got it done, and got my level 1 cert today!

I wrapped up work on it back in April, and got one of the last orders of decals from Stickershock (I sincerly hope he decides to open up shop again after his wife beats her cancer, he does excellent work!). My biggest delay was just finding time to paint it, I had the construction work largely wrapped up by the first week of February but between the cold and rain it probably took me 5-6 weeks alone just to fill spirals and other imperfections, prime, sand, prime again, and finally paint once it stopped raining long enough to be able to shoot the paint. I was going to try for my L1 last month but the launch got rained out, so I had to wait until today.

Conditions were sunny, with a wind (maybe 6-7kts) from the west. Turns out I was the only one to launch today, despite about 8-9 folks showing up for the launch.

Motor (A-T H128) lit without a hitch, and kicked the rocket right off the pad. Watching the video afterwards I can see a slight weathercocking right off the rail, but it quickly straightened out and was a beautiful, straight flight. After holding my breath for a moment waiting for the 'chute to pop (went with 6 seconds of delay per sims, probably could knock a second or two off of it, as it is a bit draggy), I had a successful deployment and nice soft, but slightly muddy landing from where the adjacent field had been plowed up.

Video of the launch (I needed to clean the housing on the camera!)
https://vimeo.com/131306283

On the pad: