Cuda Build

[Bruiser]

The Cuda won and the build has officially started. I like to draw how the aft end is planned to go together so I can have a ready reference during the build. I drew this up yesterday



From there I went to cut out the fins and ran into a problem after just a few cuts.

I received a new Skil 3386 band saw for Christmas 2019. My wife purchased it for me from Amazon. I have only used it a few times for cutting fins and centering rings out of 1/8th ply. Well there I was happily cutting away when the blade popped off. I open the cover to put it back on and I see the tire on the lower wheel has cracked apart and come off the wheel. I look at the top wheel and you can see many, many cracks in the tire there as well.

So I go inside to figure out how to start a warranty claim. Turns out she did not buy the Amazon warranty because Skil warranties it for 3 years. So I start reading the fine print and it turns out you have to register the tool 30 days after purchase to start the warranty. Guess what I didn't do...

I go to the Skil parts area to just buy the parts and it shows them discontinued. I found a pair of urethane tires on eBay that are supposed to be a great upgrade so I ordered them. They should be here by the end of the month.

Don't worry though, it won't hold up the build much, if at all. I still have my table saw, hacksaw and razor saw for cutting Luckily I have some centering rings available that I previously made I can use.

The pre-cut fin slots were too long so I wrapped a coupler in wax paper and slid it into the tube. Then I cut some filler pieces of card stock and glued them into the areas I needed to fill. I will apply some epoxy to the areas on the inside of the body tube when I am installing the centering rings and motor mount assy. I am also thinking of using a process called quasi-glassing on the outside of this rocket which will also reinforce the filler pieces.



That's it for now,
-Bob

 

[Bruiser]

I started by marking the locations of the centering rings on the motor tube


Then I put several wraps of tape to act as a stop for the centering ring


Next I slide on the centering ring and I glued the upper side of the joint


Now I moved the wrap down .
to the next lower centering ring. I also made another wrap of tape for the upper centering ring. I have slide on the bottom CR but I am not gluing it yet.


Now I have slide the upper CR over the tube and again, not glued.


Here I am putting epoxy in the tube far enough in so that the upper CR will catch the glue and attach it to the body tube


Here is the view from the top. I am still not gluing the CR to the motor tube so that I can still slide the motor tube out.


Here I have slide the motor tube out and I am gluing the back side of the centering rings with epoxy


Oh, well I need to start another post. You can only attach 10 files at a time.

-Bob

 

[Bruiser]

Here I have applied glue to the Motor tube where the upper CR is


Here I have applied epoxy for the second CR to push into a bead so that it will glue to the body tube. You can also see that I have coated the inside on the filler strips with epoxy as mentioned earlier


Now I have slide the motor tube assy into the body tube. This will secure it to the body tube and CRs


Next I removed the aft centering ring. It was only there to set the depth that the motor tube would go in


Here you can see the blue tape that the aft centering ring was pushing against during the motor tube install


Here is the way it sits now with the tape removed


That is it for tonight,
-Bob

 

[Bruiser]

Time to glue in the aft centering ring.

First I applied some epoxy. In this picture you can see I added a fillet to the middle centering ring, put glue on the end of the body tube where the CR goes and put some glue on the motor tube where the CR will be positioned.


Next step is to slide the CR in position. This will push the epoxy that I put on both tubes causing the epoxy to "pool" around the joint area.


Next is to flip the tube over so the epoxy will flow on to the CR producing a nice fillet.


More to come later...

-Bob

 

[Hobie1dog]

love the pictures, thanks

 

[Bruiser]

A picture is worth a thousand words and they help to explain so much. Documenting these builds the way I do are not only helpful to beginners (I hope) but also helpful to me because if I'm doing something questionable it gives more experienced peeps to point it out to me.

The boat tail is next so I started with epoxying the boat tail CR on. Of course I used a coupe wraps of tape to keep it located and then made a nice epoxy fillet


Of course it needs a nice fillet on the other side so I removed the tape and applied the epoxy


Next is the actual boat tail. I used payloadbay.com for the transition shape and cut it out of some card stock I had on hand. I made mine in two layers so it would be the same thickness as the body tube once glued up. The balsa I added to the rear of the aft centering ring comes into play now as the front of the boat tail glues to that. It can be kinda tricky getting the boat tail to stay in place and more gluing surface does help. It also helps if the bat tail is somewhat formed so I rolled it over a can a few times before attempting to attach it. Make sure to test fit before getting the glue out and have some painter's tape ready to hold it in place.

So on the first layer goes on and I use the painter's tape to hold it in place. Once the glue starts setting I'll take the second wrap and coat the surface with Elmer's white glue. I will put the cardboard down on a piece of paper, hold it in place with one hand, apply the glue and smear it with the other finger. If you hold it steady you won't get the glue on both sides Once the glue is smeared, carefully pull it off the paper and put it over the other boat tail. Position it so the seam is 180 out from the other seam. Now start wrapping it around the boat tail pulling off the painter's tape as you come to it. Continue wrapping until you are all the way around and apply painter's tape again to hold it in place. You can look it over now and you can work the edges a little (with your fingers) to get a nice round shape while the glue is still wet. This should give you a pretty nice boat tail but you will still need to apply some sort of filler after it is dried if you want it to look really nice. You can see the painter's tape and where I put a fillet of carpenter's glue around the CR to help hold it in place while it dries.


-Bob

 

[Ez2cDave]

Since this is a Scale model build, what data are you using ?

Dave F.

 

[Bruiser]

I think I discussed this a little in my "poll thread (2) Which Missile to Kick Off 2021 With? | The Rocketry Forum .

First thing is can a model of a display model be a scale model? Not for certain categories of scale contest but yes, for some.

I could not find any drawings of this missile that have measurements. Nothing official anyway. There was a thread on TRF back in 2013 (2) Cuda | The Rocketry Forum that has an attachment with measurements the OP came up with. I examined the photos that are available and came up with my own measurements. I bumped those against the measurements from that thread and they were very close to each other. I decided that even though my measurements are from photos (and that thread) my rocket will probably more scale than most scale models out there... How many Patriot model rockets are there that have no boat tail??? My Cuda has one

As for a paint scheme I will be using the photos of the display model. As best I can tell the Cuda was launched once back around 2012 but I could not find any photos of that particular missile. There are some artist drawings but they are conceptual.

BTW, I did send and email to Lockheed asking for basic measurements but heard nothing back.

Wish I could add to your scale data batch but I got nothing

Dave, I guess to answer your question directly, my scale data comes from photos

-Bob

 

[Ez2cDave]

Hmm . . . Apparently the "CUDA" is based on an AIM-120C AMRAAM missile.

Peter Alway posted AIM-120 Scale Data here . . .

https://www.rocketryforum.com/threads/looking-for-amraam-aim-120-scale-data.147131

Dave F.

 

[Bruiser]

Been working a little during breaks today. I applied thinned CWF to the boat tail and spirals this morning. Later on I sanded and applied a second coat of CWF to the areas of the boat tail that were low. A second coat filled the low spots and it is good to go now. I also took the time to cut the fin slots the rest of the way so the TTW fin tabs will fit.


Meanwhile I was working on the coupler/laundry shelf/recovery harness anchor. I made up a shelf last night by laminating two pieces of 1/8th ply together. Then I sanded the outside with the disk on my belt sander. I used my drill press with a step bit make the holes. This morning I sanded the holes with my Dremel tool and epoxied it into the coupler. Later on in the day I thinned some epoxy and coated both sides of the disk and the inside of the coupler. I still need to install the eyebolt. It's at home


I also worked on the mount for the lower rail guide. I found some 8/32 weld nuts locally and I had to laminate some 1/8th ply for a spacer. I have it installed where it is in the photos which intruded 1/4 inch into the coupler area. At first I thought "I just won't center the coupler" but then I thought if I notch the coupler, the coupler will actually "capture" the mount just a bit which could be good so that is what I did.


I invite you to visit my thread about Quasiglass over in the "Techniques" forum. I'd like to get some input about that because if I decide to go that route the time to do so is coming up fast. https://www.rocketryforum.com/threads/quasiglass.164093/

Thanks,
-Bob

 

[kuririn]

Why not turn your coupler/shelf into a full baffle?
Just need to glue on a ring with a few holes near the center on the other end.

 

[Bruiser]

Ah, I have thought of that. All my other rockets have baffles of assorted styles.

Let me ask this... Have you read my other builds and seen my launch reports? I have about a 50/50 chute deployment ratio. Another thing is that I felt it would be too close to the motor due to the size of the body tubes I ordered. I thought the slotted tub was longer than the 10 inch tubes that came in. The website did not have a specification on it. I added one in the comments afterwards. I thought it'd be as long as the tube in the Doorknob kit. The slots didn't really work out for me either. Live and learn...

So because of my recovery history and the short body tube I made the decision to forgo a baffle on both the Cuda and Peregrine (when it's time comes).

-Bob

 

[Bruiser]

Dave, that is some of the conceptual work I have seen. It doesn't really apply to the actual missile. Nothing is actually the same.

Been doing some tedious work today. I did get the coupler/laundry shelf/recovery harness anchor installed. I coated the body tube and the top of the centering ring with some thinned epoxy, then added some regular epoxy in the coupler area before sliding the coupler/laundry shelf/recovery harness anchor in place.


It slide together nicely and I stood it on end while it dried. That completed the construction phase of the rear assembly.


I did cut the upper body tube to the correct length but I haven't glued it on yet. I want to install the blind nut for the rail button first and I had to laminate some scraps together to get that just right. I also work on the fins some more laminating 1/16th bass to each side of the 1/8 ply to build up the thickness. Most of it will get sanded away when I profile the fins.

So that's it for now,
-Bob

 

[tab28682]

Your Cuda is looking good! I have some familiarity with the Cuda.

I am a model designer/builder for Lockheed Martin Aeronautics in Fort Worth. Back in 2013, myself and another guy built a full scale Cuda display model for LM MFC over in Grand Prairie, for trade show use. Pic from the internet attached. We also did a half scale Cuda, but could not find any publicly released pictures of it. The half scale model was all 3D printed. Was not a huge amount of actual building on the full scale Cuda. We used a slotted aluminum tube, and did glass molds for the fins and nose cone. Might have done a mold for the tail cone, but it might have been 3D printed. Been a while and I do not remember.

I also took one of our 1/20 sale open weapon bay F-35A models that we use for trade shows and outfitted it with a dozen Cudas in the weapon bays. Pic attached. We printed one 1/20 scale Cuda and made 12 of them using a silicon rubber mold and casting resin and scratch built some carriage rails.

Both of these were fun projects.

Before you ask, I have no scale data at all that I am allowed to share....

 

[tab28682]

Hmm . . . Apparently the "CUDA" is based on an AIM-120C AMRAAM missile.

Peter Alway posted AIM-120 Scale Data here . . .

https://www.rocketryforum.com/threads/looking-for-amraam-aim-120-scale-data.147131

Dave F.

View attachment 447253

The original Cuda that Bruiser is building is unrelated to the AMRAAM, other than the Cuda being proposed as a competitor to the AMRAAM. The Cuda is a Lockheed Martin Missiles and Fire Control (MFC) product, and the AMRAAM is a Raytheon product.

Note the forward fin drawing in Bruisers first post and the lack of forward fins in these drawings.

Note the transition in the drawing above where the Cuda body meets the AMRAAM rocket motor. Not the same diameter.

The proposals to use the AMRAAM and Meteor motors to boost this different variant of the Cuda shown in your post are more recent.

 

[tab28682]

One more thing. I saw in your project discussion post some discussion of how to model/illustrate the ACMs.

In terms of industrial display models, we typically have to build a display model to fit the customers available budget, which is almost never unlimited. We actually proposed modeling the ACMs in 3D, but it was a fair amount cheaper to represent them with cut vinyl decals, so that was the customers decision.

Sometimes we get to build museum scale models and sometimes we get to build functional industrial display models.

Looks fine from 5 feet away, or boosting at 150mph...

 

[Bruiser]

Tom,

Thank you so much for your post. It was pretty inspiring to read that it at least looks like a Cuda from someone who would know. I used the picture of your model when I was calculating my measurements.

About those ACMs. I had thought I would make a wrap for that section that had the ACMs cut out. But then it occurred to me I would have to paint them once I painted the wrap. I don't think I would do a great job of hand painting 240 or so slightly recessed holes... Maybe I should just go with vinyl decals for the ACMs. It's not as if I am building a museum scale model.

In researching the Cuda I ran across the M-SHORAD which looks very much like the Cuda. Would you know anything about them that you could share? I found one pic in the same color as your display Cuda and I found one pic in olive drab.



Thanks again,
-Bob

 

[kuririn]

About those ACMs. I had thought I would make a wrap for that section that had the ACMs cut out. But then it occurred to me I would have to paint them once I painted the wrap. I don't think I would do a great job of hand painting 240 or so slightly recessed holes.

Here's another idea. Make two identical wraps, punching holes through both of them at the same time.
Use one as a "stencil" wrap, spray painting the ACMs through the holes.
Paint the outside of the other wrap, then spray adhesive on the unpainted side.
Carefully line up the holes to the painted circles and burnish.
Easy peasy and you have some texture on that section of the rocket.
Having said that I personally would just do a decal.

 

[tab28682]

Tom,

Thank you so much for your post. It was pretty inspiring to read that it at least looks like a Cuda from someone who would know. I used the picture of your model when I was calculating my measurements.

About those ACMs. I had thought I would make a wrap for that section that had the ACMs cut out. But then it occurred to me I would have to paint them once I painted the wrap. I don't think I would do a great job of hand painting 240 or so slightly recessed holes... Maybe I should just go with vinyl decals for the ACMs. It's not as if I am building a museum scale model.

In researching the Cuda I ran across the M-SHORAD which looks very much like the Cuda. Would you know anything about them that you could share? I found one pic in the same color as your display Cuda and I found one pic in olive drab.
View attachment 447516
View attachment 447518

Thanks again,
-Bob

Have not had any recent interaction with LM MFC on Cuda or anything related. Looking at the full scale model, it appears they pulled off the "Cuda" decal and remarked the model as the M-SHORAD . Thinking about it, I believe we may have built two full scale Cudas for them....but that was 7 years ago and I have slept since them. I have no knowledge if the Cuda round to be used with M-SHORAD will be identical to what I have seen building the Cuda.

M-SHORAD is more or less the name of the system that will manage the Cuda in air defense: Maneuverable Short Range Aerial Defense (M-SHORAD)

 

[tab28682]

One other way to do the ACMs is to paint that area of the rocket black or some suitable color before you do the overall base coat of FS 36375 gray. Then, apply the cut vinyl dots. Paint the overall model color a little more heavily over the dots. Remove the dots. This gives a slight three dimensionality depth to the ACMs.

BTW, the missile radome was painted FS 36270, the inert round blue stripes are the FS number for whatever that color blue is called and the fins were painted in a steel/titanium like color. Pretty simple and much like an AMRAAM, except for the radome color.

 

[Bruiser]

I had thought about painting the area with black first then installing a colored wrap over the painted area and wha laa, there you go. Sounds good but there would be a seam.

Since I would use my cricut to do the holes I thought of using the cricut vinyl for the wrap but there's the color problem. I can not find anything saying it can be painted so I would be limited to whatever shade of gray they have. I also don't know how to address the seam with this

I have thought about using the Avery label paper. Theorically I could paint it after I run the cricut cuts the holes. I'd still have the seam issue but the color would match

In my RC Days I would simulate panel lines by laying down tape then brushing primer over the area. After the primer dried I would wet sand it a little so I could see the tape edge and then pull the tape off. That would leave a ridge that would simulate a panel seam. That is very simulair to what you are suggesting with using the dots as a negative mask. This process sounds promising.

I'll continue to think on it. I have time

-Bob

 

[kuririn]

I had thought about painting the area with black first then installing a colored wrap over the painted area and wha laa, there you go. Sounds good but there would be a seam.

I would think that glue would not adhere to paint as well as bare paper, hence the stencil idea.

 

[Bruiser]

I keep thinking about those bingo markers...

-Bob

 

[lakeroadster]

@Bruiser ,

Awesome build thread, really enjoying the detailed text with photo's.

Curious what technique you used to cut the backing ring shown in the photo below, and what the ring is made of?

Thanks!

 

[Bruiser]

The centering ring is made of 1/8th inch craft ply from Hobby Lobby. I glued some 1/8th inch balsa to the aft side of the CR. They are 1/4 inch wide. I used my compass to make the lines and then I cut them from some scraps with a new x-acto blade. The balsa pieces give the boat tail something to bond to.

-Bob

 

[Bruiser]

I got a little done over the weekend starting with the rear fins. They are made of a 1/8th ply core to which I have laminated 1/16 basswood on each side.

1) is where I am sanding the outboard taper. I put a shelf board on my lap and lay the fin on it and then use a sanding bar to get a flat taper. Once one side is done I flip it over and do the other.

2) is where I have drawn a line to denote the front and rear tapers. I started with the front taper using the same sanding process from above

3) is where I have moved on to the rear taper again sanding the taper as in step 2

4) is the sanded fin. I'll tell you this is the firs time sanding basswood this way. Normally I would have used balsa and then papered the fins. I wanted a little more strength and that is why I changed it up a little. Anyway, it's quite a bit harder to sand the tapers into the basswood





I also cut the forward body tube to length, glued it to the after tube and have applied cwf to the seam and spirals. I am pretty sure that I am going to do the quasiglass process on this rocket and I want to give it a good surface to start out with.


-Bob

 

[Bruiser]

Here we go. Since nobody even attempted to talk me out of it I've gone and done it. Yep no one told me to come to my senses not here of in the "Quasiglass" thread I started over in Techniques so here I am now...

The Silken Mist Cuda



It used most of one leg but there it is hanging to dry. I have the first coat of MINWAX water based polycrylic on it. I am going to let it dry overnight before applying the second coat.

I just realized I should have weighed it beforehand so we can know just how lightweight this process actually is. I'll weight it tomorrow though and than again after the second coat. A little subtraction and we will be close to the initial weight.

Just a little trivia type info now. I was worried about the color. I thought a tan or brown color might be too dark for a light gray missile. I searched for white nylons but couldn't find any at Walmart, the Dollar Store, the Base Exchange or the Commissary. I thought to myself "well where do the nurses get theirs?". After a few minutes of pondering I realized I had dated myself. Nurses no longer wear dresses and white nylons. It's all scrubs now.

Now I have to go back to sanding

-Bob

 

[Bruiser]

I have failed. I was so excited when I checked out the work on the body tube this morning I couldn't wait to get a second coat on it. I didn't even think to weigh it until I was all done. I'll have to try harder when I build the Peregrine (which isn't far away I think). So far I plan to use the same process on it, assuming this continues to go as well as it has been.

When I checked it this morning the nylon was attached to the cardboard well. The surface was actually rougher than I thought it would be feeling a lot like sandpaper. I applied the second coat and it is mostly dry now. I just took some fine sandpaper and used it to trim the toe off from the boat tail and the excess from the top. It feels a little less rough right now and I am tempted to sand but I am going to wait until after I get the first coat of z-poxy laminating resin on. I am going to wait until this afternoon for that so the poly has more time to fully dry.



On a side note, my bandsaw (ref post 1) is back in operation. The urethane tires from ebay did the trick. Hot water is your friend in getting the tires to stretch enough to go over the wheels. Hopefully it has many more years of service now.

Continuing to sand fins. I am on the front now.

-Bob

 

[Bruiser]

I have the first coat of finishing resin on now. I applied it with a small brush and then used a playing card as a squeegee to get off any excess resin. You can see the "roughness" I mentioned earlier on the bottom of the tube. Tomorrow I will do a light sanding before I put on a second coat.



-Bob

 

[neil_w]

Is that less work than just glassing?