A couple MPR scratch builds

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Pining for the Fjords
Feb 19, 2017
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So, with my Saturn IB ready for paint, I needed to find some excuse not to paint it yet. I settled on a pair of MPR scale model scratch builds, as I like MPR and scale models, but I've never done an MPR scale model, and I might as well make two while I'm at it.
The first one is an IQSY Tomahawk in 25% scale, putting it at a 2.2" tube. It's designed for versatility, and can fly on anything from a D12-3 to an I243WH (mach & 3700' :point:). E30's and F36's will likely be my motors of choice. It has lugs and rail buttons just for the fun of it, and a baffle from Apogee that didn't fit my Ventris (darn Estes PSII tube sizes) to protect the laundry.

The other is an AIM-120 AMRAAM missile at about 40% scale using Estes PSII 3" tubing (actually, the entire rocket is a kitbashed Estes Scion). It's designed for larger 29mm motors, like the F59WT, G68WH, H54WHLB, and H90CL. (Can you guess what case I have?) I'll likely just use dog barf, and it will only have rail buttons. All of the fins fit onto scrap plywood and the fins from the Scion with a little tweaking, so it won't be perfectly scale - it'll be pretty close though.
I have started both builds, which will follow in subsequent posts.
View attachment amraam.ork
View attachment iqsy_paper_2in.ork
Thanks for the Tomahawk file. I just ordered parts and will start on one myself!
Thanks for the Tomahawk file. I just ordered parts and will start on one myself!

I will warn you that those fins are not a nice shape unless you can laser-cut them - the trailing edge is angled at something like 5 degrees, which makes for some messy numbers. Also, like a lot of my scale models, it isn't really great in terms of scale accuracy - I readjusted a few things to make it fit available parts.

Have fun with it! If you want laser-cutting files for the fins, I can send you them - just pop me a PM.
I send .ork files to Nat at Upscale and he routes fins for me. I'm sure he can work with laser files as well if you want to post them. Can't wait to get started! I want to get this thing up on a fast "I" motor! The only other D-Region I have is a modified 29mm Estes kit that's gone up on hot "H" motors.

I think I'll up-scale this one to 4 inch later on. I scratch just about everything I build, and .ork files are the instructions for me, so I'm always pleased to come across a new file!

I like where your break point is in this one. That will make for a nice payload section to play with. I'm thinking drouge-less with a Raven, GPS and Archetype cable cutters.
Sounds like you've got it figured out.

It doesn't actually break in the middle as of yet - the middle section is a baffle, and I'm just popping the nose for now. If you can fit a 'chute in the bottom, more power to ya!

I may eventually make an alternate upper section that is partially payload bay, but the baffle is glued into the lower tube.
I'll be gluing the nose cone to the upper airframe section and use the upper section as payload. Raven controlled with no motor eject. In place of any baffles will be a single bulkhead. Rocketarium has 5" couplers. Thanks again for the file!
Ahh, I see what you're doing now.

The one issue I can see is that an I243 almost reaches the top of the tube, which might make the parachute a challenge - I suppose you could wrap it around the motor, but there's not much space there either.
So, I'm way behind on this thread at the moment, and the builds are progressing quite nicely, at least for the most part. I'd guess that I'll be playing catch-up for the majority of the build.

The first order of business is the Tomahawk. The build is fairly standard and pretty much like an Estes PSII kit, but with rail buttons.

First, the obligatory parts pic:
01 parts.jpg
Then the tubes were slotted and holes were drilled for railbuttons.
03 slots.jpg

The MMT was assembled...
04 mmt.jpg

Next step: the baffle. I had some fun with this one.

The pre-drilled hole in the forward baffle plate was waaaay too big for the included small screw eye and the larger one I used. Kinda disappointing, but I just drilled a smaller hole a bit off center and screwed the eye into that.
05 baffle1.jpg06 baffle2.jpg

Then the NC was sanded (those ridges Apogee gives you are nice if you want a boat tail, but otherwise annoying...) and the MMT was installed.
07 nosecone.jpg08 mmtin.jpg

And, of course, fins...
09 fins1.jpg10 fins2.jpg11 fins3.jpg
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Nose cone from apogee? Did you cut your own fins? I sent upscalecnc the .ork and received my ply fins a week ago or so. Just about to make my LOC order. I think I'll order 38mm parts as well as 29mm in case I decide to go with 38mm for crazy flights and adapt down for fun flights.
So, I have some catching up to do.

The parts are finally cut for the AMRAAM. Plywood is harder to cut than I thought! There are a few nicks out of the edges, but nothing a little CWF won't fix.

I used a technique I learned from Cap'n Low n' Slow's various builds to match the lower fins- pinning the tabs with dowels.

2 lfins1.jpg3 lfins2.jpg4 lfins3.jpg6 lfinsdone.jpg

I couldn't do that with the upper fins because my shortsightedness in planning fin tab heights gave me a 1/4" tall tab, so I just eyeballed. I thought they came out OK.

5 ufins1.jpg7 finsdone.jpg

And the parts pic...

8 parts.jpg

One more pic I have handy - I slotted the lower tube for fins.

1 slots1.jpg

More will follow... at some point...
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Ask mum for a band saw for Christmas!!

And I see you've got the customary 'messy bench'!!

(images didn't seem to come through though.. only one, the last one came thru..)
Yes, check your post picture failure.

And clean up your bench.
Ask mum for a band saw for Christmas!!

And I see you've got the customary 'messy bench'!!

(images didn't seem to come through though.. only one, the last one came thru..)
Yes, check your post picture failure.

And clean up your bench.

OK, sorry about that, fixed now...

About cleaning up the workbench, that's unlikely to happen anytime soon... It's been neatened up a bit since those pictures were taken, but most of the mess is still there.
Getting back to this thread... I got a bunch done, I've just been too lazy to update the thread.

Sorry, not a lot of pics... I just got a new crappy cell phone to replace my old crappy one, which died for pretty much no reason. :eyeroll: The upside is that it has a half-decent camera, so I don't need my digital camera to take pics. That means (hopefully) more pics in the future.

First, I glued a bit of plywood onto one CR and stuck a screw eye in it. I also added 3oz of clay to the nose- those little canards really hurt your stability...
9 cr.jpg11 nc.jpg

I glued couplers into the short middle tube, slotted the tube through the fore coupler, and glued in the canard fins. I also glued the eyeleted CR onto the fore end of the MMT.
10 finmmt.jpg

More recently, I glued the MMT & two fins into the fincan tube and drilled the railbutton & rivet holes for both rockets. Again, I apologize for the minimal pics.
12 fin1.jpg13 holes.jpg

Now, back to gluing...

Looking forward to seeing these at the field! looking very good!!

Can I make a suggestion:

Your forward CR with the eye screw. You're better going with a bolt & flat washer as you have more surface area acting against the shock of the shock cord. Using a screw, you only have the threads of the screw holding everything in. With an eye bolt, you can have a washer on the backside of the eye bolt, and that greatly adds surface area to the CR, which spreads out the shock load when needed. Also, the piece of added ply to the back side of the CR, had you brought it out to the edge of the CR, and matched the CR's circumference, you'd have a larger 'target area' to put the upper rail guide screw.

And, the nose weight, I'd stick a stick thru all that, to hold it all in place. Drill a 1/4" hole thru the NC & clay and jam in a 1/4" dowel or chopstick. Glue in, then sand flush. You don't want that to come loose..
Thanks Paul!

Your suggestions are definitely valid, but:
- My railbuttons use flanged nuts, so I don't need a block inside to mount them to.
- I'm using a 1/2" elastic shock cord with a steel leader, so there shouldn't be much load on the hardware.

On a different build, say with wood screw based buttons and a Kevlar shock cord, those suggestions would be great, and they're good to know for the future.

I'll consider the stick thru clay thing though- my current plan is to leave it as is and fly it on a light motor where it won't hurt if it shifts (CTI F59 comes to mind). Then if the clay loosens, even the slightest bit, I can reinforce it. Honestly it really doesn't need clay- I just like future proofing my rockets, and 3oz gets it up through the whole 29mm lineup.
On with the build.

I got the nose of the Tomahawk painted with the first coat of red.
13 ncpaint.jpg

I also got the aft fins of the AMRAAM CWF'd and sanded... I tried out the palm sander attachment for my cordless drill. It worked pretty well but threw up a copious amount of dust- I think a dust mask of some kind is in order for next round...

(I apologize for the horrible photography. I'm not exactly the most steady-handed person ever...)
16 cwf1.jpg
I like comparing my rockets to classic rockets of their approximate size. So, time to bring out the Ventris...
17 compare.jpg
Got the rest of the fins CWF'ed and sanded the other day, but apparently I didn't think to get a picture of it. I thought I got one or two, but it's not on my phone. Just imagine all of the fins looking like the AMRAAM's aft fins.

Today I threw a white base coat on the whole family of parts, minus the AMRAAM NC, which won't be painted- it needs to be white anyway and this is the best it's going to look.

I used almost an entire can of paint- that's a lot of rocket!
18 basepaint.jpg
I apologize for the image quality- a combination of a crappy phone and crappy photographer.
Moving forward... a bit...

I got the first coat of silver done on the AMRAAM fins. After painting, I noticed I missed a spot: I forgot to get some paint on the trailing edge of the forward fins. You can see the bare CWF in the pciture.

I was painting with the fore fincan (I guess?) "right side up", so 180 degrees from the picutre. I didn't get paint on it simply because I didn't see it.

19 silverpaint.jpg

Yes, I have a lot of stuff in my basement...


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Ben, I seem to be missing the pic.. (or, I can't see it..)

Should be fixed now.

Nothing really new has transpired on either build, other than that I ordered a 24/40 case and a few reloads including a pack of E28-4T's for the Tomahawk.
So, progress has happened! However the thread updating department has clearly been slacking a bit.

I got the black stripe done on the Tomahawk upper tube. I didn't get the black fin done at the same time because the fincan still needed some touch-ups... Touch-up work is now done, but the black fin still isn't. Probably tomorrow. Starting to look almost like a rocket!

A bunch of paintwork that I forgot to take pictures of occurred on the AMRAAM. I used fluorescent blue paint for the blue stripes because it looked like the closest match. Not a good plan- it reminded e why I hate fluorescent paint. Drippy, runny, doesn't cover at all, color inconsistent, etc.

However, after that the gray coat was a nice break. No major issues, dried fast, didn't run too much, didn't bleed under the tape...
20 paint1.jpg

Still no E28s. AeroTech was hoping to have everybody back in stock with 24/40 this week so hopefully it'll come in soon.


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More progress!

I got the black fin painted on the Tomahawk, as promised. I got a bit of overspray on the tube but it fits my criteria of a 30ft paint job. I'll probably touch it up at some point.
16 black2.jpg

Aaaaaand finished!
17 whole2.jpg18 whole3.jpg19 whole4.jpg

Rail buttons attached and retainers reunited. I had some similar pictures of the AMRAAM now that the paint's dry and I can put the whole thing together, but they were so awful and blurry I decided not to post them.

Both rockets are now ready to fly! That is, once I get my hands on some AP... Don't have anything bigger than an E9 at the moment.