MMX V-2 Project

[ep29030]

I recently purchased a nosecone/tailcone set from Balsa Machining Service. Parts# BMS20V2B, BMS20V2C. They were made for the old Apogee Medallion motors (10.5mm diameter) that existed for 2-3 years back in the late 90’s. They fit a BT-20 airframe. So this is my attempt to make these parts into a MMX kit.

 

[ep29030]

Here is the basic airframe. It requires a 2 inch piece of BT-20 airframe. Total airframe length is 6 inches. To make the fin templates, I used the K-22 V-2 kit instructions on Jim Z Website and scaled them to print at 56%, which is the difference between the original BT-50 and my BT-20 sized kit. I decided to use the larger semi-scale fin for this kit. If I make another one, I’ll use the scale sized fin and add additional nose weight.

 

[ep29030]

The tailcone is drilled through to fit a 10mm tube, which is a BT-4. The motor mount tube is a BT-2, 1” length. BMS does sell BT-2 and BT-4 tubes but only in 34 inch lengths. They also stock the BT-2 to BT-4 centering rings (eRockets also has centering rings). I chose to mount my BT-2 motor tube into a piece of BT-4 tubing, then slide the whole assembly into the balsa tailcone. You could alternately skip the BT-4, and use paper stips and glue stick to wrap your own centering rings that fit the balsa tailcone. Your choice. For the motor stop block, I used a small laser cut block I got from Ollie-OOP Rocketry. You can also use BT-1+ tubing for this purpose, available from eRockets. The kevlar is 100# waxed Kevlar I got from the kite store on a roll.

I slid rings on motor tube and glued them in place, glued the stop block into the motor tube, tied the Kevlar between the centering rings and gave the knot a drop of glue to set the knot. Once motor tube and rings were ready, I slide them inside a 1” long BT-4 tube and glued them in place. This is the final motor assembly that will go inside the tailcone.

 

[ep29030]

Semi-scale fins were cut from 1/32” basswood using the template. I had to do a little sanding to get them to fit the curve of the tailcone a bit closer. For the launch lug, I used a 1 inch piece from eRockets. These are plastic lugs. I always sand them with 320 grit paper before installation. Use medium CA to attach it, then glue fillets to help capture it to the airframe and give it a smoother appearance.

 

[ep29030]

Sanded the outside of motor assembly with 320 grit sandpaper. Covered it with a film of glue and inserted it into the tailcone.

 

[ljwilley]

Looking great! That will be fun to fly on tiny motors!

 

[ep29030]

Ah! Forgot to mention that before I started any assembly I covered nose and tailcone with CWF and sanded them smooth with 320 grit sandpaper.

 

[ep29030]

Currently putting on fin fillets. For model rockets I do two rounds of fillets with Titebond then all remaining fillets with Elmers glue. Elmers does not shrink as it dries, so there is no bumpy edge to the fillet. This is the technique scale modelers use for finishing.

 

[billpr]

Great looking rocket. Like the small size Keep us posted on the paint job.

 

[GlenP]

Looking great so far! Just for size comparison do you have something like an Alpha or Wizard rocket to show in a picture next to it?

 

[ep29030]

Looking great so far! Just for size comparison do you have something like an Alpha or Wizard rocket to show in a picture next to it?

Ask you ye shall receive. Here is the V-2 with its first paint color (yellow), beside an Estes Alpha III. Have not officially measured, but the V-2 should be right at 7 inches tall from the tabletop.

 

[ep29030]

OK, on with the build. I gave the rocket a heavy coat of Duplicator gray primer filler to start removing the woodgrain and tubing spirals. Looks pretty ugly after the primer dried, but that's the point--sand off the problems and smooth it up for final paint. I like a smooth paint, but I'm going to fly this rocket so I won't get too perfectionist about it. There is a point of no return here. Attached are pics after primer dries, then after it is sanded off with 220 grit paper.

 

[ep29030]

Looking at the V-2 schematics in 3rd ed of Rockets of the World, I decided to add the protrusions on the fins and the vents between the fins, near the aft end of airframe. So, how to make them? I decided to make the fin details using .020 sheet styrene, and make those tiny vents from slices of a 1/8" launch lug.

 

[ep29030]

I didn't attempt to accurately measure anything here--just eyeballed it. I'm flying this, not entering a scale competition. Just having some fun adding details. I will also simulate the silver vent ring above the fins later after final painting. All these details are being added after sanding off the first coat of primer and wiping the rocket with a slightly damp paper towel to remove sanding particles.

Fin details were cut from styrene, then each pice was removed and rounded on the ends. They were placed on the fins with a small amount of medium CA and tweezers. Once the CA had some time to set, I gently sanded the edges of the styrene on the fins, to round the edges a bit. The edges can be a bit rough from cutting, and they are too small to easily sand before attaching them to the rocket. For reference, those white squares on the cutting mat are 1/2” and the lines of dots are 1/8” apart.

 

[ep29030]

I knew the vents would be more of a challenge. To make them, I put some tape on a 1/8" dowel until the launch lug fit snugly. I let the end of the launch lug hang out about 1/8" past the dowel so I could start slicing pieces of it. The key to getting even cut is holding the blade perpendicular to the lug, and making a slicing motion as you move so it cut cleanly. With practice, you get better. I decided to cut up a 1"long piece of lug. I got 15-16 decent pieces to choose the best 4 to apply to the rocket.
To apply them, I used my Tamiya decal tweezers (expensive but good). To get glue on them and apply them, you have to barely grip them so you don't bond your tweezers to the pieces. This is where fine tweezers are a mandate. Anyway, I added a small film on the end of each one and placed it between the fins. I was surprised that they went on without issue. I used tweezers to adjust them before CA set.

 

[ep29030]

Looking at ROTW, I am going to paint this rocket in the V-2 #2 scheme, which is yellow and black.
After adding the detailed pieces, it was back to the shop for a coat of white Dupli-Color primer. Let that dry several hours, then it received a coat of Dupli-Color Yellow Engine paint. Will let it dry a couple of days before taping it up for black paint. Will probably do the black in two or three rounds, since the paint scheme is in three sections. Here is the rocket after the yellow paint. I may give it a wet sanding with 1000 grit paper to smooth the paint before starting the black paint. Wet sanding always improves the finish. The motor beside the rocket is a 13mm mini-motor (1.75" tall) for reference.

 

[billpr]

Looks great, thanks for posting. I'll order some parts and build one, to go with my mini Patriot rocket.

 

[darrenf]

Amazing!

 

[ep29030]

Got the bottom section masked and painted. Now masking the middle section. Will paint it later today.

 

[ep29030]

Getting close to paint completion. You can see two places where there are gaps (above fins, near tip of nosecone. Those are places where there is metal. I will add some strips of monokote for the metallic look once paint has dried. Then it’s on to clear coat and connecting up the recovery train.

 

[ep29030]

I added two small strips of monokote (color was 'Aluminum') for the two places there are bare metal. Color is now complete. Going to let it sit a couple of days then do a light wet sanding and then a final coat of Dupli-Color 1K Clear to give it some protection. Going to put a 1" mylar streamer in the kit for recovery.

 

[ep29030]

I just received two more of the same nose/tail cone sets from Balsa Machining. I want to build a Wac Bumper kit next.

 

[ljwilley]

Beautiful! I could never get such a good paint job done on such a small rocket.

 

[cvanc]

Seconded, gorgeous! Needs banana for scale!

 

[ljwilley]

Yes do a banana scale picture

 

[ep29030]

I’ll get a scale photo for you. Highly recommend the Tamiya tape for edging. Worth the cost.
Also, I went to brushing on the black areas instead of spraying it. Less taping to do and good results. I sprayed a small amount of paint into a cup then used those tiny Testors touch up brushes for paint application. The ones that look like white fuzz on the end of a plastic stick. I’m setting up a small booth so I can start airbrushing these small rockets. It gives so much more control over paint application.

 

[Bluegrass Rocket]

Excellent work Mark.

 

[SolarYellow]

Currently putting on fin fillets. For model rockets I do two rounds of fillets with Titebond then all remaining fillets with Elmers glue. Elmers does not shrink as it dries, so there is no bumpy edge to the fillet. This is the technique scale modelers use for finishing.

Classic Elmer's Glue-All, or something else? I hate the gaps that show up when doing fillets with shrinking wood glue.

 

[ep29030]

Classic Elmer's Glue-All, or something else? I hate the gaps that show up when doing fillets with shrinking wood glue.

I do 2 rounds of fillets using Titebond yellow glue (I’m using Titebond III at the moment), then I switch to 2 rounds of Elmer’s white glue to give smooth edges. This gives you the best of both types of glue.

 

[ljwilley]

I have always had problems with paint bleeding, that is why I recently got some new Tamia tape. I will see how it goes!