ProSeries II Black Brant XII

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Theory

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Yup, build thread time!!!!!!

This is going to be a fun one and not just because it’s a DARN COOL rocket, but because it’s a DARN COOL rocket with tons of detail and a 29mm motor mount.

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As is typical of one of my builds, there will be some modifications. Will be adding plywood centering rings to use as anchors for 10/10 rail buttons, will be using an Aerotech aluminum motor retainer (all my 29mm rockets use these and I like keeping my retention solutions the same). Will also be using a Kevlar shock cord, “thin mil” parachute from Top Flight, and the rocket will get a unique yet appropriate paint scheme.

First up, laying out all the components. Lots of balsa pieces to cut!

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Each fin on the lower “boosters” is actually made up of 5 individual pieces. These are all glued together then sanded to the airfoil shape we all know and love.

Will use Tite Bond III for all fin construction. Do not believe there is a better glue for this.

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Method is to do one side at a time to minimize sliding. Apply some glue, spread with finger, wipe off excess, and place the individual pieces. The 4 fins are the. Pressed between two scrap pieces of granite with some extra weight applied

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Will be adding plywood centering rings to use as anchors for 10/10 rail buttons,

Hope that works for you. I haven't had best results trying to blind drill in to the edge of a CR. Instead I just CA a small plywood square inside the airframe, above the CR, and drill in to that. Easier to hit a 1"x1".
 
I have never used an inside piece on a LPR or MPR, or L1 rocket to put in a button. I just tap the cardboard body hole for the screw and CA it. Then put epoxy in the hole, put the button in and flip it upside down then so the epoxy forms an inside rivet.
 
Hitting the CRs has never been an issue and IMHO is one of the strongest ways the buttons can be anchored. It also allows for them to be easily replaced should that be needed.

My method is to measure, then measure again, then lay the airframe assembly on my drill press and drill the holes. This is done before the fins and has worked very well.
 
Looking forward to seeing your excellent building skills here. I'm almost done with mine; just a bit more paint left to do. Have used a lot of masking tape on this one! I also went off other sources for paint vs the box. :)

As for rail buttons, I am just sinking screws into the plastic in the lower section. I am keeping the 1/4" lugs too.
 
I looked at this kit as I love the old sounding rockets, especially the Nike, terrier, Talos. It is a nice looking kit. I sort of wish it was multi-stage, but it should look super-scale and nice taking off, even being a single stage rocket. I'll look forward to seeing it fly.

Edit: BTW, I watched a recent video on the history of the Black Brant. You may have seen it, but if not, here is the link--it's a good video:

The Most Reliable and Versatile Sub-orbital Rockets Ever Made; the Black Brant Sounding Rockets
 
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Is the metal Aerotech motor retainer come with the kit?
A surprise they didn't include the plastic Estes retainer (which does work very well).
 
Yup, build thread time!!!!!!

This is going to be a fun one and not just because it’s a DARN COOL rocket, but because it’s a DARN COOL rocket with tons of detail and a 29mm motor mount.

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As is typical of one of my builds, there will be some modifications. Will be adding plywood centering rings to use as anchors for 10/10 rail buttons, will be using an Aerotech aluminum motor retainer (all my 29mm rockets use these and I like keeping my retention solutions the same). Will also be using a Kevlar shock cord, “thin mil” parachute from Top Flight, and the rocket will get a unique yet appropriate paint scheme.

First up, laying out all the components. Lots of balsa pieces to cut!

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Similar - I went to BadBoy Rocketry's plywood/basswood cores for the fins. Not sure about using the plywood CRs; I might mix and match them to save a little weight. And simply use 250# Kevlar cord (2.7g) instead of the Kevlar/elastic (7.5g) mix. Definitely adding a swivel to the recovery system. I haven't decided on the parachute yet - the stock one is 25.25g. But I do have a thin-mil Top Flight chute I could substitute (18.95g). Does anyone know the Cd of the Estes parachute? I will likely sand down the plastic engine retainer to clean up the look a bit.
I want to fly on E, F, and G composite motors on it; perhaps even an H motor.
 
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Cut out the slots in the plastic pieces then cut them to length.

Opted to cut the slots first as the thought was keeping them as large pieces would add some needed rigidity, believe this was the right call as some were VERY challenging to cut. Snapped a blade on one. The trusty xacto proved better.

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I then took a stab at sanding an airfoil onto one of the lower fins. Will touch it up but believe it came out well.

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Cut out the slots in the plastic pieces then cut them to length.

Opted to cut the slots first as the thought was keeping them as large pieces would add some needed rigidity, believe this was the right call as some were VERY challenging to cut. Snapped a blade on one. The trusty xacto proved better.





I then took a stab at sanding an airfoil onto one of the lower fins. Will touch it up but believe it came out well.
Looks like we are at roughly the same stage in the build. I have a set of files on hand to widen out the slots but it was really easy to do with my Dremel (but harder to control). Like you, I air-foiled the fins down to the plywood core but to a slightly greater extent than you did. I didn't want to go to a thin knife edge because I wanted the durability. I went with wood filler instead of epoxy or thin CA for hardening the fins.
 

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I did an oopsie! During the assembly of the Talos/Terrier booster section, I epoxied the motor retainer to the motor tube too early. Its not a disaster; I will just have to sand out the core of the centering ring so that it fits around the retainer base. With a little luck I can secure it to the top of the retainer base. It does restrict the amount of space needed to add internal fillets, however, so I am going to have to use smallish tools or a longish Q-tip applicator to apply the glue.
 
I did an oopsie! During the assembly of the Talos/Terrier booster section, I epoxied the motor retainer to the motor tube too early. Its not a disaster; I will just have to sand out the core of the centering ring so that it fits around the retainer base. With a little luck I can secure it to the top of the retainer base. It does restrict the amount of space needed to add internal fillets, however, so I am going to have to use smallish tools or a longish Q-tip applicator to apply the glue.
I did the same thing then realized I still needed to add the aft ring enclosure over the retainer. I thought that was very confusing in the instructions.

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After inserting the MM, I thought wait... why do I still have a third CR? Fortunately it's cardboard and not plywood. I filled the gap with glue. I probably over sanded the fins. Too much Christmas movies and eggnog. They’re solidified with paper and CA. We’ll see how they hold up on landings.

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Sanded the centering rings that will anchor the rail buttons. Decided to have them sit inside the plastic pieces so I had to sand them down a fair amount.

Then I sanded the inside with some 320 and mixed up a batch of System Three T88. Some on the inside then a nice little filler to complete the install.

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Also sanded another fin and my right thumb in the process — face palm —

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thinking I am going to keep these fins and the forward balsa fins a little “meatier” as I like the idea of flying her on an H128 and the extra material may prove beneficial.

Once I have all for shaped I will go back and get them all fairly close to each other. Doing it all by feel now and the results aren’t too bad
 
Sanded the centering rings that will anchor the rail buttons. Decided to have them sit inside the plastic pieces so I had to sand them down a fair amount.

Then I sanded the inside with some 320 and mixed up a batch of System Three T88. Some on the inside then a nice little filler to complete the install.

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Also sanded another fin and my right thumb in the process — face palm —

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thinking I am going to keep these fins and the forward balsa fins a little “meatier” as I like the idea of flying her on an H128 and the extra material may prove beneficial.

Once I have all for shaped I will go back and get them all fairly close to each other. Doing it all by feel now and the results aren’t too bad
I think if the cardboard CR can keep the MM from ejecting forward, the balsa fins can handle the H128, probably.

Sorry about your thumb. The non-benevolent rocketry gods appreciate your blood sacrifice. 😅
 
Moving right a long on this one. Pushed pause on sanding the fins, not that I don’t absolutely love it, but, well…

To the motor mount. Added a pair of the stock paper centering rings and glued them in place with Tite Bond III. Measured down from the top of the airframe to ensure I had adequate clearance for plastic pieces to fully insert, the shoulders are actually quite long.

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The motor mount was then glued into the cardboard airframe but not adhered to the plastic lower piece. This allowed for lower internal fillets on the paper centering ring.

To adhere the molded plastic pieces to the cardboard airframe I went with System Three T88. A VERY thin layer was brushed on the plastic then a moderate amount was brushed on the cardboard. Epoxy was also brushed on the motor mount tube to bond it to the plywood centering ring. The pieces were then bonded together.

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Care was taken to remove all glue that “squeezed out” before the pieces were fully seated.
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The main Kevlar harness is a robust piece pulled from my bin of extra stuff. A quick note on that, gotta love the old bin of extra stuff, so very helpful at the times we need it most!

Not sure if the breaking strength but it’s a touch under 1/4”, super supple, has a nice loop in one end and was long enough for this. WIN!!!

This was mounted HPR style by epoxying it to the forward end of the motor mount. More than strong enough for this.

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Now I know what you’re thinking “Theory, how will the middle plastic transition piece fit as you glued that plywood ring in it, that ring you “need” to anchor the rail button you want to use?”

Well good question, and the dremel took about 23 seconds to make a nice little notch.


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The rest went together the same as the aft portion. Brushed on T88 and care to ensure all excess epoxy was removed.


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Finally the forward paper centering ring was notched and glued in place to “seal” against ejection gasses making their way where they are not wanted.


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Fins are close to being complete. Sanded to a uniform shape, well as close as I was going to try and get.

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The next step is to mix up some laminating epoxy and coat each. Used a foam brush and applied a heavy coat to each, then went back over each again, then hung them to cure.

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