Scale Staged Black Brant XI 1:7.5

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Completed motor facing end with connectors for ejection charge and airstart/separation.





The sled is 1/8 basswood with 3/16 launch lug material that fits right over the #6-32 rods.



The Raven 3 for scale. Plenty of room for a Featherweight GPS as soon as they produce an Android app!



Also just remembered I wanted to squeeze a camera in there too, might still be room to add it later on.

Earlier in the week I added the fin bracket details to the fin can but the paint came out horrible with peeling and everything; I don't even have a pic. I cut them off and will redo them.

 

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Wrapped up the altimeter bay tonight. I built a little compartment on the back for the battery. A screw through a small block holds it in place.



The bummer with the switches built into the side of the coupler is the sled ends up being difficult to remove to work on due to the wires, so I use a molex latching connector.



Here's the back of the removed sled/cap.



And the front.



Here's how it fits together with the battery and wiring on the back of the sled and the Raven and future GPS on the front.



The sled will slide out far enough for me to connect the Raven's USB or charge the battery without disconnecting the plug.

 

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Got the first test flight in today. Flew it on G76 to about 1,200 feet. Set it up for main at apogee ejection with motor ejection backup and test popped the nose cone at 400 feet. Perfect flight and recovery so next flight will be true drogueless DD setup.



The three white stripes are electrical tape. Since the sustainer doesn't have launch lugs I made a strap-on rail button assembly from 1/2" square basswood and taped it on securely with electrical tape. This also held the buttons out beyond the tailcone. Worked great. Third tape stripe was a camera.



At this point I'm ready to start building the second stage. Probably going to slow down a little at this point, not a lot of painting or flying left this year. I'll try to get the Talos and Taurus stages built over the winter and painting probably won't be until late spring.

 

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The Taurus booster will go together something like this. I don't think I'll be able to squeeze in more than a 3 grain 38mm motor.

3" diameter, drogueless dual deploy. Aft end will house 2.14" airframe due to the tapered end that will double as the connection point to the Talos booster. The interstage coupler will slide inside the 3" airframe and will be ejected to deploy the main chute.

 

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Launch was rained out today so I cheered up by starting on the Taurus booster.

I marked and cut the angles for the boat tail. Also drew up and cut the first template for the fins.



I will be using a Giant Leap Slimline retainer in order to fit inside the 2.14 airframe coupler. Still not much room to spare with wiring but I wanted to squeeze in the 38mm mount for longer burn times.

One of the things I enjoy about building scale is the challenge of working with the available space, not just being able to make the airframe longer, for example. This is going to be a squeeze!

 

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I built up the aft diameter for the boat tail with wraps of glued cardstock strips.



Here's how the interstage coupler will go together. It will be ejected for dual deployment of the second stage.

 

[Ez2cDave]

 

[markg]

The Taurus booster will go together something like this. I don't think I'll be able to squeeze in more than a 3 grain 38mm motor.
3" diameter, drogueless dual deploy. Aft end will house 2.14" airframe due to the tapered end that will double as the connection point to the Talos booster. The interstage coupler will slide inside the 3" airframe and will be ejected to deploy the main chute.

First time I'm seeing this project. Looks really cool. Similar to you, I'd like to put together a Black Brant XII, 7.5"->5.5"->4". Mine will be FG though, big and heavy.

It looks like you could make some room in the Taurus for a longer motor but reducing the size of the AVbay. Keep the coupler the same length, but recess the aft lid into the coupler. That's what I did on my Red FiberMAX.

cheers - mark

 

[Ez2cDave]

Similar to you, I'd like to put together a Black Brant XII, 7.5"->5.5"->4". Mine will be FG though, big and heavy.

cheers - mark

Speaking of the BBXII / BLACK BRANT XII . . . 1st two items by Peter Alway.

Dave F.

 

[Charles_McG]

Thanks for pointing out the Alway, Dave. I’ve been thinking about making my Terrier in such a way I could throw a Talos under it. And way having trouble finding Talos info.

There was such a thing as a Talos-Terrier-Recruit. The Recruit was the same OD as the Tomahawk, so I’d likely do an imaginary Talos-Terrier-Tomahawk.

If I was that much of a glutton for punishment.

This BBXII build is lovely.

 

[micro]

Thanks Mark, I had the same thought. Basically extending the motor into coupler section and shortening the av bay portion. A bulkhead in the middle would work except for the GPS tracker, I figured if I used a center 2.14 tube half way up I could squeeze the tracker antenna down the side between tubes. But I figure I'm going to have trouble finding a field/conditions to fly this thing as it is so 38/3g should be sufficient. If I ever have an opportunity to go to 4g I could always modify it.

Make sure to cross-post a link to your build when you get going!

 

[micro]

Thanks Dave and Charles, I have done a low power 3 stage XII before, this model is actually a XI which is very similar to the XII but without the Nikha 4th stage. And not as well documented. That would be cool though with flip-out fins for the 4th stage, just sayin'!

The other notable difference with the XI is the spin motors on the Talos...

 

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So I made a happy accident gluing up the interstage coupler. I meant to position the outer (3") coupler section further aft to allow for shear pins to connect the stages. That was the whole idea of having the 2.14 tube extend beyond the tailcone on the sustainer. I was distracted by TV. So I just cut some areas out big enough to get my fingers in there to place the pins. I think it'll work fine.



So I'll have pins connecting the sustainer to the coupler that will be sheared by the separation charge, and another set of pins holding the coupler in the booster to be sheared by the main parachute charge.



During assembly prep the coupler will be pinned to the sustainer before being covered up by and pinned to the booster.

 

[Ez2cDave]

Thanks for pointing out the Alway, Dave. I’ve been thinking about making my Terrier in such a way I could throw a Talos under it. And way having trouble finding Talos info.

There was such a thing as a Talos-Terrier-Recruit. The Recruit was the same OD as the Tomahawk, so I’d likely do an imaginary Talos-Terrier-Tomahawk.

If I was that much of a glutton for punishment.

This BBXII build is lovely.

https://www.rocketryforum.com/threads/talos-scale-data.155989/

Here is a TALOS-TERRIER-ORIOLE . . .

 

[micro]

The motor in the Taurus will extend a bit beyond the aft end in order to leave enough room for the wires and connectors to be tucked in and taped. Even with the slim retainer it is going to be pretty snug inside the 2.14 coupler.



That will help leave room in the Taurus but will make the Talos booster that much tighter. We'll see how it shakes out. I do end up with about 4" of compartment for the main in the Taurus section so I think that should be plenty.

 

[micro]

I received my GPS from Featherweight. The hardware is elegant, unfortunately the interface and usage are pretty clunky and documentation isn't current. Had to kind of figure it out for myself. It is technically still in beta so hopefully they iron those things out.



Here is the sustainer av bay with the GPS added. I need to move them around so I can access the USB port on the Raven without the antenna being in the way.

 

[micro]

Been working on the "through the boattail" fins for the Taurus booster. Same idea as the the Black Brant sustainer fins built up from 1/64 ply and skinned with 1/32 ply. They are a little heavier than I'd like but the booster will still be stable without additional weight so what the heck.

 

[Mugs914]

That is a great idea for the fin construction! The inner layers could be "hollow" if weight was an issue, but I can't imagine that they are much (if any) heavier that a regular ply wood fin, and there is a TON less sanding to get the scale profile!

 

[Keenan Cox]

Agreed! Seems like a very doable method, plus adds some decent strength to the fins. I imagine it's very satisfying to see come together.

 

[micro]

That is a great idea for the fin construction! The inner layers could be "hollow" if weight was an issue, but I can't imagine that they are much (if any) heavier that a regular ply wood fin, and there is a TON less sanding to get the scale profile!

Thanks, as I mentioned I've been thinking about this for some time but this is the first model I've done it on. It's definitely more precise than sanding in my experience. Plus I'm just cutting with an xacto knife so it's something I can do at the kitchen table.

The veneer plywood is definitely more dense than standard ply, but I agree with the air space it's probably a wash. I considered drilling out some material with a forsner bit before putting the skin on but I think it'll be fine.

 

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For the boattail I glued down three of the fingers for each fin and left two between each section unglued. This will allow me to get in there to fillet around the fins since I won't be able to get in the aft end.



I measured and cut the slots with a sharp xacto and straight edge.

I glued up the fourth fin tonight so hopefully I'll be gluing them in tomorrow.

 

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Huzzah! 4 fins complete.




And glued in!


Next will be the tedious task of adding glue fillets through the unglued tabs.

Also thinking about how the rail guide standoffs will go together. I'm thinking I'll employ some creative licence and not put them exactly in their scale locations in order to make them stronger. I haven't decided yet though.

 

[mbeels]

Those came out really well, very nice work!

 

[Forever_Metal]

Been working on the "through the boattail" fins for the Taurus booster. Same idea as the the Black Brant sustainer fins built up from 1/64 ply and skinned with 1/32 ply. They are a little heavier than I'd like but the booster will still be stable without additional weight so what the heck.

View attachment 399267

View attachment 399268

That’s the best idea I’ve seen so far (since I just saw it), thanks for sharing

fm

 

[Forever_Metal]

I'm going to use this tech on my Ajax...

fm

 

[micro]

F_M feel free to cross post a link if you do a build thread.

 

[micro]

I cut off a couple boat tail flaps to work on the lower rail guide standoff. Made from basswood strips with side gussets for strength, it's pretty darn sturdy.



Notched out the two flaps around the standoff and glued all of them down, the boat tail is looking nice!

 

[Keenan Cox]

Beautiful build so far! This has been a very cool build to follow. Thanks for posting your progress.

 

[micro]

Thanks! Having taken the time to get all the pics and post the updates it's nice to hear that people are actually following along. I've learned so much over the years from forums, hopefully I can inspire readers with some ideas for their future builds.

Here is the aft end of the Taurus ready for filler and sanding.

 

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Some analysis. I don't think I mentioned I was able to fly the sustainer again last month on a G64 to fully test the dual deployment. Nice flight and recovery with no damage and good descent velocities of 44ft/s drogueless and 18ft/s under chute. Probably won't be flying again until spring now.



This weekend I tested out the sustainer separation charge. I guessed on 0.25g BP which seems good. First I tested it with just the interstage coupler friction fit with tape. Here's the video just because it was kind of comical:



It landed just out of frame.

That seemed like it should actually be good with the shear pins added, so I assembled it with the shear pins and hung it from the tree for another test. I figured a vertical test would give me the best idea of how each section would react to the force and have the least possibility of damaging some fins.



I think that looked good. Good clean shear of the pins with no tearing.