Yeah, that does look great! You're being very thorough and methodical with the building, documenting, and testing, it makes for an excellent build thread. I'm enjoying following your progress, and looking forward to the 2 stage flight.
Scale Staged Black Brant XI 1:7.5
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Thanks! The process is definitely part of what I wanted to share.
The av bay for the Taurus is coming together. Just like the Black Brant's but more roomy. I'll use a right angle USB cable to connect without removing the whole sled.
I realized I need a separate battery for the GPS so I'll have to add one to the Black Brant's bay as well. Just waiting on connectors to wrap it up.
The av bay for the Taurus is coming together. Just like the Black Brant's but more roomy. I'll use a right angle USB cable to connect without removing the whole sled.
I realized I need a separate battery for the GPS so I'll have to add one to the Black Brant's bay as well. Just waiting on connectors to wrap it up.
Have to get started on the Talos booster so I can stop daydreaming about all three stages together! Here is the plan:
Body splits about in the middle. Coupler will be hollow up to about its midpoint to allow for 10 inches of motor which should fit any 2 grain 54mm. I think that's about all I can squeeze in but that should give me enough options. Chute will sit on top of the bulkhead in the upper section, and the interstage coupler will house the altimeter and will eject for dual deployment. This configuration allows me to still have dual deployment with motor backup.
So with a rough simulation using the upper two stages as built and the plan for the Talos, flying J315 to I170 to H160 I get around 8,000ft.
Body splits about in the middle. Coupler will be hollow up to about its midpoint to allow for 10 inches of motor which should fit any 2 grain 54mm. I think that's about all I can squeeze in but that should give me enough options. Chute will sit on top of the bulkhead in the upper section, and the interstage coupler will house the altimeter and will eject for dual deployment. This configuration allows me to still have dual deployment with motor backup.
So with a rough simulation using the upper two stages as built and the plan for the Talos, flying J315 to I170 to H160 I get around 8,000ft.
Have most of the body pieces cut, here's how the Talos booster will go together. Standard fin can setup, Pro54 2g case for scale. The coupler will be hollow with a bulkhead about even with the airframe joint. The coupler will be glued into the upper airframe section where the chute will be stored.
Above that will be the interstage coupler pinned in place. It will sit directly on top of the midframe coupler section making contact. That will transfer the load to the interstage during boost. I'll need to sand down the rings to fit inside the coupler section and cut a good piece of 54mm stock once I have a final length. Plenty of room in here for a Stratologger CF.
Above that will be the interstage coupler pinned in place. It will sit directly on top of the midframe coupler section making contact. That will transfer the load to the interstage during boost. I'll need to sand down the rings to fit inside the coupler section and cut a good piece of 54mm stock once I have a final length. Plenty of room in here for a Stratologger CF.
I just drew up the fins for the Talos booster. Going to be 14 sheets thick of 1/32 ply, ouch! I may need to put holes in these layers to lighten them up. I thought I'd show how I drew them up, but then I thought some might also be interested in the whole design process. That might be helpful to anyone who hasn't done a scratch build like this before. So let's go way back...
I knew the rocket I wanted to build, the Black Brant XI. Pretty much a XII but no finless 4th stage, a good candidate for a 3 stage model. There is a nice scale drawing of the XII by Peter Alway in Rockets of the World, shared here in post 38. First I drew it full scale in OpenRocket:
I only needed to modify the length of the sustainer which I estimated by proportion from the launch photo.
It's much easier to draw the fins on the full scale drawing and then scale the whole thing down. Complex fins can be drawn point by point after calculating the coordinates from the drawing:
The only bummer was the Taurus fins that are swept back 3 degrees and attached to the boat tail. Unfortunately there's no way to attach them to the transition in OpenRocket so the best approximation was to attach them to the body and slide them backward.
Once I had my prototype drawing, I needed to figure the scale. I knew I wanted to start with 4" for the Talos booster. Dividing the scale diameter 30.125 by 4 I get 7.53. Now I divide the other diameters by the same factor: 22.75/7.53=3.02 and 17.26/7.53=2.29. That's almost dead on for LOC 3" and 2.14" tubing ODs at 3.1 and 2.26. Next I figured if I rounded the factor to 7.5 to make it easy on myself what amount of error would I have in the body diameters? -0.4%, 2.2%, and -1.8%. The average of those looked pretty good to me so I used the OR scale function to scale my prototype drawing by a factor of 7.5.
From there in OR I replace body sections with actual component materials from the database but maintaining the scale lengths. That's my jumping off point to where I draw the complete build in OR. As I build it out I update my "as built" plan with true dimensions and masses of components for good flight simulations.
I knew the rocket I wanted to build, the Black Brant XI. Pretty much a XII but no finless 4th stage, a good candidate for a 3 stage model. There is a nice scale drawing of the XII by Peter Alway in Rockets of the World, shared here in post 38. First I drew it full scale in OpenRocket:
I only needed to modify the length of the sustainer which I estimated by proportion from the launch photo.
It's much easier to draw the fins on the full scale drawing and then scale the whole thing down. Complex fins can be drawn point by point after calculating the coordinates from the drawing:
The only bummer was the Taurus fins that are swept back 3 degrees and attached to the boat tail. Unfortunately there's no way to attach them to the transition in OpenRocket so the best approximation was to attach them to the body and slide them backward.
Once I had my prototype drawing, I needed to figure the scale. I knew I wanted to start with 4" for the Talos booster. Dividing the scale diameter 30.125 by 4 I get 7.53. Now I divide the other diameters by the same factor: 22.75/7.53=3.02 and 17.26/7.53=2.29. That's almost dead on for LOC 3" and 2.14" tubing ODs at 3.1 and 2.26. Next I figured if I rounded the factor to 7.5 to make it easy on myself what amount of error would I have in the body diameters? -0.4%, 2.2%, and -1.8%. The average of those looked pretty good to me so I used the OR scale function to scale my prototype drawing by a factor of 7.5.
From there in OR I replace body sections with actual component materials from the database but maintaining the scale lengths. That's my jumping off point to where I draw the complete build in OR. As I build it out I update my "as built" plan with true dimensions and masses of components for good flight simulations.
For the Talos fins I have Alway's drawings but I don't have the leading and trailing edge thicknesses nor the position of the middle ridge between faces. I'm going to fudge a little for durability like I did for the other fins and make the leading and trailing edges equal to the thickness of two sheets of the 1/32 ply I'm using for the skins.
That just leaves the position of the high point, seam, spine, not sure what to call it. I estimated the position at the root edge by blowing up the diagram to match the fin template I printed from open rocket.
For calculating the rest I use one half of the fin less the thickness of the skin, so thicknesses 0 at the leading and trailing edges and the high point where I marked (3.86/7.5)/2-.036=.221".
With a little trigonometry I find the position at the tip chord and a thickness of .179".
Seems to be right, my calculated location on the tip chord lines up with the drawing.
Then I divide out the thickness of the inner layers and measure and draw my lines parallel to the leading and trailing edges. I'll just tape this drawing to my ply and cut on the lines to make some templates.
That just leaves the position of the high point, seam, spine, not sure what to call it. I estimated the position at the root edge by blowing up the diagram to match the fin template I printed from open rocket.
For calculating the rest I use one half of the fin less the thickness of the skin, so thicknesses 0 at the leading and trailing edges and the high point where I marked (3.86/7.5)/2-.036=.221".
With a little trigonometry I find the position at the tip chord and a thickness of .179".
Seems to be right, my calculated location on the tip chord lines up with the drawing.
Then I divide out the thickness of the inner layers and measure and draw my lines parallel to the leading and trailing edges. I'll just tape this drawing to my ply and cut on the lines to make some templates.
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With the unseasonably warm weather last week I got a coat of primer on the Taurus.
Got all the parts cut for the Talos fins.
That's a lot of wood, heavier than a dead preacher my mother would say! After cutting and weighing the first one I decided to save weight I'd only extend the center 4 sheets for the TTW tabs. That's still a 1/8" 12 ply tab. Even then it all adds up to almost 10oz (280g). I have the parts taped together so I can remove some material tomorrow on the drill press.
Got all the parts cut for the Talos fins.
That's a lot of wood, heavier than a dead preacher my mother would say! After cutting and weighing the first one I decided to save weight I'd only extend the center 4 sheets for the TTW tabs. That's still a 1/8" 12 ply tab. Even then it all adds up to almost 10oz (280g). I have the parts taped together so I can remove some material tomorrow on the drill press.
Kinda late now I reckon, but what if you were to make some of the layers out of 1/32" balsa? I often make "balsa ply" out of several layers of balsa, cross grained then skinned with 1/64" ply. Tough stuff! Cutting the centers out of the ply bits might help too.
I think with your 1/8" ply core and 1/32" skins it would still be bulletproof, and a bit lighter.
I think with your 1/8" ply core and 1/32" skins it would still be bulletproof, and a bit lighter.
Good idea. The only reason I didn't do that is I didn't remember seeing balsa that thin around here. But now that you mention it I must be thinking of when I was looking for 1/64 for the upper stage fins. But I see plenty of 1/32 online that would be worth ordering if I can't find it locally. I will have to go back out and look! I only have 1/16 on hand.
I have made fins before with 1/8 balsa core and 1/32 birch skin that were surprisingly rigid, tough, and far straighter than 3/16 ply would've been.
I have made fins before with 1/8 balsa core and 1/32 birch skin that were surprisingly rigid, tough, and far straighter than 3/16 ply would've been.
In order to keep the fins from warping I glue them up two layers at a time in my highly technical jig- two layers of 1/4" plate glass with some weight on top.
When I glue on the skins, they only need glue at the high edges of each layer.
Four fins built!
They weighed in at 218g glued up, and are quite stiff. I like how they turned out.
Sketched the slots, I'll cut them with an xacto.
When I glue on the skins, they only need glue at the high edges of each layer.
Four fins built!
They weighed in at 218g glued up, and are quite stiff. I like how they turned out.
Sketched the slots, I'll cut them with an xacto.
Continuing work on the Taurus booster. Fin slots cut, forward centering ring and motor tube glued in place, spirals filled and sanded.
Fins glued in and internal fillets added. Glued in some ply backing for the aft launch lug.
Fins glued in and internal fillets added. Glued in some ply backing for the aft launch lug.
That looks awesome.
Really enjoying this thread. Thanks for sharing!
Really enjoying this thread. Thanks for sharing!
Yeah, I appreciate the details and fin construction, it's coming together great!
Tim51
Well-Known Member
Isn't that actually the Talos, not the Taurus? Either way, really inspiring stuff... great build thread.
Yes, that is a TALOS booster, not a TAURUS . . .
"Micro" is having a great build !
Dave F.
Over the weekend I revisited the sustainer av bay. I think I mentioned before I originally planned to run the GPS off the same battery as the Raven. Later I realized it should have its own separate battery since it would likely reboot when the ejection and airstarts are fired due to voltage drop. I figured it would have a cap to keep the computer alive for a few seconds like the Raven but nope.
The only place to squeeze in the extra battery was on the front. And I had to space the electronics so far apart the terminal blocks wanted to touch the inside of the coupler so I ended up just making a new sled from 1/16 aircraft ply. Here's how it ended up.
The Raven is at the top where I can access the USB port easily without removing the whole sled (and wiring to the external switches).
Then the GPS was placed as far to the lower corner as possible to allow the battery to be mounted in between. It hangs off the end but the sled is shorter than the bay and held in position with nuts on the threaded rod. I had those epoxied in place already so I didn't change the length of the sled. No need to rebuild the whole thing, it was just enough room.
Had to solder the power leads for the second battery to the switch already epoxied in the switch band but it wasn't bad. And replaced the 6 position plug with an 8.
These electronics will live in this rocket semi permanently. By popping the top end I can charge the batteries or access the USB port without removing the whole sled.
The only place to squeeze in the extra battery was on the front. And I had to space the electronics so far apart the terminal blocks wanted to touch the inside of the coupler so I ended up just making a new sled from 1/16 aircraft ply. Here's how it ended up.
The Raven is at the top where I can access the USB port easily without removing the whole sled (and wiring to the external switches).
Then the GPS was placed as far to the lower corner as possible to allow the battery to be mounted in between. It hangs off the end but the sled is shorter than the bay and held in position with nuts on the threaded rod. I had those epoxied in place already so I didn't change the length of the sled. No need to rebuild the whole thing, it was just enough room.
Had to solder the power leads for the second battery to the switch already epoxied in the switch band but it wasn't bad. And replaced the 6 position plug with an 8.
These electronics will live in this rocket semi permanently. By popping the top end I can charge the batteries or access the USB port without removing the whole sled.
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Getting back to the Talos booster, I reinforced the hollow coupler section with another layer of coupler.
The coupler stiffener was glued in and the bulkhead glued in flush to the end of it.
Just beneath the transition I glued on styrene strip for a straight edge of the detail.
My SIM so far shows I'm going to need some nose weight. OpenRocket/Rocksim/RASAero all agree roughly 0.5 cal stability with no weight so anything I can lighten in the rear will help. I was studying it and realized with the shortness of the lower body section I have such easy access to the motor, why not use a few wraps of masking tape at the top of the motor tube to retain the motor. I think it'll work great which is a shame- I have a nice aeropack retainer for it but it'll save about 50g to use a tape ring.
The coupler stiffener was glued in and the bulkhead glued in flush to the end of it.
Just beneath the transition I glued on styrene strip for a straight edge of the detail.
My SIM so far shows I'm going to need some nose weight. OpenRocket/Rocksim/RASAero all agree roughly 0.5 cal stability with no weight so anything I can lighten in the rear will help. I was studying it and realized with the shortness of the lower body section I have such easy access to the motor, why not use a few wraps of masking tape at the top of the motor tube to retain the motor. I think it'll work great which is a shame- I have a nice aeropack retainer for it but it'll save about 50g to use a tape ring.
I built from tip to tail so I could test fly the sustainer and 2-stage setup before going full stack. The second stage Taurus booster is about ready to fly except that it needs rail buttons. I need to build out the Talos booster at this point since it's the largest diameter portion, and I'll use the position of those buttons to finally align the Taurus buttons (the offset from the body is the thing here). Things don't always go together the way I imagine so I want to be sure of their final placement on the Talos before I modify the Taurus to match.
The fin can is slightly larger than the main body, which works out to just about another thickness of body tube. I cut pieces that fit between the fins.
Being conscious of weight and not needing double wall strength here I decided to cut some sections out of the fin can to save some weight. With the extra pieces glued on it'll probably be tougher than the intact single wall.
If I were thinking ahead I would've done this before completing the internal fillets! This seemed like a good time to glue in the aft centering ring with nice fillets.
It seemed obvious here to run the shock cord mount through both rings, replaceable style.
On top of the fin can pieces went strips of basswood. The taper up to the body will be wood filler. I placed some tape at the forward edge of the taper to use as a guide to run a blade to create the profile.
The fin can is slightly larger than the main body, which works out to just about another thickness of body tube. I cut pieces that fit between the fins.
Being conscious of weight and not needing double wall strength here I decided to cut some sections out of the fin can to save some weight. With the extra pieces glued on it'll probably be tougher than the intact single wall.
If I were thinking ahead I would've done this before completing the internal fillets! This seemed like a good time to glue in the aft centering ring with nice fillets.
It seemed obvious here to run the shock cord mount through both rings, replaceable style.
On top of the fin can pieces went strips of basswood. The taper up to the body will be wood filler. I placed some tape at the forward edge of the taper to use as a guide to run a blade to create the profile.
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That ring at the top of the fin can is where the Talos launch rail shoe gets bolted on, so that's where my first rail button goes. Pilot hole drilled, hardened with CA, and tapped for #8-32 screw. The basswood strip was also soaked with CA since it'll be out there wanting to get banged up.
The forward end reinforcement is a strip of body tube with a fillet of wood filler. The shoe mounting point is built up with some veneer ply to match the thickness of the aft shoe mount point. It's a little oversized for strength.
With both Talos guides on I shaved some off the rear Taurus standoff and built up the front mount point so all four buttons are aligned. As far as I can tell from pics the rear mount is just a rectangular stock and the front is made up of a few pieces bolted together.
I have no measurements for these parts so just eyeballing them.
With all four buttons in place I hung both boosters from a section of rail to verify alignment.
The Talos body sections needed a little twist from where I had them aligned in order for the interstage coupler to align perfectly with the Taurus.
So I made new witness marks where I'll align them when I drill for the shear pins.
The forward end reinforcement is a strip of body tube with a fillet of wood filler. The shoe mounting point is built up with some veneer ply to match the thickness of the aft shoe mount point. It's a little oversized for strength.
With both Talos guides on I shaved some off the rear Taurus standoff and built up the front mount point so all four buttons are aligned. As far as I can tell from pics the rear mount is just a rectangular stock and the front is made up of a few pieces bolted together.
I have no measurements for these parts so just eyeballing them.
With all four buttons in place I hung both boosters from a section of rail to verify alignment.
The Talos body sections needed a little twist from where I had them aligned in order for the interstage coupler to align perfectly with the Taurus.
So I made new witness marks where I'll align them when I drill for the shear pins.
Keenan Cox
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Exciting to see more progress on the build. Are all three stages using rail buttons?
Unfortunately I'm pretty much done for now until I can paint. It's 8 degrees F out right now. I did sew a parachute for the Taurus booster yesterday.
The sustainer has no rail buttons on my model. That's why I needed a sturdy interstage coupler to keep it straight and supported. Here's a pic of the Black Brant XII which is set up the same way on the rail as the XI. There is one support on the Black Brant stage, but I don't know if it's only for assembly support and retracted before launch or if it's some sort of piston that retracts immediately as the forward shoe leaves at launch. That seems like it would be asking for trouble even on the prototype so I'm assuming they retract the forward mount support when it's in launch position.
When I fly multi stage non-scale that are same diameter I put buttons on each stage.
The sustainer has no rail buttons on my model. That's why I needed a sturdy interstage coupler to keep it straight and supported. Here's a pic of the Black Brant XII which is set up the same way on the rail as the XI. There is one support on the Black Brant stage, but I don't know if it's only for assembly support and retracted before launch or if it's some sort of piston that retracts immediately as the forward shoe leaves at launch. That seems like it would be asking for trouble even on the prototype so I'm assuming they retract the forward mount support when it's in launch position.
When I fly multi stage non-scale that are same diameter I put buttons on each stage.
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With a little warmer weather I got out to the garage for a bit.
I sanded the transition on the top of the Talos, looking roundish. It's easy to see where it needs another coat of filler.
First coat of primer on the Taurus sanded off, then primed with a dark gray that makes the flaws easy to see.
I sanded the transition on the top of the Talos, looking roundish. It's easy to see where it needs another coat of filler.
First coat of primer on the Taurus sanded off, then primed with a dark gray that makes the flaws easy to see.
Talos and Taurus in various stages of priming and sanding.
It doesn't look like I'll be able to squeeze the chute burrito into the motor side for apogee test deployment so the two stage flight is going to have to be dual deploy on both stages.
It doesn't look like I'll be able to squeeze the chute burrito into the motor side for apogee test deployment so the two stage flight is going to have to be dual deploy on both stages.
This is really looking fantastic! I'm really enjoying seeing this come together, what a cool project.
Finishing update: black is on upper Taurus section. Sprayed the fins yellow (why I had white primer on the lower half). The yellow comes in gloss only so I wet sanded it with P600 and will apply a satin clearcoat. I think I will do the black body then the clear.
The Talos booster is about ready for white. After many iterations of priming, filling, and sanding the transition is smooth and round.
The Talos booster is about ready for white. After many iterations of priming, filling, and sanding the transition is smooth and round.
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Inspired me to build some smaller sport scale versions (BT55 and BT60) versions of at least the two upper stages... one black powder, and then the other with composites and electronics.
Thanks for the progress reports... really like the 'how to' on the scale fins.
Thanks for the progress reports... really like the 'how to' on the scale fins.
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