The Double Arcas

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UPscaler

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The Anti Gravity Group is at it again.

This time, we thought it would be fun to upscale a full-scale rocket. So, we proudly present The Double Arcas.

9.25" in diameter, 15 feet tall. 98mm in the middle, four 54s, and four 38s. The seven motors in the 12" Punisher just didn't seem wild enough šŸ˜œ

Like last time, @tjsnakez cut all the pieces and myself and Shane (@PosTart , as he goes by around these parts), and Matt are here to slam it together.

Step one is the nosecone. We wanted a proper scale one, so we decided to do it ourselves. Taylor made up a fancy jig and a combination of hot wire cutting and sanding netted us a pretty solid result!

Up next is glassing it!

There will be videos of this build coming out on my YouTube channel, too!

Stay tuned!


Braden
 

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For the hot wire, do you just connect it to a car battery charger or something?

Came out pretty darn good looking.
 
Here are some better pictures of the nosecone jig. I used two 1/2ā€ shaft bearings to hold the 1/2ā€ all thread. This allowed us to spin it in place while remaining aligned with the nose profile guide. After we got it to a rough shape with the hot wire cutter, we threw the all thread in the big Milwaukee drill and spun it like a hillbilly lathe to turn the high spots down!

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Here are some better pictures of the nosecone jig. I used two 1/2ā€ shaft bearings to hold the 1/2ā€ all thread. This allowed us to spin it in place while remaining aligned with the nose profile guide. After we got it to a rough shape with the hot wire cutter, we threw the all thread in the big Milwaukee drill and spun it like a hillbilly lathe to turn the high spots down!

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Whose tubing and couplers are you using?
 
Whose tubing and couplers are you using?
They're from Ken at Performance Hobbies!

Joe Hill was nice enough to meet Taylor halfway on delivery while he was on the east coast. Which is great, because we can't imagine the cost of shipping two 9"x6 foot tubes.

Braden
 
More glass, more glass!

Fins: glassed
Airframes: glassed (and heat shrinked. Heat shrunk? Heat shrunked.)
Nosecone: Glassed

Here comes the sanding, folks.

Braden
 

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Up next is fiberglassing these big giant airframes. It was a bit daunting of a task, but the soller sleeves really helped the process move along. The heat shrink tape, on the other hand, was tedious.

After a quart or so of epoxy, the tubes are looking pretty good, aside from the parts the heat shrink didn't reach. So far, the tubes only weigh 9 pounds each...which is a bit concerning for the finish weight. If it stays lighter than we are thinking, we're going to have to pull back on the motors a bit.


Braden

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Gatling gun mode engaged!
We built the motor mount assembly and slid it into the airframe to glue the fins in without the outboard tubes.

This allowed us to add internal fillets to the fins, then glue the motor tubes in, and proceed to add internal fillets to the fin/motor tube joints as well.

Next up is gluing the whole shebang in and getting to external fillets.

Braden
 

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Did you guys fly it yet


We really slacked on keeping this thread updated. Sorry folks! It was a busy busy week followed immediately by moving from Idaho to California.

The Double Arcas will be making its second flight at AIRFest 30 on an Animal Motor Works N2800 Skidmark demo motor, assuming sparkies are allowed. Keep your eyes on this thread for @tjsnakez 's nosecone V2 build.
 
Ok, dat wuz purty nice! šŸ˜²

Now, I've heard that the common wisdom is that you don't cluster composite motors. Yet here goes not 2 or 3, bu NINE BIG composite motors at once. This little lowly L0 guy wants to know a few things about how to make this possible,a s I am tryung to recreate a model from my childhood (that never flew), and the specific impulse available from composites vs. black powder is hard to pass up. I'd assume that my car battery-powered system should provide the amps needed, and you'd want to be as uniform and correct with your starters (igniters, initiatiors) placements as possible, but do you guys use anything special to ensure you light this many motors within the few hundredths of a second needed to pull this off? I'd appreciate any wisdom that you could impart!
 
Ok, dat wuz purty nice! šŸ˜²

Now, I've heard that the common wisdom is that you don't cluster composite motors. Yet here goes not 2 or 3, bu NINE BIG composite motors at once. This little lowly L0 guy wants to know a few things about how to make this possible,a s I am tryung to recreate a model from my childhood (that never flew), and the specific impulse available from composites vs. black powder is hard to pass up. I'd assume that my car battery-powered system should provide the amps needed, and you'd want to be as uniform and correct with your starters (igniters, initiatiors) placements as possible, but do you guys use anything special to ensure you light this many motors within the few hundredths of a second needed to pull this off? I'd appreciate any wisdom that you could impart!
The 8 outboard motors used e-matches with pyrodex pellets in the top of them to light them. The N in the middle used Copper Thermite, but that is not a compound you want to mess with if you're not familiar with safe pyro mixing and handling practices. I always recommend folks use Procast from Quickburst, as it's a BKNO3 compound with a binder that makes dipping e-matches into it simple. I used it for my M and four J flight in my Honest John, and it brought a moonburner M motor up nearly instantly.

You'll want to use low-resistance igniters when clustering. All of our clusters are lit with e-matches.
 
The 8 outboard motors used e-matches with pyrodex pellets in the top of them to light them. The N in the middle used Copper Thermite, but that is not a compound you want to mess with if you're not familiar with safe pyro mixing and handling practices. I always recommend folks use Procast from Quickburst, as it's a BKNO3 compound with a binder that makes dipping e-matches into it simple. I used it for my M and four J flight in my Honest John, and it brought a moonburner M motor up nearly instantly.

You'll want to use low-resistance igniters when clustering. All of our clusters are lit with e-matches.
Very much thanks! I'll have to get some e-matches and try them out. Do you wire in parallel? I've heard of people using series setups, so i thought I'd ask. If in parallel, do you use a common ground or pairs of leads back to common mains?

Again, much thanks for your help!
 
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