BA Baracus Build Thread

[Barkley]

Haven't done a build thread in a while, but a skilled buddy of mine is in town, and a discussion over a few beer led to a plan for a full carbon, scratch built, M capable 77mm min diameter rocket. Plan is to build it now, test it with a K at an URRG launch in the spring, then maybe visit Argonia later in 2017. Looking at different high temp laminating epoxies at the moment, and already have the 2x2.

This weekend could be fun.

 

[ChrisAttebery]

Cool project name. It needs to be flat black with a red stripe.

 

[Bat-mite]

I pity the fool who tries to beat this rocket! :wink:

 

[mpitfield]

You will have to remove all of the gold chains from around the rocket if you plan on flying in Algoma, or just paint them :wink:

Looking forward to the build thread, have you given much thought to the recovery system? It looks like a single split design?

 

[Barkley]

Looking forward to the build thread, have you given much thought to the recovery system? It looks like a single split design?

Confirmed single split. NC sled, charge on the NC lid. Thoughts were to use a ring on the motor case and my JL chute release. Still working on how to get telemetry out of the carbon, but I suspect I may follow Jim's lead.

 

[Barkley]

PTM&W PR2846 laminating epoxy chosen, which has great heat tolerance but a complicated post cure (4 hours at 150F, then 4 at 250, 4 at 350, then 4 at 425). Big thanks to JP at Composites Canada for not only having this stuff in stock, but also finding another customer who uses this stuff who'll let me use their oven. Truly above and beyond.

When I did my last build thread (https://www.rocketryforum.com/showt...-Scratch-Build-Thread&highlight=flying+moomoo) I tried an unconventional method for making the nose cone. I'm doing this one the right way, so now I need a lathe big enough to make the mold blank. The one I had in mind isn't big enough...

 

[REK]

I'll be watching


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[Barkley]

Mandrel purchased. Disappointed that all the 3" stock wasn't quite 3", but 2.996 with Mylar film will work. Was hoping to not need the Mylar this time.

 

[REK]

Mandrel purchased. Disappointed that all the 3" stock wasn't quite 3", but 2.996 with Mylar film will work. Was hoping to not need the Mylar this time.

Apply this to your mandrel, it will add 0.01" to your mandrel. Not only that, but it will make it easier for you to remove the cured tube. Trust me the mylar will make it difficult to remove after that complex cure schedule.

Cut to overlap and then cut the section that overlaps. After that if there is any metal showing where you cut the overlap, apply wax paste. Finally give the whole thing a coat of baby oil to give the cured part easy removal.

I do this all the time with my tubing.

https://compositeenvisions.com/non-...49-25-1250mm-width-thickness-0-11mm-1802.html


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[mpitfield]

Hey Chris,

You're inspiring me to abandon off the shelf CF tubing for my L3 and give "roll your own" a try. Are you planning on applying any compression to reduce the epoxy and make the layup any tighter? If so what methods are you considering?

 

[Barkley]

Good fun yesterday. Some changes to the design spec, as I'd like to eventually like to use this as the top of a 2 stage. Now 4 fin, traditional dual deploy.

Here's the mandrel getting cut:

 

[Barkley]

PTM&W. An eye opening experience:

West system has a viscosity of 975. This stuff has a viscosity of 7000. It's like using molasses for a layup.

Normally you transfer the resin into a detergent bottle to make things easier to pour and to keep your shop clean. This was a still shot, but it may have been a video as the stuff just wasn't moving. We had to hit it with a heat gun to get it to flow:

 

[Barkley]

Hey Chris,

You're inspiring me to abandon off the shelf CF tubing for my L3 and give "roll your own" a try. Are you planning on applying any compression to reduce the epoxy and make the layup any tighter? If so what methods are you considering?

Michael,
Your project is aggressive - I don't know where you'd be sourcing your commercial tube, but if it isn't made with a high temp epoxy odds are good it'll melt. I used a Loki M to sim this project and it took it over mach 3, so that's part of why I'm using the epoxy I chose. Rolling your own really isn't that hard, but I'm glad I did as much fiberglass work as I did to get the process down. The rest of the process will follow - working with Keith has been an eye opening experience, as he's a pro boatbuilder on boats with load that will be much higher than we'll see.

 

[Barkley]

Shrink tape in the middle, vac bag tape on the right.

 

[Barkley]

Inside: Freekote spray mold release. The best. Outside: snow. No question I'm back in Canada.

 

[Barkley]

2x2 twill, on the roll. Turns out the width of the roll was exactly 5 wraps of the mandrel - awesome sauce.

One pro lesson learned. I'd always laid out the carbon on a cutting mat and used a rotary wheel cutter. The new way is to pull out 3 individual strands of carbon (or FG if that's what you're using), then that's your cutting guide. For certain I'll be doing this from now on:

 

[REK]

Shrink tape in the middle, vac bag tape on the right.

So are you going to shrink tape it and then vacumn bag it? I think the shrink tape is more than enough.


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[Barkley]

So are you going to shrink tape it and then vacumn bag it? I think the shrink tape is more than enough.


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Belt and suspenders. It's worth it. More pics soon.

 

[REK]

Belt and suspenders. It's worth it. More pics soon.

As long as it works


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[Barkley]

So.. this is a high class low brow layup. Here is what's holding up the tube in the shop:

Edit to say, you can clearly see the mandrel and the mylar.

 

[Barkley]

So... we laid up the whole bit with the good stuff, leaving a bit without so it could soak up from below:

After this bit I was gloved up, so no pics.

 

[Barkley]

More to come, but here is the tube before vacuum:

Taped peel ply, which results in 6 bar of pressure, three wraps then a bit of a pull..... then repeat. Then shrink wrap, which is the same. Then hit it with the heat gun to squeeze it. then.... the vac bag.

 

[Barkley]

Applying the breather fabric:

 

[mpitfield]

Looking Good Chris, man you are like a machine when you get into something. My builds take so much time because I can't give more than an hour, more like 30 min at a time. I am just finishing my GLR Mariah 38 after two years. That's one rocket close to making it off the bench and a couple dozen left to get through.

If you end up with ridges from the shrink tape are you planning on attempting to sand them out? BTW I know you have worked with FG, but have you ever sanded CF before, if not wear gloves and a mask, that stuff gets right into your pores.

 

[Barkley]

Draping the rest of the breather fabric:

Then in the bag:

 

[Barkley]

Heat gun down the middle of the mandrel, for two reasons. First, it expands the alloy just a hair, which makes everything pop off a little easier when it cools, and second it helps to kick the epoxy.

Supposedly full vacuum is 29 on this gauge, so 28 is damned good:

And here's the proof that the belt and suspenders technique works. The wet spots in the breather proves the vacuum has pulled some of the epoxy right through the shrink tape.

 

[blackbrandt]

Whoah! Epic! I'll be watching this one carefully.

 

[Barkley]

Looking Good Chris, man you are like a machine when you get into something. My builds take so much time because I can't give more than an hour, more like 30 min at a time. I am just finishing my GLR Mariah 38 after two years. That's one rocket close to making it off the bench and a couple dozen left to get through.

If you end up with ridges from the shrink tape are you planning on attempting to sand them out? BTW I know you have worked with FG, but have you ever sanded CF before, if not wear gloves and a mask, that stuff gets right into your pores.

Yes, this will be sanded to a polished finish. I want it to look pretty when I'm done.

The intent of this was to be a single stage, but I changed to spec a bit to leave the option of putting a booster under it:

Single break from REALLY high probably isn't the best idea, so I went with a more traditional dual deploy setup. Turns out it got me a bit more height than the original design. That's with a Loki M, but still sims well with a K.

Edit to add: If anyone has any recommendations or thinks there's a way to improve this, I'm all ears.

 

[BDB]

Yes, this will be sanded to a polished finish. I want it to look pretty when I'm done.

The intent of this was to be a single stage, but I changed to spec a bit to leave the option of putting a booster under it:

Single break from REALLY high probably isn't the best idea, so I went with a more traditional dual deploy setup. Turns out it got me a bit more height than the original design. That's with a Loki M, but still sims well with a K.

Edit to add: If anyone has any recommendations or thinks there's a way to improve this, I'm all ears.

This looks awesome! Did you leave the case hanging out of the back by ~ 1 caliber to use as a coupler for eventual staging? What are your plans for motor retention?

 

[Barkley]

This looks awesome! Did you leave the case hanging out of the back by ~ 1 caliber to use as a coupler for eventual staging? What are your plans for motor retention?

Re 1.5 calibers, I'm leaving the door open for possible staging, but that's not the plan at the moment. Re motor retention, was thinking about a ring in the forward bulkhead.