12” Mega Punisher Build Thread

[Rocketjunkie]

You might want to try the thinned Bondo to fill the weave of the T-T glass. I used it on the Deuce98 for this and the glassed paper body tube. https://www.rocketryforum.com/threads/bigger-deuce.47449/page-3 starting at post #83.

 

[mtnmanak]

No arguing that CNC is the way to go for precision, but it’s way out of our budget. It took me a couple hours to make all the wood parts, so not really a big deal. And the fit is great on everything.

Definitely get it on the cost of a CNC machine, it isn't exactly cheap. When you put it in perspective, though, you can get a very excellent Shapeoko 4 for less than the cost of the parts of this rocket and less than a single flight if you load up all the tubes. Once I got into rockets of this size, I figured that if it is going to cost somewhere north of $1500 to build a rocket and then another $2000 per flight to fly it, $1700 for a good CNC is not out of the question anymore.

Good luck with your build and flight - wish I could be out there to see it!

 

[AstroAbaqus]

Fins are in place, internal fillets are done and the fin can tube is glued in place. Next is fillets, then we're doing a layer of tip to tip fiberglass to really cement things in place.

Here's a fun picture of the Cert 3 XL that we're using as a drogue just because it's absurd that a chute this big is a drogue.

Braden

I dont know Branden, but I guess that nosecone cost as all my entire build xD. Amazing project! Are you all going to do a video out of this? Would take a flight to US just to see it or ear it

 

[UPscaler]

You might want to try the thinned Bondo to fill the weave of the T-T glass. I used it on the Deuce98 for this and the glassed paper body tube. https://www.rocketryforum.com/threads/bigger-deuce.47449/page-3 starting at post #83.

I was trying to remember who I had seen thin some Bondo when I was considering doing it on my 7.5" Iris, so I'm glad you popped in! I used this same glass on the Iris tubes and it definitely leaves a good bit of sanding to be done in the end. It's beefy, though!

I dont know Branden, but I guess that nosecone cost as all my entire build xD. Amazing project! Are you all going to do a video out of this? Would take a flight to US just to see it or ear it

Yes, this build is entirely documented. So far I've already racked up about 100 gigabytes of footage. It's going to be a bit before I can get it all edited and ready to go!

Braden

 

[Williamhimka]

Wow - really coming together fast! What tubing are you using for the airframe?

Phenolic fiberglassed it seems

 

[C.O.B.H.C.]

Are the outboard 75mm motor tubes just held in with epoxy? Or are you going to have an aft aluminum thrust plate?

 

[UPscaler]

Nothing too extreme for the day.

Both remaining fin sections got their tip to tip treatment which, unfortunately, means we're about to ender the sanding stage.

However, next on the docket is also figuring out all of the hardware and, of course, ground testing.



Braden

 

[UPscaler]

In our quest to make perfect trifecta fins (cheap, light, and strong), there's a bit of a learning curve. We weren't quite sure if we needed to add any more composite but didn't want to do a whole second layer of tip-to-tip glass for weight reasons.

For a little bit of extra peace of mind that adds less than two pounds overall (before sanding), we added more carbon atop the glass using the foam core shape as a template to ensure the structure around the foam is plenty beefy.

Overall, the addition of tip-to-tip glass and these carbon bits added only about 3.6 pounds. Every bit counts when you've got seven motors tubes to fill!

Now, they're feeling pretty dang beefy and the entire fin can assembly comes in under 40 pounds as it sits. That's not too bad considering there's nearly two quarts of West Systems epoxy, tons of hardware, and half a tree worth of plywood in/on it.

Braden

 

[Adam3836]

Impressive just down right impressive
That thing is gonna roar lol

 

[cwbullet]

I have to concur. This is one beautiful build project.

 

[Neutronium95]

Now, they're feeling pretty dang beefy and the entire fin can assembly comes in under 40 pounds as it sits. That's not too bad considering there's nearly two quarts of West Systems epoxy, tons of hardware, and half a tree worth of plywood in/on it.

I'm glad you're keeping the weight in check. The Gates Brothers rockets are absolute tanks that could stand to lose a lot of weight. They used tons of centering rings, ran threaded rods through the motor mount assembly and then entombed the whole thing in a boatload of fiberglass. Your approach is pretty much how I'd want to build a rocket of this size.

 

[UPscaler]

I'm glad you're keeping the weight in check. The Gates Brothers rockets are absolute tanks that could stand to lose a lot of weight. They used tons of centering rings, ran threaded rods through the motor mount assembly and then entombed the whole thing in a boatload of fiberglass. Your approach is pretty much how I'd want to build a rocket of this size.

Our primary concern is trying to avoid nose weight if we can. Porthos doesn't have any, but the 75mm motors will likely make a fairly substantial difference in tail weight.

Ultimately, a lot of the choices we made have substantial Gates Brothers influence, we just didn't do it quite as hardcore. No tip to tip fiberglass matte here.

Braden

 

[tjsnakez]

We are learning a lot as we go on our first mega project. Overall I’m happy with the construction of everything so far. Next time we will start with the same fin construction and go straight to 3 layers of carbon.

 

[UPscaler]

Some finishing touches included adding six weld nut backed #10 screws to each of the two sections that will remain attached throughout the flight.

Last night we were planning a ground test but after some semantics it wound up getting a little late. So, the charges are ready for a ground test this evening. The PVC caps we're using are hilariously large.

As a bonus, there's a picture of my night flying RC plane in there for good measure. That's what we did instead since it's a little less concerning for neighbors.

Braden

 

[DAllen]

Made a lot of progress today!
View attachment 523601

LAWDY HATH MERTHY

 

[Neutronium95]

What kind of paint job are you planning on doing on this thing?

 

[jmasterj]

Late question, but is the nose cone from Composite Warehouse?

 

[g.pitts]

Just for giggles, what did your black powder charge sizes end up being for the drogue (primary and backup) and main parachutes (primary and backup)?

 

[tjsnakez]

Just for giggles, what did your black powder charge sizes end up being for the drogue (primary and backup) and main parachutes (primary and backup)?

15 grams for the drouge and 18 grams for the main!

 

[rfjustin]

15 grams for the drouge and 18 grams for the main!

When you ground test, I think you may find that much BP is excessive, even for a 12" airframe. I've got old videos in my vault of some 12" ground testing with comparable charge sizes and it was WAY too much.

YMMV, looking forward to seeing the ground test videos.

 

[tjsnakez]

When you ground test, I think you may find that much BP is excessive, even for a 12" airframe. I've got old videos in my vault of some 12" ground testing with comparable charge sizes and it was WAY too much.

YMMV, looking forward to seeing the ground test videos.

It ended up being spot on! We were definitely nervous about it being too much though haha

I think Braden got some good video of it too!

 

[The_Quacken]

I am soooo excited to see video of this build especially after following this thread

 

[UPscaler]

Here's @tjsnakez on the ladder drilling shear pin holes (standing to ensure the tube and NC were seated properly as they would be for flight).

Here's the fincan covered in frosting (epoxy with microballoons) to smooth things out!


Braden

 

[Hobie1dog]

I can't believe you can afford that many motors.

 

[tjsnakez]

I can't believe you can afford that many motors.

We’d like to thank our sponsors chase Morgan, capital one, and being single without kids

 

[Theory]

That last one…. Yup, that last sponsor FTW!

 

[TheTank]

We’d like to thank our sponsors chase Morgan, capital one, and being single without kids

The last one… 100% accurate. While I could afford buying all the motors for that one flight… it would be divorce court and child support that would be costly. The one flight part would not sit well with the boss.

 

[Theory]

I’m lucky that my other half approves of this hobby/obsession

 

[Tim51]

I’m lucky that my other half approves of this hobby/obsession

Yep, same here. I recall a few years ago asking my wife if she thought the whole rocketry thing was a bit mad. She just put her hand to my cheek and said 'It makes you happy'. Nuff said.
However, I think were I ever to undertake a project anything like this (and the 'like' bit is obviously academic atm since I'm L2, not L3) I'd feel more comfortable doing it the way these lads are - ie as a collaborative group engineering challenge rather than a solo job. Apart from the cost sharing it must be great bouncing ideas and trouble shooting as a team. More power to them.

 

[AfterBurners]

Here's @tjsnakez on the ladder drilling shear pin holes (standing to ensure the tube and NC were seated properly as they would be for flight).

Here's the fincan covered in frosting (epoxy with microballoons) to smooth things out!


Braden

Looks like you're gonna need a bigger truck