Plasma Dart II Upscale (a neil_w design)

[neil_w]

OK, in hindsight, here's how to prevent this, and what should be done when the design is made into a kit.

Make the rings at the ends of the cage with holes precisely positioned for the bars. The holes should be drilled with the two rings stacked, or cut with a CNC machine (router, laser, or otherwise). Add very short dowels to fill the holes and stand just a little proud; the proud portion is like the disks Marten glued on but with the positioning forced. Glue one ring in place. Once that glue is cured, place the bars and the other ring in place with a glue that gives a little time for positioning. Rotate the second ring so that the bars are are square, then leave it for all that to cure.

I think having precision-drilled rings with the short dowel pieces is a very good idea. If building at a small scale, the small dowel pieces could be used to support launch lugs as the cage pieces, in the style Martin used.

You don't generally want to permanently attach all the cage pieces at the same time you're gluing the rings, though, because that will make finishing the core very difficult. If they are mounted like Martin's, then one could just temporarily rest on there.

Or an alignment mark on the inner diameter of the rings could be aligned to a straight line on the BT. That's actually fairly reliable, if the marks one the rings are made with the laser cutter (or at least more accurately placed than mine were. )

If I built it again (as always, I won't) I'd try this method.

And Bob's your uncle. (Where the hell does that saying come from? What has some guy named Bob have to do with it?)

https://en.wikipedia.org/wiki/Bob's_your_uncle

 

[mbeels]

OK, in hindsight, here's how to prevent this, and what should be done when the design is made into a kit.

Make the rings at the ends of the cage with holes precisely positioned for the bars. The holes should be drilled with the two rings stacked, or cut with a CNC machine (router, laser, or otherwise). Add very short dowels to fill the holes and stand just a little proud; the proud portion is like the disks Marten glued on but with the positioning forced. Glue one ring in place. Once that glue is cured, place the bars and the other ring in place with a glue that gives a little time for positioning. Rotate the second ring so that the bars are are square, then leave it for all that to cure. And Bob's your uncle. (Where the hell does that saying come from? What has some guy named Bob have to do with it?)

I think having precision-drilled rings with the short dowel pieces is a very good idea. If building at a small scale, the small dowel pieces could be used to support launch lugs as the cage pieces, in the style Martin used.

You don't generally want to permanently attach all the cage pieces at the same time you're gluing the rings, though, because that will make finishing the core very difficult. If they are mounted like Martin's, then one could just temporarily rest on there.

I had an idea to combine these two good ideas (non-mounted cage pieces, and laser cut holes in rings to force positioning).

It starts to get complicated though, it involves 1/4" holes in the rings (for alignment and launch lugs), 1/4" dowels for alignment, and centering rings with 1/4" ID and and OD suitable for BT-5 tubing. It would still require notched cage pieces to attach after the finishing, but could utilize dowels for alignment.

Probably the precision 1/4" holes, in addition to laser marks, and a properly marked body tube would have fixed the positioning errors I made.

"and Nellie's your aunt"

 

[BABAR]

Why not just build the thing without the cage pieces. Don't paint it yet.

Make an open circle template (with slice across it, so you can put it around the warp core on forward surface of the REAR transition) with your 6 or 8 evenly space holes. Mark the holes.

Now dry fit your cage pieces, line up aft with your marks, eyeballed straight, and mark the corresponding sites on the aft surface of the FORWARD transition. Remove the cage pieces.

Now put small rounded pieces of tape over all your marks.

Paint the rocket and apply your warp core decal.

Paint your cage pieces, sparing the tips which need to be glued.

Pull the tape pieces off your marks.

Glue in your cage pieces.

Touch up the glued areas with black paint. Another easy touch up is with a black sharpie pen. Alternative is to add black dye to your glue, but Lord save you if you get glue in the wrong place!

 

[neil_w]

That is closer to what I did, but still screwed it up, at least partially due to an incorrect template. (we really need the old facepalm emoji back)

 

[mbeels]

Oh man, I think that this is my favorite part of a build, getting the envelope from Stickershock23.com and applying the vinyl. Mark does fantastic work, and he is super accommodating. Can't recommend him enough.

 

[BABAR]

Very, VERY, nice!

 

[kuririn]

Oh man, I think that this is my favorite part of a build, getting the envelope from Stickershock23.com and applying the vinyl. Mark does fantastic work, and he is super accommodating. Can't recommend him enough.

View attachment 392554

That is the proverbial crowning touch. Nice work.

 

[mbeels]

Well, you what they say, the thread isn't over until the fat lady gets her canards. Or something like that.

I'm aiming to get them done and the rocket setup for dual deploy by the Nov 16-17 MDRA launch.

 

[mbeels]

Rustoleum 2x Gloss White is on the canards, AV bay is built with an Eggtimer Quark, and motor is loaded with a G25. The weight came in under 22 oz, so I think it will be fine with the G25 as long as it isn't super windy this Saturday. The nearly 5 second burn should be fun.

Yay, I got one of the Apollo cases:

 

[BABAR]

Hoping for light winds, a straight trail, a soft landing, and a short walk!

 

[Nytrunner]

~6.5 T/w at the start of that burn. Has a good regressive long-burn profile

Should work, judge wind accordingly

 

[mbeels]

Hoping for light winds, a straight trail, a soft landing, and a short walk!

Thanks! Me to.

~6.5 T/w at the start of that burn. Has a good regressive long-burn profile

Should work, judge wind accordingly

Yeah, it's a nice thrust curve. If it's really windy, I'll use an F67.

 

[mbeels]

Well, way too windy for the G25. I launched a G77 Redline which was a nice boost. I didn't allow sufficient space for recovery and so I attempted to borrow some room inside the nose cone, and that didn't work. My error, I'll reconfigure the recovery gear.



It's repairable, but it will be a bit tricky to make it both structurally sound, and straight.

 

[Nytrunner]

Guess all you can really do is turn it into a PD 1

 

[mbeels]

Guess all you can really do is turn it into a PD 1

Or squish it a bit more and make two gooney plasma darts.

 

[neil_w]

That's pretty weird, seems like a very clean break with almost no collateral damage fore or aft. Seems like it *should* be repairable, but I confess I'm not sure how to do it.

Here's my one idea, dunno how practical but see what you think.

1) Cut away what remains of the transition, and the shredded BT80.
2) Insert a long piece of coupler into the upper half.
3) sand down the upper centering ring on the MMT so it'll fit inside the coupler.
4) Extend the coupler as far into the fin can as it'll go. I don't recall where the next centering ring is...

If the coupler can extend a decent way into the fin can, that should keep the whole thing straight and rigid.

Oh , and of course at some point you need to slide on the new transition before gluing it all up.

 

[mbeels]

That's pretty weird, seems like a very clean break with almost no collateral damage fore or aft. Seems like it *should* be repairable, but I confess I'm not sure how to do it.

Me neither.

Based on the dirt on the motor retaining ring, I think it hit while rotating and the motor bore most of the impact. So it broke sort of like dropping a piece of chalk from 30cm, or a falling chimney breaks 1/3 of the way up. Or mainly it just whacked the dirt pretty hard.

I think that's a good ideal, Neil. I was thinking some similar, with two separate couplers on either side of the centering ring, and a new section of BT-80. But I like your idea of one longer centering ring for strength. It would a continuity through the broken area.

I might also try fiberglassing something, since I have cloth and finishing resin left over. It doesn't show in the picture well, but that exposed centering ring is split. It may need to be replaced. I happen to have two extra 1/4" 38mm to BT-80 centering rings that I ordered by accident.

I'm also considering changing the split location to just in front of the forward shroud, similar to what you did with the PDI.

I need to stare at it a bit longer.....

 

[neil_w]

Good luck sir.

 

[BABAR]

Me neither.

Based on the dirt on the motor retaining ring, I think it hit while rotating and the motor bore most of the impact. So it broke sort of like dropping a piece of chalk from 30cm, or a falling chimney breaks 1/3 of the way up. Or mainly it just whacked the dirt pretty hard.

.....

I was thinking the Dilithium delaminated which blew the warp core and disrupted the plasma field (aka FTI, "Fecal Turbine Interaction"), but I think your explanation is more plausible.

Hope you can get her back in the air!

 

[mbeels]

Well, after staring at it for a while, I ended up doing almost exactly what neil_w suggested, and it was easier than I thought. Now, the harder part will be the shroud and restoring the finish and cosmetics.

First I cut away the heavily damaged tube sections, and removed the torn shroud completely. I then:
1) Added a new 1/4" BT-80 to 38mm centering ring low on the motor mount
2) inserted a BT-80 coupler
3) inserted a second BT-80 to 38mm centering ring, cut down to fit inside the BT-80 coupler
4) slid the two parts together
5) And because the joint will be covered in the shroud anyway, I slit a short section of BT-80 and wrapped the outside of the joint with it.

It does look like this was a clear weak section of the rocket, it was an unsupported section of BT-80. The rest of the rocket has the benefit of interior centering rings and tubes, or the exterior plasma cage.





The yellow lines designate new 1/4" centering rings, and the blue lines show how far the motor mount tube extends. This new section of coupler will tie together the strongest elements of the rear part of the rocket, with the front part.

I also cut away the damaged plasma tube.



All together once again. This should be quite a bit stronger then it was before. I then wrapped it with a section of BT-80.



A side benefit of cutting away part of the plasma tube is that it may make inserting the new shroud a bit easier. The cosmetics will be hard!

 

[mbeels]

All things considered, this repair is going much easier than I expected. Wrecks always look so much worse at first glance. I owe another huge thanks to @neil_w for the templates from the shroud and warp tube templates. They greatly simplified this process! A new shroud is in place (Rice Crispies again, coincidentally) although I'm going to try the unfinished side out this time. I hope to get better glue joints and fillets with the warp tubes. I'm also hiding the seam.

 

[neil_w]

Looks great... I didn't realize you were going to lose some warp tube, but that should patch in reasonably well I think.

 

[mbeels]

fill, sand ... sand ... sand ... fill, sand ... sand ... sand ... fill, sand ... sand ... sand ... fill, sand ... sand ... sand ... fill, sand ... sand ... sand ... fill, sand ... sand ... sand ...

 

[kuririn]

Heh, you forgot to add the ...sneeze... in there.

 

[jqavins]

I'm going to write the next great novel about model and HP rocketry, and the protagonist will be named Phil Sand.

 

[BABAR]

I'm going to write the next great novel about model and HP rocketry, and the protagonist will be named Phil Sand.

Ode de Black Powder. (Little French play on words there!)

 

[kuririn]

I'm going to write the next great novel about model and HP rocketry, and the protagonist will be named Phil Sand.

Instead of a novel, how about a primer, with the protagonist named Phil Sand Wykoff?

 

[BABAR]

Instead of a novel, how about a primer, with the protagonist named Phil Sand Wykoff?

When they make the movie, he can be play by StickyFingaz

 

[mbeels]

It could take place in Sandalot, and the knights of the 220 grit.

 

[dhbarr]

It could take place in Sandalot, and the knights of the 220 grit.

On second thought, 'tis a scratchy place.