Build thread: Plasma Dart

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Hey, should base drag correction apply here? It would seem that, if the base drag correction formula is correct, it should apply to every rocket, and give a bit of a stability boost. In this case, the tail is BT70, which is quite a bit of base drag and has a large effect on CP:
1600219822776.png 1600219794437.png
Slight adjustment was made to account for the .5" extension of the core tube.

Anyway, that's a 2.3" move of CP, enough to add a whole caliber of stability. Even if it's only half correct, it's still enough to change the rocket from "marginally stable", to "comfortably stable". In which case I can stop worrying about additional nose weight.
 
It looks.... like the OR render. Surprise!

I'm used to your usual build-up of suspense, not revealing the rocket in its entirety until it is completely finished, but I like this fully assembled progress shot! I'll be really curious to see how the paint and finishing goes with this one.
 
I'm used to your usual build-up of suspense, not revealing the rocket in its entirety until it is completely finished, but I like this fully assembled progress shot!
I debated but decided to do it. 🤷‍♂️

One day I'm going to do a mystery build thread without showing the design ahead of time. But that would require me to finalize all the details of a design without showing anyone beforehand, which seems.... well, a bit far-fetched, knowing myself. :)
 
LAUNCH LUG

Part of the exquisite craftsmanship of my rocket builds is that I usually remember to mount the launch lug before I paint.

Based on TVM's old article about launch lug shapes, I decided to bevel the front edge and leave the back square. Position-wise, I would ideally want it as forward as possible on the fin can to get close to the CG, but I moved it back a bit to look better, since I have the supplemental loop at the front.

I use a launch rod to ensure alignment.
Lug-1.jpg
Frankly, I'm convinced I could do it just as well by eye, but whatever.

As is my custom, first a TBII fillet goes in to fill the joint. It looks so nice when wet...
Lug fillet wet.jpg
...and such a bubbly mess when dry.
Lug fillets-1.jpg
That is why we always finish with TBQ&T.
Lug fillets-2.jpg
Because the TBQ&T is completely clear, it actually looks just as bad when dry, and I usually run my fingers over it just to convince myself that it really is smooth.

Le finished lug:
Lug-2.jpg

Now that is some quality build thread content right there. 👍
 
Fillets are finished. State of the rocket:
View attachment 431578
It looks.... like the OR render. Surprise!

I guess I should figure out what I'm going to do with the tail now. 🤷‍♂️
Actually it looks exactly the opposite of the OR rendering, but that’s just a technicality, sort of like distinction between average and median......;)
 
As is my custom, first a TBII fillet goes in to fill the joint. It looks so nice when wet...
View attachment 432001
...and such a bubbly mess when dry.
View attachment 432002
I find this condition can be improved upon. Wait about ten or 15 minutes after application. That's brief enough that the glue can still flow, but long enough for bubbles to float to the surface. Then pop the bubbles with a pin.
Actually it looks exactly the opposite of the OR rendering, but that’s just a technicality, sort of like distinction between average and median.
Far less of a difference than that, since "average" is an ill-defined term which can be the same as median, but is more often the arithmetic mean, and that's not the same at all.
 
I find this condition can be improved upon. Wait about ten or 15 minutes after application. That's brief enough that the glue can still flow, but long enough for bubbles to float to the surface. Then pop the bubbles with a pin.
For launch lug fillets I find the bubbles appear later in the drying process. If I happen to see them I pop them, but generally I can't be bothered to try to monitor them while drying, especially since it's so easy to fix the problem with a single layer of Quick and Thick.
 
NOZZLE BITS, PART 1

I decided to stick with the original design for the tail:
1600730500246.png
Some of the other alternatives looked good too, but none of them were (IMHO) clearly *better*.

I cut out a bunch of little pieces:
1600730625811.png
Each one needed to be (annoyingly) sanded to fit, something like this:
1600730683118.png
Every fiber of my being wants to reach into that picture and wipe away all the sanding dust. No can do!

Final picture for the day:
1600730787494.png
*Of course* I am papering these guys. One down, five to go.
 
One thing I like to do to spice up my fins is take a paint marker and run it just along the edge of the fin. Something like that could give you the extra pizzazz you're looking for on those vents
 
Some of the other alternatives looked good too, but none of them were (IMHO) clearly *better*.
And your HO is the only one that counts. (Yeah, OK, but you know what I mean.)
One thing I like to do to spice up my fins is take a paint marker and run it just along the edge of the fin. Something like that could give you the extra pizzazz you're looking for on those vents
And if you pick tiny red, white, and brown circles they could give the extra pizzas too.

Alright, I'll stop now. For a while. Probably a little while.
 
One thing I like to do to spice up my fins is take a paint marker and run it just along the edge of the fin. Something like that could give you the extra pizzazz you're looking for on those vents
I thought that would be great, but when I previewed it in OR I really didn't like it, which honestly surprised me. I can still decide on something for that up until the last minute, but if I were to go with it as shown in the pic I'd be satisfied.
And if you pick tiny red, white, and brown circles they could give the extra pizzas too.
This is quite amusing to me because just a couple of days ago my daughter was working on an art homework project in which she misspelled the word as "pizzaz". As soon as I pointed it out, she commented that it looked like "pizzas".

 
I cannot figure what you did there on line two. Explanation?

I sort of imagine a very long ruler and look at the distances.

I think there comes a time when seeing "7" brings to mind "3" (because 10-7=3)
And seeing "54" brings to mind "46", because 100-54=46.

So for any number between 0 and 100, I almost immediately see what's missing to make 100.
Ex. you give me "29", I'll get you "71" immediately.
Ex. you give me "63", I'll get you "37" immediately.

So when I see:
"342 - 173"

I see the "42" easily.
I see the "100" that separates 200 and 300.
I see the "27" that's missing for 173 to reach the next hundred (200).

So then I add 42 + 100 + 27.
 
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NOZZLE BITS, PART 2

Six parts, all papered and sanded to fit:
Nozzle bits continued-2.jpg
Getting things like this lined up exactly tends to be a pain, so I printed out a template and glued it to the back of the centering ring. This served to paper the ring as well, which should improve the finish a bit (not that that's a particularly important area).
Nozzle bits continued-1.jpg
Even with the alignment marks, getting each piece in the right position and straight was frustratingly difficult. Eventually I got what I think is a decent result:
Nozzle bits continued-3.jpg
I'm happy with the appearance, which, again, looks like the render, but it's always reassuring to see it IRL:
Nozzle bits continued-4.jpg
I have a bunch of highly finicky filleting to do back there, but other than that construction is now complete.
 
Papering was actually super-quick. All straight, square, edges, and small size means fewer inches of edge to sand off the extra. Really easy. Sanding the pieces to fit properly in the first place was much more difficult and frustrating, and I didn't do a particularly good job. Fillets will be important.
 
Filleting around the nozzle bits is a tedious, toothpick affair. Not fun, but necessary to fill the gaps.
Nozzle fillets.jpg
Yeah, there are a couple of bubbles there that I only noticed after I looked at this close-up picture. I did better with the ones after.
 
Sincerely hoping to get some painting done this weekend.

I decided to sacrifice a short piece of BT55 to connect the two halves of the rocket together:Ready to paint.jpg
This gives me access to the ends of the centering rings so they can get painted, while keeping the whole thing in one piece so it's easier to manage than juggling two separate pieces.
 
Good luck with the painting hopefully the weather holds up for you, it looks good around here. That seems like a good idea to get the ends of the centering rings painted, that'll add a nice touch. I'm also curious to see how skipping the primer step works out.
 
My plan is regular white primer and white base coat on the full payload section and the fin can. Then I will follow (in the future) with black on the plasma core and two of the fins. Then finally the decals, which will be... "interesting".
 
I attempted a single "paint + primer" coat on the Low Boom SST. I ended up with some bubbles and surface irregularities. I ended up wet sanding and re-coating. So it was pretty equivalent to doing a separate primer step. I think you've done a better job with the surface prep, though.
 
Painting the ends of the centering rings? Im afraid my brain is fried this week and I'm not capable of figuring out ehy you want to paint the faces of the centering rings
 
Painting the ends of the centering rings? Im afraid my brain is fried this week and I'm not capable of figuring out ehy you want to paint the faces of the centering rings
Mainly just to seal them. Not sure if it matters, but can’t hurt.

Parts will look more finished when separated as well.
 
PAINTING, PART 1

Got my white base coat on today. Let's see how it went!

Here's a peek after first coat of primer. This is the sort of thing that filler/primer would have helped. It wouldn't have filled the crack (probably), but it would have shown it to me and I would then have filled in with a bit of CWF.
Base coat-2.jpg
As it stands I will probably do nothing.

Here's what the seam between the rear transition and the fin can looks like:
Base coat-1.jpg
Again, gaps that I did not see clearly before. Fortunately, that one is also a seam between black and white paint, so it will not really be visible at all.

You can also see some pits in the edge of one of the strakes. This is educational for me: I should have realized that the thin CA I used to seal the edges wouldn't fill pits. In the future I will have to do a more careful job with fin edges, probably a bit of CWF after the thin CA. In this case, it'll be black and probably not visible, but since I will be painting over it, I'll have the opportunity to fill it a bit beforehand.

Because I had rather little gloss white left in the can (I was really crossing my fingers that it would be enough), I opted to do two coats of primer and then two coats of gloss. That worked out *mostly* OK, but towards the end of the final coat I was really close to the end of the can and had some come out not too clean and leave me with this:
Base coat-4.jpg
The ripples on the body are annoying but not a disaster. The bumpiness of the bottom fin will need to be worked a bit, either with some ultra-fine sandpaper or polishing compound. Note that I have had comparable results even when filler/primer was applied, so I don't think that's the culprit here. I am more than capable of getting a crappy paint finish regardless of the prep.

Note that the edges of the fins, which had thin CA applied, stayed very smooth. That is interesting. Should I CA the whole fin in the future? That's an expensive approach when using the SuperGold.

Here's the whole thing. Note that I lightly primered the plasma core, but didn't go beyond that, since it'll be painted black. That's why some of it looks yellow-ish here.
Base coat-3.jpg
Preliminary assessment: Although there are some hiccups, I think it came out OK. An advance coat of primer (not necessarily filler/primer, anything) would definitely have revealed some areas that need further filling. Likewise, lightly sanding the whole thing and then applying one more wet coat would completely solve the bumpy paint issues I have here and there, but in both cases it adds another paint step and that's what I'm trying to avoid. I think I can make this work the way it is. So it'll be a 3 foot paint job instead of a 6 inch paint job. That's fine.

Frankly, it's the decals that will be drawing most of the attention, and those are what I need to really get right.

And now it sits for at least a week before I take it inside and start masking for the black coat.
 
My whole system is buily around Rustoleum 2X enamel, but Im beginning to wonder if I should try laquer based something
 
Lacquer seems to have some nice properties. I've been hesitant to switch, though, because... well I don't remember exactly. 🤷‍♂️ BUT IT WAS A VERY GOOD REASON I'M SURE.
 

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