Biohazard build thread

I do not have kind feelings towards whoever first figured out the tube spirals needed to be filled. But now I can't unsee those spirals (and neither can anyone else), so I do my duty as a model rocket builder and slather on the thinned CWF. This time I tried applying with a knife blade, but really didn't like it, so I went back to my standby method of using a chopstick, then squeegeeing off the extra with a dull razor blade. I did a fairly quick and careless job, figuring that I'd fill in any last bits with Bondo after priming, but I actually think I got everything pretty well covered.

Getting to this point is always a sigh of relief:

In case you're wondering, I did *not* fill the spirals on the inside of the ring or the tube fins, because @#!& that. :hot:

What's wrong with spirals? I love spirals! :wink:

KenECoyote said:

What's wrong with spirals? I love spirals! :wink:

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Ha ha, makes me want to go heckle you in your thread about filling those dang spirals. Nothing a big tub of spackle couldn't fix! 😝

neil_w said:

so I do my duty as a model rocket builder and slather on the thinned CWF. snip
In case you're wondering, I did *not* fill the spirals on the inside of the ring or the tube fins, because @#!& that. :hot:

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I agree with you...."@#!& that" and @#!& doing any of the other ones as well. Screw the spiral police. Nobody says it's your "duty". I have absolutely no shame in ignoring low (and some mid) power spirals covered with glassine. Now the big raw tubes with those grand canyon style spirals....that's another story. People are all the time looking at my models up close and nary a word about spirals. And I don't care if they are thinking about it and not saying anything, because if it really mattered, wouldn't they say something? I am way more pleased when they say how cool my models look. That beats just being pretty all day long...to me.

Yeah, I'm back from the launch. Now you get to put up with me again....LMAO!

Gary Byrum said:

I agree with you...."@#!& that" and @#!& doing any of the other ones as well. Screw the spiral police. Nobody says it's your "duty".

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For me it's right there with rounding fin edges: unnecessary but I feel absolutely compelled to do it. One day I hope to be cured of both of these afflictions. It's not that awful really, I just wish I had a more efficient method of applying the stuff (I seem to be getting much better/quicker at the sanding part).

We all have areas where we focus attention, and others where we shortcut. Where I take my shortcuts is in painting. My rockets get one coat of filler/primer and then top coats, period. Spraying opportunities are too precious for me to deal with multiple loops of fill/sand/prime/sand/etc. like I read from some other folks. I'm generally satisfied with my results, though I don't typically get the mirror-like finish some others do.

Yeah, I'm back from the launch. Now you get to put up with me again....LMAO!

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Any APRO Lander updates? Looks like my build is going to be delayed until after the summer, so I need yours for my vicarious thrills.

KenECoyote said:

What's wrong with spirals? I love spirals! :wink:

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I love Spiral...

[video=youtube;22IHZYzcu8Y]https://www.youtube.com/watch?v=22IHZYzcu8Y[/video]

but I hate them on my builds. The key thing to remember is that the only thing that really matters is that you are happy with it in the end.

neil_w said:

For me it's right there with rounding fin edges: unnecessary but I feel absolutely compelled to do it.

I'm generally satisfied with my results, though I don't typically get the mirror-like finish some others do.

Any APRO Lander updates? Looks like my build is going to be delayed until after the summer, so I need yours for my vicarious thrills.

[/COLOR]

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Rounding fin edges is something I will do for performance sake. Air will come around a rounded surface much better than a flat one. I'm 98% for the rounded edges, although for aesthetics reasons, the APRO Lander is getting flat ones.

For some reason, I get better finishes on nose cones than I do fins, using the same filler approaches... But it isn't so hard to do. I can't see using CA for this though. CA will give balsa killer strength and assist in a smooth surface, although, you have a lot of hard sanding to do. I use the water based DEFT sanding sealer which will strengthen the wood and help smooth it. Then it's the usual wood filler slather that gets the job done well. Most of my nose cones have a glassy finish after that. My fins would too, if I could just get it right.

My Lander and the Magic Dart are all that's left on the bench, and I had planned to get the Lander done before next months launch. After I get a motor inventory done and get this stuff back upstairs, I'll try to get some movement on that Lander. It's really not that far from being finished.

Gary Byrum said:

Rounding fin edges is something I will do for performance sake. Air will come around a rounded surface much better than a flat one. I'm 98% for the rounded edges, although for aesthetics reasons, the APRO Lander is getting flat ones.

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Yeah, I might make an exception for that one... but in the end I'll bet you a dollar that I end up rounding them. Compulsion! (or maybe I'll just take the sharp edges off and leave it at that. Geez, I'm really looking forward to that build but gotta be patient).

For some reason, I get better finishes on nose cones than I do fins, using the same filler approaches... But it isn't so hard to do. I can't see using CA for this though. CA will give balsa killer strength and assist in a smooth surface, although, you have a lot of hard sanding to do. I use the water based DEFT sanding sealer which will strengthen the wood and help smooth it.

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For this nose cone, I found that the CA sanding was easier since I wasn't trying for it to be the perfect final surface. I'll be interested to see how it comes out after painting. But I'm not really satisfied with the CA technique, so I will keep searching for something that works better for me. Next order I'll probably throw in a couple of small balsa cones that I can experiment with, first will be epoxy, which I have convinced myself I can get to work with relatively low effort. We'll see.

Do you use the DEFT spray or brush on? Does it have much odor?

K'Tesh said:

The key thing to remember is that the only thing that really matters is that you are happy with it in the end.

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I had not problem with visible spirals until I learned that they are a thing that can be eliminated. Can't unring that bell!

neil_w said:

Do you use the DEFT spray or brush on? Does it have much odor?

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If you knock off the sharp edges, it's a serious improvement. I use the DEFT in a can and there's no odor. I switched from using Minwax sealer which has an odor, but it didn't have much wood strengthening qualities. And it dries up in the can within a year, or starts to. It' gets thicker and you really can't thin it out. Waste of money. The DEFT will make you a happy camper.

Gary Byrum said:

I use the DEFT in a can and there's no odor.

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I believe both the spray and brush-on containers would qualify as "cans". I'm guessing you mean the brush-on, though...

neil_w said:

I believe both the spray and brush-on containers would qualify as "cans". I'm guessing you mean the brush-on, though...

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Correct. I would have specified spray or rattle can otherwise. This stuff soaks in really fast and makes you think you need more than you do. It just gets harder to sand the more you lay it on. One good coat on a fin gives (aprox) twice the strength. If you like to use sealers, which I do, you'll prolly like this better than the smelly stuff. I had my doubts about it at first, but that was over after my first usage.

neil_w said:

Ha ha, makes me want to go heckle you in your thread about filling those dang spirals. Nothing a big tub of spackle couldn't fix! 

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Haha! Just friendly jesting! For those of you not aware, Neil and I are rocket buddies.

K'Tesh said:

The key thing to remember is that the only thing that really matters is that you are happy with it in the end.

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+100%

KenECoyote said:

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Artist's conception of Ken's rocket with spirals properly filled:

Hep to it, brother. :neener:

K'Tesh said:

The key thing to remember is that the only thing that really matters is that you are happy with it in the end.

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Indeed, and the journey is to figure out exactly where one's "happiness point" is, and learn how to get there in the most enjoyable way (assuming one is in it for enjoyment in the first place, as I certainly am.) Of course, the "happiness point" tends to be a moving target as one's skills and ambitions improve...

neil_w said:

Artist's conception of Ken's rocket with spirals properly filled:

Hep to it, brother. :neener:

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I'll call that one "BioDome"! :wink:

KenECoyote said:

I'll call that one "BioDome"! :wink:

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Put some nose weight in and it'll probably fly fine. Might not spin so well though...

If you guys aren't careful, you're gonna screw around with each other and come up with a killer concept you'll both be fighting over.

neil_w said:

Put some nose weight in and it'll probably fly fine. Might not spin so well though...

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:rofl:

Gary Byrum said:

If you guys aren't careful, you're gonna screw around with each other and come up with a killer concept you'll both be fighting over.

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"Spiral Hazard"! I like that!

We now return to your regularly scheduled build thread already in progress.

An excessive amount of thought has gone into the build/prime/paint sequence of this rocket, because I'd rather overthink it up front than find myself in trouble later on. I'll get to some of the details in a later post, but one thing I decided pretty early was that the tube fins or pods or whatever you want to call them (is there an official way to distinguish them? I tend to think that pods have nose cones on them, but am not sure) would be primed and the interior painted before being attached to the fins.

In a fairly recent thread that I can't find now, a question was raised about how to attach tubes/pods squarely and securely to the ends of fins. I think it was TopRamen who talked about the the method that I chose to use here.

The basic principle is: attach a very flat strip of balsa to the tube. It is easy to get this on square. Then, later, use a double glue joint to attach the fin to the strip. It is easy to get *that* square.

First, I cut a piece of balsa about an inch long, and the width of the fin roots. Then I rounded the edges, because I wanted these to match as closely as possible with the fins themselves. Next I cut about 1/16" strips off it, and attached them to the tubes. After gluing, I then sanded down the strips on a sanding block they were extremely thin (barely there!), probably about 1mm. The result looks like this:


When the time comes, it should be very easy to get a nice square attachment of that onto the fin. Ultimately, that strip should be completely encased in the fillets that get added on at the end. Maybe it's an overthink, but it should work.

Here are the three of them, all finished:


It looks like the middle one is a tad shorter than the others; with all the sanding I did on the cut ends it proved to be nearly impossible to make them all the same size to a very precise degree. I'm hoping that won't really be visible in the end, because the tubes will be fairly far apart in the fully assembled model.

This build has progressed faster than I expected. A few minutes here and a few minutes there and I've made it pretty far.

I will still defer many details of the build/prime/paint sequence, but I did (after going back and forth a few times) decide to mount the rear fins before priming. On my first few BAR builds I primed all parts before any assembly, but I'm modifying that and now leaning towards assembling anything I can before priming. Basically, anything that I believe I'll be able to sand effectively after assembly gets assembled first. The rear fins, minus the tubes, being TTW mounted and all, should be easy to sand in place.

For each fin, I first checked tab height. One of the three needed to be knocked down just a bit, and then it was snug; the others were good as-is. Then I glued each fin against the, uh, "left" edge of the slot, which was the side that I originally marked with the fin-marking guide, and applied some Titebond II to that joint as well. Here's one in the comfortable embrace of my 3D-printed alignment jig:


I then had a look at the gap on the other side. Here's the biggest one:


I stared at it for a while, though of ways to fill it, and then just said "fillet". I applied my usual fillets with Titebond NRND and just let it cover over the gaps. The end result feels plenty strong, don't really foresee any problems. In hindsight, I probably could have done a better job trying to force some glue *into* the gap but I don't think it will matter. The rear fins are attached.


I haven't yet succeeded at getting a good fillet picture, if I do get one I'll add it later, but hey, they're just fillets. [edit: no fillet pictures forthcoming. However, they look good and the fins seem really strong]

And now, somewhat amazingly, I am ready to prime. Which means a nice, painful break in the action while I wait for an opportunity to go outside and do some spraying. In the interim I'll write up the sequencing.

This is moving along nicely! Looking like some quality work there. Once fins are on and motor mount is in, there is a certain "I'm getting there" feeling.

Cabernut said:

This is moving along nicely! Looking like some quality work there. Once fins are on and motor mount is in, there is a certain "I'm getting there" feeling.

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Yeah, it's been rather straightforward and drama-free so far. Not the most interesting build in retrospect, but I guess that means I planned it out correctly.

Doing justice to the paint job will be the real challenge. There will be many opportunities to screw it up.

Here are the parts, all ready for priming, with future glue joints masked off:


The shoulder of the nose cone is wrapped in tape and inserted into the payload section for convenience. When it comes time, I might also assemble the two tubes, just so there's one less piece to wrestle with.

As I mentioned previously, my goal was to assemble everything I reasonably could before I cracked open a rattle can. In this case that still leaves a bunch of loose parts to deal with. Here is my planned sequence:

1) Everything in the above picture will be primed (including the interior of the ring and tubes)
2) The interior of the ring and tubes will be painted before assembly.
3) I will probably paint the outside of the ring as well before assembly, minus the glue joints.
4) The tube fins (seriously, are they tube fins or pods? What's the official definition?) and middle fins will be attached (at this point I'll be able to test the fit of the ring)
5) Everything will be painted
6) Ring will be attached
7) Paint will be hand-retouched at the joints between the ring and the middle fins.
8) Clear coat

The whole reason for treating the ring the way I am is that it seem like it would be very very difficult to work around the ring once it is attached, so I will delay that until the end.

As with many other things, there's probably a bit of overthinking here but I sure don't want to get stuck due to lack of proper planning.

Seriously, your build is looking great! :clap:

I read your design thread researching for a ring project of my own that I am about to undertake, and even though I am late to the party, I am enjoying your build thread as well.

neil_w said:

4) The tube fins (seriously, are they tube fins or pods? What's the official definition?)

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My name is not Webster or Oxford, and I am not an expert, but here is my breakdown

• Ring fin: A fin constructed from a tube that goes around the main air frame
• Tube fin: A fin constructed from a tube that attaches directly to the main airframe.
• Pod: A tube that is mounted to a fin (can be either open or closed)

Mr Rocket said:

Seriously, your build is looking great! :clap:

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Thanks! Got some primer on it today, which should clear the way for some additional assembly. Spraying the insides of the, ur, "pods" was a joke, I'll almost certainly have to hand-paint the interiors when the time comes. The ring was no problem.

My name is not Webster or Oxford, and I am not an expert, but here is my breakdown

• Ring fin: A fin constructed from a tube that goes around the main air frame
• Tube fin: A fin constructed from a tube that attaches directly to the main airframe.
• Pod: A tube that is mounted to a fin (can be either open or closed)

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Sounds good, but I think that one addition would be that anything that is not open (i.e., has a nose cone or some sort of block) is a pod.

Unless someone registers a dissenting opinion, I will hereby call the doodads on this rocket "pods".

Well guys, instead of speculating, I did what you might not have done. I googled and did an image search on ROCKET POD and came up with a boat load of these. It appears that most weapon types of pods have multiple holes in them for firing rockets or other various projectile exploding devices.

Gary Byrum said:

Well guys, instead of speculating, I did what you might not have done. I googled and did an image search on ROCKET POD and came up with a boat load of these. It appears that most weapon types of pods have multiple holes in them for firing rockets or other various projectile exploding devices.

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I would agree that that is a very "official definition" of a tube thing that launches projectile weapons... but I would not say that the definition applies directly to "cylindrical crap that people add to model rockets because it looks cool".

OK, then would you say, that a submarine torpedo tube classifies as a pod? Or maybe even a "proton torpedo" (sci-fi) is launched from a pod? A singular reloadable tube. To me, both of these could be classified as pods. And FWIW, I'm on your side here. I call em pods too.

Slightly updated the paint job:

The new swoops on the ring will actually make the painting easier, because the joints between the middle fins and the ring are now all red, so I'll be able to apply the red after the ring is glued in. There are two possible ways to do the black on the ring, haven't decided which yet:

1) pre-paint the ring black, and then apply paint mask to the desired black areas before spraying the red
2) Just paint the whole ring red, and then apply black vinyl to create the black areas.

Either way Mark Hayes wins.

I also experimented a bit with putting some sort of designs on the rear fins (including the Biohazard logo) but haven't liked anything yet. After the modification to the ring, the paint scheme is kind of feeling "done", but I'm sure I'll still fiddle with it further.