APRO Lander II Build Thread

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In other news, finally got this today:
View attachment 305412
Look forward to testing fit and getting this glued in, which will then allow me to glue the big transition.

(weighs in at 1.3 g, in case anyone is interested)

So this goes on the inside of the large shroud, correct? I can see why it might be a hassle to line up without that conical section.

I'll finally be able to start to dabble with 3d printed parts soon, so since you've done a few, what's your impression of them?
 
So this goes on the inside of the large shroud, correct? I can see why it might be a hassle to line up without that conical section.
Yup. I hope to have it installed pretty soon so I can show it. It'll be much clearer in position.

I'll finally be able to start to dabble with 3d printed parts soon, so since you've done a few, what's your impression of them?
It's fun, that's the #1 thing. The print quality varies depending on who's printing, what material, and what resolution. I've had mixed results so far, but most stuff has been usable. Cost is non-trivial, but not too bad if you print in cheap materials (I'm using mainly ABS these days) and group together some jobs to dilute the fixed setup fees.

Overall: thumbs up. Lets me do things that I otherwise couldn't, and I still get a thrill from going from CAD file to physical object.
 
I'll get back to the transitions later (try to contain yourselves), but for now let's catch up on some mundane build stuff I did a while ago.

To mount the BT80 tube onto the BT55 core, I needed 55/80 centering rings. I really wanted 1/8" birch ply, but the only ones I could find commercially were black fiber. I suppose I should feel lucky I found them at all (it's kind of an oddball combination) but I am not a fan of the fiber for this application. Apart from the black dust it puts all over everything (I quickly learned to give each one a good wipedown before test fitting anywhere) it's not very rigid. These rings are fairly large, and the extremely high drag of the BT80 assembly means that it'll be pushing pretty hard against these rings when flying. So I decided to double them up for strength: once again, the magical formula of two layers laminated with some glue makes for an assembly that is really rigid. Again, maybe overkill, but whereas the transition shrouds are mostly cosmetic, this is part of the core structure of the rocket and I wasn't going to take any chances.

I positioned the rear ring(s) on the BT55 to be flush with the end of the BT80. In retrospect I don't know why I didn't leave a little more room for a fillet in back there; it'll be totally hidden so there's no cosmetic reason to have it flush. It *did* make it easy to position the BT80 during assembly, so there's that I guess.

After I slide on the double ring I realized that I had measured the distance to the back of the BT55 incorrectly. In a panic I twisted it and pulled it off, relieved that the Titebond II had not set yet. I re-measured and put it back in the correct place. At the time I was incredibly glad that I noticed this, else I would have had a mess on my hands. Now, however, I recognize that the error (ring was too far up the tube) would have simply put the rings non-flush with the BT80, which would have been fine. Oh well, no harm done.

The front rings were positioned to be a good fraction of an inch behind the front of the BT80; there was no reason to try for precision there.
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You can see the nice dirty mess from the mis-glued rings on the left, and the dirtiness of the black fiber rings in general.

When dry, I glued it into the BT80 assembly.
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At the top you'll see yet another ring. I put that there (just a single, it's not structural) *not quite flush* with the BT80 to provide an anchor for the transition. At the time, my thinking was that I was going to put those little support fins in front of the ring, so I couldn't pre-install the ring into the transition. Now, I know that I probably *won't* be using those little fins, so in fact I could have glued the ring into the transition and then (eventually) slide the whole thing on. Live and learn.
 

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  1. This rocket has a pleasingly small amount of spirals to fill, since so much of the body tubes are covered with shrouds
  2. It occurred to me that I might be lavishing excessive attention on small details in a subconscious effort to drag out this build, because is so damned fun I don't really want it to end. This design has maximum quantities of all the things I enjoy most about rocket building (all that wood-and-tube structure, complex design planning, 3D printing, fin papering). I am so glad I decided to build it, regardless of how it turns out in the end. Thanks again to Gary for this wonderful design.
 
So my existing shrouds didn't quite fit over the centering ring, so I made a new one (single layer) and it was *perfect*:
ImageUploadedByRocketry Forum1479438649.875143.jpg

You can just see the edges of the paper on the outside of the ring.

I also decided that the transition that was really most vulnerable to crushing was the big one in the rear, because it has so little curvature there's very little strength gained from its shape. So I made a double layer, and thought it looked great.

Next day I came back and noticed that the two double layer shrouds had puckered quite a bit from the Titebond II. So, lesson learned: don't laminate shrouds with a watery glue. Both of those shrouds went into the circular file.

Finally, I had already printed a couple more of the front shrouds on the cardstock, so I figured I might as well make it. So I made a double-layer, this time using a glue stick, which was the only glue I could think of that absolutely would not pucker the paper. Normally, I trust glue sticks about as far as I can throw them (although I could probably throw one pretty far...), but I gave it a shot anyway. Indeed, the adhesive qualities of the glue stick are almost non-existent, I don't even know how anyone does anything with them. But after tacking down a couple of loose corners with Titebond (just a tiny amount), it actually looked OK. No, better than that: it looked perfect. And strong. Here it is in the drying rack:
ImageUploadedByRocketry Forum1479438637.095383.jpg

So I decided to use it. Before gluing it on, I needed to mark the fin lines on the BT55, lined up with the ones on the BT80. I made a little paper template to help me line them up:
ImageUploadedByRocketry Forum1479439392.473096.jpg

And then, after marking the tubes (and removing the paper template), I glued the shroud into place. It fits perfectly and looks very nice. I still need to fillet and smooth out the edges, but it appears to be a success.
ImageUploadedByRocketry Forum1479438675.484073.jpg

In this picture you can see that the seam on the shroud lines up with one of the fin lines, where it will be covered by a strake.

And thus ends the shroud-making saga, at least for this rocket. I'll feel pretty confident with these things going into the next build (I'll need one or two for Starship Avalon).

Oh, for the rear transition I decided to stick with the shroud I made originally (from the posterboard), and just be careful with it. I don't feel like making any more.
 
OK, time to get this rod catcher thing installed.
ImageUploadedByRocketry Forum1479222454.616836.jpg
First I checked that the lug fit through it properly:
ImageUploadedByRocketry Forum1479523611.586310.jpg
Whew. It actually fits just about perfectly, just a bit snug but not too much.

Then I put the shroud on, slid the catcher in from behind (those holes in the giant ring are coming in handy) and marked its position.
ImageUploadedByRocketry Forum1479523626.007655.jpg
Then I glued it on with some epoxy. For positioning, I merely centered it on the line I had previously marked:
ImageUploadedByRocketry Forum1479523650.072021.jpg

Then I glued on the front lug and made a video:
[video=youtube;nJhjlvWauQY]https://www.youtube.com/watch?v=nJhjlvWauQY[/video]

Fun!
 
I had no idea you were going to put a lug inside of the catcher. I figured the catcher was the lug. It still could be ya know.
And as an avid believer in those nasty, icky, dusty, yucko black fiber centering rings, I've heard those comments about them being dirty before. Nothing a little wiping won't fix. And I always keep a wet / damp rag on the bench so I can wipe my fingers off. As for doubling them up?......I'm not even going to go there. I will say this in their defense. They can handle F32 composite motors just fine.
 
I didn't even think about using the catcher *as* the lug... 😳 oh well. I think I wanted the front lug further up around the CG, but it probably would've been fine with just the catcher.
 
Looking great so far! I know what you mean by taking your time on a build that's fun.
 
Strakes are on.
ImageUploadedByRocketry Forum1479584738.062052.jpg

You'll notice that the one on the left is a bit shorter; that's because I got careless while papering and snapped the tip off. I'll probably cut a sliver of balsa and patch it in there later to even things out.

As an experiment I glued on the strakes with Titebond No Run No Drip (what I normally use for fillets). Interesting! It is extremely tacky almost immediately; just push the fin into place and you're done. I don't know how strong it is compared to the Titebond 2, but for the strakes it doesn't matter.

The big transition is still just a dry fit BTW.
 
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After gluing on the big transition (which I'll get back to) I did a quick test fit of the rear transition to see it all together. This is what I saw:
ImageUploadedByRocketry Forum1479693646.209950.jpg
I cannot imagine how I missed that. The edge is a very poor match for the big ring. Apparently I did a terrible cutting job, but was so focused on other aspects that I failed to notice.

I have printed out three new templates on my 65 lb cardstock, and will have at it yet again.
 
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It appears that the opposite side is "pinched", and that would indicate to me that your central BT isn't centered.
 
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It appears that the opposite side is "pinched", and that would indicate to me that you central BT isn't centered.
I concur. It's as though the bottom shroud is off to one side. What I see, is the aft shroud overlapping on one side, and underlapping (word?) on the other side.
 
I agree it may look like that, but the precision of the centering rings is much higher than my hand-scissor-cut transition, so the transition is the more likely culprit. I'll confirm all and report back. In the meantime, my scissor technique is getting pretty good... :)
 
Two new ones, a double and a single (65 lb card stock).
ImageUploadedByRocketry Forum1479737939.527481.jpg
I made the double with the glue stick, this time applying the glue to both surfaces. Much better grip. Thus far the double has held its shape (no rippling from the glue). Will try the fit as soon as I get a chance.
 
I've had good results with super thin CA(BSI blue bottle) on paper transitions and cones. Given any consideration to using it on these?
 
I've had good results with super thin CA(BSI blue bottle) on paper transitions and cones. Given any consideration to using it on these?
I have a bottle of the stuff and have thought about it here, but I confess I can't quite guess at the exact procedure that should be used, particularly on a large and somewhat floppy shroud like this (i.e., need to ensure that the shroud holds its shape while the CA is drying?) Care to describe exactly how you do it?
 
I usually drip a little on and then use the "nozzle" of the bottle to spread it out quickly. One short section at a time. I usually use wax paper or ziplock bag material for a non stick surface underneath.
 
Muscle:
ImageUploadedByRocketry Forum1479832663.496502.jpg
I used basswood 1/16") because (a) I won't be papering it (gotta draw the line somewhere) and (b) it could stand up to some handling when I was sanding it to shape.

Hope to glue these guys in as soon as possible.
 
Muscle:
View attachment 305862
I used basswood 1/16") because (a) I won't be papering it (gotta draw the line somewhere) and (b) it could stand up to some handling when I was sanding it to shape.

Hope to glue these guys in as soon as possible.

They may seem like a PIA to work with, to mask off and paint with a brush, but it's amazing how those little parts are like putting a nice frame around a portrait. They add so much to the fin aesthetics. This is where I got hung up on the painting of mine. I don't particularly like to mask and these are the pits.
 
Yeah? You aren't installing the struts either. Or are you? Those make it quite difficult to apply the masking and painting.


The first Lander.
DSCF1665.JPG
 
Looking good! Say, what kind of motors and altitudes are you expecting?
Would you guys be able to add working landing gear like the Mars Lander's in the next incarnation? :) :) :)
 
Looking good! Say, what kind of motors and altitudes are you expecting?
Motors: D12 and E15
Altitude: not much! :)

It sims to 300-something on a D12 and 500-something on an E15. Thrust profile of a BP F15 would be ideal to get it up a bit more, but then it'd be seriously tail heavy. 24mm F reloads are likely to be the "best" motor, but I don't do reloads at this time so the disposable E15 will probably be my go-to for this one. It'll maiden on a D12.

Would you guys be able to add working landing gear like the Mars Lander's in the next incarnation? :) :) :)
Next incarnation? You mean your upcoming build of the APRO Lander 3? Yes please! :wink:

It would be cool to have a fleet of these things, all slightly different, although I don't know when they'd ever be able to get together.
 
Would you guys be able to add working landing gear like the Mars Lander's in the next incarnation? :) :) :)

I deliberately strayed away from mocking the Mars Lander. Including the action landing gear. I didn't want it to be a spinoff design. I can see how it is similar, but having built a Mars Lander, they are nothing alike. "The APRO" which precedes anything here and even the Mars Lander, was designed back in the late 60's and brought to life by LW Bercini in a model that proved to be very unstable. The Newly titled "APRO Lander" was is a redesign created back in 2009 and was flown successfully that same year. The design was flawed having used a BT 50 as the core tube which just isn't wide enough for a proper sized chute.
 
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