APRO Lander II Build Thread

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ImageUploadedByRocketry Forum1498352583.596801.jpg

Shiny Future is shiny.

Every time I walk past my workbench I stare at this rocket. To say it is the favorite thing I've built is an understatement.

I hope it lasts more than one flight....
 
Well it's built like a brick sht....er....um.......outhouse!

Or maybe it isn't. Read on.

Yesterday I got this bird into the air at the BARC launch (not very far into the air, but it is what it is). It drew some appreciative comments.

Here's my "proud Papa" pose with it and the one decent launch shot I got.
apro_launch - 1.jpg apro_launch - 2.jpg

The up part of the flight was fine, although you could almost feel the D12 straining to push this damn thing through the air. I continue to think an E15 will be perfect for this rocket. Anyway, it didn't go very high but it went pretty straight, minus effects of the wind. Deployment of the 18" nylon chute was perfect with a 3-second delay, everything looked good until I retrieved it:
ImageUploadedByRocketry Forum1500214970.159853.jpg

So I guess even papered fins have their limits. That was the end of its flying for the day.

Because the paper was still mostly intact on one side, I decided to just shove some TBII into the joint, push the fin back into position, and clamp it so it would stay in alignment.
ImageUploadedByRocketry Forum1500214871.869528.jpg

In the end, it still flexed back just a bit, but that won't be enough of a bend to make any difference on this rocket.
ImageUploadedByRocketry Forum1500214091.431870.jpg

But at least she is back on her own.... uh... four feet.
ImageUploadedByRocketry Forum1500214103.852005.jpg

I'll do some finishing work to make it look a little better, although I won't be striving for perfect. I can always display and photograph it from the other side.

I don't know how strong the repaired fin is compared to the others. I admit I'm nervous to fly it again, but I will give it another try in the future once I acquire the necessary E15s.

But hey, it has flown so it is now officially a rocket! And it is still beautiful. :)
 
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That new bend in the fin is minimal for this one Neil. I wouldn't worry about it much either. Don't feel too bad. I've launched mine twice and both times I broke some of the struts loose. No fin cracks though. I am curious what size chute you used though. And about those E15's. Where are you getting yours? I've never used those before. D12-3 seems to be too short of delay and a D12-5 was too long. Maybe I'll look into those E15's.
 
That new bend in the fin is minimal for this one Neil. I wouldn't worry about it much either.

Agreed. That bend is the least of this model's problems, aerodynamically speaking. ;)

I am curious what size chute you used though.

18", which I had thought would be plenty big. Conceivably I could try to stuff something larger in there to slow it down a bit; it's not like this thing is going a mile up in the first place. But that would be getting big to shove into a BT55.

And about those E15's. Where are you getting yours? I've never used those before. D12-3 seems to be too short of delay and a D12-5 was too long. Maybe I'll look into those E15's.

Well that there is the problem. I purchased my original set (used in my Solar Warrior, flew awesome) on-site at a launch, from Heavenly Hobbies. Sadly, none of the launches I have access to have on-site vendors anymore, so I haven't purchased any since. Apogee has them (as do others I'm sure) but I'd want to avoid shipping charges if I can so I haven't really worked out a buying strategy yet. The E15s come with 4s or 7s delay; I'd be going with the 4 for this one. I still have a single E15-7 in my box, but 7s seems way long for this rocket.
 
As you know, my chutes are an inch larger than commercial chutes, but even a 19" chute seems to small for this bird too. I can get a larger chute in that 55, but it would be that really thin ripstop stuff I have. Today is chute day and I plan to repair some and make a few replacements. I'm thinking of seeing how a 22" chute fits in there.
 
As you know, my chutes are an inch larger than commercial chutes, but even a 19" chute seems to small for this bird too. I can get a larger chute in that 55, but it would be that really thin ripstop stuff I have. Today is chute day and I plan to repair some and make a few replacements. I'm thinking of seeing how a 22" chute fits in there.

Yeah, maybe something like a 21"-ish thin-mil chute would be ideal. No one sells in that size hough, 24" seems like it might be a bit much.
 
I would like to launch this rocket again but really was nervous about fin breakage after its maiden. I upgraded the chute to one of Gary's very nice 21" jobbies, but upon finding out that Gary's original was breaking a fin on every flight (or nearly), I decided that reinforcement was needed if she were to fly in the future. After discussing it with Gary, I decided to just do what I do best: take a simple problem and come up with a complex solution, albeit one that would (I hope) be effective and fun to implement. And so all roads pointed to 3D printing.

I found a new inexpensive hub on 3DHubs nearby and had these cuffs printed for the fin leading edges:
IMG_6577.jpg

I debated materials for a while. I was gonna go with PETG, but it's a bit more expensive and I haven't used it before. My concern was that it would be too flexible. Maybe not, but I didn't want to risk it. I also didn't want to take a chance with ABS warping or having poor layer adhesion. So I went back to good old PLA, 100 micron. I printed them in red in the hopes that I wouldn't need to paint them.

I really didn't know how thick to make them. In the end, I probably made them a bit thicker than they needed to be. They are VERY stiff. Total weight for four is around .6 oz. I had an extra printed in case I messed them up. Oh also, this was actually my second batch; the first batch was too small due to a couple of measurement errors on my part. The new batch was the correct size.

Anyway.

Out of the printer, they didn't have the smooth round profile I was looking for, so I performed what could only be called an obscene amount of sanding (PLA is *hard*) to, shall we say, "round them into shape". Here's the before and after (well actually the after and before):

IMG_6582.jpg

After shaping with a 180 grit sanding sponge, I went up the ladder all the way to 1500 grit, after which they were pretty smooth. Not perfect, but still quite good:
IMG_6583.jpg

I checked fit before continuing. The channels needed a bit of opening up to achieve a nice snug fit on the fins. Perfect. Then I applied 3 very quick coats of Future using a paper towel to wipe it on. To hold the parts while applying and drying, I threaded them onto a piece of 1/8" square dowel and held them in a clamp:
IMG_6589.jpg

After the Future, they looked pretty darn good, definitely no need for paint and a pretty good match for the existing fin color. That made me happy.

The fins were prepped simply by sanding the paint off the leading edges, so the epoxy would have at least one raw surface to bond to:
IMG_6588.jpg
I tried not to think to hard about what I was doing here. I was so proud of this paint job and here I was making hash out of it. But all in service of the greater good, so I pressed on.

For each part, a nice bead of 30 minute epoxy was carefully laid into the channel...
IMG_6591.jpg

...and then it was stuck onto a fin. I had practiced applying them enough times during fit testing that I knew pretty well exactly how to do it to get them to land in the correct position the first time (or at least close enough so I wouldn't need too much adjustment). And here is a fin with the cuff applied:
IMG_6592.jpg

Pretty good, eh? Here's an end view of one of them showing how it fits on. Sorry for the blurriness but you get the idea:
IMG_6594.jpg

The very top of one of the cuffs just wouldn't lay flush to the "muscle". I tried for a while but really there was nothing I could do about it, so I just forgot about it. You only see it if you inspect closely, and I'm certainly not concerned about aerodynamics (that train left the station a loooong time ago for this rocket):
IMG_6595.jpg

And here is the finished fin can.
IMG_6593.jpg

I'll say this: if these don't prevent breakage then I shall give up and retire this rocket. As it stands now, I will be ordering up some Aerotech E15s for launch this spring or summer.
 
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It’s Great Planes, which I think is the same as BSI. Mine might just be getting old, dunno, but it still seems strong when cured. I’ll need a fresh supply one of these days.
 
Those turned out great man. Touche! I have too much in the work pile right now to apply repairs to mine. I'll just do the fixer upper I told you about doing and see how that works for me. Either way, one of us is bound to have something that works.
 
Future liquid floor wax. I think it was replaced with Pledge anymore, but a 4-1 ratio of Pledge/Future to Simple Green makes for a surface coating that is pretty glossy.

Oh, okay. Thx for the reply.

So it won't yellow/fog with time and/or exposure to UV?
 
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Future does not yellow. Here's the canonical info page: https://www.swannysmodels.com/TheCompleteFuture.html

I have never felt the need to mix in Simple Green; for brushing on it's fine straight out of the bottle.

This stuff has also been tried with success, although not by me (yet): https://www.amazon.com/dp/B000BYE9TI/?tag=skimlinks_replacement-20

There are many ways to skin this particular cat. :)

I have to use the Simple Green. Straight OOB Future won't relax without it. Seems to want to draw up and pool itself. Might depend on a number of reasons though, paint, weather......
 
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I have to use the Simple Green. Straight OOB Future won't relax without it. Seems to want to draw up and pool itself. Might depend on a number of reasons though, paint, weather......
Interesting. Maybe I'll try it one day, just to see how it compares. There are occasions where I do wish it were just a bit thinner.
 
APRO Lander II flew again yesterday, this time with the fin cuffs, Gary's parachute, and an AT E15-4.

Suffice to say everything went better than last time. The E15 got it moving pretty quickly and to a decent height, perfectly straight up; under the new parachute the rocket drifted down and landed upright, with all four fins intact. All modifications did their job.

There was a bit of damage at the edge the bottom of the large transition. I think that must have happened on the last flight and I just didn't notice it, because this time there's no way that spot could have touched anything on landing.

Anyway, the E15-4 is a perfect engine for this rocket, and the one I will use in the future.

Here's a fuzzy but still decent screen grab from the video I took.
apro 2 flight 2.JPG
 
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