APRO Lander Build Thread

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Gary Byrum

Overstable By Design
Joined
Aug 4, 2011
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Location
Lincolnton NC
I'd like to thank Neil_w for this pic. It's the best example there is of what my first APRO Lander looked like before I botched the finish. Also, this rocket needed a BT-55 main tube rather than the BT-50 it had.

View attachment 286848

Thanks to an interest in this design, and knowing I should have used a larger main frame tube, I’ve decided to build it again with improvements. Particularly the launch lug installation. The “uh-oh” moment on that note, happened after the construction was done. At least it wasn’t forgotten. It just had to be a custom install.

Here are all the parts. The big tranny is being formed as will the others to follow. The fin template shows 2 versions of a “fin muscle” that will be installed after the fins are glued in place. I will explain their purpose when the time comes. Also, in another thread, I mentioned having to turn your own nose cone, when actually, a PNC 55-BB will do the job nicely. So ignore that part of the template. The disk shape with “Make 2” are the 6” CR’s. I may only have to make one if I’m lucky.

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Well, not so lucky. It’s really hard working two really wide trannys on to one CR, so I blew it off. Not that much weight anyway. This time I included the two 55/80 CR’s that I forgot in the parts pic. You’ll notice also, there are “U” shaped notches in all of the CR’s. These are for the launch lugs/launch rod to fit through. This was my error in the first build. All trannys have been glued and fitted and one of the CR’s has been mounted on the aft tranny. After the CR has been mounted in the forward tranny, holes will be made in the forward and aft tranny for said launch lugs to slightly protrude the outer surfaces.

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Hey, cool! By the way, what does "APRO" stand for?

Also, what weight card stock are you using for the different transitions?

I realized sometime after I posted my picture that I had given it three fins whereas yours has four. Whoops. So I decided that my version, currently in planning, would be 3F, with a few other mods just to be different. We'll see if I ever get around to building it. :) In the meantime I shall watch and learn.
 
APRO
Aeronautic Projects & Rockets Organization.

LW came up with that definition. I came up with the acronym. I didn't know what it meant, I just liked it. We were teens back in those days. We named our club APRO. Forgive the spelling of "model", we were still learning how to spell. BTW, it looks just fine with 3 fins. Have fun with THAT alignment. :grin:

APRO Club House.jpg
 
I came to discover, that I needed 2 more CR’s for this build. Another 55/80 and a 55/2.75”. The BT 80 was going to get 2 CR’s and I had to make the 2.75”one. So, let’s break out the OLFA circle cutter again and get at it.

This specialized size is going in the smaller end of the big tranny, but recessed about 3/16” from the edge. I used the little blocks of wood shown as a stand off for that ring. You’ll see why when I get ready to assemble the rocket. For those in need to know, I am using two types of poster board for this build. The 6” CR’s and the 2.75” one, are cut from 1/16” thick poster board. Two of the trannys are made from something heavier than 110#.stock. Wally World has poster board sizes at $1.49 and it’s perfect for these trannys. There was no weight factor on it, but my calipers seem to show 1/64” thick. The 55/80 CR’s are the Letramax black fiber type. The BT-80 tube is 2 3/8” long. CR’s are glued flush to both ends of the BT-80 (takes 2). The forward shroud is the only 110# stock and I CA’d the surface, heavy on the joint area. I’ll show why on that later on also. It got the 3rd 55/80 CR.

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APRO
Aeronautic Projects & Rockets Organization.
Gary,

As long as you are supplying historical details, you should post a pic of the original Apro rocket design from....what, 1969?

Neil, I built one of those original designs. It was seriously unstable. Gary was sitting on the ground and it practically landed in his lap. He kicked it to pieces trying to get away from it. Yeah, we were pretty naive about stability and other safety issues back then....just kids. But we were enthusiastic and creative. We were always trying new things - and making plenty of mistakes. But in the process, we developed a knack for originality and an intuition about structural stability.
 
APRO
Aeronautic Projects & Rockets Organization.
Gary,

As long as you are supplying historical details, you should post a pic of the original Apro rocket design from....what, 1969?

Neil, I built one of those original designs. It was seriously unstable. Gary was sitting on the ground and it practically landed in his lap. He kicked it to pieces trying to get away from it. Yeah, we were pretty naive about stability and other safety issues back then....just kids. But we were enthusiastic and creative. We were always trying new things - and making plenty of mistakes. But in the process, we developed a knack for originality and an intuition about structural stability.

Yes, that was Jeff's (my little brother) OT.

As we were already tuning into our design ideas, it was the failed flights that also taught us about stability. For me, I found some success using bigger fins on rockets. LW learned about CG and CP way before me and we both shared ideas and groomed each other for better flying designs. I can bet there's 20 dozen designs in our old drawings (which we still have) that would be total stability failures. Anyhoo, LW would be the first to build our signature model representing our club name, and as I recall, HE FLEW IT NEKKID!. Not only was it unstable, but built rather fragile. Didn't take much for me to mash it to pieces. It looked something like this.

APRO 1969.jpg
 
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Here, that forward tranny got sanded on the joint area until I got it level with the underlying part. This eliminates any bump that could show if I had just filled it and sanded. I run into this so often and it helps a lot. Nothing goes perfect of course. It still needed a little Bondo, but not very much.

The two paper disks with cross marks, are how I was able to mark the big tranny for fins. Both disks have a tic mark that lines up with the shroud joint. Taped those in place, marked the tranny at the cross marks and used my aluminum angle bar to draw the lines.

The forward and aft trannys have been marked where the launch lugs go. I sort of regret that recess I put in the top of the big tranny now. I really didn’t need it. Not a problem though. That’s what that big box of balsa scraps are for. Stuff like this. I’ll use enough to build flush with the hole and will make for a gluing surface for the BT-80 CR’s. Originally, that BT-80 was supposed to slip inside the hole, but now I’m not going in that direction with it.

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You should upscale it using Estes PSII parts... Then it'd be APRO PRO :wink:
 
You should upscale it using Estes PSII parts... Then it'd be APRO PRO :wink:

Nothing's impossible. But these big trannys are tough to get right. I've always been more successful with smaller ones. You'd think it would be the other way around, eh?
 
After having to widening the lug holes a little, I started on the forward and aft trannys where the lugs protrude. The aft was pretty cut and dry, but the forward tranny presented its own set of problems. I’m using ¼” lugs because the Sunward lugs fit tight on the club launch rods. If you look closely at the pic, you’ll see gaps on either side of the lug in the tranny. They are also jagged. I don’t care how patient I can be, cutting through a tranny coated in CA is like carving through plastic. My ¼” Dremel barrel bit is the perfect size for the job, but it kept shifting on me. I can’t just fill them with putty because that really doesn’t work well. I suddenly remembered having a can of “Great Stuff” and I’m going to attempt to fill the inside near the lug area to a point where a little putty will stay in place and the foam will act as a surface. Prolly have some inside contour sanding to do the get the fit.......yay.....sanding........:eyeroll:

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Why did you feel the need to CA the front transition anyway? Seems like it'll be held quite securely by the attached strakes.

Oh, and I'm finally getting a feel for the size of the big transition. Wow. :eyepop:
ImageUploadedByRocketry Forum1460125007.046105.jpg

(Just an experiment made with printer paper, for now.)
 
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Why did you feel the need to CA the front transition anyway? Seems like it'll be held quite securely by the attached strakes.

Oh, and I'm finally getting a feel for the size of the big transition. Wow. (Just an experiment made with printer paper, for now.)

The forward tranny is much thinner paper than the rest of the rocket. The lower portion of the strake is surface mounted to it and could still poke a hole in it if it landed wrong. Just a precautionary measure. Besides, I think I may have used 100# stock instead of the 110#. That would be my bad.

Yeah, that big tranny puts it in perspective now, eh? OH, going to use that Yoplait container in a build? You could make a tranny out of that. If you only knew how many people use stuff like that to build rockets, you'd be amazed. Just ask Scotty Dog. He does it all the time.
 
Last night I stuffed the forward tranny with Great Stuff around where I needed it. I also got the fins and strakes cut, capped off the gap in the top of the big tranny and spread a dollop of Bondo on the aft tranny.

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Today, I started digging at the forward tranny. Seems like a lot of foam in there but I didn’t know how much expanding it would do. I carved some of that out, then used a ½” dowel wrapped with 60 grit and went at it. Once I got it close, it was all about, sand & fit, sand & fit, sand & fit. I finally got the result I was expecting and it hardly weighs a thing. At least the gaps are filled and a little Bondo should finish it of nicely after installation.

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Nifty work with the foam there; I never played with that stuff before. That transition looks great.

I'm having a hard time finding suitable heavy 11x17 paper for my big transition. Bought some "posterboard" at Michaels (unspecified weight) and it's definitely too light. If I can't come up with something better I might have to double it (that'd be fun) and I'm planning a balsa frame underneath for support. That is only one of several oddball strategies I'm planning for this... should be a very "interesting" build. In the meantime I shall continue to enjoy watching yours come together.
 
Nifty work with the foam there; I never played with that stuff before. That transition looks great.

I'm having a hard time finding suitable heavy 11x17 paper for my big transition. Bought some "posterboard" at Michaels (unspecified weight) and it's definitely too light. If I can't come up with something better I might have to double it (that'd be fun) and I'm planning a balsa frame underneath for support. That is only one of several oddball strategies I'm planning for this... should be a very "interesting" build. In the meantime I shall continue to enjoy watching yours come together.

Neil, just drop by Wally World, and get some of their poster size board (heavier than 110#). I'm sure you'll find a use for the rest of it some day. Basically print the tranny on copy paper, cut and piece the 3-4 pages of shroud parts together with tape and transfer by tracing on your stiffer board. It would be wise to cut the tranny out on the inside of the lines you drew. It might come out a bit too large. The sticker on the p-board says, "Ghostline Poster Board" and the bar code number is, 79784 92052. The weight is unspecified there also. Just picked this up last week.

Hopefully I'll have some more pics to post this evening. Most of my work has been priming these other 4 rockets I have going.
 
Having touched up the Bondo joints and little critical areas, I got the slots cut. Can’t say I’m any good at those, but these were better than others I’ve done. CAD said I needed 4 3/32” length slots, so for safe keeping, I made them 4” so I could trim if necessary. Every thing is still dry fit until I can commit to the glue with confidence.

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OH MY! WTH!!?? Something lied to me. That or I just plain screwed up. Look at that gap at the top of the fin, ERRRRR! OK, so I do have options. I went ahead and glued the big tranny in place. I needed to do that for any and all future adjustments. Maybe the fin isn’t sitting flat on the airframe, maybe the fin is too long. I’ll find out tomorrow after the glue sets

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SO, now you can see why I have to approach this the way that I am. The other day I screwed up and glued that big CR in place which totally blocks any internal view of my glue joint to the fin and applying fillets. I wanted to do that after I got the fins in place for easy access. So a little brainstorming came up with cutting peep/glue holes in the big CR. I can also make sure my fin root is solid to the airframe. After gluing the fins on, I’ll drizzle some glue in the holes on the aft part of the fin joint and use a long swab to form the fillets. Somehow, there must have been an easier way to do all of this. I just didn’t see it.

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As predicted, the fin roots were not making great contact with the airframe. I cut the tips down a little at a time until I knew I’d have to sand off some of the trailing edges. Not much was taken away to accomplish a good fit, so I glued them in place. Without those peep holes, I’d have been f….. uh....screwed. Those holes won’t matter at all since I’ll glue them back in place and all will be covered with the aft tranny. OH, and I also thought it wise to install the motor mount as well.

Just so you know, there were no jigs or fin alignments tools I could use except that well seasoned eyeball. For me, that’s really easy since I rarely use an alignment jig anyway. Normally I shape the fins before an installment, but in this case, I figured it best to shape the leading and trailing edges after the matter.

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Looking very nice. Seems like getting the big tranny and main fins in place is really the key milestone with this build. What thickness of wood is that BTW?

Neil, just drop by Wally World, and get some of their poster size board (heavier than 110#). [...] The sticker on the p-board says, "Ghostline Poster Board" and the bar code number is, 79784 92052. The weight is unspecified there also. Just picked this up last week.
I got some plain white posterboard from the same brand; it seemed (from feeling the packages, anyway) to be the same weight as the Ghostline. Definitely heavier than the previous stuff I got, though I'm not sure how much beyond 100 lbs it is. In any case it shall have to do.

Mine has one glossy side. Which side goes out? I guess shiny side out for smoother painting surface? I'd think primer oughta stick to it OK.
 
Looking very nice. Seems like getting the big tranny and main fins in place is really the key milestone with this build. What thickness of wood is that BTW?

It definitely is. Especially since my CAD drawings are on a zero line thickness, and nothing really is on this build. Never ran into so many flaws in my drawings before. I used 1/8" balsa. In fact, most of my rockets get that thickness.


I got some plain white posterboard from the same brand; it seemed (from feeling the packages, anyway) to be the same weight as the Ghostline. Definitely heavier than the previous stuff I got, though I'm not sure how much beyond 100 lbs it is. In any case it shall have to do.

Mine has one glossy side. Which side goes out? I guess shiny side out for smoother painting surface? I'd think primer oughta stick to it OK.

Personally I never have issues with glossy side out. My paper isn't like that here, but I have dealt with it in the past.
 
Earlier today, I did my glue drizzlin’ through the peep holes and that worked out very good. I’m holding out on putting fillets on the fin/tranny area because the muscles will provide all necessary strength I’ll need there. Now it was time to install the BT-80 section. Up until now, there was no need for a “lug alignment” tool, but all that changes now. Everything all the way down to the last lug will get the alignment tool. That would be a ¼” dowel. It was wise for me to mark the entire airframe with a lug line because it 2nds as a dowel guide. Everything was prefit & glue, prefit. & glue, keep that dowel straight and keep on truckin’. Once I got all the trannys in place, I gave it a few minutes or so, to set up a bit so I could do a preliminary fit with the lugs. Slid those in, ran my dowel and did the last second tranny adjustments. Sounds like a lot of overkill work for this application, but there are a couple of things I have to consider. Nothing has gone as planned with this build and I’m getting older by the minute. Tomorrow, I’ll get the aft tranny & lugs in while all of this dries overnight. It’s finally coming together.

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Gary- it's neat to see some craftsmanship go into an original design.l Brings back the excitement and joy of my earlier rocketry days! Kudos to you,brother- that looks like an awesome machine! You have got to get a picture of the smoke trail that's gonna leave! Nothin' but props for an old school rocketeer! Straight smoke and good chutes!
 
Gary- it's neat to see some craftsmanship go into an original design.l Brings back the excitement and joy of my earlier rocketry days! Kudos to you,brother- that looks like an awesome machine! You have got to get a picture of the smoke trail that's gonna leave! Nothin' but props for an old school rocketeer! Straight smoke and good chutes!

Thanks fyr. It's designs like this that challenge a persons skills. I don't care how much attention I gave the initial drawing, this bird kinda took on a path of it's own. I've made a dozen modifications already, and I know of a few more on the way. I sure hope no one ever wants to kit this up. It would take a top shelf genius to produce accurate building instructions. At least this one is being built with strength in mind. Very unlike the prototype.

And FWIW, I prefer this kind of building instead of pre-cut fins, tubes, and all the simplicity that goes in most of the MPR & HPR kits. It's all very much like the difference between a good homemade banana pudding, and what you might find available at the deli.
 
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