3" 2 Stage -- Alpine Style

Springboarding off of last summer's "build light" tangent I took, which culminated in a July trip to Argonia flying an aluminized 17500ns full N motor in a 4" rocket with 1/8" G10 fins and no layups, built from scrap parts that worked great (build thread found here: https://www.rocketryforum.com/showthread.php?55965), I've now moved to Texas, and am pairing my newfound easy access to decent waivers with my distinct lack of two other things -- time and money -- to continue this chapter of builds.

The name is pretty indicative of it all, stolen from my other hobby, high-altitude climbing. The parallelisms are evident -- the old-style approach to climbing involved a massive amount of equipment, investment, logistics, and preparation; featuring large teams moving slowly and methodically up the mountain, often requiring an exhaustive effort just to get all of that stuff to base camp, not to mention the slow-moving nature of those climbs often required an unrealistically long weather window.

The Alpine Style approach, pioneered in the 80s, kinda fits with my general mojo and the goal of these projects -- pack light, get up and get down in the shortest time possible, thus minimizing risk and exposure, emphasize skill and common sense over preparation, planning, and stiff-set rules, and don't invest so heavily in one route up the mountain that you can't easily change gears to adapt to the circumstances as they become known. So, last summer's hypothesis proved correct, so far -- that perfectly aligned fins and solid knowledge of basic bonding technique trumps the need for the cheap insurance that thick fin stock and heavy layups provide; but we're going to push the envelope further this time with the speeds that the sustainer of this one will reach, and it may well not work. But, the investment of time and money won't be significant enough that committing to this direction will be a major setback in the event of a failure. Many iterations are a far more complete learning experience than one slow, expensive, all-consuming project that commits one's time and finances heavily to one design tangent.

Anyway, enough babbling. I don't have my mixing stuff or tools with me, and spend most of my time working these days, but bought a few cheap tools from Harbor Freight, enough to do basic construction. I've been lucky enough to be granted use of others' mixing equipment on occasion. The formulas the group has chosen for mixing aren't the best for our purposes (ISP is key), but will suffice and beggars certainly can't be choosers. So, I've got 2 7600s mixed and ready to go, and will begin construction in a few days of a basic 3 inch 2 stage using parts and electronics I have available. The methods will pretty much mirror exactly what's shown in the previous thread, and hopefully just be another notch in the belt of the Alpine Style concept. Shooting to fly July 12 in Argonia, same place and time as last year, and hit around 40k.

Follow along if you wish.

Regards,

Prophecy

Subscribed.

me too!

prophecy said:

The Alpine Style approach, pioneered in the 80s, kinda fits with my general mojo and the goal of these projects -- pack light, get up and get down in the shortest time possible, thus minimizing risk and exposure, ...
Prophecy

Click to expand...

Ah, so you're omitting the recovery components in order to lighten the load and decrease exposure time:wink:. Very creative thinking!

Looking forward to watching this one develop!

-Eric-

Subscribed!

With reference to your other project (super interesting read btw - thanks) how fast do you think the 98 with no layup went?

Zebedee said:

With reference to your other project (super interesting read btw - thanks) how fast do you think the 98 with no layup went?

Click to expand...

Around m1.8. As mentioned there, I went with a pretty slow propellant and a progressive geometry to a.) to take it easy on the fins and b.) maximize altitude with a longer burn time and a configuration that accelerates once it's up in thinner air.

Alright! I'll be following along. I hope to be at that same launch on the 12th but with only one 3" rocket and only one 7600 ex load, but I'm also hoping to hit close to 40k. See you there.

Manny


Sent from my iPhone using Rocketry Forum

I've never had a shread on a single-stage flight. However, I have had problems, more than I'd like to admit, on two-stagers. My belief is that the reason for this is that a two-stager is likely to be moving at higher speed for a longer period of time. Thus, lots more time for the elements to find that weak spot and cause problems. I advise folks to build their sustainers stronger than they would otherwise do for the same rocket as a single stage.

Jim

JimJarvis50 said:

I've never had a shread on a single-stage flight. However, I have had problems, more than I'd like to admit, on two-stagers. My belief is that the reason for this is that a two-stager is likely to be moving at higher speed for a longer period of time. Thus, lots more time for the elements to find that weak spot and cause problems. I advise folks to build their sustainers stronger than they would otherwise do for the same rocket as a single stage.

Jim

Click to expand...

Jim,

Yeah, same thing happened with the one other time I tried a 2 stage at Balls a few years ago. 3" to 3" with a 7600 in the booster and a 10,000 moon burner in the top. In second 6 of the 8 second sustainer burn it gave up the ghost. Motors are uber slow here, and who knows, I may wimp out and put on one layer of something. But I'm inclined to give it a try in pure form and see how it goes. Any plans to go to Argonia this summer? Also -- I spoke with Thomas at TRA Las Cruces about a July trip out there. They're gathering interest in applying for a 75k waiver for that weekend, if you've got any plans to fly high pre-Balls.

P.S. I've been meaning to get in touch with you about Balls arrangements, like we spoke about at Hearne a few months ago.

Steve

prophecy said:

Jim,

Yeah, same thing happened with the one other time I tried a 2 stage at Balls a few years ago. 3" to 3" with a 7600 in the booster and a 10,000 moon burner in the top. In second 6 of the 8 second sustainer burn it gave up the ghost. Motors are uber slow here, and who knows, I may wimp out and put on one layer of something. But I'm inclined to give it a try in pure form and see how it goes. Any plans to go to Argonia this summer? Also -- I spoke with Thomas at TRA Las Cruces about a July trip out there. They're gathering interest in applying for a 75k waiver for that weekend, if you've got any plans to fly high pre-Balls.

P.S. I've been meaning to get in touch with you about Balls arrangements, like we spoke about at Hearne a few months ago.

Steve

Click to expand...

I have some data for you. Send me an email or a PM with your email address and I'll fill you in.

Jim

Ok, managed to sneak out to the "shop" (collection of cheap tools in the corner of a flooded apartment garage) for about two hours over the weekend and get the three sustainer fins cut. Going to build the entire first stage first since I have enough parts for that one lying around without having to reorder and it's unclear whether or not my ARTS (necessary for the 2 stage flight) will be repaired in advance of 7/12 (and having the two stage ready to fly sans electronics would kill me). Only took a picture after the first one was cut; the other two look exactly the same (roughed on a bandsaw, edged and beveled on a bench top sander).

In my allotted two hours this coming weekend, I should be able to get them tacked on and get the fillet rotation going. Build the nosecone/av bay combo the following weekend and that should be a wrap for the sustainer.

Finally got out to good old storage unit #58 today and spent about 6 hours taking a chunk out of this thing. Amidst the screaming kids running to and from the complex pool, I managed to get some stuff done and am pretty happy with how it all came out seeing as it's been a year since I last did this stuff.


Last weekend's progress -- three fins cut, edged and beveled




About half of today's project was roughing the crap out of all the parts to be bonded, 'cause that's the key to this whole concept. Starting with the fins -- taped off an area to be sanded (because I tend to get overzealous), started out by doing 60 grit parallel to the root of the fin and then used a technique I discovered last year to do perpendicular sanding (which is the direction that needs to be best prepared as that's where the stress will be) -- I touch-sanded it on the rump of my benchtop belt sander, which gets some nice deep scratches in there -- certainly cringeworthy to the "bond composites the professional way by activating it with fine sandpaper" camp, probably enough to give 'em an aneurism, but I write ads for a living and do this crap for fun, and it's worked for me every time I've done it. If it ain't broke...

Finished up by cutting notches in the root of each fin on the bandsaw.

Next up, of course, the airframe. Before gluing the fins on is also the last chance to square up the edges of the airframe if necessary. The rough cut from the factory had some steps in it, but alas, I had no chop saw with which to square it up. So we did the best we could with a bench sander. Came out pretty well given the circumstances and the show goes on.





Next, back come the tape guides, but this time for the airframe rough-up. Going to mount the fins 3.5" from the bottom of the airframe (I always do a twinge over 1 caliber) so we'll rough up +0.5" on each end of the fin root.



Again, we started out with 60 grit and then went to town with an old sawzall blade, getting some nice crosshatching action and an awesome palm blister.

Then it's time to mark the fin locations. It needs to be pretty much spot on for this concept to work, but no fin guides, protractors, or fancy stuff, just a piece of plywood on two sawhorses and curious onlookers walking by on a nice summer day. So, a tape belt around the circumference, measured and marked for three fins and a rail button line, starting out with dots:

Then we take an angle iron and run a pencil line through each dot.

Then, back to the "faux slot" method for tacking the fins on. Worked awesome last year. Mimick a slot by taping popsicle sticks around where the fin will go, that way you only need to eyeball one axis when you hold it in place for 5 minutes while it cures.



And a 1:





(the old drill press box made an awesome stand!)

And a 2:



And a 3:



And then it's time for the Proline 4500 fillets. Had to run out and buy a scale, but of course the cheapest scale at Walmart only measures in pounds and ounces, with .1oz resolution. 100:16pbw, so working in tenths of an ounce...2.5oz resin to .4oz hardener.



Closeup shows the epoxy leaking into our gouges nicely -- just what we want -- eat your heart out, chemical bond folk...



So tomorrow morning I'll do the second side, and the third side tomorrow evening, meeting this weekend's goal of getting the fins mounted.

A sore back, some suspicious neighbors and an angry girlfriend later, we're finally somewhere on this thing.

Prophecy

Knocked out the other two fillet sets today, just got in from doing the last one. Fincan is all done minus rail buttons. Good weekend. Next weekend - nosecone/av bay.

Great work mate! I will be at the July 12th launch so I look forward to seeing this. I am hoping to have my bird all ready to by then.

Mat

Good morning, all -

Chugging right along here. Got the nosecone/av bay assembly done this weekend, so all that remains is the inevitable "random loose ends that should take half an hour and end up taking half a day" part of a build that every rocketeer has experienced. Got pictures of most of the steps, though not all. This is a clean and simple solution to putting electronics in the nosecone I've been doing for the last five years or so, ever since I started using a line cutter and happily ditched the allthread/ubolts/payload section mess.

First step is to cut the tube we're going to sink in the cone to length. In the shop till you drop tools trip at Harbor Freight, I had to pick between a chop saw and a bandsaw to fit the budget, and went with the bandsaw as I felt it was more versatile. But, it only has like 10" of depth on the cut and we needed a 12" piece. So, out comes the trusty keyhole saw:



The blade was pretty dull from last week's roughing up adventure, so it took a little longer than anticipated and the cut was a little messy. Benchtop sander to the rescue:



The tubing I was using is oil pipeline that was made out of spec for a job, exactly 2.0" OD. One of the guys at WTR works in an oilfield and scored the bad batch, and showed up to a launch with an entire truckload of it. Great for making little 2" single-use motors, and av bays, I guess. The bonus is that a 2" hole saw is a drop in fit for cutting rings for this stuff:



And the inside, too:

Random glory shot of the $6 hole saw and the $60 drill press:



Then it was time to sink four nuts in the back of the centering ring:



And tack it on to the end of the tube, also locking the nuts in place. Also see the sled cut and sanded to fit in the background. Fit to be sandwiched in between the tube cap and the bulk plate that screws into the centering ring, eliminating the need for allthread:



And then plug the hole from the hole saw in the tube cap with JB Quick Weld:



And finally, fillet the ring. Fillet needs to be strong on this side as it's mounted flush to the other end to allow the bulkhead to seat and won't be filleted on that side:

Not shown is gluing the shoulder into the nosecone, and then gluing the assembly into the nosecone. It's pretty much all set now.

List of annoying, random tasks to complete next weekend:

1. Mount rail buttons
2. Mount eyebolt and drill wire hole in nosecone bulkplate
3. Mount altimeters and battery hole patterns in sled
4. Drill shear pin holes
5. Drill pressure bleeder hole
6. Drill vent hole/arming hole through nosecone and av bay tube

Then we should be good to go-got my flights approved by the Kloudbusters BoD this morning, getting ready to go.

Aaaaalrighty then, chugging right along. Butalane and I swear that if we were building Wildman kits and flying them on CTI motors our projects would garner more interest.

Anyway, I'll be traveling for the weekend of the 4th and the launch is the weekend after that, so I had to go ahead and get this finished up this weekend. We've all been there; the rocket is basically done, you're kinda over the build, but there's a never-ending list of random loose ends to tie up that ends up being a whole heap of work.

First was to mount a forged eyebolt in the nosecone bulkplate. Whoops, my neighborhood Home Depot doesn't carry them and it's not worth spending a few hours searching various Mom and Pop shops for one. Usually a u-bolt would be my fallback, but when the whole rocket weighs something like six pounds, it just feels so wrong to put a hunk of metal in there to serve such a mundane purpose as a recovery hardpoint. Let's see if we can't come up with a more elegant solution:



Now, for the line cutter. I went to the shooting range the other weekend and saved a few of the 9mm shell casings to make in to line cutters. A quick note on these - Tony A. pioneered the current application of the shell-casing line cutter on the TQC message board maybe five or six years ago. A good friend of mine makes gorgeous ones on his lathe and sends me some each year for Balls, always refusing to take payment. Over time, they go missing; this most recent pair went missing with last year's Balls project. I hesitate to ask more than I need to; so for filler projects like this I aim to make my own. It kinda feels wrong to me that people have commercialized this idea and I hesitate to buy into that notion, and I have no machine tools to make nice ones myself, so I hack away and make ugly ones that work. First step is to drill a 1/8" hole for an ematch in the bottom of the 9mm casing.



Next, drill a lateral hole for a ziptie:



And then we need to search the aisles at Home Depot for something to act as an insert. We hit on the first aisle:

We then need to hack a hole through this, and then put a screw in the top so I have something to tether it back to the shock cord so it's reusable. Ugly, but it'll work:



Then, we'll drill holes and sink nuts into our little fiberglass plate to hole the shock cord in place:





All together now, looks pretty clean and sharp:

Then we mounted the rail buttons. After that, it was time to drill a bunch of holes. We've all been there; leaving drilling pressure bleeder holes/vent holes/shear pin holes etc. till it's time to launch. When done in haste, I always seem to get unlucky somehow; oops! Arming hole is right against the rail! Etc., and so on. So, I'm now anal and map this stuff out obsessively. We'll make this easy and extend our fin mounting lines for the three shear pin holes, and extend the rail button line for the pressure bleeder hole. We'll drill the vent/arming hole in the nosecone and have the pin pattern such that it sits directly opposite the rail button line when pinned in. Then, I measured the nosecone shoulder; 83mm. So, we'll split the difference and mount the shear pins 41.5mm down from the lip of the tube. We'll put a ring of tape around the tube at this depth, leaving perfect cross marks between the tape and the pencil lines to tell me where to drill.



The drill press box returns once again as a convenient stand:





A perfect result:



All stacked up, looks fast:

Now time to drill a hole in the nosecone for arming/venting through both the nosecone/coupler and the alt bay tube. We did this on the drill press, using our Ikea screwdriver head set as a stopper guide to keep things square:



Came out nice:



Now we need to drill a hole in the nosecone bulkplate to allow both charge wires to come through. We've all drilled this hole in haste on the field and had to thread the wire through more things than necessary to compensate for the hole being in the wrong place. This needs to be in between the sled and the nuts for the shock cord mount, which are perpendicular to each other, so we etch a line at 45deg and drill away:



Now, time to lay out the av bay board. I had planned to go the discount route just for purity's sake and use one or both of my Missileworks RRC2+ and/or my Adept 22; but as an old-timer, I remember the days of setting Mach delays on Baro alts, and had been nervous about going to Mach 2 with a baro-only alt. A friend of mine flew one of these new Baro-only alts past Mach over the weekend and had it pop prematurely, so I'm going to wimp out and use a Raven. Time to lay out my sled for the Raven, brackets for the 9V battery, and leaving room for the tracker which will butt up against the bulkplate to allow room for the antenna to stretch up to the top of the bay. We had to nip the corners of the brackets to get em to fit:



And then we mark the holes for the Raven and these brackets:



And then mount the brackets:



All set:





So that's pretty much a wrap. I'll spend weeknights week after next prepping for flight #1 and then head on up to Kansas.

Thanks for following along if you did,

Regards/Prophecy

Good luck on the flight, look forward to hearing how it goes!

God I wish this rocket was flying on a commercial motor.

patelldp said:

God I wish this rocket was flying on a commercial motor.

Click to expand...

Te he he he. Steve, I'm following along! Thanks for sharing; I'll be watching for the flight report!

ECayemberg said:

Te he he he. Steve, I'm following along! Thanks for sharing; I'll be watching for the flight report!

Click to expand...

2,000mi driving and 2 all nighters later, I'm back at my desk - flew this on Saturday morning. Had it all prepped ahead of time, and had it on the rail around 11am. Boost was perfect - dead straight, not even the slightest wiggle (eyeball and popsicle stick fin alignment FTW!), motor hauled @$$ off the rail and burned for about 3.5 seconds. After losing tracker signal last year, I tested it this year a.) in the car b.) once in the av bay c.) on the rail and d.) after retreating to the flight line. Had a good strong beat every time, and did until about three minutes past apogee, at which point it slowly faded to black. Can't imagine the battery popped loose, because that would have been a sudden stop. I figured it had landed behind a bluff or something, so I drove in a 1, 2, and 4-mile radius square stopping at every high point for a signal. Nada. We later went out to 6 miles (Manny and Lance- thanks again for the help!) with a rooftop extended-range antenna, and still got absolutely nothing.

Unbelievable that this has happened two years in a row, and I'm tired of losing rockets that fly awesome after one flight. But, the definition of insanity is doing the same thing over and over again and expecting a different result. Next up are Airfest and then Balls, time to go after that HAM license and get a Telemetrum.

prophecy said:

2,000mi driving and 2 all nighters later, I'm back at my desk - flew this on Saturday morning. Had it all prepped ahead of time, and had it on the rail around 11am. Boost was perfect - dead straight, not even the slightest wiggle (eyeball and popsicle stick fin alignment FTW!), motor hauled @$$ off the rail and burned for about 3.5 seconds. After losing tracker signal last year, I tested it this year a.) in the car b.) once in the av bay c.) on the rail and d.) after retreating to the flight line. Had a good strong beat every time, and did until about three minutes past apogee, at which point it slowly faded to black. Can't imagine the battery popped loose, because that would have been a sudden stop. I figured it had landed behind a bluff or something, so I drove in a 1, 2, and 4-mile radius square stopping at every high point for a signal. Nada. We later went out to 6 miles (Manny and Lance- thanks again for the help!) with a rooftop extended-range antenna, and still got absolutely nothing.

Unbelievable that this has happened two years in a row, and I'm tired of losing rockets that fly awesome after one flight. But, the definition of insanity is doing the same thing over and over again and expecting a different result. Next up are Airfest and then Balls, time to go after that HAM license and get a Telemetrum.

Click to expand...

I'm with you on that sentiment.

"If it bothers you, don't let them push the button."

After losing a few altimeters over the past year after seeing the rocket land, I am never flying a sizable rocket without tracking again.

Bummer Steve. Looking forward to seeing what you have at Airfest.