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A4 (V2) for my L3
I'm here at one of my thrice weekly sitting in the lobby of the natatorium for an hour and a half sessions, so may as well update the build.

I prefer to cut my own CRs and bulkheads, and with my largest previous project being 4" diameter this was accomplished with a Harbor Freight fly cutter and Drill too can build cool rockets with crappy tools, and it leaves more motor money which I am going to need. These rings are mostly beyond the limits of these tools, so I needed new tools, or a workaround. I searched the here and the rest of the interwebs and came accross a couple good adjustable jigs for circle cutting with a bandsaw (got one) and sanding circles on a disk sander (got one). I also have a copious wood scraps bin(s), so the total investment in the below jigs was about $1 in screws, and a few hours time. All of the CRs and bulkheads for this project will be made or modified using these two jigs.

Band saw Cutter:

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Sanding Jig:

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The bulkheads are cut a touch big on the band saw jig, and then sanded to a tight fit on the sanding jig. For CRs the center hole is then cut with the fly cutter using the central pivot hole needed for the jigs to guide the bit (they are the same size, not by accident). The Sanding jig also allows for nice control over angled edges for the NC and boat tail CRs.

Crappy drill press and fly cutter...gets the job done, eventually.

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I did grab a few commercial CR's from the stash, but there are no standard size rings in this project, so they will need to be sanded to fit. To do this I made a plug bulkhead out of some scrap to guide the shaping.

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Starting the Nose Cone

First up, gotta cut the base off. Marked the line, made a notch with a dremel and cut it with a Zona saw.

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There are two very different CRs for this section, both were made from high quality 3/8" Baltic birch ply.

The fore ring is to hold the inner tube, and to act as a mount for the bulkhead and adjustable nose weight. It has a groove cut into it (made with fly cutter and about 1/8" deep) to set the tube in, the edges are angled to match the contour of the NC and there are 6 holes which match up to the bulkhead.

The aft ring is more straight forward, but also contains a 1.25" hole to afford access to a tracker bay.

Both rings had 8-32 T-nuts epoxied (5 min) in place for Tracker plate and bulkhead retention down the line.

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The tube was epoxied into the CR groove using Aeropoxy structural (this will be the main structural epoxy for the entire build).

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This was test fit into the nose, and a flashlight dropped into the tip. This allowed for a dashed line (hard to see) to be drawn around the NC showing the CR location. The fore ends of the T-nuts were taped over to prevent epoxy sneaking in and the tube epoxied into the roughed up NC usingf Aeropoxy with milled fiberglass added to thicken it. The Aft CR was put in place to ensure center, and 3/8" brad nails (x12) were were put through the NC into the fore CR.

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After the Aeropoxy had began to set I poured in a 12 g batch of US Composites 635 (Medium) laminating resin to create a "fillet" between the NC, ring and tube.

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This brings us to the end of swim practice, and as such, the end of this evenings updates.
rharshberger;1508124 Wrote:Nice jigsSmile

I would think you'd like them.  The Band saw one is basically a hybrid of your scroll saw jig and the below chap's band saw jig.  While the sanding jig is essentially my kludged ripoff of your jig.

These thing really do work great, and are remarkably easy to construct.
So I find myself with another hour of sniffing chlorine and sitting.

So the entire point of making that internal tube in the NC was to allow for a tracking bay between the tube and NC wall. If you look back at the NC rings you see that the large ring for the base has a 1.25" whole in it to allow for access. To make the plate that will go over this an additional CR was cut out of 1/4" Birch ply and sliced into multiple covers. One of these was mocked up with the tube, taped in place, the retention holes drilled through both ring and plate, and the access hole marked.

A sled was made from a scrap of 1/8" Birch Aircraft Ply. The sled will be held to the plate by two pieces of aluminum angle, that were cut and mounted to the sled. The bracket then got a trip to the bench grinder to make it fit the access hole. Once attached to the sled the unit was dry fit, and the brackets bent so that the sled angles roughly parallel to the NC, so there is no pressure on the antenna.

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The entire thing has been mocked up in the NC, but that is hardly photogenic. The moral: it fits.

The astute observer will notice these are not the correct rings pictured earlier. These were made from scrap bin plywood to test this idea out before I started cutting the good stuff.
The smell of chlorine means it;s time to update the thread. I've made a lot of progress a half-hour here and an hour there.

After roughing up the inside of the NC with some 80 grit, the aft CR was glued into place using Aeropoxy thickened with milled fiberglass to keep it where I wanted it. Another dozen brad nails ensure another level of mechanical bonding with the NC. The Aft CR was positioned to allow about 3/16" of the inner tube to project past. This lets the tracking bay plate be fully recessed when screwed in. Lastly, external (if that makes sense) fillets were applied.

A piece of 1/4-20 all thread was cut so that it extends almost to the NC tip when passed through the forward bulkhead. This will be the rod that holds the adjustable nose weight, and is held on the fore side of the bulkhead by a washer and wing nut (the weight will go between the bulkhead and the washer). On the aft side of the bulkhead the rod will be held with a stainless steel oblong lifting nut, which will serve as the shock cord anchor point.

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Dipstick;1508897 Wrote:Looking nice! One thing I learned when building my own 7.5" V2, use the Rocksim method of CP, apparently it's more accurate in models like the V2 with large curvy sections that adds more fin area down the boat tail. I initially added noseweight to match barrowman and ended up not needing it which really restricted performance...

Definately. If you look at the build diagram pic I posted it shows both values. I did that for completeness only, I will definately be baseing my CG on the Rocksim calculation. Also, the Rocsim calculation of CP better agrees with the suggested CG for several V2 kits, so it has been real world tested also.

I think to achieve the 1 cal over the Barrowman CP in the nose weight space available I would need dark matter or stellar core material, and I can't find a commercial supplier of either.

Nose weight limiting the available motors is really what led to the adjustable nose weight option, and trying to push all the "stuff" as far forward as possible. After finishing out the NC at just a touch over 3 lbs (pictures next swim practice) and having all the bt parts weigh in under 4, I'm getting hopeful I can get this thing in around 15 sans motor and nose weight. That would provide a really wide spectrum of motors, so I'm focusing very closely on managing weight...the rocket, not mine.
An afternoon distraction post.

The main bulkhead for the electronics bay is going to include a lot of stuff. This bulkhead will be the attachment point for the drogue and main shock cords, as well as all the terminal blocks and charge wells, the altimeters, and of course the rods that tie the bay together. In other words, it's going to be really, really, really important to get that thing just right as almost every failure mode in the rocket is centered there.

The bulkhead was made from 3/8" Baltic Birch goodness. Some radial reference lines were drawn down on the bulkhead (fore side) 22.5 degrees apart, and myriad holes laid out and marked for size.

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Like I said, a lot going on here

There is a second bulkhead that matches the ID of the donut bay tube. This bulkhead was glued in place with some Titebond II, and a hardwood dowel also glued in at the same time for alignment. Once dried the dowel was sanded flush on both sides. The purpose of the small bulkhead is to help with alignment, and sealing from the drogue compartment.

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Lastly the holes all needed drilled, and some of these needed to line up with the donut bay aft CR, AND some of these pass all the way through the CR while others do not (more later on that). Back to my favorite building tools for this, tape and a cheapo Harbor Freight Drill Press. All done and pretty happy with the results.

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The holes that are shown in the tape picture do not extend into the CR, in other words, they were drilled prior to taping the two together.
All charges will be controlled by a pair of RRC3 altimeters. I know the thinking about using two different types/brands of altimeters, but I would rather go with the altimeters I have experience and comfort with. To me there is more of a chance that I will mess up with a new altimeter than the altimeter will mess up on it's own.

The best way to describe how the altimeters will be supported is with a picture:

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The altimeters are mounted to Missileworks 3D printed sleds (54 mm variety), and will be therefore supported by 2 rods. They will be held in place by lock nuts above and below on a single side of the sled, so that the threaded rod they are on can be screwed into the T-nuts in the aft CR once the bulkhead is installed (makes more sense when I get to the pics). This setup allows the altimeter, ematches, and charges to be completely prepared outside the rocket and the entire assembly loaded together.

The inner tube of the bay is a spare piece of 4.1" Magnaframe left over from my L2 build, Arapahoe-J (soon to earn a name change with a K-flight). The aft CR has 4 holes that do not go all the way through, into these was epoxied (5 min) 10-24 T-nuts. These will accept the threaded rod holding the altimeters. These do not have to pass all the way through as they will not be carrying the bulk of the load upon ejection, that will be handled by 2 pieces of 1/4-20 all thread. The roughed up magnaframe was then epoxied into the CR with Aeropoxy, a square was used to ensure that it was, well, square. The next day an Aeropoxy fillet was put on the joint.

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Before gluing the assembly into the rocket a test fit was in order, with and without altimeters. Note: I will either be mounting the magnetic switches differently in the finished rocket, or I will use rotary switches. Haven't decided, but the clearances are fine for either of these solutions.

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The all thread that the altimeters are mounted on have been turned into long bolts by the application of some red threadlock to the cap nuts that top them off. Note: every "permanent hardware attachment has some red threadlock in it.
With a good fit for everything confirmed it was time to epoxy the electronics bay in place. The aft CR needed to be 5 1/4" from the aft end of the bt. To accomplish this I went back to the scrap bin and cut a spacer from some pergola construction leftovers. The bay was epoxied in place with Aeropoxy, again thickened with milled fiberglass so it stayed where I wanted it.

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Once that dried I had to come up with a way to do the "internal fillet" as my hand was not fitting in there. I always keep a look out every year on lab cleanup day, and scoop up any expired or unwanted lab supplies that may be of use. Turns out an "expired" 5 mL pipet aluminum taped to a 30 mL syringe of a type no one in the lab likes works perfectly for injecting this fillet. An "aft fillet" was also applied, but that was pretty easy as it didn't require any tools other than a plastic spoon, so no pics.

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To better support the upper bulkhead a 1" thick ring of 7.5" phenolic was cut and notched to allow it to fit inside the bt. This was then epoxied in with some more fiberglass/Aeropoxy mix. The bulkhead was used to push this into place to ensure it was at the correct height all the way around.

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With that, the body tube is nearly complete. Rail button attachment and a bunch of holes to accomidate altimeter breathing, pressure relief and shear pins are all that remains.
Awesome! This thread is so cool I'm following it in two places. Big Grin
Junior L2!
Biggest motor of 2015- I284

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