-heavy. Simulation suggests that turning the nose out of solid pine would work
-out just about perfectly.
-
-Because such a heavy nose cone will put significant compression load on the rest
-of the airframe, we'll build internal structure to carry that load rather than
-depending on the airframe material itself. Some quick back of the envelope
-calculations suggest that 3 ribs made of cheap, common 1x2 pine lumber should
-more than suffice.
-
-The fins will be fabricated from nominal 1/2 inch birch plywood, rounded,
-vacuum-bagged with one layer of carbon fiber for stiffness and one layer of
-fiberglass for surface preservation and strength. They will insert into fin
-grooves cut in the forward and aft fin rings and interlocked with two
-intermediate rings. All fin to ring joints will be augmented with chopped
-fiber and/or glass fabric scraps. Once the fin can is fully assembled, an
-extra layer of fin to fin glass across the airframe will be installed to
-help keep the fin can together during landings.
-
-The airframe will be constructed from 12-inch concrete form tubing with the
-inner and outer layers peeled, wrapped with two layers of 6oz fiberglass. A
-section of airframe tubing wrapped with one glass layer will be slit and
-closed down to form a coupler so the main airframe can be built in two pieces
-to ease transportation and flight prep.
-
-Recovery will involve a 3-foot drogue parachute deployed by blowing the nose
-cone off at apogee, and an ARRD will be used to release a 28-foot main chute
-from a deployment bag. For high flights, a reasonable main deploy height for
-traditional "dual deploy" recovery will be chosen. For lower flights, the
-main will be deployed just long enough after apogee to permit the drogue to
-re-orient the airframe, approximating the "main out at apogee" experience.
-
-A side-access electronics bay will be constructed in the valley between two
-fins near the leading edge of the fins. Electronics will consist of one
-each Altus Metrum [TeleMega](http://altusmetrum.org/TeleMega) and
-[TeleMetrum](http://altusmetrum.org/TeleMetrum) boards. The TeleMega is
-overkill, but I'm curious to see what the airframe rotation rates are like
-in flight, and the gyros will capture that. Each will use a single 850mAh
-LiPo battery, and rotary switches mounted in the airframe for on/off. Two
-charge cups will be mounted on the forward ring of the fin can for apogee
-deployment, and an ARRD will be mounted on the other side of the same ring
-for main deployment.
-
-The main airframe tube will contain ribs and additional structure to carry
-the load induced by the nose cone, and to direct apogee deployment gasses
-around the main parachute deployment bag.
-
-Because the kinetic energy at ground impact even under the large main will
-be fairly high, the ring at the aft end of the airframe will be doubled
-to 1.5 inches thick for extra strength.
-
-The airframe will be set up with 1515-sized rail buttons, and use of
-Terry Lee's launch trailer with 20 foot rail is assumed to ensure stability
-for all flights.
+heavy. Simulation suggested that turning the nose out of solid pine would work
+out just about perfectly. And thanks to the fire, Bdale had some large pine
+logs drying... but trying to turn a nose cone out of one of those was kind of a
+disaster! So we ended up asking Dan at
+[Python Rocketry](https://pythonrocketry.com/)
+for help, and he delivered an outstanding bespoke nose cone for the project!
+
+Because such a heavy nose cone would put significant compression load on the
+rest of the airframe, we took notes from Kevin Trojanowski's large rocket
+group projects, and decided to build internal structure to carry that load
+rather than depending on the airframe material itself. Some quick back of
+the envelope calculations suggest that 3 ribs made of cheap, common 1x2 pine
+lumber would more than suffice.
+
+For the airframe, we acquired a length of 12-inch concrete column form,
+peeling the inner and outer layers to get rid of the waxy surfaces. The
+tubes were then wrapped with two layers of 6oz fiberglass using West Systems
+epoxy and peel-ply fabric to consolidate the fibers and make for a reasonably
+smooth finish with minimal sanding. A section of airframe tubing was slit and
+closed down to form a coupler at the front of the fin can, so the main
+airframe can be separated to ease transportation and flight prep.
+
+The fins were fabricated from nominal 1/2 inch birch plywood with rounded
+edges. They were inserted into fin grooves cut in the forward and aft
+centering rings and interlocked with two intermediate rings for mechanical
+strength. All rings were CNC cut from 3/4 inch birch plywood, except the
+aft ring which was doubled by laminating two pieces of plywood to form a
+1.5-inch-thick aft ring more likely to survive the kinetic energy of
+landing. The epoxy used for all fin to ring joints (and most others in the
+airframe) was augmented with West Systems 403 Microfibers, yielding very
+strong yet light joints. Once the fin can was fully assembled, the fins
+were laminated with with one partial layer of 5.7oz 2x2 twill carbon fiber
+for stiffness, and one layer of tip to tip 6oz fiberglass for surface
+preservation and strength.
+
+Charge cups for primary and secondary black powder charges mount on the
+top of the fin can forward ring where they are easy to load before adding
+the main airframe tube to the stack. This ring also sports an ARRD
+intended to release the main chute during descent. The main airframe tube
+has 3 ribs epoxied to the inside of the skin that sit on the fin can forward
+ring after assembly, and provide a bearing surface for the nose cone once it
+is installed. In this way, the compressive load from the nose mass carries
+down through the ribs into the fin can plywood stack, and no significant
+load is carried by the aiframe tubing itself. The main airframe also has
+a "baffle" between two of the ribs that causes the gas produced by the black
+powder charges to flow up past the main parachute to blow off the nose cone.
+
+Because the nose ended up being really heavy after adding sufficient nose
+weight to stabilize the airframe on big motors, recovery starts by blowing
+off the nose at apogee and deploying 2 mil-surplus 5-foot parachutes on
+a "V" harness. The main chute is a 28-foot man-rated mil-surplus chute in
+a Giant Leap deployment bag, and the harness is fabricated from lots of REI
+1-inch climbing strap (in bright purple, of course!) and a number of
+different size stainless steel quick-links.
+
+A side-access electronics bay in the valley between two fins provides
+space for two removeable "sleds", each holding an Altus Metrum
+[TeleMega](http://altusmetrum.org/TeleMega). Each TeleMega has a single
+dedicated 850mAh LiPo battery, and a rotary power switch mounted in the
+airframe for on/off. Custom dipole antennas were designed and integrated
+into the construction just inside the airframe skin to maximize telemetry
+performance, with RG-188 teflon coax and SMA connectors to the flight
+computers.
+
+The airframe is configured with two 1515-sized rail buttons, and is really
+only considered safe to launch from Terry Lee's launch trailer with 20 feet
+of very stiff 1515 rail.