## Design Details
-* 98mm [Performance Rocketry](http://performancerocketry.com) G-10 convolute glass air frame
+* 98mm [Performance Rocketry](http://performancerocketry.com) G-10 convolute glass air frame
+* 98mm [Performance Rocketry](http://performancerocketry.com) G-12 filament-wound glass couplers
* 75mm [PML](http://www.publicmissiles.com) phenolic motor mount
* [Shock Wave Rocketry](http://shockwaverocketry.com/) fiberglass 98mm Von Karman 6:1 nose cone
* custom fins, using 3/16 inch birch plywood laminated with carbon fiber
The TeleScience board supports connection of up to 12 NTC thermistors along
with other capabilities.
-Installing the electronics in the fin can bay was .. interesting. More later.
+Installing the electronics in the fin can bay is a *huge* challenge due to the
+restricted space between the MMT and airframe.
+
+### Fintenna ###
+
+On 2YikStik, one of the big disappointments was a very poor signal from the
+UHF transmitter on the TeleMetrum board mounted in the fin can. This isn't
+surprising, since the antenna was just a wire whip running in parallel with
+and very close to the motor casing. For this build, I decided to try
+something completely different.
+
+The quick summary is that I'm loading the two fins that don't have thermistors
+in them as an antenna. And it works brilliantly!
+
+Before bagging the fins with the CF and glass lamination, I put 1 inch wide
+copper foil tape on two of the fin substrates, running from near the tip
+down to the root. Then the fins were bagged with 2 layers of 5.7 oz 2x2
+twill carbon fiber and a 6 oz glass sanding veil layer on both sides, all in
+one bagging operation to ensure all the layers formed a strong chemical epoxy
+bond.
+
+After unbagging, while the epoxy was still somewhat leathery, I carefully
+cut the CF back at the root edge of each fin exposing the copper foil. The
+fins were then allowed to cure and get sanded normally. When installing them
+in the airframe, I oriented them so that the thermistor fin is on the anti-rail
+side of the airframe, and the two copper-foil-equipped fins bracket the rail
+side, with the copper foil sides facing each other across the rail-side valley.
+
+After applying fin to fin glass across the motor mount, additional copper foil
+tape was used to join the two fins, soldering the new foil to the foil embedded
+in the fins. I then cut a "gap" in the center of the space between the two
+fins, and installed a 1.5-20pF piston trimmer capacitor with the screw aimed
+aft, and a piece of small diameter teflon coax with two ferrite beads on the
+forward side of the gap. The coax was run through a hole near the root of
+the fin separating this valley from the ebay and terminated with an SMC
+connector to mate with the TeleMetrum board.
+
+I'm pleasantly surprised at how well this seems to work. With a Pro75 6xl
+case installed, the variable cap allows the antenna to be tuned to about 1.3:1
+SWR, and the resulting transmitted signal seems strong...
## Build
[Shockwave Rocketry](http://shockwaverocketry.com), with thermistors embedded.
The fins are 3/16 inch birch ply, tapered on the leading and trailing edges,
-then covered with one layer of 5.7 oz 2x2 twill carbon fiber and a layer of
+then covered with two layers of 5.7 oz 2x2 twill carbon fiber and a layer of
6 oz glass as a sanding veil, all vacuum bagged with West Systems laminating
-epoxy using a kitchen food saver appliance.
+epoxy using a kitchen food saver appliance. The two CF layers are rotated
+45 degrees from each other.
We're moving from the Giant Leap Rocketry 98mm Magnaframe-based Dynawind to
G-10 glass tubing this time around. Dynawind is lighter and strong enough,
All rings and bulkheads were cut using a CNC milling machine from 3/8 inch
birch plywood. The fin forward and leading edge rings are made from 3/4 inch
-thick assemblies made by laminating two such rings with wood glue, to provide
-sufficient depth for milled fin slots.
+thick birch plywood, mostly to provide sufficient depth for milled fin slots.
Will add a pointer to build photos here once they are available.
projects / web / gag.com / blobdiff