From a5d5ad3ef958f339129b95a46de311a83eec0f88 Mon Sep 17 00:00:00 2001 From: Bdale Garbee Date: Sun, 21 Feb 2021 09:34:02 -0700 Subject: [PATCH] start documenting V-2 build --- rockets/airframes/V2-8/index.mdwn | 79 +++++++++++++++++++++++++++++++ 1 file changed, 79 insertions(+) create mode 100644 rockets/airframes/V2-8/index.mdwn diff --git a/rockets/airframes/V2-8/index.mdwn b/rockets/airframes/V2-8/index.mdwn new file mode 100644 index 0000000..a24d934 --- /dev/null +++ b/rockets/airframes/V2-8/index.mdwn @@ -0,0 +1,79 @@ +# 8" V-2 + +## Motivation + +The [V-2](https://en.wikipedia.org/wiki/V-2_rocket) has a significant place +in the history of rockets, and Bdale always thought it would be cool to build +and fly a model of one. After learning how to make APCP research motors and +experimenting with Everclear (which has visible flame characteristics +reminiscent of the LOX and ethanol fuel used in the original V-2) the +idea became even more appealing. + +And then, [Composite Warehouse](http://compositewarehouse.com/) put their +[8 inch V-2 kit](https://www.compositewarehouse.com/index.php?route=product/product&path=18_70&product_id=158) +on sale during their Black Friday sale in 2020... and it was just impossible +to resist buying one! + +## Design Details + +This 8-inch diameter kit is all filament-wound fiberglass, with an +aluminum-tipped nose cone and 98mm motor mount. A short coupler section is +provided to attach the pre-slotted tail transition section to the main +airframe tube, and a longer coupler section is provided to double as the +nose cone attachment and electronics bay. Beautiful, thick, stepped glass +bulk plates with central 1/4-inch holes were included to enclose this bay. + +When the kit finally arrived in mid February 2021, the parts all seemed to be +of outstanding quality, and the coupler sections in particular showed up in +thick-wall glass that seems really robust. An hour or so of fun involving +a bathtub, a couple shop towels, warm water, and dish soap cleaned everything +up and eliminated the residual fiberglass dust on all the parts in the kit. + +Further examination showed that there was one minor problem. The aft +centering ring's inside diameter was fine, but the outside diameter was +smaller than the opening at the aft end of the fin section. It wasn't a +grossly un-usable part, and the gap could have been addressed by using some +small balsa shims to center the ring in the opening and sufficient epoxy with +fiber filler to close the gap. But, since a CNC router was available, the +decision to fabricate a custom replacement aft ring with precisely positioned +mounting holes for an +[Aeropack 98mm retainer](https://aeropack.net/motorretainers.asp) +was easy to make. The ring was cut from 1/2-inch birch plywood, stepped with +about a 1/8" lip to the outside diameter of the glass, and 12 holes the +correct size to directly tap for a #8 screw thread. The point of the lip +was to make assembly easy. With the machined lip, the ring could be epoxied +in place by itself but still assuring axial alignment. The part was designed +in [FreeCAD](https://www.freecadweb.org/) and cut on Bdale's +[Probotix](https://www.probotix.com/) Comet CNC router. + +## Design / Simulation File + +## Construction Log + +2020.11.22 +Kit ordered during Black Friday kit-buying spree. + +2021.02.17 +Kit arrived! Fun in the tub cleaning up all the kit parts. Dry fit various +bits to get a feel for how it should all go together. Discovered aft +centering ring OD too small, reported to kit seller not asking them to take +any action since I want to make a custom replacement anyway. + +2021.02.19 +Built up an [OpenRocket](http://openrocket.info/) model of the airframe, +except that using the latest released version, 15.03, it's not possible to +model the fins correctly. The fundamental issue is that this version of +OpenRocket doesn't support fins on transition sections. Several work-arounds +were explored, but the net effect is that Bdale needs to package a fresher +version of OpenRocket for [Debian](https://debian.org) despite the lack of +a new upstream release, since it appears this deficiency got addressed sometime +since the 15.03 release. + +2021.02.21 +Designed and machined replacement aft ring, located the unused 98mm Aeropack +retainer already on hand. + +## Photos + +## Flight Log + -- 2.30.2