If you assume a spherical cow then there is no fin setup that can give
a constant roll rate other than 0 for any accelerating rocket. An
ideal fin tab or canted fin will spin the rocket through the air at a
constant "thread pitch", nominally with 0 spin rate at launch and
apogee and maximum spin at maximum velocity, though in reality inertia
would slow the spin up and spin down.
On Sun, Jul 17, 2016 at 1:29 PM, William Claybaugh
<wclaybaugh2@xxxxxxxxx> wrote:
Yep, supersonic. Still interested in a non-canted fin solution theory, if
any one knows of one.
Bill
On Saturday, July 16, 2016, Ben Brockert <wikkit@xxxxxxxxx> wrote:
I imagine your rockets go supersonic, so you'd be better off with a
canted fin (or a trim fin at the end of a fin) than a trailing edge
fin tab due to the change in behavior of a trailing edge control
surface in the transonic and supersonic regimes.
On Sat, Jul 16, 2016 at 11:37 PM, William Claybaugh
<wclaybaugh2@xxxxxxxxx> wrote:
I'd be interested in a theory to describe this problem. My own interest
is
in using fin tabs to assure spin at a specific rate (9-10 hertz), which
appears--to me--to be cheaper and more reliable than trying to carefully
align the fins to just the correct offset. Aligning them dead straight
and
using a fin tab appears to be much simpler....
Does anyone know of such an analysis?
Bill
On Saturday, July 16, 2016, Ben Brockert <wikkit@xxxxxxxxx> wrote:
Gary Cooper posted this to the FAR facebook page, though he's flying
in northern California:
https://youtu.be/I-FhXvLtk-U
A homebuilt motor that appears quite reliable, and trim tabs on the
fins to get rid of the tiny amount of roll the rocket was doing.