I have done much research about rail button placement and questioned many
people. There’s no real consensus so it doesn’t seem to matter. If it were
an issue we’d know about it. The most common answer I got was be button as
far aft as possible and the other somewhere in the other side of the CP.
The buttons are to keep the rocket going straight until the fins can take
over. So as long as you have that one button far aft you should be fine.
On Tue, Jun 2, 2020 at 9:27 PM Kyle Brookes <kyletbrookes@xxxxxxxxx> wrote:
Hi all, I have yet to be able to make it to a TCC launch, hopefully--
someday soon. but it you can't fly em, might as well keep building them.
So i wanted to see if anyone in the group had a rule of thumb for rail
button placement. I see that Apogee recommends placing them so that they
capture the CG. this make some sense as binding on the rail has less of a
lever arm. However Apogee doesn't appear to adhere to this rule in their
own designs. Both the Zephyer and Katana have the forward button ~70% of
the way between the CG and the rear button with large motors installed.
both systems also have the CG at 30% of length from the aft, however keep
the button spacing at 12 inches.
As far as math goes, i figure one way to look at it is allowable angle
deviation from the rail. so essentially the slop between the button and the
rail over the span button to button. this would lead to a constant spacing
independent of length (with some reasonable amount). My scratch build is a
near min diameter fiberglass so i have flexibility and constraints on the
placement that would differ from thru fin motor mounts as well.
Would love to hear thoughts form the list?
Thanks
Kyle
