Thank you Andrew!
This is another occasion when I wonder why a certain number like 20 mph was
chosen as the maximum wind.
From: Andrew Wimmer
Sent: Friday, June 19, 2015 3:20 PM
To: roc-chat@xxxxxxxxxxxxx
On Fri, Jun 19, 2015 at 10:17 AM, R Dierking <applerocketry@xxxxxxxxxxx> wrote:
There could be problems when there is a cross wind to the rocket being held on
the rail. Not because of the potential rotation around one of the buttons, but
because rail buttons resist moving when they are at an angle to the rail. This
we know from inserting the rocket onto the rail and feeling it grab if not
going on straight. You can really feel any rotational torque. So the rail
buttons are grabbing on the rail guides and could induce a ‘snap’ as the rocket
goes down the rail.
I can't find it right now, but I did the math on this once on a "standard" USLI
airframe -6" dia, 10' long, 50lb on a CTI 4 grain L. The effect, even in 20mph
wind is extremely negligible. It's more pronounced when you're loading it on
the pad since you have the entire weight of the rocket torquing the button and
providing force on the interface between the button and rail. When it's leaving
the pad under thrust, unless you are launching horizontally, most of that force
isn't there, and the force from the wind, as mentioned, is very very small.
-Andrew
