RE: [AR] Re: Modeling liquid engine aft body in OpenRocket
Bob,
FYI… here is a design for a retractable launch lug. This is for a C-type
rail, but we have modified for the Baxter launcher at FAR which uses a
T-type rail. I have found (and you can sim to verify) that the launch
lugs/rail guides add a "not non-significant" amount of drag to the rocket.
<<...>> <<...>>
Kevin,
I have had "slow" accelerating liquids weathercock by 5-10° even in light
wind conditions off the Baxter rail at FAR. I feel there might be some sort
of "torqueing "effect as the aft rail guide leaves the rail. Can anyone
address this?
--- Carl Tedesco
-----Original Message-----
From: arocket-bounce@xxxxxxxxxxxxx <arocket-bounce@xxxxxxxxxxxxx> On Behalf
Of Robert Watzlavick
Sent: Wednesday, July 29, 2020 5:42 PM
To: arocket@xxxxxxxxxxxxx; Kevin Ho <rebelwithoutajob@xxxxxxxxxxx>
Subject: [AR] Re: Modeling liquid engine aft body in OpenRocket
I was going to follow the FAR guidelines for the Baxter launcher, placing
one at the CG and one at the aft end of the body. I've seen other
references that suggest one at the CG and one at the CP. The skin is very
thin (0.016 inches) so I'm going to have to add stiffeners underneath.
I'd really like to 3D print the rail guides out of nylon but I'm worried
the steel rail will cut through it so I'll make them out of aluminum.
-Bob
On 7/29/20 7:17 PM, Kevin Ho wrote:
IIRC you are using a long rail, which should reduce weathercocking to
a certain extent. Longer rails means higher off-rail speed, which
means that even in a wind gust your relative wind will shift by less
degrees off the nose.
Also a controversial topic, but where are your rail buttons going to
be? That can greatly affect off-rail weathercocking. Placing the aft
button close to the CP can reduce the swing somewhat.