Question 1: Launch rod length
Kevin Beeson
www.rocketryonline.com and have found a ton of great information. I was
wondering if anyone could tell me where I can find similar information (web
sites, etc.) regarding the following:
Are there any guidelines or rules of thumb concerning the length of launch
rods? Is it better to get by with as short as possible or are long rods
preferable to guide the rocket?
Thanks in advance.
Michael Roy Hollihan
>
>
> Are there any guidelines or rules of thumb concerning the length of launch
> rods? Is it better to get by with as short as possible or are long rods
> preferable to guide the rocket?
>
> Thanks in advance.
Generally, for model rockets the standard length of a launch rod is 3-4
feet; for higher power (up the G/H) it's five feet. In general, the
longer the better, as this guides the rocket more as it gets up to
speed. However, given how wobbly most rods are, you get problems with
bending and 'whip.' When the rod whips, it can impart to the rocket
some angle you didn't intend. So, you don't want 'as short as you can
get away with' as this sounds like you want one that is too short and
for heavier rockets you don't want too long as they will bend the rod a
lot.
--
Michael Roy Hollihan
Mid-South Rocket Society
NAR Section #550
Memphis, Tennessee, USA
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"Of all tyrannies, a tyranny exercised for the good of its victims may
be the most oppressive. It may be better to live under robber barons
than under omnipotent moral busybodies. The robber baron's cruelty
may sometimes sleep, his cupidity may at some point be satiated; but
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Dwight L. Brown
For small models using 1/8th inch rods 3ft is good. For larger rockets
using 1/4" rods I use 5 to 6 ft .
D.B. Brown NAR 69453 L2
Andrew Waddell
--
Andrew D. Waddell
PML Online Support Rep
TRA 2043 L2/NAR 52875 L2
Email: ADWa...@home.com
PML: www.publicmissiles.com
Dwight L. Brown <n5...@delrio.com> wrote in message
news:t%g43.2672$Px3....@newsfeed.slurp.net...
Buzz McDermott
> I have read the rmr FAQs as well as all of the INFOCENTRAL articles at
> www.rocketryonline.com and have found a ton of great information. I was
> wondering if anyone could tell me where I can find similar information (web
> sites, etc.) regarding the following:
>
> rods? Is it better to get by with as short as possible or are long rods
> preferable to guide the rocket?
Common lengths are:
1/8" 36"
1/4" 48"
1/2" 72-96"
3/4-1" 96-144"
Generally, longer rods do not hurt, but there is a point at which they don't help any
more, either. You can run flight simulations with Rogers ALT4, WinRASP, RocSim or other
available software. These programs will give you a very good idea of the rocket's velocity
as it leaves a launch rod of a specified length. In most cases, you would like to have at
least 20 feet per second velocity for vertical launches in dead calm conditions and at
least 30 fps for most other cases. This is for your typical 3FNC/4FNC type rockets.
Buzz McDermott
NAR 13559 L2
Andrew Waddell
was talking about 1/2, 5/8, and 3/4" diameters.
--
Andrew D. Waddell
PML Online Support Rep
TRA 2043 L2/NAR 52875 L2
Email: ADWa...@home.com
PML: www.publicmissiles.com
Dwight L. Brown <n5...@delrio.com> wrote in message
news:t%g43.2672$Px3....@newsfeed.slurp.net...
>
> For small models using 1/8th inch rods 3ft is good. For larger rockets
> using 1/4" rods I use 5 to 6 ft .
>
>
> D.B. Brown NAR 69453 L2
> >
> > Are there any guidelines or rules of thumb concerning the length of
launch
> > rods? Is it better to get by with as short as possible or are long rods
> > preferable to guide the rocket?
> >
> > Thanks in advance.
>
>
Alan Jones
<holli...@bellsouth.net> wrote:
>Kevin Beeson wrote:
>> Are there any guidelines or rules of thumb concerning the length of launch
>> rods? Is it better to get by with as short as possible or are long rods
>> preferable to guide the rocket?
>>
>> Thanks in advance.
>Generally, for model rockets the standard length of a launch rod is 3-4
>feet; for higher power (up the G/H) it's five feet. In general, the
>longer the better, as this guides the rocket more as it gets up to
>speed. However, given how wobbly most rods are, you get problems with
>bending and 'whip.' When the rod whips, it can impart to the rocket
>some angle you didn't intend. So, you don't want 'as short as you can
>get away with' as this sounds like you want one that is too short and
>for heavier rockets you don't want too long as they will bend the rod a
>lot.
>
>Michael Roy Hollihan
Interesting. Are there any technical reports on launch rod whip and
related laucher/rocket dynamics? I'm not aware of any. I've always
assumed the longest launcher that you can transport and use is always
best, with diameter depending on rocket mass and rod length (and to
some extent, launch angle and wind speed). Ed Labudde may be
presenting an R&D report at NARAM indicating an optimal rigid launcher
length in the presence of cross wind.
Alan Jones, al...@nospam.avalon.net