No, mass is not mass. If I needed 4 oz of weight at the tip I would need a
pound at the middle (depending the length of the rocket, placement of CP an
CG etc. The point is the lever arm.) With lead I can get really close to
the tip. With feathers I'd need a lot more volume and the cg of the mass
would not be near the tip so I'd need perhaps a pound of feathers to be
equivalent to the 4 oz in moving the rocket's CG. The length of distance
between the center of Mass of the rocket without the weight and the center
of mass of the added weight determines how much weight you need to add. At
the tip "less is more".
But to your other point. Once I add the epoxy to keep the sand in place it
in fact becomes "trash" on the playa because of the epoxy. And if I've
used the epoxy and things come apart a 4 oz blob of sand/epoxy is going to
hurt just as much (probably) as a 4 oz blob of lead/epoxy.
Sorry, I don't see any benefit to changing materials currently. Although I
must admit your idea of using water for ballast on the way up and letting
it drain out on the way down to reduce weight at landing has always
fascinated me.
Thanks,
Mike
On Mon, Jan 30, 2017 at 2:19 PM, R Dierking <applerocketry@xxxxxxxxxxx>
wrote:
Sorry Mike. I believe you have not considered other things and went to
what you knew first.
Yes, mass is mass. I don’t think anyone needs a high density material for
nose weight. It’s just not that critical.
However, it would probably be impossible for me to convince anyone that
insists on metal material. But, what the heck, I’m trying anyway.
Richard
*From: *Michael Klett <xsive.guy@xxxxxxxxx>
*Sent: *Monday, January 30, 2017 2:15 PM
*To: *ROC Chat <roc-chat@xxxxxxxxxxxxx>
*Subject: *[roc-chat] Re: Prohibiting Metal for Nose Weight
Richard,
My ballast of choice is lead BBs. They seem safely captured in epoxy. I
would also argue that by using lead they occupy less volume so I can get
the center of the mass of the BBs further in to the tip of the nose cone
and so I need less weight. Less weight is safer. If I tried to put the
weight in the AvBay for instance, I'd need a lot more weight to balance the
rocket and the additional weight would reduce the safety some.
Thanks,
Michael
On Mon, Jan 30, 2017 at 2:05 PM, R Dierking <applerocketry@xxxxxxxxxxx>
wrote:
Then why do even people with model rockets use metal?
The RSO wouldn’t want someone with an aluminum nose cone on a HP rocket
but accepts rockets with a nose containing bolts or lean shot. And, having
taken a nose apart that had bb’s set in 5 minute epoxy, the epoxy cracks
and releases the bb’s.
*From: *Allen Farrington <allen.farrington@xxxxxx>
*Sent: *Monday, January 30, 2017 1:59 PM
*To: *roc-chat@xxxxxxxxxxxxx
*Subject: *[roc-chat] Re: Prohibiting Metal for Nose Weight
Tripoli has an official statement on using metal...you can find it on
their website here:
http://www.tripoli.org/Portals/1/Documents/Safety%20Code/
Metal%20in%20Rocket%20Construction%20v2.0.pdf
Allen
Sent from my iPad
On Jan 30, 2017, at 1:50 PM, R Dierking <applerocketry@xxxxxxxxxxx>
wrote:
Next time the NAR and TRA safety rules are revised, there should be
something about what kind of nose weight should be used or how about
shouldn’t be used.
Don’t the codes already say something about minimizing the use of metal?
Why add it? There’s no good reason why metal has to be used; there are
other things that would work fine.
And, just to get ahead of the one response that’s going to ask if a
rocket with other types of weight could hurt someone just as bad. Yes, I
realize that. But, again, if you think through the various failure
scenarios, metal (bolts, lead shot, bb’s, what ever…) is a poor choice for
nose weight.
What other things could be used? Things that would be even better for
both safety and performance.
Richard Dierking
--
*Justice shall flourish in his time, and fullness of peace for ever.*
*Psalm 72*
