Re: Re: F1D partial motor blast shield

From: Jake Palmer <82.jake_at_gmail.com>
Date: Thu, 19 Jul 2012 17:13:10 -0700

I can't comment on the effect of the CG change until I try it. I know
Larry was actually ballasting his model up to weight so it was easier for
him to move both the weight and CG as necessary.

Regarding protection, he said he remembered at least one partial motor
breaking. It damaged the blast tube, but left the motor tube unscathed.

On Thu, Jul 19, 2012 at 4:08 PM, William Gowen <wdgowen_at_gmail.com> wrote:

> **
>
>
> Just wrap the motor tube with graphene.
>
> On 7/19/2012 7:04 PM, Yuan Kang Lee wrote:
>
>
>
> Assuming that you place the extra balsa where the partial motor is, it
> will be impossible to replicate the same CG as the full motor. It would be
> 50 mg of weight placed well in front of the CG. Perhaps the effect is small.
>
> The other question I have is how much protection does the extra balsa
> provide. If the protection is adequate, does this mean that extra balsa
> over the full length of the motor stick (100 mg of balsa) could protect the
> whole motor stick? It would be nice if this is the case, but it would be
> difficult to find a spare 100 mg. If you could spare 50 mg and protect part
> of the stick from an exploding full motor, where would you place the
> protection?
>
> --- In Indoor_Construction_at_yahoogroups.com, Jake Palmer <82.jake_at_...><82.jake@...>wrote:
> >
> > I had the fortune to spend some time talking to Larry Coslick at the
> Kibbie
> > Dome this year. I lost 2 motor tubes to motors that broke during or after
> > loading them onto the model (one broke just seconds after launch). He
> > mentioned something he's done in the past and I think it's a brilliant
> idea.
> >
> > While he was doing partial motor testing he covered the first 4-5" of his
> > motor tube with a leftover piece of another motor tube. He cut open the
> > seam wide enough so it could slip over his motor tube, but narrow enough
> so
> > it stayed in place. The idea is that it's a semi-permanent blast shield
> > that stays on the plane during quarter and half motor testing. Even if
> the
> > motor breaks after launch it will protect the motor tube. It's about a
> > 40-50mg weight penalty, although you can use a lighter partial motor
> stick
> > to offset the weight (just make sure you get your CG right). When he
> > switched to a full motor he removed the sleeve. I plan to use this idea
> > for all my future partial motor tests and I thought I'd share it with
> > anyone else that might find it useful.
> >
>
>
>
>
Received on Thu Jul 19 2012 - 17:13:11 CEST