Geof Landis, Phd. was a legendary member of the MIT Rocket Society. He championed the Geodesic Method for altitude data reduction, as well as many other accomplishments. His Landis Loop was a simple ring that centered the aft end of an egglofter or similar shaped rocket launched from a tower. I don't have picture handy.
Question on fineness ratio
- Thread starter SDramstad
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It's in the NAR rules for sure. Section 2.6:
"A rocket used for a Level 3 certification must have a minimum fineness (length-to-mean diameter/body width) ratio of 4:1 and be aerodynamically stabilized using fins, tubes or other non-shroud components of measurable thickness not to exceed 10% of the mean chord or semi-span. In lieu of calculating the mean diameter/body width, maximum diameter/body width may be used. The documentation submitted for review shall include the fineness ratio and mean chord/semispan-to-thickness ratio "
So, "must ... be aerodynamically stabilized using fins, tubes or other non-shroud components ..." rules out sticking a motor in a nose cone.
Thank you! I thought it was a NAR rule and not a Tripoli rule. I still am eager to fix any poorly written or confusing Tripoli rules.
That might have been my bad. I was looking at the NAR rules and the Tripoli President popped up and Tripoli got pulled into it. My bad.......
No problem. I’m like a bad penny.
Not if you put fins on the nosecone. Doesnt say it has to have a body tube.
Well, this is why we have TAPs and L3CCs, I guess. They have refusal rights over your design.
Fins on a 5:1 nosecone would be cool to see.
Even if they meet all of the very specific rules for an L3 attempt? Not that I would do that. My L3 design is a very basic 4FNC. But this looks like a loophole to me.....Well, this is why we have TAPs and L3CCs, I guess. They have refusal rights over your design.
The fineness of a rocket can show its susceptibility of an airframe to bend in a side wind. I wouldnt think most nosecones would affect that all that much so I could argue there should be a minimum L/D for the airframe excluding the nosecone.
I have a bunch of 5.5 inch plastic nosecones in the garage. One with fins and/or a ring fin will happen when I can get to it.. Probably rear ejection.
As a TAP and L3CC, we do have wide authority to refuse a candidate, but we would not refuse one without reason. Now, that reason could be that we believe a candidate is immature or has terrible judgment, but whatever the reason we need to explain it to the candidate. Designs that meet the requirements are unlikely to be refused.
Dang, I have to be mature?????
It’s a low bar. I made it over.
Okay, scared me a bit.......It’s a low bar. I made it over.
NateB
Well-Known Member
Too much time on my hands today. I think a ring fin would look better, but Open Rocket won't sim it. This was quick, but anyone could play around with nose weight, fin size and shape, and motor choice for better stability.
