Tailcone contributes to part of the total 1.0 meter length, but not the .85 length of 40mm diameter airframe. You must have .85 meters of 40mm diameter.

I tried to think through the question of tailcones. You can add a tailcone to reduce base drag, but you will be adding to the length of your rocket to do so. I suspect that it will still be a net reduction in drag, and some contestants will choose to go with a 29mm motor to do just what you are thinking.

Good luck!

Chad, I forgot to pick the rules sheets for this years contest at the meeting, are they online some place yet?

Ron

Contest rules have been posted on the Front Page, in the right hand Articles block. And we're working with Darrell Mobley to get the Upscale Contest announced nationally. Thanks for asking.

Thanks, I found them.

Ron

Hi,

Was in the process of planning my fin design, so I though I'd double check just to be sure. The rules stat 5.51" min. fin span.
Is this a crossed or the circumference around the fins? If it's circumference man those are some little fins. 😳

Howdy,

Cowabunga, those would be HUGH! That's a circumference of 19" or 12 1/2" across. Man, if that's the case I'll need to make them .010" thick, so much for a mile high, hehe.

That's the DIAMETER of a circle circumscribed around the fins, also known as the Span-Diameter in RockSim. The semi-span minimum is 2.755".

Thanks guys for your patience, so... just to be clear. The minimum Height of each fin, must be 2.755" from the body tube to the wing tip?

Thanks again

Not if what Chad said was correct. I would interpret his statement as saying that each fin must measure at least 2.75 inches from the center of the body tube, not the surface.

hey guys,

Found this on RP, thank you Goggle.

1. Root Chord
2. Sweep Angle
3. Sweep Length
4. Tip Chord
5. Body Tube Diameter
6. Semi Span
LE Leading edge
TE Trailing Edge

So, thank again for the help.

Chris is right. The RP diagram is wrong.

This is why I made a diagram that was handed out at the annual meeting. Here it is again.

https://files.me.com/chadair/01hl42

Hi,

Since my confussion I've done lots of reading, heres a qutoe from a NASA site and the link:

"For a trapezoidal wing, we need to know the semi-span (s), which is the distance from the root to the wing tip."

http://www.grc.nasa.gov/WWW/k-12/VirtualAero/BottleRocket/airplane/area.html.

So..each fin has to have a min. root to fin tip length of 2.755" or 1.97" which one? 😕

A circle circumscribed around the fins shall have a diameter no smaller than 5.51" (14cm). See the diagram.

Forget semi-span. It was not used in the contest rules.

Carry on- Chad

hehe, pretty hard to forget now. I understand what your saying, but would still like to know which is the correct use of the term.
So, then according to drawing our fins can have a min. height of 1.97"?