MaxQ
Tripoli 2747
I am looking at a particular design problem....many of you have probably done a project that has fins that have substantial extension below the aft end and have had to deal with recovery issues.
On lightweight rockets, may not be too much of a problem. My original Loc IV came without thru the wall fins (which the kit now has) so I had do do a lot of repairs over the years.
Once the project gets bigger, and the weight goes up, the ability of the fin to absorb the hit on landing w/o breaking off becomes a problem.
Probably why a lot of the bigger projects don't have fins that extend below the airframe.
But if you want to do a scale project..this becomes an issue (see the second picture below...Mercury Little Joe).
I've done thru the wall fins on most projects, with reinforcing internally at the the fin root to motor mount.
The fins on my Astrobee 1500 survived one recovery falling w/o the main parachute attached (ground was soft and the fin roots were heavily reinforced internally - see the first picture below)
I've heard some guys do bolt on fins for easy replacement when they are damaged, but hiding the non scale bolts would be a problem on some scale projects.
Some guys probably opt for a solid thick fin, as a hollow structure is prone to damage.
I've seen a lot of L-3 projects where the fins are locked into centering rings above and below the fin root, with threaded rod between the centering rings.
Any other ideas?
On lightweight rockets, may not be too much of a problem. My original Loc IV came without thru the wall fins (which the kit now has) so I had do do a lot of repairs over the years.
Once the project gets bigger, and the weight goes up, the ability of the fin to absorb the hit on landing w/o breaking off becomes a problem.
Probably why a lot of the bigger projects don't have fins that extend below the airframe.
But if you want to do a scale project..this becomes an issue (see the second picture below...Mercury Little Joe).
I've done thru the wall fins on most projects, with reinforcing internally at the the fin root to motor mount.
The fins on my Astrobee 1500 survived one recovery falling w/o the main parachute attached (ground was soft and the fin roots were heavily reinforced internally - see the first picture below)
I've heard some guys do bolt on fins for easy replacement when they are damaged, but hiding the non scale bolts would be a problem on some scale projects.
Some guys probably opt for a solid thick fin, as a hollow structure is prone to damage.
I've seen a lot of L-3 projects where the fins are locked into centering rings above and below the fin root, with threaded rod between the centering rings.
Any other ideas?
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