I hope I will be forgiven for not getting these in the correct order.
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, just for maximum noise and excitement at the flight line.
Sounds like a real answer, and hard to argue with. However, I have found that, at rocket launches, nothing beats the excitement of a rocket losing it's fins at about 100 feet of altitude and whirling around, with everyone trying to guess which direction it would be pointing if it straightened out. Not really my kind of excitement, though. A low flight by a 5 foot, medium or high powered rocket with no deployment, plunging straight into the ground nearby at a good clip was pretty exciting, too.
Please post links to where I can buy this edge stock for a BT-60 or BT-80 rocket's fin leading and trailing edge. It would rock for a scale look, as it is not going to Affect the price of the motor I need to use.
Edge stock I have used on RC planes is much too big for Mid-to smaller High power and lower rockets.
I admit I was thinking mostly of the bigger rockets, and in that case, Bob's your uncle. Just now, I was poking around on the net. I saw egregiously expensive, 3/16" rounded leading edge stock on eBay, and cheaper, thicker rounded stock elsewehre. I saw 1/8" t.e. stock that could be glued together to make symmetrically beveled 1/4 inch stock. With a simple balsa stripper, one could narrow the t.e. stock and glue together to get 3/16" or maybe thinner beveled stuff. Here are some sources for that sort of thing:
1/8 thick t.e.
https://www.nationalbalsa.com/products/181236te
https://specializedbalsa.com/products/lead_trail_aileron.php
https://balsausa.com/products/balsa-trailing-edges?variant=43671246700834
However, in my next post I intend to show a method to bevel fins consistently and quickly.
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A couple of things before we address the OP's fin topic.
1) Me and West 105/205 is like a three year old and maple syrup. Oy.
2) Me and West 105/205 with colloidal silica is like a 1st grader and library paste. Vey.
Unless you were wearing gloves, that's not very healthy. In the case of the coloidal silica, I strongly advise you to wear a really good dust mask as well. That stuff is nasty. It does nice things to the consistency of the epoxy, though. Other things I've used to thicken epoxy have been wood flour and something called plastic mini (or micro?) fibers. You can use phenolic or glass microballoons if you don't need ultimate strength. That will come out lighter and be easier to sand, but it's not as nice for the consistency. It works, though. Above based on a little boatbuilding experience. SIMPLE boatbuilding, I'm not one of those expert craftsmen who can make a Whitehall boat that sells for $15,000. But my boats floated and worked ok.
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Performance failure mode: Poor performance due to drag and to fin flutter
1) Fins should be tapered root to tip (reduces weight and drag and if I am not wrong eliminates a resonant frequency which limits flutter).
Yup. Keeps the stiffness where you need it, at the root, while reducing the weight out near the tip, where it matters most. I assume you mean tapered in thickness as well.
2) Fins should have an airfoil shape to minimize drag, appropriate for the rocket (rounded front and tapered back for subsonic, wedge for supersonic, if I am not wrong - if you have superior knowledge please correct me).
I'm absolutely sure you're right about subsonic stuff, and I've heard the same thing about supersonic. For subsonic, there is no harm in making the fins as much as 10 percent thick, if they're in a good airfoil shape. A good airfoil shape can be an ellipse, with the high point 20 or 25 percent of chord back from the leading edge, with tangent lines going back to a thin trailing edge. Other, more complicated shapes may be a little lower drag, but that one's not bad. The airfoil in the following picture, by the famous Mark Drela, is VERY close to this shape and looking at it is how I concluded that the ellipse and tangent lines were a good shape. This foil was meant for low Reynolds numbers, but it's still reasonably low drag, according to Drela's Xfoil program, at Reynolds numbers of 1 and 2 million. Assuming you don't make one extra swipe with the sandpaper. For extra stiffness and strength, doubling the thickness probably wouldn't hurt much at all at those relatively high Reynolds numbers. If memory serves, a good approximation for Reynolds number at sea level conditions and reasonably comfortable temperatures is the chord in inches times the length in the direction of flow (fin chord, in this case) times 532. So a 4 inch wide fin going 500 feet per second would have a Reynolds number of a bit over a million.
In the case of supersonic rockets, I wonder if anyone has explored using the Whitcomb area rule for small rockets that reach high Mach numbers at low altitudes, as many hobby rockets do. We might see something that looks like a V2, except with a bit of hollowing out of the body where the fins are. The F-102 was unable to break Mach 1 until the fuselage was narrowed like that where the wings were. You can see the difference here:
Certification Failure Mode: Certification failure for the fins is a fin breaking (in landing) or shearing off (in flight), another failure mode is losing the rocket
1) The more meat you have on the fin, the less likely will be a break upon landing
2) Fins shearing off is unlikely for any rocket for L1 or L2 if the fins are properly filleted.
3) Square (low aerodynamic performance) fins keep the rocket low and slow and increase the chance of finding the thing after the flight.
So if I had been thinking about L1, I would not have tapered an profiled the fins so excessively. I'm an engineer, so I think that it was my natural prediliction towards aero performance that had me do so much work. We'll see how much of an error I made.
If L1 had not required a motor of at least a minimum size, you could have used a smaller motor to control the altitude. Maybe you should carry water ballast that drains when the chute opens, rather than messing up the fins. Or just put an o-ring on the outside of the nose. THAT ought to slow it down.
Jeeps are not meant to go fast. The more squarer, the more betterer.
Tell that to the driver of the ones that pass me on the highway going 75 mph. I doubt if most of the ones I see ever go further off-road than someone's lawn. On the other hand, I drove a little sedan up here once to watch hawks migrating when my s.o. didn't feel like a hike:
https://maps.app.goo.gl/m9f1cub8MLLBPit78
I find that trees like the taste of really streamlined fins.
Hard to argue with that.
