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Just call me LimeStone Cowboy!You certainly don't see a nose cone made out of sandpaper every day.
Just call me LimeStone Cowboy!You certainly don't see a nose cone made out of sandpaper every day.
Great!@BABAR Thanks so much for all your help with this. I'm pretty sure I can follow your directions and make this with my son. It's also stuff that he can do most of the tracing, cutting and glueing. Your method is one that will allow us to make a nosecone that looks exactly like this drawing. We'll probably use one of the balsa methods to do a version of a traditional arrow. I'll make sure to post pics of the process. I've got plenty of the other building materials for the rest.
Some expanding foam squirted into the paper cone would serve to safely reinforce it as well as give the cone's shoulder something to seat against. Just be conservative with the amount squirted in, the excess will expand out the cone's open end so there shouldn't be much pressure against the sides.Great!
A minus (and plus!) of paper nose cones is that they do not survive ballistic recoveries well. I say that is in a way a plus, because most nose plastic and balsa nose cones don’t do well with ballistic impacts with asphalt and concrete And maybe playa del California, although they may do okay wit grass or soft dirt. So the plus is that these are much easier and cheaper to replace.
But the other plus is safety. Although a ballistic recovery (aside from Mosquito,Quark, and other featherweight recoveries) is never excusable, stuff happens. Paper nose cones are like the new car “crumple” zones, so if they hit something the paper crumples and the force is basically spread out to the width of the body tube or nose cone base. Not that, aside from the above, ballistic recovery is EVER safe, but if it’s gonna happen, I’d much rather get hit with one of these than a typical ogive plastic BT-20 cone.
You can reinforce the internal structure of these with heavy duty cardstock or balsa or plastic key card triangles cut just a bit smaller than your template and glued on inside before folding (although I have never needed to, if after a few flights the tip gets a bit distorted, I just make another. Mine are reinforced AND attached to tube with Mylar tape. Strength AND shiny color.....win-win! So swapping out used for new is easy enough. )
If you make them long and skinny, you can stick a bit of clay in the nose—— the added LENGTH makes a minimal mass go a looooong way is affect on CG.
I haven’t tried filling them with polyurethane glue, I am afraid the expansion would likely distort the contours.
There is a shareware program called poly https://www.peda.com/poly/ that can show many different polyhedrons both in 3D and a flat view.
Yep. By using straight edges the computer program could be run overnight and they could quickly iterate the design towards a low radar cross-section. Their program was heavily optimised also, which made this possible. Computers back then didn't have the memory or processing capacity to do complex things quickly.On a somewhat related topic, I was watching a video about Skunkworks. Someone found an obscure Russian paper on aerodynamics and decided to try and create a stealth airplane from the 60's era formulas. The result was the F-117, but the reason why it has straight lines is because in the 70s, they didn't have the computer processing power like they have now to calculate curved edges such as the F-22 and F-35.
That smile made my day,errr.... rather night since I work nights! Thanks for letting me play a part in this.Here he is cutting out a prototype and the "finished" prototype. It fits perfectly on a BT-20. I will be posting a separate build thread to show the whole process. Thanks especially to @BABAR for the ideas. @kuririn, we'll be using a coupler to make the nosecone as you suggested.
The rest of you, we're planning to make another version that is shaped more like an actual native american arrowhead and with natural style fletching. We'll be using the balsa ideas suggested above. This thread has been amazing and I appreciate all your help and encouragement. My son must have told me half a dozen times how much he loves doing this with me. Can't buy that with money!View attachment 423462View attachment 423463
Yeah, they might start looking for corresponding cardboard animals. Ha, ha.A future archeologists might find it and be very confused.
Also, when you make the cuts, you can actually cut only one side of the triangles between the trapezoids to use as a glue tab on the inside (for the other side that you would normally cut, just SCORE it and it will fold nicely.You may look into Modge Podge as both a stiffener and a finish. Besides being safe and age appropriate, it works well on paper. My son has been using it lately in paper/card stock creations. It makes them stiff and shiny.
With the feather fins and the mod podge on the cone, a string test would be interesting.Also, when you make the cuts, you can actually cut only one side of the triangles between the trapezoids to use as a glue tab on the inside (for the other side that you would normally cut, just SCORE it and it will fold nicely.
My card stock noses have held up pretty nicely, although now my Helis and AirBrakers land nose up rather than nose down, so that helps.
If your rocket is LONG enough (and I am thinking anything ARROW like should naturally BE relatively long) you don’t need any nose weight. That means much less landing stress. Knock wood (or cardstock), I have yet to have an AERODYNAMIC failure of any of my nose pyramids, most of which have been four sided. The max motor I have used is an E.
So the if you use a long body tube (I am thinking at least 18”), just put a shoulder at the base filled with enough polyurethane glue to hold a screw eye, your nose cone should last a while (especially if you cover it with duct tape )
I should have made myself more clear, we're not using actual feathers. We're going to make them feather-like, out of balsa. They'll be swept back, much more than an actual arrow would be because we're trying to duplicate the arrow from the photo in post one. I'm assuming the swept back design will also add more stability to it. I hope.With the feather fins and the mod podge on the cone, a string test would be interesting.
I’m also curious which lug option(s) you choose.
Also, when you make the cuts, you can actually cut only one side of the triangles between the trapezoids to use as a glue tab on the inside (for the other side that you would normally cut, just SCORE it and it will fold nicely.
Sorry, I meant to say feather-like fins. They look like they have significant weight but should be offset vertically by the mod podge or whatever weight you put in the card stock cone.I should have made myself more clear, we're not using actual feathers. We're going to make them feather-like, out of balsa. They'll be swept back, much more than an actual arrow would be because we're trying to duplicate the arrow from the photo in post one. I'm assuming the swept back design will also add more stability to it. I hope.
I'll be using a stand off for the lug.
Sorry, I meant to say feather-like fins. They look like they have significant weight but should be offset vertically by the mod podge or whatever weight you put in the card stock cone.
You could do both stand-off and lug attached to the fin.
Everything I have read and from my experience good white glue (real Elmer’s or Aleene’s tacky glue, NOT Elmer’s School Glue) is the glue of choice for paper to paper and paper to cardboard. I use it also for LPR motor mounts, has just as much strength as wood glue for paper to paper or cardboard and a longer “set” time, so it doesn’t “grab” too soon, with mount only partly inserted.Thanks for that great idea. I'm new to folding cardstock. Is there a particular glue that is preferred for glueing the tabs? I've got all the "traditional" glues, i.e. white glue, ca, etc.
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