A difficult design...

Ok, so a friend of my wife has asked to make a rocket that looks like a banjo for her father. Not a rocket with a picture of a banjo, the rocket needs to look like a banjo. Probably something mid-power size, large enough to see and be impressed, but small enough to be flown by someone that is not certified. I have been playing with a couple of ideas but I am not in love with them. Therefore, I am requesting input from you. Any ideas or suggestions?

I would try to make it look and fly like a rocket but have the ejection charge transform it into the shape of a Banjo, that way it can be admired longer. Good Luck.

Just my two cents,

David

At least up front, it does'nt lok toooo hard to do. Take it one step at a time. First-your gonna have to loose the goose neck at the end --straighten that out. Next-- the back end is gonna be heavy--not good! Let's look at putting it on a diet. Foam board might be a good bet and it's easy to work with.Your on your own finishing that one! The other idea I came up with---make it a tractor. Mount the --MOTORS-- up front -- and pull it into the air. Recovery might be an issue with that idea but the launch part should work OK. Ya know, if your good--I mean really ,really good---it could glide back----hmmm , now I'm thinkin about stuff--here we go again!!

We have a guy in our club that did a guitar. First time I saw him walking out to the pads I figured he was heading out to serenade his rocket...turned out, it was his rocket. He's flown it a few times. I can try to put you in contact with him.

Tony

hornet driver said:

At least up front, it does'nt lok toooo hard to do. Take it one step at a time. First-your gonna have to loose the goose neck at the end --straighten that out. Next-- the back end is gonna be heavy--not good! Let's look at putting it on a diet. Foam board might be a good bet and it's easy to work with.Your on your own finishing that one! The other idea I came up with---make it a tractor. Mount the --MOTORS-- up front -- and pull it into the air. Recovery might be an issue with that idea but the launch part should work OK. Ya know, if your good--I mean really ,really good---it could glide back----hmmm , now I'm thinkin about stuff--here we go again!!

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Funny you should put this in *these* terms!! I've done such things for nearly thirty years...and yes, they DO glide back, and the motor IS mounted up near the front end. Sort of Astron Invader-ish, but with a much longer forward tube attached up front, and this is ejected to allow the CG to shift aft for glide.

Matter of fact, I've even done an HPR glider of this very thing back in my old days. Flew on a J350, right after those motors were released back in 1996, and did well. Needed 5lbs of ballast in order to work, too! :y:

So, a banjo would absolutely work, if you had the forward tubing be like a BT80ish on like a 15-20" diameter disc.

AstronMike said:

Funny you should put this in *these* terms!! I've done such things for nearly thirty years...and yes, they DO glide back, and the motor IS mounted up near the front end. Sort of Astron Invader-ish, but with a much longer forward tube attached up front, and this is ejected to allow the CG to shift aft for glide.

Matter of fact, I've even done an HPR glider of this very thing back in my old days. Flew on a J350, right after those motors were released back in 1996, and did well. Needed 5lbs of ballast in order to work, too! :y:

So, a banjo would absolutely work, if you had the forward tubing be like a BT80ish on like a 15-20" diameter disc.

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I've seen the picture of your "circular" boost gliders. Banjos was the first thing that came into my mind.

not sure how much it will help but FLiskits has the rockstar which is electric guitar inspired, https://www.fliskits.com/products/01prod_fs.htm

mjennings said:

not sure how much it will help but FLiskits has the rockstar which is electric guitar inspired, https://www.fliskits.com/products/01prod_fs.htm

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If anyone can do it, Jim Flis can.

He's made a huge upscale Acoustic Guitar Boat for the 2000 Merrimack Library Cardboard Boat Race.........

https://jflis.com/leisure/canoeing/boat_2000/dreadnot.htm (Note: Photos in article are copyrighted by Jim Flis.)

Bob

This seems doable. The best flying would be basically a rocket with a round disk instead of fins. That disk is considerable aerodynamically if thicker than the tube/NC and the CG would only need to be slightly forward of the disk. Changing the tube to a neck on one side of the disk presents symmetry and recovery issues, but solvable. The CG would still need to be aligned to the center of the disk and the "neck" couldn't a have a tip/cone shape that pushes air to one side. Maybe just a central tube and attach a fretboard of wood or foamcore to one side. Nosecone behind the headstock. Put a nose weight on the side of the tube opposite the fretboard to shift weight forward and away from the extra weight of the fretboard.

Avoid going any larger than a real banjo.

Fins could be two round disks on either side of the central tube. You would likely still need to have some kind of fin in the plane 90 degrees from the disks but you could do that with acrylic so they were less noticeable. As noted previously, the nose"cone" could be shaped out of foamboard to look like top of the banjo. If you want to go all the way, why use round tube? Fabricate a square "tube" out of a cardboard box, or get some square tubes from a newwayspacemodels rocket kit.

You don't have to necessarily try too hard to make it look like a banjo, but can use elements of the banjo in the design and finishing. For example, for our wedding, I made a rocket with the fins looking like champagne bottles.

In the case of a banjo, how about a design like the neck for the body and half-round fins with a design resembling the body? If you make three fins, the body design can even continue across the body tube giving you "three banjos around."

This'll be pretty easy...

Neck out rectangular box... length as desired...

~ 8-12" round disk for body of banjo (and serves as fins in the x plane)

Make 4 long "fins" that extend up the body and up the neck and mimic strings (these will serve as strings and the y-plane fins). for stability,... would be easiest to do this front and back,... so banjo had 2 faces...

FWIW... this could be REALLY cool!

Somewhere I saw a fabulous photo of a highly realistic, near full scale electric guitar flying in Russia. I thought it might have been posted by Round over in the Year of Astronautics thread but I looked thru that and couldn't find it (nor with a search). Maybe in something linked from there? I'm sure it was from Russia and (alas) I'm pretty sure that it was reported to have crashed.

Peartree said:

Fins could be two round disks on either side of the central tube. You would likely still need to have some kind of fin in the plane 90 degrees from the disks but you could do that with acrylic so they were less noticeable. As noted previously, the nose"cone" could be shaped out of foamboard to look like top of the banjo. If you want to go all the way, why use round tube? Fabricate a square "tube" out of a cardboard box, or get some square tubes from a newwayspacemodels rocket kit.

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Wouldn't necessarily need fins. That's why I said the disk should be thicker than the "neck". Looking at the edge-on shape, even by cardboard cutout method of determining stability the CP wouldn't be that far forward. Add the effect of drag stabilization and it's very stable, even in the less good direction. However one problem of making the proportions completely realistic is that the CG would need to be in mid-air, behind the "neck" a little above the body.

A half-tube would be a good simulation of the neck, but wouldn't hold pressure very well, hence a tube in it or behind it. The whole neck could be the nose cone, but it would look better coming down if it wasn't and probably work better. Rear ejection could be used, but a styrofoam body would be better to land on.

If the banjo body did not have to be solid and two disks would suffice as the X axis fins, then there could be Y axis fins sandwiched between the two disks (you could sandwich two shorted open rectangular tubes as fins and to provide even more stability for the disks if they were to be large and too flexible/flimsy.

Wow, lots of great ideas, Thanks. I have already picked a few that I will incorporate into my design. If I actually build this rocket. I will upload some photos.

BTW, It will NOT be a glider. I have trouble getting Edmonds stuff to glide...
:eyeroll:

I'd say shape it out of foam and run some 29mm tube up the middle of it all. Headstock shaped from foam around a basic 29mm nosecone, and some lexan fins to keep it looking real. Throw a "minimum diameter" G motor in there and let it go :wink:


Braden