Spin Fin Design

[sandman]

This is something I came up with about 40 years ago. (Yes, I am THAT old).

I had read something back them that said that a rotor or propeller got most of its thrust from the tips of the blades.

I incorporated that idea into a rocket design and found that the spin effect was tremendous...bordering on rifleing.

Best of all and not realized until launch, the spin effect was even more advantagious on recovery.

No streamer or chute is used. I expected a tumble recovery but instead I got a helicopter recovery.

The original design was a BT-20 body but my new on is large enought (BT-50) for a more positive motor retention. The fins were soaked in soapy water and the tips taped tightly around a spray can for a the curve. (they are drying now)

Check it out. No pics yet but CT showed me how to make a CAD drawing into a JPEG (but I think we broke the chat room doing it!)

All comments welcome...

sandman

sandman

 

[MarkABrown]

That sounds like a really neat concept. I can't wait to hear how it turns out. I'll bet Eugene will just eat this thread up!

 

[sandman]

I kinda thought Eugene would have responded first...LOL.

Perhaps this would be a better method of recovery for his upscale gyroc...have the heavy nose cone deploy, instead of the rear pod, and hang under the spinning rocket body.

sandman

 

[sandman]

OK, here are some pics of the reincarnation of the spin rocket design.

my wife has named it the "SPRIAL STUGATS"

sandman

 

[sandman]

Here is another view.

sandman

 

[sandman]

And one last view.

I followed the tube spiral with the silver stripe which is monocote trim. The silver square on the fin will hopefully flash in the sunlight as it spins.

The slight twist on the fin tips is all that is needed for a very fast spin on liftoff.

The nose is heavy and is suspended by a harness on recovery. The decent should be slowed by the spinning main body...I hope.

This will launch tomorrow. I'll rerport back.

sandman

 

[KermieD]

Please hurry back with those launch reports. I believe you when you say the tips will induce plenty of spin. I'm really curious as to how that comes off the rod. Since the spin is produced around the centerline of the rocket, I'm wondering if the torque on the rod would cause rod whip and/or hanging issues. Also, I'm curious as to how the spin affects recovery. I think I read somewhere about how the tips induce the spin, but it's the midpoint between the body and the tips that produces the lift.

Having absolutely zero actual experience with any kind of spinning recovery, I can't wait to hear how this goes. It's really neat when this kind of thing works, as I'm sure the crowd does a lot of ooohing and aaahing when something works well that looks different from the norm.

 

[Austin]

Sandman,

As usual, your building is nothing less than astounding bro!!! That has to be one of the coolest "made to spin" rockets I have seen...PLEASE give us a report on it's launch.

Oh yea, pics too!

Carl

 

[sandman]

OK here is the launch report.

I have to admit I'm a victim of my own technology. The initial concept involvled entirey too many design "improvements".

After four flights and lots and lots of "helpful" advice from all the other club members we figured out what went wrong.

1.) Don't use a double kevlar harness attached to opposite sides of the body tube.

2.) Don't use a steel leader with ball bearing swivel. (not enough wt. for the ball brg swivel to work properly.

3.) Stick with the original 40 year old design.

All that new high tech "crap" ...kevlar...ball brearing snap... stainless steel leader...would work for a good part of recovery but would ultimately get snagged and wound up around the rocket and made the dumb thing go "stable" for the last 100' of recovery resulting in more damage.

Yep, you guessed it. on the fourth and final launch of the day it worked perfectly.

The fourth final launch of the "Spiral' was PERFECT.

Just a nose cone and a shock cord...just like i designed it 40 years ago.

This was a prototype (total investment about $1.00). It will be rebuilt.

The final results...KEEP IT SIMPLE STUPID!!! KISS!


sandman

 

[sandman]

Well, the fins for the new Spiral are curved and taped over the form (a spray paint can)and should be ready for sanding tonight.

The new fins are 3/32" balsa instead of 1/16" for a little more strength.

A simple recovery system of just a shock cord and a nose cone. Just like the original. No streamer or chute.

As soon as this one is finished I will take it to the local school field and give it a try. I will report back immediately!

No pics yet...it will look exactly like the last one anyway!

sandman