Vertical rocket in swing test

[BDB]

Has anyone ever done a swing test and had the rocket stand upright while swinging it? I've seen backwards and forwards, but never upright. While I want to think that means that it will fly straight up no matter what I do, I suspect this isn't a good thing...

(Sorry no pictures. My daughter and I were swinging rockets over our heads in the driveway in the dark.)

 

[neil_w]

I would think that qualifies as "failing the swing test".

Is it a weird rocket, or something pretty normal that can be simmed in OR or something, to get a sanity check?

 

[BDB]

I assume this is a fail too. It was just remarkable how it didn't flop around like other failures that I've seen. It just stood straight up.

This was Esther's reversible rocket, so simulations are out. I think I'll add some "nose" weight and give it a real test. (From a safe distance, of course.)

 

[GalantVR41062]

My daughter and I did some swing tests on small MD 18mm rockets with success, later OR show they have about 1 caliper of stability.

Then I tried 2 scratch builds, a Bt55 45" long and Bt60 50" long, 3FN. Both were nose straight down during the test. I have flown the Bt60 on a 29mm AT E motor to 1000', and my new OR file shows the rocket has a lot of stability, 3-5 calibers pending motor.

I am under the impression forward horizontal swing test is good, I wonder if I was not able to swing the larger models fast enough for the fins to straighten out the airframe, resulting in a nose down perpendicular to the air flow test.

How do I swing test my 1/4 scale Viking 7 sounding rocket, 8" dia 144" tall and 52lbs with a full L motor?
JK, I will have to trust the sim, heads up flight from the away cell.

~John

 

[Zeus-cat]

I gave up on the swing test years ago. I found it difficult to get the longer rockets to fly straight while swinging them. A longer string helps, but makes it harder to get the rocket going and stopping it can be difficult too.

 

[lakeroadster]

........ My daughter and I were swinging rockets over our heads in the driveway in the dark..........

So very awesome... Blessed

I assume this is a fail too. It was just remarkable how it didn't flop around like other failures that I've seen. It just stood straight up.

This was Esther's reversible rocket, so simulations are out. I think I'll add some "nose" weight and give it a real test. (From a safe distance, of course.)

WAIT!!!! Please don't add nose wait until you video the swing test to show it standing straight up. I really want to see that!

 

[BBowmaster]

I find the key to a successful swing test (assuming a stable rocket) is a long enough string. I’m afraid I’ve dragged a few through the grass to get them started. An assistant to toss it in the swing direction helps.

 

[lakeroadster]

I find the key to a successful swing test (assuming a stable rocket) is a long enough string. I’m afraid I’ve dragged a few through the grass to get them started. An assistant to toss it in the swing direction helps.

One would think there should be some ratio of string length to rocket length?

Longer rockets need longer strings... anybody have a rule of thumb on this?

4:1 ... or ... 6:1 ... or ... 8:1

I've been using a 5:1 ratio. but the rockets I'm testing are only about 18" long or less.

 

[Alan15578]

My daughter and I did some swing tests on small MD 18mm rockets with success, later OR show they have about 1 caliper of stability.

Then I tried 2 scratch builds, a Bt55 45" long and Bt60 50" long, 3FN. Both were nose straight down during the test. I have flown the Bt60 on a 29mm AT E motor to 1000', and my new OR file shows the rocket has a lot of stability, 3-5 calibers pending motor.

I am under the impression forward horizontal swing test is good, I wonder if I was not able to swing the larger models fast enough for the fins to straighten out the airframe, resulting in a nose down perpendicular to the air flow test.

How do I swing test my 1/4 scale Viking 7 sounding rocket, 8" dia 144" tall and 52lbs with a full L motor?
JK, I will have to trust the sim, heads up flight from the away cell.

~John

Ah, The rope test. Have you ever watched athletes do the heavy hammer throw?

 

[jqavins]

A flat plate wants to turn broadside into the wind. That's what makes things like street signs and Galloping Gertie oscillate (when combined with springy or pendulum-like supports). I suppose if the CP and CG are dead on top of one another the same thing might happen to a rocket. Try swing testing a wooden ruler.