2nd stage ignition distance?

I am basically trying to 2-stage by stacking 2 Estes Alpha's. The 1st stage is going to be powered by a D12-5, and the 2nd stage is going to be powered by a C6-4...

I may switch that initial stage to a D12-3 or D12-0 depending on the feedback I get here...

Right now, the distance between the top of the 1st stage motor and the bottom of the 2nd stage is 14cm (5.5").

Any ideas?

TIA,

Randy. Melbourne, Ontario.

Well, a D12-0 is the obvious choice of three you mentioned. "Blow-thru" ignition can be awkward with the difference in motor diameter. Without some additional means of ignition transfer, I would not make the gap between motors more than the diameter of the lower motor. I think a C6-7 would be better in the upper stage as well.

Matt Melbourne, Victoria

I'll give you the short answers first, then follow it below with the long one.

I'm assuming you're chad staging here. I've clustered 5 to 5, C6-0's to B4-2's, 10.5" apart and chad staged all 5, 3 times now.

CHAD staging 1 to 1 should not be a problem for you, if you know and use a few building and flying tips.

First off, you don't want a 5 second delay on your first stage, you want to use a booster, no delay. A delay, especially that long, would allow the rocket to arc way too much before ignition of the 2nd stage. Then if it did light, you'd power it into the ground.

There would be several engine configurations you can use doing what you want to with an Alpha but let's start simple. I've learned that it's best to use engines of the same diameter when chad staging over maximum distances. If you just want to use a D engine, I'd suggest a D to D set up, but for your first attempt and using an Alpha at that, I'd start with a B6-0 to an A8-3. Why? Because the nozzles are bigger on an A than a C and larger upper stage nozzles, makes chad staging more reliable. Here's a few engine combinations you can use:

B series: B6-0 to A8-3, or A8-5 then try going to a B6-0 to B4-4 or B6-4. C series: C6-0 to C6-5 or C6-7 D series: D12-0 to D12 5 or D12-7

As you gain expeience building and flying this one, you can always increase engine size and try different configurations. Why not build 2 of them? I'd suggest 1 for 18mm options and another for 24mm options.

There are several staging tips you need to use when staging engines that far apart.

1. Test stability, as you may some weight in the nc to keep CG & CP correct.
2. You need to drill 3, 1/4" holes through the body tube, just below the coupler to vent the bt.
3. Place 2 pieces 1" x 1/2" of Scotch tape on opposite sides of the bt where the stages join.
4. Use a 3/16th lug and rod. While you're at it, use a 4' rod too.

There will be other tips in the articles listed below.

1 to 1 should be no problem, if you use the right methods of construction and flying. ***** Here's the LONG answer and some photos to help you along. Follow these links and I think you'll be able to do what you want to do.

Start here:

You should be able to scan through this in about 10 minutes. It's not that much, print it out or cut and paste it to your hard drive, to use as a reference as you build.

Then go to:

for the follow up. There are several pages there on clustering and staging scattered throughout the site.

What you want to know is available on these sites. Take some photos as you go of your build and flights. Most people on rmr would like to see them.

Good luck!

Randy

Here is some more usefull info!

In the Handbook of Model Rocketry I think G. Harry Stine presented data that as long as one uses venting holes between the booster and sustainer one could get away with several inches of distance. The number 7" comes to mind but I am uncertain. I remember being struck with that's a long ways between motors but he said it works. Put vent holes in my Quest Zenith II and the pop and go staging works fine. Kurt Savegnago

It's 12" in the Handbook (6th Ed., p. 172-173). If you take that as gospel, there it is. If not, then make up your own number .

Paul

Pete Bricker at NARAM 46 had a Giant Scale Saturn V staging perfectly with a 22" gap between first and second stage. He had a vented stuffer tube and parallel cannon-like tubes for the recovery system.He had done that consistently for apparently 5-6 times. Mister No

And PB had no stabilizing fins for the 2nd and 3rd stage. It was an awesome flight!