First scratch built two stage, Stage Fright

[o1d_dude]

By the way, using a laser printer, you don't have to clear coat the decals before you soak them in water.

I did not know that: 1. You had a laser printer, and 2. Laser printed decals don't require a clear coat fixative before soaking.

 

[qquake2k]

I did not know that: 1. You had a laser printer, and 2. Laser printed decals don't require a clear coat fixative before soaking.

I use the laser printer at work. The toner gets fused to the paper by heat, so it doesn't run in water.

 

[qquake2k]

I clear coated the water slide decals, and applied the vinyl decal.

 

[qquake2k]

I'm very happy with how this one turned out. Like all of my rockets, up close you can see the many imperfections. But stand back a few feet and it looks awesome! I expected the vinyl decal to look good, but I'm surprised at how well the water slide decals turned out. And the clear coat made them look even better, darkening them somewhat and bringing out the color. It looks exactly like I envisioned!

 

[qquake2k]

I still need to drill the vent hole(s) in the booster coupler. What do you guys think? 3/16" or 1/4"? One hole or two?

 

[o1d_dude]

That's funny.

I was looking at the pictures in the post above trying to spot the staging vent.

No clue on how many or how large. :confused2:

 

[qquake2k]

That's funny.

I was looking at the pictures in the post above trying to spot the staging vent.

No clue on how many or how large. :confused2:

You wouldn't be able to see it, it would be in the coupler. But I haven't drilled it yet in any case.

 

[qquake2k]

I still need to drill the vent hole(s) in the booster coupler. What do you guys think? 3/16" or 1/4"? One hole or two?

Bump...

 

[GDJ]

Bump...

Hard to say how big or how many. Is the vent for the excess ejection charge or does it vent off some of the 2nd stage thrust to prevent damage to the booster housing?

 

[[POW]Eagle159]

From my 2 gap staged rockets(9'' and 3'' gap) The hole goes right under or as close as possible to the second stage. On mine Ive done 4 3/16 holes....But that tends to be a lot and they have worked for 3 flights each.

Below is good info. on it. around pg. 5

https://docs.google.com/viewer?a=v&...s4sL3E&sig=AHIEtbTpC4TVviPJlP5yMaZmGA1ZUF5bEg


Why didn't you do this when you were still building?

 

[[POW]Eagle159]

Hard to say how big or how many. Is the vent for the excess ejection charge or does it vent off some of the 2nd stage thrust to prevent damage to the booster housing?

Its so when the booster ejection goes off there isn't a build up of pressure on the tube and the booster ejects off before the top stage is light.Also it is so the booster ejection pushes the colder gasses in the tube out so the hot gases light the second stage...

 

[GDJ]

Its so when the booster ejection goes off there isn't a build up of pressure on the tube and the booster ejects off before the top stage is light.Also it is so the booster ejection pushes the colder gasses in the tube out so the hot gases light the second stage...

I see. Cool!

Since the ejection charge is under some pressure, and since the composition of the exhaust gasses are known, the trick is to vent just enough so there is just enough pressure build-up to keep the heat where you want it, but just enough to light and not create a pressure vessel, right?

 

[GDJ]

I did some quick math on some old tables for flow/velocity for Hydraulics, and changed the numbers for the average density of the exhaust gasses.

Single 1/4" (6mm) hole should be sufficient, two 3/16 holes is actually starting to get a bit on the large side due to the volume of two orfices letting out the gasses, but it should be okay. Same with a single 5/16. 3/8" is too big, and you probably wont have enough hot gasses left to ignite the 2nd stage.

BUT, this is just a quick table calculation, and my math might be out a bit. Others should chime in to confirm or refute what I said. Either way, information is good.

 

[[POW]Eagle159]

I see. Cool!

Since the ejection charge is under some pressure, and since the composition of the exhaust gasses are known, the trick is to vent just enough so there is just enough pressure build-up to keep the heat where you want it, but just enough to light and not create a pressure vessel, right?

More or less, yes. When the ejection goes off, the hot gases and is shot up with the cold gases being pushed out and the hot gases/burning BP chunks keep going up until they hit the top engine.And....Woosh!

I think the vent hole(s) can be quite small, but to me better safe than sorry.

 

[GDJ]

True. Better to be safe than sorry. Do you want to have the ejection charge to simply ignite the 2nd stage, or will the pressure build-up assist in stage seperation, or will the 2nd stage just push the booster out?

 

[[POW]Eagle159]

True. Better to be safe than sorry. Do you want to have the ejection charge to simply ignite the 2nd stage, or will the pressure build-up assist in stage seperation, or will the 2nd stage just push the booster out?

From what I've seen on my rockets, The 2nd stage causes Soooo muck pressure, the booster flys off


I'm making a rocket with 2 chutes for the booster for my next scratch build!

 

[GDJ]

From what I've seen on my rockets, The 2nd stage causes Soooo muck pressure, the booster flys off


I'm making a rocket with 2 chutes for the booster for my next scratch build!

I would go with a single 1/4" hole then. That should be enough.

I admit I never played with vent holes. I just used the Estes black powder engines and they were butted up against each other with a 4mm spacer between them and I doubled up the tube over the joint area. Never had to worry yet on venting.

 

[[POW]Eagle159]

I would go with a single 1/4" hole then. That should be enough.

I admit I never played with vent holes. I just used the Estes black powder engines and they were butted up against each other with a 4mm spacer between them and I doubled up the tube over the joint area. Never had to worry yet on venting.

Yes one or two 1/4 vents on opposite sides of each other is probability the best.

 

[qquake2k]

This is the way I understand it. The booster doesn't have an ejection charge, just propellant. BP motors burn from the bottom up. As it burns towards the top, at some point the propellant that's left won't be thick enough to contain the pressure any longer, and it bursts upward. This shoots hot gas and (more importantly) burning chunks of BP propellant towards the sustainer motor. The burning chunks are what ignite the upper stage motor. The vent hole is to prevent the booster from pushing away before the upper stage motor ignites. Once that happens, it will push the booster off and away.

 

[gdjsky01]

Venting is to give the existing air inside some place to go when the hot gases push forward

 

[qquake2k]

Well, it looks like our first club launch of the season will be tomorrow. Woot! Like I've done before for clusters, I soldered lead wires onto the igniters so I can attach them all together. The first flight will be 2xC6-0/1xD12-0 in the booster, and a D12-7 in the sustainer. Succeed or fail, it should be an exciting flight!

 

[GDJ]

I have faith that this will work just fine.

 

[qquake2k]

I have faith that this will work just fine.

Thank you for the vote of confidence!

 

[gdjsky01]

Absolutely happy (???) that you can finally get all those scratchers off the pad. Win or lose have loads of fun out there!

 

[qquake2k]

Absolutely happy (???) that you can finally get all those scratchers off the pad. Win or lose have loads of fun out there!

Oh, I plan on having a good time and putting on a good show!

 

[qquake2k]

I drilled a 1/4" vent hole in the booster coupler. I flooded it with CA so I could clean it up and sand the outside smooth. Stage Fright is ready for Act 1!

 

[o1d_dude]

Isn't there an old rocketry saying that goes "If all goes well, it will be exciting. If not, it will be really exciting"?

I'm looking forward to this one. It will be "exciting".

 

[Scotty Dog]

I'm very happy with how this one turned out. Like all of my rockets, up close you can see the many imperfections. But stand back a few feet and it looks awesome! I expected the vinyl decal to look good, but I'm surprised at how well the water slide decals turned out. And the clear coat made them look even better, darkening them somewhat and bringing out the color. It looks exactly like I envisioned!

I kinda lost track of this build.I just got looking back at it.WOW!!! Love the way it came out. Dont ya love it when It looks exactly like I envisioned![/!!!

 

[gdjsky01]

Should be hearing something soon... its too dark to still be launching...

 

[qquake2k]

Should be hearing something soon... its too dark to still be launching...

Well, it was somewhat successful. It was a nice initial boost, the upper stage ignited without a problem, but then the sustainer land sharked. The sustainer was undamaged, but the booster apparently didn't tumble (I didn't see it fall). It looks like it hit butt first very hard, the body tube is crumpled in several places. And it did something to the coupler, it's now very tight. I can fly the sustainer as a single stage on 24mm reloads, but I haven't decided what to do about the booster yet. I think it needs more oomph, and I thought about building a new booster with a 3x24mm cluster. But I don't know if that would give the upper stage enough momentum. It looked like the sustainer was underpowered.

I have photos and a video, but I'm still editing everything. I should have something posted tomorrow.