The "Initiator" home made 2 stager

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TimothyAReed

Well-Known Member
I am going to try and scratch build my first 2-stager hence "Initiator" I already am HPR L1 JR certified and have some experience building rockets from scratch(if you don't try new things you won't learn). my ASP order should arrive tomorrow but I already have fins cut out and an open rocket file made. Anyone with experience flying a 2-stager please download the file and voice your concerns here are a couple things that need to be addressed:

1. still don't know the final dimensions of the nose cone(or weight can always add some) because it is part of that Estes plastic nose cone assortment that's part of the ASP order.
2. motor retention on the sustainer is still a question, I am thinking of using a hook and just cutting a slot in the booster motor mount tube to allow the sustainer motor w/ hook to slide in (might 3d print and ABS ring around that slot to keep up structural integrity.
3. should I use a kevlar cord attached to a centering ring for my shock cord or a 1/4" elastic shock cord mounted by the "teabag" method?

View attachment Initiator_rev2.ork

View attachment Initiator_rev3.ork

View attachment Initiator_rev5.ork

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Rex R

LV2
umm, any particular reason for leaving close to 2" of motor out in the breeze? you might want to look up 'Gap staging'.
Rex

TimothyAReed

Well-Known Member
umm, any particular reason for leaving close to 2" of motor out in the breeze? you might want to look up 'Gap staging'.
Rex
That was to bring the CG aft, also it was because I have a 5.75" 24 mm motor tube and It didn't fit in the booster so I had to put it somewhere..

Updated the .ORK file on the original post

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Incongruent

Well-Known Member
Do you have tube cutters to potentially cut the tube shorter? If not, you can use a strip of paper wrapped around the tube as a guide.

fyrwrxz

latest photo
I made one 18 (?!) years ago and lost the sustainer to the 'guard cows' in Monroe, Wash. Thank the rocket gods no electronics were lost!
A few tips:
Lose the hook and motor block and stainless steel wadding. Go with Estes 29mm retainer or Aeropack if you got it. If you go 38mm on the booster-sleeve it and play it conservative. Don't do a long burn on the top until you dial the stack in.
Re-inforce the booster section at the bottom by cutting some off the sustainer body tube (or use a coupler cut down) and use the rest on the bottom of the sustainer. Where is your timer or altimeter? I used an Adept in the bottom for booster chute and a small timer in the top for a sep charge if the motor deploy didn't work. Long hand math to figure coast time. Wire leader for flame resistance on booster with blanket and barf to protect chute. Altimeter in sustainer rigged with drogue and middling fire agl to give me time to acquire it (visual only). I reduced the top tube by approx 5-6" (I used it) and ran 1/4 alaly tube next to the motor tube for the charge/igniter wires. The interstage adapter was cumshawed out of two blue tube couplers resawn to nest where the re-inforced top of the body for the sustainer and into the rear of the already sleeved bottom of the booster.
Forget the 'tea bag' and rubber band stuff-strictly low power. Do the kevlar thing. Like an idiot the first (and only flight) of the sustainer by itself was an "H' and it drifted way too far as my recovery load calc was off. You wil need long wires for the drogue event-I used shooter's wire to the charges. GROUND TEST EVERYTHING. It took me a dozen to get the stack right and I used a soft charge (rubber glove finger) for the sep charge. I don't think anything was above 2 g of 4f. If you want Pm your addy and I'll send you some microfuge 1.5 tubes for testing-no charge.
FWIW- I cut the strakes off the standard aerotech fins on the sustainer and rebalanced the whole thing so it was stable. Oh yeah- bulkheads in the nose cones. Lotta build time in Washington because it rains every 15 mins or 29 days out of the month for 23 hours each day.
If anybody reads this from Washington (Monroe field) it was white with a red/white/metallic blue "PYRAT" outlined in red on the side. i expect it got plowed under. Sorry if this is confusing but PM me if you need clarification. It was a fun build during the long hours alone up there. I'll have to do another one. Have fun with yours! You should ask the serious stagers out there about the new electronics. Cris from Eggtimer has good stuff that's affordable and is working on a few new things I'll let him announce. You may be really interested in one of them. Straight smoke and good chutes!

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Rex R

LV2
why would the OP need all that fancy electronics for staging a pair of Estes bp motors?
Rex

Rex R

LV2
unless you have a desire to use a bp E motor in the sustainer...I would suggest using the longer tube in the booster and the shorter tube in the sustainer. stagers are typically 'over stable'(nature of the beast) I wouldn't worry too much about it at this point.
Rex

TimothyAReed

Well-Known Member
I made one 18 (?!) years ago and lost the sustainer to the 'guard cows' in Monroe, Wash. A few tips:
Lose the hook and motor block and stainless steel wadding. Go with Estes 29mm retainer or Aeropack if you got it.

Re-inforce the booster section at the bottom by cutting some off the sustainer body tube (or use a coupler cut down) and use the rest on the bottom of the sustainer. Where is your timer or altimeter? I used an Adept in the bottom for booster chute and a small timer in the top for a sep charge if the motor deploy didn't work. Long hand math to figure coast time. Wire leader for flame resistance on booster with blanket and barf to protect chute. Altimeter in sustainer rigged with drogue and middling fire agl to give me time to acquire it (visual only). I reduced the top tube by approx 5-6" (I used it) and ran 1/4 alaly tube next to the motor tube for the charge wires. The interstage adapter was cumshawed out of two blue tube couplers resawn to nest where the re-inforced top of the body for the sustainer and into the rear of the already sleeved bottom of the booster. Forget the 'tea bag' and rubber band stuff-strictly low power. Do the kevlar thing. Like an idiot the first (and only flight) of the sustainer by itself was an "H' and it drifted way too far as my recovery load calc was off. FWIW- I cut the strakes off the standard aerotech fins on the sustainer and rebalanced the whole thing so it was stable. Oh yeah- bulkheads in the nose cones. Lotta build time in Washington because it rains every 15 mins or 29 days out of the month for 23 hours each day. If anybody reads this from Washington (Monroe field) it was white with a red/white/metallic blue "PYRAT" outlined in red on the side. i expect it got plowed under. Sorry if this is confusing but PM me if you need clarification. It was a fun build during the long hours alone up there. I'll have to do another one. Have fun with yours! You should ask the serious stagers out there about the new electronics. Cris from Eggtimer has good stuff that's affordable and is working on a few new things I'll let him announce. You may be really interested in one of them. Straight smoke and good chutes!
wow quite the response, Thanks!

I am using 24mm Bp motors so staging electronics is not a concern, however I want to get to that point eventually. also I was thinking Tumble recovery for the booster as it weights 78.5 grams but for bigger staged rockets I will definitely go for a chute on the booster, I do have a 4X36" streamer I could use(not sure how to mount it to the booster, wrapped around the motor tube?). for altimeters I only have a perfect flight firefly and not sure I want to put a $30 dollar altimeter into a$15 dollar rocket(I am still on the fence if I want to add an eBay or not).

TimothyAReed

Well-Known Member
Do you have tube cutters to potentially cut the tube shorter? If not, you can use a strip of paper wrapped around the tube as a guide.
normally I will 3D print a tube cutting guide it only costs like 5 cents

fyrwrxz

latest photo
Apologies to the OP-these are 29 mounts an I 'assumed' (yeah I know) it was AP. Sorry. I also revised my original post with more info (hey-it was a long time ago ok?)

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TimothyAReed

Well-Known Member
unless you have a desire to use a bp E motor in the sustainer...I would suggest using the longer tube in the booster and the shorter tube in the sustainer. stagers are typically 'over stable'(nature of the beast) I wouldn't worry too much about it at this point.
Rex
Okay I got the Idea of a longer sustainer from watching a 2 stager at BARS that used that ESTES pre-made booster it was like a 4' rocket with a 6" booster!
Also I was trying to strictly adhere to the 1-2 calibers of stability because I was afraid of sever weather cocking

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TimothyAReed

Well-Known Member
Apologies to the OP-these are 29 mounts an I 'assumed' (yeah I know) it was AP. Sorry.
no reason to be sorry those are great tips for when I go bigger

TimothyAReed

Well-Known Member
unless you have a desire to use a bp E motor in the sustainer...I would suggest using the longer tube in the booster and the shorter tube in the sustainer. stagers are typically 'over stable'(nature of the beast) I wouldn't worry too much about it at this point.
Rex
uploaded a Rev3(with eBay for altimeter) if being overstable is the norm can I just increase the length of the sustainer? I do not care about high performace(is that why you make a longer booster? For more performance on the sustainer?), I'll care about performance after I get staging down.

Rex R

LV2
now that I have taken a longer look at version 1...comments; I would suggest Estes type components ('low power', thin wall tubes). I've made a few edits showing how I might do it(feel free to use some/ all/ or none as you like). you should keep an eye on what OR uses for materials default for most things is cardboard...don't think you wanted cardboard fins . note that aside from using Estes tubes and moving motors I still had a stability margin of 1.76cal that may change if the nose is lighter than what is in the file. usually over stable just means you have less far to walk to recover the rocket . have fun, looks like a nice design.
Rex

View attachment Initiator_redit.ork

TimothyAReed

Well-Known Member
now that I have taken a longer look at version 1...comments; I would suggest Estes type components ('low power', thin wall tubes). I've made a few edits showing how I might do it(feel free to use some/ all/ or none as you like). you should keep an eye on what OR uses for materials default for most things is cardboard...don't think you wanted cardboard fins . note that aside from using Estes tubes and moving motors I still had a stability margin of 1.76cal that may change if the nose is lighter than what is in the file. usually over stable just means you have less far to walk to recover the rocket . have fun, looks like a nice design.
Rex
Thanks, I probably should have mentioned that I have some ASP T-60 arriving today(which is kraft phenolic) however after you showed the cardboard fin mishap I checked and Open rock had the sustainer body tube at 3 mm thick! it is only 1 mm so the tube is not as heavy duty as you probably thought also I have 1/8" plywood fins(probably should have mentioned that, kinda thought the fins were set to plywood in OpenRock).
Also you made the Tube coupler 1.5" is there any benefits in making it so small? like I said I have never done this before and I thought a longer couple would keep the sustainer from "wobbling" during the booster burn, you know more than me though .

Rex R

LV2
ah, I did wonder a bit about all the phenolic tubes. I used the materials I am familiar with that work nicely given the motor impulse. 1.5" coupler length is the standard length for bt60 couplers, can one use longer couplers, certainly. one could also reduce the amount glued into the booster...you may find it a bit harder to be neat trying to glue centering rings while working around a 24mm motor mount(and you'll want a clean tube for staging). we're probably close to the same page when it comes staging, I've only built and flown 3 Estes multi-stage birds (number 4 has never been flown, needs a new 1st stage) am working on number 5(which is kind of my design) will it work, dunno be interesting to find out.
Rex

TimothyAReed

Well-Known Member
ah, I did wonder a bit about all the phenolic tubes. I used the materials I am familiar with that work nicely given the motor impulse. 1.5" coupler length is the standard length for bt60 couplers, can one use longer couplers, certainly. one could also reduce the amount glued into the booster...you may find it a bit harder to be neat trying to glue centering rings while working around a 24mm motor mount(and you'll want a clean tube for staging). we're probably close to the same page when it comes staging, I've only built and flown 3 Estes multi-stage birds (number 4 has never been flown, needs a new 1st stage) am working on number 5(which is kind of my design) will it work, dunno be interesting to find out.
Rex

oh okay, I did not know the standard was 1.5" ASP only carries 3" I will cut it not a problem(if you've had success with 1.5" no reason to change that) would you go with 1" in sustainer and .5" in booster for the coupler?
Also the Bought the T-60 in 30" segments so can I just use all the tubing for one rocket? see Rev5 for what I mean (this would also make the rocket over stable)

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Rex R

LV2
well if you're curious, this is my current project. kind of fun figuring out just how to build the thing. it will be gap staged and use 2 motor hooks for a 'plug and go' setup. the interstage will be vented via a pair of holes in the centering rings to the aft end of the booster. 0.5" in the booster should be plenty. I suspect that your bird will be heavier than it needs to be...but, it is your rocket build away and have fun.
Rex

View attachment rexga.ork

TimothyAReed

Well-Known Member
well if you're curious, this is my current project. kind of fun figuring out just how to build the thing. it will be gap staged and use 2 motor hooks for a 'plug and go' setup. the interstage will be vented via a pair of holes in the centering rings to the aft end of the booster. 0.5" in the booster should be plenty. I suspect that your bird will be heavier than it needs to be...but, it is your rocket build away and have fun.
Rex
wow that's quite the big bertha! also, I am purposely not going light weight&performance oriented because my flight ceiling is 2k' and I am already hitting 1400 this is more of testing the 2 stage "waters" so to say.

Rex R

LV2
the trick to help hold the altitude down is to add drag...have you considered using C11's instead of D12's as your motor of choice? heheh can't wait to hear what the RSO is going to say when he see's it.
Rex

TimothyAReed

Well-Known Member
the trick to help hold the altitude down is to add drag...have you considered using C11's instead of D12's as your motor of choice? heheh can't wait to hear what the RSO is going to say when he see's it.
Rex

C11 for which stage? sustainer, Booster, or both?

Rex R

LV2
yes, sorry couldn't resist. both stages.
Rex

TimothyAReed

Well-Known Member
Here's some work I was able to put in.

cut the 3" tube coupler down to 1.5"

the fins are not glued on just seeing what they look like

overall look of the rocket(not length is actually shorter by 12")

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BABAR

Builds Rockets for NASA
TRF Supporter
I like the look. Those sustainer fins should be fine for sta<script id="gpt-impl-0.32791263615222826" src="https://securepubads.g.doubleclick.net/gpt/pubads_impl_108.js"></script>bility purposes, although they may be a bit delicate on the landing. Kind of a tough balance, big chute gives you a nice soft landing but on a two stage a LOOOOOOONNNGGGG walk. Small chute or streamer means it comes down quicker, drifts less, BUT is going to come down a bit hard.
Will your stability calcs work out if you reverse the sweep, have them go forward, then with the engine sticking out the bottom end of the rocket on landing should impact on engine not fins? (plus I always thing forward swept fins are cool!)

Regarding engine choices, think of your goal. If it is to simply prove you can do a successful two stage flight, consider using the smallest engines you can, particularly in the sustainer. You can buy or easily make an adapter for an 18 mm engine for you 24 mm sustainer motor mount, and put an 18mm C, B, or even an A engine in it (I like A's they have a BIG nozzle which is great for sustainer gap stage ignition, but with your little or no gap, a C will work fine.)

From a "flight excitement" standpoint, I think it is more fun to watch staging flights where the rocket stages low (where it is easily seen) and the sustainer deploys low (also easily seen by the audience.) As a plus, you can quickly find the booster and sustainer and fly it again!

If you go D to D, I hope you have no winds and really big field and a streamer on your sustainer.

Straight Trails!

BABAR

Builds Rockets for NASA
TRF Supporter
Oh yeah, no matter how big that booster looks, on the ground it is going to be tiny. Bright colors, like neon fluorescents or metallic.
I flew an unpainted Flutterbye. Balsa colored. In fall. With dry leaves on the ground. Very balsa colored dry leaves........

TimothyAReed

Well-Known Member
Oh yeah, no matter how big that booster looks, on the ground it is going to be tiny. Bright colors, like neon fluorescents or metallic.
I flew an unpainted Flutterbye. Balsa colored. In fall. With dry leaves on the ground. Very balsa colored dry leaves........
I have some bright orange gloss protective enamel for the rocket, if you download the openrocket file and switch to 3d finished view you will see it

TimothyAReed

Well-Known Member
I like the look. Those sustainer fins should be fine for sta<script id="gpt-impl-0.32791263615222826" src="https://securepubads.g.doubleclick.net/gpt/pubads_impl_108.js"></script>bility purposes, although they may be a bit delicate on the landing. Kind of a tough balance, big chute gives you a nice soft landing but on a two stage a LOOOOOOONNNGGGG walk. Small chute or streamer means it comes down quicker, drifts less, BUT is going to come down a bit hard.
Will your stability calcs work out if you reverse the sweep, have them go forward, then with the engine sticking out the bottom end of the rocket on landing should impact on engine not fins? (plus I always thing forward swept fins are cool!)

Regarding engine choices, think of your goal. If it is to simply prove you can do a successful two stage flight, consider using the smallest engines you can, particularly in the sustainer. You can buy or easily make an adapter for an 18 mm engine for you 24 mm sustainer motor mount, and put an 18mm C, B, or even an A engine in it (I like A's they have a BIG nozzle which is great for sustainer gap stage ignition, but with your little or no gap, a C will work fine.)

From a "flight excitement" standpoint, I think it is more fun to watch staging flights where the rocket stages low (where it is easily seen) and the sustainer deploys low (also easily seen by the audience.) As a plus, you can quickly find the booster and sustainer and fly it again!

If you go D to D, I hope you have no winds and really big field and a streamer on your sustainer.

Straight Trails!
I have a 3d printer so I will print some adaptors. here what the club(FSA #481) says about its field "The site is free of obstructions for approximately 2000' east, north and west" so not that worried, also need to post an update because fins were glued on last Friday(been camping over the week end) however they have epoxy fillets and I am very confident in success(I also have a JLCR so bigger chute lower opening however I will fly it with c's for the maiden then go bigger for "scientific reasons")

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BDB

Absent Minded Professor
I like the look. Those sustainer fins should be fine for stability purposes, although they may be a bit delicate on the landing. Kind of a tough balance, big chute gives you a nice soft landing but on a two stage a LOOOOOOONNNGGGG walk. Small chute or streamer means it comes down quicker, drifts less, BUT is going to come down a bit hard.
Will your stability calcs work out if you reverse the sweep, have them go forward, then with the engine sticking out the bottom end of the rocket on landing should impact on engine not fins? (plus I always thing forward swept fins are cool!)
BABAR is right about the back-swept fins being an issue. I solved this on my Magnum by papering them and attaching them through the wall. (You can see what I'm getting at in this post.) He is also right about the need for a streamer or a chute with a spill hole. The Magnum is supposed to have a 24" parachute, but I cut a ~6" spill hole in it--without it I would have never found it after any of its flights.

TimothyAReed

Well-Known Member
BABAR is right about the back-swept fins being an issue. I solved this on my Magnum by papering them and attaching them through the wall. (You can see what I'm getting at in this post.) He is also right about the need for a streamer or a chute with a spill hole. The Magnum is supposed to have a 24" parachute, but I cut a ~6" spill hole in it--without it I would have never found it after any of its flights.
I am using a 9" chute, plus the fins are 1/8" plywood(not balsa), will probably use a C-11-0;C6-5 setup to bring expected altitude down to 738'

TimothyAReed

Well-Known Member
Oh yeah, no matter how big that booster looks, on the ground it is going to be tiny. Bright colors, like neon fluorescents or metallic.
I flew an unpainted Flutterbye. Balsa colored. In fall. With dry leaves on the ground. Very balsa colored dry leaves........
I hope this picture of the booster calms any worries....