Estes Savage Build

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Dotini

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I've acquired and begun preparing to build this 2 stage rocket kit. The literature mentions a 4.7 oz weight, and specifies only a D12-0 for the booster. My first question is why it doesn't also mention the C11-0, which is rated for a 6.0 Max Lift Weight?

I would very much desire to use the C11, since I have very easy access to a beautiful (but smallish for boosted rockets) 500' x 500' field, and would prefer to keep my launches down to the minimum altitude consistent with safety and good practice. What might be the reason Estes has omitted the C11-0 from their specified motors for this model?
 

Initiator001

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I was told that the D12-0 was the only recommended booster for many Estes kits as there was too much open space between the propellant bulkhead of the C11-0 compared to the D12-0. This could cause gas pressure to push the booster stage off the model before the upper stage motor could be ignited.
 

BABAR

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I was told that the D12-0 was the only recommended booster for many Estes kits as there was too much open space between the propellant bulkhead of the C11-0 compared to the D12-0. This could cause gas pressure to push the booster stage off the model before the upper stage motor could be ignited.
Properly vented this small gap is a non-issue. This is speaking as someone who successfully has black powder gap staged over four feet.


as @Dotini mentions posts a max lift off weight of 6 oz. that said, nice to have a slick 4 foot rod (or even better a rail), and a low wind day as mulitstagers tend to have more plumage and a bit more tendency to weatherock, but his birds don’t look particularly draggy and I think if the full Stack is under 6 oz. should be fine

the C11 has a shorter burn time, which means it will stage sooner. For me and I think for @Dotini this is a good thing

1. First priority is always safety. Even when you have enough thrust to get off the pad confidently, there is always the chance of a bit of rod whip, lug snagging a bit, or an unexpected gust of wind. In any case, a shorter burn time means IF the flight STARTS to get off vertical, it won’t get very far off before sustainer lights.

2. For small fields, keeps altitude For both booster and sustainer lower, making recovery of both easier.

3. I like to SEE the staging event, so as long as it is at least a few feet ABOVE the rod (yes, I had one stage before it LEFT the rod [long time ago I think on a B6-0] that’s a bit too underwhelming ) I am fine with relatively low staging, I like it under 100 feet.
 
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BABAR

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Remember that for the SUSTAINER motor, there is almost no limit as to how LOW you can go in power, as long as the delay is appropriate. Especially for first flights I will frequently even use a motor adapter and downsize a motor class, like an A8-5 (or 3) in a 24mm mount, or an A10-3T in an 18mm mount. This both keeps the altitude down and is a (relative) safety factor. Remember, the sustainer motor doesn't have to mess with inertia, if the booster DID its job, the sustainer is already at a stable velocity and appropriate trajectory. On the other hand, if the booster DIDN'T do its job, the sustainer is either already unstable and/or off vertical (no lockouts in non electronic black powder staging, my friend!), in which case it's going to be BAD, but the smaller the motor the LESS bad it will be. Going small with the sustainer motor also bumps up the stability of the stack, as it is less weight in the tail. Things I like about the A8 and A10-3T motors is they have larger nozzles than B, C, and other 13mm motors, so I theorize they are easier to ignite with BP staging. D12 also has a nice big nozzle, so it's also a goodie.
 

waltr

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Thanks for that idea. What would be the ideal size, number and position of the holes?
For gap staging I have done, I use one 1/4 hole close the the sustainer motor.
Never had a failure igniting the second stage.
 

n3tjm

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Thanks for that idea. What would be the ideal size, number and position of the holes?
It really depends on the design of the booster. If possible, I like putting them in the centering rings, between the fins. Or Drilling a couple holes in the side of the booster. I've gone as small as 3/16" dia. holes. In theory it shouldn't matter where the holes are since this has worked for me venting out the side and venting out of the tail.
 

BABAR

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I can tell you what I have done, not sure it is any better than other suggestions.

for no gap staging (motors taped) no vents are needed. So the following only applies to nonelectrinic black powder tape staging

minimum diameter two holes. I usually use a standard cheap notebook paper size hole punch. One on each side, prevents theoretical risk of asymmetric venting tilting the rocket. Probably overkill. this works for 13 mm to 24 mm D, I’d go with three spaced 120 degrees for an E. These holes are place about 1/8 to 1/4“ below the sustainer nozzle position in “nested” position. You need to have at least 1/4 of the sustainer motor sticking out the rear of these sustainer, 1/2” is better, as the motor itself acts as the coupler for minimum diameter birds, at least for mine.



non-minimum diameter you have a lot of options. I extend the motor mount in chimney fashion so it terminates about 1/8 to 1/4” below where the sustainer nozzle will be on boost. you still need to vent the OUTER tube.

you have multiple options, I will describe two.

the EASIEST is just to put the same two hole you would on the minimum diameter, one on each side. Distance doesn’t matter that much, as the gas will have to go all the way up the chimney to illuminate the sustainer nozzle before it can go anywhere else anyway. Just make sure the holes are not occluded by any coupler you set up, and that they are ABOVE the most forward centering ring of the motor mount/chimney.

the most ELEGANT and aerodynamic is to punch two or three holes in EACH of the CENTERING RINGS of the booster. The gas will then go UP the chimney to the sustainer, slip out the 1/8 to 1/4” circumferential gap between the end of the chimney and the sustainer motor, and the can run back DOWN the booster between the body tube and the motor mount/chimney through the holes in the centering rings, ultimately venting out the tail end. This obviously requires a bit of planning, as you need to make the holes before you glue in the mount/chimney. If the rings aren’t wide enough for that size hole, just glue them first onto the mount/chimney, then cut some notches in them before you glue in the mount. For low power you aren’t going to significantly degrade the centering rings with a few small notches. This avoids poking holes which may be less aesthetic and aerodynamic when placed on the side of the body tube.

of, if you are @neil_w , you poke the holes in the sides and put decals on labeling them “plasma vents” or “tachyon portals”
 

Dotini

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Getting farther along into the build, it is now clear that the parts alone, not counting motors, are going to add up to more than the 4.7 oz advertised weight of the rocket. That rules out the use of a C11-0, and answers that question quite firmly. Now I'm faced with the questions of how to hold down the altitude while working with the D12. Aside from using an A8-3 in the upper stage, I will add some considerable weight and drag to the model, starting with adding a baffle and altimeter, amongst other measures, possibly such as increasing the the main tube to BT-60.

@BABAR
The Savage has gap staging of a bit over 1". It also has an interesting "stage cone" which concentrates the gases and particles of the booster directly into the nozzle of the sustainer motor. I used to build these from paper into my multi-stage models from the 80's.
 
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n3tjm

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I find that with C11's that taping method is very unreliable. Those motors seem to have a lot more pressure when the propellant wall blows. And it is enough pressure to blow the motors apart before the sustainer can ignite.
 

BABAR

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I find that with C11's that taping method is very unreliable. Those motors seem to have a lot more pressure when the propellant wall blows. And it is enough pressure to blow the motors apart before the sustainer can ignite.
I would be foolish to argue with real world experience! I haven’t tape Staged anything other than 13 mm and 18 mm motors.
 

Dotini

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Booster and stage cone of Estes Savage
DSC00425.jpg


Booster and sustainer fin cans separated by booster body tube
DSC00429.jpg
 
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Dotini

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After cementing and assembling the fins units, I feel impressed with the design, fit and quality of these parts. For instance, the fins are only 0.050" thick, and come with rounded edges.
DSC00434.jpg

Since the goal of the project is to enjoy the sound and fury of the D motor at my relatively small field of 500' x 500', I have taken steps to limit the altitude. An increase in weight is gained by the addition of a full baffle in the tube and an altimeter and wee bit of plumber's putty in the nose cone. Additionally, I have added Gurney flaps to the starboard trailing edges of all eight fins. These will force the rocket to spin counterclockwise on ascent, robbing energy that would otherwise contribute to altitude. I've added a roll visibility paint scheme to the tube and two of the fins.

Since the area of each fin is about 3.6 square inches, I feel it may be justified to increase the tube diameter to BT-60 on my next build of this model, which will be another step in limiting altitude and may permit use of a C motor in the upper stage.
 

Dotini

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Not finished, but close.

DSC00437.jpg


I will be using my 4' long 3/16" diameter launch rod for this model.
 
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Dotini

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Lacking only launch lugs and touch up, this lightly bashed Estes Savage is ready for flight.
DSC00440.jpg

Equipped with D12, C6, 15" Xform chute and Alt2, this model weighs in at 7.9 oz. It would have been even heavier if I had filled and painted the tube, but it is standard except for purple Sharpie roll pattern.

I think I like this model quite a lot, and will build another with balsa transition and filled and painted BT-60 tube, likely adding another ounce or more.

This is the first model I've worked with that comes with pink components. Next time I will try for a yellower green and better purple or red violet colors to go with.

I'm looking forward to the next calm, dry day for a launch.
 

BABAR

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Looks great as usual (you shame me with your finishes on prototypes, mine never see paint, and often rarely get sanded!).
Considering your field, recommend go with an A motor on the sustainer

Main reason: distance from staging. Note I did NOT say altitude. There is a reason for that. If it stages perfectly vertically, your only problem is DRIFT, which whiile considerable at higher altitude, is not too bad with low winds. OTOH, if it is NOT perfectly vertical, than whatever component is NOT vertical is generally heading in some direction LATERAL to your launch site. Depending on how FAR off vertical staging is, a motor like a C6 can carry the rocket a looooong way from where it was launched.

Second reason: A motors have a larger nozzle bore than B or C. I haven't really had any problem with any black powder motors lighting, but I always tend to think a larger bore increases the chance of successful gap stage ignition.

Wishing you two straight trails and a couple of short walks. Designate your buddy to keep eyes on the booster descent while you keep track of sustainer. Hard for one guy to track both, and most commonly if not assigned in advance, both are watching the sustainer and nobody is keeping track of booster.
 

rklapp

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My cloned CC Express does well on the C11-0. I've experimented with C11-0 in the Booster-60 but tends to go diagonal on the boost causing the sustainer to land outside of the park. The C11-0 is fine with lite rockets like the Spirit and Chiller.

 

Dotini

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What is the secret of making the booster tumble on recovery rather than descending ballistically?
 

rklapp

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What is the secret of making the booster tumble on recovery rather than descending ballistically?
The D12-0 goes about 100ft and C11-0 goes 50ft so don't think there's much difference. Actually, I'm not sure they do descend ballistically. Seems to be either tumbling or spinning. The CC Express booster likes to spin down.

 

neil_w

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What is the secret of making the booster tumble on recovery rather than descending ballistically?
It simply needs to be unstable. You can check this in a sim program.

Typically, this is more of a concern with gap-staged models, where the longer booster is more likely to be stable and ballistic on the way down.
 

Dotini

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It simply needs to be unstable. You can check this in a sim program.

Typically, this is more of a concern with gap-staged models, where the longer booster is more likely to be stable and ballistic on the way down.
I suppose even a gap of 1 5/8", such as the Savage, is still a gap and potentially stable. We shall see.
DSC00448.jpg
 

neil_w

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My guess would be not stable, the whole thing is still pretty short. Remember that these boosters have the CG pretty far back (no weight in the nose). I expect you'll be fine (also this is something I would not expect Estes to screw up).
 
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