C.H.A.D. staging 13mm booster to 18mm sustainer

[Dotini]

How best to do this?

My guess would be to wrap the top of the booster with tape until it matches the 18mm motor diameter, then splice the two together with a final wrap of masking tape or Scotch tape. .

 

[heada]

13mm nests inside 18mm. 18mm nests inside 24mm.

You should be able to just but the forward (ejection) end of the 13mm into the aft (nozzle) end of the 18mm. A single wrap of scotch tape at the joint is all that is needed to hold them together. You can use masking tape too but I find scotch tape releases better for CHAD staging.

 

[Bat-mite]

What does CHAD stand for?

 

[David_Stack]

CHeap And Dirty...

https://www.apogeerockets.com/education/downloads/Newsletter339.pdf

 

[Sandy H.]

13mm nests inside 18mm. 18mm nests inside 24mm.

You should be able to just but the forward (ejection) end of the 13mm into the aft (nozzle) end of the 18mm. A single wrap of scotch tape at the joint is all that is needed to hold them together. You can use masking tape too but I find scotch tape releases better for CHAD staging.

For the examples I had quick access to, the nozzles of the 18mm motors were cast right at the end of the motor - a 13mm motor would not 'stick in' the case. Also, wouldn't that mean the tape would be really ripply going from 18mm to 13mm?

You could glue a proper centering ring to the top of the 13mm motor (or just cut a used 18mm motor to make a similar ring) and tape as you normally would for CHAD staging. It would add a little mass, which might be bad, as I'm not sure what the goal of staging 13mm to 18mm would be. . .

Not sure if gluing a centering ring (or similar) to the top of the motor is considered a motor modification. If so, ignore what I suggested.

Sandy.

 

[Bravo52]

It should still work even if the "tape is ripply" between the two motors. Unless there is a manufacturing problem with the ejection charge on the 13 mm or the main charge on the 18 mm, the force needed to break the ripply tape should be great enough to allow for ignition. I've had staging occur with no tape...

 

[Sandy H.]

It should still work even if the "tape is ripply" between the two motors. Unless there is a manufacturing problem with the ejection charge on the 13 mm or the main charge on the 18 mm, the force needed to break the ripply tape should be great enough to allow for ignition. I've had staging occur with no tape...

Just to clarify, is this what the consensus is to address the OP's initial question?

Sandy.

 

[heada]

Just to clarify, is this what the consensus is to address the OP's initial question?

Sandy.

Yup. On my motors, the fit is so snug that I can hold the pair by the 13mm without the 18mm falling off. The tape is almost not needed. The 13mm only goes into the 18mm 1/8th inch or so but that's all that is needed.

 

[Cape Byron]

It would add a little mass, which might be bad, as I'm not sure what the goal of staging 13mm to 18mm would be. . .

I would guess the OP wants staging to occur as low as possible. It's cool to see when it happens.

 

[Sandy H.]

Yup. On my motors, the fit is so snug that I can hold the pair by the 13mm without the 18mm falling off. The tape is almost not needed. The 13mm only goes into the 18mm 1/8th inch or so but that's all that is needed.

Interesting. On the particular (random) motors I pulled out of the box, the 13mm won't stick in more than 1/32-ish and it won't hold the A8-3's weight before it falls off. I pushed them together as hard as I could by hand (no vise or something crazy like that) and the 13mm motor is significantly out of angle with the 18mm.

Just the first two motors I picked up, maybe some others in the box would mate more like you have seen. Probably smart to do a sanity check and if your motors don't mate up well, pick a different combination, assuming you have a stash available. It is rocket science after all!!!

Sandy.

 

[Sandy H.]

I would guess the OP wants staging to occur as low as possible. It's cool to see when it happens.

In that case, a little mass wouldn't be that bad. I didn't think about that reason for staging, but it seems legitimate in hindsight.

Sandy.

 

[heada]

I pulled a random A3-4T and it matched up to a random C6-5. Chamfered the end if the A3 with my thumbnail before I tried. I don't have any 13mm booster motors.

 

[Cape Byron]

In that case, a little mass wouldn't be that bad. I didn't think about that reason for staging, but it seems legitimate in hindsight.

I've done a little noodling with high drag booster stages to get low staging altitude. An ongoing project.

 

[Dotini]

For the examples I had quick access to, the nozzles of the 18mm motors were cast right at the end of the motor - a 13mm motor would not 'stick in' the case. Also, wouldn't that mean the tape would be really ripply going from 18mm to 13mm?

You could glue a proper centering ring to the top of the 13mm motor (or just cut a used 18mm motor to make a similar ring) and tape as you normally would for CHAD staging. It would add a little mass, which might be bad, as I'm not sure what the goal of staging 13mm to 18mm would be. . .

Not sure if gluing a centering ring (or similar) to the top of the motor is considered a motor modification. If so, ignore what I suggested.

Sandy.

I really appreciate all the replies to my question.

Currently the one I like the best is the suggestion to saw a used 18mm motor casing to make a centering ring. This will be with enough purchase, say 1/4", on the 13mm motor to ensure very good alignment with the upper stage. Thrust from the booster will not be off axis. Also the tape application will be nicer looking. I don't think gluing would be desired.

My goal(s) of CHAD staging a 13mm to 18mm are several:
1) To exploit the efficiency properties of the A10-0T relative to 18mm boosters. It has a Max Lift Weight of 4.0 oz, which equals the B6-0 and C6-0, and exceeds the A8-0. Yet it has an initial weight that is less than half the 18mm motors.
2) The weight saved by dispensing with an airframe and fins for the booster and using a more efficient 13mm motor could be put into lifting a somewhat larger, heavier and more visible upper stage.
3) My easy access launching field is limited to 500' x 500' of beautifully tended grass, beyond which are trees, wires and roads. But I hope to still experience and enjoy multi-stage rocketry by strictly limiting the altitude which boosted rockets are easily capable of.

I will use a yellow Sharpie on the motor and ring to make recovering it after launch easier. Also I will ensure that my upper stage is plenty stable to handle the extra 1/4 oz of weight on the tail at lift off.

 

[Dotini]

This BT-55 model, at 21.5", 3.16 oz with A8-3, parachute and altimeter, might be a good candidate for CHAD 13mm boost.

 

[Dotini]

I've changed my mind about the above rocket being suitable for 13/18 CHAD boost. It's really too heavy. Instead I'll go with this one of quite a bit less weight. It'll be less likely to become confused about where it's going during the latter rather weak part of the A10's thrust curve.

 

[BEC]

Yeah, you really need to watch out for that long, weak tail of thrust on the A10. Even on a light model (my little Estes Checkmate) one can sometimes see the model seem to struggle to keep climbing during that low-thrust tail.

 

[Dotini]

Yeah, you really need to watch out for that long, weak tail of thrust on the A10. Even on a light model (my little Estes Checkmate) one can sometimes see the model seem to struggle to keep climbing during that low-thrust tail.

View attachment 483057

That's a very pretty model and a superb looking field. What is the facility?
I was up at 60 Acres today for the first time. And it was awesome like this place looks to be.

 

[BEC]

That is Sixty Acres North, looking west east and a little bit south.

 

[Alan R]

Why not just gap stage here?

 

[Dotini]

Why not just gap stage here?

Merely to reduce the part count, weight and complexity to the absolutely bare minimum essentials. It's an exercise in minimalism. No purpose is served by adding more tubes and centering rings, other than aesthetics or visibility during recovery. It would be entirely redundant structurally, since it would be not carrying fins. And there would be the downside in adding/moving weight aft. But yes, after I successfully launch, recover and collect my data, I may well build and paint some tubes and rings to house my booster, as it would sure look better on the the shelf. They don't call it Cheap and Dirty for no reason.

 

[Alan R]

Merely to reduce the part count, weight and complexity

What I meant was ... a gap staging you don't have to stick the motors together at all, doesnt require anything extra other than just putting the top of the 13 close to the 18 and the 18 will ignite.

 

[Dotini]

What I meant was ... a gap staging you don't have to stick the motors together at all, doesnt require anything extra other than just putting the top of the 13 close to the 18 and the 18 will ignite.

Well okay, now I'm confused. I guess I don't understand gap staging although I've launched a 4 stage rocket with 8'' gaps between each engine. What would locate the 13mm motor to the upper stage or hold it near the 18mm motor?

 

[Alan R]

Well okay, now I'm confused. I guess I don't understand gap staging although I've launched a 4 stage rocket with 8'' gaps between each engine. What would locate the 13mm motor to the upper stage or hold it near the 18mm motor?

it looked to me (above, the yellow-tailed rocket) that you have a 13mm motor tube that you're going to drop off the rear. That's what would be holding it. Or I misunderstood

 

[Dotini]

Here it is. How could it be gap staged without anything extra?


13mm CHAD device for 18mm motor consisting one piece of scotch tape and 1/4" ring sawn off used 18mm motor.

 

[Alan R]

ah. now I get it.

 

[Alan R]

In the first pic you had of this, I thought the yellow part below the fins was the 13mm and the 18 was inside that. and the whole yellow part was going to drop.

 

[Dotini]

That yellow part is mostly a reversed Estes Mongoose fin can, with about 1/2 inch of motor mount tube extending aft to provide a place for taping the sustainer in place.