# Why aren't there many 18 mm composites?

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##### Well-Known Member
When it comes to 18mm composites as far as i know there are only 3 the D21, D24, and the D13. Why Is it that there are only 3?

#### ben_ullman

##### Well-Known Member
The main reason being cost.

I can pack 2 6" O motor grains in the same time it takes me to pack 5 18mm loads. A manufacturer can get say $500 for 2 O grains versus$25 for 5 18mm.

Plus there just isn't a market for 18mm composites like there is i bigger sizes.

Ben

##### Well-Known Member
but it goes both ways you can get 18mm reloads at about half the cost of a 24mm reload and you can use adapters

#### ben_ullman

##### Well-Known Member
but it goes both ways you can get 18mm reloads at about half the cost of a 24mm reload and you can use adapters
Well, it almost doesn't go the other way

Otherwise there would be alot more of them on the market. The cost return is just not there. No matter if you say more people would buy 18mm then 24mm the money just isn't there with the labor involved.

Ben

#### The EGE

##### Well-Known Member
Don't forget the Apogee D10W. It's got -3, -5, and -7 delays.

There's also not a lot of market for 18mm composites because they're just too powerful for most 18mm rockets. A D21, or even a D13, will shred a lot of them, or launch them so high that they're very hard to recover. As Ben pointed out, there's no real reason to use them in a 24mm rocket when D12s are available and cheaper. They also can't be

The only major uses for them are Machbusters like yours, the occasional rocket (like my Rama) that is too heavy for a C6, and the occasional contest model.

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#### daveyfire

##### Piled Higher and Deeper
Otherwise there would be alot more of them on the market. The cost return is just not there.
There can also be significant technical challenges in very small composite motors, including efficiency problems and ignition methods.

##### Well-Known Member
well actually D12's sell at about $12 dollars and a 3 pack of reloads for a 18/20 is$7.90 at valuerockets.com

Here is the chart
D12 D24/D13
1) $12$38 (casing and motor)
2) $24$46
3) $36$54
4) $48$62
5) $60$70
6) $72$78
7) $84$86
8) $96$94 THE RELOAD HAS BEAT THE D12!!!!!!

#### The EGE

##### Well-Known Member
There can also be significant technical challenges in very small composite motors, including efficiency problems and ignition methods.
Also true; I assume these are why AT no longer sells B, C, and E 18mm loads...

##### Well-Known Member
Use a q2g2 igniter

#### ben_ullman

##### Well-Known Member
Use a q2g2 igniter

Ben

##### Well-Known Member
Quest has no composetes and the ppl at quest are friendly they will allow a production lisinse

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#### skip_dye

##### Well-Known Member
well actually D12's sell at about $12 dollars and a 3 pack of reloads for a 18/20 is$7.90 at valuerockets.com
...but once I use my 40% off coupon at Micheal's......

Also, the first two online retailers I check sell D12 for less that $10. I used a friend's 24/40 casing once.....to much of a PITA to use. Way to easy to get grease on the delay element. I can only imagine how much more difficult the 18/20 is to use. I would bet that 18mm rockets are probably marketed more toward kids. One must be 18 to buy composite motors. https://tinyurl.com/ajh2f Not a good idea to have a product that most users can't even buy. My philosophy is this....Anything I build that I would want will fly on a D, I would probably want to fly on a E. So I put a 29 MMT in it to keep my options open (F, G, etc). Alan NAR & TRA L2 #### ScrapDaddy ##### Well-Known Member ...but once I use my 40% off coupon at Micheal's...... Also, the first two online retailers I check sell D12 for less that$10.

I used a friend's 24/40 casing once.....to much of a PITA to use. Way to easy to get grease on the delay element. I can only imagine how much more difficult the 18/20 is to use.

I would bet that 18mm rockets are probably marketed more toward kids. One must be 18 to buy composite motors. https://tinyurl.com/ajh2f Not a good idea to have a product that most users can't even buy.

My philosophy is this....Anything I build that I would want will fly on a D, I would probably want to fly on a E. So I put a 29 MMT in it to keep my options open (F, G, etc).

Alan

NAR & TRA L2
Ok fair enough price is almost equal. But in the long run you will save money, and you will get more power but the 18mm size is not only for kids it is a great area for 1)record setting 18mm has less drag then a 24mm 2) machbusting 3) most importently for people who are on a budget: D

#### daveyfire

##### Piled Higher and Deeper
Use a q2g2 igniter
In an 18mm motor, a twin-lead igniter like a Q2G2 can take up a significant portion of the throat area. This not only increases chamber pressure at startup, but also creates a significant pressure drop as the leads are ejected through the throat. Depending on the propellant composition, this pressure drop can trigger combustion instability, or even extinguish the motor.

#### JAL3

##### Well-Known Member
In an 18mm motor, a twin-lead igniter like a Q2G2 can take up a significant portion of the throat area. This not only increases chamber pressure at startup, but also creates a significant pressure drop as the leads are ejected through the throat. Depending on the propellant composition, this pressure drop can trigger combustion instability, or even extinguish the motor.
I don't have the experience or the background to comment on this assertion. What I can assert is I get Copperheads to ignite the motor about 70% of the time. With the Q2G2, I am at 100%.

#### daveyfire

##### Piled Higher and Deeper
What I can assert is I get Copperheads to ignite the motor about 70% of the time. With the Q2G2, I am at 100%.
As I said, it depends on propellant composition and motor design. (We're very blessed with HTPB, from a combustion stability standpoint.) For different 18mm composite motors, things may (will) change. You may not even be able to fit an igniter through the throat of an 18mm APCP B motor. Longer 18mm motors become more workable from an igniter standpoint (cf. some of Rocketjunkie's designs, or Kosdon's 18mm G motors :cyclops since the throat diameter grows as well.

edit: Not to say that these challenges aren't insurmountable. They're a fun problem to solve. But a commercial manufacturer may not want to deal with the trouble, when there's money to be made elsewhere.

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#### JAL3

##### Well-Known Member
As I said, it depends on propellant composition and motor design. (We're very blessed with HTPB, from a combustion stability standpoint.) For different 18mm composite motors, things may (will) change. You may not even be able to fit an igniter through the throat of an 18mm APCP B motor. Longer 18mm motors become more workable from an igniter standpoint (cf. some of Rocketjunkie's designs, or Kosdon's 18mm G motors :cyclops since the throat diameter grows as well.

edit: Not to say that these challenges aren't insurmountable. They're a fun problem to solve. But a commercial manufacturer may not want to deal with the trouble, when there's money to be made elsewhere.
Understood.

##### Well-Known Member
Ohh kosdon makes 18mm g's?

#### Initiator001

##### Well-Known Member
I was working at AeroTech when the 18mm RMS 'B' & 'C' reloads were cancelled.

As I was reviewing the sales data at that time, the 'B' & 'C' reloads had been ordered exactly ONCE by each of the hobby distributors/dealers. There had been no re-orders in over six months and no indications that there would be any orders.

I then made a presentation to the owners of AeroTech concerning this development and my recommendation was to discontinue these small reloads. My recommendation was accepted and as far as I know, AeroTech never received any flak over discontinuing the 'B' & 'C' reloads.

They just never sold enough to justify keeping them in production.

#### The EGE

##### Well-Known Member
I was working at AeroTech when the 18mm RMS 'B' & 'C' reloads were cancelled.

As I was reviewing the sales data at that time, the 'B' & 'C' reloads had been ordered exactly ONCE by each of the hobby distributors/dealers. There had been no re-orders in over six months and no indications that there would be any orders.

I then made a presentation to the owners of AeroTech concerning this development and my recommendation was to discontinue these small reloads. My recommendation was accepted and as far as I know, AeroTech never received any flak over discontinuing the 'B' & 'C' reloads.

They just never sold enough to justify keeping them in production.

That makes sense, I suppose. It prolly wan't ecomomically viable to compete directly with Estes BP motors.

#### Der Red Max

##### Well-Known Member
...and my recommendation was to discontinue these small reloads. My recommendation was accepted

##### Well-Known Member
YOu did kill the b and c motors!!!

##### Well-Known Member
YOu did kill the b and c motors!!!
He's a MURDERER!!!!!!!!!!!! :shock:

##### Well-Known Member
i really wish at least the E25 was available

#### MarkII

##### Well-Known Member
I was working at AeroTech when the 18mm RMS 'B' & 'C' reloads were cancelled.

As I was reviewing the sales data at that time, the 'B' & 'C' reloads had been ordered exactly ONCE by each of the hobby distributors/dealers. There had been no re-orders in over six months and no indications that there would be any orders.

I then made a presentation to the owners of AeroTech concerning this development and my recommendation was to discontinue these small reloads. My recommendation was accepted and as far as I know, AeroTech never received any flak over discontinuing the 'B' & 'C' reloads.

They just never sold enough to justify keeping them in production.
Gary also said that in a thread on one of the forums (either here or at YORF) last year. I'm not sure if the thread was actually about these topic, but I do remember asking about them at one point, and then seeing his response. I was wondering about the same thing as ScrapDaddy.

MarkII

##### Well-Known Member

MarkII
Great Minds Think Alike

#### MarkII

##### Well-Known Member
Great Minds Think Alike
As you look at the selection, you almost inevitably wonder about it at some point. But if Aerotech started making them again, how many B and C reloads do you think you would ever actually buy? (Be honest.) My own take is that rather than fret over the fact that there are only a couple of reload formulations on the market currently for the 18/20 RMS case, instead I appreciate the fact that the 18/20 RMS system even exists at all and that someone makes commercial-grade reloads for it. That's pretty cool when you think about it. If sufficient interest ever built up for 18mm B and C reloads, Aerotech would no doubt consider making them again.

Propellant research by hobbyists is not a subject for this forum, but I will just mention in passing that there is at least one manufacturer of 13mm reload cases for use in research. That form factor is pretty darned small.

MarkII

Wow 13mm!