Number of body tubes

[MetricRocketeer]

Hi TRF colleagues,

Consider the LOC/Precision LOC-VII as an example. Probably other examples exist.

Below the nose cone, this rocket has three body tubes -- an upper, middle, and lower body tube. So, why does it have so many body tubes? Why not just two body tubes, or even one? I understand, of course, that a multistage rocket needs to have multiple body tubes. But the LOC-VII is a single-stage rocket. What do the other body tubes contribute? They certainly add to the complexity of constructing the rocket, because now we need tube couplers.

I can see reasons for having two body tubes:

> A very long body tube is inconvenient to work with.

> A very long tube makes attaching a recovery harness to the forward side of the forward centering ring difficult.

> If you wanted to employ electronic dual deployment, then you would place the DD device in the upper body tube.

Fine. But I don't understand the reason for having three body tubes.

Could any of my TRF colleagues please weigh in here.

Thank you.

Stanley

 

[sriegel]

Might just be the stock tubes are not long enough to span the whole length from tail to av bay for the lower section.

Also, some prefer to break the lower body at the fin can vs the av bay as that is less likely to zipper the tube.

 

[DigBaddy]

It does cost more to ship longer packages. Avoiding one long BT can save on shipping costs; improving sales/profit/competitiveness for the vendor.

 

[jmasterj]

Optimally (for the rocket) you'd make it out of less tubes, but as the other posters have mentioned, production and transport dictate different tube sizes.

If you want really long single tubes you can look at mailing tubes; they are available much longer than LOC tubes.

 

[tsmith1315]

Variety. It’s the spice of life!

 

[boatgeek]

A very long tube might need a larger ejection charge than is standard on commercial motors. You can add more BP, but you (a) have to have it and (b) have to remember to put it in.

 

[dr wogz]

it's a also a stocking / inventory issue..

if you only stock 12" and 18" and 32" tubes,

you can have: (not including nosecones)
a 32" + 12" = 46" rocket (with a 12" av bay)
a 12" + 12" = 24" rocket
a 12" + 18" = 30" rocket
a 18" + 32" + 12" = 62" rocket (with 12" av bay)
a 32" + ...

you get the idea..

(The more a manuf. buys of one part, the part is usually cheaper with greater quantities ordered.. many companies offer 'qty discounts' on parts..)

 

[Tractionengines]

Shipping cost, AND Shipping damage claims.

All the shipping companies have a length overwhich the costs jump.

Long skinny boxes more subject to something landing on the middle of them in transit and squashing the tube inside.

 

[MetricRocketeer]

Hi TRF colleagues,

I thank all of you for your excellent replies, which clarified the issue tremendously.

Stanley

 

[kramer714]

For the Jr Level 1 i suggest he kids use a Madcow DX3. Since it splits in the middle it is easy to fit a bunch of them in a car trunk......

 

[jimzcatz]

It does cost more to ship longer packages. Avoiding one long BT can save on shipping costs; improving sales/profit/competitiveness for the vendor.

Thats the correct answer. Its a shipping matter totally.

 

[Antares JS]

*deleted*

Never mind, reading comprehension fail on my part.

 

[cbrarick]

sometimes you just need more then one tube for transportation and storage.
"Another Bad Idea" has SEVEN body tubes.
to be fair, it's 3 inches in diameter and 28 feet long...........a 14 foot fin can would be a pia to transport.

 

[MetricRocketeer]

"Another Bad Idea" has SEVEN body tubes.

Hi @cbrarick,

Could you please post a link to this rocket. I am trying to see what it looks like.

Thank you.

Stanley

 

[cbrarick]

just may be one of the largest super-rocs out there....it's on a 20 foot rail, kinda sticks off the top a little

 

[MetricRocketeer]

just may be one of the largest super-rocs out there....it's on a 20 foot rail, kinda sticks off the top a little

Hi @cbrarick,

Is this from a kit?

Thank you.

Stanley

 

[cbrarick]

my rocket, "Another Bad Idea" was just something that came out of my evil genus. There's no kit. 100% scratch built.
my next, "A Terrible Idea" is on the drawing board, we'll see if it comes to life.
If it flies it will dwarf "Another Bad Idea" and I'm gonna claim the largest HPR super-roc, even though that designation doesn't exist!

 

[cbrarick]

hmmm got a quote for 8 CF tubes, 7 couplers & 7 vent bands.......