# 6g 29 vs 2g 38

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#### ActingLikeAKid

##### Well-Known Member
Is there any advantage/disadvantage to launching a larger 29mm motor vs. a smaller 38? Same rocket, similar impulse, 38mm motor tube, the 29 would have an adapter.

Thoughts?

#### Bat-mite

##### Rocketeer in MD

Check the weight of the 38mm vs. the 29mm plus adapter. Then compare that weight with thrust requirements and sim altitude. If using motor ejection, check for appropriate delay times.

#### MikeyDSlagle

##### Well-Known Member
With the weight also double check stability, the 38m will have most of the mass at the business end whereas the longer 29 will have it up through the body tube.

#### qquake2k

##### Captain Low-N-Slow
A lot of 29mm reloads are able to ship without a hazmat fee.

#### emckee

##### Well-Known Member
Longer burn times are possible with 38mm motors than 29mm, just as a function of the propellant web.

Also, there may be a cost advantage to doing one over the other as well. If you look at the transition from 38mm to 54mm, you can frequently get a better price point (at approx the same impulse, or more impulse for the same \$) for the long 38's rather than the smaller 54's - at least as far as Aerotech is concerned.

#### markkoelsch

##### Well-Known Member
What you will generally find is a higher average thrust for the 29-6g as more propellant surface is burning at a given moment.

A case in point would be the Aerotech H180 white lightning versus the H123 white lightning. In terms of total impulse the H123 edges the H180 by a few newtons, and has the higher average thrust.

Thanks, all!!

#### Flyfalcons

##### Well-Known Member
38 will be easier to clean.