Weird Open Rocket Happenings With 13 mm Estes Engines

[BABAR]

The large variation in static CG/CP relationship is what I was alerted by and why I went to the Estes motor data first. That's when I asked here, as I expected very static stability change.

With the 'new' A10 data loaded the stability change between A3 and A10 is essentially zero, more like the expected result.



Absolutely. Anecdotally I always test a new 13 mm rocket with an A10 before I fly with an A3. The final altitude is slightly less, but the initial thrust is higher with the A10.

BTW, 13 mm motors are great and underrated by a lot of people. Four flights for the price of three!

Yup, basically with a cheap Estes adapter (or easy enough to make) the A10-3T can be used to replace the A8-3.
And at 5.25 grams plus adapter (mine is 4.4 grams, it has a piece of Mylar tape to keep the sides together although not needed) the total is 9.65 grams, compared to 16.35 grams for the A8.

HOWEVER, the A8s sell in a bulk pack, so if you fly a lot and use those, the price difference may go away.

from AC supply

4 A10-3T for $6.17. So about $1.54@ piece?

24 bulk pack $43.19, so is $1.79

so still come out ahead with the A10

at hobby lobby the bulk pack of A8-3s is $39.99, so $1.67,
the A10-3T is $6.99 for 4, so $1.74, so a few pennies ahead with the bulk pack.

although what I DO like about the bulk packs is they come with wadding and 36 instead of 12 igniters, the latter a big plus in my opinion.

 

[Cape Byron]

In Oz we can get prices as low as AC Supply, but it's called shoplifting and frowned on by vendors and the constabulary.

The going price for a bulk pack of 24 A8-3 is $125 ($92 US). A pack of four A10-3T is $26 ($19 US). If anyone ever wonders why rocketry isn't more popular over here it's basically financial.

 

[BABAR]

In Oz we can get prices as low as AC Supply, but it's called shoplifting and frowned on by vendors and the constabulary.

The going price for a bulk pack of 24 A8-3 is $125 ($92 US). A pack of four A10-3T is $26 ($19 US). If anyone ever wonders why rocketry isn't more popular over here it's basically financial.

I guess that’s why I read a lot of water rocket accomplishments from down under. They haven’t jacked up the price of water quite as much.

 

[BrendanH69]

They haven’t jacked up the price of water quite as much.

Don't go around saying that out loud.......you'll given them ideas!