Max Liftoff Weight of Estes motors
 

Hey all,

I've been working on a project (http://www.oldrocketforum.com/showthread.php?t=6641), and as I'm doing the swing-testing and adding nose weight, I'm getting really close to 113g but not yet stable. According to the NAR website (http://www.nar.org/SandT/pdf/Estes/C6.pdf), that 113g is the mass that Estes has recommended as the Max Liftoff Weight for B and C motors.

My question is, how critical is that Max Weight? If I go over by a few grams (115~120g total weight), will I be OK? I would have to imagine that there's some sort of safety margin built into that 113g spec.

Thanks,
EV

The max recommended weight is related to speed as it leaves the launch rod. If you use a longer rod, the extra quarter-ounce or so should pose no threat.

(Bob waits to be shot down by his betters for speaking out of turn. :-) )

It has about as much to do with the coast phase as it does liftoff velocity. Check the C6-3 vs C6-7. Their thrust curves are the same and they have the capability to lift the same amount, yet the C6-7 is rated for lighter rockets due to the delay. The extra weight of the longer delay grain is negligible compared to the 2.5 oz vs 4.0 oz liftoff weight between the two motors. You have to consider both when choosing your motors. :)

BTW, I can't see the pics in your thread here at work, but I recall it's going to be pretty draggy. That would make me worry a little more about the max weight of the rocket because you might end up with a really late deployment. I'll try to remember to look at the pics again this weekend.

If you have a bunch of guys in your club that fly oddrocs, they can probably look at it and hold it in their hand and give you a pretty accurate prediction of the flight profile on a C6-3. They will probably be a lot more accurate than you could calculate with RocSim.

Somthing I have noticed
 

C's and B's seem to have the same lifting ability ( off the line) and c's more or less just have a 2x longer burn time , that being said . B's are lighter ... and since they have to lift themselves , technically b's can out lift c's in the same rocket.

Or just do what i would do , punch a few 1/2 inch holes and add a few a10's :) they will coax it off of the ground

Extra tubes?
 

EV,

You have those extra tubes in the wings and the extra body support tube you can put motors into. :confused:
Would but something to see launch! :eek:
Just thinkin' out loud again. :rolleyes: :D

Yes, but try launching a heavy rocket that does ok on a C6-3 with a B6-2 and you may end up with a core sample.

you b right
 

I was simply speaking of lift off , ....... I actually did that miscalc a few weeks ago loaded up bt80 red max clone with 3 b-6's only 2 light and it archrd at around 30 ft

It did clear the rod nicley however

I don't know if you have thought of this, but you can explore the use of the 18mm AeroTech SU or RMS motors.

Greg

3 D21T SU 18mm Aerotech motors in a 3x18mm cluster mount BT80 rocket should fly really well.