=Scale= LTV Scout/Roc Sim question

I need one of the really good Roc sim gurus to look at the sim I made for my LTV Scout.

The flight simulation has me baffled!

Oh I got it to work just fine but the results...

OK, 699' on a D12-5 that sounds about right...pretty good actually!

But then when I plug in an E9-6...1,417 feet!!

Going from an Estes D12 to an Estes E9 will make a difference of 700'...REALLY???

I don't think so...but I could be wrong...nah! That just ain't right

I gotta be missing something pretty obvious.

Sandman: here is what I got. I reran the simulations....

Rosko, I ran it again and got.

684' with a D12-5

1384" with an E9-6

Why am I getting different altitudes and why is there such a big difference between a D12 and an E9 motor?

Almost twice the altitude difference?

Is that right?

The only change I made was to add 2" to the tube with the parachute (an oops on my sim input) but that's all I changed.

But really...almost 1,400' on an E9 in a 39" rocket?

And why is my E9 sim more than 100' higher than yours? And D12 50' lower?

Am I doing something wrong?

Gordon,

I looked over your design; its obvious you like turning balsa wood! It would be interesting to see these pieces after you are finished shaping them.

The only thing I found out of place in your simulation is the parachute weight. I substituted in a 3 oz mass overide for the parachute weight, the weight of a 20 inch skyangle 'chute. The simulation now gives 454 feet on a D12-5 and 794 feet for the E9-6. I also used the RockSim equations for the simulation. The E9-6 deploys at around 70mph and the E9-4 is not any better.

See the simulation file attached.

Bruce S. Levison, NAR #69055

Bruce! you were right there when I was painting it at NARAM!

454' and 794' well, THAT make a little more sense (altitude wise)to me!

I've flown it with an E9-6 and it sure wasn't going 70mph when the chute deployed!

It worked just fine with that motor but...it sure wasn't at 1,400' that's for sure.

I used an Estes 18" parachute right from the RocSim database.

Is there THAT much difference?

Gordon,

Now I remember that rocket, it had a perfectly turned nose cone and transitions!

Weight is a big factor for this model with the 0.2 ounce Estes 18" chute in the simulation I get a 737 foot altitude with a D12-5, total rocket weight 4.8 ounces. With the heavier 3 ounce skyangle chute this brings the alt down to 454 feet, total rocket weight about 7.5 ounces.

Do you know the real weight of this rocket fully prep'ed with no motor in it? Since I know you use heavier balsa and tend to paint on the heavier side I would guess the rockets final weight is more than 4.8 ounces and probably more like 6.5 ounces.

Bruce S. Levison, NAR #69055