WinRoc Alt Accuracy

[Bravo52]

Just wondering about the accuracy of the altitude predictions in WinRoc 4.5. I have a Nuke Pro Max that weighs in at 25.3 oz with a G64 and it is showing an alt of 1646 ft. I want to use it for my L1 with an H128. The sim shows 2416ft. Every post on the board says it’ll go 3000+ on that motor! So who is right?

v/r
Bravo

 

[cjl]

Probably the people on the board - winroc IIRC uses a constant and user inputted Cd, which allows for significant variation on altitudes depending on the accuracy of that value. Rocksim is a bit more accurate, but I would trust personal experience over both software packages.

 

[LarryC]

Would suggest you find a Cd value that is consistent with your G64 altitude by repeated sims in WinRoc. Use this value in the H simulation. The resulting value should be a slight under-estimation of your flight summary Cd on the H - unless you get fin flutter or some other mechanical failure on the bigger motor.

You might try the simulations with Cd+/- 0.2, just to get a feeling for the sensitivity to the accuracy of the value.

Finally, check the WinRoc impulse value and compare it with the manufacturer's specification. These things can vary over time.


Luk and Regards,
-Larry C.

 

[tquigg]

I've been using Winroc for years with no problems. I use it in conjunction with Aerodrag software to find the Cd. I've made a few flights with an onboard recording altimeter, and have come within about 100 feet or so of each altitude prediction so far. I prefer Winroc over the other programs, as I don't have to "build" a rocket in order to conduct a flight simulation. Just plug in some numbers and hit "run".....

 

[LarryC]

Would suggest you find a Cd value that is consistent with your G64 altitude by repeated sims in WinRoc. Use this value in the H simulation. The resulting value should be a slight under-estimation of
your flight summary Cd on the H

.

Oops! I meant the altitude is a slight under-estimate. The flight summary Cd is a slight over-estimate!


(Sorry to reply to my own post)