Difuminar: 9500 feet and Mach 1.5 on a CTI G150

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drew
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Re: Difuminar: 9500 feet and Mach 1.5 on a CTI G150

Postby drew » Tue May 09, 2017 2:40 pm

Also in future you might want to consider not using JB Weld for anything other than bonding metal components. It's incredibly brittle an over time with reasonable usage I suspect those fillets will end up cracking.
Andrew Hamilton
AMRS 28 L3
AMRS Records Committee Chairman
Max Alt AGL - 23,908ft - K300 - Balls 22
Max V - 2,488 ft/s, ~Mach 2.2 - M2250 - THUNDA 2015

TRFfan2
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Re: Difuminar: 9500 feet and Mach 1.5 on a CTI G150

Postby TRFfan2 » Mon May 15, 2017 12:26 am

OverTheTop wrote:Marty, I like your idea of putting more realistic values for wind into the sim.

Remember that sims are only approximations to reality (refer to my sig below). I would be using even higher values than the safety code, just to see what the sim produces when prodded.

A pass in one simulation (or many for that matter) does not give you any feel for how much margin the design has for performance. It can result in a false sense of security. Simulating failures will be a better indication of design margins.
+1


strud wrote:From here : http://site.skygeek.com/MSDS/j-b-weld-8265-cold-weld-compound.pdf

SG : 1.9313

http://www.fiberglasssupply.com/pdf/msds/3MGlassBubbles.pdf

SG: microballoons : 0.12 to 0.6

SG typical epoxy : (West Systems 105) 1.15

So assuming about 30% microballons by volume, overall SG for epoxy + microballon mix would be around : 0.9
Ok i entered that in the sim to get a weight estimate, stability is still fine.

drew wrote:Also in future you might want to consider not using JB Weld for anything other than bonding metal components. It's incredibly brittle an over time with reasonable usage I suspect those fillets will end up cracking.
Should i use Proline 4500?

drew
Southern fried goodness
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Posts: 946
Joined: Sat Aug 01, 2009 10:20 pm
Location: Perth

Re: Difuminar: 9500 feet and Mach 1.5 on a CTI G150

Postby drew » Mon May 15, 2017 11:33 am

TRFfan2 wrote:Should i use Proline 4500?


I like Proline 4500 and if you have some laying around I'd recommend using it over the JB Weld. That said given the maximum speed this rocket will see you'd be more than fine with West Systems. In future you probably want to save JB Weld only for bonding motor retainers.
Andrew Hamilton
AMRS 28 L3
AMRS Records Committee Chairman
Max Alt AGL - 23,908ft - K300 - Balls 22
Max V - 2,488 ft/s, ~Mach 2.2 - M2250 - THUNDA 2015

TRFfan2
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Joined: Mon Feb 29, 2016 7:52 am

Re: Difuminar: 9500 feet and Mach 1.5 on a CTI G150

Postby TRFfan2 » Tue May 16, 2017 12:00 am

drew wrote:
TRFfan2 wrote:Should i use Proline 4500?


I like Proline 4500 and if you have some laying around I'd recommend using it over the JB Weld. That said given the maximum speed this rocket will see you'd be more than fine with West Systems. In future you probably want to save JB Weld only for bonding motor retainers.
I was going to get proline but they had it out of stock for a couple of months in the store so i got jb weld instead.


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