Web of lines/scratches on surface of 75mm CTI case, anything to worry about?

The Rocketry Forum

Help Support The Rocketry Forum:

rocketsam2016

Well-Known Member
Joined
Aug 31, 2016
Messages
270
Reaction score
4
Has anyone seen anything like this before? I purchased this 3G 75mm never-flown case from another flyer as part of a larger purchase of used 75mm hardware. This case was bought new by them a few years ago, looked at once, then stored back in the original packaging until I bought it off of them. When I received it, I noticed that the case surface has a web of what looks like scratches in the anodized layer (but I don't really know what I'm talking about...). The web is uniform over the entire case. I got another 75mm case in the order that has flown but looks normal to me.
IMG_20170610_220902.jpg

I emailed CTI a couple of weeks ago and haven't gotten a response. I got a good deal on this purchase so I'd love to just keep everything :), I trust that the seller had not noticed this and is operating in good faith, and I understand that I'm buying not-new hardware, so I just want to make sure this isn't a major problem.
 

slaak

Well-Known Member
Joined
Jun 19, 2014
Messages
52
Reaction score
4
Its not very pretty to look at but shouldn't effect the performance of the case since anodize isn't structural. If its on the inside too you probably just want to make sure you clean it extra well after firing. Its due to a difference in thermal expansion coefficients between the aluminum case and the anodize layer. Either CTI made the anodize layer too thick or they sealed the anodize incorrectly or the case got too hot some time since it was anodized. some more info here https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19950025269.pdf https://aluminumsurface.blogspot.com/2009/06/crazing-defects-cracks-in-anodic-layer.html
 

Bat-mite

Rocketeer in MD
Joined
Dec 5, 2013
Messages
11,162
Reaction score
1,890
Location
Maryland
Sorry to say ... there have been more "mistakes" coming out of CTI since the fire. Wish we knew more about what is going on up there.
 

blackjack2564

Crazy Jim's Gone Banana's
TRF Supporter
Joined
Jan 18, 2009
Messages
9,146
Reaction score
1,315
Location
Savannah Ga
No Worries Mate!!

I have some that way, they perform just fine.
Just imperfection in surface, no bearing on structural integrality.
 

Banzai88

Lvl 1,Wallet....Destroyed
TRF Supporter
Joined
Jul 15, 2015
Messages
2,584
Reaction score
748
I have CTI and Dr. Rockets cases that look like that. All function fine.
 

mikec

Well-Known Member
Joined
May 9, 2009
Messages
2,544
Reaction score
400
Sorry to say ... there have been more "mistakes" coming out of CTI since the fire.
According to the OP this case is a few years old, so whatever the explanation is, that isn't it.
 
Top