Taking the Big Bertha to new lengths

[Commander]

Yes Final color has been sprayed and no problem with the crazing re-appearing.





While not totally finished (I need to apply a clear coat), This appears to have been a successful operation with a new procedure found in dealing with a nasty cancer plaguing spray painters for years.

[Trident]

I've never seen crazing in primer coats? Did you have incredibly bad humidity that day? The few times I've had crazing is when I've used different brands of paint and had bad reactions between the two. The only other thought might be some kind of contamination, possibly even transferred by your bare hands to the patched area? I've been buying the super thin nitrile gloves to wear while painting. Keeps paint off the hands obviously, but also keeps any skin oils off the areas where painting will be done.

I recycled my first non-emptied paint cans the other day. Decided I just would likely never use them up. They were either of the category of "not crazy about the color", or that the paint is no longer available, and I just don't know how I'd use them up -- other than having some rockets with uniquely colored nose cones ...

[bernomatic]

I've never seen crazing in primer coats? Did you have incredibly bad humidity that day? The few times I've had crazing is when I've used different brands of paint and had bad reactions between the two. The only other thought might be some kind of contamination, possibly even transferred by your bare hands to the patched area? I've been buying the super thin nitrile gloves to wear while painting. Keeps paint off the hands obviously, but also keeps any skin oils off the areas where painting will be done.

No, it didn't rain last weekend and the humidity was within reason (In other words, I really don't recall, but it wasn't notable). I use to keep records on all that stuff when painting, I got lazy though and should start again.

I haven't seen primer crazing previously before either. However I haven't sprayed primer over finish coats often enough to get a good statistical probability either. Contamination was my first thought also, especially seeing as this rcket had been flown previously and exposed to lord knows what in the skies over Cleveland . I'm just fortunate that it happened prior to the RNC convention, otherwise someone somewere would have found a way to blame it on Trump.

Anyways, going with the contamination theory, the crazing appeared on the old painted portion only, I stopped after I noticed it appearing, so whether or not it would have spread, as my experience with crazing has shown it to do, with additional painting is unknown. I can't recall exactly, but it seems to me that this Bertha was also a part of a test program for a generic "Future" product. (or should I say a generic Pledge, with a "Future" shine? ). If so, I didn't strip it before working on the update/repair. Also the BTW the generic product did not live up to expectations.

So in conclusion, while we can't be sure exactly what caused the crazing to begin, we know what ended it with minimal work. That in and of itself was a revelation worth the whole update process.

[bernomatic]

Well, I uncovered another issue, One which I am not going to correct if it is discovered something is different, but has left me wondering.

As previously stated, the body tube is now close to the standard length of 45.7 cm (measured 45.6 cm), but, the overall length of a Big Bertha as shown in the catalog I received (copyright 2012) states the overall length (including nose cone and trailing fin length) is 61.0 cm. My Big Bertha measures 59.1 cm long. almost 2 cm short still.

I am fairly certain it is not the nose cone, as that is/was a standard cone and the one I used was from an Estes rocket designer package.

So that only leaves the fins. Now I could have placed the fins in the wrong place, but a quick glance at the picture shows that not to be the case, since being almost a full 2 cm forward of the aft end of the body tube would be really, really noticeable.

So now we are left with only two possibilities:
1) I screwed up the sizing of the fin (hey I did mess up the body tube length)
2) Estes misreported the overall length, or has changed the fin size .

As to number one, I used a fin template I traced from a Big Bertha I built in the early part of the century (damn that feels strange to say that), say about 2002 or so. It was the black "Beta Series" version.

So, without starting the type of anal retentive fin discussion seen on that other forum, does anyone have any idea why I'm still missing 2 cm?

[bernomatic]

I think this will be the final post for this thread. I gave the Bertha a couple of final clear coats of Rustoleum. Some micro-wrinkles appeared at the seams of the tubing, not at the overlap of the paints. This would tend to make me think that it was something (the filler maybe?) reacting with the chemicals of the Rustoleum. If we look at the earlier pictures, the crazing we see there is also near these seems.

The wrinkles this time are so tiny, that I'm just going to ignore them. It is not as if this Bertha is in pristine condition.

[Trident]

You cannot end this thread yet. The obligatory final picture of the Bertha rehab is required. Actually, a flight picture would be better. Otherwise, I'll just keep this thread alive all by myself. It'll get pretty tedious, so please comply ...

[bernomatic]

Just got back from a night out with mom of all rockets. We took in an Cleveland Indian's game (they lost), and the fireworks after the game. Then went to a bar (re: bar) my daytime bosses have opened in a storefront of the building I work in, to watch the end of the Cavs game (they won). So I'm getting home kinda late and a tad inebriated, but the whole point of this post was to say that I was hoping to launch a few over this weekend including the Bertha, so we can put this thread ( and Trident) to rest.

[bernomatic]

Well, good news and not so good news.

Flew the Big Bertha on Sunday. You can see the full flight report (sans pics and video which haven't been uploaded yet). The short story, she went up and came down a little too quickly. I think most of the problem was windcocking with a lot of parachute mis-attachment added in. She plunged into the ground crimping a portion of the body tube.

So here are some pictures.

The new full length Bug Bertha post flight... Still looking sexy.


The damage from the prang.


At the left, on the seam from the tube attachment, you can you just make out the tiny wrinkles I was talking about after spraying the gloss coat.

BTW, just in case anyone was wondering, the booze in plain view behind the rocket is the cheap stuff I have set out as a decoy for the young gentlemen of the house who have acquired very particular tastes and wouldn't dare touching "well" booze. Meanwhile dad's good stuff is being welll cared for and for some reason isn't evaporating as fast as it did a while ago.