Honest John Project

[Albanach]

Painting issue: What causes the paint crackling?

 

[cwbullet]

Painting issue: What causes the paint crackling?

Paint - primer incompatibility?

 

[OzHybrid]

Painting issue: What causes the paint crackling?

Multiple things. In short. The paint on the surface dries quicker than the paint below. As it dries it shrinks. It then pulls into islands that if they dry further can cause cracking. This can be due to draughts in the area you are painting. It can be made worse by incompatible base coats. So read the instructions for the paint system, check the temperature and humidity levels are the same for undercoat/ primer and top coat. Additionally thinning the top coat too much can make things worse.
There is generally an optimum time frame for laying down all the coats. If you get that right they all dry in the right order and don't pull at each other. , .
If you take too long, this will cause issues. If you are too quick you'll run the risk of runs and wrinkling. The inverted drying profile of crackling.... ish...

Without photos and a list of your paints, temperatures, and times, that's as much general help as you can get.

 

[Albanach]

Bad Primer choice. Had to use the power eraser to fix it. The primer was very solvent prone.

 

[Albanach]

Launched on Sunday at QC Rocket Club launch and used a J615 aerospike achieved 1500' @ 287 mph. Perfect launch to watch.

 

[augendoc]

In the photo, you have placed it centrally against a frame that is commonly used for making small fruit trees grow flat. The process is called espadrille. A bit like when you have someone in a photo with a tree in the middle of their head.

Training a tree to grow on a trellis or other support is called espalier. An espadrille is a casual shoe with a rope sole. But then again, my spellchecker once rewrote “Yosemite” to “Glasnost.” So “espadrille” is actually a pretty good guess.

 

[Hobie1dog]

Launched on Sunday at QC Rocket Club launch and used a J615 aerospike achieved 1500' @ 287 mph. Perfect launch to watch.

darn it, I wish you would have gotten video

 

[MarsLander]

Is there a rule of thumb for the fillet radius to rocket size?

Handbook of model rocketry-G. Harry Stein.

Measure your fin root and multiply by .04 and .08. Find something in the range that is close.

Fins look about 5-6"??? 5" at 4% is .2, 6" at 4% is .25. 8% would be .4 and .5. You could use anything you have that is 1/2" to 1" in diameter and be just fine. At that point aesthetics takes over. It also depends on the speeds, higher speeds, I'd use a larger fillet...