How to keep paint from cracking??

[Jim Mackell]

I'm going to be refinishing the side of a very old trolley car. There is a horizontal side panel that runs about 30 feet. It adjoins the main support beam for the full length. The two are very tightly joined. It's impossible to even insert a razor blade tip into the joint. But wood moves. And it flexes at different rates. And that's why the last paint job has developed cracking and therefore let in moisture and therefore starting bubbling. All right at the long horizontal joint. How can I paint the side of this trolley without developing cracking? Thanks for any ideas.

[Lex Boegen]

I would use painter's caulk to fill in the crack. Level and smooth it with a straightedge (such as an old credit card).

[Mike Hollingsworth]

Latex Paint and lots of coats.
It will stretch like a BandAid.
I gave up on oil base exterior long ago.

[Joe Chritz]

You probably won't.

A quality exterior acrylic is a good choice but it is still a possibility that cracks develop. Unfortunately it is the nature of the beast.

Don't fault a snake for being a snake and all that.

Joe

[johanes purnama]

The paint cannot help if the wood is moving.
A paint is just a thin layer. It wont be able to withstand the wood movement.
What you you can try is to finishing for all the wood surface, so there is no exposed surface. Hopefully by this way there is no wood movement since the wood pores and grain are already fully closed.
But it no guarantee that the wood would not move.
Cracking in the wood finishing
(http://www.wisnofurniturefinishing.com/2010/08/cracking-in-wood-furniture-finishing.html)

Good luck

Johanes