Crack filling

[Superduner]

I'd like a bit of advice about filling cracks in the top of a gate which is open to the intense UV rays in southern France.
It's one of a pair and the other one is fine after 7 years but this one is severely cracked (cracked may not be exactly the right word here).
I've tried filling with all sorts of stuff. Hot glue, epoxy wood, water based wood filler but nothing stays around for more than a few months. It either squeezes out when the cracks close up a bit or falls out when the cracks open up in wetter weather.
It's there a product that will work in this situation?

 

[Tris]

The first thing that sprang to mind was whether polyethylene glycol or a wood hardener would stabilise this enough to let you refill the cracks with a conventional exterior filler. Other than that whether there is a pourable UV stable resin that would bond well enough.

Really just thoughts as a jumping off point than anything helpful I'm afraid

 

[johnnyb]

No I'd suggest epoxy impregnation then epoxy filler such as repaircare(its a Belgium product I think) be warned it breaks down under uv so something to filter this needs to go on top(osmo uv?sikkens)

 

[Cabinetman]

You are obviously keen about the appearance but personally I think it’s a losing battle. Probably time for a new top rail. What sort of construction is the gate?

 

[Chubber]

Rake it out and try this....

Big Boy Plastic Flexi Filler 250ml​

by Big Boy Product Code: 31685

From Tool Station. Inexpensive and 'elastic'

 

[Superduner]

Thanks for the helpful comments so far.
I'm going to try a combination. First some Ronseal wood hardener after raking out the cracks, then some Big Boy Flexi.
It's not available here, so the big river UK is sending some out - not quite so cheap!
It'll take a week or so to get here, but I'll report back when I've tried it.