Pilot in an experimental tailwheel aircraft reported a runway excursion after landing in a quartering tailwind. Right main gear and propeller were damaged with no injuries to pilot.

Narrative

I was on a VFR flight to ZZZ from ZZZ1. The winds were reported as variable at 5 mph. After contacting the tower; I was told to report left mid downwind for XX; which I did. Then the tower asked me to extend my downwind and he would call my base. The downwind was extended a mile or more and I ended with at least a two mile final. The windsock was hard to see until I got close to the runway since it was halfway down the runway and not near the end of the runway. The wind appeared to be a left crosswind. I did a normal three point landing and as I was slowing down I was have difficulty controlling the aircraft and the left wing raised up and initiated a ground loop and I was not able to stop the rotation. I tried adding power to correct the movement but that aggravated the situation and I ended up off the runway and broke the right landing gear off and resulted in a prop strike. Once I got out of the plane I looked at the wind sock and noticed it was a quartering tailwind. I did not have enough rudder authority at that slower speed to correct the situation and I let the left wing get too high. Once in the grass the gear failed and the prop struck the ground sending pieces flying. I was not injured in the incident. The long straight in approach at an unfamiliar airport did not allow me to sufficiently assess the winds on the runway and I reacted too slowly once the ground loop started.