Fuel expansion and fuel odor

Ok, we're learning as we go with our "new to us" RV8. After recently flying it on a beautiful, cool morning, I topped it off and placed it back in the hangar. The next day, my son came out on a warm afternoon and was preflighting the airplane. He unlocked one of the fuel caps and fuel immediately gushed out of the tank. Obviously, heat had expanded the fuel. My question is, why didn't fuel go out the vent and relieve this pressure? Also, we've noticed an occasional fuel smell in the aircraft when it's been topped off and especially if you're doing some light acro. Is this just a natural result of a small amount of venting onto the forward belly? We did check both vents and they are open and the airplane flew for almost an hour after this gushing experience.

We continue to be amazed by the design and capabilities of this aircraft and the incredible craftsmanship of the builder.

Just a guess on the "gushing" out the cap. The high point in the vent line is above the tank filler neck. Pressurized fuel will flow out of the vent line, to a point. The pressure in the tank and fuel in the vent line will equalize at some point. Head pressure will keep positive pressure in the tank from the fuel sitting in the vent line. You released it when pulling the cap.
As long as your vent line is clear, I don't think you have an issue.

I would agree with your assumption for the slight smell of fuel venting when your tanks are full. I will get that on my 6 sometimes after filling. I run on off my left tank after filling (I sit on the left), but as soon as I safely can, I go to the right tank for just a few minutes, then back to the left, then manage accordingly. This seems to keep the occasional minor fume smell away.

Thanks! Pretty much what I thought but I value the RV community input.

My -8 with "Rocket" coil type vents will burp fuel after warming in the hangar...

If I'm going somewhere I fill it to the rim...

If I'm putting it in the hangar I leave it down 1/4"...

Too expensive to leave it on the hangar floor.

My -8 with "Rocket" coil type vents will burp fuel after warming in the hangar...

If I'm going somewhere I fill it to the rim...

If I'm putting it in the hangar I leave it down 1/4"...

Too expensive to leave it on the hangar floor.