Airspeed Error

Hi everyone, New guy here. Bought a very nicely built RV6 in September and now have the RV grin! One problem though, it does have a significant IAS error. About 10 knots fast at 170kts TAS both AS indicator and has a RMI indicator showing the same error. I did have a static leak inside the plane, fixed that, thought that would be it but only dropped about 3kts. Static is at the pitot-static tube mounted at the typical place under the left wing and extends down the same amount as a fiends RV4 that does give known good indication. I checked the static ports around the pitot, all clear. Thinking this thing might not like the static taken under the wing?

Hi and welcome to Van's Air Force! I have a Piper pitot mast on my RV-6 (that was the cheapest option for a heated pitot at the time) and the static source never worked right. I finally installed the plans-specified static ports and my airspeed is within 1% now.

I added dams in front of static ports

I had the same problem when I first started flying my Lancair 235. On my first landing, I floated a full 4,000'! To solve the problem, I added little "dams" in front of the static ports (I have one on each side). Now, from flying wind triangles at various speeds, my ASI appears to be right on between 80 KIAS and 140 KIAS. YMMV.

Common problem whereby I have never heard of a location that worked as well as following the plans and putting them on the side in the location specified. Also, as silly as folks sometimes think the pop rivet (as per plans) isn't "robust or professional enough" it works very well. The shape of the pop rivet head is part of the recipe. There have been lots of
problems reported when deviating from the plans here, especially location.

Thanks for the help everyone. Next annual I'll try it at Vans location and the pop rivet. See how that goes. It's close at low speeds so it can wait a couple months.