Vents
David,
I'm not sure what part of the system you are needing. The fresh air systems for the -7 kits I have seen are a pretty much hold-your-hand affair. The NACA vent holes are punched at the factory. The placement of the outlet vents is on Drawing 24. In between is just tubing, either 2" SCAT tubing or tubing of your choice.
If your kit doesn't have the cutout for the NACA vent, or you didn't get SV-1s with your kit, order them from Vans. It is the plastic part of the NACA vent. It will come with directions and a cutout template. It has a 2" outlet to attach to any vent tubing. Just make sure the long axis of the vent is parallel to the chord (longeron) of the airplane. Also make sure your vent is high enough to clear any workings or positioning of the rudder pedals. I don't think the position of the NACA vent is that exacting but I believe Van's did work to show that the prepunched location on the -7 skins works well. Also there are a number of -7 builder websites with lots of details and great pictures of how they did it.
The 6 kits don't have any provision for air vents so I patched it together. I got the SV-1 and installed it like the 7s. I also got the SV-3 tubing that Van's sells. I was a bit disappointed because it looks like regular ol' automobile ducting and I am not sure it is any lighter than SCAT tubing. But it will work.
The reason the SV-5s didn't work for some people is that it is made from plastic, probably ABS. The valve plates that stop the airflow aren't machined so they don't match up completely to the inside of the vent. Some people are successful in adding adhesive to make the valves seal. Other people don't like the cheesy plastic look. The builder who gave me a set of SV-5s couldn't make them work and I spent a couple of days in frustration also. I almost threw them away but I think I can take them apart and, with some ingenuity on my lathe, can make them seal.
Some builders don't care about a little air leak but in your location, I think you will want a good seal in the wintertime. If you haven't got your aftermarket outlet vents yet, the best ones I've seen are from Stein Air. I believe they are a full 2''diam not 1.625" like Vans, but also more expensive.
The best thing about the Van's system is it is light weight. On the -6s every ounce counts. Good luck.
Dave A.
6A
