Posted Tuesday, April 21, 2009

Wing Tube Modification

One of my pet peeves (among several on this plane) is the fastener method used to secure the wing panels to the fuselage. Pilot holes drilled in the ends of the aluminum tube and pan head sheet metal screws to secure the wings to them and thus securing the wing/tube assembly through the fuse just didn't set well with me. After screwing those screws in and out enough, they are going to strip out. Then where are you?

Enter yet another use of my little brass inserts. The mod is simple and was pretty easy to accomplish. I used a pair of 6-32 inserts to facilitate use of 6-32 machine screws instead of the sheet metal ones. I drilled the existing holes out to 13/64 and continued through into the plugs which are inserted into the ends of the tube. Changing bits, I then used a 15/64 bit to enlarge only the aluminum portion of the hole. The insert was then threaded into the hole and sunk just below the surface of the tube to allow smooth fit into the wing. A couple drops of thin CA were applied to the inserts to ensure that they will NOT back out - ever.

Example of the wing tube with the typical pilot hole.

Tube drilled and fitted with 6-32 brass threaded insert.

Now the sheet metal screw has been replaced with a long-lived machine screw.

Fuel System, RNVA, Engine Installation

This was the last major component installation of the project. You may recall I wrote of the break-in that I performed a few weeks ago (already?) and since, the engine sat in the shop while I gallivanted about the country with no time to put into it. Well, with a few nights free after a cancelled biz trip and some more time on the other side of Easter, the engine, RNVA (remote needle valve assembly) and fuel system was fitted to the tight compartment forward of the firewall.

The tank was previously installed, then I noticed I set up the plumbing with the tank right side UP, not sideways as it would be installed in the plane. Five minutes later - fixed. I am always very careful and as I do more specialized fitting and tinkering with these things, I tend to plan drilling holes much more carefully than I used to. I hate extra holes. Positioning the spot for the RNVA and fueling port are next up.

The RNVA mounted to the firewall on a small hardwood block.

This is Dubro Products new EZ fueler. All plastic, gas or glow use. Check it out at their website.

The fueler was installed at the 9 o'clock position on the cowl directly behind the engine. The working space is tight. The trip from the tank to the carb is a short one.

RNVA and fueler valve now installed and plumbed in.

The engine was installed as the last step in the front-end work. Now you can see why I used a fueling port instead of pulling the fuel tubing off the carb.  There's just not space to access the tubing at the carb inlet.