Building & Fitting RV-6A Tanks

Infopipe · #1 06-20-2014, 12:46 PM

I have two questions:

1. I've been given plans of wing build from previous owner, but Figure 11A seems to be missing. Can a facsimile of that one figure be acquired. I've ordered complete Wing Build Set, but it won't be around until next week.

2. I'm building new Fuel tanks. I'm assuming that I will have to build on a jig (similar to a wing in a jig), and fit to the current wings (on the plane). Does anyone have any tips as to how the new holes in the wing can be accurately positioned and drilled. The plane is a non-pre-punched kit.

Thanks in advance.

Mike S · #2 06-20-2014, 12:54 PM

Quote:

Originally Posted by Infopipe

Does anyone have any tips as to how the new holes in the wing can be accurately positioned and drilled.

Darrell, you need a strap duplicator.

https://www.youtube.com/watch?v=DLpXnykw5dA

Any aircraft tool supply house should have them.

And, if the original holes were equally spaced, you could also make use of a rivet fan.

http://www.eaavideo.org/video.aspx?v=1543236758

https://www.youtube.com/watch?v=WMcW9qFOfiE

az_gila · #3 06-20-2014, 01:33 PM

It is the #8 dimpled mounting holes that will need to be located on the new fuel tank. The stiff skin and tight fit might make the use of a strap duplicator difficult.

I would use the other option that many non-pre-punched builders used, a stiff sheet of drafting Mylar.

Get the tank made and fitted in place with none of the mounting holes drilled. Trim the tank skin aft edges for a nice fit against the rear wing skins. Then place the pre-marked Mylar template over the tank and drill through the Mylar into the skin. Only a small pilot hole is needed - it can be opened up to the #8 screw size and dimpled once the tank is removed from the wing.

I think this technique carefully applied will give you better accuracy than attempting to use a strap duplicator on an existing countersunk nut plate.

Infopipe · #4 06-20-2014, 01:39 PM

I think this method will work as the strap duplicator might not fit under the rear tank baffle which has a hole from skin into the rear wing spar.

The reason I'm looking for Figure 11a is to determine the fluting locations on the ribs that do not coincide with the rivet holes. I guess I could layout the rivet holes and then flute between them?

az_gila · #5 06-20-2014, 01:43 PM

I have it scanned, see your email and reply for an attachment.

Pat Falley · #6 06-20-2014, 02:55 PM

I had to replace my tanks due to slosh. I couldn't make a pattern or template that I thought would work, so here is what I came up with. It's basically measuring and marking each hole. It turned out to be easy and it worked well.

With the tanks off:
Mask the skin around perimeter of both the tank and the wing. The edge of the tape should run along the edge of the wingskin. The tape is to write on using a sharpie, it just needs to be one width of tape.
Use a precision angle and straight edge, draw a line to mark the location of each hole on the wing masking tape. The angle keeps the line square with the edge of the wing skin. It needs to be an accurate, straight line, it should project over to the center of the hole.
Using calipers, carefully measure the distance to the center of each hole to the wing skin edge. I threaded a screw into the nutplate to have something to measure against. Write the number next to the line.

Once all holes are measured and marked, slide on the tank. You you can now locate the center of each hole and mark it.
I drilled them with a #40 and used a small nail to verify the hole is over the nutplate center. You can move the hole a little if you need to as you updrill.

Accuracy was probably with .02 all around, it went together fine.

Hardest part was dimpling once the holes are drilled.

It took a weekend to get each tank on for good.

az_gila · #7 06-20-2014, 04:25 PM

The template secret is to get some drafting Mylar that is thick enough not to be floppy and has a matte finish on one side you can mark on.

Infopipe · #8 04-11-2016, 08:53 AM

I finished the tanks last fall and have been waiting for warmer weather. Now I'm going to install. I understand that I'll have strap the new tanks on for measuring (for trimming). I assume that the straps will have to go over the flaps. To do that I'll need some kind of jig to insure the flaps are not damaged.

My question:

Has anyone done the install this way and has anyone built a jig?

If you've built a jig, could you share with me the design?

Thanks!