How to enlarge a large hole?

I ordered the RV-14 fuel tank caps for my RV8. The rivet holes align and it sits flush on the skin, but I need to open the hole for the cap ~.2 inches.

The current hole is ~2.34 inches and the final hole needs to be ~2.54 inches.

Is there a recommended technique to accomplish this?

My initial thought is to cleco a plate over the top of the current hole, find the center, then use a hole cutter to cut to the final size.

Cut out a piece of plywood with correct size hole and clamp to part. Use router or zip cutter to cut hole with plywood as guide.

If you are skilled with a file, you can scribe the line and file to it. A craftsman can do it so well it will look machined.

Hole

Drum sander on a hand drill . If you own a Cleveland tool edge roller that will put a nice finishing touch to that area also .
Tom

Dremel with small drum sander head.

Making it round in the right place

Use a square to draw perpendicular lines tangent to the existing hole. A straight edge from corner to corner (tape thread) will give you the center of the hole.

Use a compass to draw your correct diameter circle and center it. Trace the new circle.

OR

Use a compass to draw two circles (old and new diameter). Center the old circle on the hole. Tape the paper template in place. Cut out the old hole. enlarge the edges to the new hole. Should give you a nice round hole if you use a sanding wheel, file, or edge dresser.

Don

-14 gas caps on an -8

Great thread!
I just got my -8 wing kit last week and ordered -14 gas caps with it as well.
Glad to hear that the tank skins already have the rivet holes in them, and even better that they line up with the -14 caps.

I've been contemplating how to get this hole enlargement thing to happen.
So far the best idea I've heard in my local circle of knowledge is to cut a fresh piece of plywood big enough to cover the cap hole.
Clamp it down flat to the tank skin.
Then find the center of the cap hole and and mark it on the plywood.
Drill through the skin and plywood with a hole saw type cutter using the plywood to guide your pilot drill at the center of the hole.
Hope that makes sense.
Looking forward to hearing all the other ideas here as well. I'm not even going to open my box until fall except for a quick inventory, then close it back up. That's the deal with my wife. "winter project" One sub kit per winter. Did the tail kit last winter.
Good luck, and thanks for the great question.
Tom

Before going down the hole saw route - do it on a scrap piece first - you may not like the edge and accuracy of the hole saw you are using ... When I have enlarged large holes I have found that a new sharp scribed circle - with a 1/4 to 1/2 size sanding drum was the best way to get a perfect hole .. just sanding out to the scribe line ... perfect hole. It is harder to get a nice hole if the file has a small radius in comparison to the finished hole radius ...

why the -14 cap?

I have tried to follow the various links and have read as much as I can find on it - but can someone tell me what the advantage is to going to the "new" -14 cap on the RV-8 tank? I am at the tank building stage and I ordered the deluxe caps (for the -8) when I ordered my wings...it's not too late for me to change to the -14 caps at this stage in the build, but I don't see any discussion on the pros/cons, just whether or not they will fit the -8 or how to drill out the hole??

Thanks for the help...

izzybear said:

I have tried to follow the various links and have read as much as I can find on it - but can someone tell me what the advantage is to going to the "new" -14 cap on the RV-8 tank? I am at the tank building stage and I ordered the deluxe caps (for the -8) when I ordered my wings...it's not too late for me to change to the -14 caps at this stage in the build, but I don't see any discussion on the pros/cons, just whether or not they will fit the -8 or how to drill out the hole??

Thanks for the help...

Click to expand...

I purchased my wing kit from someone else and it had the standard fuel caps. I have very little real world experience with them beyond them being very cumbersome to open. I have read about and have seen that the standard caps are prone to leaking.

Those two factors together prompted me to order new caps. I didn't want Locking(or I would have gone with the newtons) and the T-00007's are much easier to open than the standard. While not part of my decision they are much lighter as well.

izzybear said:

I have tried to follow the various links and have read as much as I can find on it - but can someone tell me what the advantage is to going to the "new" -14 cap on the RV-8 tank? I am at the tank building stage and I ordered the deluxe caps (for the -8) when I ordered my wings...it's not too late for me to change to the -14 caps at this stage in the build, but I don't see any discussion on the pros/cons, just whether or not they will fit the -8 or how to drill out the hole??

Thanks for the help...

Click to expand...

Yeah Jim, It's just a preference thing. When I was visiting Van's I asked about the deluxe caps which are very nice, but when the guy giving me the pseudo tour held up the -14 caps........well, they were even twice again as nice. They're lighter, look cooler, operate very smoothly, and even have a bigger opening so you can look in past the filler nozzle a little better and see when the gas level is almost to the top before you have a gas geyser on top of your wings. I would for sure upgrade from standard, but the -14.....until I build my tanks and install/modify my -14 caps, I may be wronging you to make that recommendation.
I will be paying close attention for whoever goes before me to see how they do it.
Tom

Thanks

Thanks for the additional info Aaron and Tom... Looks like the -14 cap is an improvement on the deluxe fuel caps if they are now a little larger and lighter!

That was easier than I thought

Taking the approach that JanRV6UK recommended I found a 2 inch drum sander that I could chuck into my drill from Harbor Freight for 8$(actually a whole set).

I place the fuel cap flange on the skin in the proper orientation and then using a fine tip sharpie marked the skin where the flange meets the skin. This left me with a nice blue circle in the right place. I used the sanding drum to remove to the line.


That wasn't enough, I had to take the line away completely to get the cap to go on and off without interference.





Thanks all for the help!

I'm glad Aaron posted these pictures... The caps are Newton SPRL's, standard on the Glasair Sportsman (which uses 4 of them). Not sure if Aircraft Spruce is stocking it yet, but you can buy a re-seal kit for these caps as well, making them a good long-term decision.

RV-14 Caps on my -8

Well it's been nearly a year since I was first introduced to these (then) new gas caps for the RV-14 at Van's.
Last week I finally got to the point in my project to modify my tank skins and get them to fit in.

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I haven't heard a better idea for enlarging the hole than what has already been discussed here, so I decided to proceed.
As stated by Aaron before, the rivet holes line up perfectly to the tank skins.

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From the inside side of the skin it is easy to reach in between the cap flange and the skin with a sharpie and draw the new radius needed for the cap to fit through the skin.
The 2" sanding drum made quick work of this.

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Once ready to sand, it nearly took me 20 seconds to go from here:

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To here:

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Getting pretty close to the line with the rough cut (or rough sand in this case). I then just kept going with the sanding drum with much less pressure for the fine tuning before going to the 220 sand paper by hand followed by the 400 as soon as the cap would pass through the hole.

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When I take the tanks apart for the final deburring / dimpling, I will clean up the hole one last time and be good to go.
After all the research and decision making on this mod, I think I will like it most do to the larger hole opening. As far as looks or anything else, I do like the machined clean look of the aluminum deluxe caps better than plastic. Once painted though it shouldn't make any difference in appearance.

Thanks for making and posting the first go of this Aaron. Hope your recovery is going well.

Tom

I printed up a template, clecoed it to the existing holes, and traced around it. Used a nibbler and a sanding drum, and a file for the final fit. Just make sure you have the flange oriented right before you start filing it down to fit the curve of the skin, or you'll have to order a new one