Kahuna
Moderatoring
I was asked in another thread about my recent wing replace and fuel tanks. After 1200 hours on the Super 8, it was time for an upgrade.
Howd I get 97 gallons in my RV-8 wings?
You might recall that my original 8 wings had 2 30 gallon wing tanks plus a 13 gallon smoke tank located on the left wing in the wing walk area. These fuel tanks were just extended 2 bays each main tanks. Building these was pretty straight forward, but a pain. Add 2 bays, order extra skin, z-brackets, and so forth.
In wing smoke tank is very convenient for keeping the junk outta my plane. Smoke oil guys dont always keep it in the tank when filling. Further, I want ALL my baggage. I dont want any tanks in my baggage. I want the space for travel.
I have had plans where I wanted more fuel. Lots more fuel. 60 was not enough. Time for more. My good friend Pat Tuckey, aka ;Glider', had done some work in this department. Go here for his very considered response.
I liked his ideas, with a few exceptions. I did not like using the existing outboard skin and making it a permanent deal rivetted to the spar. Mine will surely leak on the first day and require me to remove the tank. ALso in Gliders testing, he had no need for the transfer pump. So. on I went with those items in mind.
I decided that I would build 4 standard vans tanks. Simple, easy repair, easy parts. If I whack a deer, I build another standard tank. But how to get around the pesky pre-drilled holes in the spar for the outboard forward LE skin?
I did it this way. Build the tanks. Set the outboard tanks up on the wing spar. ALign the outboard tank with the outboard skin. Use the holes in the tank skin as guides for drilling into the spar. Let the holes fall where they may. Its essentially what I did on my first set of wings for the 2 outboard bays. This will leave a nice ~4" gap between the tanks for plumbing. Only the inboard tanks have indicators. This makes fuel flow accuracy more important than before.
Z-brackets. I used 2 sided tape. Let the Z-brackets fall where they may. Put zbrackets on rear baffle with solid rivets not bucked. Tape rivets in place. Your just trying to get the zbracket to stay in place. Put 2 sided tape on zbracket side facing spar. Set tank in correct place. Push down so the 2 sided tape hold zbracket in place. Remove tank and brackets are in the permanent place you want them. Drill into spar web and your alignment is good to go.
Plumbing. In my installation, the engine only gets fuel from the inboard tanks. Further, the inboard tanks only vent to the outboard tanks. If there is fuel in the outboard tanks, it will get pulled into the inboard. Only the outboard tank is vented to the outside air. Testing has proved this to work fine. My outboard tank vent, vents at the fuse in the normal vans location. Note: Since a very sealed tank is now mission critical to the success of this senerio, the Vans usher caps are junk and had to go. I went with some double sealed locking caps from ACS. I must have caps that will NOT leak or I wont get the fuel pulled into the mains.
While I was building new wings, I went ahead and went with single piece top skins. Just cause.
But wait. 4 RV-8 tanks are only 84 gallons. Where is the other 13? Well I went ahead and built the same in wing smoke tank as before. Only this time I plumbed it so in case I ever need it to double as a fuel tank, its ready to go.
You dont get no pictures cause I didnt take any. Its just 4 tanks on the leading edge of the wing.
Did the wings slide into the fuse and the bolts line up? Like butter. When I lined up the plane to drill the rear spar, it required no wing movement/adjustment at all. Both sides perfect. Drill hole, done. A testement to the repeatability of the pre-punched Vans products.
Howd I get 97 gallons in my RV-8 wings?
You might recall that my original 8 wings had 2 30 gallon wing tanks plus a 13 gallon smoke tank located on the left wing in the wing walk area. These fuel tanks were just extended 2 bays each main tanks. Building these was pretty straight forward, but a pain. Add 2 bays, order extra skin, z-brackets, and so forth.
In wing smoke tank is very convenient for keeping the junk outta my plane. Smoke oil guys dont always keep it in the tank when filling. Further, I want ALL my baggage. I dont want any tanks in my baggage. I want the space for travel.
I have had plans where I wanted more fuel. Lots more fuel. 60 was not enough. Time for more. My good friend Pat Tuckey, aka ;Glider', had done some work in this department. Go here for his very considered response.
I liked his ideas, with a few exceptions. I did not like using the existing outboard skin and making it a permanent deal rivetted to the spar. Mine will surely leak on the first day and require me to remove the tank. ALso in Gliders testing, he had no need for the transfer pump. So. on I went with those items in mind.
I decided that I would build 4 standard vans tanks. Simple, easy repair, easy parts. If I whack a deer, I build another standard tank. But how to get around the pesky pre-drilled holes in the spar for the outboard forward LE skin?
I did it this way. Build the tanks. Set the outboard tanks up on the wing spar. ALign the outboard tank with the outboard skin. Use the holes in the tank skin as guides for drilling into the spar. Let the holes fall where they may. Its essentially what I did on my first set of wings for the 2 outboard bays. This will leave a nice ~4" gap between the tanks for plumbing. Only the inboard tanks have indicators. This makes fuel flow accuracy more important than before.
Z-brackets. I used 2 sided tape. Let the Z-brackets fall where they may. Put zbrackets on rear baffle with solid rivets not bucked. Tape rivets in place. Your just trying to get the zbracket to stay in place. Put 2 sided tape on zbracket side facing spar. Set tank in correct place. Push down so the 2 sided tape hold zbracket in place. Remove tank and brackets are in the permanent place you want them. Drill into spar web and your alignment is good to go.
Plumbing. In my installation, the engine only gets fuel from the inboard tanks. Further, the inboard tanks only vent to the outboard tanks. If there is fuel in the outboard tanks, it will get pulled into the inboard. Only the outboard tank is vented to the outside air. Testing has proved this to work fine. My outboard tank vent, vents at the fuse in the normal vans location. Note: Since a very sealed tank is now mission critical to the success of this senerio, the Vans usher caps are junk and had to go. I went with some double sealed locking caps from ACS. I must have caps that will NOT leak or I wont get the fuel pulled into the mains.
While I was building new wings, I went ahead and went with single piece top skins. Just cause.
But wait. 4 RV-8 tanks are only 84 gallons. Where is the other 13? Well I went ahead and built the same in wing smoke tank as before. Only this time I plumbed it so in case I ever need it to double as a fuel tank, its ready to go.
You dont get no pictures cause I didnt take any. Its just 4 tanks on the leading edge of the wing.
Did the wings slide into the fuse and the bolts line up? Like butter. When I lined up the plane to drill the rear spar, it required no wing movement/adjustment at all. Both sides perfect. Drill hole, done. A testement to the repeatability of the pre-punched Vans products.
Last edited:
