Thorp Air Command - T18.net

Quit doing 45 degree pitch angle climb outs.

_________________
Bob Highley
N711SH
SN 835
KLAL

Do we need vented fuel caps?

Plans say no.

_________________
Bob Highley
N711SH
SN 835
KLAL

Interesting question, interesting answer. I may be paranoid, but the lack of a backup scares me. One juicy bug is all it would take to plug a 1/4 inch vent.

Perhaps a different question is in order -- who is flying with a vented fuel cap, and what does your tank vent look like...and do you get splash-back through the fuel cap?

_________________
Philip Mandel
N118BC
S/N 957
Beaverton OR

Go look at any certified airplane for an example of vent size and location. A Piper or Cessna would surely vent fuel in flight with a hole in the cap.

_________________
Bob Highley
N711SH
SN 835
KLAL

That should not be a vented cap ... if it is it's going to "dribble" fuel .. it has a hole in it. That being said .. both of the Thorps I regularly fly do tend to give off a fuel smell and or leak in certain conditions through the cap .. neither of those caps are vented, they just don't seal 100%.

_________________
Lee Walton
Houston, TX
N51863,N118LW
KEFD

https://www.kitplanes.com/time-to-vent/ has some good info. I always wondered why strutted Cessnas have the 90 degree forward-facing vent tube hiding just behind the strut. The aforementioned website reveals the secret:
"The fuel tank cap(s) have vents built into the body of the cap. In addition, there is a forward facing ram vent underneath the wing behind the strut. In this position it is protected from impact ice."
So THAT's the reason, keeps it safe from impact ice.
Pipers are described as follows:
"Many low-wing aircraft use a simple metal tube protruding from the lower wing surface. The bottom of the tube is cut at 45 facing into the airstream to provide positive pressure to the tanks. This type of fuel-tank vent is used on aircraft such as Beechcraft Bonanzas, Piper Cherokees and Arrows, and Mooneys."

_________________
Philip Mandel
N118BC
S/N 957
Beaverton OR

I have the forward facing 45 degree vent tube that comes out the bottom of the fuselage just behind the firewall. I, too, get some gas smell through my non-vented gas cap with a full tank on take-off.

_________________
Bob Highley
N711SH
SN 835
KLAL

My aircraft has a non-vented cap with a forward facing vent like Bob's, been flying like that for 49.5 years, no problems so far.

_________________
Bruce Finney
N18JF T-18C #262
Yelm, WA USA

Like most everyone's saying, you shouldn't have a vented cap - plug the vent hole. In reality, you cannot have too much pressure from the 1/4" vent tube. Bottom line - if the cap's not vented and fuel's escaping from it, it is not sealing as well as it should... period. I never had fuel leakage from my cap, that I could smell or otherwise.

_________________
John Evens
Arvada, Colorado
T-18 N71JE (sold)
Kitfox 7 SS N27JE

Every once in awhile I get a fuel smell from a full tank on T/O . I remove the cap and give the adjusting nut on the bottom of the cap a slight turn to slightly expand the Viton o-ring . Smell gone , unless your F/O had a big ass plate of burritos !

RB

You absolutely DO NOT want a vented cap. If it is vented, where does the vapor go? In the cockpit!! Ask me how I know. Vapors will go both ways, In and out (STS). Do not do that. You will not be happy.
As I said, your cap is not sealing properly. That needs to be fixed. Do not fly with fuel dripping on your PAX feet! That is a fire hazard.
Cubes

Great comments, thank you all. Looks like there is a non-vented fuel cap in my near future (ACS 10600) to replace the 10610 vented:

http://acsproducts.co/our-products/mach ... h-fuel-cap

Spruce has them for roughly 60 buck$.

Even so, I am concerned about the vent getting plugged. It happens. It's rare, but it happens. The following webpage discusses an incident involving the author's Baron:

https://www.planeandpilotmag.com/article/zen-fuel-vent/

Many certified aircraft have backups. Most SE Cessnas have the 90-degree vent facing forward below the left wing behind the strut while one or both of the fuel caps is vented. Of course, they are up above and therefore no fuel can spill out of the fuel cap into the cabin and no fumes, ditto.

One idea I have is to drill a small hole -- perhaps 1/16 of an inch -- in my vent line somewhere between the start of the bend and the bottom skin of the fuselage. A bug(s) can then block the 1/4 opening and kill the ram air, but at least some air can still get into the tank -- unless the aft side of the tube is in a low pressure area. This is something I am not qualified to determine.

I appreciate that folks without backups have never had an issue. Please consider what might happen if your vent tried to ingest a big ole' bumble bee or chunk of bird or if mud daubers mudded it up while you were set somewhere overnight. Thanks!

_________________
Philip Mandel
N118BC
S/N 957
Beaverton OR

In the ‘For what it’s worth’ category, 218TH has the 1/4 fuel vent, but has a screen on it with a piece swedged over it to secure the screen in place.

Take a look at my removable floorboard setup in the photo gallery. I have a forward facing tube near both R & L gear legs for redundancy of fuel venting. They’re tied together behind the firewall using a Tee behind rudder pedals. Connected by a short rubber hose, a single aluminum tube conveys venting up to the fuel tank. Best location is at top center of the tank, as per plans. Least affected by sloshing there in the center. Dynamic pressure runs into both external tubes equally. One could be blocked and it still works. But cap should not be vented or you’ll lose any pressure gained. I never get fumes in the cockpit.

Nevertheless, I like the smell of av gas. Admit some of you do too. Maybe you like the sound of turbines winding up also!

Les