Fuel caps

[Zk Boy]

Well only about a week to go on our 15 month rebuild (1957 18a 160). The help from this site has been fantastic even down to members kindly helping with forwarding parts to NZ.
One of my last questions is, can I run the cessna style fuel caps on the cub, there are no piper caps in NZ for sale.
The cessna caps fit well and I would do a flow test. I will order some new caps from univair but I don't think they will be here in time for the test flight and engine run in.

Is anyone running these caps? They are the same as the 172.

Thanks
Only days now!

 

[mvivion]

Are they vented? That's the biggest issue, since the Cub uses vented caps. If they're vented, they should work, HOWEVER, they would not be a "legal" substitute. I don't know about NZ, but NAPA Auto Parts stores in this country carry a variety of fuel caps, some of which are vented, and work just fine on a, er....uncertified airplane...or in an emergency. And, they're chrome plated!!

Atlee Dodge also sells PMA'd fuel caps.

MTV

 

[Zk Boy]

Thanks for that, yes they are vented caps, I have seen one on a 90 hp cub, so was just wondering?

 

[P.o.P]

Cessna caps are NOT vented.

There are those that have an "Emergency Vent" flapper valve that will open with negative pressure in the tank.

It is not vented otherwise.

HOWEVER; they are intended to be used with the "Normal" underwing Vent System to prevent fuel starvation

if the Vent Tube is blocked ONLY.


Using this cap just might shorten your first flight.

And NOT for a good reason.

 

[Zk Boy]

That was the reply I needed to stop me thank you. I think I can borrow some caps off another cub until my new ones arrive. Thanks again

 

[P.o.P]

Wow!

3 minutes for a reply.

You must be sitting on your laptop.

That is the great thing about this forum as years ago it might have taken weeks ; if you

got a reply at all.

Obviously someone might do the "Black & Decker Lobotomy STC" on them.

Good Luck!

 

[Bob Breeden]

NEVER AGAIN:
Fuel starvation from non-vented caps on a Super Cub - sent from a vendor as replacements sold as VENTED CAPs, but not drilled yet. This was one experience only in which I was flying patterns familiarizing a friend who was in the front seat of a Cub. There was a GRADUAL increase in stumbling on full power application, but fuel still flows and power is still made at reduced power, cruise settings. This gradually worsens over 10 -15 minutes - until she coughs bad on takeoff, leading to an abort into a farm field. Switch tanks? Carb Heat? Mags? What was it? Not noticed until it was obvious that the fuel caps had been sucked down below the level of the tank cover as the tank collapsed....one quick turn on the fuel cap and the tank hissed and popped back up into shape...

 

[P.o.P]

That is exactly what would happen with a Cessna with a blocked vent TUBE.

The so-called "Vented Caps" open a red rubber flapper when this occurs to provide a vent.

You still get a "hiss" at the cap though when that happens.

My guess is that they reduce fuel flow somewhat.

Still easier than changing the fuel sysrtem though.

 

[cgoldy]

I have the caps with the forward facing vent tube. I accidently put one on backwards during my flight testing phase. My stupidity never fails to amaze me! At full power and high angle of attack (low alt over water as well) she shut down as it had created a vacuum. Put the nose down and Switched tanks very very quickly and away she went again. Fuel cap check is now firmly on my preflight list.

 

[cubdriver2]

ZK, find a Harley shop, the older bikes had vented caps and fit on a Cub tank, I would still order the right caps but the Harley ones will get you going, WARNING, WARNING, WARNING, anytime you do anything with your fuel plumbing or venting do a flow test, even if it's certified parts do a flow test of at least 5 gals.

Glenn

 

[bob turner]

That little forward venting tube is the secret for good flow. I know the S/C doesn't require them until you hit 180 HP, but it is still a good idea. I would bet a nice Harley cap and a soldered in copper tube would do just fine, but make sure the other vent system is disabled - or just get the non-vented cap and solder the tube in that. Only on the airplanes that MTV suggests - certificated aircraft require the hundred dollar caps.