Fuel Caps - Any better?

TimO · #1 06-26-2016, 04:59 PM

I'm thinking I may need to get some better fuel caps than the ones that came with the RV-14 Kit. Does anyone know if they're standard enough that I can buy a set elsewhere? I tried my spare RV-10 caps in them but they are smaller than the RV-14 fuel caps.

The reasons are twofold:

1) a couple times now when I've been fueling, I set the caps on the wing walk area, and the wind has blown them off the plane and back by the tail on the ground. They're just so light, which is sometimes a good thing, but in this case, if it's happened twice already in just over a week, it's going to be a long-term pain.

2) Today when I was doing a few rolls near my house (I live in a barren area), the kid and wife looked up and texted me that I was leaking fuel from both wings. I decided to look sideways on the next roll and sure enough, both fuel caps were just pouring out a fan of fuel while I was upside down. And, I wasn't at all negative when it happened (although the tanks were prob. at least 3/4 full).

Maybe I can change out the seals to larger o-rings or something and fix #2, but considering I'm not already that keen on these plastic fuel caps, if there is a source for good aluminum ones that fit, I'll probably just have some engraved ones made and replace these and keep it as a spare. Being light plastic, it would be a nice spare for a trip to Alaska or something...

BobTurner · #2 06-26-2016, 05:10 PM

If you're pulling positive g don't the tanks think that they're right side up? And enough of a leak to be seen from the ground? Something sounds very wrong.

woodmanrog · #3 06-26-2016, 05:25 PM

Tim,
Which caps do you have? We have the locking type and they seem very substantial albeit a bit costly.

rvbuilder2002 · #4 06-26-2016, 06:04 PM

An airplane owner wanting some of his parts to be heavier... so the wind wont blow them away? That is far from typical, but hey, to each his own.

As far as the caps sealing goes.... the seals are adjustable, though I haven't had to adjust any as received from the manufacturer.

rleffler · #5 06-26-2016, 06:56 PM

Does the RV-14 use the same caps as the RV-10?

I've ordered multiple caps from Vans and found that I had to adjust each one for proper fit. I really don't like the Usher caps.

Between me leaving them someplace and the tab breaking, they been a PITA.

I recently switched to Andair locking caps on my RV-10. I really like them. You can't take the key out when unlocked, which means the odds of setting it someplace and forgetting them is slim. Especially if the cap key is one the same ring as the ignition key.

They do reduce the size of the opening, which makes it a little more difficult to fuel. I'm managed to relearn the fueling process, but it isn't a big deal. They are also a bit constrained and you have to deal with the usual Andair ordering process. I ended up purchasing from Aircraft Specialties. Steve was a great help in getting them expedited. Plus he engraved them too.

Naturally, I haven't tested flying upside down in my RV-10.

See you and the family in a few weeks!

bob

TimO · #6 06-27-2016, 11:41 AM

Here are the replies to the queries so far:

Bob T: Yes, it was still positive G's, but the tanks were pretty full yet. And yes, I was about 1800-2000 AGL when they could see it. They saw the fuel spray coming out of the tanks and let me know. So I did another roll looking out the side window (that gets you dizzy quick

) and saw it for myself. They actually said "it looked like it was quite a bit of fuel". I don't think the actual volume is all that much though...it just fans out so much it's very noticeable. By the back of the wing the fan of fuel was probably at least 10-12" wide. I'm guessing with the roll, there is a little bit of centrifugal force that the fuel maybe slightly moves outwards. I'm guessing with much more empty tanks I wouldn't see this. But, I must say I've been seeing a bit of blue fuel staining on my flaps lately and now I know where it came from. The -14 BTW is very nice with rolls. Split-S's were fun too.

woodmanrog, I have the standard RV-14 caps. I don't know what they would be called exactly. They're a mostly plastic cap, that has 2 sections that rotate and lock in. They aren't the expand-to-seal type that the RV-10 used.

The other thing that I don't like about them is the fact that the stock color is kind of ugly. It's somewhat of a yellowish tan color. So this means that you really are forced to paint them. We had a fly-in this weekend and an RV-9 guy came by and wondered why I painted my caps...he said "I tried painting mine at first but they chipped all up like yours are starting to." Well, yeah, mine already have a couple of paint chips in them, especially since they blew off the wing. I painted my RV-10 caps and they chipped up too, but eventually I got some nice engraved ones that have the fuel type and my N-Number on them, and those I left raw aluminum.

Scott, yeah I'd gladly get some heavier caps if I could get aluminum, leave them unpainted and get them engraved. If you have any manufacturer info that you can send me offline or in a PM, I can check with them to see if they offer an aluminum variant. If so I'll go that route. The caps are nice otherwise, and the locking method is convenient. They open nicer than the expand-to-seal types. I also like the pretty anodized neck rings they came with...but I'm hoping for a different material option.

If they don't make them in an aluminum variant, I'll check into having a production run of some top-halves in aluminum. At least maybe that way people could retrofit an aluminum top onto their caps and get them engraved.

Bob L,
No, these aren't like the RV-10 at all. I actually would prefer non-locking caps. I don't need the extra inconvenience of the key or anything, but, if Andair makes one that will fit the -14, I'd consider it. I'll maybe bring some
tape to seal off the open tank at OSH and bring my fuel cap to their booth.
At least we're only a few weeks away now!

I'll try to remember to take some pics and post them so that people can see what they're like.

EDIT: Here is a link to the page on Vans site for the caps we get with the RV-14. They're the T-00007 type.
http://vansaircraft.com/cgi-bin/stor...duct=delux-cap

Also, if you go to the retrofit locking type cap page, it says specifically that they can't be used on the T-00007 flanges used in the RV-14 wings.

http://vansaircraft.com/cgi-bin/stor...duct=retro-cap

So if you build per-plans, you will lessen your options on what fuel caps you can use. But, if you don't go per plans, I don't know if there is any guarantee that the other cap flanges will fit. The RV-14 being all pre-punched, fits the T-00007 flanges. So we're probably going to have to figure out a different solution than most other RV's are using. Ideally, we can talk to the manufacturer and see if they'll make aluminum top halves. If not, I'll have to see how complex they are and maybe make some up like with the axle extensions on the RV-10. If I do it, it'll be a one-time group buy type situation. If I can get the seals to stop leaking though, there will be a limit to how hard I'll try to get aluminum tops. I'd really prefer them, but first I just want them to seal.

rvbuilder2002 · #7 06-27-2016, 04:14 PM

I believe the RV-14 fuel caps are made by this company.

http://www.newtonsprl.co.uk/

I don't know if they have any other versions of the cap available.

czechsix · #8 06-27-2016, 04:22 PM

Tim, have you tried tightening your caps? I recently did the leak test on my tanks and initially the caps leaked so badly I couldn't even pump the manometer up to 0.5 psi...it was leaking out faster than I could pump it in. I tightened them up a bit and afterward they were almost leak-free. One of them still leaked very slowly so I used a piece of vinyl tape to complete the pressure test, but the point is, there's no way you should be venting any visible amount of fuel overboard in flight. If they fit that loosely you're also going to get water in the tanks the first time you park it outside in the rain.

The tightening process works a bit differently from the aluminum caps Vans used prior to the -14. On the aluminum caps where the rubber o-ring is being compressed between the top and bottom halves, there's a fine line between getting it tight enough to seal vs. so tight that you break the roll pin trying to close it. The caps on the -14 are designed such that the lower half of the cap must be inserted into filler neck in a specific orientation, then rotated 90 deg clockwise (using the open tab on top of the cap), and when the tab is closed the lower half is being pulled up against the bottom of the neck flange. To tighten the cap you simply turn the nut until you can no longer rotate the locking tab clockwise after inserting it into the filler neck. Then back it off just slightly so you can rotate the tab clockwise and then fold the tab down. If that's not tight enough then there's something else going wrong that you can't fix by tightening.

Overall I think the design of the -14 fuel cap is an improvement over the previous models, but it is plastic and may not be as robust in the long run. We'll see. If you decide to paint them, you might want to get some primer made for plastics. All the major paint shops carry it because cars have plastic bumpers, and primers designed for metal surfaces don't adhere well to plastic. I used the car bumper primer one time on an R/C model helicopter body and it held up very well including several crashes...

TimO · #9 06-29-2016, 11:15 AM

No, I haven't tried to tighten mine yet. I'll have to do that. I'll lube and tighten them and see if that seals them up. You're absolutely right about the water. Every year at Osh I get dumped on and you definitely pick up water from leaky cap o-rings.

The plastic paint is a good idea as well. Sadly, if you do that, you'll probably have to paint them some other color than your base paint, because finding plastic paint to match may be tough. A contrasting color may be better.

Attached you can see pics of my fuel caps, and the mechanism that is being described. I agree that in general the fuel caps are a better design (as long as these can be sealed tight). I just think the material chosen is a poor choice.
I'd prefer a nice aluminum cap, and then engrave them. It does appear that these are engraveable. It looks like Aircraft Specialty does them:
http://www.aircraftspecialty.com/engraving.html

These are the SPRL caps. I'll have to see what info I can find on them. I'm not going to stop and tear mine apart right now, but if I could have a new top machined I'd do it. For the time being, I may have to buy new caps if I can't strip off my paint. Below are the pictures of my caps. I would recommend NOT painting them if you're using these caps....at least not unless you have a better paint to use for the job. Remember, mine has been flying less than 2 weeks and if they look like this now they're going to be downright ugly in a year or two.

Edit: Now that I've googled "SPRL Fuel Cap" I see you can buy these in a locking version for people that want that. Hopefully I can track down the actual manufacturer and inquire about an aluminum top.

Carl Froehlich · #10 06-29-2016, 11:34 AM

I help with a set of RV-14 tanks and agree, the caps are not good. While Van's must have had a reason to use these, they just have a cheap feel to them.

I suspect however that the pre-punched hole in the tank skin is too large to install the standard Van's aluminum flange and cap - but if I was building an RV-14 I'd try real hard to find a way to use the standard flange and cap.

Carl