ceengland(at)bellsouth.ne
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 Posted: Tue Apr 10, 2012 3:31 pm Post subject: Fuel Caps (Was: Gascolator (Was: Hoses and O-rings in RV-6 |
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Van's is a pretty conservative organization, as homebuilt companies go. The aren't likely to give any definitive advice when you stray off their carefully worn path. 
Suggest googling 'alcohol and gasoline resistant o-rings' or 'gasohol resistant o-rings'. Here's an interesting read:
http://www.twtex.com/forums/showthread.php?t=27917
Of course, it was found on the internet, & worth what you paid for it.
Seriously, either nitrile or buna-N would probably do fine. I'm running AL-free premium mogas in my -4, & I replaced the swelling original o-rings with nitrile. No problems in several years since they were replaced.
It's been a while since I replaced them. I can't remember exactly how I disassembled them, but it's not intuitive. If memory serves, the nut is just a lock nut, and the aluminum disc actually unscrews after the nut comes off. There's a drive pin through the center shaft that holds the lever on. If it breaks (or you remove it), the cap will disassemble itself (into the tank...).
There are *many* sources of nitrile, buna-n, etc o-rings here in the USA. The biggest hassle is knowing what size to purchase. On advice from either this list or the VAF forum, I bought a set of about a hundred nitrile o-rings of many different sizes for about the same price as one set of 4 from Van's. I can't find the vendor in my bookmarks list. I'll try to look at the box when I go out to the hangar tomorrow & send you any info that might be on the box.
Suggest signing up for the Vans Airforce forum (VAF) & search for posts by 'frankh'. He's been running gasohol for years in an injected engine. He could probably tell you what he uses for cap o-rings. Once you find some of his posts, you can send him a private message for info. Asking on the forum will just get you a lot of noise about how stupid you are to even think about using car gas.
Charlie
On 04/10/2012 03:49 PM, George Nielsen wrote: [quote] Thanks for bringing up this subject, Charlie.
From the Van's Website I found the following: "... older O-rings are black, newer ones are brown. The brown O-rings are generally auto fuel resistant, but their tolerance for the newer oxygenated auto fuels is unknown. The older (black) O-rings are no longer available. Upgrading to the newer O-rings requires replacing the fuel cap." For further information please see:
http://www.vansaircraft.com/cgi-bin/catalog.cgi?ident=1334090313-448-765&browse=am&product=fuel-cap
Does anyone - have any experience with the above mentioned brown seals on whether they can resist oxygenated fuels such as ethanol?
- know of any other sources of suitable O-rings?
- know whether one can keep the fuel caps and replace the O-rings?
As for the last question, to me it seems that one can unscrew the nut on the bottom of the cap to dismantle it and replace the O-ring. Yet they say that upgrading to newer O-rings requires replacing the fuel cap.
George Nielsen
| Quote: | Time: 06:54:19 PM PST US
From: Charlie England <ceengland(at)bellsouth.net> (ceengland(at)bellsouth.net)
Subject: Re: Gascolator (Was: Hoses and O-rings in RV-6 with Lycoming)
Forgot to mention the O-rings in the fuel caps. Older black ones will
probably swell up with any auto fuel (at least they will on USA blends).
Ask Van about the newer brown ones, or do some homework on materials.
There are plenty of O-ring materials that will work fine.
I'd suggest reading through the FAA STC's for auto fuel to determine for
yourself whether you can assume that *all* FAA approved avgas related
products are safe with auto gas. Wait; never mind. There are *no* FAA
STC's that allow alcohol laced autogas in certified aircraft, so STC's
are meaningless when looking for an answer to your question. I can say
for sure that O-rings in at least one older gascolator will dissolve in
alcohol.
Also forgot to mention tank sealant. Again, age of the original product
used matters. The older sealants used in Van's tanks will not stand up
to USA auto fuel blends (even without alcohol). Newer stuff probably
will, but you'd need to check with the sealant manufacturer & give them
the exact model # & age of the sealant to know without finding out the
hard way. (Personal experience with alcohol free auto fuel in a -4
completed in 1992.)
If you've got a 160 hp engine (higher compression), be cautious of
detonation unless you run premium. (I run premium in mine.)
Charlie
Love mogas in my Lyc, but with older planes, there have been issues to
deal with...
On 04/09/2012 04:16 AM, George Nielsen wrote:
>
> Thanks to all for your replies. And thanks to Charlie for bringing up
> the subject of gascolators.
>
> On the subject of gascolators, my RV-6 is equipped with one. As this
> is the only aircraft I have ever flown which has a gascolator I was
> wondering about its utility. Would it be just as well to remove it? Is
> Mogas more susceptible to vapour lock therein as the gascolator is
> located in front of the firewall?
>
> Thanks.
>
> George Nielsen
>
>> Time: 04:36:13 PM PST US
>> From: Charlie England <ceengland(at)bellsouth.net> (ceengland(at)bellsouth.net)
>> Subject: Re: Hoses and O-rings in RV-6 with Lycoming O-320
>>
>>
>> On 04/08/2012 09:48 AM, George Nielsen wrote:
>> >
>> > My plan is to enable my RV-6 and its O-320 engine to run on Mogas,
>> > including the variety that contains ethanol. I have taken a good look
>> > at the fuel system and done some dismantling but I have found no
>> > O-rings. The fuel system contains several hoses, some black, some
>> > wrapped in dark orange. I suppose that the latter is to protect them,
>> > is it not?
>> >
>> > I would be grateful if anyone could tell me how many hoses an RV-6 has
>> > in its fuel system, what their dimensions are and whether the fuel
>> > system also included O-rings or anything else that may be susceptible
>> > to Mogas, ethanol or water. If that is the case I would like to know
>> > how many of these are present and what their dimensions are. Thanks.
>> >
>> > Kind regards
>> >
>> > George Nielsen
>> > RV-6 PH-XGN
>> > The Hague, the Netherlands
>> If the fuel system is 'stock', as designed by Van's, and you have the
>> standard fuel pickups in the tanks (not the 'flop tubes'), then there
>> should be only aluminum line & aluminum fittings from the tank to the
>> firewall, with metal-to-metal flare fittings; no O-rings. Van's stock
>> fuel selector should be fine, as well. Depending on age, if you have a
>> gascolator, it could very well have rubber gaskets that alcohol will
>> attack. The flexible hoses are an unknown. If you can't determine the
>> actual materials in the hoses, the safe thing would be to simply replace
>> .them with teflon lined hose. (USA FAA recommendation is to replace any
>> but the new teflon type hose every 5 years, anyway, though many people
>> don't do that.) The mechanical fuel pump will likely need to be rebuilt
>> with current technology diaphragms & seals; older mechanical pumps *do
>> not* survive alcohol for very long. The carb or injector is likely OK,
>> but I'd contact the manufacturer to be sure.
>>
>> Hope that helps,
>>
>> Charlie
> |
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