H

hector

Member
G,day all,
Was wondering if I may get a bit of help for a few things on my flying -4.
I am still building a -4, very slowly, but in July 09 I bought a flying one to start up a business doing fly out repair work in the top end of the Northern Territory. (Australia). All is going well, the only problems I am haveing with the 'plane are that the cowl hinges keep breaking, and the fuel caps don't last long.
first the cowls. time in service is about 780hrs. the originall builder didnt do a very good job, and an extensive amount of work was done for it to pass CASA survey. Following that, it had a heavy landing/crash that required new eng mounts/gear legs/cowls. Not much in the log books of note after that except reskining one fuel tank (leaking) and another set of cowls. I have put about 120hrs on it since July and have had to repair the cowl attach hinges twice in that time, on the right side, at the front, both behind the spinner and at the outbord section. I now have a piece of .040 aly screwed to the two halves to hold it together behind the spinner. When the cowls are put in place they seem to sit O.K and it's not like I need to get to rough to get the pins in. At present I am just putting progresivly heavier aly on to hold them together, but am a bit woried that I am moveing the stress to another area. I realy would be a lot happier if the cowl did'nt come off in flight and wrap around the tail as I recon it would significantly degrade performance.
Are issues with the cowl hinge pins a common problem on relatively high use
-4's or is there an underlieing problem on this one? I do no aero's, encounter moderate turbulance, 50% dirt strips, 155Kts cruise,Sens metal prop. wouldn't say it has any vibration issues.
Other issue is the fuel caps. The ones that came with the 'plane would not lock down properly, so I took the new ones from the one I am building and started useing them, and they have already broken the roll pin that holds the tab on. cant find a new pin for lovenormoney, so ordered a new set from the factory and now carry spares around with me. Does anyone know the part No for the pins? and is this also a common thing or have I just got a dud fuel cap?
Sorry for rambling on, I realy am very happy with the way the 'plane performs, and it sure beats have to work for a liveing, but would like to try and clean up all the lose ends.
Any and all advice/sugestions welcome.
Cheers
Bill Markey,.
A Wing and Repair.
Remote Area Repair Rectification and Recovery.
Northern Territory
Australia.
 
hector said:
Other issue is the fuel caps. The ones that came with the 'plane would not lock down properly, so I took the new ones from the one I am building and started useing them, and they have already broken the roll pin that holds the tab on. cant find a new pin for lovenormoney, so ordered a new set from the factory and now carry spares around with me. Does anyone know the part No for the pins? and is this also a common thing or have I just got a dud fuel cap?
Click to expand...

A common replacement for the fuel cap pins is either 1/16" drill rod or, my favorite, 1/16" stainless welding rod. I carry a 6" length of the welding rod in the plane in case there is a need to cut a new pin on a trip. It can be cut with a sharp pair of wire cutters and will deform a little instead of breaking the cap.

However, if the large o-ring is occasionally lubed, and the caps adjusted properly, pin breakage is quite rare. When you refuel, dip a finger in the fuel and rub some fuel on the o-ring. Make sure the large nut on the bottom of the cap is adjusted so only a small amount of force is needed to secure the locking lever. The part of the cap near the nut is also threaded, be sure it hasn't turned a little and moved away from the nut and squeezed the o-ring.
 
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fuel caps

Bill - on the fuel cap question, the parts are all available from Van's and other sources. Can get the roll pins from Van's for $0.43 each (do a search on Van's on-line catalog home page for "FUEL CAP ROLL PINS" as I don't see them on the page with the other fuel cap spare parts). Spare tabs and o-rings are also available from Van's. I carry a small plastic bag in the plane with a couple roll pins, o-rings and tabs - doesn't weigh much or take up much space.

I've found it to be a good idea to take the caps apart about every 6 months to clean and lube (I used DC-4 last time and seems to work fine). That, along with keeping the nut adjusted so it's not too tight has worked for me and I haven't broken a roll pin since I started doing this (breaking a roll pin is what caused me to take them apart the first time and I used part of a 1/16" drill bit as a temporary roll pin at that time until I got replacement pins).

Do a search on VAF for other threads on this subject. Here are a couple:

http://www.vansairforce.com/community/showthread.php?t=27832&highlight=fuel+cap+pins

http://www.vansairforce.com/community/showthread.php?t=16086&highlight=fuel+cap+pins

I can't comment much on the RV-4 cowl hinges but the hinges on my -6A have held up fine so far. There are threads in the VAF archives on this subject as well though if you use the search function above.
 
Hector,
Like sam said, when I fill my tanks I simply just drip or smear a little fuel on the Oring before I drop the cap back in the whole. This little bit of lube is all it takes for smooth operation of the tab on the cap. My 4 has 1100 hrs and 15 years of service and I have never replaced a pin. If you have to force the tab over it needs lube.
Regaurding the hinge pins. Alot of us opted for an alternate at the front hinge pins behind the spinner. Instead of a hinge I installed a plate on each side about 2 inches wide of 063 aluminum fixed to the bottom cowl halves with rivets and 3ea 10-32 nut plates on the top half (each side) to hold the top half of the cowl. I have never had a problem there. I have had a couple of eyelets break on the upper hinge on the firewall on the far right corner. Something you can do that will help with this is to build a solid stand off from a fixed portion of the front of your engine that rests against the bottom cowl. Like a crutch. Use some form of rubber such as an old piece of air hose where it contacts the lower cowl. This seems to help prevent some of the lifting of the cowl and helps reduce the strain on the hinges.
Ryan
 
There is a better solution to caps

Van's also sells a retrofit locking cap. I don't see it in their catalog, however they do display it at their counter. You receive two locking caps, manufactured in the UK by Newton Equipment Ltd, together with a sleeve you pro-seal into the filler neck. It is an easy retrofit that will take less than one hour for two caps. The locking caps have one or two "O" rings around the circumference of the cap. No leak problem and also provides a sense of security because it would take a more determined person to open the cap without a key. It all remains flush with the top skin. I have installed these in two of my RVs and found them very satisfactory over many years.
 
Cowl Issues

Bill,

On the subject of your cowl, I would add that it might help to have your prop dynamically balanced if that is convenient for you. Eyelets breaking off on the hinges suggest a vibration issue, but probably a combination of flight loads too. Do you use the camlocks along the top rear? Also, on the rear bottom, #8 screws work better than the hinge pins. These two things probably help reduce the load on the area behind the spinner. In other words, the more securely you have the cowl fastened to the firewall area, the less it is going to move around in the front.

Just a couple of things to think about.
 
What type of hinge are you using behind the spinner

For you to have the expected longevity of the two short hinges between the upper and lower cowl, this needs to be extruded hinge and not regular open eye hinge material. The plans have always called for extruded hinge in that area.

My personal experience with two different RV-4s, with fixed pitch and constant-speed, the extruded hinges last maybe not forever, but they do last a very long time.
 
Thank you to all that have helped, Have done another 8 hrs since last post and all is o.k at presant. will have to look into the extruded hinge and see if I can follow up on some of the other sugestions.
Cheers,
Bill Markey
A Wing and Repair.
Northern Territory.
Australia.
 
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