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Fuel Tank Sightglass Leak

MartySantic

MartySantic

Well Known Member
Well folks, after 25 hours and about 4 months my original sightglass on the side of the tank developed a leak. I had not installed the new glass material. Was waiting for warmer weather. Found about 8 ounces of gas on the floor of the hangar this morning. I have drained the tank and removed the tank but have not started dis-assembly. Will do that this weekend and post a report. Appears as though the plexi has cracked, very similar to what others have reported.

Had just flown the plane from the paintshop yesterday and found the leak today. The paint, looks fine...no damage, I am happy to report (that is, after my brief look).

I refuse to install the new glass material. Will seal the holes with a plate sealed inside the tank, and another plate sealed outside the tank. Will also install the stiffener that came with the window revision inside the tank.

For a local indicator will use the same sealed marine float gauge that John Bender suggested and has installed.

I e-mailed Van's a few months ago and asked if they could send me a tank part without the holes. If they could/would, I was considering just building a 2nd tank. Their response was no, because the QA in sending me an alternative design would be horrendous. I can relate as before retirement I was an engineer in the nuclear industry.

IMHO, the sightglass design, new sightglass material or old sightglass material is a weak point and Van's should modify the design and provide a tank with an alternative means of checking the level locally (ie. a marine gauge or some other alternative).

Clearly, a new line of thinking is required here.
 
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Major bummer. Sorry to hear this.
What if a skilled welder put a solid piece over the entire sight window opening? Is that doable?
 
Problem

If you tried to add it over the window by welding, you'd have a problem with the plastic inside if you didn't remove it. If you take it apart to remove the plastic, just seal it up.

John Bender
 
proseal is the way to go...welding this size of aluminum is a **** shoot at best. Marty's answer is the correct one. I did my own even without cracks just for peace of mind. Everything is fine now. And the plane is wonderful...the sight glass shouldn't keep anyone from building this plane. I would do it all over again...and might!
 
diamond said:
Major bummer. Sorry to hear this.
What if a skilled welder put a solid piece over the entire sight window opening? Is that doable?
Click to expand...

Welding such a thin material is very hard. Our nuke plant certified welders agree. Better to pro-seal a plate over the holes.

BTW, I am otherwise MOST satisfied with the design of the RV-12. Cruising at near 120 knots, burning 4-5 gal/hr (mogas) makes this airplane just a joy. My ground speed back from the paintshop was 135 knots.
 
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I have to agree with Marty

Though not an aeronautical engineer or 'expert', it looks to me that Van's should change the fuel tank design. I am a retired firefighter and so know quite a bit about gasoline and fires and the thought a leaking gasoline tank near me is terrifying.

So, I'll follow the plans and build my tank as per instructions. BUT, before I construct my tank, I'll measure the tank parts carefully and make patterns for use after my 12 is certified, etc.

Then, I'll construct my tank of a heavier guage aluminum and there will be no glass or holes to look thru. Will do some w&b calculations and see if I could add a few more gallons capacity in the process.

I'm interested in making my 12 as safe and good flying aircraft as possible. I'm not too concerned about gross weight as after our diets, my wife and I now total 345#s fully dressed and full of food. We will continue our diets in effort to further improve the performance on our 12. Also, hope that the weight loss will allow us to live an active life for a lot more years.

There will come a day when we have to sell our 12 and that's when the original tank will be placed back into the aircraft.

I don't think that Van's can make a fuel tank change to the aircraft without spending a lot of $$$ to certify the changes. So, it's up to us to make the changes that we think are needed.

Overall, this is an OUTSTANDING KIT AIRCRAFT and ENGINEERING ACHIEVEMENT. Thanks again to Van's and to those who are the 'pioneers' in building the first several kits.
 
It looks like I am the only one left with the original site glass and after 8 months and 50 hours it is still good, but Marty's leak has convinced me it's time to pull the tank, remove and seal the site glass hole, and do the "Bender fuel gage modification".

http://www.amazon.com/Moeller-Marin...TCRBE/ref=pd_ts_sg_4?ie=UTF8&s=sporting-goods

The plane is down for paint anyway so this is a good time to do it since the good flying season is right around the corner.
 
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JOHN BENDER STATEMENT

Builders. I feel this particular item ( fuel window ) is the least desireable feature of the entire build - HOWEVER - it is easily fixed later, and I hope all these posts have not discouraged anyone from building an RV-12. I have over 50 hours on mine now, and it is a SUPERB aircraft overall. This is a weak spot, but can be fixed with a few hours of work. I would strongly suggest 'closing the window' after inspection, and install the Moeller Fuel Gauge on top as I did. You can turn around and see it in flight, and you can see it while filling. NO LEAKS ! It's a great plane !

John Bender
 
Open letter to potential builders reading this thread...

Designing and supplying a kit for an airplane is a complex process.

Occasionally things needing to get changed, get found after an extended operational period.

This occurred with the fuel level site window on the RV-12 and a change was made and parts supplied an no charge to all builders.

The two company RV-12's have been flying for many months and many hours with no problems using the new site window.

It is no surprise that builders who chose not to follow the recommendation of Van's Aircraft and install the new site window, are experiencing a failure of theirs (that is of course why the change was made).
 
Why all this complaining....

.... about the sight gauge? They (Van's ) had a problem, and they fixed it. I haven't heard of any problems at all with the updated material. Why keep beating a dead horse? It does not help the reputation (read that re-sale value) of the RV-12. May I respectfully suggest we give this topic a rest?
 
BigJohn said:
.... about the sight gauge? They (Van's ) had a problem, and they fixed it. I haven't heard of any problems at all with the updated material. Why keep beating a dead horse? It does not help the reputation (read that re-sale value) of the RV-12. May I respectfully suggest we give this topic a rest?
Click to expand...

The tank is fine, it is the site glass that is the problem. You cannot see it when filling the tank, you cannot see it in flight, and it cracks leaking fuel. John Bender came up with a great fix that we are now just installing the second fuel level gage in Marty's and my fuel tank. We are still experimenting with a permanent fix so until we get it resolved this is the place to discuss the alternatives.

Resale will only be hurt if we do not come up with a permanent fix.
 
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rvbuilder2002 said:
D
It is no surprise that builders who chose not to follow the recommendation of Van's Aircraft and install the new site window, are experiencing a failure of theirs (that is of course why the change was made).
Click to expand...

Not happy with your response, sorry. When I called Van's technical support they told me that your RV-12 had 300 hours and a year and was just starting to see problems in the sightglass. As such, I was not worried and with less than 30 hours on the RV-12, I was hoping for some good weather before pulling the tank. My tank had been built and was painted BEFORE the new sightglass was offered. How can you be confident that the new material is fine after a few months?

Obviously the sightglass material supplied to the original builders was not the same as the sightglass installed in the prototype (#003). I now see many of the original builders have experienced problems with the original sightglass material with less than 50 hours.

Maybe you can elaborate why there is such a difference.
 
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Mention again

We here in the midwest are subject to ETHANOL. Not sure anyone can say for sure what the long term affects are with plastic and ETHANOL. The other advantages of being able to see while flying, and filling, combined to make me not take a chance on ETHANOL causing a problem down the road. It is an alternative worth considering. I will state again, that I feel the factory fix is likely good, but I don't want to find out long term the plastic degrades from ETHANOL ! A good worthwhile discussion. I am offering this as an assurance for those who don't feel comfortable with the plastic.

John Bender
 
Doesn't Matter

It doesn't matter ya know. Once you have your certificate you can change it...and should. That's the point. To expect a guarantee from a fix is pretty short-sighted. The first one didn't work and I would have rightfully expected the manufacturer to support it as strong as they are the second one. Its an unnecessary device and too much failure potential for my own satisfaction. Once you build it you get to decide on your own. The manufacturer is a business and would be foolish to consider changing the new one until (and if) it fails. The good news is you get to decide. Many flying now are concerned for their own piece of mind and would like to make sure you know why. Personally, I would feel pretty sad if someone burned a hole in the ground because the second try didn't work either. These are experimental you know...sometimes experimenting for your own safety is not that bizarre. As Nike would say, "just do it!" and stop worrying about whose feelings are getting hurt.
 
Question about the Moeller Marine Gauge;
When the Moeller indicates full, is the tank completely or almost full?
Any change to bent the float arm?
 
Gagarin737 said:
Question about the Moeller Marine Gauge;
When the Moeller indicates full, is the tank completely or almost full?
Any change to bent the float arm?
Click to expand...

Since the gage is located on the forward end of the tank it will show "full" before the tank is acutally full. When my gage indicates full I can still add 2.9 gallons then the tank is full. The position and slope of the tank of does not allow for float adjustment.

The best features of the marine gage is it can be seen when filling, it can be seen while in flight, and it is very accurate.
 
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Thanks for the info!
I want to order one but no shipping outside the USA.

I'll rivet a piece of aluminum on both sides of the sideglass position. What thickness is used by others?
 
What I did

If you have the latest update, with the stiffener, just install everything EXCEPT the plastic window. Be sure you sand or scotchbrite the inside and outside VERY WELL. Put a lot of 'gooo' on the original plate, and install it on the opening inside. Install the stiffener over it, and seal around it well also. Do the screws as instructed. Spread all that squeezes out of the holes around the outside as smooth as you can. No leaks, no problems.

John Bender
 
Gagarin737 said:
Thanks for the info!
I want to order one but no shipping outside the USA.

I'll rivet a piece of aluminum on both sides of the sideglass position. What thickness is used by others?
Click to expand...

That is what I did. I put a piece of aluminum inside, another outside. Also put the stiffener inside. The material I used was either 0.025 or 0.032. Made for a neater installation.

There may be enough room to mount the gauge on the flat portion of the tank far aft (would give a better FULL indication), BUT, it would be hard to read when filling and when in flight.
 
Covering the Site Glass Holes

I used .040" inside and outside. I Rounded the corners nicely, to accommodate the existing screw hole pattern and used AN 426 4-4 rivets, along with a good coating of proseal on all parts. By using flush rivets, the patch is hardly noticeable, and I doubt that it will leak. It was an easy mod while building the tank. Actually, I was able to squeeze all of the rivets, by covering the windows before I installed the rear, end panel.

Tom
 
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