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Sight Glass Statistics

Please describe your sight glass material and if you have had problems or not.

  • Old material, no problems.

    Votes: 2 18.2%

  • Old material, problems.

    Votes: 4 36.4%

  • New material, no problems.

    Votes: 4 36.4%

  • New material, problems.

    Votes: 1 9.1%
  • Total voters
    11
  • Poll closed .
B

BigJohn

Well Known Member
I have recently heard of more sight glass problems. I think it might be helpful to gather some accurate numbers on the topic rather than go by anecdotal information. I am going to try and post a poll on this, so bear with me! Please only respond if you have actually put gas in the tank.
 
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I personally have not had a problem with the old sightglass material after 18 hours on my RV-12. I know of 3 other RV-12 owners (flying) that have experienced mutiple cracks in the "old" style sightglass material leading to fuel leaks. All three had less than 30 flight hours on their planes.

I will not install the new sightglass material on my existing tank, but will seal the holes with two plates. Or I may buy the parts and build a new tank without the sightglass. Will add a mechanical type fuel sender. This gauge is completely sealed and is NOT vented.

http://www.moellermarine.com/aftermarket/fuel_systems/fuel_senders/
(See Swingarm Mechanical Sending Units on the webpage).

Please share your experience with the sightglass so Van's engineering has a good dataset.
 
No problems so far, 27 hours. Glass looks good, no crazing, no cracks. Just part of the preflight to take a close look at it. I will just build a new tank and repaint it to match if it leaks.

I wonder if the cracks are caused by over tightening the screws causing pressure points like we see on some RV canopies from time to time?
 
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Sight Glass

I plan to proseal a piece of aluminum over the windows right after my airworthiness inspection. No real point in messing with this thing.
 
Fuel tank leak test

I waited untill I received the new window and backup plate and used them to complete my tank. I mounted the tank to a couple of pieces of wood so the tank is supported as it would be in the airplane. My mentor, Jan, suggested we put in put in 1 gallon of 100LL and run it around all the tank seams and screws to see if we had any leaks. One screw on the fuel gage plate leaked so I removed the screw, re-prepped the area and installed a new screw with ample amounts of proseal. After a week we ran the 1 gallon of fuel around the seams and screws and no leaks were observed. We then put in 19 more gallons of 100LL. Jan suggested that we use the 100LL instead of mogas because the coloring in the 100LL will leave a stain that we could see for any weeping or very slow leaks. The tank has been setting in the hangar for a week and I don't see any leaks. I plan to leave the gas in the tank until I need to install it for flying. Current guess for flying is about 3 months away due to building interruptions for holidays and skiing.

Bob Kibby
 
Needed more parameters to vote

As far as I know, no ones tank leaked when first put in. Votes should only have been placed if 20 - 30 hours had been FLOWN. Takes some sloshing and bumps to start the cracks it seems. Also, at least one person has not voted due to no computer. As usual, these results may not paint an accurate picture of the problem.

I think we now know 4 that have failed with the original window. Larry is very likely correct, the screws may have been too tight. With the original steel nuts, it is very hard to judge loose fit. They turn hard from the first revolution.

John Bender
 
Hi John,

Well as we know, all polls are subject to inaccuracies. I'm just trying to ascertain if there is still a problem with the new glass, or not. I've just finished my tank with the new glass and it won't fly for at least six months.

Actually, I like the idea of filling it up and letting it sit for a while. Granted, the vibration won't be there, but it should at least verify basic integrity.

I also find the comments about the tightening of the screws very interesting. I think I now understand why they changed the nuts from the self locking kind to plain old 6/32 nuts. It sure would have been easy to over tighten the self locking type. I just put a small socket on mine, and held the shaft with my fingers. That was enough pressure to make the Proseal ooze out around the edges.

I hope folks will continue to submit input. Especially if any of the new glass has cracked or deteriorated. If the new stuff appears to be problematic, I will do as others have suggested and cover the whole darn thing with a piece of aluminum.

John
 
Whomever indicated they were using the new material sightglass and have seen problems.......Could you please elaborate!
 
Closed the window

RV-12MarineGaugeinstalled100_1215.jpg


RV-12MarineGaugeinstalled100_1208.jpg


RV-12Fuelwindowclosed100_1206.jpg


RV-12WindowCover-up100_1205.jpg


Mine ( original design ) cracked and started leaking. I decided to eliminate the window. We have ethanol in this area, and I just am not sure it won't be a problem in the future. I think the factory 'fix' is a serious improvement over the original design, but I don't want to take a chance. If you want more details, ask.

I can turn around and see this gauge WHILE FLYING. Also, while filling, you can see this. All these things together made me change it.

John Bender
 
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Looks good John. Great idea. Keep us informed as to how it performs.
 
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John's Fuel Guage

Another advantage of John's guage is that you can see how much is in the tank as you fill it, so you don't overfill and wind up with gas running all over the outside of the fuse.

Tom
 
todehnal said:
Another advantage of John's guage is that you can see how much is in the tank as you fill it, so you don't overfill and wind up with gas running all over the outside of the fuse.

Tom
Click to expand...

I agree. If you keep your ear really close to the opening you can either hear it filling up.
 
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Need more info on new material problem.

Somebody made an entry that they had a problem with the new material. It would be helpful to have more details, or to know that that vote was a mistake.
 
I wonder if the cracking is caused by the flexing of the tank sidewalls. With a load of fuel on board sloshing about, could the flexing be twisting and stressing the sight glass? Don't need no stinkin sight glass and I mean that literally if it starts to leak. Buy a piece of Tygon tubing, glue a stopper in the end with a hole in it and calibrate by adding known quantities of fuel to the tank and mark the tubing. GA has been using this type of gage for years. After all it's what is in the tank before you fly that counts. I think Van's figured stuff would end up on top of the tank sooner or later and damage any gages that were put there.

Art Pennanen
 
Old material: problems. We had installed the tank in the aircraft with no leaks. After filling the tank with 20 gallons of fuel the plastic cracked and leaked. We now have covered the old sight holes with a .040 plate and pookied up the tank. We also installed a Moeller mechanical fuel gage on the top of the tank. We have leak checked the tank and will install it this week and recalibrate with 20 gallons of fuel. I sure hope the leak problem is fixed!
 
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Sight Glass Problems

I really like the idea of the sight glass, but the thought of cracks in the glass, or any leaks allowing fuel to contaminate the cabin area, just scares the #*/% out of me. Man, we need a fix for this! The newly designed glass and backing plate look to be an improvement. My thoughts are, that doubling the thickness of the glass could have been a easy fix. Oh well...

Another thought: All plexi is prone to cracking around stress areas. It would be interesting to know if everyone who has installed these, has taken the time to carefully smooth all of the holes and slots in the glass. I think these edged need to be finished to a mirror finish to eliminate any possibility of allowing a stress area to remain.

How about it guys, were they slick as a baby's rump when you installed them?? If so, more engineering is needed, and another retrofit.

Tom
 
Making sure

Please advise - Moeller Marine Fuel gauge product # 035722-10; do I have the right numbers? Please advise.

Thanks again to all of the 'pioneers'.

I'm a long way from constructing the fuel tank but my plan at this time is to build two tanks - one to get the elsa cert and the other to install into the aircraft later. The second one will be a bit larger - maybe about 25 gallons, and have no holes on the side that need to be covered up. Flame on.:cool:
 
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