RV-10 QB wings and fuel senders and leak testing order

[MElstien]

Hello. I could use some feedback on what order to conduct the following tasks on my QB wings that were built in 2006. Any other advice would be very helpful. I have searched and read all the other posts. I am worried about not passing the leak test on 12 year old wings that were in storage for 10 years and proper travel of the fuel sender floats.

I am also having initial difficulties getting the fuel sender to get to full travel and getting a visual on why. I do have a small USB camera but getting the proper view is proving difficult.

I will continue to try to get a better view on the float travel and adjust as needed, but barring not getting a good travel (both via visual and Ohm readings) what should I do next?

I was thinking about following this order:
Temporarily install the fuel sender with the gasket, install the quick drain and using the VANs leak test kit, test the tank, knowing I may get some leakage around the fuel sender/screws/gasket. My hope is that this will get me some degree of confidence quickly that the tank does or does not need work to correct the leaks. If I do have leaks, cutting the access holes is probably the way to proceed, depending on where the leak(s) is/are.

If it is good from a leak perspective, continue to try to get the fuel senders adjusted before committing to cut an access hole in the baffle for easier adjustment. I already have the leak test kits and the Tank repair covers and closed-end rivets. Heck, while the tank is open, install capacitance plates and a return line.

My goal is to not cut it open if I don't have to.

[Carl Froehlich]

Don't fix something that you do not know is broken.

Fuel sender - you will not see be able to see this with any camera on a stick as there are ribs in the way.

Fuel sender - if installed correctly it will not read any level over 24 gallons or so, but it will read down to an empty tank. When you calibrate whatever EMS module for fuel level you put in two gallons at a time to translate level indication to fuel level. There is no adjusting the fuel sender beyond the instructions for making the bends (don't for get the 90 degree bend where the float rod goes into the fuel sender bracket hole - the hole and the sender arm plastic clips are both required to hold the float rod).
DO NOT CUT A HOLE IN THE BAFFLE.

Fuel sender gasket - this gets proseal on both sides or you will have a leak.

Leak test - does a good job of finding gross leaks but not common weeping rivets. Take the tanks off the wing and let them sit on a workbench for a couple of weeks in different positions will five gallons or so of 100LL. If you have a leak it will show up as a blue stain. Keep the tank vented when you do this.

My experience is that capacitive plates are far more problematic than the simple float level. I would never use them.

Carl

[MElstien]

Tonight I spent a few more hours in the shop with my USB camera on a flexible wire and my ohm meter. I had already bent the wire per VAN's measurements including the return bend that acts as an anti-rotation tab and goes into the fuel sender pivot point. The bends were quite accurate and true.

Summary:

1-The float does bottom out where it should physically and the resistance also reads the max of 247Kohms. This is the 'tank Empty" value. Good and the most important reading.

2- The float does not travel to the top of the tank. I found that it clears the vent tube but hits the skin stiffener. There is not enough clearance between the vent tube and the float to correct for the overlap of the float hitting the stiffener. So, the resistance at max fuel reading is 56.2 Ohms and the min on the sender is really 31 Ohms. This does not sound like much but it appears to be a significant amount of travel on the float arm. See picture and video. The picture shows where the float arm is at 56.2 Ohms. The video shows how much movement is still left from the 56.2 Ohm reading to the stop point and reading of 31 Ohms.

http://elstien.us/RV-10%20Build%20Lo...%20picture.JPG
http://elstien.us/RV-10%20Build%20Lo...r/IMG_6046.MOV

3 I realize that I will calibrate the tanks by adding fuel in known increments and it is good that Zero, will be as accurate as possible.

4) But if the float does not travel to the top of the tank, It will read full for a longer period of time than I may desire casting doubt on range and duration. I plan on using a fuel flow meter, but I would like the added information from the floats. Also, won't the EFIS fuel reading jump from full to something less than full the moment the arm starts to move, say from 30 to 24 Gallons. I guess I could calibrate it to only read 24 gallons or whatever the actually reading is when the float hits its artificially short stop. I visually check that the tanks are full every flight anyway so I would know I would have a known amount of extra fuel to burn before the floats become "Accurate".

5) I wish the QB wings came with the floats installed. It appears the QB team did not bend the fuel vent per plans to accommodate the space needed for the float.

[Machsandy]

Our gauges are calibrated in litres and the max reading is 75 litres = 19.8 galls.

The system works really well so when full the gauge reads 75 litres and then after about 45 mins flying per tank the gauge begins to reduce below the 75 litre indication. We also have a fuel flow meter and this gives an even more accurate indication when the tanks are really full as well as this being confirmed by the gauges once below 19.8 galls a side.
Finally we run a calculation using known consumption figures.Out of interest running lop we use 11.9 galls per flying hour plus 0.8 galls for eack start up and taxy (45l/3l). So we have 3 reliable sources of fuel on board and the gauges become accurate after 45 mins from full.

The fact the gauges under read when full is of no operational consequence in our experience.

[mturnerb]

I just did this on my RV-14A qb wings - no idea how similar this is to RV-10 but I assume there must be some comparison given same wing design. I used an endoscopic camera (flexible) to check float position using holes for the fuel strainer and one above it that ends up getting a "plug". Similar to other RV-14A builders I found that I had to put a "V" bend in the float arm to get clearance from the rib. If you look at my blog (in signature) you can see photos from my camera on the right wing install which I just completed. I did this with tank off the wing so I could easily flip it up/down to check float movement and position.

Check out this thread as well: http://www.vansairforce.com/communit....php?p=1083062

Of course I don't recommend copying what I did (YMMV) but I found the advice in that thread immensely helpful.

[Carl Froehlich]

Originally Posted by MElstien

. SNIP

2- The float does not travel to the top of the tank. I found that it clears the vent tube but hits the skin stiffener. There is not enough clearance between the vent tube and the float to correct for the overlap of the float hitting the stiffener. SNIP

I?m not sure how you can manipulate the float arm with the sender installed.

Assuming you can and not interfere with the sender arm itself, perhaps you can put another bend in the float arm rod to clear the tank stiffener. I built my tanks and recall needing to tweak the rod a touch to clear such interference - but I did it before installing the rear baffle. You should also verify the rod lengths correct. If memory serves, if a little long you will hit a stifferner. Which way the float itself is pointing makes a difference. You will need to do some trial and error work.

At any rate, considering the tank design that last little bit of travel may not every be a gallon of added reading. I find the float accuracy to be within a gallon if properly calibrated to the EMS. For practical use, the EMS fuel flow sender is most accurate - but the float senders provide very good cross reference to identify fuel that you thought you had but don?t (shorted by the line guy filling the tanks, fuel leaving the tank via a path other than the engine (sump valve leaking, etc.). The fact that even as is your sender will read at least 20 gallons in the tank means you have very good indication of fuel status for the long cross country legs.

Carl

[rvbuilder2002]

Originally Posted by MElstien

2- The float does not travel to the top of the tank. I found that it clears the vent tube but hits the skin stiffener. There is not enough clearance between the vent tube and the float to correct for the overlap of the float hitting the stiffener.

The float can be clipped on to the arm with it extending fwd or aft.
Often times just flipping the float around on the arm give clearance from things like internal stiffeners, etc. (I don't remember if the 10 plans specify which way to orient the float....)

[Richard Connell]

I found that it?s a pretty tight fit between the vent tube and the stiffener.
After plenty of fiddling I got it to swing freely but there?s enough play in the mechanism that I can envisage it hitting one or the other at some point in the future. I probably should have trimmed the float down in hindsight to make sure.

[MElstien]

Hello,

I am still fiddling with it to see if the float will fit between the vent line and the stiffener. I also called Stewart Lambert to see about trimming the actual float down by 1/4 inch or so. They had no response on if that would be acceptable or not.

The problem seems to be that the QB builder did not bend the vent tube away from the stiffener per the plans allowing for more clearance. In the picture below, the tube should also bend away from the upper skin stiffener. See Richards graphics several posts before this post.

Vans had no good response either. Do I accept this or try to move the vent line? I think I will continue to fiddle with the float wire today to move the float away from the stiffener and see how much it overlaps with the vent line. Then test the tanks to see if they leak.

[Richard Connell]

Hi Michael.
Looking at your photo perhaps they did bend the vent line correctly but it has rotated.
Perhaps you can try loosening the B nut on the vent line and rotating the vent line 90 degrees.
I recall seeing someone had modified a crows foot wrench to use it through the sender hole.
Good luck
Richard