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Fuel tank onboard rib question for 7A

Drawing 16A shows a cork gasket between plate T-708 and the onboard rib (coordinates B5 and G8). However, there is no gasket on the packing list, and there was none in the wing kit when it arrived. Further, there is little discussion of gaskets in Section 7 (e.g., page 7-6 and 7-8). Are cork gaskets required? If so, how do I obtain them? Have already emailed Van?s, haven?t heard back yet.

Also, are there any more detailed instructions on attaching T-708 to the rib? The holes and directions show that they are bolted to T-407 but it looks like T-708 is riveted to the rib under the fuel sender base plate. Would appreciate clarification.
 
Tank

There should be a sending unit kit with all the parts and an instruction sheet, including the gasket if you choose to use it. There is a monting ring riveted to the inside of the tank rib. Nut plates are attached to this assembly. Some of us used sealed nutplates. The rib is installed like all the others. Most builders proseal the cover in place without a gasket.
 
There should be a sending unit kit with all the parts and an instruction sheet, including the gasket if you choose to use it. There is a monting ring riveted to the inside of the tank rib. Nut plates are attached to this assembly. Some of us used sealed nutplates. The rib is installed like all the others. Most builders proseal the cover in place without a gasket.

For what it's worth, I just finished the assembly of the LH tank on my RV-10 and did not use a gasket between the fuel sender flange and the inboard rib. I sealed it with flamemaster tank sealant only. Pressure tested over several days using a magnehelic gauge and saw no air loss, only fluctuations in pressure with ambient temperature.

Here's hoping it holds up with fuel!

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yes, there should be a cork gasket that mimics the T-407 reinforcing ring shape, (except for the rivet holes). Section B-B shows the stack-up. The reinforcing ring is riveted to the rib via the anchornuts.

Some folks eschew the cork gasket for Proseal. I did a combo. I punched 1/4" cork disks and tacked them over each anchornut rivet with proseal, then used access panel Proseal to seal the T-708 access plate. This provides a designed in thickness of sealant by allowing the plate retaining screws to torque against the cork spacers. Avoids scalloping between the screws and a paper thin thickness of sealant at the screws.

Or, you could just build it like Vans says!

I would not use the rubber sender gasket though. That will crack/split and leak in about ten years. I used Proseal there as well.
 
Nutplates are riveted in assembly with T407 to the INSIDE of the T703 tank rib.
T708 cover plate is held on the rib with screws. Note the T708 as pictured is for the LEFT tank, where the circular plate is cut off flat in one spot is positioned towards the front of the tank. Do a trial fitting of the pickup tube plumbing to orient their relative positioning, this will help you orient where the nutplates for the fuel sender should go and not rivet them inside out.

A lot of builders forgo the cork gasket and use tank sealant only instead, better chance of avoiding any leaks in that area some time in the future. Same for the fuel tank sender. Also note that the screw pattern for the fuel senders are matched to their mating fuel sender Left or Right.

Hmmm, fl-mike beat me to it...

Good luck on your built
 
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Gents, thx to all for getting right back. Looks like good comments all the way around.

FYI, my instructions say (paraphrasing) ?do not use the rubber gasket between the sender and 708,? so that is consistent. Still haven?t heard back from Van?s about the missing gasket. May just use Proseal instead.

Any idea why 708 is bolted to the rib on the outer ring, but has holes to be riveted under the fuel sender? Should T-708 NOT be riveted to the rib? Does it matter?
 
The T-708 attaches to the rib/T-407 using screws around the perimeter. The larger hole in the T-708 plate has platenuts for the sender unit to attach to. I hope this makes sense!

The only platenuts riveted to the T-708 are for the fuel level sender.

I have a T-708 here already made up, please feel free to email me for a photo if you like.

hugh-thomson at hotmail dot com.
 
Any idea why 708 is bolted to the rib on the outer ring, but has holes to be riveted under the fuel sender? Should T-708 NOT be riveted to the rib? Does it matter?

To which rib are you referring? There is no rib in the drawing (16A, detail C), nor any bolts involved here. Attaching hardware will be #8 steel cad plated screws.

Highly recommend fresh Proseal over any gasket material for this application.
 
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