Flop tube-fuel sender after construction question.

lancef53 · Post by **lancef53** » Sun Dec 02, 2007 9:46 pm

Ok, here is the deal- I bought a set of SB wings from another builder who had started them, and had some medical issues and elected to not continue the project. He had planned and installed standard fuel pick-ups and float sensors, all mounted on the end rib.

I want to use flop tubes, and was trying to figure out the best way to do so. The left tank is done and installed on the skeleton with the leading edge, and is the one I am the most concerned with. The right tank is partially completed and not closed up, so it is not going to be a problem.

Is my best bet to get the fill in plates for the inspection holes(part-411 something) and install the float sensors from the back side in the 2nd rib bay? Is this possible?

It seems like this would be a common problem with quickbuild wings, but I can't find a site that documents it.

Thanks!!!

Post by **bullojm1** » Sun Dec 02, 2007 10:08 pm

The first question I have to ask is do you intend to do sustained inverted flight (Fuel injected engine AND inverted oil)? If not, there is no point in putting in the flop tube. Also, be aware that the flop tube needs to be replaced every few years. Here is an interesting PDF on that issue: http://rvplane.com/pdf/FlopTubeAlert.pdf

If inverted is your goal, it might not be so simple to convert your one tank. The flop tube penetrates into the tank through the T-405 angle on the leading edge. Usually there are universal head rivets holding the angle to the tank rib. Some of them might need to be replaced with countersunk head rivets so the nut on the fitting can be tightened to the T-405. You can buy a new T-407 access panel that doesn't have any holes cut in it to replace the one with the fuel sender.

The fuel sender can be easily relocated to the second bay. Check out Chad Jensen's site (http://www.chadandbrittne.com) for how he relocated his.

Another thing to think about is the trap door between the first and second bay. With the inverted system, there is a trap door to fabricate to keep the fuel in the root bay. Since you will have to make a hole for the fuel sender in the second bay anyways, this could provide you with some access to put rivets in there.

The last issue I can think of is you might need to install some anti-hangup brackets in the tank. Sometimes the inverted tube has the tendency to catch on things in the tank. The brackets would be installed to keep the flop tube from getting in those situations.

Have you considered just putting the flop tubes in one tank and running from it when you go inverted?.....it would save you so much time and effort.

Good Luck!

Post by **Spike** » Sun Dec 02, 2007 10:16 pm

I would say just do one and use that tank for acro.

Spike

lancef53 · Post by **lancef53** » Mon Dec 03, 2007 9:35 am

Thanks for the replies, Yes I plan on the invert system and fuel injection. I had thought about just doing one tank, but I would feel more comfortable having both available.

Do you think it would be possible to make a reinforcing plate on the outside of the tank baffle t-702? basically, I would make an oversized plate for the backside of the tank and proseal it on, and then install the platenuts on the inside, sandwiching all three pieces together?

Thanks, Lance

Post by **Spike** » Mon Dec 03, 2007 11:24 am

Sure that could be possible. Its just one more place to get a leak though in 10 years. And its not accessible without taking the tank off of the wing.

Wicked Stick · Post by **Wicked Stick** » Mon Dec 03, 2007 7:33 pm

Why not leave the almost finished wing alone and leave it as the normal pickup tube, then just flop tube the other.

The regular pickup tube will probably provide the ability to get a little more useable fuel out of that tank, and then just use one tank for the flop tube/acro flying. Just placard somewhere that inverted flight must be flown on that tank.

lancef53 · Post by **lancef53** » Mon Dec 03, 2007 8:25 pm

Thanks for the replies, I will think about leaving the completed tank alone. I never thought about the useable fuel issue, does anyone know the difference? I am kind of a chicken when it comes to fuel, I always like to have plenty--the old saying about flying a heavy plane, or one without fuel!!

Why is it that it always seems like the flop tube is in the left tank? Is there a reason for this, or just a fluke?

Thanks, Lance

tmbg · Post by **tmbg** » Tue Dec 04, 2007 11:11 am

seems like most people build the left wing first!

captain_john · Post by **captain_john** » Tue Dec 04, 2007 4:25 pm

I have a flop tube in the left tank and a standard pickup in the right.

I dare say that the standard pickup will sip right down to the last few ounces of fuel whereas the flop may unport around a gallon or so?

I am just guessing at these figures, but once thing is for sure... the standard pickup dips down MUCH deeper into the tank that the flop ever will!

CJ

Wicked Stick · Post by **Wicked Stick** » Wed Dec 05, 2007 11:03 pm

lancef53 wrote:
Why is it that it always seems like the flop tube is in the left tank? Is there a reason for this, or just a fluke?

Thanks, Lance

The fuel pickup line in the right tank has less of a chance of coming loose inside because to loosen it, would mean it would bottom out on the bottom of the tank skin. So if we are only to have one regular pickup, it's best to have it on the right side, and put the flop tube in the left.

Just my theory of course.

Post by **Spike** » Thu Dec 06, 2007 8:34 am

Wicked Stick wrote:
The fuel pickup line in the right tank has less of a chance of coming loose inside because to loosen it, would mean it would bottom out on the bottom of the tank skin. So if we are only to have one regular pickup, it's best to have it on the right side, and put the flop tube in the left.

Just my theory of course.

Was ther some sarchasm here that I missed?

tmbg · Post by **tmbg** » Thu Dec 06, 2007 12:30 pm

is 'sarchasm' the inevitable gulf that separates those of us that got it from those of us that didn't?

Post by **Spike** » Thu Dec 06, 2007 1:06 pm

Very probably.

Wicked Stick · Post by **Wicked Stick** » Thu Dec 06, 2007 10:12 pm

Actually, none was intended, so I apolagize for my mis-written verbiage in advance.

Not sure if I want you messing around my EFIS just yet though.

Post by **Spike** » Thu Dec 06, 2007 10:50 pm

Wicked Stick wrote:Actually, none was intended, so I apolagize for my mis-written verbiage in advance.

Not sure if I want you messing around my EFIS just yet though.

Ill make sure to get some play time with it once you are flying