Aux fuel tanks

[caveman370]

Guys,

I plan to talk to Bill Clapp at AirVenture this year about producing a few sets of tanks. Several builders have exchanged emails with me with their interest. If you think you're interested, let me know so I have a number of sets in mind for when I talk to Bill. Plus, he might have a better price for several sets at once rather than piecemeal.

Jeff

I’m in too


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[sonex1374]

For anyone that has expressed an interested in the wing tank group and would like to be added to the offline discussion, please send me a PM with your email address and I will add you to the list. I'll use email for the next couple months as the method to keep the group informed of the project's progress. After things settle down and finalize I'll also post an update here.

Jeff

[Ad Eves]

Can the tube type wing tanks be retrofitted? What prevents them fretting on the ribs?

[Speed]

I have the Bill Clapp tube tanks. They work fine! (They may be the original ones?)

I bought N77ZZ in 2015. But the tanks were installed when he did the Corvair conversion back in about 2008. I remember seeing them and talking to him at OSH in '08, never imagining that someday I would own that plane. And, yes, I'm still running that same 2.7L Corvair, now with about 400 hours. Sweet little motor!

BLUF: They obviously hold up...10 years, no evidence of leaks. They work! Hold about 5.5 gallons each. I typically only put 5.0 max in to avoid venting (due to the low dihedral of the wing). Also, I don't keep fuel in them unless I'm going X-country.

I currently have the single pump that draws from both tanks at about .3 gal / min. (So, I typically transfer for 10 minutes, moving 3 gallons) It's plumbed into top of the main tank. Bill also put in an ingenious fuel vent that keeps one from accidentally over-filling the main and venting onto the canopy...

I did install a shutoff valve between the two tanks to prevent fuel from transferring by gravity from one side to the other (and then overboard) when plane is on uneven ground. They both have quick-drains near the wing root. The caps on the wingtips are same as RV uses.

I'm considering re-plumbing with two pumps at some point...but low priority...I just haven't been flying much due to my wife's situation. I've also considered how to do a different wing tip vent system, which would likely tie back into the main vent, located on the turtle deck, but again, low priority. I am also going to put in some inspection plates, just so I can inspect!

BUT: It sure is nice to be able to easily carry another TWO hours of fuel, and have no real impact on the CG. I LOVE THEM!

[lpaaruule]

Would the weight of the wing tanks subtract from the useful load capability structurally? Put another way, would it have to be taken into account as structural gross weight since they are in the wing tips? I'm not so concerned about sport plane stall speed, or climb performance, just potential changes to Va and useful load.

[Speed]

To be clear, the tubes run the length of the wing and are just forward of the spar. The filler neck/caps are about 6" from the wingtips. My W&B naturally includes the tubes/tanks and hardware in the empty weigh and I calculate the weight and moment for the amount of fuel I carry. They don't add any structural strength, the best I can tell. I can't comment on how much the tubes themselves weigh, but it can't be much. With the Corvair and the tanks, the plane's empty weight is on the heavy side. But, I don't mind: the engine is great and the tanks are worth their weight when I use them! It's a lot of good flying for being light sport!