Hatz Biplane Association

Lorin's airplane, snooty, has 250 hrs on it now, with no problems venting both the main tank and the hopper tank through the offset fuel cap. Every time I climb up on the built in steps I worry about the stress my 200 lbs put on it, but upon close inspection I can see no deflection or cracking. I try to use a ladder if available, but it sure is handy when one is not.

Luke

Thanks John. I will proceed with the standard filler cap and vent moved off center. I'll also keep the steps in mind when working on the fuselage.

JD

We located our filler neck 7 inches from the left side of the tank instead of the middle to make it easier to fill. We found out another advantage, in an unfortunate way, when ours ended up on the nose due to a rough crosswind landing. The fuel spilled out of the tank vent but spilled off to the side of the fuselage instead of directly on the firewall which could have caused a nasty fire. Approximately 5 gallons went out through the vent before we got the tail back on the ground.
We have had no problems with the Hatz style gas cap or vent with the plane in any normal attitude. We got the idea from looking at the long nose Hatz and added a step to the left landing gear and a removable step on the fuselage. It makes refueling MUCH easier.
John Hanson HC-012

I am building the fuel tank per the Classic plans, welding .090 5052 aluminum. I was unable to bend the 1/2 inch lip on top of the pan using a hand operated brake, I have cut a new piece for the pan and will take it to a company with a power brake. Just thought that might be of interest to those using the thicker aluminum.
I am planning on moving the filler to the side which brings up questions concerning the vent. I am wondering if it would work to use the plans type cap and vent located to the side of the tank. I think the venting would be adequate since the fuel is free to move through the cutouts at the bottom of the baffle, but perhaps someone knows better. Also I was wondering if fuel would more likely vent overboard if parked on a slope. Lastly, if I did place the vent in the center, could I use aluminum tube welded to an AN fitting which would screw int a welding flange, or would it be better to leave the center filler cap and vent, in addition to a side located filler?
Any input appreciated

JD

Can't answer your question directly, Painless, but the .032 in the RV tank probably works because the skin is in a constant state of curvature. Makes it stronger the way a Luscombe fuselage is strong...it's a tube. If I remember correctly, the rear baffle of the RV tank is .050. I went with .040 and .050 because the total thickness of .090 more closely matches the thickness of the center section leading edge plywood so that there's not a bump as air flows over the top of the leading edge then over the tank top skin leading edge. Real good reason to choose that thickness metal, huh? With the internal rib/baffles on 10" centers, the tank is very solid. Yes, my unqualified guess is that .032 would be pretty thin for the tank. I'd guess .040 to .050 to be the thinnest. But this advise is worth the price paid!

So is .032 too light for a riveted tank? I believe that is what my RV tanks are made of. I was thinking of using .032 for the entire tank. Would that thickness, in 5052 be inadequate? My biggest concern is the top, which is then being used to secure the tank to the airframe. 23 gallons of 100LL x 6lbs/gal = 138 lbs of fuel. Factoring in G-loads, is that too much to ask of .032?

Oh yeah, my tank has .040 for the main body and .050 for the lid.

I built mine the same way Kevin did his. I had a pro welder tig weld the filler neck. Had a little distortion, but it popped right out afterward. I built mine with 1/8th inch clearance on the bottom and took the sides in as close to the end ribs as I could. I had to taper the front and rear of the tank ends to miss the wing attach brackets and bolts. I wanted as much fuel as possible. Haven't filled it to measure yet, but calculations run around 25.5 to 26 gal. I just had to guestimate the curvature of the top of the tank.

Kevin, wish we lived closer so I could help with your fabric! I knocked over a can of Polyfiber reducer the other day and the smell of the little bit that dribbled out brought back good memories of covering my Hatz. You'll have fun too!

Great info here, thanks to all that posted. Seems many ways to build the petrol tank, all depends on what the builder is comfortable with skill wise and tools available. All work and that is the great educational value to homebuilding, many ways of accomplishing/building the same thing.

I built a fiberglass tank for my Piet which performed very well. No issues with fuel effecting the resins if the correct one is used.


Blue skies,
Keri-Ann

Correction. We are not sure where the other 3 gal. is supposed to go.
John