Brodhead Pietenpol Association

Original Posted By: Owen Davies

Original Posted By: TOM STINEMETZE
I pulled the fuel tank out of the nose tonight, it literally took about twenty minutes to remove the cover and fuel tank. What a simple job! It is great to have something that is so easy to work on. Now I have some questions about repairs to the tank:The tank is mounted in the nose above the passenger's feet, so any fuel leaks at this fitting are in the cockpit. For that reason, I'd like the new fitting to be strong enough that the tank would break before the fitting fell off. If this fitting had broken off in flight, all of the fuel (18.3 gallons when full) would have drained into the passenger floorboard (not to mention the engine would have been dead). This experience has given me a strong appreciation for fuel tank designs like Chuck Gantzer's, where the fuel is entirely isolated from the cockpit interior. Excellent design, in my opinion.For the new fuel fitting installation, I'd like to be able to screw a 90 degree elbow to the new tank fitting, and screw a new fuel valve to the elbow, that way the valve won't drop 5" from the bottom of the tank like it did on the original install. I also intend to install a cable operated fuel shuttoff, which it didn't have before. I can handle all of that, I just haven't done fiberglass work before, so I'm leary of repairing the fiberglass tank myself. It is about 21" inches from the filler neck down to the sump/fitting location (through the tank). There is no way to access the inside of the tank except through the filler neck. The tank is "three layers of fiberglass with Safe-T-Poxy" according to the logbook. Could I possibly cut an access hole in the top of the tank, install the new fitting through that hole, and then patch the hole? Is patching a fiberglass tank that simple?Tom, I believe this is the "top hat" flange you were talking about, that works with the finger strainer:http://www.aircraftspruce.com/catalog/a ... .phpThanks for the help everyone.Steve RuseNorman, OK ----- Original Message -----

Original Posted By: Steve Ruse
Steve,I've built several epoxy tanks and can make the following suggestions: a) you have to cut a hole in the top of the tank to be able to access the interior or it will not hold, b) the hole in the top is less likely to leak, c) get inside and scuff the surface up about 6" by 6" use min. 80 grit. d) using epoxy and flox, glue a 1/4 thick, 3" by 3" AL flat stock over where you want the hole, on the inside of the tank. e) using a satin weave like 7781 fiberglass, laminate over the AL flat stock, after you have floxed the edges of the AL flat plate so the glass laminate transitions smoothly to the tanks surface. f) use min. four plies of fiberglass. g) now on the outside of the tank, laminate 4 plies of epoxy and fiberglass about 8" by 8" over the area of the AL embedded plate. h) after the epoxy cures, you may want to heat it with a hot air gun until it's kinda hot to the touch. Drill and tap a hole for the new threaded fuel fitting., i) vacuum up any drilling waste out of the inside of the tank. j) now to fix the hole you cut in the top. Take the piece you cut out and rough it up 80 grit. k) take popcicle or tongue depresser sticks and flox them to the four sides of the cutout piece. l) after they have set up, put the cut out piece back in the hole you cut, using the sticks to support the cutout piece. m) using flox and epoxy you can now tape a strip of epoxy around the edges you have cutout. n) after this sets, remove the wooden sticks. Now put min. four plies of epoxy/fiberglass over the entire cutout piece overlapping to the tank by 2" all around. The trick to getting good bonding is always make it very very rough. Epoxy is hard to stick to, there's no chemical bond to the tank's surface, so you have to get a good mechnical bond. Also, anytime you're repairing a fuel tank, it's gonna have oils/fuel additives in the epoxy, so you absolutely have to get these scrubbed off with acetone/ and 80grit to get a new laminate to bond properly. Any questions you can give me a call at 907-235-4882 or email off group.Gordon ----- Original Message -----

Original Posted By: Steve Ruse
I pulled the fuel tank out of the nose last night, it literally took about twenty minutes to remove the cover and fuel tank. What a simple job! It is great to have something that is so easy to work on. Now I have some questions about repairs to the tank:The tank is mounted in the nose above the passenger's feet, so any fuel leaks at this fitting are in the cockpit. For that reason, I'd like the new fitting to be strong enough that the tank would break before the fitting fell off. If this fitting had broken off in flight, all of the fuel (18.3 gallons when full) would have drained into the passenger floorboard (not to mention the engine would have been dead). This experience has given me a strong appreciation for fuel tank designs like Chuck Gantzer's, where the fuel is entirely isolated from the cockpit interior. Excellent design, in my opinion.For the new fuel fitting installation, I'd like to be able to screw a 90 degree elbow to the new tank fitting, and screw a new fuel valve to the elbow, that way the valve won't drop 5" from the bottom of the tank like it did on the original install. I also intend to install a cable operated fuel shuttoff, which it didn't have before. I can handle all of that, I just haven't done fiberglass work before, so I'm leary of repairing the fiberglass tank myself. It is about 21" inches from the filler neck down to the sump/fitting location (through the tank). There is no way to access the inside of the tank except through the filler neck. The tank is "three layers of fiberglass with Safe-T-Poxy" according to the logbook. Could I possibly cut an access hole in the top of the tank, install the new fitting through that hole, and then patch the hole? Is patching a fiberglass tank that simple?Here are some pictures of the tank and fitting:http://www.wotelectronics.com/Bottomoft ... ner.JPGTom, I believe this is the "top hat" flange you were talking about, that works with the finger strainer:http://www.aircraftspruce.com/catalog/a ... .phpThanks for the help everyone.Steve RuseNorman, OK ----- Original Message -----

Original Posted By: "Douwe Blumberg"
Subject: Re: Pietenpol-List: Bad news - broken fuel tank fitting & warning to builders>I pulled the fuel tank out of the nose tonight, it literally took about twentyminutes to remove the cover and fuel tank. What a simple job! It is great tohave something that is so easy to work on. Now I have some questions aboutrepairs to the tank:Steve,I've checked very carefully both groups of photos. It seems, at leastto me, that two things are worth noting:1) The tank in itself seems good enough to do the job, and should bekept.2) The installation of the finger strainer flange was really verypoorly made but it can be re-done properly.The reasons why the flange was pulled out are many:1) It was not bonded to the underlying lamination at all2) The holes in the outer portion of the flange are too small and toomany3) It was only "bonded" with resin with no top laminationsNow let's see how it can be fixed. First, you say elsewhere thatsafe-t-poxy was used for the lamination, so that is what you shoulduse. You should also look for some 8-10 bidirectional glass cloth,twill weave, industrial grade (aviation grade is not really necessary)and cotton flocks ("flox"). The work should be done withoutinterruptions i.e. you should always work with something "wet" under.1) Remove all traces of the old bonding and roughen the surface of thetank around the bottom hole in a radius of 3" + flange radius using a60-80 grit sandpaper.2) Remove all glue traces from the flange and enlarge the bondingholes. Using a rattail file, file away material between two adiacentsmall holes and enlarge the resulting slot with a large round fileuntil it becomes a large hole. Roughen both surfaces of the flange with60-80 grit sandpaper and degrease it in lacquer thinner or MEK.3) Prepare a small quantity of resin, then mix with flox until theresulting paste does not run off. Spread a 1/8" thickness over the areathat should receive the flange. More if the area is not flat.4) Press the flange into position. The flox paste must ooze out of ALLthe holes and around the flange itself. DO NOT EVER lift the flangeotherwise all the effort to make a leak-free joint will be wasted.5) Very carefully level the oozed paste into the holes and around theflange, taking away any excess.6) Prepare three discs of fiberglass cloth with a 3/4" center hole: one2" larger than the flange, one 4" larger and one 6" larger.7) Place the small disc over the flange and through its threaded boss,and laminate it down the usual way. Use an excess of resin, you want tobe sure that no delaminations/trapped air exist.8) Place the middle disc over the freshly done small disc, with theweave at 45 degrees with regard to the weave of the smaller disc, andagain laminate it down the usual way.9) Place the larger disc over the freshly done middle disc, with theweave at 45 degrees with regard to the weave of the middle disc, andagain laminate it down the usual way.Done. You should now let the laminate cure fully and set completely,perhaps leaving it untouched for a week, then test it for leaks usingreal fuel (do NOT use water as it is more viscous, you can have noleaks with water but leaks with fuel, been there done that).This technique was taught to me many years ago by a professional workerin the aerospace industry, and I used it in all my flange-relatedfiberglass work.SeeYa!Andrea VavassoriVolksplane VP-1 I-BYRAEAA #348037FCAP I-146Homepage: http://andrea.modelberg.it________________________________________________________________ Virus and Spam checked by NSS Srl - http://www.nssitaly.com Compliant to DL #196 30/06/2003 Definition count: 606102Definition date: 2008/03/11MDAV version: 2.2.9________________________________________________________________________________