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wing tank replacement

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Posted

Well it finally happened. I had my avid for just over a yr and now the right wing tank is leaking. I am thinking it would be better to go ahead and replace rather than slosh and hope for the best. My question is the tank is a 15ish gallon tank with the 1/4 turn metal cap with the goose neck vent on the top. The left tank is not leaking and for the time being I am not going to replace it. I am leaning toward the kitfox tanks at 450 a tank. Reason being is it will resemble the left side more than a poly replacement would. I am thinking I might sell the avid in the spring and don't want to pass a problem on to someone but I want it to look close to the original tank. The avid is a B model with upgraded heavy hauler wings. The spars etc have been beefed up to up the MTOW to 1150. The Kitfox site has tanks for the 1-3 but asked for a wing twist. my heavy hauler wings apear to be uncambered but I have no idea what twist I need to tell them. I am assuming that the 1-3 model tank would be what I need but they also have a model 4 tank. I was hoping to just remove the top fabric but with the kitfox replacement I think it will require top and bottom fabric to be stripped???? If you think poly tanks would be a better option I will listen, although I am hearing problems with the gas caps and vent tubes not holding up.  I don't know whether two different gas caps/tanks would keep me from selling it or not but that is a concern. Currently I have one (leaking 15 gallong) and one 7 gallon that has a storage compartment along side it that is not leaking. Resale will be a factor in my tank decision so help me out guys.

Thanks Mark

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Posted (edited)

Mark,  Unless some Avid person, like Jim Chuk "1avidflyer" knows more about this than I do, I think the Kitfox 1-3 tanks would be your best fit.   Measuring wing twist with wings on plane is not as easy as having one sitting on sawhorses, but can be done - First, level the wing at the root end fore and aft with a level across both spars underneath - then move out to end of spars near last rib, and put the level under the front spar - when it shows level, measure from the top of the level up to the rear spar, and that is your twist.  Might be easier with a helper.  Hope this helps,  EDMO

 

Edited by EDMO

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Posted

Doug posted a bunch of pictures a while back of the different profiles of the wings, and the Kitfox 1 - 3 are not exactly the same as the Avid. Maybe I can compare the ribs also and tell what the difference is.   Sloshing may not work, but then again maybe it will.  That is a lot less work and $ than pulling out the tank.  YMMV  JImChuk

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Posted

I think the tanks are close enough to work - maybe not perfect.  If you are going to try sloshing, I recommend CASWELL - One of our members has had a chunk of it sitting in fuel for some time now (years?) and it has not deteriorated.  (Wypaul?)  EDMO

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Posted

you guys are right about the $. I looked into Caswell $79 for a qt which is enough to do 20 gallon tank. I guess I can build a wing rotisery and give it a try. Any ideas about the acetone wash? finding different opinions. AV gas vs acetone prior to treatment. 

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Posted (edited)

you guys are right about the $. I looked into Caswell $79 for a qt which is enough to do 20 gallon tank. I guess I can build a wing rotisery and give it a try. Any ideas about the acetone wash? finding different opinions. AV gas vs acetone prior to treatment. 

Instructions for CASWELL, as best I remember, is to put in a can full of screws and shake, rattle and roll!  Some say acetone?  Don't see how Avgas would help at all.  I don't know.  Instruction on can is usually for metal tanks. 

Two guys shaking is better than rotisery, IMO.  EDMO

Edited by EDMO

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Posted (edited)

I used acetone to rinse out my tanks (new) but I suggest caution, my tanks made some interesting sounds when I use it.

i did have some Caswell epoxy soaking in gas for several years but finally threw it away with no degradation at that time.  It will be a bigger challenge to get the tank completely coated while installed in the wing but quite doable. 

I also used the screws before the acetone.  The acetone may be hard on the wing finish.

Edited by wypaul

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Posted

Have a look at KBS coatings.  They use a different cleaning solution, rinses out with water if my memory is right.  I used it once and it seemed to work ok. Didn't hurt the fabric.   Aluminum tanks that eventually started to leak again.  They do twist and crack though.  Fiberglass is probably more stable.  As far as putting in screws, don't know how that will work though.  Our tanks have baffles in them to keep the top attached to the bottom.  I think the reason for using the screws is to scratch up the rust in a steel tank.  This kit will do a 25 gallon tank.  They also have smaller kits.  JImChuk

https://www.ebay.com/itm/AUTO-FUEL-TANK-SEALER-KIT-KBS-COATINGS-25-GALLON-TANK-GAS-TANK-SEALER-/370582196844?_trksid=p2349526.m4383.l4275.c10

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Posted

When I got my new tanks from Kitfox, I rinsed them with ascetone then with E85 garbage fuel.  I used about a gallon of each PER TANK.  I collected the waste rince and inspected it for any forign matter or discoloration. 

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Posted

Mark -

In our F/G tanks, I would highly recommend using a 2-part phenol novolac epoxy based product for sloshing/coating. I would refer you to the detailed info in this thread: http://www.avidfoxflyers.com/index.php?/topic/738-wing-tank-repair/

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Posted (edited)

All Avid models officially called for 2" wing twist, although for years both Avid and [old] Airdale had repeatedly and quite publicly advised builders that 1-1/2" was fine. I built my Mk-IV and A+ wings with 1-1/2" twist, as did many others, so you really should physically check yours to be sure before deciding which replacement tanks will work best in your Avid. Ie. the Kitfox 1-3 model wing ribs may be darn near the same airfoil as Avid's under camber ribs with a nearly identical chord, under camber etc., but the longer KF1-3 wings use only 1" [edit: 1.75"] of twist per the KF build manual and that twist difference presents some challenges when installing the Denney or Skystar KF3 slip-in wing tanks in your Avid Mk-IV HH wings (I'm not sure if Kitfox Aircraft is currently offering a new E-resistant replacement tank for the old KF 1-3 models).

As Jim noted I did put up a bunch of pics showing Avid HH and Speed rib differences as well as KF 1-3 and 4-7 rib differences on site somewhere. I also did a thread about fitting the Skystar 1-3 wing tanks into my Avid Mk-IV HH wings. Like Ed I'm sloggin through cancer treatment and a bit foggy on the thread names right now but I'll try to look them up and post links for you.

Edited by dholly

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Posted (edited)

Doug,  My mind is probably a lot foggier than yours right now - Neulasta really kicks my butt for about 3 nights - got one more to go this round , but believe my KF1 & 2 wings were built with 1 1/2" twist, but maybe I've been listening to Avid Flyers too much? - Donno about the KF3.  When I put my new tanks in I had to add another capstrip to top of ribs on each side of the tank to clear the edges - High Country or Birddog486 did the same to theirs.  EDMO

Edited by EDMO

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Posted (edited)

Yeah Ed I hear ya, one more week for me. :wacko:

Ok, here's the CORRECT info: Denny produced two 'slip-in' style wing tanks: a black tank for the KF1-3 which used the old under camber rib profile in 1.75" twist wings, and a gray tank for the KF4-1050 and KF4-1200 Riblett laminar flow rib profile in 1" twist wings. Some of the early KF4 tanks were light gray or dark gray, some factory sloshed with Kreem others not. See the attached pics.

Now something of interest... in their current online catalog, Kitfox Aircraft does sell wing tanks for KF1-3 (might be just about the only part they still offer for the older KF) AND they ask you to specify twist when ordering. Kinda makes me wonder if some early KF1-3 builders were opting for a little less twist in their under camber wings just like the Avid builders were. Pretty sure they all used the same factory recommended 1.75" twist. In any case, it might be possible to specify, 2", 1.75" or even 1.50" twist in their new E-resistant slip-in tanks. In every case, the difference in a KF1-3 rib vs. an Avid STOL/HH rib will cause issues when plunking a KF1-3 tank into an Avid STOL/HH wing. I'm still looking for my install pics.

028 (3).JPG

029 (2).JPG

Edited by dholly

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Posted (edited)

Well,  My old tanks, and my new tanks, for KF1-3 were all gray.  ???  EDMO

Edited by EDMO

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Posted (edited)

lol, never seen that, it's a new one on me. Do they have any identifying info or stickers on them? My Skystar sourced KF3 tanks were similar color and raw f/g looking style as sold today, but non E-resistant of course. 

CIMG4420_0001.JPG

Edited by dholly

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Posted

Actually,  My KF1 & 2 tanks were gray - The 4 new KF1-3 tanks were gray - The KF3 tanks are still covered with fabric, so I don't know about them.  EDMO

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Posted

I used acetone to rinse out my tanks (new) but I suggest caution, my tanks made some interesting sounds when I use it.

i did have some Caswell epoxy soaking in gas for several years but finally threw it away with no degradation at that time.  It will be a bigger challenge to get the tank completely coated while installed in the wing but quite doable. 

I also used the screws before the acetone.  The acetone may be hard on the wing finish.

I am surprised that you would use Acetone. Acetone eats fiberglass. I called the guys as Caswell and they told me only use acetone if  your tanks are metal. Otherwise hot water and detergent.  Use drywall screws so the inside gets roughed up. 

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Posted


When you soften it whatever you put on it sticks better.

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Posted

Lot of the Kitfox tanks were treated with Kreem and sometimes it flaked off after many years.  The acetone will dissolve the Kreem.  Of course if you filled the tank with acetone, and left it overnight, it would probably eat through the fiber glass as well, but that is not how it should be done.  As far as the screws in the tank, I'm doubtful that would work very well with the fiberglass tanks with the baffels  in the tanks.  Different with a single space like say a motorcycle tank, where you could dump in a bunch and shake it around to knock off all the rust and such.  JImChuk

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