Sign in to follow this  
Followers 0

Gas tank

31 posts in this topic

Posted

I have finally figured out a course of action for my gas tank. Looked inside it is very clean. I am going to cut the top of the tank out, within 3 inches of the edge. Will be covering entire tank with vinyl ester resin. I will then put top back in place after covering with same compound. Manufacturer guarantees it is completely alchohol resistant. The prep is ver important to the success of the job. Not complicated, just takes time. We are all used to that.

I only have 1 tank. This is what i am proposing for other wing. Removed stitts for recovering and am looking at wing. There is bracing in the bays that I would install a tank in. Can that be safely removed if after installation of tank I cover top and bottom of gas tank bay with .040 aluminum, riveted and epoxied in place. Will have to remove Rib to match other side. I would think the shear strength would be far greater than the bracing. If this will work will make new tank.

New tank will be made with last a foam and vinyl ester resin. Very straight forward to work with and completely alcohol resistant. One of my friends just made one. Very light, stiff as hell and easy to fab in complex shapes. Wall thickness is 1/4 inch so will cut down on volume some but finished product is great.

Comments and suggestions, please

Share this post


Link to post
Share on other sites

Posted (edited)

I looked at vinyl ester resin for coating the inside of my tanks before I built my wings but did not find any info about how good of a bond could be made between vinyl and the polyester.  Do you have some info about that?  I decided to use phenol novolac epoxy to coat the inside of the tanks because I was able to find plenty on information on that.  It would be good to know about vinyl ester resin

 

For the new tank are you planning to glue it to the spar like the original tanks?  If so I don't think you need to worry about removing the bracing.

 

For the new tank I would suggest using a couple of coats of neat VER after the layup to be sure that you don't end up with pin holes leaks, I fought those on my Q-2 tanks, and of course remember to test it before installing.

 

Maybe Ed would know about bonding VER to Polyester???

Edited by Paul S
1 person likes this

Share this post


Link to post
Share on other sites

Posted

My friend did roll 2 coats of VER over the the inside of the last a foam after building the tank. I am going to coat the VER with the novalk epoxy after it dries. Kind of nervous about the epoxy by it self, the VER bonds to the glass well. The epoxy will have a fresh surface to bond to that way. The VER grabs the last a foam unbelievably well. We made some floor boards for my 180 and they were light tough and completely resistant to everything.

Share this post


Link to post
Share on other sites

Posted

Sounds like that should work well, let us know how it goes.

Share this post


Link to post
Share on other sites

Posted (edited)

Let me know how it goes too - I have only used two types of epoxy, and not being a chemist, don't have a clue about the ingredients - never even read them - The best I have heard is Caswell or something like that for sloshing....I am now a student, quietly listening and learning.

I am wondering about carbon fibre, or Kevlar in the layups for tanks, instead of just fiberglas?

The builder's manual for both Kitfox and Avids show how to relocate the drag tubes when installing a wing tank - both for the 6 gal and the 12 gal, I think. Please refer to the manuals - that is important, IMO. I eliminated one tube and moved the end of one when I installed TWO 12 gal tanks in each wing on mine, and the manual does not show 2 tanks, but I believe mine is strongly braced by the tanks.

EDMO

Edited by Ed In Missouri

Share this post


Link to post
Share on other sites

Posted

Some problem with carbon fiber wicking petroleum if not sealed properly, that said it is being done. I don't feel that confident in my abilities. I loked over a carbon cub and it seemed everything was carbon fiber. Guess that is how you get $180,000 in one, nice but a few pay grades above me.

Share this post


Link to post
Share on other sites

Posted (edited)

Some problem with carbon fiber wicking petroleum if not sealed properly, that said it is being done. I don't feel that confident in my abilities. I loked over a carbon cub and it seemed everything was carbon fiber. Guess that is how you get $180,000 in one, nice but a few pay grades above me.

A LOT of pay grades above me too!

What I was referring to, was sandwiching CF or Kevlar between the layers of Fiberglas - Never tried this, and don't know squat about it - don't even know much about why to do it either - They never taught this at work or at AMT college. All I know is that CF is stiff and strong when cured, and Kevlar is tough and strong?....Any Epoxy and Laminate Engineers on here?

EDMO

Edited by Ed In Missouri

Share this post


Link to post
Share on other sites

Posted

I built the cowl for my Q-2 using a Kevlar sandwich that you are suggesting Ed.  The one bad thing about Kevlar is that if you try to sand into it you get the "Kevlar fuzzies" which are hard to deal with.  The fibers stand up and resist being tamed again without covering them with a buildup of glass or micro.  This probably is not an issue for a tank where cosmetics is not that important.  Oh and it does take special shears to cut Kevlar.  All that said I am happy with the cowl but there was a few times I questioned my choice of the Kevlar sandwich when making changes to the cowl.

Share this post


Link to post
Share on other sites

Posted (edited)

I built the cowl for my Q-2 using a Kevlar sandwich that you are suggesting Ed.  The one bad thing about Kevlar is that if you try to sand into it you get the "Kevlar fuzzies" which are hard to deal with.  The fibers stand up and resist being tamed again without covering them with a buildup of glass or micro.  This probably is not an issue for a tank where cosmetics is not that important.  Oh and it does take special shears to cut Kevlar.  All that said I am happy with the cowl but there was a few times I questioned my choice of the Kevlar sandwich when making changes to the cowl.

Thanks Paul,

I thought I had read that the Kevlar was hard to cut - didn't know about sanding.

I worked with fiberglas at Chrysler for nearly 30 years making fixtures - They used Ren 9410, if I remember right - don't have a clue as to what was in it - didn't mind using it, until time to cut and grind, then it was an itch! I used West System epoxy on a boat after retiring - Didn't bother to read that either. Don't know what we used in school for vacuum bagging - just know it was epoxy and there was no catalyst involved in any that I used. Now everyone knows exactly how little I know about it. :lol: I still have 2 books from school on composites - Maybe should read them!

I still want to learn about Carbon Fiber someday - Hard to believe "stronger than steel"? :huh:

If I have any leaks, I think I will try the Caswell sloshing - sounds good and simple - I like simple!

EDMO

Edited by Ed In Missouri

Share this post


Link to post
Share on other sites

Posted

Hi!

 

What problem are you trying to solve? I have some experience repairing these tanks if they leak. If they are already installed in the plane it is probably best to go in from the bottom as opposed to top. If constructed to plan there is plywood on the top but there is easy access to the bottoms.

 

IMHO, there is no good way to make them ethanol proof if that is your goal. Evenually any coating you apply will be problematic and eventually delaminate if you use ethanol. It is horrible stuff.

 

Chris

Share this post


Link to post
Share on other sites

Posted

Chris, I was informed by the tech people that the VER was completely impervious to alchohol. Might be wrong, I frequently am. Because of how I have to close the tank I pretty much have to go in from the top. My tank is all fiberglass

Share this post


Link to post
Share on other sites

Posted

Should

Share this post


Link to post
Share on other sites

Posted

Should I make a liner out of the last a foam for the tank? It would not be difficult.

Share this post


Link to post
Share on other sites

Posted

I coated the inside of my tanks as well with a vinyl ester resin.

 

I dont think I'll take the chance using ethanol because I dont trust it to be ethanol resistant but I was worried about them having leaks so I went this route.

 

I used a multi tool to cut the tops off and made a 2" wide lip that I attached to the inside of the tank. Then I was able to glass the tops back on.

post-379-0-71440000-1375828522_thumb.jpg

post-379-0-66721900-1375828532_thumb.jpg

Share this post


Link to post
Share on other sites

Posted

The reason I do not believe it is a good idea to try and think in terms of ethanol proofing a non-ethanol proof tank is that ethanol will find a spot wher there is no coating and make its way between the coating and the fiberglass. No matter how good a job you do coating, there are still the tank penetrations where you probably cannot maintain the coating integerity. 

 

I did a bunch of experiments with various coating compounds like Buna N rubber, polysulfide sealer, structural epoxy and phenolnovolac epoxy.

 

I cut the holes in my tanks and used the cutouts to make test pieces. I first put a piece of the tank material in 10% ethanol. After a day or so the fiberglass surface softened. It didn't fall apart or anything, but with my fingernail I could put a dent in the glass. Once removed from the ethanol and left to sit for another couple of days, the fiberglass tank material hardened back up and remained seemed structurally sound. That was good news to me, but I knew deep insid that if the tank was continually exposed to ethanol, eventually it would deterioriate. 

 

So I cut the fiberglass of my fuel tank material I had removed into a bunch of test pieces, sanded and cleaned them and put silver dollar sized coatings of each of the coating materials on each piece and exposed all of the samples to different fuels and additives. I tried all the different coatings in Avgas, 10% ethanol, non-ethanol regular autogas, seafoam fuel additive and Marvel mystery oil.

 

All of the test samples survived the Avgas and Marvel mystery oil without any deterioriation of the coating or substrate tank material. All of the samples survived the regular autogas except the Buna N rubber which deterioriated in the ethanol and lost some color but did not deterioriate in the non ethanol gas and seafom. The structural epoxy, polysulfid sealer, and phenonovalac epoxy survived the everything including ethanol just fine, but the exposed fiberglass softened and the ethanol worked its way under all of the coatings and weakened the bond coating so I could easily peel it up as far as it had managed to work its way under the coating.

 

So, there you have it. Those were real experiments I actually performed no BS speculation. Just the facts. If you are lucky enough to have vinylester tanks (or which ever resin is not ethanol sensitive), you are lucky indeed. If you have polyester (or what ever one is sensitive) like the tanks in my Magnum i do not think it is wise to try and coat them to make them ethanol proof. I reasoned it might last a long time, but no matter how I sliced it, it was time bomb. I ended up fixing the leaks with structural epoxy and never used ethanol. I think that is the only guarantee.

 

I really liked the phenonovalac epoxy because it is impervious to almost anything, but it was very brittle. Bend it just a bit and it would snap. The structural epoxy was much more flexible when cured, and I only plugged the leaks, I did not coat the tanks. I would have used fiberglass resin if I had known which kind of resin my tanks were made of, but I didn't, and I did not want to take a chance with some incompatibility that I may not know about. The structural epoxy sticks like mad to everything, and I have no worries about it and have had no problems with my repairs.

 

But I won't go near ethanol knowing what I know now.

Share this post


Link to post
Share on other sites

Posted

Ok, so I guess I coat my current tank with the VER and use av gas only in it, and put a 100ll only sticker on it. The new tank I am making out of the last a foam I will use the auto gas in. I really don't care about the difference in price. It is 90 miles to the nearest av gas and that is in the Las Vegas tca, not the most experimental friendly place on the planet. I always keep a drum of av gas in the hangar for the Cherokee when I am low but don't want to use it unless I have to. Burn half a day to fill the drum up so try to keep to a minimum. My engine builder asked me to keep my av gas burn to a minimum, said it increased maintenance schedule significantly.

Just can't seem to catch a break. Oh well every shortcut I take has always been a mistake.

Share this post


Link to post
Share on other sites

Posted

Chris,

Thanks for the report with no BS - I only want to plug any leaks I might find - Not make tanks moonshine proof - You failed to say what "structural adhesive" you used - Would that be the Hysol 9460 that we are using to glue the ribs to the spars - and most everything else on my build?

BTW: Amie is trying to get some nose-gear questions answered - She may want to contact you too.

EDMO

Share this post


Link to post
Share on other sites

Posted

I re-read my post and it was confusing. What I meant to say is that you wil be fine with any coating I tested with Avgas or autogas without alcohol and with marvel mystery oil additive if you like that particular additive.

 

I did notice some discoloration of the Buna N rubber compound with regular auto gas and in the seafoam additive, but no loss of integerity of the coating.

 

The Buna N rubber was definitely the nicest coating to apply and use, but it deterioriated quickly in ethanol, so I ruled it out in case I accidently put ethanol in without knowing it.

 

The epoxy's I tested and the polysulfide sealer were impervious to the alcohol, but in my case the fiberglass wasn't.

 

The structural epoxy I tested was Hysol 9430 I think. It is a clear two part. Got it from aircraft spruce, but couldn't find it on the site just now. I could have the number wrong I'm not at home where I can look.

 

Hope that is more clear. It's always harder to write something down so it makes sense than to just talk about it! :wacko: 

 

not a nose gear expert, but have some experience with various nosewheel configurations.

Share this post


Link to post
Share on other sites

Posted (edited)

Thanks Chris,

I believe Hysol 9430 is the gray stuff sold by Spruce - I had thought about trying it, since it is about $60 a quart kit, instead of the 9460 that Kitfox sells for $100 a pop, which I have just ordered AGAIN to remodel my wing ribs and do other things. Guess I could have used T-88 since my ribs are glued with that, but needed "Other things" glued too.

None of us are "nose wheel experts" - Those guys work for Boeing and other big companies - we just "Xperiment" and hope for the best!

EDMO

Edited by Ed In Missouri

Share this post


Link to post
Share on other sites

Posted

I checked and it was Hysol 9430 that I did the experiment with and used on my tanks. I thought of it as clear, but it is actually called off white.

Share this post


Link to post
Share on other sites

Posted

I checked and it was Hysol 9430 that I did the experiment with and used on my tanks. I thought of it as clear, but it is actually called off white.

I am going to check and maybe experiment with the 9460 to see if gas/alcohol will affect it - I have the books from Loctite - need to read them - I had a Loctite rep give a presentation while I was supervising the Coast Guard mechanics, but if I call now with a question, no one can give me a straight answer.

Thanks again,

EDMO

1 person likes this

Share this post


Link to post
Share on other sites

Posted

My starboard tank leaks and has caused the fabric to come unglued. How difficult is it to pull the tank and reseal it, then fix the hole in the fabric?

Share this post


Link to post
Share on other sites

Posted

Welcome to the forum DirtriderDave! Several different options out there to fix your tanks. Most people end up replacing the tank or putting a new smaller tank inside the old one. Calling Bandit.....

Share this post


Link to post
Share on other sites

Posted

Installed 2 plastic tanks inside the old fiberglass tanks. Each tank holds 5.2 gallons.

post-56-0-25306900-1376528697_thumb.jpg

post-56-0-51027200-1376528734_thumb.jpg

post-56-0-79005800-1376528754_thumb.jpg

Share this post


Link to post
Share on other sites

Posted

Installed 2 plastic tanks inside the old fiberglass tanks. Each tank holds 5.2 gallons.

At what cost, and from who?

I think Chris has the best idea - about $2 worth of epoxy where the leaks are.

EDMO

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!


Register a new account

Sign in

Already have an account? Sign in here.


Sign In Now
Sign in to follow this  
Followers 0