Epoxy primer inside spars

[Meyer]

All,

I am planning to epoxy primer the inside of the wing spars. How much does it take to do that?

I saw posts about someone using an airbrush gun on a long piece of PVC. Someone else just put a tennis ball in to cap each end, and sloshed primer around inside. I will do the tennis ball method I think. Any idea how much I should order? I was just going to order the epoxy primer from kitfox.

Thanks

Scott

[Esser]

I think about a quart per wing should do it if I remember correctly. You want extra so you know you covered everything. I, too, did the tennis ball method.

[jmodguy]

Eastwood.com sells a wand with a 360 degree spray head for spraying inside automotive panels. Check it out

[jiott]

I'm pretty sure I did all four spars with less than a pint, using tennis ball method. Pour in plenty to get a good slosh, then drain it out and reuse on the next spar.

[jrevens]

I did the tennis ball thing. Cover the tennis balls with Saran Wrap.

[aviator79]

I should have done that!

I made a little mess because the primer soaked through the fuzz on the tennis ball. I think I used a quart per two spars - I could have done all four, but I only worked on one wing at a time. Most of what you put in comes back out, but as Josh said, you need plenty of excess to make sure you get a good slosh.

[Floog]

Priming the inside of the spars is a waste of time, money. Adds weight and makes a mess too.

[aviator79]

If anyone is qualified to say this, it's you. But you didn't have to completely submerge them just to make your point. ;)

[efwd]

Wow, quite a statement. I notice the "inside" of the spar is a waste but no mention of the outside. Living around the ocean, I wouldn't want to see what the inside or the outside of the spar would look like a few years from now if it weren't primed.

[SSFoxBuilder]

Has anybody considered CorrosionX or Boeshield T-9 as a spar corrosion preventative? I was planning on this at some point.

Both are usually applied as a mist and will "set up" a nice protective coating, probably more than sufficient for most Kitfox users...

[jiott]

I primed the inside, and outside too, of my spars because I figured someday I may want to put floats on it. Kitfox factory recommended priming the inside for float application, especially near salt water.

[Dave S]

I would promote the idea that doing something (paint, alodine, corrosion proofing/sealer), with the inside of the spars (as well as the outside like where many builders epoxy prime them) is important for long term service given that the most susceptible part of the assembly is precisely where little can be done with it inspection or repair wise. Where the insert contacts the inside of the spar tube is the most likely place for corrosion to start. I regard corrosion prevention/corrosion proofing to be critical in the long run - if a plane will be around for many years. Corrosion in lap areas in old aluminum airplanes is not unheard of - usually the little raised "donuts" around a rivet holding aluminum skin to an aluminum rib, or spar capstrips, or skin overlaps or similar lap areas is where it ends up.

Corrosion will eventually turn all aluminum into bauxite, from whence it came - some things speed up the process like electrolytes & moisture. Some things retard the process like sealing the surface to keep oxygen, moisture and electrolytes away from the surface (at least till it gets a scratch).

[colospace]

Dustin, I used Corrosion-X inside my spars. Living in the low humidity of Colorado, I'm thinking that is sufficient although I will probably renew it at each condition inspection. I also soaked the inside of my lift struts with linseed oil early on.

[David47]

So just a bit of added info. Unless you remove the oxide layer on the inside (or outside) of the spars before you paint, the adhesion of the paint to the surface is debatable. Alumiprep or something similar should be used before you apply the primer, as this gets rid of the oxide layer and any oils or other contaminants from the extrusion process. I used alumiprep and then alodined the spar internals using the tennis ball method. The alodine has enough chromium in it to give corrosion protection against most nasties, such as salts etc. FWIW.

[Delta Whisky]

colospace - I'm liking the idea of using corrosion X or Boe shield - how did you apply it? Special spray rig? Tennis ball?

[Floog]

Here's another strong statement from someone qualified only in offering an unsolicited opinion: The spars will last a lifetime without any additional protection inside or outside, ocean environment or whatever. I guarantee it!

[ken nougaret]

With this and your previous post, i have to ask, is this an inside joke that I am not aware of?

[colospace]

colospace - I'm liking the idea of using corrosion X or Boe shield - how did you apply?...
I taped the outer ends closed and sprayed what seemed to be a healthy dose of Corrosion-X into the inboard ends. I put rags beneath the outer ends to catch excess that eventually dripped out. The Corrosion-X is supposed to create something of a fog that coats all surfaces.

[Meyer]

So just a bit of added info. Unless you remove the oxide layer on the inside (or outside) of the spars before you paint, the adhesion of the paint to the surface is debatable. Alumiprep or something similar should be used before you apply the primer, as this gets rid of the oxide layer and any oils or other contaminants from the extrusion process. I used alumiprep and then alodined the spar internals using the tennis ball method. The alodine has enough chromium in it to give corrosion protection against most nasties, such as salts etc. FWIW.

You did alumiprep first then alodine and that was all? No primer?

Thanks all for the replies.

Scott

[bbs428]

I prepped the inside spars with white vinegar slosh for about 5-10 min. I used gorilla tape on the ends.
Held the wing above my head and rocked it all about. Kinda like the "truffle shuffle" but you don't giggle your fat - just the wing.
Good workout... not. :p Best to bribe a family member to do it. Lol.
A fresh water rinse, a hair drier dry job and then an Alodine slosh for 5-10 min.
Finished with another slosh of fresh water. Done.

[David47]

You did alumiprep first then alodine and that was all? No primer?

Thanks all for the replies.

Scott

Yep, that was it. If you look up the properties of alodine you'll find that it has corrosion inhibiting properties as well as acting as a surface preparation prior to painting. It's the chromium content in the alodine that does the trick. The gold standard for corrosion protection in severe environments would be alumiprep (or similar), alodine and then epoxy primer (2 part). What bbs428 has done will have a similar effect - the vinegar will help reduce some/most of the oxidation layer. Alodine 1200/1201 is a pretty good inhibitor, and it'll also maintain your electrical conductivity. I decided to go this way because it's way simpler than priming. As bbs428 says, you can slosh and wash (water rinse) .... and you'll have good protection .....

[FoxTrotter]

Are you guys doing this spar prep on quick-build wings (which is what I have)? Not clear to me how you're "holding the spar over your head and sloshing" with an assembled quick-build wing, nor how you're treating the exterior of the spars with all the ribs etc already in place.
Thanks - Michael

[efwd]

Youll need to either spray or apply with a brush when it comes to the exterior surfaces. As for the slosh, I propped the quick built wing on a sawhorse. I put tennis balls into the spars at the floor. I poured the primer in at the end propped up on the sawhorse. quickly put the tennis balls into the ends and ran to the other end, picked it up and tilted back and forth. I used new, fuzzy tennis balls. Leaked pretty good. I think some have stopped the leaks by putting saran wrap over the ball first.

[airlina]

with finished wings on saw horses,plug the spar ends with afformentioned tennis balls , dump epoxy primer into open ends and plug with two more tennis balls, then lift one end at a time with the other end on the saw horse and slosh. go to the other end of wing and do this again. flip the wing over and repeat, inside done and can be done solo. for my exterior spar protection, i used a small hobby type spray gun and shot epoxy primer to the spars around all the wood parts. used the same rig to varnish all the wood parts at a later time. the small hobby type gun can be used in tight quarters ,accurately with little overspray. Bruce N199CL

[FoxTrotter]

Thanks, guys. Did you go straight to the epoxy primer, or was there some kind of preceding prep, eg Alodine or equivalent?

[efwd]

Alcohol cleaned, whiped down with scotch brite ( no circumferential rubbing ), alcohol cleaned again then straight to spraying Primer as the previous post describes.

[FoxTrotter]

Dustin, I used Corrosion-X inside my spars. Living in the low humidity of Colorado, I'm thinking that is sufficient although I will probably renew it at each condition inspection. I also soaked the inside of my lift struts with linseed oil early on.

Colospace, how did you spray the inside of the spars? Did you simply use a spray can, spraying at one end and letting it drain to the other end, or did you use some kind of special long wand? How many ounces did it take to convincingly cover the entire internal length?
Thanks
Michael

[efwd]

Ken added a Pic of his spray gun he used back on page 10 of the Builder hints and tips thread. I think post #123

[colospace]

Michael, I did it while the wings were folded. Wings pretty level, but tips slightly low. I put tape over the outboard ends of the spars and just sprayed liberally from the inboard ends. The stuff is supposed to diffuse in the air and coat all the surfaces in a volume. I left them closed up and noticed a couple of weeks later that excess was dripping out the ends past the tape that was by then a little loose. Don't know how much I used, but the can still feels pretty full.

[FoxTrotter]

You did both wings with one 16-oz can of CorrosionX? Did you use the standard, the HD, or the aerospace?

Did you epoxy primer the outsides of the spars?

Thanks
Michael

[colospace]

I'll have to get to the hangar to see specifically what I used. I did not epoxy as I was trying to avoid painting in my attached garage and I don't expect to be spending a lot of time at the beach. :cool:

[FoxTrotter]

Thanks for checking. Meanwhile: did you do anything for the outside of the spars, or just leave them alone?
- Michael

[colospace]

Left as delivered.

[Meyer]

I primered mine with epoxy primer with a brush. Aviator79 did the same I believe.

Some primered the inside by inserting a tennis ball in one side (press fit), loading primer, then ball in other end and then rotate wing.

[109JB]

So this is a timely discussion for me. I will be starting my rebuild of a Kitfox 4 that I intend to someday put on amphibious floats. Although I live in Illinois where corrosion isn't as great of a concern, I want to do what I can because my retirement plans include going to coastal areas and splashing around. Given that the wings are already assembled and in good shape, what is the consensus regarding corrosion protection I can use that would be effective without having to take things apart on the wings? Is there something that can "creep" into the joints?

[bbs428]

I just Alodined them inside and out. Light weight and a somewhat easy application.

A two part epoxy coating would be the gold standard in an harsh environment, just heavier.

[FoxTrotter]

I'll have to get to the hangar to see specifically what I used. I did not epoxy as I was trying to avoid painting in my attached garage and I don't expect to be spending a lot of time at the beach. :cool:

Gary, were you able to find out which product you used and how much you needed?
Thanks
- Michael