Wing Sealing

T

tone175

New member
The Service Letter (87a) calls out EC1375 or EC1239. The mil qualification (8802f) is a good start but does anyone know the part number sealer that the factory is using?

Additionally, I have read somewhere that the factory dipped the wings in a preservative solution. Anyone know what that preservative that might be? I noticed that a wood framed sports car builder also dipped their wood frame into a preservative solution.

http://www.youtube.com/watch?v=MLS7p0fGhiM

Regards,
Tony

Rhunter wrote:Bellanca Engineering Report BER 838 addresses spar butt checking and cracking. I had some checking in my spars but all were within limits. I don't have the BER handy right now but I know it allows aft spars to be cracked out to the second bolt hole in the areas between the hinge straps. The forward spar may not have any cracks in the area between the lower hinge straps. I think it may allow a crack out to the first bolt hole in the area between the upper hinge straps on the forward spar but check the BER- I can't remember that part for certain. BER 838 can be obtained from Alexandria Aircraft and applies to all Cruisair, Cruisemaster, and Viking series aircraft. Alexandria says to check the depth of the cracks with a piece of .020" safety wire. I went one better and used a tiny, extremely thin blade of Buffalo Grass that grows at my airport. My deepest crack was 1 1/16", which is well within limits. The BER says to pack the cracks with an approved, waterproof glue, which would be Resorcinol. After that the BER says to seal the spar butts with a type of 3M sealant that is apparently no longer available. I think it was EC-760 or something like that. The sealant that Alexandria uses is of a type conforming to MIL-PRF-8802F. The same aerospace sealant used to seal integral fuel cells and windows on pressurized aircraft. It works well but it is opaque and I wanted to be able to see my spar butts for future inspection so I just coated them really well with three coats of full-strength Stits Epoxy Varnish. They survived this past summer without any cracks and this is South Texas! I don't have them installed yet so I get a good look at them every day. Oh, and the wings can get really heavy if the gear are installed! With gear removed two people can easily handle one wing.
 
I don't have any idea what they used originally, but as a cabinetmaker, I used to cut and dry my own wood with a sawmill. When freshly cut, I used a coating called PEG to coat the ends of the boards so they wouldn't dry too fast and create end checking. I can't see why that product wouldn't work as good as anything else. Good luck.

Michael
 
Michael, this PEG is an interesting product. From what I gather polyethylene glycol is more for high moisture content green wood. I would imagine that the factory would receive the spruce dried and stabilized. But who knows?
Regards,
Tony
 
http://www.morgancars-usa.com/roadandtrackone.html
According to this article, it looks like they use Cuprinol. I have never heard of this product and it raises the question. What did Bellanca use when they treated the wings?
Regards,
Tony
 
Believe it or not, they used a product called "Bellanca Sealer." They did and I still have a partial gallon of it in a tin from Bellanca. It hasn't been available for years. It has the color and consistancy of diesel fuel. It is more of a protectant than sealer. Randolph made a copper based wood preservative until the EPA made them quit. You can still get a wood preservative that has copper in it at Home Depot. The copper prevents fungus growth. This is what Cuprinol is.
After preserving new or refinished wood, I would give a couple coats of Stitts epoxy varnish, as directed. If you are covering Bellanca wings, FOLLOW THE STITTS MANUAL on this topic.
Dan
 
Thanks, Dan. It looks like the older preservative was most likely a special mixture of chromated copper arsenate-CCA. The copper is the primary fungicide and because some fungi are resistant to copper they add arsenate as a secondary fungicide/pesticide and the chromium is used primarily a stabilizer. I was disappointed to hear about the removal of MSMA from the shelves at Home Depot. It also contains arsenic just like CCA. CCA is still allowed in industrial settings, but unavailable in the retail environment. I like Stitts epoxy varnish it is good stuff.
Regards,
Tony
 
I have a friend with a mass spectrometer.. and if I had a small sample of the bellanca sealer.. say 10 cc ( two teaspoons full) he could give us a chemical anaylisis of the stuff.
One problem with many of the wood preservatives one can ( or could :? ) buy is that they were often heavily petroleum based, and not too conducive to good glue bonding :roll.
Most any of the "heavy" metals are good fungicides : copper , arsenic, zinc, lead, silver, and gold for those of you with new planes.
What promotes rot, and fungus is moisture and dirt. Even simple varnish does a good job of keeping these things out of cracks and crevices... IN THE ABSENSE OF SUNLIGHT. sunlight will screw up varnish faster than rabbits find "friends".
Of course any rigid coating ( varnish epoxy or not ) is subject to cracking due to flexing, and changes in moisture ( which gets in through the cracks... round and round we go).
I had a sailboat made in the 1930's of douglas fir. Every place one piece of wood lapped over another the builder painted a bit of white lead paint. 60 years later the boat was sounder and stronger than the day it was built. Moral of that sidebar being the key to longevity in wooden structures is to keep them CLEAN..and Dry as possible. Places like our wheel wells need to be given special attention to keep moisture and dirt from working thier way into crevices...and keeping the atmosphere the bird lives in as dry as possible. When you live in the midwest or south... you're stuck with the humidity, but .you can seal out the dirt. Asking how can I get this aprt later, or glue to this later has to be part of the equation when you chose stuff to use on your plane. The law of unintended consequences being what it is... :oops: I'd ask the guy who has repaired a wing that's been given the West System treatment before I plunged in. I read somewhere ( there's an authoritative source for you ! ) that bellanca used a coat of good old fashoned varnish under the cotton wind covering. anybody whose torn of original wing coating to recover.. feel free to comment on that possibly eroneous bit of "info".

BTW how hard is it to be fly by night marine coating company or some such.. and buy whatever "industrial" product you want. Not very.
 
You must log in or register to reply here.
Back
Top