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View Full Version : Fabric work, envelope Breathing mast.



160STol
02-18-2006, 08:22 PM
I am getting ready to do the fabric work on my exp Pa 20. I have the Ceconite Manual which I found to be a waste of $10.00 I also have the EAA DVD which is a little more helpful. I an getting ready to prime the fuselage with expoxy primer. When installing the envelope, which came with no installation paperwork Do you cement it at the longerons, how about the razor back spine, the formers? I can see cementing it at the door sills and tail post, front gear section. But if you do the longerons, do you hang the fabric first to align the seams? Do you reach up in and apply cement or dab it thru ? Where do you apply the cement in the mid sections where it is harder to reach for a better way of describing it. Only the longerons, plus the door sills, tail post, gear box area. ?
On the breathing mast, I was think the Hobbyair, But my auto parts/ paint dealer has a Willson system that takes air from your air compressor and filters it, and it feeds the air to a face mask. You must make sure your compressor is getting it's air from a outside source. Any thoughts ? Willson mask is around $100.00 I have a good filter system already. I am not sure, but I think you use another air hose to feed the mask.

Steve Pierce
02-18-2006, 08:30 PM
Who did you get your envelope from. Get a Poly Fiber manual for some hints on putting on the fabric. Jim and Dondi Miller make an open bottom envelope. You cover the belly and then glue the envelope to the two bottom longerons. Shrink the seam down the spine first and then alternate either side to keep from getting a crooked seam. You can pre-glue the spine and then hit with your iron at about 230 dgrees to help hold the seam straight.

I get fresh air from my Graco HVLP but the Willson sounds like a good deal that will work just as well. I know several shops that use a system like you describe.

bob turner
02-19-2006, 01:31 AM
I always liked the blanket method. A double-sewn seam seems to make the rudder just right, and save material. The rest of the airplane is thus free of unsightly seams, and the wide fabric is wide enough for a legal overlap at the trailing edge, and a butt seam on the L.E. can be covered with an 8" strip, leaving two legal seams in anybody's manual. Don't forget to remove the selvage edges - you'll never hide them!

wilbur
02-19-2006, 03:06 PM
I have a friend that uses the hobby air pump, with a bullard air fed hood. I use the bullard hood in industrial applications and it works well. I'd be cautious about trying to use a two stage shop compressor for air unless I tested it before buying. My 7 1/2 hp quincy 2 stage won't keep up with the volume I like for my hoods. (although I may have the hood air cranked up more than I need)

Steve, The Graco HVLP pump sounds like a good idea. Does it produce enough volume for the gun and breathing air at the same time?

Wilbur

Steve Pierce
02-19-2006, 03:41 PM
Yes, I don't remember the model number of my Graco but it will run 2 guns. I just put a "Y" in the line with another hose for my hood.

Ruidoso Ron
02-19-2006, 04:15 PM
Steve, didn't Gilbert cover the top of his Clipper fuselage with one piece?

Steve Pierce
02-19-2006, 10:05 PM
He covered each side with a seperate piece of fabric glued to the center stringer like Piper did originally. No envelope.

jay heil
02-20-2006, 05:38 PM
steve ive aalways kind of wondered how your supposed to do this ok so you glue one side on the center stringer and then you have to glue the next side onto the first side's fabric with an overlap of 1 inch[poly fiber, 2 inch airtech] ok so that seam is now 1 inch off to the side or 2 inches if using airtech and then you cover it with a reinforcing tape ok to make that reinforcing tape centered on the spine of the fusalage you would need a 4inch tape on poly fiber and then on airtech you would need a 6 inch tape is that how you did it?
and as long as im asking questions how can you glue to the stringer anyway ? here is a couple quotes from the poly fiber manual the fabric can only be joined with a cemented seam "over structure" "structure" in a fusalage is defined as longerons or cross tubes only formers and stringers dont count" it goes on to say [they are doing a J3] notice the 3 wooden stringers on the top of the fusalage aft of the cabin ,you cant create a cemented seam over these stringers ok i know the center stringer on a clipper is aluminum but still even though piper glued cotton to this stringer or former im reading you cant be glueing polyfiber or airtech or really anything to this stringer am i reading this wrong somehow???

Steve Pierce
02-20-2006, 09:23 PM
Clipper stringers were originally aluminum. Look at Dwg 11988 on the Short Wing CD. Doesn't exactly follow the Poly Fiber manual but it does the manufacturers data. Tested a 2" glue joint and the fabric failed before the glue joint did. Used a 2" tape down the center stringer. If you want to follow the Poly Fiber Manual I would get Jim and Dowdy Miller sew an envelope. The 2 clipper frames I have in the shop now have a 3/8" center stringer/longeron welded in.

jay heil
02-21-2006, 04:14 PM
ok what im getting at here is if you put a 2 inch tape down the center of the stringer that means you have 1 inch on each side of it so there fore if you had a 2 inch overlap of the fabric for the glue joint you cant possibly have the reinforcing tape covering the seam !! even if you had a 1 inch overlap its not covering the seam but if you did airtech which i believe you need a 2 inch overlap so if you put a 2 inch tape on it then your tape has to be centered 2 inches to the side of the stringer[if its centered on the seam] and thats not even on the stringer look im not trying to cause any trouble just trying to figure out how its to be done

bob turner
02-21-2006, 05:00 PM
Jay - it sure sounds like you are right. However, the aircraft was certified with 2" tapes centered on the longerons/stringers, and that's the way about 99% of rebuilds are done - at least until now. I have never seen a fabric failure at a longeron or stringer that was due to normal use - but sure have seen a lot of finish cracks, regardless of the taping philosophy. Buy lots of 4" tape, and keep your feds happy - or do like everybody else and make it look like the factory did - really pretty.

I always cover the sides first, with one piece, then the turtleback with two pieces, then the bottom with one piece. To be legal, you pretty much have to do some stitching back by the rudder, but cover the joint with 4" tape, and shrink the tape to totally hide the stitches. Then sand carefully while you put silver on, and you'll never see the pinked edges. Just my opinion.

Steve Pierce
02-21-2006, 08:35 PM
Covered the bottom first. then the fabric went over the center stringer to the bottom longeron. Then a 1" overlap over the previous piece of fabric on the center stringer to the other bottom longeron. 2" tape glued over the center stringer. You can't see the seam.

jay heil
02-21-2006, 08:58 PM
ok steve forgive me im really not trying to piss you off here but if you overlapped it 1 inch that seam weather you can see it or not is 1 inch on 1 side or the other [depending on which side you did first ] of the center stringer ok now if you put a 2 inch tape on it isnt 1 edge of the 2 inch tape right exactly on top of the seam ?

Steve Pierce
02-21-2006, 09:30 PM
Drew a straight line on the first piece of fabric 1" from the center with a compass. Glued the other side to that line and the edge of the tape over the edge of the overlap. The Piper drawing I listed above shows it.