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PostPosted: Tue Apr 12, 2005 11:03 pm
by Shannon
Lately I've been asked a few questions about fabric covering. Since I've done a little, read a little, and been told a little I'll start a new topic on the subject. To get started here's a pic of a completely fabric covered Lazair. Looks great Huh ! There are some things to consider with fabric. More later....

PostPosted: Thu Apr 14, 2005 10:44 am
by Shannon
The first thing to consider is the cost. No matter what type of Fabric covering system you use (Stits Poly-Fiber, Hipec, Cenconite. Ect..) the costs of fabric materials, supplies, coatings, and paint will add up. Do some in-depth total cost analysis before you get started. A fabric covering job can cost substantially more than Tedlar, Mylar, ect.

PostPosted: Thu Apr 14, 2005 11:00 am
by Shannon
Fabric covering requires a "top coat" finish usually using automobile grade paint. The hardeners, reducers, primers, clear coats, paint equipment and supplies can be very expensive in total. Do your homework and tally all the costs. Lastly you must know how to mix/apply paint as well as have a place to do it.

PostPosted: Thu Apr 14, 2005 11:36 am
by jb88ci
Good post. While researching how to cover my lazairs with fabric without adding substantial weight or significant cost. I also took into consideration the documents i found at these links....

http://www.ultralightnews.com/features/paintinguls.htm

http://www.ultralightnews.com/features/ ... arrier.htm

http://www.questiongravity.com/airbike/latex1.htm

I also managed to download a copy of Dave Edwards e-book.

I've done a practice panel and have covered the tails...next is teh wings...

PostPosted: Thu Apr 14, 2005 11:59 am
by jb88ci
here's an adapted version of the cover and paint book.... B)

PostPosted: Thu Apr 14, 2005 1:44 pm
by Shannon
Excellent. Any additional material is welcome. Here's a little information archived from an old Lazair Newsletter that is a slight variation of the information provided in your links. Good.... obviously however It's up to the individual to decide how best to do the job. I personally didn't use latex paint as my weave sealer and UV barrier. Others claim success however using this method.

Before going with fabric is there may be few structural considerations to think about. Keep in mind I've never covered wings in fabric so I can't render any specific opinion on exactly what needs to be done. What I can do however is add some of the opinions of others whom have done the job. There are some very important things to consider.


More later....

PostPosted: Thu Apr 14, 2005 4:42 pm
by Shannon
According to some there are some weaknesses that show up in the wings when covering with fabric. Evidently the root rib as well as the trailing edge are a little deficient in strength to withstand the "pull" of shrunk fabric. Accordingly it has been advised that the root rib as well as the trailing undergo some reinforcement. I personally can tell you that 1.7oz Poly-Fiber will produce "scalloping" (bowing) of the existing 1/2" aileron trailing edge tubes when the fabric is shrunk too tightly. Others report that it is actually possible to warp the entire wing if fabric is shrunk too tightly. I can imagine heavy grades of fabric (2.7oz Poly-Fiber for example) imposing a "pull" much tighter than 1.7oz fabric or Tedlar.

My direct experience with 2.7 Poly-Fiber fabric on the wingtips however did not indicate any ill effects or deformity ? Go figure ?

As a footnote Carlson Aircraft is already set up to make "Lazair" custom aluminum trailing edge sections for the wings. I personally think this is a great updgrade for the wings regardless if you are covering with Tedlar or fabric.

PostPosted: Thu Apr 14, 2005 4:49 pm
by Shannon
Apparent minor scalloping of original 1/2" trailing edge with fabric covering.

Note: Tedlar produces nearly the same result when shrunk tightly.

PostPosted: Thu Apr 14, 2005 6:03 pm
by Shannon
Note: Scalloping doesn't seem to be a problem on the trailing edge of the ruddervator tubes or stabilizer tubes with 1.7oz Poly-Fiber though the fabric is fairly tight.

PostPosted: Fri Apr 15, 2005 10:00 am
by jb88ci
great stuff, Shannon.

I've already got the tail surfaces covered. There doesn't appear to be any scalloping. I'm going to start the wings this weekend. I've already done sharp trailing edge which seems to have increased the stiffness greatly. I will add a stiffener to the root rib as the picture shows.

I did note the black paint suggestion elsewhere but when i read the empirical data on paints and UV protection, i chose to just go with a high adhesive primer sealer.

Seems that white paint and black give the same uv protection as long as at least 2 coats are applied.