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  #1  
Old 04-27-2004, 09:36 AM
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John Slade John Slade is offline
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Default Plastic Peel Ply

PLastic peel ply is the use of clear 4 ml plastic sheeting, as found in home depot, on top of the finished layup and any standard cloth peel ply. The technique has been described as "poor mans vacuum bagging". The plastic sticks to the wet epoxy and shows up bubbles very well. Squeege over the plastic with a little help from a hair dryer and you can watch the bubbles run along in front of you're squeege and out the edge. Wet the squeege with epoxy for a better slide over the plastic. The air can't get back in because of the seal caused by the plastic. Lots of excess epoxy can be removed this way for a very tight, compact and lightweight result. Do not press too hard because air can be sucked back into the layup through the foam - you'll see this when it happens because the area goes dark when you squeege it, then goes white again. If this happens lift the plastic and add more epoxy. After cure the plastic comes off in an instant and you have a very smooth, almost moldlike finish. I describe this in detail in my web page "tips and tricks" section. http://canardaviation.com/cozy I first saw this at Bulent's shop 3 years ago after finishing my fuselage sides. I've used it ever since. The airframe is now finished and in gloss. The only place I saw pin holes was in the parts I did BP (before plastic). Try it once. You'll never go back.

In my experiments a 15% reduction was recorded in the weight of the layup. I subtracted the weight of the foam in each case.

Significant compression DOES take place using this method. With the squeege sliding on plastic the fibers are squeezed. Air can't get back in, so they stay squeezed. Its hard to get a dry layup this way, and its very obvious when you do. The color change from light to dark as the squeege passes tells you everything. Air bubbles are being displaced. The gloss finish is very easily scuffed up for bond since there is no weave to deal with. I think we had the best suggestion earlier - try it on some test pieces and do structural tests. Prove (or disprove) the technique with practical experiment rather than theoretical science.

Note: See my web page, http://canardaviation.com/cozy/chap20.htm for pictures and discussion of this method.
  #2  
Old 04-28-2004, 06:43 PM
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I think this should be called "Peel ply and plastic"

Currently it makes me think the peel ply is plastic.
  #3  
Old 04-28-2004, 07:02 PM
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Default

Maybe call it Pressure Bagging. Its vacume bagging in reverse, and the plastic is not really a peel ply layer... or maybe it is. I dunno.

Oh... how about SMOOTH PLY? SLICK PLY?
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  #4  
Old 04-28-2004, 07:07 PM
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I dunno either. We've had lots of name suggestions, and no-one gets to decide which is the right one. I gather SportAir are teaching it these days. I wonder what they call it.

The main issue here, whatever it's called, is that it works. Use it.
  #5  
Old 04-29-2004, 03:54 PM
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Default Behind the curve....

John,

Have you moved your site from the garden????? url. If so I need to update my links from my builders page. I hope you have since I could never remember your url, but even I may be able to remember canardaviator.com. Hmmmmm, I will be 43 a week from Saturday, should I be having "Senior Moments yet" <g>

All the best,

Chris
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  #6  
Old 04-30-2004, 02:43 PM
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Quote:
Originally Posted by CBarber
I will be 43 a week from Saturday, should I be having "Senior Moments yet" <g>
A Taurus (Earth sign) building a plane? are you sure thats wise.

Chris you're almost exactly 10 years older than me, My 33rd will be May 18th.

May birthdays rule.
  #7  
Old 04-30-2004, 02:54 PM
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Quote:
Have you moved your site from the garden????? url.
Yes. The old site is still up, but the new one is next door: http://canardaviation.com/cozy
I'd appreciate it if anyone linking to kgarden change the link.
  #8  
Old 05-01-2004, 07:29 PM
alexmadsen alexmadsen is offline
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Default skip the frosting and sanding ?

Say, Would it be possible to skip the frosting and sanding of wings if one used the plastic ply (for Velocity)? The fact that there will be no air bubbles, no weave marks, and uniform epoxy should eliminate surface irregularities. I gather that frosting and sanding is one of the worst and most time consuming parts of composite construction.
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  #9  
Old 05-01-2004, 08:21 PM
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Sorry, but I don't think so.
Even with plastic peel ply there are some irrgularities, and the overall surface is probably not perfectly flat, so I think you'll have to cover everything with a layer of micro and sand with a long board to get the finish right. I know a lot of the velocity parts are prefinished, but these's going to be plenty of areas where you need to blend things in.

Really, having done it, suffered and whined like everyone else, I don't think the finishing part is as bad as people make out. [looking back on it]
  #10  
Old 05-02-2004, 03:38 AM
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Quote:
Originally Posted by alexmadsen
Say, Would it be possible to skip the frosting and sanding of wings if one used the plastic ply (for Velocity)?
Uh, no. I can not imagine you could or would even want to. In addition to what John mentions, also remember the Velocity uses one layer of Triax for the wings. Triax has a thicker weave. Brendan at the factory actually suggested to me not to use the peel ply on the wing. He said even though the difference may be slight, the peel ply forces raw epoxy into the grain of the weave (and you will still need to use micro for finishing). When you use micro, you are forcing micro into the same grain and by design (micro is used to fill and lighten the epoxy), micro/epoxy is lighter then straight epoxy in the same area and volume. Of course, your mileage may vary. FWIW.

All the best,

Chris
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