What mat'l. is this and where do I get some? Can wax paper be used as a substitute?
What mat'l. is this and where do I get some? Can wax paper be used as a substitute?
Peel ply is a fabric-type release material used in vacuum bagging. It is usually teflon coated fiberglass for high temperature molding, or nylon for room temp work. Epoxy will wick through it (similar to wetting out glass) but the epoxy won't stick to it. The wicking action will remove excess resin from the layup. When the epoxy has cured, you peel the material away from your laminate, taking the excess resin with it. You are left with a rough-textured surface which helps when you want to bond additional layers or parts to this first layup.
Peel ply is available from all the major composites suppliers, including CST.
Peel ply is like a teflon coated fiberglass, that when removed, leaves a semi rough, bondable surface. Typically this is the last ply on your layup, you wet it out just like glass, then remove it when cured. Really cuts down on sanding.
David, seems like we where both typing at the same time. How funny!
Thank Guys for the info. I just ordered some from cst.
I have to clarify the use of peel ply. Lets' say for example a wing is to be glassed with 3/4 oz cloth and vacuum bagged. One side of the wing is glassed and the cloth is saturated with resin some of which will be squeegeed off. A piece of peel ply is then laid on the wing and smoothed out. There is no need or any point in applying resin to the ply. On top of the peel ply breather cloth is applied. The same is done for the other side of the wing. The whole lot is put into the vacuum bag. As the pressure on the wing builds up the resin soaks through the peel ply and into the breather cloth. The breather cloth is essential for this process. It is the cloth that soaks up the excess resin, not the peel ply. The ply is there as a parting material to allow the cloth to be removed. There is not much point in using it without breather cloth. once the ply is saturated any more excess resin has nowhere to go.
The big disadvantage of all this is, the ply or cloth is not re-usable. When it is all stripped off the wing it goes straight into the garbage. I have used paper towels as a substitute for breather cloth. Provided most of the excess resin has been removed when applying the 3/4 oz cloth the paper towels work just as good. I have been told, but I have not used, that Taffeta from a fabric store is a good substitute for peel ply.
If you describe your application we can be more specific.
I have aerospace composites vacuume bagging system. It came with everything except the peel ply which they don't include in their EZ-VAC I kit. I'm using the bagging machine to attach 1/16" balsa wing skins to foam cores. This will be my first time using this technique with the vacuum bagging. Their instuctions say to place peel ply over the top balsa wing sheeting and then on top of this the breather felt. They say "the peel ply will prevent the breather cloth from bonding to the sheeting or to the leading edge should any resin ooze out. Once the resin has cured, the peel ply can be easily removed."
I always suggest that it is best to follow instructions when doing something for the first time.
The following is based on my experience. I have built a lot of wings. I do not use the breather cloth or peel ply when sheeting wings, it is not necessary. I do have some narrow strips of breather along the edges and across the ends of the bag and to the outlet connector. When applying resin to the skins pour it on and then squeegee it off, there should be just enough resin on the skin to make it look damp. not shiny wet. If the correct amount is applied the resin will not ooze through the skin. The bag will close in on the LE and TE of the wing. It may stick there. However the bag material releases very easily from cured resin. I use my bags over and over again.
Thanks Ed for the reply. I made a small test peice to see if this process was lighter and stronger than using 3m 77 spray glue. You know, it was lighter and stronger. I see why it was lighter, because you go back to scrape off all the epoxy from the wing skin and have that damp look (sheen). I was very, very sceptical about how the skins would attach to the foam because there litterally was no "wet" epoxy look on the balsa sheeting. I really thought it was'nt going to adhere or hold to the foam. It actually bonded to the foam and i purposly broke some of the sheeting away and saw that all the foam beads were glued to the balsa. I really was amazed and impressed! I guess there is alot of pressure being applied to the coares, that it squeezes the epoxy out from the wood grain. And/or maybe because the foam is poros and the vacuume sucked the epoxy out of the wood grain.
Works just like a band-aid;)
Waxed paper works too. And is cheap
I was thinking about that, But would'nt it be harder to sand off the epoxy because it would be smooth?
If epoxy is being squeezed out, then there is way too much. Use a wood sealer on the balsa skin, let it flash, off then sand it lightly with 80. Mix a thick slurry of epoxy/cabosil and quickly squeegee on and right back off. Scrap back off hard. All of it must come off! The grooves that the 80 grit made will be full of the epoxy weither you realize it or not.
Wrap the part in wax paper, then paper towels and bag it. Any squeeze out will be minimal.
Remember, it just a model wing. Don't try to build it to be full scale.
Also, 3M77 works fine, so you only need enough epoxy to have the same strength as spray adhesive
I'm going to slightly stray from the bagging topic but...
Your saying that you have used just 3M77 to attach sheeting to a foam core? I've sheeted wings in the past but have always used epoxy, I never thought that 77 would be good enough or would even hold the sheeting to the airfoil shape.
I'm assuming that if your using 77 to attach the sheets, that the wing is then glassed? 77 wouldn't work if you had planned on using covering would it?
AHHHHHHHH!!!!!!!!!!!!! Why does everyone overbuild??????????????????? They are models!!!!!!!!!!!!!! Has anyone actually seen a wing brake in flight??? (glider guys, you can stay out of this, I've seen what that ol winch can do)
Have you ever tried to remove something that was put on with 3M77??? It is NOT going to come off. NO, the wing is not glassed. The problem with spray adhesive is that the sheet MUST be put on right the first time, there is no second chance.
Sorry guys, I had to vent!
Well I'll test it before swearing by it. I have to admit I've never used 77 on anything as course as foam... Are we talking little, lightweight models or 5lbs+ models? I don't fly the little guys at all.
Do you apply it to both surfaces before putting the sheet on (like contact cement) or just spray it on the foam? I'm concerned with warping the foam, getting a twist in the wing. If it can't be moved once in place, it would seem that it would be pointless to put the wing back into block and press it like you do when expoxying them to make sure they are straight.
Vent all you like, I don't know you from a hole in the ground. I'm just here to learn some new tricks and try to help out where I can. :)
My experiance is with 35% aerobatic planes. Contest balsa seems to really suck up resin even after it has been sealed, so I came up with this process.
The process I use is I set the core in the saddle and sand lightly with 80 grit, then with 150grit. I position the skin on the core and mark a centerline on the core and on the bottom of the sheeting. Once I a positive that the wing is sitting square, I spray the core and sheeting, I bend the sheeting so that the center is bowed down (you really need two people for this) and then lower the skin on to the core at the center marks, then just follow with the same motion down until the sheeting is all the way down.
I always throw the top cradle on and weight it down but I cannot say if it realy helps anything. I guess just for a piece of mind.
The thick epoxy/cabosil works too, but its not as lite. That darn porus balsa!
Ok, I'll test it out, can't hurt...
Yeah. Thanks Darrinc for the informative information.
A friend of mine used 3M77 to attach the sheeting on his Lanier Laser, he is a old school biulder with tons of redundencies and a LOT of epoxy and it came out at 28lbs. With that kind of wing loading and the agressive style of flying that he does, he has never had a problem with the wing sheeting. (hopefully this is is the worse case senareo)
A peel-ply is used to separate the composite surface from the bleeder and breather. Wax papaer won't work much above room temp. nor will it provide a realitivly smooth surface needed for minumal sanding. nor allow excess resin to be removed.
It is generally a nonporous material, though there is a (breathable) type that will allow the extra resin in the fabric to be absorbed into a kind of wick such as a layer of fiberglass. It is then topped with a nonporous layer and breather cloth..
A resin rich fabric is not as strong as one that has the proper amount of resin.