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Fiberglass cloth

KRAUSEGB

Well Known Member
Has anyone had trouble cutting the fiberglass cloth to the patterns required.
Using the suggested roller cutter, the fabric stretches so when I finish the pattern, it doesn?t fit the original?
How accurate does it have to be?

Gary
 
Draw with your blue or black Sharpie the shape and size required on heavy clear plastic about 8 mil. Lay your first over-sized layer of glass down and wet it out. Use a hair dryer to heat the epoxy & glass as you stipple with a brush,,,,or squeegee out the excess epoxy. You want all the glass wet out using the least amount of epoxy resin necessary to do so. Repeat for each layer. Use a hand held light to inspect each layer as you go to ensure the cloth is whetted out, no air bubbles, and no excess epoxy. Now when done with all your layers, cut out the shape you drew,,,,,,,you can see right through the properly wet out layers. Carry it over to whatever you are working on and wet that area out where you are going to apply your patch or whatever. (You did clean and sand that up REALLY good first with 36 grit Zircon cloth backed paper 'til it was dull and no shine ,,,,,,right?) Lay your piece in position and carefully peel off the clear plastic,,,,use a pick and paint brush to assist in peeling and pushing, stipple the patch on. Now if you want a REALLY nice transition finish,,, you will have some peel-ply fabric to lay over the patch and surrounding area. I peel-ply everything I do. Stipple that on with epoxy and heat from your hair dryer. Leave the edges of the peel-ply with no epoxy. Now leave it be until FULLY cured. When cured, grab a corner of the peel-ply and strip it off. You will be amazed at the perfect looking and structural sound patch or joint you just completed.
 
What is Peel-Ply Fabric, 9GT?

Helpfull instructions for fiberglass greens like me, thanks 9GT. However I have no idea what peel ply-fabric is. Can you elaborate?
Thanks
 
Peel ply is a material like polyester dress lining, it is used to give a smoother finish to a layup, or to create a bondable surface on a layup.

Peel ply does not stay in the layup, you "peel" it off after the resin hardens. The surface left will be flatter overall, but have small "teeth" in it. The surface is easy to finish with minimum sanding, or is ready for another layup without sanding.

Here is some good info.

http://www.clcboats.com/shoptips/epoxy_and_fiberglass/peel-ply-release-fabric.html
 
Peel Ply is a smooth dacron fabric that is used to get a smooth top layer. Aircraft Spruce sells it.http://www.aircraftspruce.com/catalog/cmpages/peelply.php It's cheap and works great. My only tip on the fiberglass is get your contour shaped correctly. Fill in the areas where the cloth "drapes" over the canopy frame with extra foam and sand to where it is the final contour. Mine was close, but not exact. I spent ten times more effort sanding an filling later than it would have taken to get it right in the first place.
 
One more thing I forgot to mention is that the fibers of the cloth must be straight. That's EZ with UNI (one direction) cloth where the strands are straight and are held together with thin woven fiber strands. This provides strength in one direction only unless you put the next layer at a 45* to the first and so on. The other most common weave is BID (bi-directional) where the strands are woven at a 45* already. Here is where its hard to hold a shape you cut out as it stretches and distorts easily,,,,hence using the plastic to help hold its shape. Its really important that the fiber strands are straight with BID to maintain its structural strength. BID is generally used for taping joints and for curves, as it shapes easily and will stay where you put it. You also alternate the direction of the weave with each layer....think "X" pattern. Now if you have a compound curve or shape you are trying to glass and the UNI does not want to stay put,,,,lifts up in areas or forms air bubbles,,,,,some times the Peel-ply will hold it down, especially if you are using a light weight peel-ply. If it does not,,,,,take a clean piece of clear kitchen saran wrap and cover everything working out all the air. It does a really good job of holding the glass work down. Its a PITA to remove afterword's though so use it only when needed.
 
The other most common weave is BID (bi-directional) where the strands are woven at a 45* already.

Nope.

BID is woven at 90*.

It is often cut so the weave lays at 45* on the work, this gives an amazing amount of ability to fit on compound curve parts.
 
Another handy method

1) Make your patterns. If you can do them in something like cardboard or poster board, even better.

2) Get some 3M77 contact spray from Home Depot/Lowes etc.

3) LIGHTLY spray the pattern and lay on waxed paper.

4) LIGHTLY spray the waxed paper and lay an oversized piece of the glass cloth over the pattern. With this method, using a 45 degree cut isn't absolutely necessary.

5) Cut the glass to the pattern. You'll find it very easy to cut now. Keep the waxed paper on the glass.

6) Lay the cut piece on a larger piece of waxed paper.

7) wet out the cloth with the epoxy.

8) Apply to where you want it. The waxed paper will come off easily.

9) Apply ply peel and press into the cloth.
 
Wax Paper Method

Thank You RV7Guy. The wax paper method for cutting the cloth and setting in place worked great.

I sprayed a little quick stick on the wax paper, cut to shape, wet the cloth, Put another piece of wax paper on top and squeeged out the excess resin.Set the cloth in place and peeled the wax paper off.
Thanks again
 
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Hi Folks,

This is a RV-12 thread and most of the sage advice is not the way it needs to be done on the RV-12.

This is one of the areas that Van's plans is very well thought out, follow the plans, do it Van's way and it will work out just fine.

As to the earlier question about using the pattern, it may take two people (three hands holding things in place and one hand rolling the cutter) to keep the fiberglass held down firmly as you cut and it is very important to have a sharp blade. Use the larger plastic cutting board with grid lines so that you can line up the fiberglass straight and keep it that way. Yes the fiber glass may stretch a little but Van's has you making extra area everywhere except the line on the windshield so get it right and try to keep the rest so that you have the planned excess area on all the other lines. When you are done it is easy to cut off the excess to the trim line on the template.

Van's system of placing the first layer on wet and the rest dry and wetting them out in place works very well just follow the instructions.

I have found it helpful to have ten (10) sheets of cardboard with a piece of wax paper ready for each one, number then 1-L to 5-L and 1-R to 5-R so that you can slid the cut piece from the cutting board to the wax paper on the cardboard (you got some nice large sheets in the Van's crates) this reduces the handling and stretching. The first piece can be wet out right on the wax paper and moved on it to the aircraft for placement. Follow the instructions and let the first layer tack up and then proceed with the other layers and the cross strips which can be cut to width and laid out folded in half on a cardboard numbered 1 to 10 so that you can be ready to place them in the proper order.

The one variation on Van's plans I have found is that I get nicer edges on the windshield by using the 4 inch wide fiberglass tape from Aircraft Spruce as it has a very nice factory edge on one side that will lay down very nicely as the first layer and it is much easier to cut the small widths required if you take a 3 foot long tape and fold it in half so that the finished edge is even then use a metal yard stick to hold down the width you need and run the roller cutter right along the metal edge.

This has served me well on the 5 RV-12 canopies I have done so far.

Good luck.

Best regards,
Vern
 
It worked well for me

Thanks Vern, but there is more than one way to skin a cat. I also used the 4" cloth across the center. Just felt RV7guys idea worked well for me.
What ever works is the right way to go.

By the way, I still have all the cloth I cut Van's way for other projects.
 
Not sure wax paper is such a good idea. Don't hear much mention of it in the composite world. If the wax gets into the epoxy you've contaminated the work. With wax it would then not be the best surface to either do more layups or filler or paint. Clear plastic works very well for all the things discussed above and doesn't have any coating that might be a problem. Then peel ply finishes up the layup leaving a smooth surface ready for further work.
The 45° cut is important, when required, for more than convenience.
Just some thoughts....discard at will....:cool:
 
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Wheel cutter

Has anyone had trouble cutting the fiberglass cloth to the patterns required.
Using the suggested roller cutter, the fabric stretches so when I finish the pattern, it doesn?t fit the original?
How accurate does it have to be?

Gary

Gary

Go to a fabric store ask for a wheel cutter pad.
The fiberglass will cut edge clean, use a sharp wheel.

Pegasus
Queen Creek, Az.
 
Been using the same OLFA rotary knife almost 20 years (with a blade change or two): http://www.aircraftspruce.com/catalog/cmpages/rotarypizzacutter.php

The slick-face plywood Vans uses for crates makes a fine cutting board. My former favorite was formica. I don't recall a real problem with the pizza cutter pushing fabric around on any surface.

Most fabric cuts are made with excess and trimmed after placement and wetting. You want a good pair of pointy all-steel barber shears. If the task calls for a precisely sized section of glass, wet out, draw dimensions, and cut between plastic. Point is, you rarely need to cut perfectly accurate lines in dry fabric. When you do it's almost always a straight line and you run the pizza cutter along a heavy gauge straight edge.....which clamps the fabric to the table. I use a 48" aluminum rule 1/8" thick.

Wax paper won't hurt anything, but you can see through clear 4 mil plastic.

There is no application for UNI fabric on any RV. Use plain weave BID for flat or single-curve surfaces. Use a harness weave BID for compound curvatures. Fabric information this thread:

http://www.vansairforce.com/community/showthread.php?t=41375
 
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Wax paper won't hurt anything, but you can see through clear 4 mil plastic.

Gotta respectively disagree with you Dan. The only composite guru that ever suggested using wax paper was Nat Puffer and he modified his recommendation in the following Builder Hint:

Newsletter# 50 / July 1995
from Builder Hints...

Taping joints. For Structural reasons, all joints should be taped with 2 plies of BID 2' wide (1" on each surface) cut on the bias (45 degrees) unless otherwise specified. After application, the tape should be peel-plied. One recommended way to accomplish this is to wet out 2 plies of BID on wax paper or Saran wrap, cut into strips, apply over joints, remove the wax paper or Saran wrap, cover with peel ply and wet out same. Wax paper should only be used with discretion. It should not be left in place while the epoxy cures, because wax will be left behind, and it should only be used on those joints which will not be later covered with additional layups. Glass layups. Remember, BID is always cut on the bias and overlapped l' in every direction, but UND is overlapped only in the direction of the major fibers.

Rutan said never use it.

The heat from layups in warm weather can melt wax into the layup and make further attachment of anything poor. And you can't use a hairdryer on the layup under wax paper as many of us do to to finish the squegee process and minimize epoxy and weight.
 
No disagreement. My comment refers to using wax paper or plastic as a wet-out aid. There's no reason to allow cure in contact with wax paper, and I'd like to think nobody is dumb enough to heat wax paper in contact with a layup.
 
...I'd like to think nobody is dumb enough to heat wax paper in contact with a layup.

Unfortunately, the epoxy itself isn't that smart. I've had thick layups pretty routinely run themselves up to 130 degrees F on exotherm energy alone.

Thanks, Bob K.
 
If you are using tape, this version can be quite useful for curved areas while giving a sharp edge.

Two layers of 45 degree weave made into a 4 inch tape. From any of the usual West Products vendors...

http://www.pbsboatstore.com/727-pisize-biaxial-tape.htm

Ooh, I know that stuff. It's 4" strips of a knitted (not woven) double-bias product called Kyntex (or sometimes Knytex, the ACS catalog misspelled it once and that name has sort of stuck). To make it, they lay down a bunch of fibers 45 degrees one way, then lay down some more 45 degrees the other way, and then they stitch it all together with polyester thread. I use Kyntex a lot where I need a bunch of bias fibers but I don't want to do a bunch of bias cutting.

This stuff is good for reinforcing tapes, but in my experience it tends not to leave the best surface finish on repairs and male-molded parts. I'd be inclined to use a final ply of 7781 or 7725 (the Hexcel version of the Interglas 92125 used in European sailplanes since the late 1960s) cut on the bias to get a finish that's easier to fill and smooth.

Thanks, Bob K.
 
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