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Uni-Directional Bi-Directional
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Note: 38" wide. Sold by the yard

The most basic structural material in building a composite aircraft is glass cloth. The use of glass in aircraft structures, particularly structural sandwich composites, is a recent development. Glass cloth is available commercially in hundreds of different weights, weaves, strengths and working properties. Very few of these, however, are compatible with aircraft requirements for high strength and light weight. Even fewer are suitable for the hand-layup techniques developed by Burt Rutan for the homebuilder. The glass cloth featured here has been specifically selected for the optimum combination of workability, strength and weight.

Two types of glass cloth, a bi-directional cloth and a uni-directional cloth are used. BID cloth has half of the fibers woven parallel to the selvage edge of the cloth and the other half at right angles to the selvage, giving the cloth the same strength in both directions. UND cloth has 95% of the glass fibers woven parallel to the selvage, giving exceptional strength in that direction and very little at right angles to it. BID is generally used for pieces which are cut at a 45 angle to the selvage, a bias cut, which enables the builder to lay BID into contours with very little effort and provides the needed shear and torsion stiffness for flying surfaces. UND is used in areas where the primary loads are in one direction, such as wing skins and spar caps. Multiple layers of glass cloth are laminated together to form the aircraft structure. Each layer of cloth is called a "ply".


  • 7 oz 38" Width Threads per inch
  • Construction: 80 Warp Tow Count X 18 Fill Tow Count

  • 8.8 oz 38" Width Threads per inch
  • Construction: 54 Warp Tow Count X 48 Fill Tow Count


Just as it should be

Keith S Verified Purchase


June 16, 2021

I ordered this cloth to be shipped folded, against the advice of AS, but there was no harm.

Edward S Verified Purchase


June 12, 2021

Aircraft Spruce took extra care to make sure the fiberglass was placed on the roll without disrupting fibers and protected it very well so it wouldnt get damaged during shipping. Great job!

Bernie N
January 3, 2021


Dasdas D
December 12, 2020

Ive been surprised at what is not stored at Corona - sometimes seems like a storefront...for composite guys - but understand the tax woman is surveying anything not screwed down to tax repeatedly. The BID sale went very well. My son, who took over a Cozy project is waiting a month for a list of things like strake foam.

David O
July 31, 2020

Works great with West Systems epoxy.

April 20, 2020

really easy to work with and just what I needed

Bob S
February 8, 2020

Still the best fiberglass cloth for new construction or repairs,

Fred K
July 27, 2019

April 13, 2017

Aircraft Spruce always does an excellent job shipping UNI fiberglass. This is a difficult product to ship, but it always arrives in excellent condition.

February 20, 2017


Q: Can I buy it by the roll? If so how much is on a roll, and is there a discount?

You can buy by the roll. The roll is approximately 125 yards. 15 percent discount kicks in at 500 yards.

Q: What is the thickness of each of the two Rutan fiberglass cloths?

The thickness of the unidirectional cloth (01-00641) is 0.19 mm. The thickness of the bidirectional cloth (01-00642) is 0.23 mm.

Q: What is the thickness of each of the two Rutan fiberglass cloths?

The thickness of the unidirectional cloth (01-00641) is 0.19 mm. The thickness of the bidirectional cloth (01-00642) is 0.23 mm.

Q: What is the per yard weight of each of the 2 types of rutan fiberglass cloths?

The uni (p/n 01-00641) is approximately 7.0 oz / yd. The bid (p/n 01-00642) is approximately 8.8 oz / yd.

Q: What is the correct weight per square yard of PN 01-00642? What is the strength of each of these cloths? Warp and Filling?

Part number 01-00642 is 8.8 oz/yd. The breaking strength of P/N# 01-00642 is warp- 440 lbf/in,Filling- 366 lbf/in. P/N# 01-00641 is warp- 650 lbf/in, 70 lbf/in.

Q: Regarding part # 01-00641: Is this E glass or S-2 glass?

This is uni-directional E-Glass.

Q: What is the correct adhesive to use with this fiberglass cloth for a structural layup?

You can use Aeropxy Strucural Adhesive Part # 01-00295.

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