US20090193730A1 - Hurricane panel - Google Patents

Abstract

A hurricane panel configured to cover a building opening that is made of a geocomposite having an impermeable core and surrounded by both sides with batting, and anchoring means for attachment to a building.

Description

PRIOR RELATED APPLICATIONS
• This application claims priority to 60/954,567 (incorporated by reference in its entirety) filed Aug. 7, 2007.
FEDERALLY SPONSORED RESEARCH STATEMENT
• Not applicable.
REFERENCE TO MICROFICHE APPENDIX
• Not applicable.
FIELD OF THE INVENTION
• The invention relates to flexible panels that can be used to protect structures from hurricane and wind damage.
BACKGROUND OF THE INVENTION
• During hurricanes and other high wind storms, windows are often damaged, and the breach can cause great damage to the structure. Hurricane shutters are often used to protect building openings from the hazards of wind-blown debris and pressure changes. These are usually made from a rigid material, such as aluminum, wood and sometimes plastic. However, shutters are expensive, cumbersome and heavy. Plywood is inexpensive and is often used as a window covering during storms. But, although inexpensive, plywood is not durable, is awkward to store, difficult to put up, and does not provide optimal protection.
• From our experience in the environmental and petrochemical industry, we believed that there were a variety of flexible liner products available from landfill preparation or the petrochemical industry that could provide hurricane protection for homes and businesses in a more cost effective manner.
• Hurricane panels made of fabric are available. These panels are manufactured and installed to provide the protection required by the building codes of particular geographic areas. The building codes are based on standardized testing to meet certain standards of strength and integrity.
• For example, flexible hurricane window panels are described in U.S. Pat. No. 6,865,852, U.S. Pat. No. 6,325,085 U.S. Pat. No. 6,176,050, U.S. Pat. No. 6,886,299, and US2004159345 by TARGUS INTERNATIONAL™. These patents describe a protective barrier device formed of a flexible mesh material having a burst strength greater than 61.3 psi and an interstice size constructed and arranged to prevent passage of wind-borne objects greater than about 3/16 inch diameter, whereby the protective barrier is placed in front of a window, and secured thereto. Preferably, the protective barrier device is a textile formed from synthetic threads, for example, polypropylene.
• U.S. Pat. No. 6,341,455 by Gunn describes flexible material used to cover a window whereby cylinder or roller bar is used to deploy the covering in a manner analogous to a shade. However, the roller bar is difficult to fabricate and subject to jamming.
• U.S. Pat. No. 6,296,039, U.S. Pat. No. 6,341,639, and U.S. Pat. No. 6,431,250 by WAYNE DALTON™ describe a curtain system covering an opening in a building, but again the window attachment mechanism is cumbersome. Another cumbersome attachment means is described in U.S. Pat. No. 6,851,464, also by WAYNE DALTON™. U.S. Pat. No. 6,886,300, also by WAYNE DALTON™, requires that the panel edges be inserted into channels, and the fabric material stretched between the channels.
• What is needed in the art is a panel with sufficient strength that can be applied to a building in a simple manner with readily available hardware.
SUMMARY OF THE INVENTION
• The invention generally relates to methods, kits and panels for protecting a window in a building using a geocomposite membrane having reinforced edges and a core of impermeable plastic surrounded on both sides by batting and having a puncture resistance of 250 lbs when measured by ASTM D-4833. The geocomposite membrane can be anchored over the window with any anchoring and attachment means, including grommets and fasteners. In preferred embodiments, the method also employs a deflection inhibitor comprising at least one elongated member so placed as to span said building opening and placed underneath said geocomposite membrane, and the deflection inhibitor can be telescoping. In other embodiments, a rectangular strip is used on the edges further contribute to the attachment of the panel over the window. The rectangular strip also contributes to edge reinforcement since it spreads the attachment load over more of the edge of the panel.
• We designed a much stronger flexible panel than has been used in the past. The panel has an impermeable core (e.g., it lacks interstices), and is surrounded by batting layers on each side, giving the panel greatly increased strength, yet keeping it flexible for easy storage. We called the panel a Weathervest™ and a cross-section inFIG. 1 shows the impermeable core1 and batting3.
• The panel can be mounted directly to the building using readily available hardware, such as nails, bolts, hooks, screws, tapons, washers, clamps and the like, and as appropriate for the building construction. Alternatively, the panel can be attached with an attachment strip that allows fewer direct attachments to the building and spreads the load. A deflection limiter can be attached under the panel to limit the deflection caused by a hurricane-blown missile. The attachment strip and deflection limiter are preferably aluminum for lightweight strength and resistance to corrosion, however, other materials can be used, including sufficiently strong plastic or resin, iron, wood, metals, and the like. In one embodiment, the attachment strip can be affixed to the geocomposite membrane, and if so it is preferred that the strips be of shorter length with some space between strips so as to allow for easy folding of the panel during storage.
• The attachment strip and deflection limiter can be the same, or a special deflection limiter can be designed to be telescoping, for example. Where the attachment strip and deflection limiter are the same, they can be made available in a few standard sizes, allowing the home owner to select the sizes appropriate for the building windows.
• The edges of the panel can be reinforced for maximum strength at the point of attachment to the building. The reinforcement can be a flexible strip sewn or glued to the edges (e.g., a selvage), but for ease of manufacture and cost the panel may be folded back on itself and attached with grommets, glue, stitching and the like. In one embodiment the grommets are attached approximately 2 inches from the edge of the material.
• Grommets Size range from 3/16″ (00), ¼″ (0), 9/32″ (1), ⅜″ (2), 7/16″ (3), ½″ (4), ⅝″ (5), 13/16″ (6), 15/16″ (7), 1 1/16″ (8), 1½″ (10), 1 9/16″ (12). Grommet size can be adjusted to fit a variety of bolt, screw or fastener configurations.
• The panel is light, can be rolled up or folded, stored easily, and used multiple times. If desired, permanent yet discreet fasteners can be added to the house, allowing quick set up after the first use. For example, a hook or eye bolt is added to the house, and short stretchy cords (such as a bungy cord) can be used to hold the panel. Alternatively, a bolt can be added to the house, and the panel fitted over the bolt and a nut used to fasten the panel. In yet another alternative, a releasable clamp can be added to the house, that in the open position allows easy mounting of the panel, but when closed tightens the panel across the opening.
• Our testing shows that the panel can take multiple hits from hurricane-blown missiles with no damage. Another benefit is that the panel is impermeable to wind and water.
• The preferred geocomposite panel is constructed with something similar to the CANAL³123012™, which has two layers of 12 oz/square yard nonwoven polyester batting bonded to 30 mils of an EVA geomembrane. This material has a grab tensile strength of approximately 500 lbs, a Trapezoid Tear Strength of 150 lbs, and a Puncture Strength of over 250 lbs. These characteristics provide enough strength to resist debris puncturing and tear forces generated by a hurricane. However, other materials can be used, provided the basic structure and a Puncture Strength of over 250 lbs are maintained. Other geomembrane equivalents are listed in Table 1.

• TABLE 1
  Geomembrane equivalents.

  HUESKER			CARTHAGE				US
  CANAL3 ™	MIRAFI ™	WEBTEC ™	MILLS ™	AMOCO ™	SYNTHETIC ™	LINQ ™	FABRICS ™

  	135 N	NO3	FX-30HS	4535	311	125 EX	80NW
  	140 NL	NO4	FX-35HS	4545	351	125 EX	90NW
  	Mirapave 400	OL	FX-380L	4599	381	130 EX	90P
  				Petromat
  	140 NC	SD	FX-40HS	4546	401	130 EX	115NW
  	140 N	NO4.5	FX-45HS	4547	451	140 EX	120NW
  	160 N	NO6	FX-60HS	4551	601	150 EX	160NW
  	170 N	NO7	FX-70HS	4552	701	180 EX	180NW
  	180 N	NO8	FX-80HS	4553	801	225 EX	205NW
  	1100 N	NO10	FX-100HS	4510	1001	250 EX	270NW
  8208	1120 N	NO12	FX-120HS	4512	1201	275 EX	300NW
  123012	1160 N	NO16	FX-160HS	4516	1601	350 EX	380NW
  	—	—	FX-22	—	100ST	—	100
  	500 X	GS	FX-55	2002	200ST	GTF 200	200
  	550 X	GS-250	FX-60	2004	250ST	GTF 250	250
  	600 X	HD	FX-66	2006	300ST	GTF 300	315
  	HP 570	—	FX-400MF	2044	4 × 4	GTF 570	4800
  	FW 700	EP	Carthage 6%	1199	Geotex 104F	GTF 400	670
  	HP 550	—	Carthage 10%	—	—	—	840
  			HD
  	FW 402	—	Carthage 15%	1198	Geotex 111F	GTF 400EO	1540
  	FW 500	—	Carthage 30%	—	Geotext 117F	—	3040

BRIEF DESCRIPTION OF THE DRAWINGS
• FIG. 1. Cross section of geomembrane composite showing core (1) and batting (3).
• FIG. 2 Top view of panel (5), showing reinforced edge (7) and grommets (9), together with single attachment strip (11), also having openings (13) at the same spacing as the grommets (not to scale).
• FIG. 3. Telescoping deflection limiter showing smaller member (17) inside larger member (15) and openings (19) at end (not to scale).
• FIG. 4. End views of three deflection limiter embodiments (not to scale).
• FIG. 5. Deflection limiters in use on window (100) (not to scale).
• FIG. 6. Panel (5) showing grommets (9) approximately two inches from the edge of the panel. Grommets (9) are only placed along two edges of the panel and the panel requires no additional reinforcing.
DESCRIPTION OF EMBODIMENTS OF THE INVENTION
• The invention provides a novel use of a geocomposite that has traditionally been used as a chemical pond liner. The material is extremely tough, yet flexible and affordable. Further, it can be attached with readily available hardware, or can be attached with attachment strips. In a preferred embodiment, it is combined with a deflection limiter.
• In one embodiment, the invention is a hurricane panel made of a geocomposite membrane shaped to cover a building opening. The geocomposite membrane has a core of impermeable plastic surrounded on both sides by batting and a puncture resistance of 250 lbs when measured by ASTM D-4833. At least two edges of the membrane have anchoring means for attaching said panel to said building so as to cover said building opening, and preferably all edges have anchoring means.
• In another embodiment, the protective building panel comprises a geocomposite membrane having a core of impermeable plastic surrounded on both sides by batting and having a puncture resistance of 250 lbs when measured by ASTM D-4833. The geocomposite membrane is configured to cover a building opening. Further, a plurality of grommets are placed 2 inches from the edge of the panel on opposing sides of the panel. In use the panel further comprises at least one elongated attachment strip having openings at the same spacing. The attachment strip is placed over the reinforced edge, so that the openings and grommets are aligned. The panel is attached to the building by at fastener, passing through said openings and grommets and connecting to said building. Either embodiment can be combined with deflection limiters that span the opening, minimizing the deflection of the panel when struck by debris.
• FIG. 2 shows the panel (5) with a two inch edge (7) and grommets (9) six inches apart. A single attachment strip (11) with openings (13) is shown beside the panel. In practice, several of these would be used to attach the panel to the building by lining up the grommets and attaching the panel and the strip to the building using standard hardware.
• The batting of the geocomposite membrane can be nonwoven or woven, or combinations thereof. The batting materials can include polyester, polyolefin, cotton, air-fluffed wood fiber, and the like. The batting can also comprise mixtures of resins, one of which is a low melt fiber that can be used to impart further strength to the batting when heat set. The core can be any sufficiently strong plastic, including HDPE, LDPE, MDPE, LLDPE, EVA, composites, reinforced plastics and the like. Various combinations are possible, provided that the three layers together maintain the requisite puncture resistance. Suitable geomembrane composites include CANAL³123012™ available from HUESKER INC.™, as well as other commercially available plastic composites. The batting can also be covered with a polymer or resin.
EXAMPLE 1First Attempt
• In our first attempt to devise a flexible window covering we tried a reinforced polypropylene membrane from CARLISLE™. The membrane was prepared by doubling the edges and heat welding. Grommets were spaced at approximately 1 ft apart. The initial material was taken to an independent laboratory and tested by firing a 2″×4″ board at 50 ft/sec at the panel. The material failed the test by tearing at the grommets. It was decided that the grommet spacing was too wide, and that the tensile strength and puncture resistance of the fabric were not strong enough. A stronger material was needed.
EXAMPLE 2Material Selection
• In our second attempt, we searched for a much stronger commercially available material. We chose a geocomposite with nonwoven batting on both sides for added strength, but having a core of EVA geomembrane in the center. We believed that batting would add considerable strength where it was needed, on the outside of the panel, and the interior core rendered the entire panel completely water- and wind-proof.
• Suitable materials were available in three different weights (CANAL³8208™, CANAL³165016™, and CANAL³123012™ available from HUESKER INC.™). These materials are used for environmental applications, including canal liners, landfill cover liners, and wastewater lagoon liners, but have never been applied to house construction or as hurricane protection of buildings.
• The three geocomposites were purchased, fabricated into panels and tested by an independent laboratory, as above. Two of the three geocomposite panels failed the test tearing the material either at impact or at the grommets from the force of the 2″×4″ hitting them. The other geocomposite panel made from CANAL³123012™ was shot five times and passed the 2″×4″ test. From this, we have concluded that a puncture strength of at least 250 lbs and a trapezoid tear strength of 150 lbs provides sufficient strength and flexibility. Additionally, the material must be more flexible than the CANAL³165016™ to prevent tearing by 2″×4″ impacts.
• CANAL³123012™ is a geocomposite that consists of two (top and bottom) 12 oz per square yard polyester nonwoven sheets bonded to 30 millimeters thickness of an EVA geomembrane. The CANAL³123012™ is inert to biological degradation and naturally encountered chemicals, alkalies, and acids. This material conforms to the nominal values listed in Table 1 and provided by the manufacturer.

• TABLE 2
  Properties of Geomembranes

  	Canal3	Canal3
  	8208	123012

  MASS PER UNIT AREA, oz/yd2(ASTM D-5261)	36	50
  MEMBRANE THICKNESS, mils (ASTM D-5199)	20	30
  GRAB TENSILE STRENGTH, lbs (MD) (ASTM D-4632)	300	500
  GRAB ELONGATION, % (MD) (ASTM D-4632)	>50	>50
  TRAPEZOIDAL TEAR STRENGTH, lbs (ASTM D-4533)	100 (MD)	150 (MD)
  PUNCTURE STRENGTH, lbs (PIN 5/16) (ASTM D-4833)	175	250
  PERMEABILITY, (ASTM D-4491)	not measurable	not measurable
  CANAL3123012 ™ was fabricated into prototype wind panels, and sent to another
  independent laboratory for cyclic wind pressure loading.

EXAMPLE 3Testing
• An independent laboratory performed testing on four (4) Weathervest panels. The following tests were performed:
• 1) ASTM E 1886-02: Standard Test Method for Performance of Exterior Windows, Curtain Walls, Doors and Storm Shutters Impacted by Missile(s) and Exposed to Cyclic Pressure Differentials.
• 2) ASTM E 1996-02: Standard Specification for Performance of Exterior Windows, Glazed Curtain Walls, Doors and Storm Shutters Impacted by Wind Borne Debris in Hurricanes.
• 3) TAS 202-94: Criteria for Testing Impact and Non Impact Resistant Building Envelope Components Using Uniform Static Air Pressure Loading.
• The test specimens were 6′3″ wide by 9′0″ Weathervest™ fabricated from CANAL³123012. The edges were pierced with #4 grommets placed every 6 inches. The grommets were 2 inches away from the edge of the panel. With a 2 inch border and grommets at 6 inch intervals, it was not necessary to further reinforce the edge of the panels. The prototypes were installed into concrete masonry bucks using ¼″×2¼″ Tapcon anchors with 1″ diameter washers along the top and the bottom edges. The anchors were located 2″ from the corners and 6″ on center thereafter and passed through the metal grommets in the fabric. No attachment strip was used in the tests.

• TABLE 3
  Test Equipment

  	Cannon: Steel pipe barrel utilizing
  	compressed air to propel the missile
  	Missile: 2″ × 4″ Southern Pine
  	Timing Device: Electronic beam type
  	Cycling Mechanism: Computer controlled centrifugal
  	blower with electronic pressure measuring device
  	Deflection Measuring Device: 24″ Caliper

• The following results were recorded in the TAS 202-94, Static Air Pressure Tests, at a design pressure of +31.6/−34.6 psf:

• TABLE 4
  Static Air Pressure Test

  	Structural Loads	Deflection Readings (inch)
  	50% of Test Pressure (+23.7 psf)	12.6
  	Maximum Deflection
  	Design Pressure (+31.6 psf)	13.8
  	Maximum Deflection
  	50% of Test Pressure (−26.0 psf)	16.9
  	Maximum Deflection
  	Design Pressure (−34.6 psf)	18.1
  	Maximum Deflection
  	Test Pressure (+47.4 psf)	15.4
  	Maximum Deflection
  	Test Pressure (−51.9 psf)	20.0
  	Maximum Deflection

• Specimens tested for TAS 202-94 met the requirements of Section 1620 of the Florida Building Code, Building (2004). Tape and film were used to seal against air leakage during structural testing. The tape and film did not influence the results of the test.
• The following results (Table 5) were recorded in the ASTM E 1896-2: Large Missile Impact Test with a missile weight of 8.8 lbs, length of 8′1″, muzzle distance from test specimen of 17.0 ft. and average ambient air temperature of 91° F.

• TABLE 5
  Large Missile Impact Test

  Missile Velocity: 50.9 fps	Impact Area: Center of fabric
  	Observations: Missile hit impact
  	area, no damage
  	Deflection: 9.6″
  	Results: Pass
  Missile Velocity: 50.1 fps	Impact Area: Top right corner of fabric
  	Observations: Missile hit impact
  	area, no damage
  	Deflection: 3.3″
  	Results: Pass
  Missile Velocity: 50.1 fps	Impact Area: Top right corner of fabric
  	Observations: Missile hit impact
  	area, no damage
  	Deflection: 2.9″
  	Results: Pass
  Missile Velocity: 51.4 fps	Impact Area: Center of fabric
  	Observations: Missile hit impact
  	area, no damage
  	Deflection: 5.7″
  	Results: Pass
  Missile Velocity: 51.7 fps	Impact Area: Lower left corner of fabric
  	Observations: Missile hit impact
  	area, no damage.
  	Deflection: 2.0″
  	Results: Pass
  Missile Velocity: 51.8 fps	Impact Area: Center of fabric
  	Observations: Missile hit impact
  	area, no damage.
  	Deflection: 3.8″
  	Results: Pass

• The following results (Table 6a) were recorded in ASTM E 1886-02: Air Pressure Cycling test at a Design Pressure of +31.6/−34.6 psf:

• TABLE 6a
  Air Pressure Cycling Test

  			Maximum Deflec-
  Pressure Range	Number of	Average Cycle	tion at
  (psf)	Cycles	Time (sec.)	Indicator (inch)

  Positive Pressure

  6.3 to 15.8	3500	2.85	6.0
  0.0 to 19.0	300	3.30	8.4
  15.8 to 25.3	600	2.25	8.5
  9.5 to 31.6	100	3.06	8.8

  Negative Pressure

  10.4 to 34.6	50	4.55	17.0
  17.3 to 27.7	1050	2.40	16.5
  0.0 to 20.8	50	11.60	14.8
  6.9 to 17.3	3350	2.44	14.8

• In a second test the following results (Table 6b) were recorded.

• TABLE 6b
  Air Pressure Cycling Test

  			Maximum Deflec-
  Pressure Range	Number of	Average Cycle	tion at
  (psf)	Cycles	Time (sec.)	Indicator (inch)

  Positive Pressure

  6.3 to 15.8	3500	2.09	8.3
  0.0 to 19.0	300	5.27	8.5
  15.8 to 25.3	600	2.41	10.5
  9.5 to 31.6	100	3.70	11.0

  Negative Pressure

  10.4 to 34.6	50	3.25	6.7
  17.3 to 27.7	1050	2.46	7.8
  0.0 to 20.8	50	6.27	9.0
  6.9 to 17.3	3350	1.74	8.8
  			Permanent Set
  			N/A

• In another test at the following results (Table 6c) were recorded:

• TABLE 6c
  Air Pressure Cycling Test

  			Maximum Deflec-
  Pressure Range	Number of	Average Cycle	tion at
  (psf)	Cycles	Time (sec.)	Indicator (inch)

  Positive Pressure

  6.3 to 15.8	3500	2.06	5.8
  0.0 to 19.0	300	6.21	7.1
  15.8 to 25.3	600	3.77	7.8
  9.5 to 31.6	100	3.67	11.0

  Negative Pressure

  10.4 to 34.6	50	3.40	16.0
  17.3 to 27.7	1050	2.50	15.8
  0.0 to 20.8	50	6.19	14.3
  6.9 to 17.3	3350	1.91	13.9
  All tests were passed.

EXAMPLE 4Deflection Inhibitor
• One of the disadvantages of the impermeable core is that no wind passes through the panel, thus the full force of the wind or debris impacts the panel and can cause significant deflection (as much as 20″ over a 6′3″×9′ panel). There are buildings where such deflection would allow the impact to reach and break the window. In such cases, we have added a deflection inhibitor to further protect the windows, which is merely an elongated strip that crosses over the window and is placed behind the panel. Alternatively, or in combination, the anchoring means can be raised or thickened to place the panel further away from the window.
• In a preferred embodiment, the elongated member is telescoping to fit a range of window sizes, and multiple elongated members are arranged appropriately over the window in either parallel or crossed manner, or combinations thereof.FIG. 3 shows a telescoping deflection inhibitor in where thesmaller strip17 fits closely inside thelarger strip15 and each end has at least oneopening19.
• End views of three embodiments are shown inFIG. 4. The first end view is a telescoping deflection inhibitor, oneelongated member17 fitting closely inside the other15 and being held together with theedges21 and23. The second end view shows aplain strip25 havingridges27 for strength and the third view shows a reinforced deflection inhibitor with threeridges27 holding twostrips29 together. In its most simple form, however, the attachment strips are made available in various common sizes and can also provide the deflection inhibitor function. Parallel and crossed patterns of use onwindow100 are shown inFIG. 5.

Claims (20)

1. A method of protecting a building opening, comprising

a) obtaining a geocomposite membrane shaped to cover a building opening and having at least one edge, said geocomposite membrane having a core of impermeable plastic surrounded on both sides by batting and having a puncture resistance of 250 lbs when measured by ASTM D-4833, wherein said geocomposite comprises anchoring means,

b) attaching said geocomposite membrane to said building via said anchoring means so as to cover said building opening.

2. The method ofclaim 1, wherein said anchoring means comprises grommets placed along the edges of said geocomposite membrane at a first spacing.

3. The method ofclaim 2, further comprising a deflection inhibitor comprising at least one elongated member so placed as to span said building opening and placed underneath said geocomposite membrane.

4. The method ofclaim 3, wherein the at least one elongated member is telescoping so as to fit a range of building opening sizes.

5. The method ofclaim 4, wherein said elongated member is aluminum.

6. The method ofclaim 5 wherein the geocomposite membrane has two layers of 16 oz/square yard nonwoven polyester batting bonded to 50 mils of an EVA geomembrane.

7. The method ofclaim 5 wherein the geocomposite membrane is CANAL³123012™.

8. A protective building panel, comprising a geocomposite membrane having a core of impermeable plastic surrounded on both sides by batting and having a puncture resistance of 250 lbs when measured by ASTM D-4833, said geocomposite membrane being configured to cover a building opening wherein a plurality of grommets are placed along each edge at a first spacing, said grommets aligned to a fastener affixed to a building said fastener comprising a plurality of attachments for passing through said aligned grommets.

9. The protective building panel ofclaim 8, wherein the geocomposite membrane is CANAL³123012™.

10. A kit for protecting a building opening, said kit comprising:

a protective building panel, comprising a geocomposite membrane having a core of impermeable plastic surrounded on both sides by batting and having a puncture resistance of 250 lbs when measured by ASTM D-4833, said geocomposite membrane being reinforced along each edge and having anchoring means along each edge.

11. The kit ofclaim 10, further comprising attachment means that can operatively couple said anchoring means and said building.

12. The kit ofclaim 11, further comprising a deflection limiter that is an elongated member and having anchoring means at each edge.

13. The kit ofclaim 12 wherein the geocomposite membrane has two layers of 16 oz/square yard nonwoven polyester batting bonded to 50 mils of an EVA geomembrane.

14. The method ofclaim 10 wherein the geocomposite membrane is CANAL³123012™.

15. The method ofclaim 12 wherein the geocomposite membrane is CANAL³123012™.

16. The kit ofclaim 12, wherein said deflection limiter is a telescoping elongated member.

17. The kit ofclaim 12 wherein the anchoring means is a plurality of grommets.

18. The kit ofclaim 17, wherein the grommets are placed about 6 inches apart.

19. The kit ofclaim 18 further comprising one or more rectangular strips with anchoring means, said rectangular strips configured to as to contribute to the attachment means.

20. The kit ofclaim 19 wherein said rectangular strip and said deflection limiter comprise aluminum.

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