BAMBOO REFERENCES

AMERICAN BAMBOO SOCIETY: http://www.americanbamboo.org/GeneralInfoPages/PNW1994BambooAgro.html

Check out the home page for a summary of the 1994 conference in Gold Beach, OR, on a wide range of subjects, including growing bamboo in New England.


BAMBOO: A MULTI-PURPOSE AGROFORESTRY CROP By Steve Diver, NCAT Agriculture Specialist, August 2001 The bamboos are gaining increased attention as an alternative crop with multiple uses and benefits. These long-lived, woody-stemmed perennial grasses are usually evergreen in climates to which they are adapted; those of temperate regions grow a complete set of new leaves each spring, the old ones falling away as the new ones develop (1). Worldwide, approximately 87 genera and over 1,500 species of bamboo exist (2), with roughly 100 species comprising those of economical importance.


BAMBOO LIVING HOMES AND RESORTS: http://www.bambooliving.com/bambootech.html
Bamboo Vision. Bamboo Technologies (BT) was created in 1995 as a shared vision to create an environmentally sustainable housing alternative in the building industry. Bamboo was chosen because of its superior ability to create biomass and replenish the earth’s clean oxygen supply, offering high quality, beautiful structural material.

TROPICAL BAMBOO NURSERY: http://www.tropicalbamboo.com/
Tropical Bamboo® Nursery is the premier supplier of non-invasive, ornamental tropical bamboo plants that grow only in a clumping manner. Many of these clumping species have only become available in the U.S. during the past decade, providing a new, exciting controlled element for landscapes.

YOUTUBE CLIPS:

Youtube Plantation Assembly: http://www.youtube.com/watch?v=6NofDRQk1vM&NR=1

Bambusa emeiensis Viridiflavus - Yin Yang Bamboo: http://www.youtube.com/watch?v=eVsOC4gczwk&NR=1

Construction in bamboo - Colombia (first part): http://www.youtube.com/watch?v=YSNQj7CDkxE&feature=related

Construction in bamboo - Colombia (second part): http://www.youtube.com/watch?v=SmZR04l_hA8&feature=related

Construction in bamboo - Colombia (third part): http://www.youtube.com/watch?v=bxxkdgpoafU&NR=1

Bambu Guadua Parte 1: http://www.youtube.com/watch?v=ZlQCeFt6Sm8&NR=1

Bambu Guadua Parte 2: http://www.youtube.com/watch?v=JsSmma_GBU8&feature=related

Prototipo bambu estrutura: http://www.youtube.com/watch?v=9UZXP-Xb6Jw&feature=related
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How to process giant bamboo into engineered lumber and sheeting.

Flat stock, 8' x 8' called Oha-sum Soy & Bamboo – OSB.

An article about bag vacuums follows this procedures list.

1. Harvest long culms of bamboo so that increment of about 8.5' can be taken from the stalk.
2. Remove any leaf branches
3. Line up stalks so that the ones of the same diameter and approximate length are next to each other in a group.
4. Cut lengths at 8.5' keeping the lengths together in a group.
5. Groups of about the same diameter are then cut exactly in half with a table saw with guides which automatically adjust for the slight taper of the stalk. Mark each side with a progressive numbering stamp, on opposite sides and 180 degrees in orientation so pairs and kept together.
6. Remove the inner parts at the joints of the halves.
7. Put in a steamer to inject hot steam and water into the halves.
8. Remove and put in a hot press, one layer at at time; squeeze out what water we can and flatten each cut.
9. If made for engineered lumber remove the ridges at each joint with a thickness planner. Renumber if necessary. We might use a metal stamp to impress the number deep into the bamboo at one end. If decorative, we could leave the ridge.
10. Run the halves through an edger to get a perpendicular smooth edge. These finished pieces are now call fletches.
11. Assemble the fletches so that the matching halves are placed next to each other and rotate one so that the haves are opposite an the slight taper is off-set by the twin cut stalk.
12. Build and air bag press with a perforated deck and a permanent, mylar sheet across the underside of the perforated deck. This lower sheet of mylar will draw the wood tight against the perforated deck to provide for uniformity of the lower surface. A metal frame holds the mylar rather straight across the frame and is permanent. The mylar is set to move easily up against the bottom of the perforated metal.
13. The top frame matches the bottom frame and has a gasket to seal against air passage. The two frames clamp tight. The upper frame has the same mylar set-up. There is a piano hinge along one side of the outer edge of the two frames.
14. Lay a thin sheet of micro perforated film (“Peel-ply”) across the top of the perforated metal so that the glue if it drips will not be deposited on the pref. Metal.
15. Lay-up the bamboo fletches, using soy glue. The strips are about 8' 5” by 8' 5” so that the fit within the perforated steel table. Fletches are laid so that the tapers of each half are opposite. Each course is changed 90 degrees. Depending in the thickness of the milled bamboo fletches, we could probably get three courses for half inch, five courses for three-quarter inch, and six courses for 1 and 1/8th inches.
16. Half inch OSB is good for outside wall sheeting and furniture, and the five-eight's OSB is good for roofing sheeting. The 1&1/8th will be made into tongue an groove floor sheeting.
17. After the strips are laid-up, the frames are mated, closed and a vacuum is applied to the inside of the bag. The bar on the top will be close to 30” of Hg. And the bar on the bottom will also be close to 30” of Hg., thus giving the OSB a double whammy.
18. If the soy glue is heat set, we can add some heat to the mylar, being careful not to deform or melt it. Electric blankets from a department store out to work.
19. After the glue is set and the OSB cooled down, it can then be run through a table saw and the edges trimmed. If 4' x 8' sheets are needed, they can also be cut.
20. The last process is sanding the surfaces so that any excess glue is removed and any irregularities removed.
21. We need test data for the Material Safety Data Sheet and for Underwriters' Laboratory: fire rating, impact resistance, bending, chemical resistance, strength to weight ratio and fiber to resin ratio.
22. We can use the same technology to build any form, such as a deck of a boat or the trunk of a car. Windmill blades for small windmills come to mind. The shapes can be irregular and can be contained for gluing with matching male and female molds of stiff material but clamped using the vacuum bag approach.
23. This approach uses a small carbon footprint and natural glues. There are no VOC's or any toxic substances. And the capital cost is low.
24. Soy stains and varnishes can be used to color and finish the outside of the panels and make them weather resistant. We can dose the soy glue with extract from the Cavassa leaf which has a natural pesticide.
25. Engineered wood could be in the form of a curved beam such as an arch for the inside of churches or other open space. It could be made into standard structural posts and beams. It can be drilled, sawed and nailed and screwed into, the same as any solid wood. It could be formed in the shape of barrel staves and used for barrels for making wine.
26. The small ends of the bamboo stalk can be used for plant stakes and trellises for plants. Bamboo would be great for grape arbors, kiosks and gazebos. The split bamboo could be used for mud and wattle construction. The leaves and leaf branches can be mixed into cob material or fed to livestock or added to the compost piles.

Vacuum Bagging Equipment and Techniques

Introduction


Vacuum bagging is a technique employed to create mechanical pressure on a laminate during its cure cycle. Pressurizing a composite lamination serves several functions. First, it removes trapped air between layers. Second, it compacts the fiber layers for efficient force transmission among fiber bundles and prevents shifting of fiber orientation during cure. Third, it reduces humidity. Finally, and most important, the vacuum bagging technique optimizes the fiber-to-resin ratio in the composite part. These advantages have for years enabled aerospace and racing industries to maximize the physical properties of advanced composite materials such as Graphite (carbon,) aramid, and epoxy.


What is Fiber-To-Resin Maximization and Why Is It Important?

The reason that composites are used increasingly is the strength-to-weight advantages that they offer. The key to obtaining these advantages is maximizing the fiber-to-resin ratio. The reinforcement (fiberglass, aramid Kevlar® graphite, etc. is not particularly strong in the textile state. As well, thermosetting resins such as polyester and epoxy are quite brittle if cured without reinforcement. If excess resin exists in the laminate, the laminate will have more of the properties of resin only. If too little resin exists, places where the reinforcement is dry will cause weak spots. To optimize the resin content, the entire reinforcement must be saturated with resin with as little excess as possible. The technique of “squeezing out” excess resin to obtain a maximized fiber-to-resin content is the theory of vacuum bagging.


How Much Resin Is Optimum?

Typically, a hand laminate uses in excess of 100% fabric weight by resin. A refined aerospace composite lamination will obtain as little as 40%. To determine the perfect combination for a given lamination is a sophisticated engineering problem beyond the scope of this brochure but a good target is 60% resin content. It is important to recognize that dry spots are “weaker” than resin-rich areas and maximization
of fiber-to-resin is relative to a “real-life” fabricator and his or her ability to improve the parts made.


What Do They Do That I Can’t Do?

Often companies who insist on maximum fiber-to-resin content use autoclaves to both elevate the temperature and pressure surrounding the part and/or mold while curing these high performance parts. An autoclave can elevate the pressure on a laminate two to three atmospheres. While this can be quite desirable, an autoclave is expensive and not readily available to the general public. This brochure assumes that a room cure, hand laminate is being improvedand that an autoclave is not available.


What Is An Atmosphere?

Vacuum bagging adds one atmosphere of pressure to a system. Although the technique is relatively inexpensive and easy to perform, it is worthwhile to understand the principle of atmospheric pressure and how it is measured so that you know if you have a problem with your system.
The atmosphere that surrounds the earth can be considered a reservoir of low pressure air. This low pressure air has weight which exerts a force that varies with temperature, humidity, and altitude. At sea level, that uniform pressure equals 14.7 psi (pounds per square inch) or 29.92 inches of mercury.(in. Hg or usually “Hg.) As its name implies, vacuum bagging is a technique which creates a vacuum; an airtight barrier between the open atmosphere and the closed system. When the vacuum bag is first sealed, air pressure on the both sides of the barrier equals that of atmospheric pressure. As air is removed from the closed system with a vacuum pump , pressure inside the bag decreases while the outside pressure remains at 14.7 PSI or approximately 30”Hg. A pressure differential develops between the closed system within the bag and the open atmosphere. It is this pressure differential which provides the uniform mechanical clamping force which is so desirable. Even complex shapes may be clamped at pressures approaching the 30” Hg figure of perfect vacuum.


Building a Vacuum System

The first step in creating a successful vacuum bagging system is to select a quality vacuum pump. The pumps are typically rated by the horsepower of the motor, type of pumping mechanism (rotary vane, diaphragm, piston, etc.,) the volume of air displaced in cubic feet per minute (CFM), and the maximum attainable vacuum pressure in inches of mercury (“Hg.) It is advisable to match the bag size, desired vacuum rate, and ultimate pressure with that of the pump for best results. While a smaller pump can often attain a desired vacuum level on a large system, it will take much longer to achieve that level. Also, if a leak is present in a system which exceeds the CFM rating of the pump, even a partial vacuum will be difficult to achieve. If a pump can not achieve full vacuum in less than five to eight minutes, the pump is probably too small. Determining the correct pump for an application is based on the square footage of the mold which it must surround. By squeezing as much air out of the bag as soon as possible before sealing the bag and applying the vacuum, the work of the pump can be greatly reduced.

Fittings and Connectors
Next, the pump must be connected to the bag itself. Although the configuration can be modified to suit a specific application, the basic connections are as shown in Diagram A. The pump is connected to the bag by tubing. The primary consideration is tubing selection is its ability to not collapse during vacuum. A connector between the tubing and the pump is required as well as a means of fitting the tubing into the bag. All connections must be as tight as possible to maintain the vacuum. We have selected a series of connectors which all fit properly and the remainder of this brochure will refer to our part numbers to explain the configurations. However, the principles can be applied with a variety of connectors and approaches.

The #891-A Vacuum Coupling creates a leak-free union between the bag and the tubing. The bag is prepared for insertion of the coupling by cutting a 1/2 inch “X” into the bag itself. The Vacuum Coupling body is pressed through the film from the inside. The 1/2” cut will expand to fit the 3/4” body of the fitting, but caution must be taken to ensure that it doesn’t tear further. The locknut is then threaded into position on the coupling body, and the union is complete. Any tears or gaps around the coupling must be plugged with sealant tape .

The #893 Vacuum Tubing can then be cut to fit from the pump to the vacuum coupling. This tubing fits the coupling as well as the fitting which is supplied with our pumps. If your tubing varies in size from either of these connections, you will have to modify your setup to ensure that you are not losing vacuum at either connection point.

Additional clamping at these and the following connections is usually not necessary up to 26” Hg. However, if these fittings are used at vacuum levels approaching 20” Hg, clamps may be necessary to prevent leaks. Adding A Vacuum Gauge
In addition to the most basic system described above, a vacuum gauge or a vacuum
gauge with a regulator may be installed in the system. The primary advantage
of using a vacuum gauge is the visual detection of leaks and the knowledge that they have been eliminated. Also, an accurate record of the vacuum pressures acquired during the fabrication of the part may be documented. Accurate recorded data of the minutes elapsed at each vacuum level will help you duplicate and hone your fabrication skills.

A vacuum gauge such as our #896 may be inserted into the system in three different ways. First and most simply, the gauge may be attached directly to the pump. Second, the gauge may be attached to the pump with vacuum relief and third, the gauge may be installed directly into the bag.

Attaching a Vacuum Gauge to the Pump Without Pressure Relief
The gauge may be mounted directly to the pump by using a connector such as our #898-A “T-Attachment Assembly “. This connector is supplied with 3 components: a T-Attachment, a brass nipple to connect to the pump and a hose barb to connect with the tubing. This . set-up permits the accurate measurement of the vacuum pressure throughout the entire system. There is a limitation to using only a gauge and a T-Attachment, however. Although you will be able to identify and plug leaks, you do not have any mechanism to reduce vacuum pressure. If you wish to adjust down from full vacuum, it is necessary to have a Bleedoff Valve Assembly.


Adding Vacuum Relief to the System

A Bleedoff Valve Assembly such as our #902-A would be installed instead of the T-Attachment Assembly. It is used as the connector for the Vacuum Gauge but allows you to adjust the vacuum in addition to reading the gauge. It is sometimes beneficial to apply only partial vacuum during the initial stage of the cure cycle. If full acuum is applied before the resin begins to gel, too much resin may be pulled from the laminate. This can leave a dry, resin starved surface which would be an inherent weak spot in the finished laminate. Partial vacuum is often desirable during this early phase for proper compaction of the composite layers, but full vacuum is delayed until the thin resin section begins to gel. Excess resin will still be bled off at this point. The #902 Bleedoff Valve Assembly is intended to be threaded directly to the vacuum pump using the attached brass fitting. The nylon hose barb exits from the port directly opposite the brass inlet port, and is the union for this vacuum tubing.. The vacuum gauge threads into the top of the bleedoff valve assembly. Teflon tape must be employed on all threaded joints to ensure a leak-free seal.


Installing a Vacuum Gauge Into the Bag

The final type of gauge attachment is to the bag itself. It is often beneficial to know the vacuumpressure within an individual bag. This is also the most accurate way to measure the pressure in the bag. Some pressure is lost in the system due to frictional air resistance, and the remote gauge location records only the pressure reaching the bag. In a system employing multiple bags, gauges can measure the pressures in each one. This is especially helpful when the bags are operating at different vacuum levels. Using a #909-A Two Way ShutoffValve , one can also control the airflow from pump to the bag. The gauge would then indicate if a leak was present, and when the valve needed to be opened again to maintain the desired pressure. To support and seal the gauge in the bag, a #910-A Thru-Bag Vacuum Connector is needed. The connector is inserted through the bag and tightened. Teflon Tape is placed on thethreads of the vacuum gauge and the gauge is threaded to the connector.


Multiple Bag or Multiple Port Applications

It is possible to have more than one bag at a time working from a single pump. It is also possible (although not usually necessary) to have more than one port into a single bag. In order to direct more than one piece of tubing from a single pump, a #906-A “T”-Fitting or #907-A Equal Angle “Y” Fitting is needed. The fitting is inserted between the pump and the tubing connections. Multiple vacuum couplings, gauges, etc. would complete the setup. The Vacuum Bagging Process
A typical wet-laminate and corresponding female mold may be placed inside a vacuum bagging assembly after certain measures have been taken to ensure its removal. First, a release film or peel-ply material must be draped over any portion in contact with the resin. Leave excess folds of loose release material in any deep or hard to reach portions of the mold to guarantee that the material will not bridge or be pulled taught across the corners. A gap would leave an air pocket below the material. If the part is too complex to have the release draped evenly, sections may be cut and applied individually to the contours. However, the layers must overlap at all joints to ensure adequate protection. The type of release layer varies depending upon the desired surface texture and resin content that the component is to have. If the inside surface is to be painted or have another layer bonded to it, a peel-ply layer would be utilized. Peel-ply will also allow !n completely surround both the mold and the laminate. If the part is small enough, it can simply be inserted into a tube type polyethylene bag, the vacuum coupling fitted, and the two ends sealed with sealant tape. If the part is too large for an existing tube type bag, you can make your own by joining two sheets of bagging film on three edges, inserting the part and vacuum coupling and then sealing the last edge. If a bag this large must be constructed, costs may warrant sealing the bag directly to the mold flange.


Bag Technique: Sealing to Mold Flange

If a part is initially designed to be vacuum formed, the mold can be built to aid in the process. Essentially, a three to five inch flange may be constructed around the entire perimeter of the mold. This makes a solid base for the application of sealant tape. When sealant tape is attached to the flange of a mold, a single-sided bagging film may be employed. The other airtight barrier in this system is the mold itself. Just like the release ply and breather material, the bagging film must reach the bottom of all troughs and fully into all corners. It is this layer which actually applies the pressure from the outside atmosphere. Even when all previous layers were applied correctly, if this bagging film bridges a gap, no pressure will be applied to that area of the part. While stretchable bagging films are in production use, they are no substitute for adequate forethought and preparation of tucks and pleats in the bagging material. A tuck or a pleat is a looped gathering of bagging material where a sharp contour or edge is encountered. Sealant tape must be used to fill the loop. The pleat extends perpendicular to the path of the flange, and three to six inches ofpleated material will generally give the necessary clearance. Bagging Technique: Surface Bagging.

The final form is called surface bagging. This is used when laminating on a flat board-like surface, or blending repairs on gently curved surfaces such as leading edges of aircraft wings. Quite simply, the part is assembled or repaired following the predetermined laminating schedule, and the peel-ply , and breather are added. Around the perimeter of the repair, sealant tape is affixed to the base structure with an inch overlap at all four corners. Next the 1/2” “X” is cut in the bagging film, and the vacuum coupling is inserted. The paper strip is removed from one line of the sealant tape at a time, and the bag is attached to the exposed sealant. Once the bag is in place, vacuum is applied.


Conclusion

Vacuum bagging does not have to be an extremely complex process. A fabricator who would like to improve his strength-to-weight will generally find great benefit from a simple vacuum bag constructions. As the process is refined, the projects become more complex or as larger parts are made, the techniques can become quite elaborate. Unfortunately, the elaborate techniques have scared a number of people away from using this helpful approach to improving their handlaminates.

We encourage you to select the right pump, to ensure that all of your components will properly fit together and to practice with some simple parts to minimize the cost of any “Learning Curve” mistakes.