An Inexpensive Vacuum System Setup

For those people who have been directed here by the postings on soaring@airage.com, the following is my current setup. There are many people who have other ways to improve upon the setup, so please let us all know. Thanks.

The Power Supply (inexpensive) was obtained from HOSFELT Electronics, 2700 Sunset Blvd. Steubenville, OH 43952, 800-524-6464.
Part Number 56-377 (pn 430-001492) 24V 1A Model Acc-T5724A was for the pumps shown, however 9V versions are available. Price Approx $7 each. (order a second for a friend, shipping is the real cost)

Vacuum Switch Source:
Part Number: F-4200-X30, Specify Vacuum switch
Adjustment range: min 1.5" Hg to 30" Hg
Deadband: Typ.: 2" Hg, Max: 3" Hg
(I found mine to be less than 2" HG)
Current rating: 15A, SPDT
Use 1/8-27 NPT mount for piping connections
Cost: Approx $18.70 each (old price) plus S&H (order a second for a friend, shipping is the real cost.)
NOR-CAL Controls, Inc. 1400 Coleman Avenue, Suite H12, Santa Clara, CA 95050, 800-233-2013, 408-727-5756
DataSheet Link: SwitchInfo.jpg

Pump Source: (The pumps pictured were for a scientific instrument and were discarded because they did not reach their rated pressure. Since then I have located an inexpensive diaphram pump with a plastic housing. When rigged in tandem they should pull the required 18" max vac pressure.)

Contact : Part Number: 70120012.
Made by VDO of Germany for ASF Thomas Company. Part#
These are about 4 1/2 L X 3 H black enclosed case air pump. The outlet fitting has a removable protective cap and is designed for 1/4 Dia. hoses. Operates from about 12VDC up to 30VDC but is designed for 24VDC. Very nice precision made unit. Brand new Prime!
G9927 $8.95 ea.
The Electronic Goldmine, PO Box 5408, Scottsdale, AZ 85261
Telephone 1-800-445-0697, FAX 480-661-8259
General Information: goldmine-elec@goldmine-elec.com
www.goldmine-elec.com
Note: May be out of stock.

The vacuum system above uses two diaphram pumps in series and pulls 18". Between the pumps and the valves is an aquarium sealing bladder to prevent the air from flowing into the valve system. The bladder whistles as air is pulled through it. I have two screw valves for two separate wing panels. The valves, and all junction pieces were obtained from the local Hardware store. The pressure on/off valve is on the end behind to the switches. The pumps run on 24V so what you see is a tranformer for power. The black tank is from approx 6" PVC sewer pipe (thick wall), with endcaps. The pipe is cheap, the endcaps are expensive. You can seal all junctions with PVC cement. The vacuum gauge was obtained locally and measures in inches of Hg. The above system hangs from above my workbench so that I have easy access when first applying the vacuum. This is not a heavy duty system. Rather for better volume and speed of pumping you should try to get a small refrigerator pump or a pump from a manufacturer.



This shows some pieces for a vacuum system which can be obtained locally. The hose connector on the right was obtained from our standard vacuum bagging sources. I chose the other parts to make sure the hose does not come off the bag. These suggestions are from Oliver Leider (President of the Sierra Silent Soarers) and are passed on here.

The Hose connectors on the left are from a local Pep Boys auto supplier and are tire valve stems for mag typ wheels, relatively inexpensive. A cross is made in the flat end using a dremel tuff grind disk, and the edges smoothed with fine emory paper, to do two things: 1) to help you seal the gaskets with the bagging material (a screwdriver and wrench) and 2) to permit air to pass to the pumps, preventing the bag from sealing the stem closed when the vacuum is applied. The large metal washers were obtained at a local hardware store. The orange/red washers are rubber, and you can cut these from an old tire tube. The hose clamps were removed from hoses on cars at the local junkyard, and perhaps can be obtained from a auto parts store or A/C car shop. The connector for the valve stem which then connects to the teflon hose to the pump system is from a can of "repair-a-flat" for approx $2.49. Just cut off the hose connector and toss the can carefully. There are many ways to clamps a vacuum bag, from tubes of sealant, to the fancy clamps offered for $3 each by vacuum bag suppliers. On a recommendation from someone on Soaring@airage.com, I finally found the clamps displayed. These are for creating a dead-air space around a house window with plastic. They have a C-groove and rubber insert which is easily removed. They come in long lengths, 4ft-5ft, and are relatively inexpensive. You can get these at the local Supply One, Home Depot, or Eagle Hardware. The clamp strips are used to line window sills. You double stick tape them around the window. You can then stretch a polyethylene film over the window to create a trapped air space. This is especially useful to those who live in very cold areas, as it prevents heat loss. They are available in lengths from 3 ft to 5 ft. I have an assortment I keep around. I gave you the description since the Hardware people will look at you funny as you try to describe what you are looking for.

When I attach the valve stem, washers and rubber gaskets on the vacuum bag, I seal the joints with some silicone sealant. It seals the junction well, and is easily removed by rubbing. Silicone makes an excellent gasket. Similiarly, when I place the tygon vacuum tube inside the tygon tubing for the valve stem connection, I use silicone sealant to prevent leakage while using twisted wire to clamp the tygon over the tlefon tubing.

Bagging Materials:
Bagging materials can be obtained from CST or ACP, whichever your preference. Since I use 18" wide bag tubing, I FOUND it difficult for me to slide the complete wet layup of mylars, FG, and cores inside the bag, and still have easy access to position the breather cloth etc. This was a problem AND there is a solution!!!

Solution: Rather than slide the wing in from the ends, I seal both ends of the tube with a Sealing machine. You can use an iron to seal the ends if you want. At this point you have a 18" bag sealed at both ends. I then cut the tube open from the side and essentially make a Taco of the bag. The max length of the bag (and wing that can be bagged) is just under 60" (or 5 ft). The reason is that the bag clamps I use above, are only 5 ft in length. I do my layup of the glass, core etc, then just slide it into the bag from the side. I then adjust the breather cloth, and make sure all things are in position, then close the side of the bag off with the clamp. I then pull the vacuum. If I need to release the vacuum, and re-adjust any parts, it is easily done, and easily reached. Re-clamping and applying vacuum is easy. Just make sure there are no creases of the bag in the clamps as this may cause leaks. I am going to try 4 to 6 mil polyethylene dropcloth plastic, folded over, sealed and clamped in the same way. It many be cheaper, and easier to obtain for use with wider wing panels.

I have used this method to bag my Micro HLG wings for my Itch, panels for my 110" Open class ship, and also my Speed 280 flying wings. I also use smaller bags for my Itch stabs and rudders.

I'll try to present pictures the next time I do my bagging.

TO ALL: This has been prepared quickly. Please let me know if this helps.

E-mail: chris@spieltek.com