After doing the cinder block method of sheeting wing cores for a few years , I'm thinking of buying a vacuum bagging system and chucking the cinder blocks. So, I'm looking for some recommendations...I build most 1/4 scale (72"+) with an eye toward perhaps a little bigger birds one day. ACP (Aerospace Composite Products) offers two systems, one with a preset pump (7-8" Hg) and another with a variable pump (up to 20" Hg) with about a $200 difference in price. CST (The Composite Store) apparently only offers the higher end system (priced about the same as ACP's).

Some questions:

- Do I need the higher end vacuum pump or will the smaller preset unit do what I need?
- Anyone know of additional sources of vacuum bagging systems besides ACP and CST? Is there an industrial source for vacuum pumpts that might be cheaper?
- Perhaps a stupid question, but will polyurethane glues cure in a vacuum (I know they need moisture, but I don't know about air)?
- Can I use this system to vacuum-form plastic such as for home-made canopies or do I need lower vacuum than for wing sheeting?

Thanks in advance for any suggestions or input!

I assembled my own vacuum bagging system after seeing a couple in our area. I bought a used Gast vacuum pump for $75, a couple of check valves (I only needed one), a vacuum guage, a vacuum switch, and some tubing from the hardware store. I also built a reservior out of 3" PVC pipe with a couple of endcaps. The switch wasn't cheap at about $30 but everything else was and I doubt that I have more than $125 in it. It works great up to about 20" of vacuum which is more than enough to crush white beaded foam and still sufficient for the denser ping and blue foams. Whether you build one or buy your own, it is well worth the effort. It will end delams (as long as you spread your adhesive evenly) and it is actually easy to use.

As far as supplies go, I really like the vacuum bagging material that comes in a tube, it is easy to put a sheeted wing into the tube and seal the ends with clips. It is very easy to get a good seal using those types of bags. Those 2 items are worth the cost. For saving money, it is easy to use paper towels as breather cloth around the perimeter of the item being bagged. I bought some peel ply but haven't used it yet.

I've seen some pretty good deals on vacuum pumps on E-bay.

I've never used polyurethane glue for sheeting a wing, I stick with epoxy. It has a proven track record with me. I have heard of people successfully using Probond though.

Good luck,

Kevin

Ditto the build your own method. There is nothing to it. I used a refrigerator compressor, an empty 20lb freon bottle for a reservoir, an auto vacuum gage, and an industrial adjustable vacuum switch. The vacuum switch was the only thing I really had to seek out and purchase. Use heavy polyethylene sheeting and pliable caulking to seal the edges.

Vince

The do-it-yourself method seems a pretty good option. Where can I find these parts, particularly the switch since it seems to be the hardest item to find? Are old refrigerator compressors and reserviors easy to come by (seems a waste to buy a new fridge for the parts )?

Thanks for the feedback!

I built my own out of a refrigerator compressor, a schedule 80 PVC chamber. The parts were picked up from an old surplus shop in San Jose, Ca. (Including the adjustable vacuum switch and solenoid/check valve)

I did purchase a few parts from ASC in San Leandro, CA. (Tube/sleeve bag material, peel ply, hose, hose/bag fitting, bag sealing clips, and vaccum gague.) They are a top notch shop in my book. Professional and quick. Prices seemed pretty reasonable. I wouldn' t hesitate to deal with them again.

I will post a few pictures of my system later tonight when I get home.

It took me less than a day to assemble the entire system.

Everything combined was under $120.00.

Ted

TRP, pics would be great! I figured I can buy the bagging supplies (bags, breather cloth, bag clips, etc.) from one of the stores, but if I can make my own pump system, I'll do that instead of the $200+ pump these guys offer.

Thanks!

Here is pic of my home brew vacuum system. The pump is an old refrigerator compressor. The gage is a cheap auto vacuum gage. The adjustable vacuum switch is from a United Electric industrial vacuum switch.

Vince

Here is a pic of my vacuum reservoir, it's just an empty 50lb freon cylinder.

Vince

A close up of the switch and gage.

Vince

Hi Vince, thanks for the pics...not to complain, but the last picture didn't get attached for some reason. Very helpful and I'd like to see the switch and gauge close up. Thanks again!

Here is a shot of my system from the front...

Here is a shot of my home made system from the back..

In this shot you can see the on off switch. When the system is turned on it will operate to the pressure you have dialed in on the pressure switch (funny thing with the lexan box on top of it.) The pressure switch then shuts off the pump and closes the check valve / solenoid. Once the pressure drops below a desired setting... the whole thing will kick back on and continue to operate until the desired setting has been reached again.

The the entire process starts over again - for as long as you leave the system 'on'.

The system has been tested and so far it looses about an inch of pressure for every three hours it is in use. Pretty respectable - I should track down the leak.... but it only cycles every 5 or 6 hours (give or take) so I am in no hurry.

Here is a shot from the side...and a bit behind it.

You can see the coil of rubber hose that leads out to the bag and bag fitting.

Here is a shot of the other side.

You can see the solenoid / check valve. It had an extra port that I didn't need.. so I capped it off. I suspect this is where my leak resides. I don't think the screw I plugged the hole with was big enough

Here is another shot..

This shot shows the bagging material (clear-ish colored roll), the peel ply (white rectangle), and the clips that seal the bag(s).

In the shots you can also see that I mounted the pump on some solid rubber mat to keep the vibration down to a minimum. I also mounted the entire system on the solid mdf and screwed 8 rubber feet on the board.

The end caps on the tank are schedule 40 and the tank body is schedule 80 pvc. I mounted the 'tank' to the board using some 1 by stock that I cut to form a saddle so it rests in there really nice. I then epoxied the tank to the saddle and screwed the saddle to the base from the underside.

I have since cut two handles in the base so I can pick up and move the entire contraption with ease.

It shouldn't take more than 3 or 4 hours to assemble your own system once you have all the materials together.

Special thanks to Luvara racing and Gordon McSomething or other for help with locating some of the materials to complete this project.

TRP

TRP, great pics! This is very helpful...I took the suggestion of trying ebay and picked up a never-used (or so it was described) Gast 1/10HP vacuum pump for $60 (from the pics it looks a lot like yours).

The reservoir tank is straightforward, as is the plumbing, but where can I find a vacuum gage, vacuum switch and check valve on the cheap? Any specific brands or part numbers I can search for?

Thanks again for all of the help!

George Spar of Aerospace Compositescan sell you a vacuum switch for your system.

Great system TRP, looks much more professional than mine.

Vince

Thanks!

I would suggest Aero Space composites for all your equipment needs. The vaccum switch will be like 30.00 and the gage will be another 20.00 or so. The rest of the stuff you can pick up at O.S.H. or Home Depot.

Good Luck,
TRP

Hey guys,
If you are using a continuous duty vacuum pump with a built in regulator do you need a reservoir tank? Can't you just set the vacuum and let the pump run?

I have a system similar to what has been presented above. I got my vacuum pump at an RC auction for real cheap; got the vacuum switch on eBay for about what APC charges, so no great bargain there; got three vacuum gauges off eBay for like $5 apiece, only because no one else was bidding at the time; 4" pvc pipe w/ capped ends reservoir; fittings & tubing from mscdirect.com, which has a pretty good industrial supplies website, good service, fast shipping, more convenient than getting stuck in traffic to go to the store.

Studying the ACP site a few nights ago, I almost think you could do without the vacuum switch and just use their APC relief valve, which closes at 8 psi, opens at 10 psi, values for white foam, which is all I ever work with. The relief valve is simpler and cheaper than the vacuum switch.

I have not found a better source than ACP for the usual supplies, bag fitting, seals, etc. They're good people to deal with imo. Get their video if all this is new to you.