I was wondering if anyone has any plans/ideas for making a vacuum pump for doing wings and tails and such. I’m not looking for a ‘production’ model or anything just something for a guys work shop that doesn’t cost an arm and a leg.

Thanks.

Daven made a dandy pump from a old window A/C unit that someone dumped at Grassfield.

I think Dave has a thread on it from his wing discussion

Jerry B. made that pump. He's the guy, talk to him on Saturday.

Sounds good thanks for the info.....

Harbor Freight sells one for $15
Scott

Is this the one your talking about Scott?

http://www.harborfreight.com/cpi/cta...temnumber=3952

If it can pull 28 oz of mercury, thats a lot. I would assume you would need to add a regulator of some sort?

Those air powered ones are noisy scuts. You need a 60 gallon air compressor to run them.

You will have to spend some money. Aerospace Composites sells a starter kit with everything you need to do basic vacuum bagging. It costs about $120.00.

Or, you can build your own.

Old Refrigerator compressor,---Free
Vacuum switch---------------------$40.00 app
Vacuum gauge---------------------$30.00 app
Reservoir, old juice can-----------Free
Assorted fittings--------------------$10.00
Time, two hours--------------------Free.

The pump in the kit from aerospace is designed for continuous running and will pull a vacuum of about 6hg. 6hg is equivalent to app. 3lbs/sq in. On a 500 sq in wing. that is pressing 1500# on the top and on the bottom. So that is like putting a 3000 # weight on the wing. If you go much above 10hg white foam will start to crush. If a home built unit is built a vacuum switch is essential to control the vacuum.

A while ago there was post where somebody used a hand vacuum pump from an autoparts store. I think it is used to check air conditioning systems. That might be an inexpensive alternative. The bag must be totaly airtight for this method to work, or you will up in the middle of the night restoring vacuum loss.

Anybody got other ideas?

Ed S

How?

A demeaning quote from one of High plains other enlightening threads on the same subject.

Figure out the above Bob and I will see if it is worthwile trying to explain "How?"


Ed S

b of course Mr. Ed.

If you place 1500 lbs. on the top skin, you also have that same force on the bottom skin. But not 3000 lbs. Same thing as your 3 lbs./sq. in.

Though with the vaccum, the force is normal to the surface.

I'd tend to agree with Bob, as scary as that is. Think of it this way. If you simply sealed a single sheet of plastic bag material around the edge of a 500 square inch table and pulled a 6hg vacuum, you'd have approximately 1500 lbs. Why and how would the same 6hg double just because the bag is on both sides? I suppose if you vacuumed a cube to 6hg with 500 square inch sides, it would be like using 9000 lbs?
GS

As in a previous similar post, the only reason I responded was to offer help and advice to somebody who wanted to get started in vacuum bagging. No more, no less.

The time spent by others questioning these efforts would be better used offering their own help and advice. Something I have yet to see. I will spend no more time on this subject.


diggs 74,
I built my own unit. If you require more information from those of us prepared to give it, email me, I will be glad to give it.



Ed S

And to think I thought I was asking a fairly straight forward question.... Anyway, thank you all for your input, it is much appreciated. I'm going to try to construct my own until I get frustrated and just buy one.

Thanks again.

Ed,
I agree that bagging is still by far the best way to sheet a foam core, therefore I didn't feel the need to respond any earlier. I also tend to agree with farmer Bob in that 6hg isn't the same as putting 3000 lbs on a wing, but is the same as 1500. Really, when it comes to sheeting wings 1500 is way more weight than I'd care to manually stack on a wing, so if I can get the same with a vacuum, that's what I'm doing.
GS