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Old 11-08-2012, 05:02 PM   #1
mugget

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Lightbulb Cozy Girrrls LoVac - low pressure vacuum bagging

I have been taking a bit of a look into the homebuilt aircraft community, I have found some interesting ideas and picked up some good tips from what I've been able to find so far.

More interesting is the idea of low vacuum bagging. I just wanted to see what people's thoughts are on this: http://www.cozygirrrl.com/lovac.htm

To summarise some of the benefits:
  • No bubbles or air
  • lighter parts
  • highly conformal lay-ups on complex parts with sharp edges and tight radius edges
  • Most importantly - minimal cost in disposable supplies

They do say that this is only suited to make some conventional lay-ups better, so it's not an option for certain parts, and not an all-inclusive solution.

Basically the idea is to use a low vacuum pump, they use a linear piston machine that pulls maximum -9.84 in.Hg at 7L/min. They use a ShopVac to pull the majority of air out before attaching the LoVac.

Also on the consumables side - it looks like they use pallet wrap instead of any kind of vacuum bag, and instead of breather they use... paper towels! So yeah, they're not spending much on consumables!

Another important point is that they use a slow cure epoxy which is warmed so that it flows really well and is thin.

From what I can see, they remove the vacuum once it gets to the green stage (after the "chewing gum" stage) and then remove the paper towels while they still come off easily.

So - for a low cost home DIY solution, it seems fairly good to me.

I've seen mention of a linear piston vacuum pump here before, and after looking into it some more it seems like a really good option for vacuum bagging. There is a more powerful -23 in.Hg model that I have seen for $80 plus shipping, I'm wondering if that would do an even better job? The larger pump may be suited to a more "traditional" bagging method, though I'm not sure how that would go if the paper towel idea was used?

I'm interested to hear what you folks think about this? Or even better - has anyone tried the LoVac method?
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Old 11-09-2012, 06:03 AM   #2
AaronVenable

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And they're building airplanes!

I'm a big proponent in sustainability, and that part of their "experiment" caught my attention. But as I read on, they are not using less consumables at all. They've replaced bagging materials with stuff they found under their sink, the clearance isle at walmart and from the warehouse at work.

There are some reusable silicon bag solutions that will cut down on long term production costs and materials usage. I've also seen reusable infusion manifolds.

What percentage of cost are you planning on avoiding by using this method?
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Old 11-09-2012, 11:02 PM   #3
herman

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Building airplanes on the cheap. It can't get any worse...

I have never built an airplane, but if I would, I would like a detailed laminate plan, including thicknesses (stiffness, buckling) or Vf to be reached.

If these guys want to infuse, I would suggest a LBA approved infusion resin. They are wet bagging, and the (presumably) L285 resin is nice enough to hand laminate in good quality, even without heating. A temperature of 20-25 degrees C is recommended though.
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Old 11-10-2012, 01:05 AM   #4
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:lol:

Okay so it looks like no one here is into that kind of thing...

I'm not planning on doing any vacuum stuff, the "DIY/experimental" aspect just caught my attention and I was interested to hear some knowledgeable opinions. I give them props just for trying it out, what really surprised me was that it seems to work for them...

Whether or not they use less consumables, I think the main point was that their consumables cost is much less. I don't know what the cheapest vacuum bagging film costs, but I think it's safe to say that it would be much more than $100 for 150mē. And that's just one single item...

The site looks quite old, maybe the availability and cost of consumables for home/DIY builders has improved since then.
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Old 11-10-2012, 09:55 AM   #5
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Recently bought a roll of bag film from airtech. It was right around $700 for 600 sq meters.
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Old 11-11-2012, 12:47 AM   #6
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Hmm... interesting to know!
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Old 11-11-2012, 04:57 AM   #7
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Which exact type was it? (material, thickness, width, length)
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