Poor Man's Vacuum Bagging By Evan Gatehouse

Post any and all methods for doing things here, if you think you have a good method, that you don't see most builders using
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Poor Man's Vacuum Bagging By Evan Gatehouse

Post by BB Sig » Wed Jun 21, 2017 2:08 pm

Evan_Gatehouse wrote:
Wed Jun 21, 2017 1:14 pm
Hi,

I'm a designer of some of the bateau boats. I've also built some big vacuum bagged foam cored panels for the bridgedeck of my catamaran - about 8'x8' were laid up in one shot.

1. Cut up your foam for the hull
2. Do a test layup with some of the scrap foam first. Say 18-24"' square or so.
3. Don't use too much bag pressure. I used about 1/2 atmosphere and that was fine. Lots more vacuum and you suck the resin out, leaving a dry laminate. But this depends on the particular resin you use - slow resins less vacuum. hot day - more vacuum to get it bonded before resin gels.
4. Use a resin trap. I used a mason jar with holes in the lid.
5. I used cheap fabric store ripstop nylon for peel ply. Works fine but do clean the resulting surface afterward before bonding/painting as the fabric may have contaminents from the weaving process. Ugly colors are usually discounted :)
6. I used cheap polyester batting about 1/2" thick from the fabric store for the breather/bleeder layer. Worked fine
7. I used 4 mil builders plastic for the bag. Not very stretchy but o.k. Don't buy the very cheapest as it may have holes and drive you crazy
8. I used rolls of butyl mastic tape from Home Despot - used to stick windows in. Works quite well at sealing.

I don't think you have to use the fancy bagging materials sold by composite suppliers for most applications.
Posting just in case someone else needs the info.



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Re: Poor Man's Vacuum Bagging By Evan Gatehouse

Post by Jaysen » Wed Jun 21, 2017 2:09 pm

How do you create the vacuum?
Jaysen wrote:
Mon Apr 29, 2019 3:44 pm
I tried to say something but God thought I was wrong and filled my mouth with saltwater. I kept my pie hole shut after that.

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Re: Poor Man's Vacuum Bagging By Evan Gatehouse

Post by terrulian » Wed Jun 21, 2017 2:27 pm

Evan, first a poor man's CNC machine, now a poor man's vacuum bagging method. What is it with you and poverty?
I actually appreciate the ingenuity at least as much as the economy.
In any case, thanks, I'll remember that in my next life when I build another boat. :help: :D
Tony
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Re: Poor Man's Vacuum Bagging By Evan Gatehouse

Post by Evan_Gatehouse » Wed Jun 21, 2017 2:29 pm

You need a vacuum pump. Doesn't have to be new, or very big. Ebay has tons of them. Look for at least 2 or 3 CFM by a reputable maker.

Something like this:

https://www.ebay.com/p/JB-Industries-Dv ... 2234683384

After you are done the project you can probably sell it for what you paid for it or close to. These types of pumps are used in HVAC air conditioning repair so you can probably also find them locally on Craigslist too.

You will need a vacuum gauge Tee'd into the pump inlet to measure how much vacuum you are pulling. Some 1/4" nylon tubing and little brass compression tubing fittings to connect to the pump.
designer: FB11/GV10,11,13/ HMD18/
SK17,MM21/MT24

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Re: Poor Man's Vacuum Bagging By Evan Gatehouse

Post by Evan_Gatehouse » Wed Jun 21, 2017 2:38 pm

I forgot to add: Really nice how to article I helped write with my wife for DIY Boat magazine:

http://www.dianeselkirk.com/PDFs/DIY%20 ... Basics.pdf
designer: FB11/GV10,11,13/ HMD18/
SK17,MM21/MT24

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Re: Poor Man's Vacuum Bagging By Evan Gatehouse

Post by Jaysen » Wed Jun 21, 2017 2:39 pm

That seems like the most expensive parts so far...

Your timing is just about perfect. I've been thinking about how to make my "better" dagger and rudder for Lil Bit and was thinking that vac over a form would be easier than a compression mold. I must now think.
Jaysen wrote:
Mon Apr 29, 2019 3:44 pm
I tried to say something but God thought I was wrong and filled my mouth with saltwater. I kept my pie hole shut after that.

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Re: Poor Man's Vacuum Bagging By Evan Gatehouse

Post by Netpackrat » Wed Mar 20, 2019 5:00 pm

When I went to A&P school, in the composites class we did some vacuum bagging, but instead of a regular pump, they had made up some venturi units from pipe fittings that would draw a vacuum when connected to shop air. It was a much more efficient means of allowing a class full of students to all do their vacuum bagged projects at the same time compared to the school purchasing many pumps. Of course you need a decent source of compressed air, but if you already have that, then it might be a better way to go than buying a pump.

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Re: Poor Man's Vacuum Bagging By Evan Gatehouse

Post by Knottybuoyz » Thu Mar 21, 2019 8:31 am

I've actually not done any vacuum baggging but a few small resin infusions projects. Have used both a vacuum generator (air compressor powered) and a Robinair HVAC vacuum pump.

This is a common commercially available venturi vacuum generator. It is capable of producing a good vacuum for bagging or infusion but will require a fairly large (5 CFM or better) air compressor.

Image

My choice was to put together a vacuum system that was more reliable, quieter and not required to run constantly. The Robinair 5 CFM pump came off of eBay for about @175 brand new. The rest of the kit is a vacuum control system from https://www.joewoodworker.com/docs/ProjectEVS.pdf.

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You can see our latest small infusion project, our rudder, here.... https://youtu.be/62jOR77qYo4

Assembling both were nice little projects and great tools to have around when you need them.

Cheers fellas.

Rick
Yours Aye! Rick
"It's not the boat "you built" until you've sworn at it, bled on it, sweated over it, cried beside it and then threatened to haul the POS outside and burn it!"

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Re: Poor Man's Vacuum Bagging By Evan Gatehouse

Post by silentneko » Thu Mar 21, 2019 8:47 am

To rich for my blood, lol. I've used this unit in the past hooked to a 2.5 gallon compressor to redo several old ac systems. It wored great. I'd go this route when it's my turn to bag.

https://m.harborfreight.com/air-vacuum- ... 96677.html
Built: 15ft Skiff, 16ft Skiff, Modified Cheap Canoe.....FS17 coming soon!

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