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 »

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 »

How do you create the vacuum?
My already completed 'Lil Bit'. A Martens Goosen V12 set up to sail me to the fishing holes.
Currently working on making a Helms 24 our coastal cruiser.
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 »

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 »

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 »

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 »

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.
My already completed 'Lil Bit'. A Martens Goosen V12 set up to sail me to the fishing holes.
Currently working on making a Helms 24 our coastal cruiser.
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 »

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 »

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 »

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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Re: Poor Man's Vacuum Bagging By Evan Gatehouse

Post by Matt Gent »

Just happened to trip across this thread.

I've done similar to how Evan proposes, and I borrowed, and then built, one of the Joe-woodworker compressor-driven venturi setups.

The joe-woodworker thing works fine, and if you get a good seal the compressor doesn't cycle that much. That's a big IF though, depending on your setup. I have been using it to re-core the running surface of speed boats I'm rebuilding, so the bag needs to seal to old glass that I may have ground on or even spilt some epoxy drips. I'm about 50/50 on getting a good seal, and the venturi setup doesn't draw enough volume to really help you trouble-shoot. I'd feel pretty good about it on a flat vacuum table (or any table/jig with a nice clean perimeter) making new parts.

The yellow tape sold for vacuum bagging from the various suppliers works fantastic, but it is expensive. I've also used the stretchy bag material (Stretch-lon?), which works well but also expensive.

I was bagging down Corecell A500, which is a high-performance SAN foam. It comes perforated so you can see where you are getting the resin mix drawing up through. That core is also expensive.

I've basically stopped using it unless I'm sure I can have a nice, clean, simple perimeter to apply the tape. For layups in warm FL it is too much of a circus trying to get the bag to seal before the resin gels over.

Anyone in South FL is welcome to borrow the vacuum setup if you want to give it a go.

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