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 Post subject: Vacuum resin infusion
PostPosted: Wed Dec 24, 2008 11:44 pm 
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Joined: Tue Nov 22, 2005 10:57 pm
Posts: 623
I would like to try this method on my new contruction, have however a couple of doubds about the correct setup for double sided infusion arround a balsa core.
If anybody could point me in the right direction or give me a link to a site explaing it in some detail I would be greatful.


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 Post subject: Re: Vacuum resin infusion
PostPosted: Thu Dec 25, 2008 2:48 am 
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Joined: Wed Nov 20, 2002 1:00 am
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Location: rhode island
this may help:
fiberglast has a vacuum infusion tutorial link at the bottom of the list.

http://www.fibreglast.com/contentpages- ... r-286.html


Its a cool process but definitely not 'plug and play'
I'm no expert but the few times i have built parts this way i needed a couple of test runs to get all of the bugs worked out.

When you do it for real, its all or nothing once you open the valve.
so you definitely do not want to throw out anything expensive due to unforseen mistakes.

I do believe you can get very good laminate properties, but all the up front labor to make a one shot success may not be worth it.

but it is fun, when it works.
-bill


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 Post subject: Re: Vacuum resin infusion
PostPosted: Sat Dec 27, 2008 1:10 am 
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Thanks for the hint, but there is no mention of how to prepare the core for the infusion. I am concened about keeping a stedy and even resin flow on both sides of the core.
Also, it is not possible to get specialized supplies here, so I have to impovise. For example, instead of commercially available peel ply I use common 100% polyesther 2oz plain weave fabric to which I apply an also improvised release agent (floor wax). Hins on also improvizesd flow media might be helpful


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 Post subject: Re: Vacuum resin infusion
PostPosted: Tue Dec 30, 2008 9:21 pm 
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Joined: Mon Mar 05, 2007 8:49 pm
Posts: 31
Location: Helsinki, Finland
This is how I made my board with vacuum infusion:
http://www.youtube.com/watch?v=k1v9sFfufQc

From top to bottom:
glass (160g/m2)
glass
carbon (10 cm wide strips)
glass
Airex core 5-10 mm (two 5 mm sheets bonded with epoxy and microspheres)
glass (going over the edge to the top side)
carbon
glass
Aramid (going over the edge to the top side)

Around the core and fibers:
Peel ply
Vacuum bag
There was no flow media, which would have made the process faster.

The epoxy was SP: Prime 20LV Epoxy Infusion System with Slow hardener.
It is really runny and slow curing.

I drilled 1,5 mm holes in 3 cm intervals from tip to tail to make the epoxy go to the base side. It seemed to work ok. Resin inlet is in the center, vacuum is from the sides.

Curing was done in sauna: 5h in 70-90C and board was left there over night. Board was still attached to the rocker table.

I didn't prepare the Airex pvc foam core in any way before the infusion process. It is a bit porous with closed cells. I haven't worked with balsa, but I don't think you need to prepare it. Maybe sanding with rough paper along the infusion direction might help.

The shop I bought the the materials was out of flow media. I did some testing on the resin flow before doing the board. Small grooves (~1mm*1mm) enhanced the resin flow a lot, but I ended up not to do that. I also bought some mosquito net which I think might have worked in helping the infusion but I didn't use that either. If the epoxy wasn't so runny, the infusion process wouldn't have worked without flow media.


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 Post subject: Re: Vacuum resin infusion
PostPosted: Tue Dec 30, 2008 11:05 pm 
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Joined: Wed Nov 20, 2002 1:00 am
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Location: rhode island
sorry for the non-answer.

you can buy core material that comes 'scored' to assist resin flow.
as mentioned above some type of flow media (loose mesh) can also help distribute the resin.

however, the peel ply (if used) and the glass cloth itself will also give you a reliable flow path.
much of the decision regarding the need to enhance flow rates may depend on the viscosity and working tme of the resin being used.
vinylesters can be found with low viscosity for easy pumping.
many epoxies are very viscous but have a long pot life. you can even get them with low temp oven cure to max out the working time.

careful placement of supply and return tubes to maintain uniform flow paths of equal distance (equal resistance) through the cloth will help alot.

my parts did not require any flow media other than supply tubing.
i 'pumped' a viscous epoxy through 12" of glass (3 plys of 6oz).
it took close to 40 minutes to completely empregnate the cloth , but the process was quite uniform.
i'm not saying this is the answer for you, but with a bit of trial and error you'll find you have lots of choices.


injecting the resin from both sides should negate the need for holes in the core.
i know you normally use balsa planks. but end-grain balsa (blocks and scrim) should help flow rates if needed.

regards,
-bill


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 Post subject: Re: Vacuum resin infusion
PostPosted: Wed Dec 31, 2008 9:33 am 
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Joined: Mon Mar 05, 2007 8:49 pm
Posts: 31
Location: Helsinki, Finland
Injecting the resin from both sides would be the normal way I guess, but then you need to cut a gap in the rocker table to fit the resin supply tube.
For me the holes in the core worked fine.


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