Learning Vacuum Infusion by Trial and Error

[Issus]

I've been wanting to learn how to do vacuum infusion for quite awhile, I know the theory but I've never seen it done in person or in a video before so I had some ideas of what to expect but not really any knowledge of how those theories worked in practice. I've done a lot of wet layups which have been bagged, and see this as the next step to improving my composites, especially with complex shapes which can be very hard to layup wet.

I have a litre or so of some sort of Araldite (marked K36) which appears to be: https://www.kirkside.com.au/Uploads/Images/aralditekitk36.pdf - however it's about 8 years old, learning how to do infusion is going to be a great way to get rid of it.

With the aim of getting started today, I headed off to the hardware store last night to grab some parts. I knew I'd need a resin trap of some sort, and a way to feed resin into the dry cloth then turn it off.

I know a resin trap would ideally also have a carbon filter to remove volatiles from the extracted air and stop them from gumming up the pump and various valves in my system. I'm wasn't sure how to go about building that yet so I plan to leave that until later, and now am considering building it as a separate "device" in the chain. I know I'll likely buy a replacement set of 3M/similar respirator filters, cut them open and use the carbon from them.

This whole build has been totally off the cuff, without my using planning and research, I wanted to put my theories into practice before following someone elses formula. Several of the composite books I have cover vacuum infusion however I haven't read through that far before.


So... back to my parts.

I started with:
3x brass 1/4BSP to 3/8" barbs (fits the 10mm pipe i use nicely.)
1 metre of 50mm PVC pipe (DWV)
1 black Poly pipe threaded end cap for 50mm pipe (this was in a different section, as the end caps in PVC were a bit rubbish and would have required additional O-Rings or other method of sealing)
1 PVC thread coupler for 50mm pipe
1 PVC end cap for 50mm pipe (these things are so nice and meaty)
1 metre of 150mm PVC pipe (in this case, on DWV pipe is available, however is quite thick walled)
1 PVC screw cap for 150mm pipe
1 PVC thread coupler for 150mm pipe
1 PVC end cap for 150mm pipe
1 Brass 1/4BSP drain cock
1 40c roll of teflon tape (these always seem to run out just as you start a new project! So this is a pre-emptive purchase)
3 metres of 10mm food grade reinforced hose
3x cheap 13mm reticulation pipe valves (kinda like a really crappy ball valve) - at $1.50 or something each these were the cheapest valves I could find.

My first task was to drill the lids out, I couldn't find my 11mm drill bit so ended up using a 10mm drill bit and putting a lot more effort into getting the tap started.

Two barbs into the poly pipe cap

One barb, one drain cock into the 150mm lid.

My plan is to also be able to use the epoxy reservoir (the 150mm pipe part) as a vacuum degassing chamber for pots of epoxy, silicon, urethane, whatever. I've sized it such that I put a plastic mixing cup into it without any hassle. This is the reason why I have a drain cock and barb on the top - so I can either pour from it (we'll get to that) or pull a vacuum from the lid and release it.

I then realised that my PVC pipe was the wrong one, thought about my plans a bit more after playing with the parts in the garage a bit more... and went back to the hardware store... and came back with:
-1 metre of 50mm PVC pipe (DWV)
+1 metre of 50mm PVC pipe (not DWV pipe, the thicker walled reticulation pipe)
1 1/4BSP brass right angle (male to male)
1 cheapest 1/4BSP ball valve I could find
1 more brass 1/4BSP to hose barb

Now I have a 150mm lid with a right angle, ball valve and hose barb + drain cock.

And a section of PVC cut to length and glued to the coupler. The red stuff is the PVC cleaner, it stains the PVC red when it's clean, and stays a milky pink if it cant etch the PVC surface. The glue is green (and I need to get some new stuff, this was getting really really thick.)

I put together the resin trap

And discovered why my teflon tape always runs out after a project... those threads needed a ton of tape to seal up!

Both parts together, as the glue is curing, I've placed the lower barb next to the pipe where it will go, this is where epoxy will drain from.

 

[Issus]

Today, I moved my vacuum pump assembly over to the work table to make it easier (it sits under the CNC mill usually).

My first thing was to find somewhere to put the resin trap, in hindsight this was a really dumb place to put it. It did nicely hold the pipes out of the way though! This would be a great place for a chemical trap.

My first project was going to be a 29mm tube, because doing small tubes wet is a pain, and it also uses less material. The length of the tube is determined by the width of my scrap cloth.

I covered some bluetube coupler in packing tape, then spiral wound on baking paper (parchment paper for the north americans here). I taped the baking paper together at one end.

Next up, mastic around the tube, then over the hose at each end. I stuck a spring in the end of each hose to facilitate air/resin flow (worked great) as the spiral wrap tube was $15/metre at the hardware store (W T F!) and I didnt have any left at home. I was planning to make a few wraps of spiral tube around the coupler at each end to allow resin to flow in and around smoothly but this will have to be done some other time. The hoses are taped to the coupler so they cant move/break the mastic seal.

I used some spray on contact adhesive along the start line on the baking paper, then started the cloth.

One immediate advantage of dry layup: You dont need to calculate the exact length of your cloth, just wrap the right number of layers and then cut along your start line

No attention paid to keeping the weave straight.. thats not the point of this exercise.

Next came perf film, then breather, then bagging film. Bagging film sealed along the length with packing tape. In hindsight, I should have had perf film under the seam of the breather - rookie mistake!

I pulled a vacuum on the tubing to get rid of any small leaks, fixed those until there were no obvious whistles of air at -20in hG.

Now I was ready to take my time preparing resin, very nice to be able to not have to rush anything on this. I mixed 100ml of resin, 25mm of hardener - total overkill but I wanted to have too much rather than too little. I had no idea how it would flow. I tried putting the cup into the new vacuum degasser chamber and pulled a vacuum on it, but after a minute there were still bubbles in the resin... might have to do some more research on that.

I poured the resin into the chamber, and opened the plastic valve to let the resin get drawn through (the layup was already under vacuum) - this was much slower than I expected, and once it hit the layup behaved very different to my expectation. I had expected it to flow up through the cloth quickly and fairly evenly, as the resin in my mind would create a path of high resistance where there was resin, and lower resistance where there wasnt - so I figured it would flow around the tube quite smoothly. It didnt - it all bunched up at the insertion point over a length of about 10cm. I had to massage it down the length of the layup after closing the plastic valve.

This is where things got really strange, there must have been a lot more air in the resin, or layup, or somewhere than I expected - it was bubbling, almost boiling, away like crazy with the bubbles all jetting down the resin to the vacuum end. There didnt appear to be any resin in the hose going out though. Now, 2hrs later, I find that most of the resin has made its way out of the layup and into the hose. Lesson learned, put the resin trap next to the vacuum port of the bag. I need to go buy another few metres of hose now (hardware store closes in 23 minutes!). Heating the resin with a hair dryer increased the viscosity, and therefore bubbling considerably. It's going to be very interesting to see how this all looks when the bag comes off!

 

[Issus]

Couldnt figure out why the resin isnt hardening, so i checked the datasheet I linked in my first post, and sure enough its a 2:1 mix not a 5:1 as i thought (the containers are 5L and 1L!)

I need to remember to wax the inside of the resin trap before trying again, as this time it will get resin in it. I need to check the seal on the bottom cap too, there is a slight whistling coming from it I believe. I bought new solvent today so I might just see if i can fix the seal up a little.

While I was at the hardware store, I couldn't help myself from picking up parts to make a carbon filter.

The filter pack was $18, much cheaper than the $35 for a 3M one, however is 1 grade lower. The carbon filters are not quite as thick.

Inside the filter

The end caps connected with a small piece of PVC.

Cut up parts of the filter and the synthetic steel wool, used to block the ends of the filter to stop the carbon escaping or other debries making a mess.

End drilled and tapped.

And barb installed.

Bottom filter parts installed (double steel wool pad for the bottom), and filled with the carbon from one filter. This gives me a spare filter for refilling this at some later date.

The other filter parts added, and a cut section of PVC installed as a spacer.

Completed filter

 

[CarVac]

1: Put a paper cup inside the resin trap to catch the resin.

2: You need to use flow cloth, the green mesh stuff you can see in the photos from Bare Necessities's thread, to ensure sufficient flow. Edit: Additionally, use peel ply and not perforated film, and don't use breather.

3: What is the carbon filter for? Filtering the air coming out of the pump? Cool idea.

 

[Issus]

My resin catch is lying on it's side at the moment, i'll have to see if i can figure a way I can hang it over the side of the bench. The cup is a great idea.

Damn, i have a vast qty of breather... I was actually thinking today I should get something like a fine mesh for getting better flow. I'm using perf film because I have a much larger quantity of it than peel ply, it's 1/3rd the price and it does leave a rather nice finish for airframes I'll try peel ply on infusion #3.

Epoxy fumes are pretty nasty things, the fumes off the araldite I have are much worse than things like west, the hardener is quite corrosive. The filter goes inbetween the layup and the pump, I have a MAC valve and pressure switch down stream, as well as two ball valves. I don't really want them getting gummed up - i've had to replace them in the past just from doing vac bagging so this has been a long time coming. Next I want to build a better intake for the pump, perhaps a taller tube with some fine mesh in it that will return some of that oil vapour. I need to refill the oil, just need to figure out what sort it takes as I used the last of it today.


I tried layup #2 this evening, after getting that oh so sticky mess of #1 off. I took things really slow this time, letting in just a little bit of resin at a time. I only used half of the 50g of resin I mixed (this was a smaller piece of scrap - 4 layers of cloth around 150mm long.) This time I didnt use the baking paper - baking paper is mandatory on wet layups without vacuum - however the infusion just runs the epoxy straight through all the layers of the paper and probably would have ended badly if that resin had cured. This time, it's two layers of packing tape, one spiral wound, one lengthwise. Then I waxed it to be sure. I used electrical tape to tape the hose on both sides of the mastic this time to better strain relieve it.

It seems as though the resin goes through 3 stages after it's flowed through, there is a little bit of time between each one. First, it seems all the air goes out, it sounds like very quiet rain as it bubbles through. It's really hard not to get air in the resin intake line as it draws through - I think this is where the air is coming from.
Second, once the air is mostly out, it will sit for a bit, not really moving, then suddenly the resin starts to move through and make its way out of the layup as the pressure pushes down on it. I'm guessing the delay is as the resin in the layup equalises, then it is able to move out down the vent line. It takes a good 3-4 minutes before there is any resin in the vacuum line based on both of these infusion.

After the bubbling phase, I'm thinking its a good time to hit it with the hair dryer to lower the viscosity of the resin and help it equalise/flow through.

On this infusion, I also used the chain I picked up, it worked far better than I expected. I can easily see the resin flowing along it and into the spring.

You can see it layed up here.

I'm hoping that there are no wrinkles in the layup where the bag creases up. I tried to get the cloth as tight as possible, but the vacuum can always make it tighter than I ever could.

 

[troj]

You're right, dry layups are easier than wet....however, it's really easy to end up with it too loose, and not realize it. You'll discover that when you pull a cured, and wrinkled, layup out of your infusion setup.

We learned that the hard way....

-Kevin

 

[Issus]

Any tips on how to combat that issue? I can certainly see where you're coming from on it, it seems like it would be very easy to do.

 

[troj]

Any tips on how to combat that issue? I can certainly see where you're coming from on it, it seems like it would be very easy to do.

Wrap it tight. It'll take some practice.

-Kevin

 

[CarVac]

Wrap it tight. It'll take some practice.

-Kevin

You can massage it under vacuum too.

 

[JohnCoker]

Smaller tubes are generally harder than larger ones as well (the greater circumference gives you more wiggle room with the cloth). I've only achieved wrinkle-free vacuum bagged tubes (wrapped or 100% composite) on 4" and larger sizes. This is not to say it can't be done, and maybe infusion is a better technique, but just my experience.

 

[Issus]

John - I agree, the smaller tubes are the hardest, thats part of the reason why I started with them. If I can get it worked out on the smaller tubes to a reasonable degree then normal sized tubes will be beautiful I dont have any issues with wet (unbagged) layups on 29mm these days, so if I'd to at least match my wet skills with infusion. The smallest tube i've bagged is 4" and dont get any wrinkles with that. I'm pretty sure I have some 2" and 4" coupler lengths here to experiment on, however they may have been sitting on an angle for a year or two and may not be entirely straight.

troj - what about if it's not a tube?


I pulled the film off, after heating the resin for an hour with the hair dryer to get the resin green. There are the creases I was worried about, some of them are epoxy only, at least one has glass in the ridge. Tomorrow I'll try infusion #3 with just peel ply, assuming I can get this one off (another 8hrs or so and it should be cured enough, this K36 cures painfully slow for experimentation, and it's 4x past shelf life doesn't help.) I'm hoping that this resin lives up to it's advertised low shrinkage, or this could be really difficult to get off, thats the main reason for the baking paper on wet layups. For #3, I may try double packing tape, waxed (to be slick), a layer or two of rolled baking paper, a layer of bagging film sealed with packing tape, then finally a wrap the layup. This could make it more challenging to wrap tight, but that may be easier to allow it to be pulled off the mandrel easier.

I think I need to figure out how many layers I can do per tube thickness (and per cloth type) before wrinkles are inevitable.

 

[flynfrog]

you can make a disposable resin trap with a few feet of layflat bag. Stack about 5 layers of n10 breather and 120 glass about 2 inches wide and put it at the exit of your part. This will buy you hours of bleed time and you can keep pulling vacuum as long as you shut off your resin flow. Its important to degas your resin before you start the shot. This can be done by simply elevating temp but you might start to advance your resin early. If you have a vacuum pot you can do a degas before the shot. Also mixing your resin with a round rod vs a flat stick will help keep you from adding air to the resin.

When we do infusion shots we use a double bag system. The inner bag pulls the resin through the part the outer bag maintains compaction. If you are interested I can try to MS paint something

 

[JohnCoker]

I think I need to figure out how many layers I can do per tube thickness (and per cloth type) before wrinkles are inevitable.

Two maximum, in my experience, but that's wet-out-and-bag, not infusion. I think the issue is how much decrease in diameter you will get. If the total decrease is small enough, the cloth can shift without wrinkling.

But there's not a lot of flex along the tows. Speaking of that, it just occurred to me that one could run the cloth at 45° to the axis of the tube to avoid having tows running in hoops (or use a pattern other than flat weave). I'll have to give that a try next time I bag a tube.

 

[troj]

troj - what about if it's not a tube?

If it's something like a nosecone, where you have to cut it into multiple smaller pieces, you're going to have less of a problem, as the pieces have an ability to shift past each other a bit. One long, continuous wrap has to shift the entire wrap, in order to compress without wrinkling.

There are the creases I was worried about, some of them are epoxy only, at least one has glass in the ridge.

Yep, not getting that is the trick.

FWIW, making a removable mandrel is a trick, as well.

-Kevin

 

[CarVac]

If it's something like a nosecone, where you have to cut it into multiple smaller pieces, you're going to have less of a problem, as the pieces have an ability to shift past each other a bit. One long, continuous wrap has to shift the entire wrap, in order to compress without wrinkling.

You can do that same trick with tubes as well, apparently. I haven't tried it personally, though, and it's still not so great for a skinny tube because handling long thin strips of cloth is difficult.

 

[Issus]

you can make a disposable resin trap with a few feet of layflat bag. Stack about 5 layers of n10 breather and 120 glass about 2 inches wide and put it at the exit of your part. This will buy you hours of bleed time and you can keep pulling vacuum as long as you shut off your resin flow. Its important to degas your resin before you start the shot. This can be done by simply elevating temp but you might start to advance your resin early. If you have a vacuum pot you can do a degas before the shot. Also mixing your resin with a round rod vs a flat stick will help keep you from adding air to the resin.

When we do infusion shots we use a double bag system. The inner bag pulls the resin through the part the outer bag maintains compaction. If you are interested I can try to MS paint something

That sounds quite like what I've been dreaming up for doing infusion plate. I'd love to see any photos or paint drawings you have

Two maximum, in my experience, but that's wet-out-and-bag, not infusion. I think the issue is how much decrease in diameter you will get. If the total decrease is small enough, the cloth can shift without wrinkling.

But there's not a lot of flex along the tows. Speaking of that, it just occurred to me that one could run the cloth at 45° to the axis of the tube to avoid having tows running in hoops (or use a pattern other than flat weave). I'll have to give that a try next time I bag a tube.

I'm not sure a 45 degree layup would give you the same strength as a 90/0 degree layup? I can see how something like twill would help, however I only have plain on hand at the moment. I'm wondering if carbon would wrinkle less or more for this, as its far far stiffer (the good stuff anyway).

 

[CarVac]

But there's not a lot of flex along the tows. Speaking of that, it just occurred to me that one could run the cloth at 45° to the axis of the tube to avoid having tows running in hoops (or use a pattern other than flat weave).

But that kills the longitudinal strength...

 

[JohnCoker]

But that kills the longitudinal strength...

I think "kill" is an overstatement, but point taken. Another option might be a twill weave, but I'm not sure how well the additional conformability will translate to ability to shrink in hoop diameter.

 

[CarVac]

What I've done is vacuum bag (I hadn't done infusion at that time) a thick layer of longitudinal unidirectional cloth, because it doesn't care about any wrinkles. Then you can follow it up with thin layers of weave, bagged or not, because the strength in the hoop direction really isn't that critical.

 

[JohnCoker]

What I've done is vacuum bag (I hadn't done infusion at that time) a thick layer of longitudinal unidirectional cloth.

Great idea; this is a perfect use for unidirectional carbon cloth. And I happen to have most of a roll of it left, so I'll try that on my next vacuum bagged tube.

 

[CarVac]

Great idea; this is a perfect use for unidirectional carbon cloth. And I happen to have most of a roll of it left, so I'll try that on my next vacuum bagged tube.

You do have to sand it afterwards before a top layer though.

 

[Issus]

I pulled infusion #2 off, well actually, ended up cutting it free with the Dremel, I need to put more thought into my mandrel removal strategy. The composite had multiple bubbles in it near the surface, I feel that the perf film didn't help here as the resin+bubbles were pulled through/under it. On a wet layup, excess resin takes the bubbles with it on the way out, here, there is no resin. Other than these two issues, the result wasnt too awful - just the wrinkles that I had - I believe I can solve that as detailed in infusion #3.


Infusion #3 went *awfully*.

I decided to simplify things and use the offcut of 150mm pvc as my mandrel, figuring a bigger tube would be easier. I was very very wrong. What would have been a 15 minute wet layup with 15 mins of prop, took 4 hours for prep and another hour or so of layup. Some of this is down to trying to figure out how I wanted to do things.

I ended up doing a spiral wrap of baking paper that made 2 layers, then putting packing tape over that, longitudinally. I was trying for an hour or so to put bagging film over the baking paper, but I just couldn't figure out how to get it taught. It was going to wrinkle like crazy under the cloth and that was going to be a very bad start. I used good cloth on this, it has a more open weave than the old offcuts I was using previously, I had hoped this would assist with resin flow. I also used peel ply rather than perf film + breather. Other than that, the setup was mostly the same. I did spray tiny amounts of contact adhesive over the cloth as I was laying it up, this allowed me to get the cloth very compact, and the peel ply too. I had high hopes at this point of a wrinkle free, good quality layup. The cloth ended up being around 750mm long down the mandrel, and 4 layers.

Once I mostly got rid of some really difficult to kill leaks in the bag, i mixed around 60 grams of epoxy and let it in. It went in exceedingly slowly, not sucking through rapidly like the smaller, shorter tube. It really really did not want to wet out and flow through the cloth. I mixed a further 40g of epoxy, and basically had to pour that in rather than have it sucked in by the vacuum. I tried heating the epoxy too. I ended up getting all but one section of the cloth infused, with a *lot* of excess epoxy making a jacket around the cloth. The remaining section of dry cloth was around the vacuum outlet (to vac pump), so i dropped the vacuum and spun the tube around, mixed some more epoxy and made the outlet the resin inlet. This wet out the section of cloth that was dry. The resin that did flow down the layup did not flow very evenly, it definitely preferred some areas over others - it really did not wet out very nicely at all.

One thing I did notice was a distinct loss of vacuum down the length of the bag even with just dry cloth. At the vacuum outlet end, the bag could not be pulled back from the cloth at all, there was no flex. At the resin inlet end, there was considerable movement when pulling on the bag, so much so i could pull on a crease and create a gap of 5-8mm below the bag. I believe the bag was pulling the cloth down tight enough to almost fully seal the tube off about 1/3rd of the way down the tube. Due to the lack of vacuum down the infusion end, the resin pooled and was able to attack the mastic, due to the pressure of the bulging resin, it was able to make its way down a slight crease under the bag and between the resin - this totally destroyed the seal at this point and one other point. I was able to regain most of that seal with quite a bit of work. I believe the breather cloth was masking this effect in the smaller layups, however also created a place for bubbles to live.


One positive of this experience, infusion #3 came off the mandrel oh so smoothly. The paper over waxed pvc with packing tape on it worked wonders.


It's immediately clear to me that I need flow media for a larger layup, and likely the smaller layup too, as CarVac has said. This is a big problem for me, the two companies that supply composites in my city (state) do not stock it, and will not get anything less than a full roll of it - full rolls of it are way way out of my price range with what the charge and would likely last me a lifetime. The next problem is that my city (state) is extremely isolated. The most isolated capital city in the world in fact. If flow media is available in australia, it could be annoying to get it here - long parcels are as difficult as they are from an international source - international sources are often cheaper. I've found a couple of stores in the US/Canada which have it for $2-10/m however I think it's going to be a battle to have them ship it. Therefore, I need an alternative for experimenting with, even if it's not as good as the real deal.

What do you guys think of shade cloth? It's quite open and rather bulky, however I havent tried pulling a vacuum on it to see if it will retain those properties when getting squished. It's also not overly expensive. I'm open to other ideas for hardware store-sourceable supplies. Most of Lowe's range is available at Masters here (Lowes own 50% of them. The shelving, store layout, even barcodes/product labels are the same.)


This layup has a vast number of bubbles, resin pools/veins, surface defects, lack of surface uniformity, you name it - if it's something you don't want, this layup has it.

The original 24mp versions of these photos are available online if the full size might help with ideas.

https://www.markhphoto.com.au/Vacuum-Infusion/i-3GLVcKZ/0/XL/DSC_0058_dxo-XL.jpg[/img
This is the section of tube which would not wet out (lighter colour)

[img]https://www.markhphoto.com.au/Vacuum-Infusion/i-rZmg4Hp/0/XL/DSC_0059_dxo-XL.jpg[/img
The weave pattern is not hte cloth, it's the peel ply. Bubbles are about 1-1.5mm across.

[img]https://www.markhphoto.com.au/Vacuum-Infusion/i-mkSVW5L/0/XL/DSC_0061_dxo-XL.jpg

This isn't a wrinkle as such, it's where the resin has pooled in the bag. The cloth is flat beneath it. These are all over the place.

You can see glass strands in the bubbles, the bubbles mostly follow the weave of the cloth. Again, the weave pattern that is visible is the peel ply.




And finally - the carbon filter was a great idea. When I flipped the bag around I took the opportunity to open it and see what the dust filter section looked like - it was damp and discoloured, I figured that some epoxy had poured in so pulled it out so as not to restrict the flow. Now that the resin is all cured - it turns out it did not get wet with resin, the discolouration is still there however it's not stiff, just slightly tacky. If this is how the little bit of cloth looks, the carbon trap must be collecting a lot of crap! I'm really glad I built this for infusion and wet bagging!

 

[CarVac]

The real issue is that you can't expect the resin to flow through the fabric on a large layup. The green stuff lets the resin flow around the fabric, allowing bubbles to expand, but at the same time the resin will soak through the comparatively short distance into the fabric.

The reduced resistance means you get full vacuum along the entire length of the layup. If there is significant resistance elsewhere, you get less vacuum applied on the other side of the resistance. That allows bubbles to remain and slows the flow.

Here's our first Bare Necessities test layup. We didn't degas properly, so the resin had tons of bubbles once we pulled a vacuum on it, but the layup turned out to be totally free of voids and bubbles.


If you're looking for a source of flow cloth, our first attempt at resin infusion used the flexible mesh tube protectors that some people buy to protect their motor cases. It's a bit wasteful of resin compared to real flow cloth because it's unnecessarily thick, but it worked alright for us. Pretty much anything with this overlapping quality that won't fully block the flow in any direction should be okay.

 

[Issus]

I'll have to hit the hardware stores and see what I can find

 

[flynfrog]

it also helps to double the layers of the RDM (resin distribution material)

how big is your pump?

 

[Issus]

Presently I don't really seem to have any flow material. I'm thinking of looking at a craft store on thursday night (late night shopping) or maybe some gutter guard or an aquarium supply store as it appears they use plastic meshes stop stop fish getting pulled into the pump. This also makes me think of looking at a fishing/boating store to see what sort of netting they have.

My pump is only 3cfm single stage, I'm pretty sure it's the old version of this - mine is about 4 years old.
https://www.ebay.com.au/itm/NEW-SIN...Electrical_Test_Equipment&hash=item2ec23abdd0

I have it on a vacuum switch, and MAC valve setup with two 1m long, 50mm ID vacuum reservoirs which with slight leaks gives me about a 20-30% duty cycle when set to -20in hg. It's not ideal, but its what I have to work with One of the local club members is trying to get me some sewer pipe to make a 1-2m long, 30" ID, 32" OD reservoir from - I'll likely have to go to a faster 2 stage pump if this pans out just to evacuate the reservoir in a reasonable time period.

 

[Issus]

So doing some research today, it turns out that humidity can be trapped in the glass and also cause bubbles. I need to ramp my vacuum to -28" from the present -20" and apply the vacuum for 30 mins prior to infusion in order to boil any humidity off. Based on the dampness I mentioned in the carbon filter, I now think that may have been moisture (not helped by the leaks I was battling). It was extremely humid when I did the layup - we had our first rain of the year last night, with Sunday being quite humid as we got to the point of it raining.

I think a stronger vacuum will also help with degassing the epoxy. I'm also tempted to hold the resin and hardener under a good vacuum for 30 mins or so before mixing too, as these have *not* been stored properly and likely have moisture in them. Hopefully I can boil off some of the moisture in the resin and some of the volatiles in there.

As a rule, epoxy compounds are less moisture sensitive except for certain hardeners. Moisture contaminated epoxy hardeners can usually be recognised by the formation of a crust around the edges of the container

That'd be me!

I'd like to repurpose a small motor to build a little agitator for the cups I mix epoxy in so that I can agitate the mix in a vacuum, or better yet, use the motor to mix the epoxy under a vacuum - serving to both degas and mix without introducing at the same time. Some M3 or M4 screws through the lid, sealed with teflon tape (which ran out on sunday incidentally) could be a good way to get power into the chamber I built along with a couple of ring terminals.

 

[CCotner]

Here's a some tips I received from an engineer at PTM&W re: degassing when I was talking to them last year. Hopefully they are helpful:

• I'm pretty sure you want to degas after you mix the resin and hardener; you will introduce air and moisture into the epoxy when you mix it. Degassing both before and after is probably not a bad idea, but probably overkill.
• 18 inHg might not be enough. We were pulling around 28, maybe a little less, with our pneumatic venturi-style pump, and it wasn't enough. The result of our effort was the mixed resin/hardener became a thick, opaque frothy mix for a few minutes; the engineer told us we didn't quite have enough vacuum, so we had allowed billions of tiny bubbles to form, but weren't pulling hard enough for them to escape. He told us we were better off not trying to degas than partially degassing, to avoid accidentally increasing void content in the final part. I think he suggested 29.5-30 inHg as the ideal range?
• He said that under sufficient vacuum, the mixed resin/hardener would turn opaque as bubbles formed, would swell up to 2-3 times its initial volume, and would then rapidly begin to boil and collapse down to the original volume, returning to clear as it did so; once it collapsed entirely and stopped boiling, it was properly degassed. So be careful how much epoxy you degas; if our pot had degassed properly, we would almost certainly have totally filled our trap and ruined the pump.

I'm really impressed so far with your hardware; ours was a mess, scrapped together and hardly working, other than that BAMF of a pneumatic pump that Aircraft Spruce and ACP sell. Resin infusion has a ton of advantages when it works; by the time I finished the nosecone on BN, I was regularly doing layups of 7-10 layers of fabric without wrinkles, with excellent compression and consistent resin content, by myself, without making any mess at all; I easily could have not worn gloves, because I never spilled a drop. Just try and do that, let alone do it by yourself at 4 in the morning, working with wet layup and vacuum bagging. Keep it up!

 

[Issus]

Thanks for the tips, the info on degassing is very helpful. I would see a multitude of small bubbles but not any froth, and certainly no expansion - I will crank up the vacuum. I had it turned down quite a ways (I was at 15inHg last time I was bagging actually) due to my implosion of a reservoir previously - hence switching to the 50mm tubes which have the thicker wall and smaller ID. The system can handle it, I'm just being a wuss haha. I need to go through and reseal all my fittings, it's been 6 months since I used my vacuum setup and some of these have slight leaks - the system doesn't hold a vacuum for very long, so pulling a higher vacuum is going to make this problem worse. I'll see if I can get time to do this tonight, otherwise perhaps tomorrow as my wife works late

I've also read that you can reduce wrinkles and increase fibre density by applying and relieving the vacuum 4-6 times, which causes the fibres to settle against each other well. This could really help with getting things nice and dense and smooth if it works - multiple people have described this so I feel its legitimate. I imagine a light massage of the layup the first few times when its under the vacuum could also help.

I've read of one person buying flow media in Australia, however he was paying $7.40/m2 for it, and ended up using 30% shade cloth with good results - he was buying full rolls so his cost of cloth was down to $0.30/m2 - a significant saving!

I'm counting on about 8-10 infusions before I start to figure it out, so I'll be sticking with it, you're right - it will make life much much easier once I have it down. I have built up a resistance/allergy/whatever it is to epoxy so the less I have to touch it/breath it the better. I do wear gloves and a respirator but wearing them for hours and hours can be annoying. I figure the cost of consumables will end up pretty similar to wet layups, substituting brushes for valves/hoses, breather for flow media and many other little differences.

I need to replace the Nitto coupler I have on the epoxy reservoir/degassing chamber with something else. These work great for air compressors but are useless for vacuum in the way they seal I believe I have Jamec on my bag valves, but those are much more expensive and not offered in a sealed variety at hardware stores here.

 

[Issus]

Purchased two of these:
https://www.ebay.com.au/itm/52FT-16...452?pt=LH_DefaultDomain_0&hash=item2337ddfcf4

Should be enough to figure out infusion



I'm starting to feel tempted to find the parts to make an acrylic or polycarbonate tube vacuum degassing chamber. It would be pretty fun to watch it degas