First crack at resin infusion of a flat panel

With some trial and error we took a crack at infusing our first flat panel. Nothing spectacular just a cover for our sump pump well. I've got a lot to learn about this process before I ever dream of attempting to infuse the entire hull of our boat.

It's an odd shaped panel. Anyhow, have a look you experts. Any suggestions are greatfully appreciated. I'll have a crack at the other side after I get some feedback. It'll be another 20 hrs or so before I unmold this one.

It looks so much easier when the pro's on the Internet do it!

firstinfusion001.jpg is the stack layed up ready to pull the vacuum.

firstinfusion002.jpg is the stack with vacuum pulled.

firstinfusion003.jpg is after about 11 mins of infusion and the resin has already reached the vacuum outlet by running up the sides. I should have stopped the flow media and not allowed it to drape over the edge.

firstinfusion004.jpg is after the part fully infused at about 32 minutes.

 

I would have infused from the center, out. Instead of point a to point b.

A resin jacket in the middle of the part. Surround the whole part with a spiral wrapped vacuum chanel. And let the vacuum draw resin outwards.

Or I would have started on the right side and drawn the resin towards the larger side of the part. A "U" shaped vacuumm canel around the top, left, and bottom sides of the mould. With the resin inlet on the right side.

The way you have it set up, you will probably always get resin circumnavigating the part.

 

Here's what I've learned so far.

Thanks for the feedback JRL. I'll try to incorporate those suggestions when I tackle the second half of the cover.

First of all this process is a little labor intensive and probably not much economical benefit for one-off parts production. The benefit is your hands never touch the epoxy! The process is also wasteful. There are a lot of consumables involved, the resin flow media, peel ply, bag, spiral wrap, t-fittings, the butyl tape and the bag. I also wasted 25' of plastic line (forgot to cut it shorter) and a small resin trap I tried (too small).



The tooling surface is a 2x4' piece of malamine. 10 coats of release wax later you test it for adhesion with a piece of masking tape. If it sticks at all, more wax. This was the first time for this piece so I gave it a couple extra coats. There are other mold release agents available but I didn't try them.

It is vital to ensure that your layup will maintain a perfect vacuum after you shut off the pump. The clamping pressure is what maintains the ultimate shape of the part you're trying to produce. I'll explain later on what happens when you don't.



The location of your resin inlets and vacuum outlets are also critical to the success of the part. Seen here the panel is not infusing well. The resin was able to circumnavigate the part and reach the vacuum outlet too soon. This meant either pumping a lot more resin in (as I now know is wrong) or stopping the process and adjusting the flow media etc. (which is an extremely messy proposition.



I eventually got the entire part infused after about 32 minutes. About twice as long as it should have taken and using twice as much epoxy as required.



The epoxy I used is specially formulated for resin infusion. It has an ultra low viscosity and a very long working time (+5 hrs). For small parts like this the longer working time is more of a PITA than a benefit.

The completed part came out of the stack fairly easily. The peel ply did it's job perfectly. The resin flow media (nylon screen mesh) did stick to the tooling surface. There are some areas along the edges of the part that didn't stick due to loosing vacuum on the stack. What happened is the excess resin that was being pulled off the part kicked off in the vacuum line just ahead of the resin trap. This in essence shut off the vacuum to the stack. After that there was no way to get the whole layup back under vacuum. I had planned to trim the edges anyways.

Frontside

Backside


The larger flat surfaces of the part are perfectly infused. There are absolutely no bubbles or areas where there shows any resin starvation or delamination. Both sides of the part were infused at the same time and I was a little worried about the backside (laying on the tooling surface) not getting resin. No worries there. The flow media looks after that.



Some of you wll recognize the biaxial fabric. It's 1708 that I got from BBC. Amazing product! A little awkward to handle such heavy fabrics and it takes some getting used to. A little 3M Super77 adhesive was req'd to keep things from moving around too much when setting up the stack. The peel ply a fine weave nylon fabric left a very smooth surface. It would probably need some light sanding for a secondary bond. I'm just guessing until I cut into the part but I figure there's 40% resin and 60% fabric. Maybe a little less resin but not much.

So the things I learned are:

Proper location of the resin inlet and vacuum outlets are critical. Experience necessary I think so that you can judge when/how the resin will reach the outlet AFTER the part is fully infused (Ideally).

Having a perfect vacuum seal on the layup is also critical to the complete success of the final part. Any leak, no matter how small is unacceptible. An ultrasonic leak detector, such as those used in the refrigeration repair industry would be a big benefit.

A bigger resin trap is required. Mine was only about 5 oz, sort of an inline filter thingy. I have my eye on an old paint pot at the local flea market that'll work. Shorten your vacuum lines so you don't waste them if you suck in some resin.

Heat lamps and hair dryers are good to help control the flow of resin. As soon as the part is fully infused we lit the exit area with lamps to help the resin kick off quicker. This helped a little bit in restricting the flow of resin, as it will with a sustained vacuum applied. Downside is it prevented us from reapplying vacuum when we needed it. Two vacuum outlets, a primary and a backup is maybe a good idea.

I'll probably do the other half next week. Need to acquire a few more materials. HOpefully it'll go better. Will post the results as well.

I'm thinking all this tinkering with this process might lead to being able to produce some smaller parts for our project, hatch covers, etc. We'll see. I don't think I have the stones to try this on the whole hull of a TW28!!! That's risky beyond belief (for me anyways). I've seen it done on the Internet but without professional guidance I don't think I'd even attempt it (feel free to remind me of that)!

 

Resin infusion is expensive at first. But once you have the pattern down. You can cut back on consumalbes. The labor becomes very robotic as its the same everytime, all the time. And eventually the entire process shortens (experience curve).

Another thing to remember is that you dont need to leave the resin line open untill all the cloth is wetted out. You can clamp it shut at about 75 to 80% infused. The resin inlet side will be very resin rich, as compared to the vacuum outlet side. Once the line is clamped the resin has a self leveling tendancy inside the bag. The excess resin from the inlet will move to the starved side of the infusion. This will end up saving you a lot of epoxy. And imporving your resin to weight ratio.

Also make sure you weigh your cloth before you start the whole process. It will give you an idea of how much resin you need in your resevoir. DIAB makes some scored cores that you may want to look into. It will help decrease you infusion times. Laying your cloth in the direction you want your resin to flow will help speed things up also. Thats why a lot of guys mix some unidirectional cloth into their layups.

Once the part is infused throw it under some dry heat (not the sun).

 

Thnx JRL

All good points to remember (rapidly taking notes).

I was going to use some CS corecell but thought it a little too expensive for a sump cover. The 1708 was a little extravigant too! The biaxial fabrics appear to work well in helping with the infusion. I was a little worried about the CSM backing but it didn't seem to have any adverse affect.

I had no way to actually weigh the cloth (digital scales on order). I guestimated the amount based on square footage. I ended up using just about double what I calculated. Got a heat lamp on order too.

Next attempt might use two bags. One to infuse the part and the other to clamp it after infusion. Just another method to test out. Watched a guy repair a hole in a boat a couple of years ago and that's what he did. After the infusion was complete he clamped off the inlet and outlets then pulled the vacuum on the second bag to clamp it. What that did was prevent the vacuum from pulling more resin out of the repair. He was working on a vertical surface, which doesn't really matter I guess, but only let the clamping HG get to about 20. Once the resin kicked he let the vacuum off and inflated the bag. He then set up a heat lamp to expedite the process or post cure I think. He was kinda a grumpy ole' fella and didn't respond to many of my stupid questions so I just watched intentively.

 

Thats exactly why he used a second bag. To prevent the resin from draining. The pro's use a permeable gortex liner inside the infusion to prevent drainage. Lets air out, resin stays in. I still have yet to try it.

 

Not all core created equal

When they tell you that all foams (for core) are not created equal you better listen. I cut the parts to fit the pump and outlet. Here's what I found.



The part looks ok. There looks to be a really good resin to glass ratio. No voids. Then on the second part this is what happened with the jig saw.



The foam was completely bonded to the glass/epoxy. The foam itself failed. I'm guessing that's what they mean when they look at the various factors, sheer modulus, etc. when they describe foam qualities.

The infusion epoxy is still a bit soft (stretchy) but is getting harder all the time. Mfgr said up to 2 weeks before it's fully hardened. You can post-cure (heat it up) to expedite the curing process. I might try that next time because this epoxy has an extremely long working time (+5 hrs) and +24 hrs to demolding the part.

The 1708 glass/epoxy ended up almost exactly 1/32 of an inch thick! Somehow I thought it would have been thicker but due to the vacuum clamping it's been compressed quite substantially.

 

Ooops!

This is what happens when your resin trap is "Waaaaay" too small!

Second pic is new trap. I don't think (well I hope) won't be filling it up anytime soon. It has a clean-out on the bottom and is 100% PVC and the epoxy doesn't stick to it.

 

Try using Adtech's 820 resin. It has a 2 hour work life. 350 cps. And is demoldable in 24 hours.

Full hardness in 5 to 7 days.

I got it to infuse through 8 layers of 8.8oz 6871.

Also keep in mind that vacuum cant compress glass farther than what is stated in the glass manufacturers specs. If it says glass thickness is .01 then under vacuum it will still be .01. Vacuum minimizes resin thickness.

 

Epoxy will stick to PVC. It might be wise to wax the inside of the tube.

 

Thnx Nero. I used something called "Lanocote". Supposedly nothing will stick to that. Thnx again.

Rick

 

I have found that a 2 gallon presure pot for paint to be the best for a resin trap, i just bring the resin line right through the lid and seal it with some bagging tape, what you will want to do is place a 1 gallon paint can or coffee can inside the presure pot this will collect all he resin and keep the presure pot clean i often put a pint of acetone in the pot and let the can float this way my pot stays clean

 

Hi Jack

I had my eye on one at the flea market last week. Passed it by planning to come back and get it on the way out and it was gone! Just my luck. I think the PVC one will work for now. The reservoir and the trap hold a perfect vacuum for over 3 days so I know there's no leaks. At some time I might get a pot, Harbor Freight has them for about $30.

Cheers

Rick

 

that will do the trick just fine, i once made a resin trap out of a old cooking pot worked great, just drilled 2 holes in the lid one for the resin line in and one for the resin line out sealed the lid with bagging tape and the best thing was it was teflon lined and the resin just fell out with a bang of a hammer pick them up at the discount store for a few bucks

 

The wifey's been keepin' a close eye on me every time I open her cupboard with her pressure cooker in it!