Guys, I am brand new to resin infusion and had issues with my first attempt. Wandered if I could get some suggested fixes. I have read a lot and have some things to fix already. My approach was as follows. Flat part 28"x32", stack was pva, 1808 glass, 1/2" scored diving cell core, db 1700, peel ply, and bag. Ran resin line to center and teed into spiral that ran an 32" dimension. Vacuum lines ran on both long sides and only one short side. No flow media.
The top (1700) wet out almost 100% except couple spots on edges. Bottom was a disaster with lots of dry spots. Couple things I think Picked up here today. First my vacuum line touch the part and had no gap or break. I had a lot of resin flowing into vacuum lines. I think in need to add flow media on top of peel ply? Also I think I might try Vacuum lines on sides only? Because the 1808 has mat on it I was going to go with 1700 (no mat) on bottom as well.
Do you have a picture of the foam, and a picture of the result? If this is Divinycell with the large scores, it is a pig to infuse correctly. Try to slow down the resin, and use something more permeable on the bottom side. (like a unifilo 175 gram or similar.)
My opinion is that you shouldn’t put the resin feed over the core.
I would put the resin inlet channel on one side and the vacuum line at the opposite side.
No flow media is preferred if your resin gives you enough time for the injection.
I agree with Roberto. If you are feeding the resin on the top of the sandwich, and pulling vacuum on the sides, then how is the resin going to get UNDER the core, scored or not. If the core was drilled with holes, then it might not be a problem. Once the resin racetracks around the core edge, no resin will want to flow under the stack, only TO the vents.
Inject on the side, pull from the other side. Allow a resin passage for the top and bottom of the core (ie: cut core shorter than fabric), and make sure there are no side racetrack paths (core edge if not beveled)…The scored core should act as flow media in a way.
OR, if top injecting, drill holes ever square inch (1/16th inch), and then you will get resin below the core!
I’ve not inused anything with foam core (yet) but my thoughts are the same as the other posters here. You’ve not given the resin any chance to get to the underside of the core.
My method would be to infuse from the outside towards the centre. Presuming that the core stops short of the edge of the laminate and that the foam core is well perforated, it would allow the resin to flow under the foam core.
Guys, thank you for the post. I will read how to post pics and put them up. The foam is cut into 30mm squares and held together with a sqrim. For the next try I have drilled holes through each foam square. I thought infusing from one side and evacuating from the other might be better. So no flow media seems to be the consensus?
I am doing this for non structural boat parts so at least the first part is salvageable all be it not ideal.
Drilling lots of holes as you have done will work. What size inlet tube do you use? Slowing down the speed of your infusion would also help imo.
This method works ok for me with just pin hole core thats if you dont need one side to come out with a moulded finish.
Vacuum table
flow media
release film/peel ply
laminate
foam core
laminate
peel ply/release film
flow media
Top and bot flow media extend past core one end so become overlaping each other, feed line goes on top of this. Vacuum port and resin break the oposite end.
Note laminate peel ply etc I spray tacked to foam then just lay on top of some flow media taped on the vac table.
I want to echo those who have suggested to slow down the flow of resin. If your resin reaches the vacuum line before the part is fully wet out the resin will just keep flowing to that place rather than filling in your dry spots.
In the past when I have had problems with dry spots or an infusion moving too quickly I have used a delay line. Basically a delay line is a low-permeability (so resin won’t flow in it as quickly) material (try a couple of layers of peel ply or some small weave glass) on the mold surface between the part and the vacuum line. This way air can be pulled through it so you can draw your resin into the part but it resin will move slowly in it, giving your part some time to fully wet out.
I can come back later with a diagram to describe how I would lay it up on the table. I think you’ve received some nice advice about how to solve your problem. Putting some perforations in the core will definitely help get resin down there but if you have racetracking (which you will thanks to those grooves) and the resin gets to the vacuum line too quickly then those things won’t help solve the problem entirely.
Thanks for the advice. I did try two more parts since the last post. Part #2 - Made perforations in foam core. I did extend peel ply on the mold past part to slow resin down (worked good). I used a glass laminant with out mat on it on the bottom. In order to see if that did the trick I did not change anything else. Infused from center, with epoxy. This time the bottom wet our great but the top didn’t get there (opposite of first try). I think the epoxy is to viscous as the part would no draw the resin in after about 20 minutes-very slow.
Part #3 - switch to polyester with viscosity of 450cps. Added flow media on top. Perforated the core. Used a different bagging material. Infused from center with vacuum paralell on two sides. Infused very quickly and I thought I had it until I pulled it off. Bottom had dry spots again. not nearly as bad as Part one which is shown on previous page.
I keep tring to perfect it with the infusion from the middle because I hope to move onto a much widder part once I get a good set-up but looks like all the advice points to a side infusion. So that is the next test.
I would recommend infusing across the panel. Feed resin along one side, pull vacuum on the other. Add staged feed lines every 36-48" if it’s a large part.
Do use flow media, but end it about 3" from your vacuum lines. This will slow down any racetracking and give dry areas time to infuse before resin starts getting pulled through the vacuum line.
Make fewer perforations on the core next time, about 1/2 as many, and place them at the intersections of the grooves. This will act as a flow media on the mold side. You don’t need grooves on the bag side if using flow media.
Overall, your finished panel doesn’t look too bad right now. A few changes and you should achieve great results.
TET thank you for the advice. I am going to give it a shot and see what happens. If I put green flow 75 on between the laminate and cor on the mold side would it harm the part? Meaning it would be permanent. Would that help the flow under the core?
Thought I would update you on lessons learned. I did have a successful infusion with some adjustments during the process. First thing is that the flits in the divincell have to go down. The backer on the foam really slows the resin down so flow media all the way to the edge less 1/2" is key. Things worked good. I have a hard time finding and stopping leaks. Not sure why.
I also went and watched a local shop that is infusing 1.5 inch thick foam. Learned a lot. They use perforated foam. They infuse from the top with feeds 18" apart max. They use a continuous strand mat as flow media an of course thickness. They also were using much lower viscosity resin then I am. Below 200cps. Very cool! I want to try the mat hey are using. They also said the chopped strand mat on the back of the stitched glass kills the flow so I need to stick with fabric w/o mat backing.
I got into the middle of this discussion. Here are some thoughts on infusing the part
Place perforated plastic on top of the laminate
Use flow medium to distribute the resin
I probably would infuse from the center and put a continuos vacuum line on the entire outside edge. Place the vacuum line 3 to 4 inches away from the part.
Cut the flow medium and perforated plastic short of all edges by 3" and place a piece of peal ply overlapping the flow medium by one inch and having it continue outward past the part for another three inches to the vacuum line. Wrap the vacuum line with the peel ply.
What should happen is the resin will be distributed though out the part. The natural channels of the core will help in this process too. At the intersection of these foam core channels you will notice a hole to allow the resin to be absorbed on the other side of the core. By holding back from all edges the perforated plastic as well as the flow medium you get the resin stopping short of the part. The resin will continue at a much slower rate to to the edges. Although because you have a natural flow medium with the core selected it may proceed to the edges quicker. Because the peel ply has been extended three inches past the part the resin will continue to fill the entire part. The peel ply acts like a break allowing the part to completely saturate. It will take a few minutes to awhile for the resin to flow through the peel ply. The key is to allow time for the part to be completed before any resin reaches the vacuum line. Once resin reaches the vacuum line the vacuum pressure is lowered and the resin will follow the path of least resistance.
Make sure you place the perforated plastic down first, the the flow medium. The perforated plastic will prevent the flow medium from sticking the the finished part.
Make sure the resin being used will not kick off before finishing the part.
I do heaps of this type of work, its such an easy way to make sandwich panels…
There are 2 main approaches.
1st is to use a flow media - or more accurately, a layer of high permeability. So you can use anything from bird netting, to shade cloth, to proper infusion medias like greenflow etc, all of which “go over the top”. Or as you discovered recently, you can use intra- laminate high permeability layers such as continuous filament mat (CFM) or soric (pressure resistant core mat) which still aid the resin flow, but become permanently part of the cured laminate.
The 2nd method is to use flow channels, these can be in the bag or caul plate, again “over the laminate” or scored into the core material “under teh laminate”. They must be spaced accordingly so the spaces between channels fill completely. Typical is 20mm grid spacing.
Unless you use some form of flow media or flow channels on both sides of the sandwich, the core must be perforated at no more than 50mm centers, most prefer 20mm or risk little dry spots between perforations. If you have a perforated core, then you only require flow media or channels on 1 side of the sandwich. The tool side of the sandwich laminate can be cosmetic / mirror quality if the core is perforated and the flow media/channels are on the bag side- which is what i do with my panels.
I always center feed and pull toward the edges - the reason is that any leaks are usually around the bag edges and it will not not drag air across the laminate with the vacuum lines around the perimeter. So center feed, with additional feed lines at 600mm spacing depending on the part size and your resin viscosity. You need to use infusion resins, generally below 350cps, typically around 200cps. Otherwise you wont be able to pull the resin a reasonable distance before resistance is too high.
I always stop the flow media 50mm from teh panel edge. The reason is to allow for the flow front lag (top and bottom flow fronts are not the same speed unless you have flow media on both sides). The flow media side will always be in front of the non-flow media side. Allow 50mm for the fronts to even out before the panel edge. When the front reaches the panel edge, race tracking around the panel edge will occur and lock off the vacuum to any parts that have not wet out yet. Stopping the flow media 50mm short, allow the resin to slow right down before reaching the edge and allows the rest of teh panel that still needs to fill, time to catch up. It allow everything to even out before crossing the panel edge where you loose control of the flow front. If using infusion groove cut foam core, fill the first 50mm of these grooves around the entire perimeter prior to the layup with thickened epoxy, this serves the same effect, you dont want these grooves allowing resin to race track around the panel edge before the whole thing is completely filled.
Have nothing but peel ply between the panel edge and the vaccum lines, this acts as a resin brake when infusion is nearing completion so you will not suck heaps of resin into your vacuum lines and catch pot. The peel ply alone allows vacuum to pass, but resin only very slowly…
Lastly, make sure you have very strong vacuum if using epoxy, the more the better. And you must have no leaks if you want a quality finish, any leaks ruin the results no matter how well you design and execute a perfect strategy.
Now that it has been a year I just saw this and wanted to say thanks. I have since my last post infused a part as you described and it can out great. I still have trouble getting no leaks so I have not figured out the silver bullet there yet. I want to do a large 6’x10’ cored part but am not confident enough that I won’t waste $1,000 in material.
