infusing with contour balsa

Forgot to say use CFM continuous filament matt not CSM if you can. CFM aids flow, most CSM retards, only stitched csm aids flow marginaly.

 

Groper, im a little confused, my plan for the actual part (which we just finalized the dimensions) will be 3m x 2m which looks about the width of your panel in the second picture in post #2 and I was planning on feeding it just like you show (3 feeds) except I was thinking of 3 buckets but I don't need to. Being a noob to infusion i feel more comfortable with the sequential feed than the single feed fishbone system for a part this big. Knowing the size of my part remembering that it has a 100mm buildup on the mold table to create the turned down edge, how would you layout the feed and vacuum lines?

Steve.

 

Andrew, I was planning on gelcoating then hand laying the 3/4 oz skin coat with unwaxed resin, then setting up for infusing just to buy myself more open time for my first infusion part. I may be overthinking it. I just received my Amprobe ULD 300 yesterday, yay.

Steve.

 

Same as I show in the pic- resin line down the center of the part, then another pair half way out to the edge which are opened only after the front passes them. Vac lines down each 3m edge with a Peel ply only resin brake from edge of panel to VAC line- I usually put the vacline 3-4 inches out from panel edge. Stop any flow media 2 inches inside from any panel edge to prevent race tracking around panel edge.

 

Thanks Groper, that's pretty much what I had in mind except I was going to run the 3 feed lines into separate buckets but I don't need to since you don't think its a good idea, I can see the value of the kiss principle.

Steve.

 

Steve; I understand your thinking for your first infusion job.
The only things I have made with the contour balsa was hull suport pads for my catamaran, this ofcourse opened up the gaps which made the infusion very fast. On a flat surface I suspect that it still will be fast with no need for transfer matt. Also guessing that you will only need one centrall feed, feeding 1m to each side. As I said this is only a gutt feeling as I have not infused contour balsa on a flat table.
As groper said do a test first.

If you are going to be doing lots of infusion jobs with PE/VE and plan to use matt to block print through get yourself some CFM. I found the 450gsm grade to be as fast as 60% shade cloth. This may not mean much to you at this stage but will to groper.

 

Thanks Andrew, I will look into cfm, its not something that is readily available or something ive used before. Is 60% shade cloth what you typically use? I presume you are using the knitted stuff.
Contour.balsa is knife cut so that on a flat surface there are no gaps but I see that corecell has a knife cut foam with slices half way through from each side which I dont think has any drilled holes so I expect the balsa will work. As I said, I will be doing a test piece without gelcoat on a sheet if glass so I can see how the resin transfers through. We are heading into a very cold week and I may not be able to get the shop up to the sustained temp I need. I need to get not just the resin but the tool and materials up to temp.

Steve.

 

We typically use 30% shade cloth as the 60% wastes too much resin - its unessesary waste for most of the jobs we do. 30% is a bit slower and doesnt pull as far, but is adequate for our needs and the cost is very low.

The CFM is great... Spray your gelcoat then layup your preform using the CFM - no need for flow media or wetlaminating a skincoat prior. If your part is not weight sensitive, the CFM is a great intra-laminate flow media and it will promote flow on the tool side as well as block the print.

Andrew - havnt heard from you in a while, where have you been hiding? Hows your boat going? Show us some more pics will ya!

 

Well, I did my test panel a couple of days ago, im pleased to say everything went very well. I made the panel 1m x 400mm (which is as big as I can go on my glass table) with the vac line across a short end and the feed across the other. I used electrical spiral wrap for the vac and 1/2" irrigation pipe for the resin feed line. The layup was 2 x DB1708 on each side of a 3/4" contour balsa core with airtech green flow media. When I first opened the feed line the resin raced across the top maybe 150mm before it found its way through the core then slowed down while the bottom caught up some, it didn't quite make it all the way to the end before gelling, about 850mm with the bottom front about 75 mm behind. The wetout was perfect. As soon as we closed the bag we pulled a full atmosphere with no leaks, probably the best bag ive ever done.
I cut a 305mm x 305mm section out and weighed it, it came in at 1057 grams, 318 grams of glass, 299.6 grams of core leaving 439.2 for resin which works out to be 42% glass, 58% resin. What I havnt figured out how to do is find out how much of that resin is in the skins and how much is in the core seams, ill probably need to infuse some glass without core to get the true glass to resin ratio. What ratio should I expect?

Steve.

 

I get 70:30 fibre to resin by weight, you should get similar if you infuse at close to absolute vacuum at sea level. If your using styrenated resins then you'll have to infuse at more like 90% vac to avoid boiling the styrene off.

The rest of the weight is going into the surface of the core and gaps. Andrew k reckons around 600grams per square meter goes into the balsa per side. With 80 km/m3 PVC foam, about 300grams per side. I know the foam is correct, but I haven't infused with balsa to confirm.

 

Steve; 30%wt resin with epoxy, VE resin density should not be too different. Rule of thumb that I use for estimating resin required to impregnate the glass is to halve the weight of the glass.
Your test pannel area was ~0.32m2; 320g glass so 160g resin to wet ot the glass + 300g core= 780g. So 1060-780= 280g resin used to fill the core, works out to ~440g per m2 each side. Not bad.

I use a spreadsheet to calculate resin requirement for each job.

 

Thanks guys, this is such good info. Im still trying to get a handle on the resin waste so i can estimate more closely how much resin to mix or to have ready to catalyze. I forgot to mention that i also am using the green flow mesh and also had the resin race away across the top before it started to wet the bottom, at that point the top slowed down allowing the bottom to start to catch up although it never did completely, lagging by about 75mm when it stopped flowing.
I have a few questions regarding the resin uptake into the core
1/ when you say that balsa consumes about 600 gm/m2 per side, is this for rigid end grain balsa sheet or for skrimmed contour balsa as i am using?
2/ with the H80 foam you are using is the 300gm/m2 each side for drilled and scored or just drilled?
3/ do you need the scoring joining the drill holes?

Thanks, Steve.

 

1. Youd have to ask AndrewK for sure as ive never infused with it, but id say its for plain sheet. Id imagine the scrimmed contour balsa would use more...

2. Again, just for plain sheet. The resin to fill perforations is in addition to the surface porosity allowance of 300g/m2. Simply calculate the volume of the perforations by the size and number of hole per meter, multiply by weight of resin.

3. yes, this is the way DIAB supplied my foam when i bought the infusion grid scored and perforated sheets from them. If the perforations dont line up with the scores on the other side, the lag will be much greater on the non scored side and probably lead to incomplete or poorly wetout laminate on the non scored side.

 

Steve; I have determined resin consumption for all of the materials I use and with a simple spreadsheet I know exactly how much resin is required for each job. You having done this one test are on the way being able to do likewise.
Regarding the lag time in the bottom laminate, if you hold short your flow media at the vacuum edge even 1" is enough for the bottom to catch up at the finish.
How many minutes did the infusion take to reach the ~800mm when it stalled? what was your gel time? seems to me you may need something longer for comfortable infusion jobs where you have much larger quantity of resin in your bucket/s

 

My resin has a gel time of 25 minutes at 77 degrees F, the resin stopped flowing 17 minutes in but it probably would have gone the whole meter except I didn't mix enough resin at the begining and when it started racing across the top before wetting through to the tool side i had to clamp off the feed and mix another batch, of course then it slowed down once the bottom started flowing. Next time I will be more prepared. I am nearly ready to do another test but it will be an actual part about 13 ft2. This part I plan to run the feed line up the center with a tee across the end with the vacuum line around the perimeter. I am looking for less expensive consumables as at the moment im buying them from a distributor, ive found a scource of the spiral wrap for 24 c / ft instead of 60c, I took a piece of peel ply in to the fabric store today and found 100% polyester liner fabric that looks exactly the same for $3.50 / yd instead of $7.50, then I found the same stuff online for $1.98 / yd so I will be doing some testing. For the feed lines im using 1/2" irrigation tube which is only about $10 for 100ft. What i need to find is a bag material that is wide and works with esters. Is the shade cloth you guys are using the knitted stuff or woven?

Steve.