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carboncactus
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Glad to see the improvements, trev. Are you happier with the cosmetics of it? Clear coat and wax does make a big difference for depth and shine. I think you'll find that hour at 110 would have been needed for the easypreg to cure. What did you back the easypreg with?
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Matthieu Libeert
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nebraskatrevor
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Thanks to all of the suggestions I have received here I am getting much closer to success with the easypreg. I will attach 3 pictures below that show from left to right: Left sample= easy preg cured on glass sheet with 3 coats of 2K clear coat sanded with a block in between coats then polished with 3M polish, then coated with 3 coats of Carnauba wax Center sample= easy preg cured on glass with a ramped cure consisting of 2.5 hrs at 65 deg C followed by an hour at 85 deg C followed by half an hour at 110 deg C (the last part at 110 was only necessary for the other sample to the right of another material) then finished with one coat of carnauba wax which can be seen as white specks in just a few pinholes. Right sample = 2 layers of another fabric that I have used and that I have been basing some of my previous comparisons on finished only with one coat of carnauba wax. All in all the improvements I have been able to make in less than a week are very pleasing to me. Next I need to try achieving the same results in actual mold rather than just on a flat sheet of glass. I also need to investigate buying a ramping capable temp controller for my oven so that I can avoid the boring and inaccurate method I have been using, me knob and watching the clock! Thanks again for all of the help I have recieved and I will continue with a picture in the future, hopefully of a more complex part.
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fgayford
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morepower (17/06/2013)
Thought I would take a look round.... I might need to look at how surf boards are made... Haha.... (NOT)
Yep.. Leaks in bags are a pain and can be from the smallest thing.. Had one leak that a good ultrasonic leak detector just couldnt find.... It was too fast to run even with the pump running to be honest... It would have been OK for wet lay if the pump was running but not worth risking a £1000+ part for the sake of a bag..... I dont like curing with any leaks...
I would suggest getting a good leak detector from Vac Innovations or Tyga Vac.....I used to think the same way and was going to buy an expensive detector. To be honest for me its a waste of time and money. I never get leaks by following some basic rules that I have posted at various places on this site. Remember the flow media causing the holes? Where ever you have a raw cut touching the bag cover that cut with a strip of peel ply before you put the bag down and draw a vacuum also put a strip of peelply over your tubing because it is sharp as well. Hope this helps. Fred
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fgayford
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carboncactus (17/06/2013)
Good to see you here, morepower!  Heres some photos of the most common leaks I get, they are located where the tape doubles up on itself at the corner of the bag: Believe it or not, that skinny thin slither of bag coulour on the black tape is a leak:  Bend the bag/tape with the leak at the apex:  Start by squeezing from the bottom (edge of the bag):  Youre basically "plowing" tape up to the leak. Work your way to the top (bend):  Gone:  Leak is now filled by tape, the white line is a reflection of the light:  When I infuse I first get my stack under vacuum and then put the mold in my oven to get things very warm to aid in lowering the viscosity when the resin rushes in. (helps eliminate pinholes) I do my drop down test while I warm the mold. I am talking about 100 f. I then take the mold out and go over the gum tape again. It is now the stickiest it can get so sealing the mold is double effective now. If you have a tiny void just stretch the bag and push down and its gone. I then let it do a drop down test while heating in the oven. I suspect that you may not have a leak when at room temp but when you heat it you will open a leak even more. I now warm my resin above room temperature and infuse. I clamp off and cut the vac line and place in the oven for curing. Hope this helps. Fred
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morepower
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Thought I would take a look round.... I might need to look at how surf boards are made... Haha.... (NOT)
Yep.. Leaks in bags are a pain and can be from the smallest thing.. Had one leak that a good ultrasonic leak detector just couldnt find.... It was too fast to run even with the pump running to be honest... It would have been OK for wet lay if the pump was running but not worth risking a £1000+ part for the sake of a bag..... I dont like curing with any leaks...
I would suggest getting a good leak detector from Vac Innovations or Tyga Vac.....
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carboncactus
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Good to see you here, morepower! Heres some photos of the most common leaks I get, they are located where the tape doubles up on itself at the corner of the bag: Believe it or not, that skinny thin slither of bag coulour on the black tape is a leak: Bend the bag/tape with the leak at the apex: Start by squeezing from the bottom (edge of the bag): Youre basically "plowing" tape up to the leak. Work your way to the top (bend): Gone: Leak is now filled by tape, the white line is a reflection of the light:
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morepower
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Like Carbon Cactus I use VTF261 and get flawless parts from OOA carbon. I just think it is care and time that is needed.... Make sure the material is down fully and debulked before you cook it... I always allow 12 hours minimum before I cure the parts... Bagging is important too... I either use a peel ply over the back surface if I am not using a mould.. (See bottom image) Or I use none perf release film with a peel ply betwee the surface layer and the back up layers on the flange of the mould. It is to give an air path. I make sure the bag is good and keep the pump running when I am curing the part... You could get a small leak when it is in the oven and never know so if the pump is running if the leak is minute at least you may still have a good part. Cooking VTF I do not ramp up the heat too quickly and I do not work to the oven temp as much as I do the part/mould temp. The oven could be 5 degrees hotter than the part as it takes time to soak up the heat.. So I work my cooking time on mould temp not oven temp. I dwell at 65degrees C for 60 minutes and do not go higher than 85 degrees with the temp increasing no faster than 2 degrees per minute. If the cooking time is 9 hours at that rate then it is 9 hours.. I dont speed up the process just to save an hour or two..  
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Warren (Staff)
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Looks like not enough vacuum or heated up too quickly or poor bagging.
In terms of "depth and clarity" of the fibre, your skull does not have the same width tows as the easypreg. Your fibres look more like a 6k fibre rather than the 3k fibre easypreg surfacing layer is made from.
The idea about the bag might be right too.
In terms of breather, I often only use a small piece just to bridge from the vacuum port to the edge of the part, and thats it. The idea of breather is to ensure that air can be sucked out throughout the part. In practice I find as long as there is a path for air from the edge of the pre-preg to the actual vacuum port then you are fine. There are enough gaps between layers of carbon and the release film to allow the air to escape when you draw down the bag.
Warren Penalver
Easy Composites / Carbon Mods - Technical Support Assistant
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fgayford
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nebraskatrevor (16/06/2013)
I went and purchased a new vac pump and gauge today (pic one) and refined my bagging methods some and saw significantly better results but I still have a ways to go. The barometric pressure here today was 28.5 in hg (725 torr/mm hg). I worked and worked on joints until I could achieve 27.5 in hg 698 torr/mmhg neat my bag. That is also the best I could achieve with the gauge connected directly to the pump so I could be that the gauge is not quite reading correctly, or that my new pump won't quite get to a near perfect vacuum. I will attach a second picture that shows the improvement from the first plate that I showed in my original post. I could not really get the voida to photograph well so I filled them with a paste polishing compound which dries white so that they can be seen clearly. The plate on the left that looks worse is the original and the plate on the right is my new improved plate. Tomorrow if I get a chance I will try a ramped cure as suggested with a hold at an intermediate temperature for a couple of hours to allow the resin to flow more completely before it gels to see If I can improve even further on todays results. I am attaching a third picture that shows todays plate with a skull I created previously. This picture shows the difference in appearance of the carbon I was using previously with easy preg. The stuff I used before looked SOOO much better. It is hard to capture it in a photograph but easy preg is downright boring looking compared to the stuff that the skull is made of. There is a much lower of contrast between the alternating layers that I wish I could find a way to improve but I think it must be related to the weave of the actual fibers. I find it a bit ironic that the non cosmetic aerospace stuff that I was using before can look so much better that "cosmetic" grad carbon cloth. I am determined to make this stuff work, or burn thru all of it trying!    I doubt vary much that there is any thing wrong with your vacuum pumps. I assume they are oil filled vane pumps. I bought a new one like you have in the picture and was horrified that it was only drawing 28HG. The whole reason I bought it was that my air vaned pump is only capable of about 26HG. I even had the dealer come to my shop with a very accurate guage. The pump went instantly to 29 plus HG. It was the cheap piece of junk guages I was using. I threw them out and bought expensive liquid filled ones and now I know what HG I am getting.
I have used the prepreg you are using and had a fail the very first time due to a leak in the bag. I would not use stretchelone for this type of work its just too flimsy. Don't even think about putting it in the oven until you do a drop down test. If your bag is good it will still be at 29HG plus overnight.
I always put my prepreg in the oven without a vacuum line and I have had no trouble.( I clamp off and cut the line)
I think Cactus is right. You have a slight leak and losing full clamping pressure. So even though it looks tight its not full clamping pressure. So try this. Use good bagging material and do a drop down test. If it holds full vac clamp off the line close to where it is going into the bag and cut the line. Leave it overnight and see if it is still holding. If so, now put it in your oven.
I have left a fully sealed bag clamped off with vacuum line cut, for weeks on my bench and not lost any vacuum.
When I was just learning I thought a fully sealed bag was impossible.
Hope this helps.
Fred
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