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oekmont
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Group: Forum Members
Posts: 550,
Visits: 27K
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Almost anything can be don't by infusion. Complex parts require more skill, but this is even more the case for wet layup.
There are special spray adhesives, wich won't be visible at the finished part.
Ooa prepreg is probably the easiest way to make small complex parts if you have the equipment.
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Hanaldo
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Group: Forum Members
Posts: 2.5K,
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50% vacuum is pretty standard for wet lay vac bagging.
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Steve Broad
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Group: Forum Members
Posts: 408,
Visits: 4.1K
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+x+xI would like to interrupt and tell my (and many others) opinion. first of all the "size" of your pump is completely irrelevant as long as you are not making bigger boat hulls, or something similar in size. Pumps with bigger volume output are only faster to pull down bigger bags, but for car part sized moulds we are talking about a minute or two maximum. The final pressure will be the same. Secondly and most important it is absolutely crucial not to apply full vacuum when vacuum bagging after wet layup. Full vacuum will degas the resin inside your part and will result in pinholes, the effect described. Thirdly when dealing with pinholes gelcoat will make the problem worse. The air bubbles will be there all the same, but under under the gelcoat. So you will need to sand trough the gelcoat to fill them. Last but not least, I would almost always prefer vacuum infusion over wet layup with vacuum bagging. In the end it is the same effort, but the result is better and much more consistent. Wet layup only makes sense to me if you haven't got a vacuum setup. If you bag the part, you could as well profit from infusion with all its benefits and don't mess around with resin. Hi Oekmont, Thanks for your input. So if you don't apply full vacuum, how to you determine how much you should apply ? Do you have any standard reference for wet layup, if using a adjusting gauge ? OK for infusion...I have never tried. Thing is that I have 5 kg of standard epoxy right now...so I kind of want to finish it before buying infusion epoxy. My worry with infusion was that the parts I am making are sometime fairly complicated, with some angles, and applying the dry carbon on them, with different layer and then vacuum that for the infusion...I was wondering if then you would use some fixative spray ?
Now do you think infusion is easier than prepreg ? I am busy with a friend building an oven for prepreg that will be properly controlled, because I thought pre-preg would be easier and cleaner to operate. Or am I wrong ?
Thanks again! Personally, prepreg is the way to go. No messy resin that has a limited pot life, no complicated piping and resin reservoirs. A MUCH quicker curing process. Fabric that sticks to the mould without recourse to adhesives. The only downsides I can think of (there are probably more and there must be some advantages that somone will no doubt point out :-) ) are that dry cloths drape better than prepreg so complicated shapes and tight internal corners take a little more work to get right and you need a suitable oven to fit whatever you are making into. I don't miss wet lay or infusion at all but each to his own. As an example, when making small panels using an aluminium mould, the time taken from the finished mould to pulling the piece off of the mould after curing is around 2.5 hours. Half hour to lay up carbon and bag. Half hour or so to raise to curing temp of 120 deg C at 3 deg a minute, then one hour dwell at this temp. Leave to cool for 30 minutes then remove from oven and extract part from the mould. Compare that to wet lay or resin infusion :-)
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Hanaldo
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Group: Forum Members
Posts: 2.5K,
Visits: 28K
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+x+x+xI would like to interrupt and tell my (and many others) opinion. first of all the "size" of your pump is completely irrelevant as long as you are not making bigger boat hulls, or something similar in size. Pumps with bigger volume output are only faster to pull down bigger bags, but for car part sized moulds we are talking about a minute or two maximum. The final pressure will be the same. Secondly and most important it is absolutely crucial not to apply full vacuum when vacuum bagging after wet layup. Full vacuum will degas the resin inside your part and will result in pinholes, the effect described. Thirdly when dealing with pinholes gelcoat will make the problem worse. The air bubbles will be there all the same, but under under the gelcoat. So you will need to sand trough the gelcoat to fill them. Last but not least, I would almost always prefer vacuum infusion over wet layup with vacuum bagging. In the end it is the same effort, but the result is better and much more consistent. Wet layup only makes sense to me if you haven't got a vacuum setup. If you bag the part, you could as well profit from infusion with all its benefits and don't mess around with resin. Hi Oekmont, Thanks for your input. So if you don't apply full vacuum, how to you determine how much you should apply ? Do you have any standard reference for wet layup, if using a adjusting gauge ? OK for infusion...I have never tried. Thing is that I have 5 kg of standard epoxy right now...so I kind of want to finish it before buying infusion epoxy. My worry with infusion was that the parts I am making are sometime fairly complicated, with some angles, and applying the dry carbon on them, with different layer and then vacuum that for the infusion...I was wondering if then you would use some fixative spray ?
Now do you think infusion is easier than prepreg ? I am busy with a friend building an oven for prepreg that will be properly controlled, because I thought pre-preg would be easier and cleaner to operate. Or am I wrong ?
Thanks again! Personally, prepreg is the way to go. No messy resin that has a limited pot life, no complicated piping and resin reservoirs. A MUCH quicker curing process. Fabric that sticks to the mould without recourse to adhesives. The only downsides I can think of (there are probably more and there must be some advantages that somone will no doubt point out :-) ) are that dry cloths drape better than prepreg so complicated shapes and tight internal corners take a little more work to get right and you need a suitable oven to fit whatever you are making into. I don't miss wet lay or infusion at all but each to his own. As an example, when making small panels using an aluminium mould, the time taken from the finished mould to pulling the piece off of the mould after curing is around 2.5 hours. Half hour to lay up carbon and bag. Half hour or so to raise to curing temp of 120 deg C at 3 deg a minute, then one hour dwell at this temp. Leave to cool for 30 minutes then remove from oven and extract part from the mould. Compare that to wet lay or resin infusion :-) Totally agree, pre-preg is just a joy... But have you ever tried to layup a 5sqm rear clam on a 35 degree day? You'll be cursing the stuff then! Haha. Seriously though, infusion has it's place, and for me it is larger structures. Laying up a bonnet, you can throw all the layers including consumables on in 10 minutes, then use the vacuum to get everything in place. If you tried to do a large bonnet with pre-preg, not only is it a nightmare to get the material in place, but you also need to spend a good bit of time making sure you haven't got any bridging or unconsolidated areas, as the vacuum won't help you. So where the properties of pre-preg help you to complete a small complex layup, they can fight you when trying to complete a larger layup. Of course, if your bonnet was very complex with lots of louvres and vents, then it could be easier again with pre-preg. Tooling can also be an issue. Nice and easy to make small high temp tooling, but making high temp tooling for full vehicle panels or boat hulls can be not only obscenely expensive, but also more difficult to construct. You have to start thinking about the tool not being able to support its own weight and distorting, so do you make a support structure? But then support structures can print onto the surface badly, or cause their own distortion issues due to differences in CTE. Heat really adds a whole new level of complication to composite production that can really bite you if you don't plan well. I try to be retrospective with every part I make, and use the different techniques and processes to my advantage. That's why they exist, to make production easier. If you choose to use a method that isn't entirely suited to the component you're making, then you're just making life more difficult than it needs to be. All of that said, there's just something about pre-preg that does put it top of the list for me. I get excited about producing a new pre-preg component in a way that doesn't really happen with infusion anymore. Infusion is bread and butter, pre-preg is caviar - you probably don't need to eat caviar for breakfast lunch and dinner, but you'd give it a thought if it was an option 😉
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Damien
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Group: Forum Members
Posts: 32,
Visits: 132
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+x+x+x+xI would like to interrupt and tell my (and many others) opinion. first of all the "size" of your pump is completely irrelevant as long as you are not making bigger boat hulls, or something similar in size. Pumps with bigger volume output are only faster to pull down bigger bags, but for car part sized moulds we are talking about a minute or two maximum. The final pressure will be the same. Secondly and most important it is absolutely crucial not to apply full vacuum when vacuum bagging after wet layup. Full vacuum will degas the resin inside your part and will result in pinholes, the effect described. Thirdly when dealing with pinholes gelcoat will make the problem worse. The air bubbles will be there all the same, but under under the gelcoat. So you will need to sand trough the gelcoat to fill them. Last but not least, I would almost always prefer vacuum infusion over wet layup with vacuum bagging. In the end it is the same effort, but the result is better and much more consistent. Wet layup only makes sense to me if you haven't got a vacuum setup. If you bag the part, you could as well profit from infusion with all its benefits and don't mess around with resin. Hi Oekmont, Thanks for your input. So if you don't apply full vacuum, how to you determine how much you should apply ? Do you have any standard reference for wet layup, if using a adjusting gauge ? OK for infusion...I have never tried. Thing is that I have 5 kg of standard epoxy right now...so I kind of want to finish it before buying infusion epoxy. My worry with infusion was that the parts I am making are sometime fairly complicated, with some angles, and applying the dry carbon on them, with different layer and then vacuum that for the infusion...I was wondering if then you would use some fixative spray ?
Now do you think infusion is easier than prepreg ? I am busy with a friend building an oven for prepreg that will be properly controlled, because I thought pre-preg would be easier and cleaner to operate. Or am I wrong ?
Thanks again! Personally, prepreg is the way to go. No messy resin that has a limited pot life, no complicated piping and resin reservoirs. A MUCH quicker curing process. Fabric that sticks to the mould without recourse to adhesives. The only downsides I can think of (there are probably more and there must be some advantages that somone will no doubt point out :-) ) are that dry cloths drape better than prepreg so complicated shapes and tight internal corners take a little more work to get right and you need a suitable oven to fit whatever you are making into. I don't miss wet lay or infusion at all but each to his own. As an example, when making small panels using an aluminium mould, the time taken from the finished mould to pulling the piece off of the mould after curing is around 2.5 hours. Half hour to lay up carbon and bag. Half hour or so to raise to curing temp of 120 deg C at 3 deg a minute, then one hour dwell at this temp. Leave to cool for 30 minutes then remove from oven and extract part from the mould. Compare that to wet lay or resin infusion :-) Totally agree, pre-preg is just a joy... But have you ever tried to layup a 5sqm rear clam on a 35 degree day? You'll be cursing the stuff then! Haha. Seriously though, infusion has it's place, and for me it is larger structures. Laying up a bonnet, you can throw all the layers including consumables on in 10 minutes, then use the vacuum to get everything in place. If you tried to do a large bonnet with pre-preg, not only is it a nightmare to get the material in place, but you also need to spend a good bit of time making sure you haven't got any bridging or unconsolidated areas, as the vacuum won't help you. So where the properties of pre-preg help you to complete a small complex layup, they can fight you when trying to complete a larger layup. Of course, if your bonnet was very complex with lots of louvres and vents, then it could be easier again with pre-preg. Tooling can also be an issue. Nice and easy to make small high temp tooling, but making high temp tooling for full vehicle panels or boat hulls can be not only obscenely expensive, but also more difficult to construct. You have to start thinking about the tool not being able to support its own weight and distorting, so do you make a support structure? But then support structures can print onto the surface badly, or cause their own distortion issues due to differences in CTE. Heat really adds a whole new level of complication to composite production that can really bite you if you don't plan well. I try to be retrospective with every part I make, and use the different techniques and processes to my advantage. That's why they exist, to make production easier. If you choose to use a method that isn't entirely suited to the component you're making, then you're just making life more difficult than it needs to be. All of that said, there's just something about pre-preg that does put it top of the list for me. I get excited about producing a new pre-preg component in a way that doesn't really happen with infusion anymore. Infusion is bread and butter, pre-preg is caviar - you probably don't need to eat caviar for breakfast lunch and dinner, but you'd give it a thought if it was an option 😉 +x+x+x+xI would like to interrupt and tell my (and many others) opinion. first of all the "size" of your pump is completely irrelevant as long as you are not making bigger boat hulls, or something similar in size. Pumps with bigger volume output are only faster to pull down bigger bags, but for car part sized moulds we are talking about a minute or two maximum. The final pressure will be the same. Secondly and most important it is absolutely crucial not to apply full vacuum when vacuum bagging after wet layup. Full vacuum will degas the resin inside your part and will result in pinholes, the effect described. Thirdly when dealing with pinholes gelcoat will make the problem worse. The air bubbles will be there all the same, but under under the gelcoat. So you will need to sand trough the gelcoat to fill them. Last but not least, I would almost always prefer vacuum infusion over wet layup with vacuum bagging. In the end it is the same effort, but the result is better and much more consistent. Wet layup only makes sense to me if you haven't got a vacuum setup. If you bag the part, you could as well profit from infusion with all its benefits and don't mess around with resin. Hi Oekmont, Thanks for your input. So if you don't apply full vacuum, how to you determine how much you should apply ? Do you have any standard reference for wet layup, if using a adjusting gauge ? OK for infusion...I have never tried. Thing is that I have 5 kg of standard epoxy right now...so I kind of want to finish it before buying infusion epoxy. My worry with infusion was that the parts I am making are sometime fairly complicated, with some angles, and applying the dry carbon on them, with different layer and then vacuum that for the infusion...I was wondering if then you would use some fixative spray ?
Now do you think infusion is easier than prepreg ? I am busy with a friend building an oven for prepreg that will be properly controlled, because I thought pre-preg would be easier and cleaner to operate. Or am I wrong ?
Thanks again! Personally, prepreg is the way to go. No messy resin that has a limited pot life, no complicated piping and resin reservoirs. A MUCH quicker curing process. Fabric that sticks to the mould without recourse to adhesives. The only downsides I can think of (there are probably more and there must be some advantages that somone will no doubt point out :-) ) are that dry cloths drape better than prepreg so complicated shapes and tight internal corners take a little more work to get right and you need a suitable oven to fit whatever you are making into. I don't miss wet lay or infusion at all but each to his own. As an example, when making small panels using an aluminium mould, the time taken from the finished mould to pulling the piece off of the mould after curing is around 2.5 hours. Half hour to lay up carbon and bag. Half hour or so to raise to curing temp of 120 deg C at 3 deg a minute, then one hour dwell at this temp. Leave to cool for 30 minutes then remove from oven and extract part from the mould. Compare that to wet lay or resin infusion :-) Totally agree, pre-preg is just a joy... But have you ever tried to layup a 5sqm rear clam on a 35 degree day? You'll be cursing the stuff then! Haha. Seriously though, infusion has it's place, and for me it is larger structures. Laying up a bonnet, you can throw all the layers including consumables on in 10 minutes, then use the vacuum to get everything in place. If you tried to do a large bonnet with pre-preg, not only is it a nightmare to get the material in place, but you also need to spend a good bit of time making sure you haven't got any bridging or unconsolidated areas, as the vacuum won't help you. So where the properties of pre-preg help you to complete a small complex layup, they can fight you when trying to complete a larger layup. Of course, if your bonnet was very complex with lots of louvres and vents, then it could be easier again with pre-preg. Tooling can also be an issue. Nice and easy to make small high temp tooling, but making high temp tooling for full vehicle panels or boat hulls can be not only obscenely expensive, but also more difficult to construct. You have to start thinking about the tool not being able to support its own weight and distorting, so do you make a support structure? But then support structures can print onto the surface badly, or cause their own distortion issues due to differences in CTE. Heat really adds a whole new level of complication to composite production that can really bite you if you don't plan well. I try to be retrospective with every part I make, and use the different techniques and processes to my advantage. That's why they exist, to make production easier. If you choose to use a method that isn't entirely suited to the component you're making, then you're just making life more difficult than it needs to be. All of that said, there's just something about pre-preg that does put it top of the list for me. I get excited about producing a new pre-preg component in a way that doesn't really happen with infusion anymore. Infusion is bread and butter, pre-preg is caviar - you probably don't need to eat caviar for breakfast lunch and dinner, but you'd give it a thought if it was an option 😉 Hi Hanaldo,, Thanks for your feedback. For me, all the parts I am doing are small parts for racing motorcycle (and I am not even doing the fairings...only internal parts, brackets etc...). So they are small and usually complex. So for me, pre-preg seems like the best option. I have never done infusion but I will definitively consider it if I end up one of these days making larger parts.
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Hanaldo
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Group: Forum Members
Posts: 2.5K,
Visits: 28K
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+x+x+x+x+xI would like to interrupt and tell my (and many others) opinion. first of all the "size" of your pump is completely irrelevant as long as you are not making bigger boat hulls, or something similar in size. Pumps with bigger volume output are only faster to pull down bigger bags, but for car part sized moulds we are talking about a minute or two maximum. The final pressure will be the same. Secondly and most important it is absolutely crucial not to apply full vacuum when vacuum bagging after wet layup. Full vacuum will degas the resin inside your part and will result in pinholes, the effect described. Thirdly when dealing with pinholes gelcoat will make the problem worse. The air bubbles will be there all the same, but under under the gelcoat. So you will need to sand trough the gelcoat to fill them. Last but not least, I would almost always prefer vacuum infusion over wet layup with vacuum bagging. In the end it is the same effort, but the result is better and much more consistent. Wet layup only makes sense to me if you haven't got a vacuum setup. If you bag the part, you could as well profit from infusion with all its benefits and don't mess around with resin. Hi Oekmont, Thanks for your input. So if you don't apply full vacuum, how to you determine how much you should apply ? Do you have any standard reference for wet layup, if using a adjusting gauge ? OK for infusion...I have never tried. Thing is that I have 5 kg of standard epoxy right now...so I kind of want to finish it before buying infusion epoxy. My worry with infusion was that the parts I am making are sometime fairly complicated, with some angles, and applying the dry carbon on them, with different layer and then vacuum that for the infusion...I was wondering if then you would use some fixative spray ?
Now do you think infusion is easier than prepreg ? I am busy with a friend building an oven for prepreg that will be properly controlled, because I thought pre-preg would be easier and cleaner to operate. Or am I wrong ?
Thanks again! Personally, prepreg is the way to go. No messy resin that has a limited pot life, no complicated piping and resin reservoirs. A MUCH quicker curing process. Fabric that sticks to the mould without recourse to adhesives. The only downsides I can think of (there are probably more and there must be some advantages that somone will no doubt point out :-) ) are that dry cloths drape better than prepreg so complicated shapes and tight internal corners take a little more work to get right and you need a suitable oven to fit whatever you are making into. I don't miss wet lay or infusion at all but each to his own. As an example, when making small panels using an aluminium mould, the time taken from the finished mould to pulling the piece off of the mould after curing is around 2.5 hours. Half hour to lay up carbon and bag. Half hour or so to raise to curing temp of 120 deg C at 3 deg a minute, then one hour dwell at this temp. Leave to cool for 30 minutes then remove from oven and extract part from the mould. Compare that to wet lay or resin infusion :-) Totally agree, pre-preg is just a joy... But have you ever tried to layup a 5sqm rear clam on a 35 degree day? You'll be cursing the stuff then! Haha. Seriously though, infusion has it's place, and for me it is larger structures. Laying up a bonnet, you can throw all the layers including consumables on in 10 minutes, then use the vacuum to get everything in place. If you tried to do a large bonnet with pre-preg, not only is it a nightmare to get the material in place, but you also need to spend a good bit of time making sure you haven't got any bridging or unconsolidated areas, as the vacuum won't help you. So where the properties of pre-preg help you to complete a small complex layup, they can fight you when trying to complete a larger layup. Of course, if your bonnet was very complex with lots of louvres and vents, then it could be easier again with pre-preg. Tooling can also be an issue. Nice and easy to make small high temp tooling, but making high temp tooling for full vehicle panels or boat hulls can be not only obscenely expensive, but also more difficult to construct. You have to start thinking about the tool not being able to support its own weight and distorting, so do you make a support structure? But then support structures can print onto the surface badly, or cause their own distortion issues due to differences in CTE. Heat really adds a whole new level of complication to composite production that can really bite you if you don't plan well. I try to be retrospective with every part I make, and use the different techniques and processes to my advantage. That's why they exist, to make production easier. If you choose to use a method that isn't entirely suited to the component you're making, then you're just making life more difficult than it needs to be. All of that said, there's just something about pre-preg that does put it top of the list for me. I get excited about producing a new pre-preg component in a way that doesn't really happen with infusion anymore. Infusion is bread and butter, pre-preg is caviar - you probably don't need to eat caviar for breakfast lunch and dinner, but you'd give it a thought if it was an option 😉 +x+x+x+xI would like to interrupt and tell my (and many others) opinion. first of all the "size" of your pump is completely irrelevant as long as you are not making bigger boat hulls, or something similar in size. Pumps with bigger volume output are only faster to pull down bigger bags, but for car part sized moulds we are talking about a minute or two maximum. The final pressure will be the same. Secondly and most important it is absolutely crucial not to apply full vacuum when vacuum bagging after wet layup. Full vacuum will degas the resin inside your part and will result in pinholes, the effect described. Thirdly when dealing with pinholes gelcoat will make the problem worse. The air bubbles will be there all the same, but under under the gelcoat. So you will need to sand trough the gelcoat to fill them. Last but not least, I would almost always prefer vacuum infusion over wet layup with vacuum bagging. In the end it is the same effort, but the result is better and much more consistent. Wet layup only makes sense to me if you haven't got a vacuum setup. If you bag the part, you could as well profit from infusion with all its benefits and don't mess around with resin. Hi Oekmont, Thanks for your input. So if you don't apply full vacuum, how to you determine how much you should apply ? Do you have any standard reference for wet layup, if using a adjusting gauge ? OK for infusion...I have never tried. Thing is that I have 5 kg of standard epoxy right now...so I kind of want to finish it before buying infusion epoxy. My worry with infusion was that the parts I am making are sometime fairly complicated, with some angles, and applying the dry carbon on them, with different layer and then vacuum that for the infusion...I was wondering if then you would use some fixative spray ?
Now do you think infusion is easier than prepreg ? I am busy with a friend building an oven for prepreg that will be properly controlled, because I thought pre-preg would be easier and cleaner to operate. Or am I wrong ?
Thanks again! Personally, prepreg is the way to go. No messy resin that has a limited pot life, no complicated piping and resin reservoirs. A MUCH quicker curing process. Fabric that sticks to the mould without recourse to adhesives. The only downsides I can think of (there are probably more and there must be some advantages that somone will no doubt point out :-) ) are that dry cloths drape better than prepreg so complicated shapes and tight internal corners take a little more work to get right and you need a suitable oven to fit whatever you are making into. I don't miss wet lay or infusion at all but each to his own. As an example, when making small panels using an aluminium mould, the time taken from the finished mould to pulling the piece off of the mould after curing is around 2.5 hours. Half hour to lay up carbon and bag. Half hour or so to raise to curing temp of 120 deg C at 3 deg a minute, then one hour dwell at this temp. Leave to cool for 30 minutes then remove from oven and extract part from the mould. Compare that to wet lay or resin infusion :-) Totally agree, pre-preg is just a joy... But have you ever tried to layup a 5sqm rear clam on a 35 degree day? You'll be cursing the stuff then! Haha. Seriously though, infusion has it's place, and for me it is larger structures. Laying up a bonnet, you can throw all the layers including consumables on in 10 minutes, then use the vacuum to get everything in place. If you tried to do a large bonnet with pre-preg, not only is it a nightmare to get the material in place, but you also need to spend a good bit of time making sure you haven't got any bridging or unconsolidated areas, as the vacuum won't help you. So where the properties of pre-preg help you to complete a small complex layup, they can fight you when trying to complete a larger layup. Of course, if your bonnet was very complex with lots of louvres and vents, then it could be easier again with pre-preg. Tooling can also be an issue. Nice and easy to make small high temp tooling, but making high temp tooling for full vehicle panels or boat hulls can be not only obscenely expensive, but also more difficult to construct. You have to start thinking about the tool not being able to support its own weight and distorting, so do you make a support structure? But then support structures can print onto the surface badly, or cause their own distortion issues due to differences in CTE. Heat really adds a whole new level of complication to composite production that can really bite you if you don't plan well. I try to be retrospective with every part I make, and use the different techniques and processes to my advantage. That's why they exist, to make production easier. If you choose to use a method that isn't entirely suited to the component you're making, then you're just making life more difficult than it needs to be. All of that said, there's just something about pre-preg that does put it top of the list for me. I get excited about producing a new pre-preg component in a way that doesn't really happen with infusion anymore. Infusion is bread and butter, pre-preg is caviar - you probably don't need to eat caviar for breakfast lunch and dinner, but you'd give it a thought if it was an option 😉 Hi Hanaldo,, Thanks for your feedback. For me, all the parts I am doing are small parts for racing motorcycle (and I am not even doing the fairings...only internal parts, brackets etc...). So they are small and usually complex. So for me, pre-preg seems like the best option. I have never done infusion but I will definitively consider it if I end up one of these days making larger parts. Pre-preg is certainly your best option then.
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Steve Broad
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Group: Forum Members
Posts: 408,
Visits: 4.1K
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+x+x+x+xI would like to interrupt and tell my (and many others) opinion. first of all the "size" of your pump is completely irrelevant as long as you are not making bigger boat hulls, or something similar in size. Pumps with bigger volume output are only faster to pull down bigger bags, but for car part sized moulds we are talking about a minute or two maximum. The final pressure will be the same. Secondly and most important it is absolutely crucial not to apply full vacuum when vacuum bagging after wet layup. Full vacuum will degas the resin inside your part and will result in pinholes, the effect described. Thirdly when dealing with pinholes gelcoat will make the problem worse. The air bubbles will be there all the same, but under under the gelcoat. So you will need to sand trough the gelcoat to fill them. Last but not least, I would almost always prefer vacuum infusion over wet layup with vacuum bagging. In the end it is the same effort, but the result is better and much more consistent. Wet layup only makes sense to me if you haven't got a vacuum setup. If you bag the part, you could as well profit from infusion with all its benefits and don't mess around with resin. Hi Oekmont, Thanks for your input. So if you don't apply full vacuum, how to you determine how much you should apply ? Do you have any standard reference for wet layup, if using a adjusting gauge ? OK for infusion...I have never tried. Thing is that I have 5 kg of standard epoxy right now...so I kind of want to finish it before buying infusion epoxy. My worry with infusion was that the parts I am making are sometime fairly complicated, with some angles, and applying the dry carbon on them, with different layer and then vacuum that for the infusion...I was wondering if then you would use some fixative spray ?
Now do you think infusion is easier than prepreg ? I am busy with a friend building an oven for prepreg that will be properly controlled, because I thought pre-preg would be easier and cleaner to operate. Or am I wrong ?
Thanks again! Personally, prepreg is the way to go. No messy resin that has a limited pot life, no complicated piping and resin reservoirs. A MUCH quicker curing process. Fabric that sticks to the mould without recourse to adhesives. The only downsides I can think of (there are probably more and there must be some advantages that somone will no doubt point out :-) ) are that dry cloths drape better than prepreg so complicated shapes and tight internal corners take a little more work to get right and you need a suitable oven to fit whatever you are making into. I don't miss wet lay or infusion at all but each to his own. As an example, when making small panels using an aluminium mould, the time taken from the finished mould to pulling the piece off of the mould after curing is around 2.5 hours. Half hour to lay up carbon and bag. Half hour or so to raise to curing temp of 120 deg C at 3 deg a minute, then one hour dwell at this temp. Leave to cool for 30 minutes then remove from oven and extract part from the mould. Compare that to wet lay or resin infusion :-) Totally agree, pre-preg is just a joy... But have you ever tried to layup a 5sqm rear clam on a 35 degree day? You'll be cursing the stuff then! Haha. Seriously though, infusion has it's place, and for me it is larger structures. Laying up a bonnet, you can throw all the layers including consumables on in 10 minutes, then use the vacuum to get everything in place. If you tried to do a large bonnet with pre-preg, not only is it a nightmare to get the material in place, but you also need to spend a good bit of time making sure you haven't got any bridging or unconsolidated areas, as the vacuum won't help you. So where the properties of pre-preg help you to complete a small complex layup, they can fight you when trying to complete a larger layup. Of course, if your bonnet was very complex with lots of louvres and vents, then it could be easier again with pre-preg. Tooling can also be an issue. Nice and easy to make small high temp tooling, but making high temp tooling for full vehicle panels or boat hulls can be not only obscenely expensive, but also more difficult to construct. You have to start thinking about the tool not being able to support its own weight and distorting, so do you make a support structure? But then support structures can print onto the surface badly, or cause their own distortion issues due to differences in CTE. Heat really adds a whole new level of complication to composite production that can really bite you if you don't plan well. I try to be retrospective with every part I make, and use the different techniques and processes to my advantage. That's why they exist, to make production easier. If you choose to use a method that isn't entirely suited to the component you're making, then you're just making life more difficult than it needs to be. All of that said, there's just something about pre-preg that does put it top of the list for me. I get excited about producing a new pre-preg component in a way that doesn't really happen with infusion anymore. Infusion is bread and butter, pre-preg is caviar - you probably don't need to eat caviar for breakfast lunch and dinner, but you'd give it a thought if it was an option 😉 Laying prepeg in 35 degrees C? It must be like trying to line up the stuff covered with impact adhesive :-) One advantage I have is I paint my carbon. This means that I don't have to worry about lining up the grain so I can make up large areas using narrow strips. This roof is contructed of 200gsm prepreg. The main area is made up of 2 layers of 250mm wide strips ovelaped by 20mm and laid at 90 degrees to each other. The window surrounds have 5 layers made from narrow strips. Using strips makes handling and positioning relatively easy but, as you say, the trick is keeping it in the tight corners. I have finally managed to stop myself making the bags just big enough and they are now way oversized so I have plenty of material to push into the corners. Building up vacuum gradually (and often releasing and starting again) is the trick to getting the carbon to sit properly into the tight bits as the release agent is trying to do its job :-)  What you must remember to do with pregpreg is to remove all of the backing material. As you can just see to the bottom left of the rear screen I failed :-) 
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