|
Francis Soenen
|
|
|
Group: Forum Members
Posts: 15,
Visits: 264
|
Next week we try to infuse a canoe in flax fabric, a big challenge for me because it's my biggest project for so far. I made a few test panels to figure out the lay-up composition, but it was not completely perfect... I had a few places where the surface was bad, but I have no idea what's the reason. I've worked with MTI hose and clamped off the resin tube when the epoxy reached the MTI. I infused at 13 mbar, so is it possible that the vacuum was to much? I did the infusion very slow, so I don't know what I best can change during the next test? The second picture is the backside where I've put some Corecel ribs, but here I think it was bridging from the peelply. Is it common that they do a post-treatment after an infusion (sanding and varnishing)?  
|
|
|
|
|
Lester Populaire
|
|
|
Group: Forum Members
Posts: 311,
Visits: 13K
|
+xNext week we try to infuse a canoe in flax fabric, a big challenge for me because it's my biggest project for so far. I made a few test panels to figure out the lay-up composition, but it was not completely perfect... I had a few places where the surface was bad, but I have no idea what's the reason. I've worked with MTI hose and clamped off the resin tube when the epoxy reached the MTI. I infused at 13 mbar, so is it possible that the vacuum was to much? I did the infusion very slow, so I don't know what I best can change during the next test? The second picture is the backside where I've put some Corecel ribs, but here I think it was bridging from the peelply. Is it common that they do a post-treatment after an infusion (sanding and varnishing)? To much vacuum is not really a thing for vacuum infusion (with epoxy). The better the vacuum, the less air in the bag, the less issues with porosity. I'm fairly certain that the issue in the first picture is due to uneven resin flow between the two sides of the core. The best way to mitigate is to have resin passages throughout the core vertically, so the flow front can even out. You can drill holes through the core every inch or so. But honestly there is always a risk this will occur in some small section. The fool proof way is to infuse the outer skin first, then bond the core in place, then infuse the inner skin. But this comes with a lot of waste in consumables and resin. The second picture clearly shows bridging. make sure the peel ply (each individual layer really) is firmly pressed against the tooling. Depending on the geometry it helps a lot to have a cut in the fabric and overlap two patches. And regards of post treatment i would always recommend a 2k clear coat for UV and moisture protection. I have quite a bit of experience with flax infusions, so if you're unsure you can also hit me up with a private message. Good luck
|
|
|
|
|
Francis Soenen
|
|
|
Group: Forum Members
Posts: 15,
Visits: 264
|
+x+xNext week we try to infuse a canoe in flax fabric, a big challenge for me because it's my biggest project for so far. I made a few test panels to figure out the lay-up composition, but it was not completely perfect... I had a few places where the surface was bad, but I have no idea what's the reason. I've worked with MTI hose and clamped off the resin tube when the epoxy reached the MTI. I infused at 13 mbar, so is it possible that the vacuum was to much? I did the infusion very slow, so I don't know what I best can change during the next test? The second picture is the backside where I've put some Corecel ribs, but here I think it was bridging from the peelply. Is it common that they do a post-treatment after an infusion (sanding and varnishing)? To much vacuum is not really a thing for vacuum infusion (with epoxy). The better the vacuum, the less air in the bag, the less issues with porosity. I'm fairly certain that the issue in the first picture is due to uneven resin flow between the two sides of the core. The best way to mitigate is to have resin passages throughout the core vertically, so the flow front can even out. You can drill holes through the core every inch or so. But honestly there is always a risk this will occur in some small section. The fool proof way is to infuse the outer skin first, then bond the core in place, then infuse the inner skin. But this comes with a lot of waste in consumables and resin. The second picture clearly shows bridging. make sure the peel ply (each individual layer really) is firmly pressed against the tooling. Depending on the geometry it helps a lot to have a cut in the fabric and overlap two patches. And regards of post treatment i would always recommend a 2k clear coat for UV and moisture protection. I have quite a bit of experience with flax infusions, so if you're unsure you can also hit me up with a private message. Good luck Thanks! I've send you a private message with more details of the project.
|
|
|
|
|
Hanaldo
|
|
|
Group: Forum Members
Posts: 2.5K,
Visits: 28K
|
I'd say the majority of your problem is the bridging. When you've got major bridging like that, it will cause issues not only in that specific area, but also in the rest of the laminate as it causes uneven resin distribution within the laminate.
Be 100% sure you have no bridging on your next test.
|
|
|
|
|
Francis Soenen
|
|
|
Group: Forum Members
Posts: 15,
Visits: 264
|
+xI'd say the majority of your problem is the bridging. When you've got major bridging like that, it will cause issues not only in that specific area, but also in the rest of the laminate as it causes uneven resin distribution within the laminate. Be 100% sure you have no bridging on your next test. Because I have a lot of vertical ribs in the canoe it's difficult to hold them in place. Is tacky spray an option?
|
|
|
|
|
Hanaldo
|
|
|
Group: Forum Members
Posts: 2.5K,
Visits: 28K
|
Sure, but be aware it can also cause you issues if you aren't careful. Some tacky sprays are quite permanent and will lock the materials in place, which means that if you position them with a bit of bridging then the materials won't be able to move around when you pull a vacuum. With infusion, I prefer for all of the materials to be as loose as possible so that the vacuum can do the work. But this isn't always possible, sometimes you do need to use a tacky spray. I like to use tacky sprays that have a temporary hold time, so they hold the materials for an hour or so while your positioning them but then they dry and lose their grip so that when you pull a vacuum the materials can move around easier again. My favourite is TensorGrip TC49, with Aerofix 3 a close second.
|
|
|
|
|
Hanaldo
|
|
|
Group: Forum Members
Posts: 2.5K,
Visits: 28K
|
Decided to post my reply to your PM in here as well, just in case anyone reading this also finds this useful:
Hi Francis,
No problem mate. Yeh unfortunately if you have dry areas as you have experienced, then the entire laminate will be riddled with porosity and sanding the laminate will expose it - as you've experienced. The best way to keep the dust out of those pinholes is to wet-sand instead, so that the dry dust doesn't pack into the porosity. Then it's much easier to clean out.
Your layup sounds fine, there's nothing wrong with that layup. Interesting Gurit have advised you to drill more holes - I use Gurit perforated foam core in 24ft yachts without needing to drill extra holes. What resin system are you using?
MTI hose is a great product, but I do advise not treating it any differently to a regular infusion - it's just there to give you an added layer of security. Follow Easy Composites tutorial video on infusing the Kevlar ice sled. It is important when you do your canoe that your feed line setup is optimised. Don't infuse any further than 500mm - if you do, not only do you risk dry spots, but the vacuum acting on the flow front gets too high and you will have porosity (this is likely what has caused your dry spots near your MTI hose). So break your infusion down into smaller sections no bigger than 500mm. Easy Composites video touches on this, and you can look up videos of 'Staged' infusions as well.
As far as timing on clamping off your resin feeds goes, again look at the Easy Composites tutorial vid for guidance. Yes - I leave the resin feed open for a time after the resin has reached the outlet for cosmetically important parts. The amount of time depends on the size of the infusion - for something the size of a canoe, I would suggest somewhere between 2-5 minutes. So once the resin has completely wet out the laminate and reached your MTI hose, wait 2-5 minutes, and then clamp your resin feed lines. Whether you shut your pump off for this or leave it on is entirely irrelevant - the pump isn't doing anything once the infusion is complete, but it may give you a small layer of protection if you happen to develop a leak right as your finishing the infusion. This is somewhat less the case when using MTI hose though, as the hose effectively seals off as soon as the resin reaches it.
As for your bridging problems, there's really no tricks to this - it's an experience thing. You will work it out as you get more experience. But you need to be taking your time when you pull that initial vacuum and position everything. Pull a partial vacuum, just tight enough for the bag to be pressing against your materials but with enough slack that you can easily slide things around. Starting from the deepest point, and with plenty of bag, press the materials down into the corners. You don't want to feel any sponginess, your bagging stack should feel very firm when you press the corner. If you feel or see the material move or bounce back as you press it in, then you've got bridging. If you need to, let off some vacuum so you can move the materials around easier and press them right into the corner - then pull a higher vacuum while you hold the materials there. Repeat this process as much as you need to to get all of the material into all of the corners until you can't feel any sponginess at all anymore. One bit of bridging is enough to ruin an entire laminate, so be very methodical and don't get impatient. After a bit of time under consolidation, the materials will start to take a pre-form and stay where you want them too, so don't worry when you need to let the vacuum off to sort out another area of bridging. This process can take hours on a large and complex layup, so just take your time with it and you'll get there eventually.
|
|
|
|
|
Francis Soenen
|
|
|
Group: Forum Members
Posts: 15,
Visits: 264
|
+xDecided to post my reply to your PM in here as well, just in case anyone reading this also finds this useful:
Hi Francis,
No problem mate. Yeh unfortunately if you have dry areas as you have experienced, then the entire laminate will be riddled with porosity and sanding the laminate will expose it - as you've experienced. The best way to keep the dust out of those pinholes is to wet-sand instead, so that the dry dust doesn't pack into the porosity. Then it's much easier to clean out.
Your layup sounds fine, there's nothing wrong with that layup. Interesting Gurit have advised you to drill more holes - I use Gurit perforated foam core in 24ft yachts without needing to drill extra holes. What resin system are you using?
MTI hose is a great product, but I do advise not treating it any differently to a regular infusion - it's just there to give you an added layer of security. Follow Easy Composites tutorial video on infusing the Kevlar ice sled. It is important when you do your canoe that your feed line setup is optimised. Don't infuse any further than 500mm - if you do, not only do you risk dry spots, but the vacuum acting on the flow front gets too high and you will have porosity (this is likely what has caused your dry spots near your MTI hose). So break your infusion down into smaller sections no bigger than 500mm. Easy Composites video touches on this, and you can look up videos of 'Staged' infusions as well.
As far as timing on clamping off your resin feeds goes, again look at the Easy Composites tutorial vid for guidance. Yes - I leave the resin feed open for a time after the resin has reached the outlet for cosmetically important parts. The amount of time depends on the size of the infusion - for something the size of a canoe, I would suggest somewhere between 2-5 minutes. So once the resin has completely wet out the laminate and reached your MTI hose, wait 2-5 minutes, and then clamp your resin feed lines. Whether you shut your pump off for this or leave it on is entirely irrelevant - the pump isn't doing anything once the infusion is complete, but it may give you a small layer of protection if you happen to develop a leak right as your finishing the infusion. This is somewhat less the case when using MTI hose though, as the hose effectively seals off as soon as the resin reaches it.
As for your bridging problems, there's really no tricks to this - it's an experience thing. You will work it out as you get more experience. But you need to be taking your time when you pull that initial vacuum and position everything. Pull a partial vacuum, just tight enough for the bag to be pressing against your materials but with enough slack that you can easily slide things around. Starting from the deepest point, and with plenty of bag, press the materials down into the corners. You don't want to feel any sponginess, your bagging stack should feel very firm when you press the corner. If you feel or see the material move or bounce back as you press it in, then you've got bridging. If you need to, let off some vacuum so you can move the materials around easier and press them right into the corner - then pull a higher vacuum while you hold the materials there. Repeat this process as much as you need to to get all of the material into all of the corners until you can't feel any sponginess at all anymore. One bit of bridging is enough to ruin an entire laminate, so be very methodical and don't get impatient. After a bit of time under consolidation, the materials will start to take a pre-form and stay where you want them too, so don't worry when you need to let the vacuum off to sort out another area of bridging. This process can take hours on a large and complex layup, so just take your time with it and you'll get there eventually. Thank you very much for your explication, I have already learned some new things! If I still have some pinholes, what is the best approach to fill the holes? Is it a good idea, during the infusion, to clamp the line for a few minutes and then open it again, so the airbubbles in front of the resin flow can escape? We gonna install the foam ribs and floor after the infusion, so what can you recommend to bond the Corecell? I thought of thicken epoxy with micro balloons or Silica.
|
|
|
|