+x

 

Chands - 7/22/2019 9:53:59 AM

I have been playing with Vacuum Bagging of kite boards for a couple of years, and fairly happy with results.  People kept telling me to go to Vacuum Infusion, and I would get a better finish on my board bases, we get a significant amount of pinholes.  I finally conceded and have made three boards and run a number of tests so far.  The last board had a the best base finish I have ever had so must admit it is worth chasing.  But the problem I am having is gas in the upper layers nearest the distribution media.  I suspect out gassing as the cause from something in the layup (the bag was tested for 30 minutes and no loss).  
I tested the PE tubing and spiral tubing in a vacuum with it submerged under Vacuum oil in a glass container and observed through the perspex lid.  These materials out gassed at -98kPa for more than 4 hours and could tell it was the tube as almost all bubbles initiated from either the inside or outside surface of the tube.  I tried cooking the PE tubing at 80 degrees C for 10 hours and retested. Same result.  
I then tested the core medium which is known for out gassing.  Extruded Polystyrene (XPS) at 40kg/m3.  Again it showed significant outgassing in the Vacuum Oil.  In case the vacuum oil was causing the out gassing I reran the test using the Vacuum Infusion Epoxy.  Exactly the same result.  
I have not tested the flow medium.  
Anyways, I am thinking maybe running the vacuum for like 6 hours before releasing the epoxy might help (my next attempt). Anyone come across similar problems?
I am taking the epoxy up to full vacuum prior to releasing into lay up.  It has a significant amount of outgassing/air bubbles.  It takes perhaps 4 minutes at full rough vacuum to get the majority of the bubbles to the surface then another few minutes for them to dissipate.  I then release the epoxy at -70kPa to keep back pressure (or is it vacuum......) on the layup during infusion (its in a separate vacuum chamber) so only giving 28kPa differential to effect flow.  It takes 35 minutes from start release to get flow over the width of the board.  To overcome the PE outgassing I have moved the epoxy pot up near the ceiling to create a air/gas pocket to trap any non-liquids there before entering the layup.  This worked well on the last board with about a metre of gas captured in this area. I did the same with the vacuum side (ladder in the photo).  But still got bubbles/gas in the upper layers of layup.
1) Is there any surface treatment I can apply to the XPS prior to layup that will stop/reduce outgassing?
2) Is there any procedure I can degas the PE tubing before using
3) What other tube material can I use that won't out gas?
Cheers for your help!
Chands

+x

 

Lester Populaire - 7/22/2019 3:34:33 PM

+x

 

Chands - 7/22/2019 9:53:59 AM

I have been playing with Vacuum Bagging of kite boards for a couple of years, and fairly happy with results.  People kept telling me to go to Vacuum Infusion, and I would get a better finish on my board bases, we get a significant amount of pinholes.  I finally conceded and have made three boards and run a number of tests so far.  The last board had a the best base finish I have ever had so must admit it is worth chasing.  But the problem I am having is gas in the upper layers nearest the distribution media.  I suspect out gassing as the cause from something in the layup (the bag was tested for 30 minutes and no loss).  
I tested the PE tubing and spiral tubing in a vacuum with it submerged under Vacuum oil in a glass container and observed through the perspex lid.  These materials out gassed at -98kPa for more than 4 hours and could tell it was the tube as almost all bubbles initiated from either the inside or outside surface of the tube.  I tried cooking the PE tubing at 80 degrees C for 10 hours and retested. Same result.  
I then tested the core medium which is known for out gassing.  Extruded Polystyrene (XPS) at 40kg/m3.  Again it showed significant outgassing in the Vacuum Oil.  In case the vacuum oil was causing the out gassing I reran the test using the Vacuum Infusion Epoxy.  Exactly the same result.  
I have not tested the flow medium.  
Anyways, I am thinking maybe running the vacuum for like 6 hours before releasing the epoxy might help (my next attempt). Anyone come across similar problems?
I am taking the epoxy up to full vacuum prior to releasing into lay up.  It has a significant amount of outgassing/air bubbles.  It takes perhaps 4 minutes at full rough vacuum to get the majority of the bubbles to the surface then another few minutes for them to dissipate.  I then release the epoxy at -70kPa to keep back pressure (or is it vacuum......) on the layup during infusion (its in a separate vacuum chamber) so only giving 28kPa differential to effect flow.  It takes 35 minutes from start release to get flow over the width of the board.  To overcome the PE outgassing I have moved the epoxy pot up near the ceiling to create a air/gas pocket to trap any non-liquids there before entering the layup.  This worked well on the last board with about a metre of gas captured in this area. I did the same with the vacuum side (ladder in the photo).  But still got bubbles/gas in the upper layers of layup.
1) Is there any surface treatment I can apply to the XPS prior to layup that will stop/reduce outgassing?
2) Is there any procedure I can degas the PE tubing before using
3) What other tube material can I use that won't out gas?
Cheers for your help!
Chands

Do you have a picture of the result? And how/where you placed the flow media? I have the feeling it is more related to the vacuum setup and not outgassing. This is usually less of a problem as you have full vacuum only at the flow front.
Infusions with core in one go can be tricky. But it is very satisfying to demould a kiteboard with a mirror finish. I built a lot of kiteboards in the past, but stopped kitesurfing.

Cheers

+x

 

Chands - 7/23/2019 2:37:03 AM

+x

 

Lester Populaire - 7/22/2019 3:34:33 PM

+x

 

Chands - 7/22/2019 9:53:59 AM

I have been playing with Vacuum Bagging of kite boards for a couple of years, and fairly happy with results.  People kept telling me to go to Vacuum Infusion, and I would get a better finish on my board bases, we get a significant amount of pinholes.  I finally conceded and have made three boards and run a number of tests so far.  The last board had a the best base finish I have ever had so must admit it is worth chasing.  But the problem I am having is gas in the upper layers nearest the distribution media.  I suspect out gassing as the cause from something in the layup (the bag was tested for 30 minutes and no loss).  
I tested the PE tubing and spiral tubing in a vacuum with it submerged under Vacuum oil in a glass container and observed through the perspex lid.  These materials out gassed at -98kPa for more than 4 hours and could tell it was the tube as almost all bubbles initiated from either the inside or outside surface of the tube.  I tried cooking the PE tubing at 80 degrees C for 10 hours and retested. Same result.  
I then tested the core medium which is known for out gassing.  Extruded Polystyrene (XPS) at 40kg/m3.  Again it showed significant outgassing in the Vacuum Oil.  In case the vacuum oil was causing the out gassing I reran the test using the Vacuum Infusion Epoxy.  Exactly the same result.  
I have not tested the flow medium.  
Anyways, I am thinking maybe running the vacuum for like 6 hours before releasing the epoxy might help (my next attempt). Anyone come across similar problems?
I am taking the epoxy up to full vacuum prior to releasing into lay up.  It has a significant amount of outgassing/air bubbles.  It takes perhaps 4 minutes at full rough vacuum to get the majority of the bubbles to the surface then another few minutes for them to dissipate.  I then release the epoxy at -70kPa to keep back pressure (or is it vacuum......) on the layup during infusion (its in a separate vacuum chamber) so only giving 28kPa differential to effect flow.  It takes 35 minutes from start release to get flow over the width of the board.  To overcome the PE outgassing I have moved the epoxy pot up near the ceiling to create a air/gas pocket to trap any non-liquids there before entering the layup.  This worked well on the last board with about a metre of gas captured in this area. I did the same with the vacuum side (ladder in the photo).  But still got bubbles/gas in the upper layers of layup.
1) Is there any surface treatment I can apply to the XPS prior to layup that will stop/reduce outgassing?
2) Is there any procedure I can degas the PE tubing before using
3) What other tube material can I use that won't out gas?
Cheers for your help!
Chands

Do you have a picture of the result? And how/where you placed the flow media? I have the feeling it is more related to the vacuum setup and not outgassing. This is usually less of a problem as you have full vacuum only at the flow front.
Infusions with core in one go can be tricky. But it is very satisfying to demould a kiteboard with a mirror finish. I built a lot of kiteboards in the past, but stopped kitesurfing.

Cheers

I don't have a photo of the flow media placement but I stopped it about 4cm before the spiral vacuum tube side of the board just leaving peel ply for the epoxy to flow through for this final distance.  The epoxy front moved uniformly across the board over about 35 minutes and was looking like a very nice wet out (couldn't see these air/gas bubbles at this point).  The board was wetted out horizontally, and once the epoxy reached all of the board I shut off the epoxy supply and tipped the board on its side so that the tubes had a straight line to capture gases after this point (if wouldn't have needed to do this if I had made the bag longer).  The side of the board that was highest (epoxy feed side) had the worst air/gas bubbles.  There were no bubbles visible anywhere in the system while the epoxy was flowing, but soon after stopping the flow I saw bubbles in the PE tubing.  You could actually see these bubbles initiating/forming on the inner surface of the PE tube.  I have had many leaks in bags before (3 years of vacuum bagging, perhaps 300 bags, have used 500m of lay flat tubing to date) and I am fairly certain there were no leaks in this bag.  I monitor the vacuum pumps closely and their performance would support that there were no leaks. Hence I am thinking out gassing.
Here is a photo of the problem

And a photo across the top of the board



And one of the base

So I think the bubbles formed after shutting down the epoxy feed, and the side which is worse is simply due to gravity attracting the bubbles upwards.

+x

 

Chands - 7/23/2019 2:48:33 AM

+x

 

Chands - 7/23/2019 2:37:03 AM

+x

 

Lester Populaire - 7/22/2019 3:34:33 PM

+x

 

Chands - 7/22/2019 9:53:59 AM

I have been playing with Vacuum Bagging of kite boards for a couple of years, and fairly happy with results.  People kept telling me to go to Vacuum Infusion, and I would get a better finish on my board bases, we get a significant amount of pinholes.  I finally conceded and have made three boards and run a number of tests so far.  The last board had a the best base finish I have ever had so must admit it is worth chasing.  But the problem I am having is gas in the upper layers nearest the distribution media.  I suspect out gassing as the cause from something in the layup (the bag was tested for 30 minutes and no loss).  
I tested the PE tubing and spiral tubing in a vacuum with it submerged under Vacuum oil in a glass container and observed through the perspex lid.  These materials out gassed at -98kPa for more than 4 hours and could tell it was the tube as almost all bubbles initiated from either the inside or outside surface of the tube.  I tried cooking the PE tubing at 80 degrees C for 10 hours and retested. Same result.  
I then tested the core medium which is known for out gassing.  Extruded Polystyrene (XPS) at 40kg/m3.  Again it showed significant outgassing in the Vacuum Oil.  In case the vacuum oil was causing the out gassing I reran the test using the Vacuum Infusion Epoxy.  Exactly the same result.  
I have not tested the flow medium.  
Anyways, I am thinking maybe running the vacuum for like 6 hours before releasing the epoxy might help (my next attempt). Anyone come across similar problems?
I am taking the epoxy up to full vacuum prior to releasing into lay up.  It has a significant amount of outgassing/air bubbles.  It takes perhaps 4 minutes at full rough vacuum to get the majority of the bubbles to the surface then another few minutes for them to dissipate.  I then release the epoxy at -70kPa to keep back pressure (or is it vacuum......) on the layup during infusion (its in a separate vacuum chamber) so only giving 28kPa differential to effect flow.  It takes 35 minutes from start release to get flow over the width of the board.  To overcome the PE outgassing I have moved the epoxy pot up near the ceiling to create a air/gas pocket to trap any non-liquids there before entering the layup.  This worked well on the last board with about a metre of gas captured in this area. I did the same with the vacuum side (ladder in the photo).  But still got bubbles/gas in the upper layers of layup.
1) Is there any surface treatment I can apply to the XPS prior to layup that will stop/reduce outgassing?
2) Is there any procedure I can degas the PE tubing before using
3) What other tube material can I use that won't out gas?
Cheers for your help!
Chands

Do you have a picture of the result? And how/where you placed the flow media? I have the feeling it is more related to the vacuum setup and not outgassing. This is usually less of a problem as you have full vacuum only at the flow front.
Infusions with core in one go can be tricky. But it is very satisfying to demould a kiteboard with a mirror finish. I built a lot of kiteboards in the past, but stopped kitesurfing.

Cheers

I don't have a photo of the flow media placement but I stopped it about 4cm before the spiral vacuum tube side of the board just leaving peel ply for the epoxy to flow through for this final distance.  The epoxy front moved uniformly across the board over about 35 minutes and was looking like a very nice wet out (couldn't see these air/gas bubbles at this point).  The board was wetted out horizontally, and once the epoxy reached all of the board I shut off the epoxy supply and tipped the board on its side so that the tubes had a straight line to capture gases after this point (if wouldn't have needed to do this if I had made the bag longer).  The side of the board that was highest (epoxy feed side) had the worst air/gas bubbles.  There were no bubbles visible anywhere in the system while the epoxy was flowing, but soon after stopping the flow I saw bubbles in the PE tubing.  You could actually see these bubbles initiating/forming on the inner surface of the PE tube.  I have had many leaks in bags before (3 years of vacuum bagging, perhaps 300 bags, have used 500m of lay flat tubing to date) and I am fairly certain there were no leaks in this bag.  I monitor the vacuum pumps closely and their performance would support that there were no leaks. Hence I am thinking out gassing.
Here is a photo of the problem

And a photo across the top of the board



And one of the base

So I think the bubbles formed after shutting down the epoxy feed, and the side which is worse is simply due to gravity attracting the bubbles upwards.

I forgot to mention the epoxy is EPOTEC YD LV535 and hardener 7257 which has a pot life at 20 degrees (we use air conditioning to keep this temperature) of 360-420 minutes and a 1mm thick gel time of 10 to 12 hours.  We let the epoxy cure at room temperature for 6 hours then place in an oven at 70 deg Celsius for 6 hours. We run a -95kPa to -92.5kPa vacuum for the full 12 hours.  The amount of gas caught in the upper PE tubing stopped growing after about 3 hours.  Almost all of the growth was in the first 40 minutes.