Vacuum infusion snowboard layup

[TimW]

I build boards using vacuum infusion and I thought I'd share the process here for those interested. If you have no experience with vacuum infusion I don't recommend starting with this because impermeable layers (core, topsheet) make it a tricky infusion. Get some experience with infusion first. It does make for a nice clean process if you build with vacuum.

About my board building efforts: I built ~10 boards(over ~18 years), all except the first two with vacuum infusion. Most of my boards are alpine carving boards, typically carbon or carbon/titanal layups. The boards in the pictures below is a board for my daughter, 145 x24 cm, triax glass laminate, sublimated PA12 topsheet. The resin us Epikote RIMR135 / RIMH137

My mould consists of a 1.5mm stainless steel plate which I bend to the camber/rocker profile I want. The middle 140 cm is glued to a 22mm MDF plate to ensure a smooth curve (140 cm is my minimum running length ). Tip and tail section are free to allow a tighter curve. Because this board is shorter, I made a ramp out of plywood for the tail.

Mould with plywood ramp and tacky tape:

01_mould - kopie (Gemiddeld).jpg (122.54 KiB) Viewed 15244 times

Base with edges:

03_base - kopie (Gemiddeld).jpg (126.83 KiB) Viewed 15244 times

I use 30gsm glass fleece for better resin flow and for flow between impermeable layers. Here I use it to get resin between the edge and the VDS foil. (Glass fabrics have good flow, for carbon I often add glass fleece to improve flow).
Base with fleece and VDS:

04_fleece_VDS - kopie (Gemiddeld).jpg (134.02 KiB) Viewed 15244 times

Triax glass 750 gsm:

05_Triax_bottom - kopie (Gemiddeld).jpg (152.61 KiB) Viewed 15244 times

This core I attached the tip and tail spacers, normally I have them separate. I drilled small 2mm holes to allow resin to flow between top and bottom:

06_core - kopie (Gemiddeld).jpg (138.84 KiB) Viewed 15244 times

More to follow

[TimW]

Top triax layer

07_triax_top - kopie (Gemiddeld).jpg (155.76 KiB) Viewed 15240 times

I drilled some small holes in the topsheet between the inserts and in the center (hardly visible). This is where vacuum is applied and the resin comes out at the end of the infusion

08_topsheet - kopie (Gemiddeld).jpg (110.38 KiB) Viewed 15240 times

I supply resin from the tip and tail. So the flow is from the circumference of the board towards the center. This creates the shortest flow path with the largest resin front. In earlier builds I had the flow from tail to tip, but then the infusion took longer and was more tricky to get right and get a perfect laminate.

rear resin supply. The spiral tube spreads the resin around the tail, ~30 along the sides

09_rear_supply - kopie (Gemiddeld).jpg (151.4 KiB) Viewed 15240 times

The same for the tip:

10_supply_nose - kopie (Gemiddeld).jpg (200.26 KiB) Viewed 15240 times

11_supply_nose2 - kopie (Gemiddeld).jpg (183.81 KiB) Viewed 15240 times

[TimW]

Next a foil is place to separate the resin area from the vacuum. I use a semi-permeable membrame that is permeable to air but not to resin (like gore-tex). This would allow any air bubbles in the resin supply, or leakage from the mould edge, to go directly to vacuum without having to go through the laminate. It thereby adds some safety but you could use a simple foil instead. I actually think it did not make any difference on my last few builds.

Membrane with a cutout in the center where the resin outlets are. The circumference of the cutout is taped to the topsheet with packing tape (I used tacky tape in the past, but because of the thickness it left an imprint in the topsheet). Tacky tape is placed on the edges of the membrane to seal it against the vacuum foil later.

12_membrane - kopie (Gemiddeld).jpg (142.39 KiB) Viewed 15240 times

Vacuum line with breather. Vacuum line is placed next to the board so you do not get any imprints. A uniform layer on the topsheet ensures a smooth surface.

13_vacuum line - kopie (Gemiddeld).jpg (129.69 KiB) Viewed 15240 times

Vacuum foil and vacuum applied. The vacuum foil is sealed with tacky tape both to the membrane and the mould edges. This way we have the inlet area below the membrane and the vacuum area on top. (supply lines clamped shut)

14_vacuum_applied - kopie (Gemiddeld).jpg (115.94 KiB) Viewed 15240 times

The beauty of this process is that you now have time to carefully check for leaks, and check/feel if the core is still aligned properly. There is a vacuum vessel in the line between the mould and pump. I close the vessel and shutdown the pump to listen for leaks and check if the vacuum remains.

Degassing of the resin. You need a deep vacuum!. The picture is at the end of degassing, but at the start the resin foams all the way to the top of the vase.

15_degassing - kopie (Gemiddeld).jpg (180.48 KiB) Viewed 15240 times

Resin supply lines in the resin pot. The resin is placed on the ground, creating 1m static head to keep some vacuum behind the resin front.

16_supply_lines_in_resin - kopie (Gemiddeld).jpg (230.11 KiB) Viewed 15240 times

[TimW]

Next step is to open the resin lines and let the resin flow!

Resin entering at the tail

17_resin_flow - kopie (Gemiddeld).jpg (206.92 KiB) Viewed 15240 times

And at the tip:

18_resin_flow2 - kopie (Gemiddeld).jpg (188.71 KiB) Viewed 15240 times

The drawback of using the membrane and a non-transparent topsheet is that you cannot really see and follow the progress of the infusion. After about 45 minutes, the resin comes through, as can be seen from the resin coming through the holes in the topsheet. Time to close the supply lines.

19_resin_through - kopie (Gemiddeld).jpg (206.44 KiB) Viewed 15240 times

The flow continues a bit when the vacuum equalizes over the mould after closure of the supply. Some additional resin comes out (photo after postcure)

20_after_curing - kopie (Gemiddeld).jpg (136.69 KiB) Viewed 15240 times

And after postcure and removal of the vacuum foil and membrane (the membrane backside serves as a peelply). Note the supply line spiral hose in the laminate beyond the tip and tail.

21_membrane_removed - kopie (Gemiddeld).jpg (142.59 KiB) Viewed 15240 times

[TimW]

And the end result:

22_finished - kopie (Gemiddeld).jpg (142.83 KiB) Viewed 15237 times

Perfect result. The only flaw is discoloration of the topsheet. Still not sure what caused that, never had this issue before.

[chrismp]

Thanks for this detailled write-up and the photos! I have only built surfboards with vacuum infusion, which is a simpler process as you don't have any impermeable layers. It's a great alternative for home builders that would like to keep the sticky mess with epoxy to a minimum.

The topsheet discoloration is strange. Are you using sublimated topsheet? Maybe the colors were not as dense in the middle of the board and the color of the cured resin/core is showing through the topsheet.

[TimW]

Yes it is a sublimated PA12 topsheet. Don't understand what it is. I built two boards with such topsheets before and they were perfect.

[chrismp]

Alright, then my guess would be what I already mentioned. I think something went wrong during sublimation which caused the ink to not transfer properly into the topsheet and now you're seeing the layers beneath the topsheet shine through. Looks kinda like a resin swirl on a surfboard

[SleepingAwake]

Thanks for the write up! I built kiteboards in infusion
and helped building entire race car bodies this way but never attempted a ski or snowboard. Was always afraid the edge bonding not being great. Do you have some long term experience with this?

[TimW]

Edge bonding is fine, several boards with 20+ days on them. Without VDS actually, only started using that recently.

I once had an edge come loose hitting a rock. I opened up the split with a knife, injected resin with a syringe and clamped it. Still using that board, it rides great and re-energized my boardbuilding efforts.

It was my first titanal-carbon laminate and infusion took a bit too long, ~4 hours, so laminate quality may have had some influence. I started using the glass fleece after that on carbon laminates to help resin flow.

20210130_172454.jpg (741.33 KiB) Viewed 15180 times

[Aïdan]

Hello,
I've been thinking over and over how to achieve a fusion process for skis... Infuse separately base and top, open before curing, put the core and re-vacuum, time consuming, a lot of waist material...mmh, never tried.
And you made it happen ! Simple in one shot, I'm amazed. For skis I will try to have a monobloc core as if it was a snowboard except for tips and tails where I want it to be (semi) cap . Any suggestion for skis ?
What is the name of the specific foil you use to separate top vacuum from bottom feed areas, where did you get it ? I've seen some ose that have similar properties but no foil yet. I'm in France and buy some stuff here and some from Germany.
About hole distribution in the core, did you try different sizes, distances between holes to get there ? (it seems to me that you have a minimal amount of holes in regard of the usual cores that exist on the market to make sandwich panels, which is good, we don't want to perforate too much our wood-cores in order to keep their mechanical properties ). I suppose that you don't aline the holes of the core with the holes of the top sheet ? Or it doesn't really matter ?
What is the pot life of the resin you use ?
Have you ever tried flax fiber ?

Thanks for sharing your experience

[TimW]

I'd expect the same would work for skis. I would just do two in parallel and run the supply line also 30cm between the ski ends.

IIRC the membrane is Dahltexx® SP-2 from Airtech (they sent me a generous sample for a PhD student's project) Don't know if there are other sources than directly from Airtech.

Resin is Epikote RIMR135 / RIMH138, about 5 hours pot life. (Way more than needed)

The holes I drill quite randomly. Early on I just did them along the centerline, nowadays I do more as they never hurt. But ever since I did the supply line around the tip and tail and the vacuum from the center I never had issues, I think a single hole in the center would also work. It's just better safe than sorry.

I have no experience with flax

[mammuth]

Yes it is a sublimated PA12 topsheet. Don't understand what it is. I built two boards with such topsheets before and they were perfect.

Did you use a backcoat on the topsheet?

If not, then here is your problem. Experienced the same with dark full sublimated TS & base. Without the backcoat the heat from the press start the sublimation process again and the color from the TS/base gets into the resin. I could see this on the black resin coming out of the ski (the resin was not colored)

[TimW]

Yes I did backcoat it.

The supplier gave me a new topsheet for free. Another customer had the same issue with a topsheet printed at the same time. They suspect there was something wrong with the ink.

[Aïdan]

Hello,

One last question, what are the specs of your vacuum pump ? Must be powerful no ?

thanks again for the share