I am in the process of building my first board as a first board for my 7yo son. He wants a triple stringer longboard shape complete with nose and tail blocks.
From reading past posts it sounds like venting is essential, but I am concerned that by doing the triple stringer, I am creating 4 isolated volumes of foam that need to be dealt with separately
Do I need to vent each of the 4 chambers separately?
Is there a clean way to allow airflow through stringer without creating other problems?
Venting each chamber sounds pretty logical to me.
With there being multistringers I wouldn’t think that strength would be an issue so I would think that you could drill a series of small holes along the stringers and when you glue them up just don’t use glue in those sections. I would think that multiple vents would look like udders on a cow.
am i missing something here? is the board a composite sandwich or just regular ole EPS and glass? i thought there was no need to vent for the latter.
This is an interesting question so I’d like to throw this out for consumption among all the braniac EPS builders…
About two months ago I was up at Surflight in Waialua describing to Jim Richardson the venting process we had been all instructed about especially regarding blue XPS delams…
Jim kind of smiled at me with a cheshire grin when I questioned about him not using vents on his sealed bluefoam spring cores and he asked me…
How the hell do I know where the gasses want to come out?
And if not, then how does putting in a vent in one area of the board actually prevent a delam in another area of the board where you get gassing under the skin?
Kind of made me wake up and think… yeah how are you guarranteed that all the gassing will release to that one little spot you decide to put your vent in… Again these aren’t hollow boards like Paul’s but fairly solid-like material.
So what gives with venting EPS/XPS boards?
Seems like what Jim said gassing and delams are going to want to occur where ever it wants to unless the skin is never bonded to the core in the first place. Something Bert forgot to mention… Maybe his shells are only secured to the solid rails with a thin air layer in between the core and the skin. But in this scenerio you aren’t worried about delams, only not blowing up
I bet you someone can confirm that even with a vent they are getting delams somewhere else on the board…
What do I know… I haven’t even done EPS #1.
It does make you wonder if any kind of breather material (screen, bubble wrap, paper towels, etc) is necessary during vacuuming. If air can flow between EPS beads for pressure relief, it seems it should do the same under vacuum? If it won’t, then maybe the pressure relief vent theory does seem suspect?
Has anybody tried an open end vacuum bag with a piece of EPS block sealed at the opening to check for leaks through foam? I’m headed to the shop right now. Will report back later.
look to windsurfboards that have been built out of super light eps for years… remove the vent they are fine. leave the vent in they bubble up/delam. eps is a huge pathway of air channels, one “little” hole is all you need but you are better off with it towards the center… xps is different and from what i have read delams because of gasses that are trapped when blown…
I’m back with some answers…
After rigging up a chunk of 1 lb EPS with fiberglass breather material touching both the vacuum fitting and the foam inside an airtight bag I cranked up the vacuum to 18 mm/hg when the pump automatically cut off. The pressure held so I figure I can assume that all the fittings and connections were OK.
I then cut a small square in the side of the bag and taped the edges to the foam leaving a small opening to atmosphere and cranked up the vacuum again.
The gauge reading went to 18mm/hg and the pump cut off again. The vacuum rather quickly decreased and I could hear a faint squealing noise at the opening where the foam was exposed. By wetting my finger with some saliva and touching the exposed foam, it was apparent that vacuum was indeed sucking through the foam and not at the taped edges - the squealing noise changed and I could feel the suction on my fingertip.
My conclusion is that 1 lb EPS foam does indeed breathe and that a vent anywhere on the shell would allow some pressure to escape. Whether or not it will prevent delams somewhere else like under the feet, where repeated stress of impact may hasten the process, is subject to debate.
In a situation like multiple stringers, it seems like a hole in each stringer(unsealed by glue as mentioned) would allow some pressure transfer between chambers and require just one overall vent for pressure relief.
As to whether breather material is needed for vacuum bagging - I’d say it couldn’t hurt. The vacuum would probably pull all around the foam without breather material but perhaps so slowly in areas distant to the vacuum to bag fitting that resin could start to set before adequate vacuum is reached at those areas.
I’d invite anyone to try my experiment and see if they get the same results. Maybe try it with 2 lb EPS as well.
For me, I’ll be using breather material during vacuuming and a vent on my first EPS board.
I just repeated the test using a 2 lb EPS sample I received from SFoam. It’s different than the 1 lb EPS Home Depot foam I first tried. The beads are smaller and tighter and the vacuum did not appear to flow through the test chunk like on the first test. In fact after a couple of minutes, the vacuum gauge did not go down, I could hear no sound and could feel no suction with my finger tip.
I have an email to SFoam in regard to their recommendations (if any) on venting. I’ll post any reply given.
I have not tested XPS foam as I have no samples.
Has anyone else cut open and melted the foam out of an eps vacuumed laminate? What’s left is like a spider web of resin where it flowed beween and around the styro balls, just like the air you are describing.
This helps greatly with general strength, as the fabric, (sandwich material if you use it), sanded surface, and the styro balls themselves are all bonded together.
I highly doubt Bert is doing any sort of unbonded layers. The structure is developed by the bonding of all parts. Some of the parts are obviously more flexy than others. Unbonded beam…house of cards.
In the photo you can see where I spread some paint on the opening. Sure enough, after breaking the foam apart, the paint had penetrated between the beads as you describe.
SFoam website says to mix epoxy/microballon slurry (not water based spackle) and seal the blank to prevent too much resin from soaking in.
Their foam was so much tighter, it seemed like it wouldn’t soak as much resin as the 1 lb density. No paint appeared to penetrate with the 2 lb density. Probably sealing the 1 lb density would be even more important.
I think Bert mentioned that he seals his EPS before lamming to prevent such strict adhesion. That’s when he said you need a vent.
I think he said if you don’t seal your blank with spackle/bog what ever then you don’t need a vent…
John
is that glass container a filter or your vac resevoir?
I see you’re using a backflow valve as well…
I think the key is to get the bonding process up over 120F degrees or more cause Bert said it at a certain value above the temp it was bonded at that the delam or gassing occurs… So it’s good to cook’em hot when your lamming just to prevent any blow throughs later…
Anxious to see Bert’s next gen breakthrough…
I’m thinking semi-claved prefabbed shells attached to the balsa railed shaped using a resin flow method under intense heat gets Bert what he wants. So top and bottom flex independantly and the core is nothing but floatation and a barrier to minimze of tune the flex into the shells.
Probably too starwars but been picking up pieces here and there that indicate it.
My conclusion is that 1 lb EPS foam does indeed breathe and that a vent anywhere on the shell would allow some pressure to escape.
That a pretty slick test you came up with. Its good to have some positive proof that it actually does flow.
Whether or not it will prevent delams somewhere else like under the feet, where repeated stress of impact may hasten the process, is subject to debate.
I think solving this problem comes down to doing a Bert says. Put strength where strength needs to be. I can think of two ways to solve this problem. The first is to prewettout the foam with resin so that it saturates the pores making it more resistant to being pressed in. The second what would be to use an inlay of pvc in the high traffic area under the balsa. I am betting Bert uses the first way. I did this on my shortboard and it seemed plenty stiff.
No need to vent.
You left out important info like what type, density of foam you are using.
The home depot brand insulation EPS is very loose in that the air around the individual beads is great. IF you are going to a full on foam supplier they can give you a “tight bead” EPS for surfboard and you won’t have any more delam problems than a comparable polyester board.
If you vacuum bag the glass to the foam and keep it a light color it will last a really long time.
Can you imagine a 7 year old trying to remember to close three vents prior to going surfing? Vents are also sources for water intrusion.
John
is that glass container a filter or your vac resevoir? - It is just a surplus suction cannister from an ambulance. I bought it for the gauge and as a reservoir in case any resin got sucked into the system.
I see you’re using a backflow valve as well… - I am but you can’t see it in the photo. That black plug thing is a quick release fitting that I just happened to have in my spare parts pile.
I think the key is to get the bonding process up over 120F degrees or more cause Bert said it at a certain value above the temp it was bonded at that the delam or gassing occurs… So it’s good to cook’em hot when your lamming just to prevent any blow throughs later…
I brought up the subject of post cure heat a couple of years back and Greg Loehr didn’t think it was necessary. Room temperature cured epoxy typically softens a bit at higher temps even after seemingly fully cured. Greg said his resin is OK at room temperature cure.
The softening John mentioned is a problem with epoxies that have low heat deflection temperatures. B staging can help increase HDT but instead we formulated ours to be quite high for a room temp. cure and have never seen that problem.
System Three website has a three part article about post curing… check “Post Curing - Part 1, 2 & 3” under “Epoxy Talk” menu. Not sure if this info applies to RR.
http://www.systemthree.com/members/epoxy_talk_f_01.html
The pre-wetout you speak of is the same as sealing the blank. Better to use a slurry of microballoons/qcell than straight resin.
Oneula, I have now scientific evidence to back me up, but if the closed cell extruded EPS doesn’t soak up water from migration through the cells, how does the air (a fluid also)migate out to the vents. It would also seem the pins that melt through the glass and into the foam would further seal the cells that in passes through. Just a wild guess on my part, but the thermo vents DON’T seem to be stopping the delam problem that they were put in for in the first place
Thanks for the tip! I’ll do it that way next time.
Jim, are you talking about the way that the glass bonds to the foam? I would think that this bonding process would aid in directing the air out of the board. My vents go into the middle of the board. When the air tries to escape it would flow through the path of least resisitance which in my case would be the vent hole.
Carl Christianson kindly responded to my inquiry regarding the vent thing. I feel it should be pointed out (as Carl emphasizes) that when discussing “EPS” (EXPANDED Polystyrene, not EXTRUDED - “XPS”) foams, there are different densities and quality. Here is Carl’s response (used with permission from Carl) -
The following response to your email applies to <span style="text-decoration:underline"><span style="font-weight:bold">expanded</span></span> poly styrene
foam only, extruded foam of course is a different matter.
Venting Part 1
It’s probable that the air spaces that exist in a finished
6 or 7 foot blank made of quality #2 EPS, might amount to a cubic inch or two, if that much. It’s hard to image the physics required that would allow that volume
of gas to expand and contract enough to cause an issue, in regards to water
infusion or de-lamination.
With Home Depot foam, I have no idea, we do not think this foam is
suitable for surfboard construction.
In the seven years I have been making EPS blanks and surfboards, I have
seen several thousand EPS / Epoxy boards made in this area alone ( the Texas
Gulf Coast. ) There are some professional builders here that have been producing
EPS / Epoxy boards for over 10 years. These boards typically last twice as long
as polyester / urethane boards and none have ever had any " vents " installed, or
had de-laminations from lack of vents.
There has been a few de-laminations occur, but these were always traced to the use of poor quality foam that was manufactured with poor bead adhesion.
Venting Part 2
I can report that I have never seen any problems with water being "sucked in "
although these boards are ridden in water temperatures from 52 to 85 degrees.
There is some water that will flow into a ding by capillary action, 0.06 milliliters per square inch of exposed foam per hour, by test with our foam. It's evident this isn't much of an issue.
In short, if you want to produce an EPS / Epoxy surfboard of commercial quality you need:
) High quality source of EPS foam. Foam with a tool-able density that
has good adhesion between the beads.
) High quality source of Epoxy resins, specifically designed for surfboard construction.
) Proper sealing of the EPS blank . Builders here use both a 50 /50 mixtures of epoxy /microballons or spackling compounds that have microballons in them. Although both are used with success, the epoxy / microballon sealer had some additional benefits, such as increased deck strength and an epoxy to epoxy laminate bond.