XPS at High Altitudes

I made this board about 3 years ago and rode it pretty regularly for a while, and loaned it to visiting friends on occasion after that. XPS bottom, EPS deck glued together with PU glue. We all know about potential bonding issues with XPS, but I just found out that taking the board by car from sea-level to an altitude of about 10,500’ you are asking for trouble! I sold it to a buddy of mine living in Steamboat, CO that takes a few surf trips every year. The plan was to get the board home, then take it to Mex and leave it with a friend. I guess he’s lucky he didn’t get to Mex and find out it popped in flight.

Reason #245 why you don't want to use XPS.

you didn’t drill little holes after you glassed it?

oh, eps deck…

XPS Dow - Bali, Mentawais, Hawaii no problem flying?

 

EPS no vent plug one pin hole ding when it got to hawaii the foam shrank 1/8" down from stringer. (Bottom and Deck)

Which XPS did you use? There’s one from Home Cheapo that is lighter in density. (powder blue) thin sheet.

The blue xps from Dow is the one used for Boat Docks and Sea Ray boat hulls. It comes in 8’ x 2’ x 5.25" billets.

 

 

Resinhead: “Reason #245?” I would think this would be up there in the top ten!

Used 1" thick Dow sheet foam, made for roofing insulation. It’s likely the cheap stuff SD referred to. The board was made to finish out a billet where I had about an inch and a half of usable foam left with the rocker I wanted in it. Glued the Dow foam to the under side of that foam and stuck it in a rocker bed until it set.

I was reminded of a friend of mine who has used more of that foam than anyone I know, never had a problem with it on his personal boards but had issues on some customer’s boards. He loved the stuff, but had too many issues to keep making them for people. I had only a minor bubble that was easily fixed, but I sell it and the thing blows up! Go figure…

While it should have, it never occurred to me that driving it up into the mountains would be an issue. If it had, I probably would have drilled little holes in the bottom.Turns out 10,500’ was the critical limit where it started making popping noises inside the car leading up the big bubble. My buddy’s kids were kind of freaking on it while it was happening. “Dad, what’s going on with your board??? It sounds like a big bowl of Rice Krispies!”

As for flying, aren’t the luggage compartments at least somewhat pressurized?
I was thinking of fitting it with one of PeteC’s goretex vent plugs after repairing it and see if that makes a difference.

Vents won't help on XPS because the gas doesn't move through the blank like EPS. IOW the pressure can't move to the placement of the vent. However, once it delams enough area to get to the vent, it might work (haha).  

Good information.

 

The Dow XPS is a whole different animal than the stuff from the home improvement store.

 

EPS = Vent plug for travel

XPS = No point to add a vent plug like MD say’s.

Surfding, how did you finish shape your XPS? I left mine at 60 grit and if you look closely, you can see little lines in the foam that I put in with a pattern cutter (looked like a mini pizza cutter) to help give the resin something to grip onto.

I’ve heard that heating glassed XPS was the worst thing, but I left it in the back of my truck (with a camper) for months at a time, and I’m sure it got pretty hot on a few occasions. I guess not too hot, though, as the glass only separated the one time and I think it was the indirect result of a rail ding.

I’ve flown with unvented EPS a few times and had no issues at all. Maybe I was lucky?

I’m making the guy a board at cost, I think I’ll vent it just to be safe.

I have made well over 200 XPS boards all with no vent plugs. 60 grit is were I leave them and glass the deck first and let it cure 24 hours before glassing the other side. You don’t want to rush a XPS. Had two go bad from sitting in a hot car in the middle of the day in August. Otherwise they do fine.

EPS I have done well over 400 with one case were the board just sucked in kind of like an over vacuumed glass job.  The board  was done in 2x4 oz deck and a 4oz bottom. The kid had a ding on the bottom and put a sticker over the ding. The dad was pissed at me and I lost a good young grom. So I do 4+6 deck and 2 x 4 bottom with 2.0 or 1.5 EPS. No more problems. Vent plugs are good I think however you need to open them up for the flight and don’t forget to close them before you surf!

XPS doesn’t have linking air channels as does eps (it has random closed air sections), so you can’t vent it.  It does expand just like eps when heated though.  Here’s what happens at altitude:   Consider that the internal board pressure is 14.7 PSI or sea level.  If the ambient air pressure drops to 12.5 PSI (about 5,000 ft), there is a +15% pressure increase in just the air pockets, and much higher with the residual blowing gas in the foam.  This is just like heating up the board, and it will expand.  Solar loading or any other heating under these conditions will drastically accelerate the expansion. If the board is made at altitude and then descends,  the reverse starts to happen and the foam shrinks. The recovery of the foam cells and air pockets from this stress isn’t uniform, some stay big and others shrink.  If the glass is well bonded to the foam, it may shrink down with it.   I went through this analysis for people who build SUP’s for Tahoe at 6,200 ft.  In many parts of Colorado, you can’t even keep a BBQ going because of the altitude.

 

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XPS doesn't have linking air channels as does eps (it has random closed air sections), so you can't vent it.  It does expand just like eps when heated though.  Here's what happens at altitude:   Consider that the internal board pressure is 14.7 PSI or sea level.  If the ambient air pressure drops to 12.5 PSI (about 5,000 ft), there is a +15% pressure increase in just the air pockets, and much higher with the residual blowing gas in the foam.  This is just like heating up the board, and it will expand.  Solar loading or any other heating under these conditions will drastically accelerate the expansion. If the board is made at altitude and then descends,  the reverse starts to happen and the foam shrinks. The recovery of the foam cells and air pockets from this stress isn't uniform, some stay big and others shrink.  If the glass is well bonded to the foam, it may shrink down with it.   I went through this analysis for people who build SUP's for Tahoe at 6,200 ft.  In many parts of Colorado, you can't even keep a BBQ going because of the altitude.

 

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Thanks Pete, that's pretty much as I figured. I told him to punch holes in the de-lam for the return trip, just in case the pressure reversal causes yet another mini catastrophe.

SD, I glass my EPS (2 lb) with a double 4 bottom, and a triple 4 deck. If the rider is heavy footed, I'll add patches where the feet go. With the triple 4 oz  glass schedule, the deck still crushes, but it only goes so far and stops.