bad US Foam blank/ bad glass job

Just had a board delivered from the glasser the other day, surfed it a few times and the foam started expanding underneath the glass.  The glass is still attached to the stringer it is the foam that looks like it is expanding / off gassing underneath the glass creating a valley with the stringer at the valley bottom.  There is some yellowing going on with the expanding area,  it affects the top and bottom of the board with the top/deck seeing the most foam expansion.  Is it tha bad  blank or the glass job? Anyone have any issues with US blanks doing this? I will try to post pictures later 

a couple months ago I ordered 3 USB 6’0P blanks with ply 4mm stringers all in orange formula and all 3 with same modified tail rocker. all were glassed same 4x4+4oz UV poly

after riding for a dozen or so sessions, one of the finished boards shrank along the stringer both top and bottom, an area about two feet long and maybe 3-4 inches out from the stringer, this area turned yellow as well.  Started between the front fins (quad) to about under the chest.  bad glue up I guess?

**hey bud **

 

              how light were they when shaped/?

 

 

 

**  cheers huie
**

I had this happen with an old ecotech blank.  It expanded and blew the nose open - crraacck!  I patched / re-glassed the nose, and it expanded in other areas, now the stringer is a little low, like a very shallow groove in places. 

But I know guys who built boards from the same batch of blanks, and never had a problem one.  I think its done doing whatever its gonna do, and....I love this board!  Its like me - has a few defects, some of them cosmetic, but very functional and gets the job done LOL!  Its only a water toy.  Hope your experience turns out as good as mine.

 

Ice 9 Cane formula used to do this quite often when it was heated up. 

Howzit Huie - I’ve not weighed a shaped blank in a while but I usually weigh the finished board without fins.

this one that shrank along the stringer was (poly) done with 4 FCS fusion plugs, s-glass bottom/warp glass deck 4x4+4oz (with toe patches), sanded hotcoat. 5’7 x 18 3/8 x 2 1/4 weighed in at 5lbs 8oz.

bummed because the board goes really well

seems like it's always a good riding board.  Sucks.  Just keep going.

Stash it and check it out in a couple years.  They can keep going off and morph badly.

Had bennet-dion. surfblanks and us all lightest [less stable?] foam they could make, but only once.

What density were you using?

orange formula.

I should also point out that this is the first time I’ve had this type of failure in almost 6 years since I started around 100 USBlanks shaped glassed sanded in my backyard shed. not really a total failure even - the glass is intact, watertight the board is still very rideable in fact it’s being passed around some friends now.

Any PU foam that is pushed toward the lower limit of density is going to have more of a chance of unstable patches. Usually the bad spots are around the perimeter of blank and therefore end up on the floor anyway. But sometimes they show up in other places, or the whole blank is bad. There's a few ways to detect this before you waste time glassing: 1) most of the time the unstable foam will ''look different'' than rest of blank; somewhat shiny or cell structure looks a little off. 2) bad spots will feel soft or ''spongy''. 3) set the blank aside for a few days after (or during) shaping; if it's going to shrink it will probably start to do so.

This is sort of a random thing, the manufacturers do QC to make sure they don't sell these blanks. But sometimes one that doesn't have any obvious flaws sneaks out to buyers.