To my surprise I discovered that one day the complete bottom of my old but favorite JP 91 L board become separated from the board filler.
I could be water leak plus beating on the chop at speed I suspect but now there is few centimeters gap on whole bottom surface, without any obvious external signs , whole bottom is simply separated
I wish to drill a hole, insert some glue and compress the bottom , stick that bottom to the internal board structure again.
What sort of glue could I use? I thought that polyurethane foam will be the easiest to fill up the space. (?) but if not react with that filler inside? will it last on the chop?
should I drill whole from bottom, side or batter upper surface thought the board?
Did somebody similar repair or board need discarding ?
I repaired a 79L JP something or other that had the bottom totally delaminated. I used lots of holes drilled into it that were about 3mm in diameter, which was the size of the syringes. By lots of holes, I mean at least a hundred, and more where the delam was worst.
I used 2-part foam in the syringes to glue it back together, and after injecting this 'glue' I would use a sandbag to hold it down while it set.
It was a lot of work, and after I glued it down I still had to remove the excess foam and then sand back and fill the holes.
I know it hasn't separated yet, but I also don't use that board as it is a very small board for me.
There is also a section where I injected more foam than needed and it raised the surface a bit.
All in all, I wouldn't bother doing it a second time, unless I really loved that board, and even then...
I had this with a board after it was left in the sun, depending on the size of the bubble it may be impossible to have it stuck down without creases appearing.
I would recommend trying to glue it (don't use epoxy) through multiple injection points, if that doesn't work then cut out all the de laminated sections and rebuild them. This is actually an easier job than it sounds once you have the materials...
Good luck!
1- Take a knife, and cut the whole bottom off, hopefully no EPS has come away with the laminate.. If there is foam attached to the laminate scrape it off..
2- Get some Q-cell and Epoxy and fill all the imperfections.. (if any, it's either the foam has failed, or the resin attaching to the foam)
3- Squeegee 170g of epoxy over the core and put the bottom laminate back on... Weigh it down or vac bag it..
4- Glass over the cut, it's a longitudinal cut along the edge of the rail so not structural.
5- Paint it..
6- take it to the tip, and buy another one..
I followed a similar process, mine felt a bit funny coming in at South passage one day and when I looked at the board on the beach I realised it had a huge bubble.
My "fix" was
1. keep in shed for 4 years while thinking "someone will want that one day"
2. clean out shed an take to tip.
problem solved.
Mine was a Starboard Trance, 84L I think.
No the photo is not my shed. If you look in the background you might spot the one designs in "windsurfer valley" at the Lancelin tip. And yes those other 2 boards also came out of my shed, one being the first polyester board I ever owned and the other my only custom built for me (Warren Thomson I think it was).
Must be an old pic, the Trance was not there the other day else I'd have grabbed it 
After closer examination I found possible reason for delamination
10 cm long rip on the side !!
Mystery remains how could it happen?
I wonder how much water and salt is now inside.
Board is now 9kg heavy with foot straps but no fin. What was the brand new weight?
It's more likely that crack was caused by the delaminated bottom flexing.
As to the delam, do you always undo the bung after use?
If you don't that's probably the main cause.
If you do, it's either down to extreme or constant flexing, (landing flat jumps from onhigh, or high speed into big chop).
Or faulty manufacture, some times the glass layer under the sandwich isn't wet out enough.
If it's due to foam fatigue due to crash landings or high speed in heavy chop, fixing the board will be a pain.
The styrene foam under the sandwich will be a mess, glueing the bottom on thru holes will end up with an uneven planing surface, board performance will be seriously compromised.
The only good way to fix this is rip the old bottom off replace the damaged foam and put on a new sandwich.
If it's a dry layup or heat/airplane cargo hold blow up cause, there's a chance that the underlying foam is ok, and sticking it back down will be possible.
Anything will delaminate eventually. Might be one season or 100 seasons.
Keef you are right about the main cause of early delamination, but decrepit is right that flexier construction obviously causes delam too. Things made of many layers glued together can't repeatedly flex without coming apart eventually. However of course if it has no flex it won't be too good for jumping.......
What type of glue should I use?
Could you recommend any product on out market that suit ?
I am ready to give a try bonding this week, nothing to loose.
I have been thinking about polyurethane foam that could be very easy applicated from spray can though long plastic pipe from one opening along whole board length.
From my experience foam is incredibly sticky, waterproof and will fill all places, but not sure how strong that bond will be long term.
Will it dissolve polystyrene inside?
no it will not dissolve the polystyrene, as you say this is a good solution (I think it is also what the boardlady recommends)
I agree that the lower carbon content (ie flexier) boards gave a smoother ride in harsh chop.
The ASA boards such as the f2 axxis, rides, mistral screamers and flows etc were significantly smoother than their custom epoxy counterparts.
(but sadly they eventually delaminated)
decrepit i had delam in mind when i made this board , it has 5 mini stringers and the divi has a thin layer of bogg top and bottom to fill the cells to try and stop any delam
