been doing some experiments with xps since it’s plentiful right now in my area (huge development going up with lots of scraps around the corner from my house). So far I’ve been hotwiring 2" wide rocker slices and gluing them individually with gorilla glue. This definitely works but it’s time consuming. Has anyone found a good glue that could be used to combine multiple 2" thick sheets to make a block of xps that could be hot wired? I know I can Hotwire through gorilla glue but I didn’t know if there was some else that was better (and cheaper).
I’ve added pictures of my latest xps creation: A 5’10"x19 3/4" quad. Continuous rocker and the rear fins set a little further up than normal. Glassed with 6/6+6. Turns really well and feels very close to regular pu/pe.
If you glue up flat sheets to make a thicker piece, you will end up with scarf lines where the rocker goes past the glued up sheets. I always have problems getting that part smoothed out. Cutting rocker slices avoids that problem. I add a perimeter piece to have a nice smooth rail. This is a mix of EPS and XPS.
I did a handful of XPS boards using rocker slices, but 2 have delamed from heat. I use the XPS for rails and stringer sections now, and EPS for the rest.
Thanks sharkcounty, I’ve always admired what you’ve done to create your blanks.
What I was referring to was gluing flat sheets together and then cutting rocker slices from a thicker slab. So instead of hotwiring 10 individual 2" slices I could Hotwire maybe just 2 10" slices. If that makes sense. Just wondering what glue would Be best to do this
I know some use spray can glue specifics for tacking fiber in infused process. 3m 78 work for foam if i remember well. Others too, if not eat foam. Probably not a strong gluing like with PU foam.
You may want to try Roo Glue. That’s the stuff Greg Loehr always suggested for gluing in stringers. I know some guys have also used it the way you are thinking, only they were using EPS. Obviously, test it first.
I have used 3M 78 to glue horizontal sheets of XPS together. It sanded fine – but I shaped within a few hours of bonding the XPS sheets together. The bond is very good after 24-48 hours of curing. But when it is cured, the adhesive becomes hard – at that stage it may not hotwire or sand well.
FYI 3M 78 contains some nasty VOCs that you don’t want to touch or breath. Work outside (very well ventilated) with nitrile/latex gloves and a respirator that has VOC cartridges.
I’ve tried using various spray glues, many made just for foam. I haven’t found one that is as strong as the foaming PU glue. Don’t want to foam to move once you start shaping, and I’ve had pieces come apart.
I think you may have a good plan in gluing up the foam then making slices. I’ve bought foam in various thicknesses and it was nice to have less pieces to glue back. The XPS I have is 3 inches thick. I was also able to get 4" thick XPS once, but it was used.
I played with test bonding of XPS scraps using 3M 78. The test pieces could be pulled apart for several hours after first bonding. After 24-48 hr, I could not break the bond. So, if you’re trying to glue rocker into bent pieces of XPS, you would have to test the bond after leaving the bonded pieces in your rocker jig for 48 hours of adhesive curing.
But as I mentioned, the 3M 78 adhesive becomes hard/rigid after 48 hr – and difficult to sand.
