Test board almost done. Now... questions!

General Discussion
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Hey folks!

Now that my first “test board” is almost completed, I have a couple of questions before getting to the real one. I’ll start with a quick overview of what I’ve done. Aside from the questions, if you can comment/laugh/bash on any of the things I did, you are more than welcome to do so.

Having no access to reasonably priced EPS blanks here, I decided to do my own blank by cutting profiles in an XPS sheet and glue them side-to-side to make the blank. Thought it would be easier to have the exact rocker right off the bat instead of using trial and error with foam bending. Oh, and by the way, this board is only… 2 feet long (this was more a test than anything else). And the real board also will not have a pointy nose so the glassing will be easier. For this one, I just shaped something for the looks. Anyway, after shaping, the result was this:

foamblank 

The darker patches are an epoxy filler I used to fill the marks I made on the blank when trying to flatten the stringer. After glassing the bottom with pigmented epoxy, I had the following result:

flaws_bottom 

I was kind of disappointed that the stringer and glue lines would show this much after the first lam (4oz). The wood I used for the stringer (some kind of plywood with a very spongy core) sucked up a lot of epoxy, explaining part of the transparency. However, even after the second lam it would still show through.

To avoid this on the top of the board, I bought some white Krylon H2O to mask the remaining part of the blank. My three layers of paint weren’t sufficient since there are some patches and the stringer that still show through:

flaws_deck 

(The strand on the tail was just glass I used to hold a fold on the tail that would not stay put. It was removed before final curing and sanded later.)

Plus, the rails are not the same yellow as the top since the blank was not masked with white paint on the rails. At this point, I thought that after the second pigmented lam and pigmented hotcoat, this thing would be totally opaque… NOT!

fisheye 

The stringer still shows through the bottom (and that damn fisheye is a real shame… really don’t know how this happened. Everything was thoroughly washed and dried before applying the hotcoat… anyway).

On the top, the results were a bit better: The second lam was thicker (6oz) and the white paint on blank seem to have helped a lot, but it’s still not perfect:

hotcoat 

Ok, the resolution on this picture is not good enough to show the flaws, but when held in hands, some defects in the blanks still show through. (By the way, the cutlap and the carbon fiber piece will be pinlined before the gloss coat. And on that picture, the carbon fiber patch hasn’t received its hotcoat… the weave won’t show on the final result.)

After these somewhat deceiving results, I looked closely at some other boards pictured here on Swaylocks and I’ve noticed that most pigmented boards are not 100% opaque (some stringers can be seen). This might not be a problem when using a “one piece” white EPS blank, but with my blue XPS with a glue line at each 1.5” (and potential patches to cover my fuckups), partial opacity is not an option to me. So, is there any way to make a blank perfectly “white/light grey” without 100 coats of paint? Or is there a way to make a 100% opaque lam?

I did some tests with red pigment and with a single 4oz layer, the black mark on the foam scrap was barely noticeable. I am however reluctant to use dark pigments because I have read here that they are prone to delamination (especially with XPS I would guess).

Thanks for your input,

 

 

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If it were me I’d try to work to the material I’ve got.  Blue foam would not yield as readily to yellow pigments and coverups as white foam would.    A blank with 6 or 7 glue lines isn’t going to resemble a blank with no glue lines as easily as will a blank that actually has no glue lines.  

Other people here have done XPS blanks with glue lines like your’s without using a stringer at all.  The glue lines add some rigidity.  Add some additional exterior glassing with wider laps and you’re in.  That should probably cut down on your stringer-related drama.  Beyond that, if you don’t mangle the foam while shaping it you won’t have to use any filler.  As I’m sure you’ve seen, the filler won’t take the pigmented resin quite the same way that the foam does.  

What I’ve done a couple times with EPS is to glass the blank with a single layer of really light cloth  - in clear - to seal it and then come back with a second lamination in pigmented resin to get my color.  Because the pigment layer is adhering to another lamination layer that is itself of even surface consistency I don’t get the “pooling” of pigmented resin in the low spots in the foam, which in EPS would be between the beads and in all blanks would include any nicks or scrapes in the foam.  Since you’re using XPS and epoxy you’re not really adding much additional weight because you’d already use a little more cloth in your laminations.  The other advantage of using a 2-stage lamination is that you greatly reduce the chances of pinholes.    Whatever drainage from the cloth into the blank that’s going to occur happens in the initial lam - the second lam has no such drainage.  

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I’ve found that swirls of color work really well compared to solids for covering up the blank, but if you use enough color it should be opaque. I’ve done white, yellow and dark green, but on EPS and regular Poly.

I just did an experimental Blue Dow XPS board this weekend. I used a 3 inch thick slab of foam and hacked out the rocker with my planer, surform and sanding blocks. The board has no stringer and is a single piece of foam. I wanted to cover the foam because I left it pretty rough, but I also wanted to use a logo so I added a tiny amount of white pigment and it worked OK. There’s a couple of photos in the what are you working on thread. I’ll post more photos when I’m done.

I had a lot of problems getting the lam wrap to stick to the bottom. I used 2 layers of 6 oz with a generous wrap and I’m not sure if I didn’t use enough resin or it was too much of an angle on the rail. The nose and tail have very hard edges, and the blue dow foam reacts differently than EPS or Poly. I also had spots where the XPS may be outgassing, so it creates little bubbles, and you have to work them out. I’m in Hawaii and we had a medium cold humid day for June. I ended up taping some places that didn’t want to stay down, but I still had to cut off sections of wrap that didn’t stick down. The top lam worked out much better, but you can see where the wrap was really messed up.

I was told by a glasser here about some of the issues with XPS and that’s not easy to glass. Kind of a bummer because I have 2 more blue dow XPS boards to finish and another white XPS blank.

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Enough pigment wiLl make it opaque. But to much pigment and your resin will not cure. Keep that in mind