EPS Foam for Stringers

[JBASS02]

Has anyone used 2lbs EPS Foam for their stringers? I saw Raka is now carrying various thicknesses. I'm planning to raise my stringers 2" and thought it might be easier using shims and foam board rather than forms and pour foam. What are your thoughts. The foam in my current stringers is dry so I'm not replacing it and I'm using epoxy. http://www.raka.com/eps.html

[smilinmatt]

That might be a little light for stringer caps. A quick internet search shows about 25 psi for compressive strength on 2# eps. I'd be worried about it crushing over time wherever there's weight (people, console, etc.) on it while you're running through waves. It might be worth a call to Raka to see if they can get a denser foam board in for you.

I'm currently doing the same thing. I picked up a 2" sheet of T-60 Aircell (6# vinylester foam) from PolyuMac. It's compressive strength is 173 psi.

[dirtwheelsfl]

Yea its basically just a nice tight styrofoam, need more glass on it than a “structural foam” would. Something like 4 layers of 17oz should be fine.

[JBASS02]

Thanks, I'll give it a try.

[smilinmatt]

If you haven't ordered it yet, I'd seriously consider something else. Putting glass on top and/or below it isn't going to help with the compression strength - which is what you need in this application. The glass will help distribute the load some, but I think there's still a pretty good chance that you'll end up with a "springy" deck in a few years.

[dirtwheelsfl]

You can use charmin if you put enough glass on it... Do some hammer testing on some pieces of different layups til you feel its adequate. A strip of uni on top never hurt either...

[JBASS02]

Thanks for the advise. I drilled some more test holes in the stringers and found some water... figure may as well do it right while I'm at this point. I'll be removing all old foam and adding 2lbs pour foam. I've never used pour foam, how important is it to get the boat level before pouring? From the looks of it puffs up over the forms and is then cut it back down to size so having the boat level isn't important??

[lelandtampa]

I checked on Hull truth and Charmin is no good. Gotta get some purple Cottonelle and vac bag it with vinylester. That's how they do yellowfins.

[smilinmatt]

I think Dirtwheelsfl and I might be arguing two different points. Based on what you said, I think you're planning on only "capping" the stringer. On the crude pdf I made (black is stringer, blue is foam, and red is new fiberglass), if you are doing "1", no amount of fiberglass will improve the crush resistance of the foam. If you are doing "2", you can use whatever you want with enough fiberglass (including charmin, cottonelle or wonderbread).

[smilinmatt]

As far as pouring foam, it's easiest if you can adjust the angle of the boat while you're doing it. It will pour out with about the consistency of syrup before it starts to expand. I use separate two mixing cups so you only need two for the entire process, a cheap plastic pitcher to mix in and pour (cheaper the better, more flexible the easier to clean and reuse), a spatula to help distribute the foam and clean the pitcher and a drill with a mixer.

Some tips:

-start the pours on wide areas so you learn how much expansion there will be
-after about 30 minutes, you can pour over a prior pour
-don't foam yourself into corners. It will keep expanding and can cause ruptures. Try to leave large openings on prior pours when you're getting close to a corner.
-you can't have too many or too big of relief holes when pouring foam

I just finished foaming my 23 last week, and it took about 6 gallons mixed to fill the stringers. I mixed one quart (16 oz A + B) at a time and did 3 pours on each side, then waited about 30 minutes, cleaned my pitchers, mixer and spatula and started again. Once I got near the end, I started mixing smaller batches to limit pour over.