The plans call for foam flotation under each thwart as well as filling the area under the stern seat. The wood core obviously has positive buoyancy, but the fiberglass coatings offset that. You should add flotation equal to or greater than that called for in the plans.

Thank you.

Any idea where I can get the foam? I have looked on CLC's website and can't locate.

At present, I have rubber fenders (about 20 x 6 inches) affixed below each of the three thwarts.  I don't have anything in the stern yet. I do have an old kayak that has lost her true. There's a piece of polysterene in the kayak I may put in the stern.

In all of our demo models we use the pink or blue polystyrene foam you can find at Home Depot or Lowes. 

We epoxy the blocks of foam together, shape them to fit, and spray-paint them black with Rustoleum or whatever:

We'd include the foam in the kits, except that it would add $100 in shipping because of the bulk. At the home center, the foam is only a couple of bucks a sheet.

Extruded Polystyrene or XPS can be picked up at any home center. It is water resistant and I can ony image that adding a coating or two of paint helps some. It's also great that it can be shaped easily (by sandpaper, rasp, etc) and it takes to epoxy and glass well. I made a foiled rudder for a Com-Pac 16 a few years ago using it and that thing got sailed hard and I never had a problem with it.

http://kpeting.blogspot.com/2015/12/re-naca-0014-rudder-modification.html 

   Thank you both! Much appreciated.

We followed the manual for the under-thwart flotation described above. It's true that it is soft and can be shaped. We don't have a band saw or an air extraction system, so it was very messy. Our least favourite part of the build. We didn't glass the foam, just painted then epoxed. In a couple of summers two of the blocks have been kicked off the thwarts, and the others are looking pretty rough. The insulating material is very fragile. This weekend we're going to pick up a 4x8 of okume and try facing them.

   Would putting fiberglass on them make them more durable.

Thanks, Larry

Larry, I believe it would, though have not tried. If I were to do the whole thing over, I think I'd just box the thwarts in like the aft seat. I guess a design requirement is that the thwarts be removable, but I don't think I'll ever do that.

That 4x8 of okume is waiting in my garage. The original plan was to face the insulating material, but now I'm wondering if I should just box it all in. Might be more work as I'd have to sand off the varnish for the filets, but might be more robust long term.

On the other other hand. I wonder how helpful they actually are when swamped in rough water. Haven't tried it myself, touch wood, but I'd guess they upgrade the ease of self-rescue from "impossible" to "almost impossible". Still, every little helps.

   I hated the foam float building as well. Agree, least favorite part of the build. Couple problems for me was Lowes only had expanded polystyrene (disposable coffe cup material) not the extruded polystyrene that's shown above. 

Cut them (foam went EVERYWHERE--like a fake snowstorm), epoxied, painted and left out to dry. Las Vegas heat melted and warped them in half a day.

Will probably retry with the correct foam once I find it, but for now I'm going to launch without and rely on positive bouyancy and steady rowing on calm water (I know, I'll post pictures of the bail out after the desert squall).

I have also considered adding float bags attached to the underside of the seat in the bow and stern instead. Will look terrible, but I'm over aesthetics.

Any suggestions or recommendations welcome.

Joe

Something like this:

https://www.rei.com/product/898428/nrs-standard-kayak-flotation-stern-bag-single?CAWELAID=120217890002303443&CAGPSPN=pla&CAAGID=107744421264&CATCI=pla-341865038764&cm_mmc=PLA_Google&product_id=8984280001&ad_type=pla&channel=online&partition_id=341865038764&target_id=pla-341865038764&brand_flag=&adgroup_id=107744421264&campaign_id=10020760234&location_physical=9030799&cid=434262083718&network=g&network_type=search&device_type=c&merchant_id=1209243&gclid=Cj0KCQjw_ez2BRCyARIsAJfg-ks9JhxyyjPtHuxO9pEIZo5nfOBPrxltGo3uoCOKrltwC-6Ua0xG-tcaAnQaEALw_wcB&gclsrc=aw.ds

Also, to the OP, not sure if this was mentioned above, but the stern seat should contain polystyrene foam if it was built to spec.