hand lay up of coracell m foam

so moving along thinking about constuction,i will be doing it S&G so i plan on glassing the inside of the floor then stiching together the 1/4" meranti sides.i think there will be enough give to put a little bend in the floor.maybe around 6" of rocker on each end the length will be 11' or so with a 3' flat spot in the middle.so my question,what do i do with the raw surface that doesn't have glass?it will be sliding around as i stich.should be ok,maybe a light sand and vacuum off when done.or is there a better way to clean?

 

I'm not 100% sure I follow. You are building a square-ended pram? 3/4" or 1" Plascore bottom with 1/4" (or mm equivalent) Meranti Hydrotek sides?

Scarf two sheets of plywood together to make a 4x16 panel. Cut out the side pieces. The left over plywood will be useful when making lockers, etc.

Box joint the Plascore together to make a panel long enough to make the bottom.
At this point you could (probably) fiberglass both sides of the plywood, and still have enough flexibility to bend it onto the boat. Then I would pre-fiberglass the outside surface of the bottom panel. Make your transom-like end pieces. Glass both surfaces.

Now stitch it all together. You will probably need some trapezoid-shaped (temporary rib-like formers) to hold the shape, while you stitch it all together. Now glass the inside bottom. Add gunwales and a few seats. And call it a boat. That's how I'd do it.

 

pram ,driftboat,skiff whatever you want to call it.A pointless boat would work.

on my test pieces it was much easier to bend with the glass on the inside of the curve.this makes it much easier anyway.

outside will be glassed all as one so over the chines,sides.

but my question is about the foam.
maybe i'm overthinking it but was just wondering on a good way to keep the foam clean or a way to clean when i'm ready to glass the whole outside.

one thing i forgot to test was how well the wires(stiches) will hold with only one side glassed.i no it was pretty strong or stronger then the wire anyway when both sides were done.i guess i'll find out.

 

Foam inside !!Glass out side !!

Its better to have the foam inside and glass out !! Didnt say what glass you had or the thickness and or density of the foam ?? but if the sheet gets hit or the bend is to great the foam will break and the release could part a big piece and you could even loose the lot!! can re-resin stick it but the tension will have changed and so the curve will change with it !!

Foam inside glass outside !!. if its to hard to bend then use a lighter glass !! and or a slightly thinner core .

 

I think I'd use a mold/form if I were bending foam without heat. Unless you are cutting out bits to score the foam, there will be great risk of it snapping on bend up, like tunnels is saying.

 

I keep repeating the same things over manytimes Know the materials you are working with what you can do and cannot do what you should do and should not do ! understanding the limitations of how far you can go before things break . if thick foam breaks try 2 or3 layers of a thinner foam and laminate it like you would if you were using veneers of wood or thin ply wood . Its what were were given a brain for to think and evaluate and reason . its what separats us from our wives !! oops !!

 

here's a pic of the model,



not all that much of a curve,

maybe i could build a form to hold the floor this way then glass.the raw foam should easly bend to this shape.