Upholstery and Cutting Foam?

[nigelmercier]

[Topic is regarding home sofa, but could apply to boat upholstery]

My lounge sofa has a backrest with a synthetic "kapok" filler (polyester?), no foam. I decided to replace it with a combination of medium firmness foam, a layer of the kapok, then polyester batting. The result looks great, but the cushions are too firm. My options are:

Repeat with softer foam (expensive, may sag again)
No foam but add more kapok (expensive, will probably sag again)
Slice the existing foam to half thickness, then add back some of the existing kapok (minimal cost: just more batting and adhesive)

I cut the foam using an electric carving knife, but it won't reach across the width of the foam, even if I cut it in half horizontally first.

Any suggestions for slicing the foam in this way? Perhaps some kind of hand saw in a jig?

 

[Phoenix of Hamble]

Thin wire (seizing wire is perfect) and a big 12v battery through a rheostat to control it.. a bit of work to set it up, but it cuts through the foam like butter!

We made up a wooden 'frame' with eyelets set in at either end to avoid the wood burning.... and got through 3 or 4 lengths of wire as it eventually broke due to not quite getting the current right.

 

[nigelmercier]

I've actually got some Nichrome wire, which is normally used in polystyrene cutters. Problem it that it sags.

 

[VicS]

I've actually got some Nichrome wire, which is normally used in polystyrene cutters. Problem it that it sags.

Danger of toxic fumes cutting upholstery foam with a hot wire ! 's what kills people in fires

(Ok for polystyrene/ styrofoam)

 

[Deleted member 36384]

The upholsterers who fitted new cushions to my yacht reduced the thickness with their special knife aka electric carving knife. After marking the required all round the edge with a marker pen, they just set too shaving bits off until the foam had been reduced. Their machine made it look easy.

 

[Phoenix of Hamble]

Danger of toxic fumes cutting upholstery foam with a hot wire ! 's what kills people in fires

(Ok for polystyrene/ styrofoam)

I did mine in the garden!

 

[duncan99210]

I reduced the thickness of a piece of foam using a normal thin bladed carving knife in the same manner as described by old boots. Marker pen to show correct thickness, then second person holding foam apart as the cut progresses. Needs to be a sharp knife to work well and the second person is essential as otherwise the blade tends to bind in the foam.

Have you tried using upholstery wadding? It's lightweight fluffy stuff: looks a bit like sheets of candy floss. We used it when redoing the saloon upholstery to get a nice curved finish to the seat tops and to take up any slack in the covers. Costs buttons but you do need quite a lot of it. Comes in a variety of thicknesses, go for one thickness bigger than you think you'll need......

Finally, have you thought about buttons to secure the whole thing in place? Run a loop of thread (think whipping twine strength) front to back, plain button to the rear, fabric covered button to the front. No idea if it'd suit your needs but it might be applicable.

 

[nigelmercier]

Have you tried using upholstery wadding? ...

Yes, it's called batting