Upholstering a Tapered Seat

[cheshire~rose]

We need to try and make a cushion for a bench seat in Python's cabin. 

It is not anything grand, just a bench base (with storage underneath). The cushion to go on the top of the base will be easy (although I think it might be 3 cushions to allow easier access to the lift up hatches underneath. It is a very small space to be faffing around with large cushions in)

The bench runs down the side of the boat so we need a cushion that will squish under the gunwale for the back and in turn should help hold the base cushions in place.

The problem comes that towards one end of the seat is where the hull starts to taper in towards the rear. The base cushion should not be too much problem as a gentle curve along the back edge will reduce the depth by around 1½" (although the curve only starts around half was along).  The gunwales are very deep and slope slightly downwards towards the outside but the real problem is how to taper the thickness of the back cushion? The gunwale depth stays the same at the top but it is 1½" shallower at the bottom.

Is there any method folks have employed to get foam cut to match a curve and how do you even start to make a template of what is needed? 

Any suggestions are very welcome, we have a volunteer who is happy to cover the foam for us but we need to work out how to make the foam fit. 

[BEngo]

Make  a template of the bottom of the back cushion. 

Make another for the top.

At about one foot intervals make templates for the cross section of the back cushion.

Number the templates for the cross sections and mark their positions on the top and bottom templates.

Stick them all together so you have a sort of cardboard ladder.  Take that to your foam supplier.  It will collapse to long and flat so it might be postable.

The supplier will make the final piece by gluing up several smaller bits I expect.

Alternativel divide the back into smaller pieces, like the seat and don't worry about the curve. Each piece will then be  a rectangular wedge and the gaps in the joins will take up the

horizontal curve.  Much easier to cover but uses more material.

N

PS. Don"t make the finished back vertical or it will be  a bloody uncomfortable seat!

Edited November 20, 2017 by BEngo
PS