First off let me say THANK YOU DAD, I LOVE THE CUSHIONS!!!!
He was stitching these up right after a knee surgury that didn't go so well (still hurting a month later), so I know that hurt to sit there and work on these, so thank you Tim Blumenstein, of Perfection Interiors 41+ years of experience in Auburn Washington, who can be reached at 253-833-4386. Tell him you saw his work on my blog. (I know, shame-less plug!) he also did another Aristocrat's interior too.
Let me explain these as we go... vinyl, or leather can blow out your seams if you sit down too fast and you have it all stitched up nice and tight... the air has no where to go so rapidly and will pop the seams like a balloon. So to remedy that problem we put a complimentary breathable fabric along the rear to create an expansion chamber to allow the foam to push and pull the air in and out without damaging the seams, even if you plop down too fast. This is also sometimes done with grometed holes... but I think this looks much better.
By stiching these together at the top seam, it does a few things:
1. keeps food and grime out of the cracks (remember, there is a 2 year old that camps with us) :)
2. creates a 5" x 5" air channel behind the seat and below the back when it's in sofa form.
3. Keeps the bed flat and together at night.
I copied my sofa in my living room for the design, boxed ends, single top stitched all edges and a single top stitch seam 6" back on all 3 seat cushions for looks.
Free Uphulstry Lesson: The Single top stitch is 6x stronger than the dual stitch you see on your expensive leather interior in your car, and 3x stronger than a simple hidden reverse stitch. The dual top stitch is all for show, and is actually a weak seam that is bound to fail and tear apart sooner than later. The single top stitch is done like this; you sew the two panels together, then flip both edges over to the one side and stitch it again going thru all 3 layers including the "top" that is shown. So not only do you run the first stitch, you double up thru all three layers for the second stitch, and in doing so you relieve the stress on the 1st stitch by running the 2nd. Now not only are you holding 3 layers together for a strong seam, the other panel's seam does not have the same pull tension it would if you didn't top stitch it it is now pulling strait on the panel and not on the 1st stitch.
Now, in your car, they do the same first hidden stitch, then individually flip each edge back and stitch it to the same panels to create the "dual" top stitch to make you feel it's really, really sewn together and strong. Wrong. Here in lies the problems;
1. the 2nd runs of stiches do NOTHING to strengthen the 1st seam, you actually make the seam weaker by punching unnessesary holes in your fabric/leather.
2. Now with all that fancy stiching done, you are still relying on a single, stressed to the max seam to hold the two panels together. They pull those flaps back nice and tight to give it a sturdy look, but they are pulling against the seam, not relieving any pressure like the "single" top stich did. So just for that fancy dual stiching that everyone from VW to Bentley, BMW to Rolls Royce, Toyota to Lexus (you get the point) use in their cars is actually a very, very weak seam. This seam will eventually tear out (look at any 200k+ mile leather car interior.) :)
Okay, off the soapbox and now onto the sofa, here is the break down from sofa to bed.
Sofa: (needs thicker, better foam and poly wrap... kinda loose right now)
Fold the back forward (attached)
Pull the bed out (mine pulls out from under the other one so the cushion doesn't move at this point yet)
Slide the cushion forward
Fold the back flat
and that's it!