I'm making a modified GVP Gear Ultralight Pack and am having a difficult time sewing the foam. I'm using a size 16 denim needle. The foam is 1/2 in thick. The bottom stitches are bunching and gathering a bunch of thread. The top stitches look normal. I assume its a tension issue due to the thickness of the foam and the fact that the sewing machine is fine when sewing other fabrics. What should I do to the tension? Or is it something else?
Thanks- April

Edited by lirpa939 on 08/26/2009 16:22:09 MDT.

Hi,

If it was my sewing machine I would set the tension to the highest number and try it.

What would that mean for the bottom tension, the screw on the bobbin? -April

Another alternative would be to cut the foam so that you do not have to sew through the fabric and foam. I have made a few packs based on the G4 plans. I cut the foam the size it needs to be, and sew the fabric as close to the edge as I can. Using a zipper foot will get pretty close. The sewn fabric will surround the foam and hold it in place for shoulder straps and hip belts without a need for sewing through the foam. In fact, the foam can't be sewn through or it is no longer removeable. Keep it simple. Scott

"What would that mean for the bottom tension, the screw on the bobbin? -April"

I don't think you need to do anything with the bottom tension if thread is bunching up as you say. It sounds like you need to turn up the top tension so the bottom thread gets pulled into the foam.

Hi April

I am not 100% sure what you are describing, but let's assume you mean the bottom surface is showing loops of the top thread sticking through?

If this is the case the problem is that the foam is being a bit 'sticky' and not letting the needle pull the top thread back when it retracts. Fabric is far more slippery. There are two ways of dealing with this:
* Seriously increase the top tension just while sewing foam
* Cut the foam to shape so you don't have to sew through it.

It may also be that the sewing machine you are using simply cannot handle the foam and give the required tension. If it is a 'light' sewing machine this can happen.

Cheers