hem for boom tent

[casem]

This is going to be difficult to explain but I'm going to try it anyway.

I'm making a boom tent, and I want it to extend past the mast, so I basically need a hole for the mast and a slot leading up to that. The problem is, how do you make the hem? You can't take the material "internal to the cut-out" and fold it back because it bunches (I suppose I could force it). I can't possibly be the first person to run into this problem. Is there a trick to do this?

[LLaver]

Rather than hemming it you could stitch some bias binding around the edge.

Bias binding is just a strip of fabric cut at 45 degrees to the grain of the fabric, this allows it to deform and bend around curves.

Cut a strip that is four times the width of the final edging, then fold it in half along its length and then fold the edges in to centre to create a strip that is four layers thick. place over the edge and sew straight through all layers.

http://www.imagestation.com/picture/sraid198/p6497e59649269e469b5f0ab0c6e95a67/f0dce62d.jpg

cheers

Lee

[Todd Bradshaw]

Your local tent and awning company probably has a roll of pre-made Sunbrella bias binding and they would likely sell you a few feet pretty cheap if that's the way you decide to go. I generally like a pretty tight seal around the mast on boom tents and mast-up-boat-covers, so I build them like this. They're a bit tedious to make, but work quite well. You can also make little ones to fit around shrouds, headstays, etc. When I built the mast-up cover for my Starboat it had a big tube for the mast, two for the shrouds, two for the backstays and one for the headstay, all made this way.
http://www.imagestation.com/picture/sraid198/pcbbb0563b2451170f8776b1cefe08096/f0dcad83.jpg

Split the cover from a close edge (side, front or whatever works best) to the mast and then cut a hole a little bigger than the mast. Hem the edges of the split by folding the fabric under and sewing a 3/8"- 1/2" hem. Then sew a long strip of fabric about 3"-4" wide (with hemmed edges) to the hole as a "stand-up" collar. You may need to make a few small slits in the seam excess around the hole after sewing the straight collar piece on. If so, keep them small, as far from the stitch line as possible and hot-cut them. A stapler is the best way to baste pieces of cover fabric together before sewing. Sew a #10 Delrin tooth zipper along the finished edges of the split and up the collar. The zipper slider should start at the bottom and be at the collar end when zipped up. I use a velcro-closed flap over the zipper. This helps keep wind from blowing water and dirt into the zipper. Also, zipper tape doesn't last very well out in the sun and weather, so the flap will greatly extend it's life. In the drawing above, you're looking at the underside of the folded-back flap. Velcro is plenty strong enough to keep a flap closed, but not strong enough to replace the zipper - so don't even think about it. To close the cover up, you zip the zipper, wrap the long end of the collar strip around the mast and collar a couple of times and tie it off with the string.
http://www.imagestation.com/picture/sraid198/p4df5cc1b92b35d5b7142d2a2871edaa1/f0dcad6f.jpg

It's a fair amount of work to make one of these, but it's not particularly difficult. The finished closure is professional looking, secure and does a good job of keeping out weather, bugs, etc.

[casem]

This sounds good. I'm going to try to go by the new SailRite in Annapolis next time I am up that way so they should probably have the binding etc. Thanks.

[Richard Smith]

Todd's collar is the usual and will provide a way to hold the tent at the mast.

You may also consider using sailmakers leather (silver/grey) as the binding instead of bias fabric - if you just want to bind the edge. Kinda looks "shippy."

BTW: Pick up some seam tape. It will help hold the pieces of whatever you choose together for you as you sew and avoid a lot of $%&*!'ing. Just keep it back from the edge so it does not show.

[peter osberg]

There is a product called 'polytac' which is genuine aircraft (stits aircraft product line) glue that is a great fabric glue. I works really well securing backing on seams and edges and stays flexible and waterproof. When I used it it did a better job than the coommercial dodger and cover I had made for me that solely relied on stitching. It dries..right now.... Which is the only fussy part about using it (it is also MEK based so it is not suitable for nylon).
peter

[Todd Bradshaw]

I used adhesives and/or seam tape on Sunbrella covers and multihull trampolines for a brief period back when I was doing a lot of commercial canvas work, but didn't find them to be of much real help. Some eventually worked their way through the fabric, leaving stains, others left stiff spots that stayed that way after the fabric's sizing started to wear off and it got soft. I went back to hot-cut edges and a good straight stitch. If a cover is going to a place where it tends to be sunny almost all the time, I'll use Tenara thread (teflon/Gore-tex) rather than the standard Dacron. That way, the stitch lines will last longer than the base fabric will. If it's sewn with Dacron thread, you can generally figure that the fabric will last about twice as long as the stitching, so somewhere down the road, you may need to go over any exposed stitch lines with fresh thread.

I much prefer staples for basting as they are quick to put in, hold well while wrestling the cover through the sewing machine and are quick to remove after sewing. Adding glue, as long as it doesn't stain and stays flexible would be fine if you want to fuss with it, but even if the piece is glued together, the true intergrity of the cover is usually going to be that of it's stitching.