Cloth cabin bows

[JeffM]

I'm working on the cloth spray dodger and will soon start on the rest of the roof. Hand-sewing by a sloppy novice--what a job! I made the bow for the dodger out of a piece of copper pipe, since I needed to bend it to conform 3-D to the deck and wrap around the forward edge of the coaming to keep it out of the way when not in use. I'd like to make the remaining roof bows of pvc pipe, and need to know how to form them and how to apply heat to bend them. Who has done this, and how did you manage it?

Jeff

[EdJones]

I bought fiberglass bows at West Marine, a bit pricey but worth it.

[Phil]

Jeff I think this is similar to what your asking about? Over at B&B

http://www.messing-about.com/forum/viewtopic.php?p=28286

I looked up some PVC characteristics (250 deg. f. for bending so SWMBO's hairdryer is not going to cut it! You need a heat gun to do it right. No fire or it will scorch and melt!) as Graham says do the heating slow and evenly.

Good luck,

Phil

[JeffM]

Thanks, Phil. I'd studied Graham's design, but forgot he'd mentioned how he made his bows.

[Barry Pyeatt]

1/2" CPVC pipe will take a pretty good bend without kinking or collapsing and is strong enough to hold up a pretty good width of fabric. I've used it in a number of different canopy situations and had good success with it. As far as a more permanent structure I would stick with alum. conduit and a pipe bender. There are a lot of commercial fittings and it is more easily formed and will support a significant amount of weight.

You may not find any plastic pipe easy to form into a permanent bow. When you heat it the structure is deformed and weakened.

The fiberglass tent rods work well for slipping into pockets that are formed into the fabric and will hold a substantial amount of weight and strain. These are available online from a variety of sources at reasonable prices as are the fittings to use them.

[Phil]

Barry, I agree, for a permanent solution alum. conduit and a pipe bender.

You may not find any plastic pipe easy to form into a permanent bow. When you heat it the structure is deformed and weakened.

The trick to heating plastic (or metal) is to get it to the min. heat required for it to loose it's memory (ie. when you let go it doesn't go back to being straight) and not so hot as for it to loose it's initial strength, for PVC it's ideal temp. is 250df with it's welding temp. at 500df. If you exceed the ideal temps. for any prolonged time the part will lose it's strength.

I noticed you said you used CPVC. I repaired a few plumbing lines in the house this past weekend. I cut into old CPVC with the shears only one rachet and it blew apart really ragged. The old white PVC cut like butter. I think it has plastic added to it ("plasticized"). The new CPVC however cut like butter as well?? So I guess exposure to hot water (which it's designed for) makes it brittle?? I ??? the CPVC for a structure but........there are also UV issues??

[Terry Dunn]

This method probably won't work for the bows you want but I thought I would mention it.

When my boys were in Boy Scouts we made snow shoes with PVC frames. Some one had built a jig to put the hot PVC on. We heated sand to about 350 F in pots and poured the sand into the PVC. You have to have steel or cast iron pots and a big burner to get it done. We managed to burn a hole in one pot. Put the PVC in the jig and pour the sand out. Cools hardens and holds form.

[Bud_Wilson]

Think about it. you buy a heating blankit kill a cast iron pot buy a good heating gun. You still have to buy the pvc and fittings. I think Ed got the cheapest ones from west marina and they are fiberglass, have to be better quality. I would at least check the price. Y'all Come Cap'N Bud.

[JeffM]

Thanks, all! (I've been keeping quiet and letting you all hash it out.) Cap'n Bud, I am thinking about it, but I'm leaning toward aluminum because its strong and easily shaped. I already have sectional fiberglass tent poles -- used them on the first overnight trip -- but I want my real roof to have a particular shape. The local box store has only steel and plastic conduit, so I haven't found aluminum yet. I'm going to want to be able to store the bows in a long seat locker, so I'm also planning to be able to take them apart into more-or-less straight sections.