after a long pause, it's time to start building

[Bob Hammond]

Nice curves on that bow. I'd forgotten that PVC pipe can be reformed like that. I once made a model of a rib cage from PVC. One thing that I recall, is that PVC generates toxic fumes (e.g. dioxin and hydrochloric acid vapors) when overheated. I don't if the temperature necessary for deformation of the PVC can cause the release of the toxins. I suppose that if it is shaped outdoors and you stand upwind in a good breeze the hazard is minimal.

[GPW]

If it’s smokes ( gasses off) , it’s too hot ... not necessary for bending, not wanted for bow making ... Oddly enough PVC bends around the same temperature Foam bends ~190F ... Easy and not a problem ... ( you could put it in boiling water , same as you’d do with wood bending )
Ps. it makes a great bow ... much easier than cutting down trees and carving/tillering for days ...

[GPW]

Ps. The bow is an asymmetrical one based on the Hidatsa Indian bows ... It shoots quite flat with almost No handshock ... We made a form for the bending ... Easy enough to make a form for PVC Wagon ribs ...

[Bob Hammond]

Maybe I'll give it a go. It's like bending guitar sides. I use a 6"x36" 1000watt heating blanket that is controlled by a Harbor Freight router controller.

Sent from my SM-G920P using Tapatalk

[GPW]

Bob , Heating blanket ... Have you tried heat bending foam yet ??? ... 190F and when cools it stays in that shape ...

Very much like bending guitar sides ...

[Bob Hammond]

The problem with the heating blanket is that it's only 36" long. but if a guy had two of them...

here's where heating blankets can be found:

http://www.omega.com/search/esearch.asp ... ng+blanket

[GPW]

Thanks Bob , that’s a wonderful source for heaters ... Now if only we were doing production , a couple of those heat blankets and a big wooden form form would be just the ticket to maikng all manner of bent foam curved trailer parts ...

Anybody want to start a Teardrop trailer company in New Orleans ?? ... ( whenever it stops raining ... )

[GPW]

Just a drawing exploring ideas ... This may be perfecxt for one of those “Utility “ trailers , with the box already framed in steel ... and a ramp/patio ...

[Bob Hammond]

We're straying off topic, but for the bows, I would make a long shallow trough from a length of aluminum gutter and put it on the heating blanket, with a cooking thermometer. A word of caution: my heating blanket can char wood easily, so never, ever leave one unattended.

[GPW]

Bob , we’ve been using a cheap Harbor Freight heat gun and a v shaped piece of cardboard with aluminum foil wrapped over it ... Keeping the nozzle Constantly moving to avoid any scorching which ruins the PVC for bow use , making it Brittle .... It takes a few minutes to soften to the point it turns into a noodle , easily shaped , bent or smashed to shape ... Again , if I were producing these , I’d get a set up like you suggest ... The best thing is , thanks to you , we now have a source we can find heating blankets , just in case someone wants to do some real heat bending ... Foam heat bent parts can be a single layer that forever stays in that shape ... bent forms lending a lot of extra Strength to the Structure ...

[Bob Hammond]

I'm laminating the arches for the door frames from 1/4" x 1-1/2" cedar strips. I'm very happy to find that cedar is quite light and dimensionally stable, although I am selecting boards carefully and cutting around knots and other defects. Because it shows little tendency to warp, I'll probably frame up the doors with cedar as well.

[GPW]

Very Nice ...

[Bob Hammond]

Here's some pics & commentary about the doorframes. In the last post, I laminated the arched headers.

First, an overall view of the mockup.

Next I cut the jambs to length, cut a bird's mouth for the beveled threshold. Note that the bird's mouth keeps the jambs securely located on the threshold (which will be screwed to the deck). Note that the threshold is beveled to shed rainwater.

Then I cut bridle joints to marry the header arch to the jambs. Here, I had a brainfart - Although the bridle joint is ok structurally it might allow infiltration of rainwater & dew. I should have mortised the arch and then cut a tenon on the jamb to fit into the mortise. But it is done, and so to get avoid this potential problem, I'll epoxy the bridle joint so as to exclude water as much as possible. I haven't cut off the 'ears' yet, and I may not since somewhere I read that they may reinforce the foam and prevent breakout.

[Bob Hammond]

I decided to add some cedar framing (I wish I'd done it at the beginning), and for the top rail I found a 2 x4 that was conveniently bowed to shape and at 70% off. I ripped it down the middle to make matching sides.

The walls are pocket-screwed onto the deck with stainless steel screws, and there is a z-shaped drip edge between the walls and deck.

I also decided to make rafters from 1/2" x 2-1/4" cedar fence pickets. They're both cosmetic and functional, in that they'll hide the seams and also support the roof. I'm dovetailing them into the top rails for strength. By the way, the large 3-4-5 right triangle makes it far easier to square up and clamp the panels.

I think that next time (if ever), I might make it a Standy by placing a hurricane hinge on the front curvature to allow the rear 7 ft section to lift.

[Bob Hammond]

Here's a rafter fitted to the top rail. In my opinion, a proper wood joint with glue will hold up much better than a joint made with metal fasteners (stainless steel screws aren't cheap, too) because the cedar is soft and weather and vibration will 'work the joints' and loosen the metal fasteners. It was safer, easier, and faster to cut all of the joints by hand than dink around with power tools that need jigs and cords and other stuff.