pre bending cap strips

Moderator: flying2nc

pre bending cap strips

Postby flying2nc » Mon May 20, 2013 5:34 am

To pre bend my 1/4"x5/8" spruce cap strips I wanted to steam them to make them bend easier and hold the bend after they had dried for about 48 hours, I wanted a large 2"copper pipe or 2"galvanized pipe and went to my local DIY home center but the largest copper pipe they had was 1" and the same with galvanized,, They did have 2" in black iron but I thought that would be too messy, talking to one of the staff in the plumbing dept, he said the black plastic would handle as much heat as the cvpc pipe (180 F) and since the largest cvpc pipe they had in stock was also 1" I went with the black 2" schedule 40,, the only caps they had to fit it was pvc so that's what I had to go with,,also purchased a 3/8"x1/4" threaded brass hose nipple to install in the pvc cap to transfer the steam in. I wanted to buy some sort of metal hose/pipe to transfer the steam from the pressure cooker to the pipe/cap strip steamer but they really didn't have anything I liked. At home All I could find was a old sprayer hose that I had replaced from the sink, it was the right size and it was braided but I still wondered if it would hold up to the steam. I drilled a 1/16" steam escape hole in one 2" pvc cap and drilled & tapped the other cap for the 1/4" nipple,, the pipe I purchased was 6' so I cut it down to just over 49" then pushed the caps on (( NO GLUE )) and attached the hose with a hose clamp.
The hose fit the top of the pressure cooker tight enough that all I had to do was push it on the pressure cooker,
The first 2 cap strips I steamed I didn't have the nails in the pipe to hold the cap strips up out of the water that condenses in the steamer so they came out soaked! also I only left them in for 10 minutes after the steam was blowing hard out the opposite end which I didn't think was quite long enough when I went to wrap them around the pre bender so I put them back in for 10 more minutes. The black pipe gets hot as does the hose connected to the pot but not so hot that they droop. Before I steamed the next 2 I installed the nails to keep the cap strips up out of the water.
I left them steaming for 20 minutes after the steam was blowing hard out the escape hole. At 20 minutes I turned the stove off and waited till the steam quite blowing, I grabbed potholders and opened the pipe up,,,,as soon as you bring them out of the pipe they dry on the outside from the heat, then just wrap & clamp onto the pre bender. like I said I left them dry for 48 hrs near heat/air supply but I probably didn't have to leave them sit that long. if I had it to do over I would have put a smaller escape hole and maybe put it on the bottom of the pipe instead of in the middle of the end cap so when the steam was escaping it was also blowing/draining the water out?
little hole drilled in pvc end cap of home made steamer to let steam escape.jpg
4 foot black 180 degree IPS schedule 40 plastic pipe home made steamer.jpg
2 cap strips in home made steamer.jpg
home made steamer is a pressure cooker with 2 inches of boiling hot water.jpg
pre bending steamed cap strips 2.jpg
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Re: pre bending cap strips

Postby trackwelder » Thu Aug 08, 2013 1:05 pm

I found that by picking the most flexible strips, I didn't need to steam or soak my capstrips, I have used almost the exact method for building snowshoes though with 1 inch square pieces of oak, I used the bending test, and clamped all of the ends to my work bench and used the ones that bent farthest down for my capstrips and the ones that didn't bend for my truss pieces.
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