Replies

1. 
   KeithNewton | Sep 15, 2007 08:05am | #1

   Hey Frenchy, Your shall we say casual description of your set-up leaves me with a few questions.

   first, and abundance of water, won't help anything, but may take three times the BTU''s to get up to 210º, where 15% MC would be about right, and take much less time.

   Uh. Extremely heavy pipe? What material? If you are using metal, and uninsulated, I would be surprised if you are getting the temperature up high enough to do any good, due to heat absorption conducted into a large massive pipe, especially if you are using it without insulation. I like to drill a small hole in the far end of my chamber to fit a food thermometer through, so I can know exactly how hot it is at that end.

   However, since cedar is a softwood with really long thin cell-walls, I am not sure that you can even get a true bend, as in cell slippage with new memory if it were bent down the grain. But I know they do this, so maybe it works across the short way.

   I have to wonder, are you using any metal compression strap to make the bend only feel compressive forces? You May have to rip all of the shingles to one width, and have some sheet-metal folded so you can bow the shingle across the grain to pop it into the metal back-up plate, then bend it over the form, so that the neutral axis is along the plate, and the whole shingle is in compression.

1. 
   frenchy | Sep 15, 2007 05:15pm | #2

   Keith Newton,

    Yeh I know,, if I put full details in it get's too long to bother reading.  too short and I spend my time answering detail questions..

      OK the steam box is also my bending form.  it has  the female shape I'm bending to the pipe is 64 pounds  (a really high grade of  steel)  and has the male radius I need bent into  the shingle so it's a positive form..  the pipe stays in the steam box so it's at steam tempurature. The box is set to provide an even distribution of steam with a drain hole to recover spent steam and roll it back into the boiler.  

     My boiler is a bit crude it's a 5 gallin gas can (gee I hope I remembered to empty the gas out before setting on the stove;-) I've tried various amounts of water to see where I could produce the maximum amount of steam and it seems about three quarts is about right.

    I've tried various widths of shingles and it seems like about 4 inches is the maximum I can bend with any degree of consistancy..

     This works, sorta for the 18 inch radius bends but I am worried about the six inch radius bends..

1. 
   saschafer | Sep 15, 2007 07:38pm | #3

   You'll probably get better results if you can rig things up to ensure that the tension side of the piece is completely constrained, so that all of the bending force is taken up in compression of the wood.

   -Steve

    

1. 
   frenchy | Sep 15, 2007 07:47pm | #4

   saschafer,

    Thanks, I'll try that aproach with the 6 inch radius forms..

1. 
   KeithNewton | Sep 17, 2007 02:38am | #5

   French, My last paragraph is what Steve was saying, but I still would monitor the temp, because the lignin does not get soft, or become plastic, until it is up to near 210º. If that thick pipe is conducting too much heat out too fast, you just can't get there.<I have to wonder, are you using any metal compression strap to make the bend only feel compressive forces? You May have to rip all of the shingles to one width, and have some sheet-metal folded so you can bow the shingle across the grain to pop it into the metal back-up plate, then bend it over the form, so that the neutral axis is along the plate, and the whole shingle is in compression.>

2. 
   frenchy | Sep 17, 2007 03:50am | #6

   Keith,

       By microwaving the soaking wet shingles  I  get them to over that 210 degree point within 4 minutes.. I found keeping the microwave working an additional minute causes the shingles to dry out and start to get stiff. less than 4 minutes and they are too stiff to bend.. .. all this time that pipe is sitting and has been sitting in the steam box at the temp the steam box is at.  You don't grab it without a decent oven mitt! the pipe forms the male portion of the mold.   The pipe is almost an inch thick so it retains heat well..  The female portion of the mold is formed in the steam box. So I have both a positive and negative mold to which the cedar shingle must conform to once the lid is closed..

    I don't have any way of checking the temp in the box  but the steam is equally spread around the box.  I have tried keeping them in the box both longer and shorter times. shorter times and the shingles straighten out by the time they get up to the roof.. (about 30 seconds or so) longer times don't seem to do anything.