Second stem blank

I bent the second stem blank today without any cracking.  The steam box got up to 205F and I steamed the blank for 2 hours.  This time I bent it from the deck end down to the keel, which worked better because the last bit was fairly straight and I had better leverage to bend it.  I tried sawing the bevel on the broken pieces from my first stem bending attempts on the bandsaw and it looks like it will work well if I set the bandsaw table to 15 degrees and saw to the corner of the square stock.

Steam bent stem blank

I took the stem blank off the form today and the springback was much less than the prior attempt.  Looks like it really took the shape.  Getting it up to a higher temperature and steaming for a longer time really made a difference.  I took off the compression strap and clamped it back on the form for safe keeping.  My form is wide enough that I can bend the next one and keep them both on the form.  If time allows, I'll try and bend the second one this weekend..

Second bending attempt

I changed the steam box setup to use a shorter connection to from the keg to the box and sealed the lid a bit better.  This time the box got up to 210F. The bad news is the insulation board started to warp. It's still holding together, so I think it will last through the end of the project, but if one were to build one for more permanent use, a layer of wood is necessary. 

The bending worked better this time. No cracking sounds and no sign of cracks after sitting overnight on the form.  The higher temperature combined with a 2 hour steaming seems to be what made the difference. I also had Laura helping clamp as I bent the stem.

Cracked stem blank

It looks like the 'good' stem I bent yesterday also cracked.  I'll need to try again.  I still have two unbent blanks, so in theory I have enough material.  I can use the cracked one as practice pieces for the next step, which is cutting the blanks to a vee shape on the bandsaw.

Steam bending stem

While the stem blanks were steaming, I rounded off the thwart blank and sanded it. It's a bit lighter than the other one, but I can probably match them up by bleaching the old one or slightly staining the new one.

I soaked stem blanks overnight in the bathtub and then steamed for about an hour at around 190F.   I probably should have made the steam box smaller, so I could have gotten it hotter, but this seemed to work okay.

Bending the wood has to be done slowly, but you can't take all day either.  There is a limit to the working time where the wood is still pliable.  You can't have too many clamps, or clamping points. I added three more holes to clamp to after I was finished.  The first board cracked, which give you a reference point for bending the next one so you don't use too much force, or bend to quickly.

All clamped up, I'll leave this on the form to dry for a week or two.

Steam box, stems and thwart

I made this box for steam bending the canoe parts.  It's 8 feet long by 1 foot square.  The ends are 3/4" plywood and the sides are foil faced 1" insulation board. I'm hoping the board is good for 212 F.  Eight feet long is long enough to steam the gunwales one end at a time.  

 I cut 4 stem blanks to bend and made a compression strap from nylon webbing and scrap lumber.  I idea behind the compression strap is to force the outer part of the bent wood to be the neutral bend axis and the rest of the cross section to be in compression.  The wood will break if it is in tension during the bending process.

I cut the blank for the replacement thwart using the good one as a pattern. Once I get the profile smoothed up, I'll round off the edges with the router and finish shaping it on the spindle sander.

Materials

I got my order from Jamestown Distributors (varnish, brush, epoxy) and Northwoods Canoe (new hanger bolts, ring nails, canoe tacks)in the last couple of days.  I also picked through the cedar boards at Menards and found some with few knots and nice vertical grain direction.  I just about to start building instead of taking things apart and stripping finish.

The varnish directions have you start with nicely sanded wood (1), apply the first coat thinned 50% and sand with #220 grit (2), apply coat 2 thinned 25% and sand with #280 grit (3), coat 3 thinned 15% and sand with #280 grit (4), 4 more coats thinned 0-5% and sanded with #400 grit (5, 6, 7, & 8 times to sand the whole canoe interior).

I just bought 1 can so I could do the seats and thwarts. I'm not sure how many cans I'll need to do 7 coats on the whole canoe.

The weather is finally supposed to cool down, so I'll be able to get a bit more work done.