Tuesday, June 26, 2012

Less is More...

This can only explain my lack of posting. Keeping busy these past few weeks taking care of business around home. New steel roof and repair of some carvings I did several years ago.

Steel roofing was a whole different animal than asphalt shingles when it came to flashing the skylights and chimney. Plus getting the steel under the solar hot water system panels was a challenge. Good learning experience though.

Carved in 2007 these carvings did quite well until the woodpeckers got into the act and did some serious damage. First I put some wire over the hole then covered the area with fiber glass drywall tape. Next a fiber glass cloth mesh was stapled over the entire carving. Two coats of resin and the carvings were weather and bird proofed. Above you can see the restored and repainted carvings mounted in place.

Now with all these distractions taken care of it is on the the business of building bridge # 6 for the cabin land.  I promised myself that I would take my time and enjoy every minute of this project.

Here is a list of several key points that must be considered in the process for today's work:
- Orientation of the annual rings in each piece for the A and B chord layers.
- Orientation of the natural crown in each piece to match the desired camber.
- Relationship of the center of the chord to the false work it rest upon for clamp clearance.
- Relationship of butt joint and false work to location of lattice for hole drilling clearance.
- Stagger of all butt joints in the chords using 4 foot units.
- Placement of parallel block clamps at each butt joint for face and edge clamping.
- Forming of camber into chord layup and blocking in place.

So let the process begin:
False work in place and raw materials ready to go.

Annual ring marked on each end and a nail was driven into the crown edge of the board for reference.

Using combinations of 8'  -  12'   -  16'   or  20' pieces it takes 3 pieces to make each chord layer. Two layers make up the outside chord of each truss. The tricky part is to arrange the different length pieces so that no two butt joints line up with each other. In the picture above you can see a small square sitting on a butt joint in the first chord layer. When the next piece is put in place there will be 8 feet between each butt joint. When the two layers that make up the inside chord are placed in a few days there will be no place where two butt joints line up. This is important to the strength of the truss. Also all butt joints will be away from the location of where the holes for the lattice are to be drilled.

 And here you have it. Outside bottom and top chords clamped, arched and blocked with 4" of camber.

Next will be the task of "sawing up the kerf" of each butt joint and drive them together to make a rock solid butt joint for superior strength and load carrying truss performance.

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