Friday, September 30, 2011

It looks like a boat!

Now that the panels are spliced together and the parts drawn and cut from the panels, it is time to actually start to build a boat.

The first thing I noticed when looking at the strong back was that there was no easy way to position the first panel to the strong back.  I fixed this by making small clips that I aligned with the bottom of the strong back and screwed to each strong back bulkhead.
As the plan instructed, I installed the first panel at the bottom of the strong back on one side by using two drywall screws at each bulkhead.  I made sure I extended the aft end of the panel past the last bulkhead by the same thickness as the transom.

Once the panel was attached on one side, I attached the opposite panel on the other side.  This assures your hull will be straight and not shaped like a banana.  I also verified the straightness with a string tensioned across the top of the strong back.

I continued by installing the next row of panels.
When all the side panels were attached to the strong back, I drilled adjacent holes along the length, 5 per bulkhead space, and I used zip ties to stitch the panels together.  I was concerned by the shape of the hull and the sags between the bulkheads until I zip tied everything together.  Doing this pulls all the panels to their proper curve.  The last step was to attach the bottom panel or the top part on the strong back.

I now have a complete hull that needs to be epoxied together, joints taped and fully glassed.  Since I had a full set of float parts, I decided to wait on the epoxy, fiberglass work until I got the first float stitched to the strong back.  Here are the photos of the same steps used to complete the first float.

On a last note, I've been trying to think of a good name for my Scarab.  So far I have "Cygnus" meaning "the swan."  I think this name is very fitting since trimarans are very graceful under sail.  I found this poem that is fitting.  It is by Susa Morgan Black....

Swan of beauty, swan of grace
A queen among her ancient race
She glides across the mirrored lake
No ripple does the surface break

It is very fitting.  However, recently I've come up with a second name, "Cricket" because of the annoying little cricket that has moved in to my garage and sings to me constantly when I'm working!!  I'll let you know what I decide.

Fair winds!!!

Tuesday, September 13, 2011

Plywood Scarf Joint

A couple of posts back I came up with a fixture that would help me make a scarf cut on the 4 foot length of the plywood sheet that provided a feature to strongly bond 3 sheets of plywood end to end.  I need a sheet of plywood 24 feet long to make the panels for the main hull and floats.

I clamped the sheet of plywood adjacent to the fixture and ran a circular saw along the edge to make the cut.  Once I had the scarf joint cut on all three sheets, I applied epoxy thickened with wood flour to the joint and aligned the sheets.  It is very important to make sure the long edge of the sheet is straight since this edge is used to layout the parts.  After the sheets were aligned, I placed a two by four on top of the joint and clamped the piece tightly to the work bench.  I also placed a sheet of plastic drop cloth between the workbench and the clamp board.

After the epoxy has cured for 24 hours, I removed the clamps and used a belt sander with a 120 grit belt to sand the joint smooth.  I sanded both sides. 

Once I had made two panels, I decided to use my two workbenches as a fixture by screwing stop boards to the long side of the bench and using a string to align both benches in a straight line.  Now I just push the 4 x 8 sheets up against the stops, align the scarf joint so the overlap is correctly position and then clamp the joint for curing.  Aligning the benches makes sure the panel is straight.  The process works great!

Next step...Lofting and cutting the panels.

Prodder Tube Assembly

The first part of making the prodder tube was the fabrication of stem support and the forestay tang.  Both of these parts are cut from fiberglass laminates as defined on the plans.  I started by making shallow boxes that I lined with plastic drop cloth material.  I found that Epoxy does not stick to this material.  The drop cloth acts like a mold release.  I cut the triaxial cloth to fit the box, wetted it, placed another piece of drop cloth on top, and covered with a piece of plywood and some weights to keep the laminate flat.
After the laminates cured, I cut the pattern from the plans and bonded the pattern to the laminate using a glue stick.  It holds the pattern in place for sawing but removes easily once the parts are cut.  I cut the two parts using a scroll saw, washed them with warm water and detergent and sealed the edges with epoxy. 

Stem support

Forestay Tang

The plans suggest making the prodder tube by laying fiberglass over a mandrel and then removing the mandrel once the glass cures.  This provides a fiberglass tube.  I decided to use an aluminum tube instead.  I found a tube with the correct ID and a 1/16" wall.  I cut the tube to length and plugged one end with a plywood plug.  The plug was completely coated with epoxy and epoxied in place.  I roughed up the outside surface where the stem support and forestay tang would attach.  Using thickened epoxy, I bonded both parts to the tube using fixtures to make sure they were correctly located and square to the tube.

Once both parts were bonded to the tube and fully cured, I applied the Fiberglass strapping as defined on the plans.  I also completely covered the tube with fiberglass to prevent denting since the tube is exposed inside the anchor locker.  I'm very pleased with the results.

Having spent enough time building parts and fixtures, I decided to start building the main hull and floats.  There are still many parts that need fabrication, but I really need to see this project start to look like a boat!

Next step, bonding 4 x 8 plywood panels to make a 4 x 24 foot panel!