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!!!



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!



Material decision made

I completed a second study of material costs and I've decided that my Scarab 650 will be built using plywood instead of foam.  I just can't get myself to pay three times the cost of plywood to build this boat in foam.  I found good prices, but I found even better prices for plywood.   However, prices aside, the decision was made based on a conversation with a fellow boat builder who owns a composite material buisness.  I was speaking with the owner of Express Composites in Minnesota about trying to get a better price on marine foam when he started asking me quesitions about why I wasn't considering plywood.  I thought this odd since he could potentinally loose a pile of foam buiness.  I found out during the conversation that he is a serious wood boat builder, power boats, not sail.  He suggested that prior to applying the wood parts to the strongback, I should coat both sides and all edges with epoxy and allow it to cure.  This seals the wood completely.  I agreed that that would be a great idea.  He also told me that doing so will easily make the plywood last 25 to 30 years.  He then asked if thought I would still be sailing this boat in 30 years.  I did the math and agreed it was highly unlikely.  I then asked him about damage.  I asked "what happens if I hit the dock really hard or run aground on a gravel shore and bust up the fiberglass that will cover the plywood?"  He then told me that the repair to wood would be less work compared to the same repair on a foam boat.  He said with wood, the damage will remain close to the site of impact.  With foam, you can experience delamination sometimes 8 to 10 feet away from the impact site depending on how serious the impact.  It was at that point I decided to go with plywood.

The plans call for 34 sheets of 6mm plywood for the majority of the hull parts.  Not wanting to spend that much money right now, I picked up 25 sheets of 1/4" which should be enough to build the floats and the lower hull.  Here is the pile

The next challenge was coming up with a way to make the scarf joint along the 4' side of the sheet.  I will need to bond 3 sheets together to form a 4' by 24' sheet.  I did quite a bit of internet research and found many different ways to join the panels.  I really like the way Chesapeake Light Craft joins panels in their Kayak kits but the method requires laser cutting or 3 axis routing.  The second best method I found is to angle the end of the sheet with a slope of 7 to 1 based on the thickness.  Some builders use planes, sanders or circular saws.  I decided to use the cicurlar saw method.  I figured if I made sure the blade was square to the fence that is attached to the saw, I would need to tip the saw about 7 degrees to angle I need.  My plan was to clamp the sheet to my workbench with the sheet flush with the end of the work bench.  I would then build a fixture that would attach to the end of the bench that will guild the saw and provide the tilt I need to make the cut.  Here is what I came up with.

Attached to the end of the workbench

I did a test cut on a scrap piece of plywood and fixture works great!  I can't wait to start bonding the plywood.  However before I start that step, I'm going to build the prodder tube assembly.

Until next time...fair winds.

Centerboard is finally complete

While I was back in "material search" mode, I decided to complete the centerboard. 

I left the board shaped and glassed the last time I worked on it.  The only work need was a final sanding and finish.  I was surprised at the amount of sanding needed to get the board smooth  and sleek.  I was also amazed at the number of pin holes uncovered during the sanding.  I sanded the board smooth, applied a fairing compound of thickened epoxy and sanded again.  This is the final result.

I also needed a stainless steel bushing for the pivot bushing.  I ordered some stainless steel tubing with the right I.D and a thick wall so I could include some grooves to help bond it in the board.  I had my machinist friend make the bushing and it turned out nicely.

I finished the centerboard by applying two coats of marine paint.  A funny story here.  I wanted the board to be white so I ordered a quart of bottom paint from Jamestown Distributors in the color called "shark white."  Who would have thought that shark white was actually gray!  I didn't!

More to come....

I'm rethinking foam vs plywood.  Its been a few months since I checked prices so I plan to requote the foam....

Much Progess during early summer 2011

First, some sad news.  I lost my best friend a few weeks back.  His name is Frosty and he was always in the shop with me help any way he could.  Mostly he would lay down and spread the saw dust all round the shop with his tail!  Here is a photo of Frosty sitting on the hose for me.

Rest in peace my dear friend....I will miss you.

As I indicated in my last post, I was starting work on the strongback for the main hull and floats.  I purchased 7 sheets of cabinet grade, 3/4" birch plywood to cut the parts.  The plans did not indicate part layout on the plywood like what is provided for the hull components.  So, I spent the time to draw all the parts using a CAD system and played around with laying the parts out on sheets of plywood that would minimize waste.  I can provide this layout to anyone who requests it.  I also discovered when I was drawing the parts that the longitudinal members that make up the hull strongback were not tall enough.  The way they are drawn on the plan, the bow would extend below the strongback if built per the plans.  I contacted Ray about this and he stated that you just need to block up the strongback for bow clearance.  Not wanting to do this, I just made the parts taller.  To minimize plywood waste, they ended up 600mm high.

When cutting the parts, I cut the slots a little smaller and I fitted each part by filing the slot for a snug fit.  This made the strongback extremely rigid.

The strongback for the floats was built exactly as the plans with no changes.  Again, I filed the slots for a tight fit which is very important for this fixture.  I could easily see the strongback moving if the fit was sloppy which would produce a banana shaped float!  I also drew center lines on both sides of the formers so I could string a line to make sure all formers are in alignment and straight.

The next step is to start building the hull and floats.  I have not had any luck finding foam that is reasonably priced.  From what I found, foam will cost $5500 usd whereas plywood would cost $1800 usd.  I think I am going to build my boat using plywood unless someone can point me to a foam source that is a little more cost competitive.  Next steps, I need to design and build a fixture to cut a scarf joint for joining 1/4" plywood sheets.

Until next time....

Molded Beam - Fail

The first molded beam was a total failure.  The part turned out so, so, but I had to destroy the mold to get the part out.  All the waxing and mold release worked perfectly with the exception of an area on the top of the beam, about the middle for about 20 cm.  This area stuck so bad, the beam still has plywood bonded to it.  Needless to say, I was very disappointed.  However, I didn't get that discouraged to scrub the entire project.  I got out the plans and modeled the beam using a CAD tool and sent the model to a local composite prototype company that often does work for Mercury Marine.  They looked at the design and wanted to meet with me to discuss the project.

When I described all that I had done with my attempt they came up with two suggestions that would have probably gave me success.  First, the suggested that the mold should have been built so it would split or for a side to come off.  Once this suggestion was made, I saw how simple it would have been to make the mold split in half.  The other suggestion was to change the process of laying up the part.  In the instructions, Ray states that you apply a coat of resin to the mold and let it tack up.  Once it is tacked up, you start to apply the cloth as per the laminate schedule and you can not stop until you finish.  The composite company told me that when you lay up a laminate using this method, the part will shrink very tightly to the mold and if the mold is a light weight plywood mold like this mold, it often will suck the mold in when curing making it almost impossible to remove the part.  This is exactly what I experienced.  The composite company suggested that I should have let the first layer of the laminate (chop cloth) fully cure before adding the remaining layers.  This will greatly stiffen the mold and probably prevent the distortion of the plywood mold.

I then talked to them about what it would take to have them make the 4 parts for me.  I instructed them to give me a quote for 4 molded beams, untrimmed and unfinished.  When I got the quote for the mold and four parts, I told them to proceed with the build!  I figured the little extra money was worth knowing the beams will be built correctly and not fail.

Since the beams are under way, I will now focus on building the hull, floats, and finishing the centerboard.  The seven sheets of plywood on the workbench are for building the two strongbacks.

More to come....