Monday, August 30, 2010

Final Word On Portlight Configuration

Once again, I've made a change to how the fixed portlights in the outboard sides of the cabin will be installed.  My portlight saga is beginning to resemble Neil Hawksford's long-lasting "tumblehome saga" in the building of his Tiki 38, Gleda

This is the final change though, and the modifications have been completed and the window panels will be installed this week.  I decided against the overlay method as described in my last post because with the outer ring frames removed, the openings were of course larger and to have enough bonding surface for the overlay style of installation, the plastic window panels would have to be 1.5 inches wider than the openings all the way around the perimeter, creating disproportionately large windows that would adversely affect the lines of the boat.  Though it took a bit of extra work, I decided to do it the right way and the way that windows are installed in practically all modern boats and yachts - with an inner flange for bonding so that the window will be flush with the surrounding cabin side surface.  This is what David Halladay recommended from the beginning and I should have listened to him then.  It is also the way the windows are fitted in the GRP Tiki 8-Meter, a design David and the Boatsmith crew have now built three examples of, counting the new one under construction in his shop now.

Following David's instructions over the phone, I made new inner flanges from 6mm ply.  The flanges must overlap the inside cabin surface around the hull by 1 1/4 to 1 1/5 inches to have sufficient glue surface.  Then they must overlap the opening by 1 1/4 inches to allow for enough bonding surface for the acrylic window panel, which is cut 1 1/4 inches smaller than the opening all around the perimeter to allow for expansion.   The two adhesives of choice are Sikaflex 295UV or DOW 795.  I'm using the DOW 795 as it does not require a primer and seems simpler to use.  Both are incredibly strong and quite capable of permanently bonding the windows with no fasteners.  The key is to bed the window panels on a sufficient thickness of the sealant to  allow for movement.  To achieve this, I laminated a spacer layer of 6mm ply between the cabin sides and the inner flange rings.  That way, when the windows are installed, there will be a 1/4" bed of sealant and the window itself will be flush with the outside cabin surface.  More explanation of this later when I do the actual installation and take photos.    Here, I am laminating the ring frames with the spacers to the insides of the cabin:

And this is how the inside frames look now that they are glued in with epoxy.  I don't have a shot of the interior side, but on the inside the frames were finished to a nice radius with the router and will be varnished along with everything else inside the cabin. 

The 1/4 inch smoked cast acrylic that I ordered for the companionway drop boards also arrived last week and I cut those to shape using my plywood patterns:  The inboard sides of the cabin are not completely faired or painted and won't be until I move the hulls out and fit the beams.  Because I don't know the exact dimensions of the cockpit and where the seats will land on the cabin sides yet, I will wait until I can mock that up for accuracy before making and installing the rail upon which the seats will rest on the cabin sides. 

The opening Lewmar portlights for the aft cabin bulkheads have also been dry-fitted and will be installed this week.

Friday, August 20, 2010

Moving Backwards and Forward at the Same Time

I've managed to put a lot of time into the project for the past several days, although it may not look like much from the photos.  The list of things to do in order to get the hulls completely closed in with all hatches and portlights installed has been long and seems to be growing.  But I'm looking at having both of them out of shed shortly, it's just a matter of getting all the paint coats on the various parts done and then installing these components and waiting for the sealants to cure.

I took a few steps backwards on the portlights, but I think it will be well worth it in the end.  I regret all the hours I spent messing around with a plan that I've now scrapped, but better to correct it now than have to do it sometime down the line when I'd rather be sailing.  The problem was the ring frames that I made to sandwich the portlights between.  For one, I didn't design them with enough clearance between for a proper thickness of sealant, and two, I made the mistake of glassing the outer frames on first, requiring the ports to be installed from the inside.  Attaching them from the inside is problematic in many ways, first to make this attachment strong enough, and second, to get a good seal.  Another reason for scrapping this idea is that further research and conversations with David Halladay regarding the materials used led me to the conclusion that Lexan is not the preferred lens material and that the ports should be instead made of cast acrylic, which is what all the major hatch manufacturers use.

So to fix all this, I first had to grind off these nice exterior rings that had been so time-consuming to glass and fair into the sides of the cabins:

After a few hours with the belt sander and then the 6-inch random orbital sander with 60-grit, I was back to a flat cabin side surface:

The new portlights will be the overlay style, the perimeters of the lenses overlapping the openings by 1.5 inches all the way around.  There will be no holes drilled and no screws or other mechanical fasteners - the lenses will instead be bonded with sealant the same way that most all modern portlights are attached.  I was skeptical of this at first, until I realized that this is the way large, heavy glass panels are often installed in skyscrapers and other structures, and until I saw first hand how well it has worked on some of the windows David and the Boatsmith crew have installed.  The recommended sealants are either Sikaflex 295UV or DOW 795.  I'm going with the DOW 795 because it is a one-part sealant that doesn't require special primers, as does the Sikaflex. 

My order of cast acrylic to make these from arrived yesterday.  This is great stuff compared to the Lexan I had before. It comes with a heavy paper protective cover on both sides that's easy to mark and stays in place while you're cutting and sanding.  Here you can see my plywood patterns used to mark the outline of the new windows.  The small piece in the foreground is a scrap from which I peeled away the paper.  It is smoked gray in color, a shade darker than the smoked gray Lexan I had.  This cast acrylic is more U.V. resistant and more scratch resistant than Lexan.  It's also stiffer so that it wont flex if a wave hits it, which could break the seal.  That's why hatch manufacturers use it.  If you step on a deck hatch it won't flex under the weight.  The only area where it is not is good as Lexan is in impact resistance, which is why Lexan is used in bulletproof windows.  Hopefully, no one will be shooting at me, so it's not an issue. 

This material cuts and sands well. I cut out the ports with a circular saw, then rounded the corners with the belt sander.

Another job completed yesterday was some major sanding of the stern decks, toe rails and sheer stringers, and then the application of the first coat of primer to those areas. Everything on the hulls and decks is now either painted or primed.  Today is the first sunny day we have had here in over a week.  I will spend the morning putting another coat of paint on the cabin sides, companionway hatches, and other small parts.

Thursday, August 12, 2010

Back at Work....

Once again I've had a long absence from posting here.  I miss the days when I was tackling this project every day with enthusiasm, and this blog was the only thing I had to do on the computer and online.  Lately I've just been putting in too much screen time researching and writing my newest book, which is coming along but still far from done.  It's hard to spend any extra time taking photos, processing them and posting on blogs, but I hate to leave those who may be building their own Tikis waiting indefinitely for my updates.  So to let you know I am still working on the boat, here is the latest:

The decision to switch from the standard shroud lashing pads in the plans to regular bolt-on, external chainplates created a lot of extra labor and expense.  But regardless of that, I firmly believe it is well worth it for the secure means of attaching the Precourt terminators and deadeyes I will be using for my shrouds, as discussed in an earlier post. 

I fabricated the chainplates myself to get the exact dimensions and fit I wanted.  They are 3/16" thick by 1 1/2" wide, and 12 inches long.  316 stainless steel plate is hard to drill, bend and polish, but eventually it was done, and I'm well-pleased with how they look.  I didn't want a highly-polished glittering yacht look, just the rugged purposeful appearance that externally bolted-on chainplates exude.  (Note that I painted over part of this section of the topsides when painting the sheer and cabin sides.  The green topside paint will be brought up to the bottom edge of the sheer stringer.  I just wanted to get everything in the way of the chainplates painted so I can permanently bolt them on.  It's easier to bolt them on at this point, before I install the portlights, as I can reach through the window openings to back up the lock nuts on the inside - important considerations since I'm working alone).

This morning I completed the backing plates for all the chainplates and bolted them up to check fit.  They will be removed and then permanently installed with 3M 5200 as soon as I polish the backing plates a bit.  Then the windows can go in as soon as that's done.

Here you can see the clearance at the tops of the chainplates for the Precourt terminators.  None of the ready-made chainplates I could find, like Schafer's, had enough length above the sheer to keep the terminators from hitting the cabin when the shrouds go slack.  These do.  Note also that the pin size for the terminators is 1/2 inch.  This will certainly be as strong as any part of the rig.  Each chainplate is through-bolted with four 5/16" bolts. 

Here's a view of the inside backing plates in the starboard hull.  I didn't want to use individual fender washers for this application, as it is all too common to see them literally compressed into the wood by the strain that is put on the chainplate bolts under load. (This part of the interior is still only epoxy coated.  It will get sanded and faired and then finished with varnish). 

I'm also preparing to permanently install the companionway hatches.  Here, they have just received the first coat of paint after fiberglassing, fairing and priming:

The cabin tops and coamings are done.  It's hard to see the edges in these photographs, but I've laid-out a non-skid pattern for the walking surfaces on the cabin tops.

Here you can see the non-skid somewhat better.  This was the final paint coat that I applied this morning.  When this has had time to completely dry, I will permanently install the Bomar hatches in the openings on the forward ends of the cabins.  I placed an order yesterday for the remaining primer, paint and sealants to complete all these jobs.  Within a couple of weeks I should be moving these hulls out in the open to make room in my shed to bring in the beams that are still in my girlfriend's garage where I built them.  I still have some sheathing and fairing work to do on the three beams before they are ready to prime and paint.