Saturday, May 27, 2017

Beefing it Up

Since last week, I fileted and taped up all the new mast step components to the hull and feel that it really stiffened up the front part of the hull.  For the next step, I wanted to really beef things up so all the loads imposed by the unstayed mast will be properly transferred to the hull and nothing will break (cross fingers).  

To do so, I needed to beef up the framing members at the mast partners so the loads will distribute laterally from the partners to the hull via these new members.  Additionally, I decided to add a false bottom forward of the mast step that will tie the bow and sides into the mast step that should reduce or eliminate any twist caused by the loads.  

I started by measuring out a longitudinal frame running from the mast step to the bow about 100 mm above the keel.  I glassed that in place with thickened epoxy and after it had kicked, I coated it with unthickened epoxy to encapsulate the wood and added some douglas fir stringers along the top edge to receive the false bottom.

I left the aft section clear because I was planning on putting an inspection port in that spans both sides of the frame.  I let it all cure for a day and then created a template with the hot glue gun and some random sticks to pattern the false bottom.  I transferred the pattern to 6 mm marine plywood and cut it out for a first fitting.  A little work with the rasp and it all seated quite nicely so I went ahead and cut out a hole for the inspection port prior to gluing it up.

I coated what was to be the bottom side of the false bottom with unthickened epoxy to seal it all up and after letting it kick, I mixed up a batch of thickened epoxy and ran a bead along the longitudinal frame and smooshed the bottom in place.  I fileted the bottom to the sides and mast step bulkhead before letting it all kick.  I stopped back at the shop later that evening after the epoxy had cured to the touch and mixed up a small batch of unthickened epoxy and taped the bottom to the hull and mast step bulkhead.  

The next day I started beefing up the top of the mast partners by epoxying in 25 x 35 mm mahogany pieces that run from the mast step along frames 10 and 11 to the sides of the hull to distribute the load from the partners to the hull.  I morticed a notch on each side of the aft piece for the beginnings of the deck framing as well.  I feel like I'm using all the wrong terms here and I'm guessing all of these pieces have specific names, but the pictures below should give you an idea of what I'm talking about.

Tuesday, May 23, 2017


I'm definitely moving forward, both literally and figuratively.  Figuratively in the sense that I feel like I'm getting a good amount of work done with minimal screw ups, and literally, because I am literally working on the forward section of the boat.

I think I said in the last post that I am going rogue on the interior build from here on out.  I'm still referring to the plans here and there, but not in any measurable way.  I'm winging it and starting with how things are arranged and built forward of the daggerboard trunk.  I still have to abide by physics though, and need to distribute loads from the trunk and mast step, so I started with the idea that I would build a seat/storage compartment between the daggerboard trunk and the mast step to help tie things together.

Since the forward end of the daggerboard trunk didn't land on a specified frame, I broke out the hot glue gun and made a template of the new frame shape with little sticks glued to a 2x4.  Once completed I transferred the template to a sheet of plywood and cut it out on the bandsaw.  The first fitting was tolerable and a few hits with the shinto rasp made the new frame sit just about perfect.

Moving on, I cut and fitted frame 11 which will sit about 200 mm forward of the frame 10 and will be part of the sandwich that makes up the mast step and partners.  For the mast step, I glued up a big blank consisting of sapelle and douglas fir.

Once it cured, I shaped the bottom to fit the curve/angle of the boat and screwed and glued more douglas fir and a 12 mm piece of plywood rabbetted to the fir for the actual step.  This will allow a channel for drainage underneath where the mast fits.  A bit hard to verbalize, so see the picture to make sense of what I said.

At this point I drilled the hole for the mast butt to seat and additional drainage holes and glassed the whole assembly in place.  I called it a day and let it all cure up overnight.  Next up was to fit douglas fir pieces that will serve as backing strips for the plywood that will enclose the mast step fore and aft between frames 10 and 11.  All of this amounts to what will likely be the most complicated assembly for the entire project so I spent a lot of time in
'contemplation mode' to make sure I could visualize everything needed to be done.

Once I was satisfied with all of my dry fits, I filleted in frame 11 along with the all the douglas fir backing pieces and after an initial cure, I hot coated everything with unthickened epoxy.  The next day I glued in the fore and aft side pieces to complete the mast step sandwich.  In the meantime, I cut out some plywood that will be mounted about halfway up the mast step on either side.  These will be glassed in and will serve 2 purposes: 1. they will be a shelf accessible through the bulkhead from the aft end, and 2. the area underneath them will serve as one of the watertight buoyancy chambers.

There is a bunch of glass taping to do in the next few days to tie everything together, but here's what it looks like to date:

Wednesday, May 10, 2017

Going Rogue

I deviated from the original plan since the last post and decided against doing a primer coat before I do the interior.  I did get a good chunk of the weave filled with 2 coats of unthickened epoxy and glassed the transom. I think it's looking pretty good now, but time to move on.

Instead of priming, I decided that it would be best to get the interior fitted before I tried making the hull look any prettier, so I marked and cut out the daggerboard slot and this is where I am basically throwing away the plans.  I plan on a number of modifications to the interior, including the daggerboard.

The plan calls for a 25 mm wide daggerboard with a long slot (basically about the same size as a centerboard trunk.  I talked to the designer about this and I decided that in order to optimize space, I would shorten the trunk because I only plan on building the standard rig, and not the light air rig which requires setting the daggerboard further back.  Additionally, I'm planning on building a NACA0012 foil for the daggerboard and if I keep the chord of the daggerboard at 280 mm, that means that the maximum width of the daggerboard is 33 mm, not the 25 mm as designed.

I won't go into much detail now, but in a nutshell, but NACA stands for National Advisory Committee for Aeronautics and the 0012 designation means that the maximum width of the foil is at 12 percent of the chord.  In other words, it will look a bit like a wing.  In theory this should allow the boat to point a bit higher before stalling.  I think it will be fun to build.  More on that when I get to it.

My son and I moved the boat outside and we flipped it over so I could sand the 50 mm tape in the interior to prep for applying the 75 mm tape over that.  Using 80 grit sanding disks on my 5" random orbit sander I was able to get everything acceptably smooth in about 2 hours.  I vacuumed it out and we moved it back in.

I measured and cut enough 75 mm tape to cover all the 50 mm tape in the bow and mid sections of the boat.  I'll do the aft section a little later, but for now I want to focus on the centerboard trunk and the mast step and forward assemblies.  Using 6 oz. batches of epoxy, I painted out all the 50 mm tape seams and then lay the 75 mm tape in it before moving on to the next.  After a few of these 4 - 5 foot sections, I'd circle back and make sure the previously laid sections were fully wetted out.  I always miss a few spots on the first pass so it's good to go back over them with a brush and squeegee.  Once I finished up I moved onto the daggerboard trunk and let the new tape cure.

The daggerboard trunk isn't complicated, it's just a hollow, rectangular box with the bottom cut to the shape of the hull so it seats properly, but it takes a bunch of steps to get it all together and ready to fit to the boat.  I should say that I really didn't follow the plans or construction key here at all, but I've done daggerboard and centerboard trunks before, and I know what works for me.  There are really only four things you have to keep in mind:

  1. Make sure your daggerboard will fit.
  2. Install it in the correct location (Center of Effort +/- lead).
  3. Make sure it is built stout enough to take a beating (because it will).
  4. The trunk has to spead the loads imposed on it to the boat without introducing major stress risers.

So to start, I had previously determined with the help of the designer a shorter length daggerboard trunk and located it on the boat (fore and aft).  From there, I scribed the bottom curve onto a piece of scrap and transferred it to the 6 mm marine plywood I planned on using for the sides of the case.  I cut each side of the case out to the proper dimensions and then epoxied what would become the inside of the trunk with 6 oz cloth.

Once that had kicked, I followed up with a coat of unthickened epoxy with 10% graphite powder mixed in.  I let it kick again and repeated with another graphite coating.  The thought behind the graphite is that it is a good 'lubricant' and provides a slicker surface for sliding the daggerboard.  I think there is plenty of debate on whether it works or not, but hey, it looks cool.

I let everything cure up for a day or so and then sanded the sides where the mahogany spacers would be screwed and epoxied into place to maintain the 35 mm desired width (for the 33 mm wide board). I clamped it all together and called it a day.

The next day I epoxied on some bed logs (scribed to the curve of the hull), which didn't seem to be part of the original plan, but I think they are crucial for stiffening up the trunk.  I also added top pieces that will be covered by a trim board once completed. At this point I was about done, so I cleaned things up a bit with a heat gun to get rid of the inevitable gobs that I missed when the epoxy was still wet and sanded and rounded the inside corners.

I fitted the board the next day and to my amazement, it all fit without a single hiccup.  I epoxied it to the hull with some thickened epoxy, and made a nice filet along the port and starboard edges before laying down a 75 mm wide strip of cloth to really tie it in.  Of course there will be frames fore and aft and a vertical stiffener about midway that will further tie it into the boat, but this was a good milestone.