Attaching the bow

 I didn't get too much done on the trimaran this week because we are getting the monohull ready for the sailing season.  At this point I just want to get on the water.  Nonetheless, I spent a few hours today sanding one side of the hull in preparation for final fairing (yeah, more sanding and fairing!)  The biggest difference being the dust is now super itchy thanks to the glass fibers.  Of course the intent is to not sand down the glass fibers since that is the source of the strength of the boat.  Rather, I am just trying to take off the gloss so the next layer adheres properly.  Epoxy doesn't adhere to itself very well, so the scratches from sanding provide a mechanical grip for the next layer.

We also glued on the bow foam.  If you recall, we glued up a block of scrap foam a while ago, and then trimmed it to rough shape on the band saw.  To attach it to the hull, I mixed a thin batch of epoxy putty following this recipe: 150 mL epoxy + 1/2 cup microballoons + 1/2 cup cabosil.  The balloons provide extra volume to fill gaps and the cabosil helps reduce dripping.  It is still a thin mix so I could press the bow on and squeeze out the excess.

I used two screws to hold the foam bow on to the hull while the putty set.  The screws tend to pull the foam up, so I loosened them slightly and put a couple wights on the forward edge.  This balancing act seemed to align the centerline of the bow foam with the hull.  It doesn't need to be perfect since the next step is carving the foam to a finished form.  This might be a good job for Dawna, the artist-extraordinaire.

You may also notice the shiny area on the forward end where I squeegeed out the extra putty.  I am testing an idea to apply a thin fairing putty to fill in the glass weave without requiring to much additional sanding.  Being thin, it tends to settle smooth like glass.  It also spreads uniformly so there aren't overly thick or thin areas.  The hull is very fair at this point, so this might allow me to finish fairing in one last pass (fingers crossed for luck).

Finished laminating the starboard float

 We finished laminating the other half of the starboard float today.  We spent several hours prepping the hull for the glass by sanding the epoxy and glass applied yesterday where the two sides overlap.  Sanding pure epoxy and glass is much harder than sanding putty and foam.  I am very glad I did the majority of the fairing before applying the glass.  So we didn't start mixing epoxy until early afternoon when temperatures in our greenhouse-like workshop were in the 90s.  Nonetheless, the glass and epoxy went on quite well.  We did set the paint trays with the epoxy on top of ice packs to keep the epoxy from kicking too fast.

In this view, you can just barely see the reinforcing strip along the hull.  This was applied after the full laminate was complete.  We find it is best to let one layer start to set before applying extra layers of fabric.  Otherwise we end up with too much epoxy and the layers are more likely to distort.  You can also see the peel-ply wrap around the stern to hold the edges of the fabric tight while it sets.  Pointy or complex intersections like this are difficult to get tight.  You have to think about how the overlapping edges interact so that one edge doesn't loosen another edge.  I have had mixed success in getting this type of intersection to come out tight and fully bonded.  Peel-ply definitely helps.

Here is the deck of the float (on its side) all laminated and awaiting final cutouts for ports.  Of course first we will do one more pass with fairing putty to fill the weave of the glass and blend the few unavoidable seams.  Then we can add the bow and access ports.  I think we will finish this float in a couple of weeks and then we are on to the port float.

A better mousetrap ... er, scissors

One minor issue I have when cutting glass fabric is the warps (individual bundles of glass fibers) are pushed around and distorted if I am impatient and push the blades of regular scissors into the fabric faster than I am shearing.  Dawna suggested trying one of these rotary scissors popular with quilt makers to cut the glass fabric.  I found it worked great.  I used a piece of aluminum bar stock as the base to roll over so I wouldn't tear up my work table.  Since the cutter rolls over the warps as it cuts, none of the material moves.  The result is a very clean cut with no distorted weave.  So far I have just cut straight lines in one of the directions of the weave.  But I think this will work just as well when cutting at an angle to the weave or along curves.  I am not sure how long this blade will last, but they are pretty inexpensive (at least compared to $50 a pair, industrial grade, fiberglass cutting shears).  Of course, when I am trimming glass on the hull and can't move the material to the work table, I just have to be careful with my regular old shears.

Glassing the exterior of the starboard float (finally)

I know its been awhile since the last update (1 month and a day), sorry for the lack of updates.  Progress has been somewhat slow, and pictures of fairing is just not that interesting.  In all, I think I applied putty and sanded the entire hull a total of five times ... five miserable, shoulder burning, lungs gasping, just shoot me already, times!  Keep in mind that the number of iterations was not because the hull wasn't already fair, but rather to address all the fine details now while it is relatively easy rather than waiting until the glass is on.  In any case, the hull is very fair, so it is time to move on to the next step ... glassing the exterior.
Being the exterior, and considering all the effort that went into making the hull fair, we wanted to ensure the exterior laminate had minimal seams to sand.  So we decided to lay on the glass in a single sheet rather than overlapping 50" sections.  This wastes a little more glass (5 feet to be exact), but it eliminates five overlapping seams.  Of course, laminating a single glass layer that is 24 feet long is a little tricky (at least for novices such as ourselves).  I couldn't come up with a way to wet the surface in sections before rolling out the glass that I was confident would work.  So we ended up laying out the glass dry and then rolling on the epoxy.  Here you can see the glass fabric covering the hull awaiting a slimy, sticky epoxy glaze.

Here is Dawna working away at saturating the glass.  It is important that the glass be fully saturated to ensure the epoxy bonds the glass to the foam.  We also squeegeed the glass periodically as we progressed to force out any trapped air bubbles.  It sounds like miniature kernels of popcorn popping  as the tiny bubbles are forced out.

 And here I am doing some final touch up work on the extra reinforcing strip.  It took about three hours to epoxy the entire half with both of us going continuously.  I mixed all of the epoxy and Dawna did most of the application.  It is a good idea to have one person focus on mixing epoxy so the batches are consistent.  We smoked one batch (literally, smoke rising and plastic liner distorted by the heat) when I dumped a new batch into a partial batch that had been sitting for too long.  After that, we made sure we always finished a batch before making more.

And here is the view at the end of the day.  The laminate came out very clean and uniform.  You might notice the extra fabric on the bow.  This is peel-ply that I applied to hold the edges against the foam tightly until it cured.  We could have applied peel-ply to the entire hull, which could save a lot of final fairing effort if done right.  I felt that we were already moving pretty fast just keeping up with the epoxy we were applying to the glass.  Trying to add the peel-ply on top without screwing it up seemed like too much of a risk.  Plus I expect I would need to do some final sanding even with the peel-ply, so maybe more effort than it is worth.

Still fairing

 I know its been awhile since I posted any updates, but I could only show so many pictures of the starboard hull being faired.  Although the construction method described by Ian Farrier results in fair hull lines naturally, it still takes some time and effort to get the details just right.  And since the exterior surfaces are seen by the world (as you sail by at Mach 2!), I want them to look professional.  So I have made three passes with fairing putty and longboard torture.  Here you can see the last thin touch ups with putty freshly applied to one side.  I hope to have this stage of fairing complete this weekend so we can move on to exterior glass.  But I think it is easier (and maybe better) to fair now rather than after glass is applied.  We will have to do a final fairing after glassing to fill the fabric weave and blend any seams, but that should be minimal.  Then we get to do it all again on the port hull (my muscles ache just thinking about it!)

While working towards an elusive perfection, I noted some subtle waves in the hull surface.  No doubt these were due to my inexperience.  But these features had a scale similar to the 30" long fairing boards I was using.  As a result, these fairing boards would never be able to smooth these features, so I needed a longer board.  I decided to make a 5-foot long board out of 1/2" plywood.  I found wooden knobs and mounting plates intended as feet for furniture to be an excellent hand hold.  Initially I set the knobs about 8" further towards the ends of the board, but after about a half an hour of use my shoulders were on fire.  So I moved them closer and my shoulders have been slowly recovering.  I use 4-1/2" wide, self-adhesive sandpaper cut from rolls on this home brewed board.  The adhesive works well, plus I fold the strips around both ends and hold the ends in place with staples for extra support.  I also sanded the bottom ends of the board to a gradual taper so the board tends to ride up and over features until they are blended.  All in all, it works very well and the waves are quickly disappearing.

Rounded keel and more fairing work

 It took a couple of hours to knock the keel down to the specified radii.  I was a little hesitant since it is harder to put foam back on than it is to shave off.  But with reassurance from Ian Farrier (which was remarkable if for no other reason than he had just experienced a serious earthquake in New Zealand the same day I emailed him), I went ahead and rounded over the keel.  The logic is the soft radius reduces wetted area, making for a faster boat.  I was careful to knock it down along the entire length simultaneous so as to avoid an irregular keel line.  I used the cheese grater for rough cutting and the long board for final figuring.

Here is an interesting view from the stern looking forward along the keel.  I am really happy with the figure of the hull and keel.   I think there is pretty good symmetry, and the lines of the hull seem to flow nicely.  Now I get to make it ugly again!

And here is the next step in fairing prior to glassing.  We skimmed the surface with a slightly thin fairing putty (1.25 cups balloons per 150 mL mixed epoxy), and then scraped most off with a fairing batten (actually it was a piece of sail batten from our old fashioned monohull, I can't believe anyone still sails with a single hull!)  The result was the putty filled in the low areas between the remaining fairing stripes we discussed last post.  And the higher areas were left pretty much bare.  Once this cures we should be able to sand it smooth with minimal effort.  Assuming we didn't miss any low spots, we would then be able to move on to glass work.  However, I am still waffling between glassing or installing the access port plates first.  Stay tuned to see how this conundrum is resolved!

Fairing as the next olympic sport

 I spent the past couple days sanding off all of the fairing putty stripes we discussed in the previous post.  All the rumors about fairing a boat are true - it is tiring and makes me feel like I'm going to pass out.  Of course most physical activity makes me feel this way, that's why I sail!  Actually, the sanding went fairly  quickly (pardon the pun), it just felt like it would take forever.  In this shot, you will see that we rotated the hull onto its side to make the process a little easier.  I highly recommend cradles with interchangeable forms, it really made life easy here.  You might also notice that I am standing on the strongback to get better leverage while sanding.  We thought a lot about either clearing out one side of the boat house, or removing the strongback, so we could put the hull at floor level.  But in the end I found this worked okay.  Most of the time I can comfortably stand on the floor and sand, but sometimes it was useful to get a little higher.  And so far I haven't slipped off or broken any important parts of me.

 Here is an excellent picture of me in mid stroke.  Notice the fine form, arms fully extended, eyes on the destination, balding spot in full view!  More importantly, notice that I am in full battle gear with respirator and 100% dust cartridges, tyvek suit, and gloves (with nitrile gloves underneath).  This activity makes a lot of dust, and I really don't want my lungs full of this epoxy/microballoon dust.  And 8 hours of sanding with a long board tends to tear up your hands, so the gloves are a necessity.  I am using 3M marine fairing boards (this one is the rigid version) and sand paper.  They are a little shorter than recommended at only 30".  But they worked quite well and I didn't have to spend any time building a board.

 After I finished sanding the entire surface, we removed the forms in the cradles and set the hull keel-side up so I could round over the keel.  Hopefully this will be the only time we ever see these hulls in this orientation!  It took about a day to sand the entire hull, which is less time than I expected.  I expect it will take a week for my arms, back, and shoulders to recover.  If you notice the piece of pvc pipe sitting on the keel, it is my reference for the radius of the keel.

Here is a close up view of the hull after sanding the stripes off.  It's hard to capture the fairness of the hull in a photo, so trust me when I state that this hull is pretty darn fair.  There are a few spots that are a little low, and the high spots were sanded flush.  The highest remaining stripes are only about 1/32", and most of the stripes are completely gone.  Although tiring and quite the workout, I found this fairing process very satisfying.  Not only did I get a great upper body cardio workout, the hull looks like it was built in a mold.

Next we will fill in the low areas with a thin veneer of fairing putty and sand again.  Assuming that takes care of the initial fairing, we will then move on to laminating the exterior.