Category: Boatbuilding methods

Once the inner layer was fitted and glued, it was time to start fitting the outer layer.  These are 1/2″ thick mahogany planks that average about 5-1/2″ wide, though they are considerably wider forward.  This is the cool stuff.  We rough-cut the blanks and steamed them to the curve of the hull awhile back.  See New Bottom Planks and Using the Boat as a Form.  Now it’s time to fine-tune these pieces and trim them to their final shape–a process called “fitting”.   That process–getting  a tight, leak proof seam between two planks that run the length of the boat–involves about 3 parts science, 1 part skill and 6 parts patience.  I use the “Router Method” that I described here in Replacing Topsides Planks.  It’s a little more cumbersome on the bottom because the clamping devices you have to use cannot be positioned so that you can simply glide right past them with your router.  You have to start and stop, then connect the line later on the workbench.  But it works tolerably well.

The first plank to be fit is the Garboard.  This is the plank next to the keel.  On our boat, the garboard is a single plank, without a splice, that runs the length of the boat.  I simply clamped it in place next to the keel rabbet, and scribed a line along it that matched the keel rabbet, then cut it to fit.  Once satisfied with the fit of the edge in the keel rabbet, I used a batten to mark a fair line on the other edge that the next plank will be fit to.  Then I trimmed to the line, making the first cut with my trusy jigsaw, and trimmed to the line with a bench plane.  I then marked out where all the screws would be placed on the plank, clamped it back in place on the boat and drilled holes for a few locator screws to hold the plank in its exact position so that the next plank could be fit against it’s edge.  These locator screws also serve as indispensable guides when you’re glueing the plank on to get the plank back in exactly the same place you had it when you fit it.

With the garboard in position, the next blank, for plank 2PF (that’s Second plank from the keel, Port side, Forward) is clamped about 5/16″ away from the edge of the garboard, and using the edge of the garboard as a guide, the router cuts an exact fit for the edge, reproducing the bevel angle as well.  Then using a batten, you mark a fair line on the other edge of the plank, cut it with your jigsaw, tune it with the hand plane, fasten it in place and move on to the next one.  Wash, rinse, repeat.

There are five strakes to the side, 2 planks (forward and aft) to each strake except the garboard and strake no. 5, each of which consist of a single plank.  That’s 16 planks total.  It’s a great day when you fit that final plank.  It’s an even greater day when you have them all glued down, but that’s a story for another day.

 

 

The bottom of the boat is made up of two plies or layers.  The inner was originally 3/32″ thick by 6 to 8-inch strips, followed by a layer of canvas impregnated with boatyard bedding compound, followed by 1/2″ longitudinal mahogany planks.  This ended up being a 5/8″ thick bottom that did not need to soak up water and swell to a tight, leak-proof fit, like traditional wooden boats do.

We’re replacing the inner ply with 1/8″ marine plywood, then bedding the 1/2″ mahogany planks in epoxy, thereby eliminating the need for the canvas layer which would dry out in about 3-5 years anyway and start leaking.  Our new bottom should have a life of about 30 years or longer if properly cared-for.

So the first step in that process is to fit the plywood to the bottom frame.  Starting at the aft end, we lay an 8 foot piece up and cut it to the outside of the framework.  As we get further forward, we’ll start laying in 6″ wide strips at a 45° angle to the keel to fit the curve of the forward bottom.

 

 

 

The edges of the forward strips are held adjacent to each other with the aid of the intermediate frames which we steam-bent to conform to the curve of the hull some time ago in Using the Boat as a Form.

 

 

 

After fitting, take it all off, seal the inner face and edges with CPES (Clear Penetrating Epoxy Sealer), and glue it in place with epoxy.  I use 5200 instead of epoxy along the keel for its better elongation properties.  All of this is held in place with monel (look it up–it’s a very corrosion-resistant metal) staples.

 

I wanted to replace the first topsides plank on this boat for a couple of reasons.  The boat was wrecked by a previous owner, resulting in partial replacement of the 1st topsides plank on the port side.  I had to take this first plank off the boat to replace the chine anyway.  So it was a good opportunity to go back with new wood.  I didn’t want to replace one side and not the other.  While I was at it, I had long enough planks to do it without a splice–one long beautiful plank instead of a fore and aft with a butt splice–how nice!

The method I use for fitting planks employs the use of a router with a guide riding along the plank edge I’m fitting to.  It was first published in WoodenBoat magazine years ago.  I didn’t invent it.  But it’s a great time-saver and with this method it’s always easier to replace old planks than it is to try to save them.  Plus, you’ve got new wood!

The first step is to fit the forward or “hood” end of the plank to the stem rabbet.  You do this by clamping it in place as close to the final position as possible, and scribe your line on it from the stem rabbet.  Then cut to the line with your saw and shave to a tight fit with your block plane.

Once that is done, I clamp the blank back on the boat with a 5/16″ gap between the plank edge I’m fitting to, and the new plank.  Then route this new edge, following the existing plank edge with your router.  This cuts a perfect match with the correct bevel.  It’s not quite as simple as these two sentences imply, but it’s much quicker than the old spile-cut-plane to the line-on and off the boat-technique.  Although if you’re inclined to slip with the router, this method is not very forgiving.  One wrong move and zip!  You’ve ruined a plank.

You can wait until the bottom is installed to drill the shaft hole and the rudder-post hole in the keel and line everything up.  But why not do it now, before the keel is permanently installed?  It is so much easier when you can bolt everything on to fit it without having to hop in and out of the boat 50 times.  OK, 50 times might be a bit of an exaggeration even for klutz like me, but it does take a few tries to make sure everything fits properly.  So I do it with the keel sitting off the boat so I can reach around all the pieces while I’m standing there.

You’ll recall we discussed Mounting the Strut a while back.   With that job done, you install the strut temporarily and use it as a guide to drill the shaft hole.  This is made easier by asking your shaft fabricator to make you a nice temporary bushing that will fit inside the cutlass bearing in the strut and guide your drill bit at the proper angle.  I use a drill bit extension and a 1-1/4″ forstner bit since the shaft has a 1″ diameter.

Since this hole is at such a shallow angle to the keel (19°) I clamp a block at the point where the bit enters and exits the keel to make sure a clean entry and exit hole.  Then it’s just a matter of taking it slow and clearing the hole of sawdust often.  Don’t push too hard as you might cause the bit to drift off-line.  You might as well go slow and enjoy it since it took so long to set this up!

Then flip it over and bore another, larger partial hole to create the pocket for the shaft log.

 

 

 

 

 

 

 

 

And then mount everything to make sure it lines up.  You’ll want to mount the rudder, strut, shaft, and the shaft log.  Of course there will be the inevitable cleanup with a wood rasp and round file, chisel, gouge–whatever your tool of choice is.

Once you’re satisfied, seal this hole well with 2-3 coats of epoxy.  This would be a great place for water to migrate into your keel and allow the growth of rot spore.

No, the transom framing isn’t growing porcupine quills.  Look closer–they’re toothpicks.  Bear with me.  There’s a method to my madness.

If it seems like I’m procrastinating on planking the bottom, let me explain myself.  There’s really a lot to do before you cover up those frames that you need to clamp to.  And all those places that are so easy to get to when you can reach through the bottom will take a lot longer to deal with when that ready access is denied by a new bullet-proof bottom.  So get those frames and the underside of the deck painted while it’s easy!

Working with the transom is one of those things that’s easier done when you can reach through the bottom of the boat, so that’s what I’m working on now.  Of course the bottom plank of the transom was removed long ago so we could replace the lower transom bow.  I didn’t want to remover the other two planks until it was time to replace them because they help to hold the shape of the boat.  With the new bottom frames coated and now permanently glued in place, the boat is a whole lot stiffer and less likely to be pulled out of shape.  So let’s get cracking!

First, why replace the transom planks at all?  Well, there’s a hole in the top plank that I can’t explain and can’t think of a good use for.  And the fact that the middle plank has been patched.  Add to that the prospect of matching stain on one new plank to two old ones, and it becomes easier to just replace all three planks.

So, removal begins with taking all the bungs out to access the screw heads and hoping most of the screws don’t break when I try to take them out.  In this case, I was pretty lucky (whew–not too much wailing and gnashing of teeth!).

 

 

Did you know that when a wood screw is removed from its hole, it loses 85% of its holding power.  The screw threads cut into the wood fibers when you put it in the first time.  You simply can’t put it back in an old screw hole and expect it to hold nearly as well as it did the first time.  So I fill all the screw holes in the framework pieces that won’t be replaced.  I do this with epoxy and toothpicks, cutting them off flush after the epoxy cures.  Now I don’t have to worry about lining up or missing old screw holes, and it holds together much better.

Next step is to coat the framework with Smith’s CPES–that’s Clear Penetrating Epoxy Sealant.  It’s epoxy that’s been thinned to almost the consistency of water so it will soak in to the wood.  Really good stuff!  So good, in fact, that you have to wear a respirator with charcoal filters when you’re using it.  It’s best to plan this for the end of your day and just leave the shop afterwards.  This stuff is really strong-smelling.

Then time to cut out the new planks and steam bend them to the curve of the transom.  But we’ll save that for another day.

Well, it’s time to start putting holes in the boat.  Now this is a subject any boatbuilder approaches with at least some degree of respect, if not downright fear and trepidation.  After all, you’re doing all this work to create something that floats, right?  But boats have to have holes in them to function.  You have to get water to the engine somehow.  The propeller shaft has to get from the engine inside the boat to the propeller outside the boat.  You have to vent the fuel tank.  You have to have a way to pump bilge water out.  The list goes on.

In this case, we need to mount the strut, which supports the propeller shaft, onto the keel.  We’ll then use the strut as a guide to bore a bigger hole–the one for the propeller shaft.  To make sure we get this right, a lot of attention gets paid to lining things up.  I install a new cutlass bearing in the strut and pass the old shaft through it.

Then line this up with the center-line on the keel, and with the center-line string suspended over the boat.  Clamp it in place, and drill.

It’s not time to install them yet–that won’t come until after the inner layer of 1/8″ marine plywood is already fitted and installed.  But we need to bend the outer planks to the shape of the hull while we can still get to the frames to use them to clamp the planks to.  So now’s the time.  Boatbuilding, as with many other endeavors, is often not done in a straight line.  You do things when you can, when you have the extra help, when you need to.

The first step is to sort through the milled lumber and pick the nicest grain for parts that will show.  We allocated the pretty stuff to topsides planks, transom planks and ceiling.  That leaves the not-so-pretty stuff for the bottom, which will be covered with paint.

We’ll start with the garboard (that’s the plank that lies next to the keel, and incidentally, where a lot of leaky bottoms start) and work out way up toward the chine.

Having allocated our lumber, the next step is to cut out what I call the “blanks”.  I used the old planks (never throw anything away until the project is finished) as patterns to get the general shape of the new planks and cut them out big on with a jigsaw.

Now that last sentence could be a whole blog topic in itself.  I realize as I write this that there’s a lot of “how-to” that gets skipped over.  How big? Bigger on one edge than another? Is there one brand of jigsaw that’s better than another?  After all, the right tool really does make all the difference.  What about grain orientation?  Is there a problem with avoiding sapwood like when you’re cutting white oak?

I know there’s a lot that I gloss over here.  If you’re interested, you can always comment or ask a question.  I promise to answer.  And I promise to tell you if I don’t know.

Back to the main topic, I cut them out two at a time–one for each side of the boat, tracing around the old plank, leaving it 1/2″ big on the bottom and leaving about 3 to 6 inches on the aft end.  This way, if I make a mistake when fitting (which comes much later), I can slide the plank forward and re-do.

 

 

 

Then I presoak these mahogany planks for at least 24 hours before steaming them.  Mahogany, being less dense than white oak, needs less presoaking time.  I would soak white oak for a week or two before steaming.  Then it’s time to steam it.  In this case, since the planks are 1/2 inch thick, they’ll be steamed for at least 30 minutes.

 

 

 

 

 

 

Finally, pull them out of the steamer and quickly clamp them to the frames of the boat.  I only steam the forward planks.  The aft ones are pretty straight, and won’t be stressed by attaching them to the boat without steaming.  Having the forward ones curved to the shape of the hull greatly eases the task of fitting them, which is a topic for another day.

We’ve already discussed cutting the rabbet on the stem and gripe here.  You can imagine that cutting this groove along the length of both sides of the keel with a hammer and chisel is a daunting task indeed.  Especially in a tough wood like white oak.  The procedure is complicated by the fact that the bevel changes along the length of the boat.  Just look at the way the bottom comes into the keel.

But thanks to Don Danenberg, there’s a better way.  He  devised a method of setting up a router track along the length of the keel and using the frames of the boat to get the right bevel.  It’s really clever, and saves a good bit of shop time, but requires that the frames all be fair before you start routing.

First, you steam bend a pine plank to lay alongside the keel.

Then screw it to the frames, and screw a 3/4″ x 3/4″ guide to the pine plank that your router will ride against.  The router sits on the plank and the keel, and cuts your rabbet.  It takes several passes because white oak is tough wood.  But it gets the job done accurately and in much less time than it would take to do it with a hammer and chisel.

 

I had some help from expert boatbuilder Mark Neely setting up this operation.  Thanks, Mark!

 

All this hard work getting the frames and other structural pieces into shape is finally paying off.  We can use this structural framework as a form when making and bending new pieces to fit the boat.  A good example is the Intermediate Frames.

Intermediate frames are the sticks that go between the main and auxiliary frames to provide another fastening point for the bottom planks.  We made these out of 5/8″ x 1″ pieces of white oak.  We steamed them for about an hour–probably could have gone a bit longer–they were hard to bend!  Then, as you can see, we just bent them under a batten clamped down the center of the frames to give them the curve they’ll need in the area of the boat they’ll be used.  Keep in mind that you’re seeing parts for both the port and starboard sides of the bottom here, clamped on place on the starboard side only.  But since the bottom is symmetrical, we can use one side for both.

For these small forward pieces it was easier to just make a simple form on the bench.

The Stem and Gripe together make the Forefoot of the boat.  This is the curved part of the bottom that provides the transition from the stem to the keel.  It needs to be a formidable piece of the boat because it is the piece that parts the water as the boat makes its way.  It takes considerable pounding, and in an older boat, almost always has some rot in it.  That means it’s going to have to be replaced.

Since we have the plans, we could loft the boat and then take off the curves to make a new stem/gripe.  But we have a pretty good pattern (albeit with a little rot here and there) in the old one.  Using a sheet of glass and some clear plastic from the art store, we can draw out a pattern and transfer that to properly dimensioned white oak to make a new one that’s better than the old–better because it’s made of rot-resistant white oak.

So the first step is to lay a piece of 1/4″ glass over the old part and trace its lines onto a piece of clear mylar.  Of course you want to get as much information as you can on this tracing, including bolt locations, bootstripe, etc.  And make sure you are looking straight down on the part when tracing to avoid any parallax error.

Then take your new pattern and transfer the lines to your new wood.  You do this by tracing over the new mylar pattern with a “pounce wheel”, which you also get at your friendly art supply store.  You can see in our example that we made sure to avoid any sapwood in the new pieces.  Sapwood is much lighter in color and contains dried sap and sugars.  Including sapwood in your boat is like a flashing neon sign for rot spore–bad news if you want to keep your boat rot free.

Once the pieces were cut on the bandsaw, it took a little time to fit the joint between the stem and the gripe.  You need a good, solid joint here that, once slathered with bedding compound, will not allow ingress of any water.

Once we got that joint in good shape, the stem and gripe blanks were bolted together and fit to the breasthook.  Then it was time to look at the curve of the whole assembly and make sure it would be fair with the keel joint.  As you can see, we had to glue in a shim or two, but there’s no shame in that.

 

 

Finally it was time to carve the rabbet.  That’s the groove that runs lengthwise along the piece for the bottom planks to rest in.  That’s really a topic all in itself, but we’ll show it here.  To make a long story short, you use the lines you’ve traced on to your blank from the old stem/gripe assembly.  Using those lines, you have at it with your chisel and carve out the rabbet.  It helps to have a test stick, called a “fid”, that is the same thickness your planking will be to test how it fits in the groove as you carve it.  With a tough wood like white oak, you have to pause a few times to sharpen the chisel.  You can definitely tell the difference a sharp tool makes here.

Then clean it up with a plane, sander, Fein multimaster, whatever works.  You’re done!