Author Archives: Ben Mitchell

And now for something completely different…

July 1, 2013 8:48 pm ⋅

After weeks – months, really – of messing about with framing, it’s time to move on.  Today we begin planking the hull.

“Planking” is boat-speak for “covering the frame with a wooden skin,” and the process we’re using is called cold molding.  Many boats can be built by bending large pieces of plywood into the finished shape of the hull.  If you’ve ever heard of a “stitch and glue” boat, that’d be a prime example of such a boat.  For this to work, the hull can’t have compound curves because a single piece can only be bent into a conical section.  Our boat has looooots of compound curves, and so we can’t just bend a single piece of sheet lumber and call it good.  Instead, we take those 4″ wide strips and start laying them in next to each other.  To allow them to fit the curve, each one is shaped by hand, shaving away some of the edge so it will fit against the prior plank when it’s bent to the hull.  I can’t really photograph this process for you without a third hand, so you’ll have to use your imagination, but suffice it to say that it takes about 2-3 minutes to fit the edges together for each successive plank.

Then you take a bunch more time to apply adhesive and staple the plank in place.  The staples are temporary, and are shot through a piece of plastic or nylon that can be used to pull the staple back out after the epoxy has cured.

Each side gets three layers of WRC for a total thickness of about 1/2″.  Today, we were able to get the first layer on the starboard side.

This is a lot of work.  And each of those staples that goes in with the pull of a trigger is going to take a lot more work to remove.  Sigh…  These pretty curves create an awful lot of work.  Because the curves are pretty tortured in some places we need a lot of force to hold the planks in place while the epoxy cures.  I’m thinking it’ll take a couple of hours to remove all those damned staples.  We’ll find out tomorrow.

-Ben

Posted in: Planking

Western Red Cedar

July 1, 2013 6:58 pm ⋅

So the original specification was that the bottom and sides of the hull be planked with strips of 1/4″ Okoume marine plywood.  There were a couple of issues with this.  First, it would have been really inefficient from a material perspective.  The bulk of the strips need to be about 5′ long which, given that plywood comes in 4’x8′ sheets, means you’d be throwing away a huge amount of material.  And this isn’t cheap stuff.  Each sheet is about $100 and we would need something like 16 plank just the sides of the boat.  The second issue is that there are some really tight bends in this thing, and torquing 1/4″ plywood into them would have been a very difficult task.

After a bit of discussion with Timm, I decided instead to plank the sides with three layers of 0.166″ thick, 4″ wide strips of western red cedar.  Unfortunately, you can’t just go buy 4″x0.166″ WRC.  What you can buy is rough sawn 8/4 lumber in 10′ and 12′ lengths.  And that’s what we did. Then came the amusing step of converting the big lumber into small lumber.

To do that, we first surfaced the rough lumber and ripped the 8″ wide planks into 4″ wide planks.  Here’s a shot of the surfacing process.  I’ve got a Rojek 12″ jointer-planer that I picked up on Craigslist.  It’s proven to be a great machine.

Then we resawed the 4″ wide planks into strips known as veneers that were about 0.20″ thick.  Here’s the resaw operation.  It’s not hard work, but it’s mind-numbingly repetetive.

Finally, all the veneers went back through the planer to get them to a finished thickness of 0.166″, leaving us with a stack of veneers ready to be applied to the hull.  I don’t think we have quite enough to do the hull yet, but we decided not to mill anymore until we got a sense for how much it was going to take.

This is expensive wood – you’re looking at nearly $1000 worth of WRC in that stack – but it’s really the best approach to this part of the process.  It’s also quite likely that using WRC saves money since we’re throwing less away.  We shall see.  For the time being, we’ve got more than enough to start planking the hull!

-Ben

Posted in: Planking

Fairly Nervewracking

July 1, 2013 6:32 pm ⋅

Now that the longitudinal members are done, the frame is pretty much complete.  But it’s not finished just yet.  The outside edges of each and every piece of framing have to be shaped so that the skeleton of the hull – the frame – is “fair.”  That’s boat-speak for “smooth.”  This is essential so that when you bend the skin planking over the frames you get nice smooth curves instead of something full of lumps and flat spots.  It’s also critical that you have wide contact points so that there’s a place on the frame to glue to.  If you only contacted the framing at the very edges, you’d have a very poor bond indeed.

Allow me to introduce you to a tool about which I’m somewhat ambivalent.  It’s exceptionally useful for the task, but it’s truly been my misery whip over the past days.  I present, the low angle block plane:

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We used this, and sanders, draw knives, and other implements of destruction, to shave away huge amounts of the framing that we’d painstakingly assembled.  The next photo shows some shavings generated around the bow.  That’s the tip of a big iceberg.  I think we filled two garbage cans with little ribbons of douglas fir.
I don’t have a final-final image for you, though realistically it’s hard to capture the result of many hours of back breaking work in a picture.  It mostly looks the same as it did before.  But if you look below you’ll see that the sheer clamp is starting to be tapered to a knife-edge at it’s perimeter.  We’ve also shaved a ton of material away from the side stringers to get them fair.
This whole process is a bit nervewracking in that it’s easy to screw up, and hard to know when it’s “done.”  Unless you measure constantly you can easily remove more material than you wanted to.  This happened to me in a couple of places including at the very tip of the bow and near the break in the starboard sheer.  I had to glue some additional material in and then shave it all back down again.
You can always make it a little better, and knowing when to stop is clearly something you get a feel for after your 3rd boat.  I am on my first, so I’m nervous.  But I think we’re done, which means we’re ready to start planking.  Yee haw!
-Ben
Posted in: Framing

Forward Sheer Clamps

June 28, 2013 8:46 pm ⋅

The last of the longitudinal members are now installed!  These are the forward sheer clamps, and they define the line at the outside of the top of the hull in the forward part of the boat.  As the Kitty Hawk 18 is a Carolina-style hull, it has a broken sheer, and a very flared bow.  The sheer line on a boat is – simply put – the line that the top of the hull makes when the boat is viewed from the side.  “Broken sheer” means that that there is a sharply divided sheer line on this hull.  In the aft sections, the sheer line is lower.  In the forward sections it’s higher.  And there is pronounced transition between these sections.  It’s also the case that the forward sheer on this boat flares widely relative to the aft.

Because the hull essentially “ends” at the sheer line, you need a stout member similar to the chine log which anchors the side of the hull and provides an attachment point for the topsides of the boat.  This is called a sheer clamp.  The aft sheer clamps went in with the side stringers and were pretty simple.  I didn’t bother discussing that.  The forward ones are trickier because of the complex curves.

We decided to laminate them from eight strips of 1″ tall x 3/8″ wide doug fir. They didn’t need too many clamps – relatively speaking – so we were able to lay them both up the same day.  Here they are after being installed.

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The intersection of the forward sheer clamp and the aft one is complicated.  Here’s the junction just after the clamps came off.  The outer sections of the forward one will get shaved away during the fairing process to produce a smooth junction.

_MG_3333

That’s it for the framing members!  Well almost, we still have to put on the third layer of the transom, but that’s pretty trivial.  The hard work of laminating these longitudinal members into position is done.  Next up: Fairing.
Stay tuned.
-Ben
Posted in: Framing

Tough Stringers

June 27, 2013 9:11 pm ⋅

First off, I apologize for the delay in providing another update.  The Florida trip got me off my usual routine. And now, on to the update…

The last of the stringers – the topmost in the bow – is tough.  It bends a lot in two different directions, both vertically and horizontally.  I tried bending a pair of 3/8″ strips in there and they broke.  Too much “hard way” bending.  So we had to do something else.  After mulling a couple of options, what we came up with was to stack six 3/8″x 3/4″ strips vertically rather than two 1-1/2″ x 3/4″ strips horizontally.  From a bending perspective, this worked great.  From an assembly perspective – total nightmare.

Anyway, we first milled a bunch of strips:

And then we laminated the starboard stringer.  Realistically this is where we made our first “ugly” error in the boat.  The strips slipped on us during clamping and we couldn’t get the parts lined back up, so we decided to live with it.  The ugliness will be completely buried later and invisible, but it’s annoying. Here’s a photo of it under clamp.  In the right hand edge of the picture, you can see that it looks more or less like a composite, rectangular board.  Toward the left side, it’s slipped so it’s more of a stair-step.

On the upside, we learned some lessons on this first one, and by the time we got to the port side we did a much better job.  Next up, we have to install the last of the longitudinal members – the forward sheer clamps – and then fair all of the framing.

Exciting stuff!

-Ben

Posted in: Framing

Florida Keys

June 20, 2013 2:05 pm ⋅

My friend Jeff is getting married in Boca Raton this weekend, and my birthday present from my rockstar girlfriend was to add a few days to the trip and come down to the keys to do some fishing.  I figure it probably goes without saying given that I’m building a fishing boat, but I rather enjoy chasing fish.  And there’s pretty much no gamefish that compares to the tarpon, especially on a fly.

We arrived Tuesday evening and drove from the Ft. Lauderdale airport down to Islamorada, where we checked into the Cheeca Lodge.  The resort is lovely.  Yesterday and today we fished with Captain Jeff Bloodworth who worked hard to find fish under tough circumstances.

Wednesday we hooked up with, leadered and released a nice tarpon on the fly.  Probably a 70# fish, but a really strong fish for its size.  Great fight.  Here’s a shot of me pulling on it.

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Today Carla caught a nice little shark on a live crab.

Tomorrow we’re going to laze about a bit before heading up to the wedding.  It’s been a great couple of days.  Back at the boat building on Monday.  Stay tuned for more updates.

 

 

Posted in: Fishing