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Penobscot 17 rebuild

penobscot lapstrake rebuild

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  #1 Michel Goudeseune

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Posted 07 March 2012 - 11:50 PM

This thread will document the repair and rebuilding of a Penoscot 17 sailboat, designed by Arch Davis.


Today's weather was beautiful, just what I needed for moving the Penobscot 17 from my tent into the workshop.

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The door lifts upward with a winch. I have barely enough room to squeak the boat through the doorway, so I didn't want the doors opening sideways.

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  #2 Michel Goudeseune

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Posted 07 March 2012 - 11:55 PM

With the boat parked outside briefly, I raised the masts. I was hoping to raise the sails and take some photos, but I didn't want that much excitement -- winds were strong and gusty :) .

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Next we backed the trailer into the workshop, and used the gantry crane to lift the boat off the trailer.

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  #3 Michel Goudeseune

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Posted 08 March 2012 - 12:01 AM

Next up was turning the boat upside-down to start work on the hull. Again, the gantry crane worked like charm.

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  #4 Michel Goudeseune

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Posted 08 March 2012 - 12:07 AM

I scraped the bottom of the hull to remove the worst of the loose paint, with the boat sitting on blocks. That got real old real quick :). The crane was used to lift the boat onto three sawhorses. Added bonus, it's easier to work on the hull overhead, than it is leaning over into the hull (when it's right-side-up).

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Among the tools in use so far: carbide scraper, several knives, 1" chisel, impact driver, deadblow hammer, renovator's bar. Oh, and the ubiquitous safety glasses, which I'm always wearing in the workshop.

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  #5 Michel Goudeseune

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Posted 08 March 2012 - 10:16 PM

Today I removed the six lengthwise seats. Work started with a screwdriver and impact driver, and rapidly progressed to a hammer and chisel. The cleats supporting the seats were softwood, and split quite easily :(.

Don't mind the inverted sawhorses -- I haven't moved to Australia. I just rotated the photos to make them easier to see. The boat's still upside-down.

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I'm also in the process of removing the deadwood, which is loose. Much of the epoxy between the keel and deadwood came out quite easily. The majority of the screws holding it in place were stainless steel. Except, of course, the last two in the stern flotation chamber, which are a bear to get at. They're plated steel, so they rusted. The aft-most one has a hex head, which has sunk partially into the keel, so I can't get a socket onto it. The other one, for extra flavour, has a square head :angry:.

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Fortunately, plated steel screws have one redeeming quality: they're ferrous, so they attract magnets. A stack of rare-earth magnets worked like a charm to locate them, so I can surgically remove them from outside, without turning the entire deadwood into swiss cheese.

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  #6 ChrisObee

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Posted 09 March 2012 - 10:29 AM

Its a cool boat. Very pretty. I envy your gantry crane.

  #7 Michel Goudeseune

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Posted 09 March 2012 - 03:49 PM

Thanks, Chris.

The crane was a DIY project too. I bought the design from http://www.synthx.com , and welded it up myself. It's come in very handy for many projects!

In boat progress, I just ordered replacement plywood for the deck, seats, and parts of most of the bulkheads. That should all be here in a week or two. In choosing between "big box crappy plywood" and marine plywood, I decided to split the difference and go with Baltic Birch. Epoxy-coated and painted, it'll be a huge improvement from some of the uncoated (!) marine ply I just removed.

The added incentive for Baltic Birch is that I can get it locally (5-minute drive) vs. half an hour (nearest big box store) or 3 hours (Noah's, in Toronto).

  #8 Michel Goudeseune

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Posted 12 March 2012 - 01:23 PM

The outside of the hull was sanded down with a random orbital sander, removing most of the loose paint. I also removed the badges at the bow and stern. Ironically, they were installed more securely than the seats :(. The deadwood was also removed, as described previously.

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A closeup of the centreboard case. It appears the planking is loose from the case, which is why I'll be removing the case and reinstalling it with fresh wood.

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How I removed the athwartship seats (front seat pictured). Using a jigsaw, I removed the middle section of the seat. A renovator's bar (fancy crowbar with a large bearing surface) was used to break the bond with the bulkhead. Then I clamped a block of wood to the edge, and used a hammer to knock it loose from the stringers.

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In this photo you can see why it was easy to remove. The blobs of epoxy on the lower stringer (1x1) are smooth -- they made no contact with the seat whatsoever. There was also little contact with the 1x2 stringer above.

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  #9 Michel Goudeseune

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Posted 12 March 2012 - 01:30 PM

Why to avoid drilling holes in your boat (even in the deck). The prior owner drilled two 1" holes in the aft flotation chamber to lead the wires for the electric trolling motor. In this photo, you can see a discoloured triangle above each stringer, where water accumulated before spilling over to the next stringer.

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Cleanup of the interior progressed rapidly this weekend, when I moved up to using an angle grinder for stripping paint B). This made it much easier to see the condition of the stringers. It also covered my entire workshop in dust!

At the bow, the uppermost stringer fell apart when I touched it -- surprising, given its location.

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  #10 Michel Goudeseune

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Posted 12 March 2012 - 01:44 PM

I have two questions relating to the masts.

The builder added this assembly of 2x2 lumber to the bow, presumably to help support the main mast. The distance from the mast step to the deck is about 14". This framework extends that height to 21". I'm wondering if it's necessary? Also, if it is, would I be better served by installing the new deck at the level of the sheer, and extending the bulkhead upwards to meet it?

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Next, the two mast steps are installed with a mortise on the step, and a tenon on the mast heel. I don't have the plans, but this strikes me as a bit odd, as it would allow water to sit in the mortise. Should I change this around to have a mortise in the mast, and a tenon at the step? Alternatively, a drain hole in the base of the mast step would allow any water to drain into the bilge. Thoughts?

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  #11 Michel Goudeseune

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Posted 15 March 2012 - 09:52 PM

Before removing any of the bulkheads, I took offset measurements of the middle bulkheads. I could have used the plans, but I wanted the actual offsets of this boat, not the hypothetical perfect build :).

I placed an aluminum beam in the corner of the knee at bulkhead #2 and #6. These aren't the names used in the plans, but they serve my purpose of identifying them in the boat. #1 is at the bow flotation chamber, and they increase in number going aft. At each bulkhead, I took photos of a tape measure placed in the corner. What I didn't picture here is the other 200 photos I took of other measurements.

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  #12 Michel Goudeseune

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Posted 15 March 2012 - 10:00 PM

With all the measurements taken, I moved on with disassembly. Half of bulkhead 4 (which is bisected by the centreboard trunk) is shown here. I made one cut at the knee, as the direction of the stringers prevents simple removal of an entire bulkhead. You can also see the state of the bulkhead where the end grain was exposed to standing water. This was marine ply!

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The first half of the centreboard trunk was also removed. The discolouration shows the level to which water was standing inside the hull. The epoxy coating on the inside face of the wood is gone -- from water migrating through the wood.

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With the centreboard trunk removed, the remains of the keel at bulkhead 2 is visible. Probed with a chisel, this wood offered as much resistance as a slice of bread. Yikes.

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  #13 Michel Goudeseune

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Posted 15 March 2012 - 10:03 PM

Nice weather offered an opportunity to sand down the deadwood outside. The warning pylon is to avoid impaling myself on the pointy end. I have a number of these 9" pylons that I use in my workshop around temporary hazards.

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  #14 Michel Goudeseune

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Posted 15 March 2012 - 10:11 PM

The quarter knees were not secure -- not a good thing for a structural part of the vessel. I did not fancy removing the gunwale to access the mounting screws, as the gunwale is securely glued. I opted for a metal-cutting blade in my jigsaw, and did a cut along the joint between the inwale and the knee, cutting straight through the stainless screws.

The knee, held in its usual location:

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The aft face of the knee: shiny epoxy. There was no bond with the transom.

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The mounting face on the inwale. The abraded parts are where the jigsaw cut through the epoxy. The dirty parts are where there was no bond.

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The mounting face on the transom. This appears to be weathered varnish. The one screw was the only connection between the knee and the transom.

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  #15 Michel Goudeseune

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Posted 15 March 2012 - 10:23 PM

With the centreboard trunk out, next up was bulkhead 3, which needs to be reinstalled before the new centreboard trunk. The old one came out comically easy:

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I then carved out the worst of the keel rot, and set about replacing it with new wood, which will be further glassed in place with biax.

The challenge was to reach the bottom of the hull, without turning it over. With two bulkheads (and a bunch of stringers) missing right now, I did not want to turn over the boat. The solution was a couple of axle stands under the cradle :).

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A length of rope around the lower casters works admirably as a wheel chock:

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New wood, being held in place with shop weights while I trace the outline from below:

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Two blocks of wood span the opening, held by a C clamp to keep the two halves of the planking aligned during this process:

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The wood was shaped using my various woodworking tools (mitre saw, handheld planer, etc). I have a large-format CNC router, but sometimes it's quicker to just do it by hand -- especially when trying to fit to an existing, irregular part.

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Here is the new piece of the keel glued and screwed in place. The screws are necessary to clamp it, as I don't have a C clamp big enough to fit around the boat :rolleyes: . They will come out after the glue dries, and the holes will be plugged. The red marks are for alignment.

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  #16 Scott Dunsworth

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Posted 19 March 2012 - 07:36 AM

I built a Penobscot 14 ten years ago, it took me 18 months to complete. Do you have any clue as to why the original builder went to all that work and didn't buy three gallons of epoxy to coat his build? I talked to the designer about not encapsulating mine. I was new to boat building then. I told him that it would be garaged and wiped out after each use. He highly recommended that I not waste my time building the boat uncoated, even with my given usage plans. There are areas of the boat that simply can not be wiped out and even a well kept boat built with these type of materials would sooner or later show the signs of water damage. I can see now after 12 years and 6 boats later how these small boats if all end grain of the all the wood was epoxy coated, finished with high quality finishs and the boat was cared for to a very high standard could last a very long time. BUT most boats never see that level of care especially after the first few years. Just Three gallons of epoxy and a little care would have prevented all this your having to do now.

ROMANS 8:1, BELHAVEN 19, SPINDRIFT 12S, 10N, PENOBSCOT 14,
IN OVER MY HEAD CANDICE 28


  #17 Scott Dunsworth

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Posted 19 March 2012 - 07:52 AM

I have a old small runabout in my barn that is in a little worse condition that I have been wanting to rebuild. It was built with white oak frames and planked with mahogany. Like I said it is no better off, but it was built in the forties. One day I will finish this boat, the outside will be epoxied and glassed. The inside will be sprayed with penetrating epoxy then Many coats of sprayed varnish. This boat will never see rain again after its done.

ROMANS 8:1, BELHAVEN 19, SPINDRIFT 12S, 10N, PENOBSCOT 14,
IN OVER MY HEAD CANDICE 28


  #18 Hirilonde

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Posted 19 March 2012 - 07:54 AM

I don't know the specifics of that boat, how much is conventional construction and how much is modern. But not all boats should be epoxy impregnated. A purely conventionally built (plank on frame, mechanically fastened, no plywood) boat that is kept in salt water will last a lot longer if allowed to pickle, move and breath. But you're right Scott that trailered boats for the most part are much better off epoxied.

Dave Finnegan

1967 Pearson Renegade  "Hirilondë"

Spindrift 9N #521 -  many KudzuCraft SoF kayaks


  #19 Michel Goudeseune

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Posted 19 March 2012 - 03:46 PM

Scott,

Believe me, I've been scratching my head wondering about many of the builder's decisions. I'll give you one example. On page 20, the plans state "To ensure that the stringers do not trap water, it is important to provide limber holes." This was underlined in red by the builder. A diagram is included on the next page, similarly annotated in red by the builder.

Now, how many limber holes do you thing were installed in the stringers? If you guessed zero, you're correct :wacko: . Why did he omit them? I Don't Know.

As I'm starting into the reassembly stage (first epoxy applied this afternoon), I've come up with a directive to guide my decisions. If it's more work to fix this one than to build a new boat from scratch, then I'll not bother. For example, this is why the interior will be completely painted. It would be more work to partially re-plank this vessel to allow a bright finish, than to build a new one.

She'll be a nice boat when I'm done, but "Bristol Condition" is permanently out of reach for this particular vessel.

  #20 Michel Goudeseune

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Posted 20 March 2012 - 08:28 PM

Using the floor jack to lower the cradle back onto its wheels, after removing the temporary screws in the keel repair:

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I coated the inside of the centre section of the hull with S1 Sealer, and then further strengthened both sides of the keel, and various parts of the plywood, with fibreglass. Most of the glass I pre-cut as biaxial, and laid it out on some pink foam before mixing epoxy.

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A self-healing cutting mat and cutting wheel work great on fibreglass, without distorting the weave.

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Here's what it looked like after epoxy coating and fibreglass. I used 10 fl oz of S1 Sealer and 20 fl oz of EAST System epoxy.

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With this stage complete, the boat was lifted onto the trailer again, to spend a few days back in the tent (to help the epoxy cure) while I work on other, paying, projects.

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