Boat in a box - the Shu3

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Chris Johnson
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Re: Boat in a box - the Shu3

Post by Chris Johnson » Wed Apr 16, 2014 5:21 pm

Starting to look like a boat Steve! Looks good!

I don't envy you having to rip 14'+ pieces of narrow stringer stock solo though. Sounds like a lot of potential for some table saw misadventure. (and that's never a good thing!)

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Shu
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Re: Boat in a box - the Shu3

Post by Shu » Thu Apr 17, 2014 12:42 am

Chris,
It was challenging. I was able to set up one upstream and two downstream rollers to support the long wiggly pieces. A "feather" which is a flexible piece that firmly holds the wood against the fence, and a couple of appropriately sized push sticks helped keep everything under control. I did end up boogering up the very tail ends as they were pushed past the blade, but I had extra length to accommodate that.

My dad has a very useful saying that he got from the owner of the boatyard where he first started building boats: "Count your fingers before you start cutting." It's a good way to remind yourself where your fingers are relative to that spinning blade.
Steve Shumaker
USA 1183

Chris Johnson
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Re: Boat in a box - the Shu3

Post by Chris Johnson » Fri Apr 18, 2014 4:30 pm

Sounds like a good system Steve!

Thinking about it a bit more later, a bandsaw would probably be another good method.

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Shu
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Re: Boat in a box - the Shu3

Post by Shu » Mon Apr 21, 2014 4:53 pm

I worked on the stem this weekend. It essentially provides shape to the finished bow, and provides a cleat to glue the hull skin and stem cap. I also fitted stringer 3, and started to fit the plywood doubler for stringer No. 1. No photos of that though.
Attachments
IMG_3136.JPG
Gluing on the starboard stem piece. A couple small nails (on other side) keep it from sliding around while it cures.
IMG_3138.JPG
Adding the port stem piece. The plastic-wrapped cross piece is there to keep the bottom flush with the starboard side. A small nail, visible at the top, holds the top in position.
IMG_3142.JPG
Tracing the offsets onto the stem and connecting the dots
IMG_3147.JPG
Checking the bevel with respect to bulkhead A (out of photo to right). The bevel is good, but the rounded profile is not ideal. Cheers for the gap-filling properties of epoxy!
IMG_3148.JPG
The stem ready for stringers and skin
Steve Shumaker
USA 1183

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Shu
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Re: Boat in a box - the Shu3

Post by Shu » Wed Apr 23, 2014 6:02 pm

The plywood doublers are now fitted. I still need to cut the bevel onto the forward end of stringers No. 4. For now they've been slid aft. I'm using the bigger clamps to put some twist into the forward ends of stringers No. 3, but the total amount of twist required here is too much for the wood. I will need to add a little bit of wood on one side and plane some off on the other.
Attachments
IMG_3152.JPG
With most of the bottom stringers fit, the shape of the bow is starting to show itself
IMG_3155.JPG
This angle demonstrates how little rocker there is
Steve Shumaker
USA 1183

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Re: Boat in a box - the Shu3

Post by Shu » Tue May 06, 2014 4:33 pm

Hawaii was fantastic, and gave me new confidence in the strength and stiffness of this construction method. Despite sailing the Shu2 hard in 20+ knots with heaps of rig tension, and then pitchpoling in 30+ knots, the only thing we broke was a tiller extension. In fact, the only things I've broken in 2+ years are tiller extensions, the daggerboard on a reef, and some torsional crushing on the mast step (see the My New Boat thread for that fix). I'm thinking of selling the Shu2 and replacing it with a composite boat that I can abuse while I concentrate on the Shu3. I really love the boat, but that's the problem; I need a boat to sail that I'm not so attached to, so my efforts (and affections) aren't divided. If you or someone you know wants a completely sorted, fast, gorgeous, and very strong boat, pm me.

Now it's time to get back to building the Shu3. This week I've been gluing the stringers in place, and have worked my way out to one of the third stringers as of this morning. It's amazing how stiff the structure becomes when the epoxy cures. I'm a little behind with the photos, but these photos show the progress as of this past weekend.
Attachments
IMG_3162.JPG
Gluing the plywood doubler to the first stringers. I used an extra piece of stringer stock to evenly distribute the clamp pressure and to maintain fairness.
IMG_3166.JPG
With the first stringers finished, the second stringer is being glued in place. I use a 3/8" rounded stick (about 1/2 the width of a tongue depressor) to fillet all around the glue joint between the stringer and frames. The string and clamp are holding one joint together, since it wanted to open up slightly.
Steve Shumaker
USA 1183

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Shu
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Re: Boat in a box - the Shu3

Post by Shu » Thu May 15, 2014 8:16 pm

All the bottom stringers are now glued in place. Here's the starboard chine log being glued.
Attachments
IMG_3244.JPG
Chine log being glued in place.
Steve Shumaker
USA 1183

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Re: Boat in a box - the Shu3

Post by Shu » Tue May 27, 2014 5:59 pm

I've completed gluing all the stringers in place. In addition to the bottom stringers and the chine log shown above, I now have the following:
1. the stringer that serves as the cleat between the topsides and the floor, and
2. the sheer clamp. This one is glued only to the stem and frame "A", which is the only frame that extends to the sheer. Otherwise, it is screwed to the temporary extensions of each frame. The screws go through the top (now the bottom) of the sheer clamp, so they will be easy to remove once the topside skin is glued on and the boat is turned upright.
3. A little fill in piece at the forward end of stringer 3.

I now need to plane the chine log to accept the bottom skin, sand the correct bevel onto the edge of each frame, and cut the limber holes into each frame. Then I will be ready to start gluing on the bottom skin.
Attachments
IMG_3249.JPG
All the stringers glued in place. This does not show the additional thickness I added to the #3 stringers at the bow knuckle.
IMG_3250.JPG
A slightly different angle. The clamps are holding the floor cleat stringer in place while the epoxy cures.
Steve Shumaker
USA 1183

Pirate
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Re: Boat in a box - the Shu3

Post by Pirate » Fri May 30, 2014 3:10 pm

Shu:

I don't see any limber holes.

Ed Chimney
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Shu
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Re: Boat in a box - the Shu3

Post by Shu » Sat May 31, 2014 12:11 am

Ed,
I've just started with limber holes on the starboard side (since the photo), which now has all the bevels planed and sanded. I was waiting to get the bevels sanded onto the frames, as the edges of the limber holes are just one more thing to catch the sandpaper on. Waiting until the last item before skinning the bottom does make me a bit nervous though. I could always forget!
-Steve
Steve Shumaker
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Shu
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Re: Boat in a box - the Shu3

Post by Shu » Mon Jun 02, 2014 7:27 pm

As I mentioned above, I finished beveling the chine and frames. It ending up being a lot of passes with the plane to bevel the chine, which being a particularly pitchy piece of Port Orford Cedar, smelled wonderful. The shape of the boat looks a lot less clunky with the chine properly beveled. With that done I have cut out the limber holes on the starboard side, and I'm gluing the cleats onto the girder forward of the centerboard box.
Attachments
IMG_3255.JPG
With the chine log and frames beveled, just add 4mm of skin and there's the final shape. Note the bit of extra wood glued onto the front end of stringer 3 and subsequently planed, rasped and sanded to shape at the bow knuckle.
IMG_3261.JPG
A different angle
IMG_3312.JPG
The limber holes are approximately 5/8" wide and 1/2" deep. After rounding the edges a bit, they are sealed with 3 coats of epoxy.
IMG_3310.JPG
Screws through the girder hold the starboard cleats in place while the epoxy cures.
IMG_3316.JPG
With the starboard cleats already glued in place, screws for the port cleats would be really awkward. It's pretty tricky hammering these nails to hold the port cleats in place.
Steve Shumaker
USA 1183

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Re: Boat in a box - the Shu3

Post by Shu » Thu Jun 05, 2014 8:45 pm

Well, my plan to hold the port cleat in place with nails and apply pressure with clamps was a bust. The Clamps pressing on the top of the triangular cleat tended to tip the cleat up, opening the bottom of the joint with the girder. I solved this problem by drilling and screwing through the bottom of the cleats, which was a real pain with the stringers getting in the way of the drill, but it worked. Sorry, no pics today.
Steve Shumaker
USA 1183

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Shu
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Re: Boat in a box - the Shu3

Post by Shu » Tue Jun 10, 2014 4:57 pm

With the centerline cleats installed, I've begun beveling them to the proper angle. This is easy at the frames, but requires some extensive eyeballing to get smooth and fair transitions between them. I've also cut out the port limber holes, and have begun to seal them with three coats of epoxy. Once these two tasks are done, it will be time to start skinning the hull. My inner structural engineer will be a little sad to see all the elegant framing and stringers covered up, but they will reappear when the boat is turned over. Also, once the planing, rasping and sanding of the Port Orford cedar stringers is complete, the most aromatic phase of the build will be over. Alas, I cannot sail a framework; the boat needs a skin.
Attachments
IMG_3324.JPG
Limber holes all cut and first coat of epoxy applied.
IMG_3327.JPG
With the cleats and stringers beveled, this is perhaps the best time to see the shape, except for a certain level of distortion from the wide angle cell-phone lens. The uniform covering of skin will make the shape less obvious in photos.
IMG_3320.JPG
Here, beveling the port centerline cleats is nearly complete, and beveling of the starboard cleats has begun. The darker wood is a combination of excess epoxy and slightly weathered wood, so it is easy to see how much more needs to be shaped.
Steve Shumaker
USA 1183

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Shu
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Re: Boat in a box - the Shu3

Post by Shu » Tue Jun 10, 2014 5:11 pm

Just a comment on limber holes, and any other holes for that matter. I am carefull to make well-rounded holes so there is no sharp inside corner from which a crack is likely to propogate. Those with an engineering background will appreciate the principle of minimizing stress concentrations. This is the reason that inside corners of joints have epoxy fillets too.
Steve Shumaker
USA 1183

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Shu
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Re: Boat in a box - the Shu3

Post by Shu » Thu Jun 19, 2014 12:05 am

On the Shu2 I used 6mm plywood for the hull skin. I was able to obtain 5 ply 6mm for the Shu 2 and it had sufficient cross-sheet stiffness and strength that I could use the sheets longitudinally for the bottom panel and the topsides. The Shu 3 is being built with 4mm oukoume plywood for the hull skin. I was unable to obtain 5 ply 4mm Okoume plywood. 5 ply 4mm is available in aircraft-quality hardwood plywood, which is significantly denser than okoume, negating the benefit of the thinner skin. The downside of 3 ply material is that is has only one thin skin with the grain running in the cross-sheet direction, and furthermore it is in the center of the laminate where it does the least to resist bending stresses.

The solution is to use the plywood with the outside grain running athwartships, across the stringers. Since the sheets are only 4 feet wide, I will need to scarf a number of plywood panels together. Here, I'm scarfing two panels together to form the center panel. I use a special attachment on a hand-held electric plane to bevel an 8:1 scarf on the edges to be joined. The attached photo shows the two edges ready to be coated with epoxy. The right hand panel was then flipped over, aligned carefully with preset marks at the joint and the underlying plywood. A few small nails held everything in place with the underlying plywood. Covering the joint with plastic, and a small pit of 1/4" plywood, I stacked weight over the joint to press it flat while the epoxy cured. Now I have a single panel ready to glue to the boat.
Attachments
IMG_3328.JPG
8:1 bevels where planed on the edges to be joined. The feather edge with the grain running in the same direction has very little strength, hence the ragged edges. 4mm joints identical to this were used for the topsides of the Shu1, and have proved strong.
Steve Shumaker
USA 1183

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