CNC Cut Parts

A great benefit of 3D modeling is the ability to use a CNC shop to cut the temporary mold members (at left in Advantec sheetstock) and the permanent lateral members. Seen here are the Airex foam core and matching Okoume plywood parts for sandwich ring frames and cockpit components.

The holes for weight saving were ridiculous. The weight saving is negligible and the amount of extra work to clean up these areas after vacuum bagging was several hours.

Being a complete newbie to CNC cutting I used Hewes & Co in Blue Hill Maine. They do lots of CNC work for boat shops and they were fantastic to work with. They recommended mold sheetstock, additions to the cutting files and sourcing the cut material - all saving me many mistakes.

Strongback

I used sheets of half-inch sub-flooring ripped into strips twelve inches wide. These strips are overlapping 2 layers thick glued and screwed. So far this has worked really well. I built the strongback early on to use it as a known flat surface for glueing up the laminated frames, keel and stem.

Sourcing wood

has come to be one of the great joys of this boat project with the occasional sadness. I had the good fortune to source white oak from New England Naval Timbers in western Connecticut. As Duke toured me through his yard sharing stories of logging and the famous ships his wood has restored and built I was deeply honored to actually have oak from his yard.

I probably shouldn't be excited about having reject timbers but my project is small enough that I could hardly justify a custom cutting order. So we found pieces which had been cut for the restoration of John Steinbeck's trawler which was the vessel in the Steinbeck's Sea of Cortez.

I also purchased northern white cedar from A.S. Hudak in Vermont. Alexander has lovingly milled boards from trees which his enormous experience as a sawyer and logger suggested to him would have tight strait grain. I am going to try these for the second and third cold molded veneer layers.

The sadness comes when buying CVG Douglas fir and seeing how frequently Clear Vertical Grain means flat or diagonal grain, wide-grain, knots and voids. I lived for 20 years in Washington State hiking through the cathedrals of the temperate rain forest and am certainly a certified tree-hugger. And while I am grateful to not be consuming old-growth timbers - the hard reality of their scarcity makes me sad.

Laminating

The photos show the keel lamination and frames right out of the mold. There is so much back-and-forth about using epoxy on oak. I investigated Resorcinol but ultimately decided I needed a guru to show me how Resorcinol works. Not having the guru I went with West Systems G-Flex. I probably used much too much in the glue-ups. As I gain experience I use much less epoxy and have much less cleanup.

Here I used black plastic to wrap the lamination. Long story, bad idea. Use clear plastic if you can so you can see the alignment of the wood layers. Especially on long laminations the layers slide against each other and are not all flat against the horizontal plywood.

Also butt joints are a bad idea. I ran out of full length oak strips and butt jointed some together. As the layup is bent across the jig the butt joint separates leaving a void.

Setting Up

Setting up the mold pieces is definitely a place where "good enough" is not. Thank goodness for laser levels. I cannot imagine what shipwrights went through with buckets of water and hoses. Fortunately the good people at Hewes & Co suggested scribing waterline marks on the temporary mold frames which made alignment much easier. Doing it over I would scribe every waterline and buttock not just the DWL and centerline.

The vacuum bagged composite parts and the cleaned-up oak laminated frames are clearly visible.

Shaping and fitting the stem was a joy. After the initial cleanup, it was all hand work. Planing the stem was like minimalist sculpture - finding the fair line by intuition as much as by marked lines.

Steam Bending and the Sheerclamp

True to amateur form, I dreaded steam bending. The sheer clamp stock is one by two inch white ash. The aft section is an eighteen foot length bent around the fantail then scarfed to other pieces leading forward to the stem. I debated to steam or laminate. I procrastinated - moved piles of wood around the shop, swept. Then amazingly, I was whining about this conundrum to a coworker around the coffee maker. He said oh you should steam. I said why. He said that's what my family did. What do you mean - that's what your family did. Oh I come from four generations of cat boat builders on Cape Cod. Ohh. End of procrastination but not dread.

I extended a buddy's baseboard steamer made of four inch PVC pipe. Improved the boiler with a big canning kettle, radiator tubes and a kick-ass cooker. Forty minutes in the steamer and the ash was ready just in time as the PVC was beginning to melt.

Sure enough the sheerclamp went on the jig in thirty seconds and a few clamps later - voila.

The sheerclamp is tapered by half toward the bow to save weight and allow it bend into the stem.

When designing the boat parts in Rhino I had no clear sense of the sheerclamp and its strength, its structural importance and the effort required to secure it to the permanent transverse members. The foam cored ring frames alone would not provide a screw anchor point so I had to add blocking. The better way would have been to replace the foam core with solid wood at the sheerclamp anchor points.

Strip Planking

The first cold molded layer is quarter inch thick Douglas Fir strips. The thinking here was to have a light first layer which might be air-tight for subsequent layers' vacuum bagging. In reality, there is no way this layer as I have assembled it will be air-tight - there are just too many gaps where the strips do not fit as tightly as they might. Also I have found that there will be a good amount of fairing to do because the spacing between mold frames is too great. I now see the wisdom of using thicker planks which may be permanently screwed to transverse members. The ability to attach one plank at a time is a great advantage over glueing up several planks in a Hail-Mary batch. Also the thicker planks will be more naturally fair over the mold than malleable thin planks.

I decided to trust the Gougeon Brothers strip planking pattern and begin in the center of each hull side. Then work down to the sheer. Then work up toward the keel. This was probably the right decision. I spent a lot of time setting the first plank and trying to figure out how the heck this was going to work. Ultimately almost every section of the hull behaves differently.

I was not able to staple through the planks. The staples just crumpled. So I glued up in batches of three to five planks at a time. Tapered planks and stealers have been required to ease plank bend and achieve a tighter fit.

The longest strips are twenty six feet and many are over twenty feet long. There was a lot of scarfing. I ripped the stock into roughly one or two inch sections and scarfed those together. Then ripped the the full length pieces into the final planks. This worked well. I learned to use less thickener in the epoxy for the scarf joint enabling the joint to be much tighter.

After a three week COVID-19 hiatus the whiskey plank was finally placed with an appropriate AARRRRRHHH!