Budget long range cruiser fit for Pacific crossing - Ideas ?

Keith there is a lot of good basic information that may help you out in David Gear's "The Nature of Boats" and "The Elements of Boat Strength." "The Nature of Boats" gives an overview and compares lots of different types of boats. Pros and cons. "The Elements of Boat Strength" sets forth conservative scantlings for wood, fiberglass, steel and aluminum boats. His scantling rules are easy to understand and use. And there are lots of examples.

Last time I checked the cost of foam was significantly greater than the cost of plywood. It has been a while. A strip planked boat is not made of plywood except for the internal bulkheads. The strips are typically made out of cedar. I have also heard of redwood being used for the strips. Lots of options to choose from which brings us back to how helpful a SOR is in focusing on what you want in your boat.

 

Take a look at the PVC foam here PVC Structural Foam - Sheets - Carbon-Core Corporation http://www.carbon-core.com/product/pvc-structural-foam-sheets/

 

Foam is interesting stuff. I have no experience using foam in boat construction or repair. I have done lots of fiberglass repair over the years and the last year I was in Mexico I extended the transom on my sailboat by 30 inches. I did the extension by myself with no help and was lucky to pull it off. The thing that I learned from that was that you really need a very experienced crew knowledgeable in fiberglass construction to build anything of any size. If I had to do it over again I would use epoxy because of epoxy's longer working time. Polyester resin has almost no working time. 15 minutes max. In that short window you have to wet out the cloth, get it in place and get all of the air bubbles out. And then get the next layer in. It was a mad rush. I can't even imagine trying to layup a boat of any size by myself.

It is my understanding that the two main issues with foam cored boats is the shear strength of the foam and achieving a good bond between the foam core and the fiberglass skin. On go fast race boats where weight is critical the skins are pretty thin. Especially the inner skin. But these boats are thought of as disposable. On cruisers or any boat that will see hard use the skins need to be a lot thicker and hence are heavier too.

You had asked in a previous post about slicing foam into strips and using the strips to strip plank a hull. You don't need to do that. You can get foam scored so that it will bend and conform to the shape of the hull. Scored foam will even conform to compound curves.

You will have to research fiberglass construction to see if it works for you.

 

You might want to review Goodwilltoall's thread on his build. Affordable seaworthy cruiser https://www.boatdesign.net/threads/affordable-seaworthy-cruiser.33980/ It's a looooong skinnnnnny boat. There might be some info there that will help you out with your boat.

 

Chuck, the scored foam with a scrim on one side to hold it together can do some slight contorsions but nothing close to what you can do with the foam strip planking. You just need to watch the video posted to understand.

 

In the book "Fiberglass boatbuilding for amateurs" by Ken Hankinson (published by Glen L) ISBN 0-939070-05-7
chapter 21 is titled: High modulus materials and speciality reinforcements" Chapter 22 is on vacuum bagging.
The example used for demonstrating the techniques, including foam core are from a 40' sailboat hull which weighed 700lb (hull, deck and cabin). This particular hull had cross linked PVC core and at least on the outside, 3 layers of UNI, equivalent to 1 layer of stitched triax. Laying individual layers of Uni is probably easier to get conformal and wetted out and the strips are simply butted together, no overlaps and then second and 3rd layers being oriented as per plans.

I also bought a book titled "True round metal boatbuilding - Bezier Chine design" by DL Schafer ISBN 9781533471222 Its a fairly recent book, published in 2016. I get the impression it is self published. It described building a 12 foot "true round" hull sailboat out of aluminum plate. Being a small boat, the curvature of the plates is quite extreme, but the point of the exercise is to demonstrate that it is possible to build a beautiful full round hulled boat out of steel or aluminum with every plate pre-engineered with CNC cutting files and drawings with lines for each bend in the plate (every 2 degrees) and all bends are made in a hydraulic press brake, no english wheel used...


The thing to understand about Schafers book is that it illustrates how you would make the individual plates for your hull from drawings / templates that he provides and the procedure used to dial in the pres brake used to make the bends. Also the process to assemble the hull and welding sequence. It does not provide you with the tools and knowledge to design your own boat and then break it down into the individual plates... Now he has a second book in the making "Applied metal boatbuilding methods" and that may delve deeper into the details, I do not know. So if one wants this technique applied to your custom boat, you would need to work with him to produce the neccersary design files. I will say that his plans, which are very detailed for a 28' and 35' sailboats are very cheap. $320 for the Bezier 28 and $490 for the Bezier 35. Some naval architects charge $9-12k just for the cutting files for the plates....

Bezier 35 below

 

Bagging a 40' hull is no small task. It is much easier to infuse, but that requires competency. My boat is all vac bagged dev panels. It is really a slow and difficult build process in my opinion. Each panel needs a dryfitting, then lamination on a table. The benefit is the boat is ultralight. My boat has some weight penalties. Mat tapes is the big one at 275#.

The aluminum boat would be MUCH easier to build as would plywood. The aluminum requires some competency; the plywood is really easy to build and tight joins are actually bad, so you don't even need to be precise. The aluminum, of course, gets you out of all the epoxy mess, so it is probably the fastest build time. I imagine some use of epoxy or foam or ply is needed for interiors. And condensation requires management (foam).

I couldn't love aluminum for the noisiness and for the fact aluminum corrodes in seawater. I couldn't love plywood for the rot potential, but I sort of do now for the build speed I didn't have.

 

Infusion on a "1 off" is probably a very risky affair. If one screws it up its a very expensive setback. I think doing hand lamination and compacting through vacuum bagging is more feasible. Sounds like thats the route you took.

 

I watched the video. It is similar to how Hobie Alter made the hulls when he was doing the R&D for the Hobie 33. I was in his shop one day when they were planking up a 33 hull. The difference is that Hobie made a male mold out of plywood bulkheads and used thin wall metal tubing instead of wood for the ribbands. Instead of screwing the foam to the ribbands Hobie and his crew took strands from woven roving and tied the foam to the metal tubes. Glassed the entire outside of the hull and finished it off before removing the hull from the molds. To remove the hull all they had to do was cut the roving strands. They then glassed and finished off the inside. The hulls were hand laidup just like you would layup cloth and resin on a surfboard. Hobie told me that it took them about a week from start to finish to make a 33 hull. Hobie used sheets of surfboard foam that he got from his friends at Clark Foam. I should know this because my son traveled the world on the pro surf tour for 15 years but I don't know what type of foam is used to make surfboards.

 

As in the Farrier 2012 Study Book PDF, on page 37 to 46 of 60, which has been vacuum resin infused by a newbie on his F-39 build.

‘‘ . . . At the end of the last century I did my research on the modern high tech composite materials, which were all new for me. . . . ’’

It happens to be all just posted on the thread Multihull Structure Thoughts in post #143 to #146.

 

Re post #61, not everyone stays anchored out off Sausalito forever once they get there, Suzie & Jules moved on despite very good open Wi-Fi there, the mentioned Richardson Bay at ± 8:31 is just north-northeast off Sausalito, and it gives good info of getting on a budget onto the web for cruisers with a good antenna once they get near to shore, below's a Bitstorm Bad Boy...

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If you are going to use strip plank foam for your build Schooner Creek Boat Works in Portland, OR had an interesting variation. IIRC they started with a male mold. The first layer was a wood veneer followed by a layer of glass set in epoxy then 2" square foam strips, then another layer of glass and epoxy finished up with another layer of wood veneer. I believe after a certain number strips a layer of glass set in epoxy was put between two strips to connect the inner and outer veneers together I am sure that there was more to it than that. It created a very stiff light weight hull. Since you are building a boat with no ballast and a lot surface area this type of construction might make you boat unsinkable. And there would be a lot less work fairing the wood veneer outer skin compared to fiberglass. The two most well know boats with this construction were probably the ULDB Rage and Ocean Planet.

 

Schooner Creek Boatworks in Portland, OR built the 28' Ocean Rowboat* Emerson that way for Jacob Hendrickson.

* some build pictures down below on the linked page

Designed by Eric Sponberg, subject thread Pacific Rowboat.

 

The pacific rowboat is similar to Rage and Ocean Planet in that they used foam strip planks but they did not use the veneer on the inside and outside of the foam. Might have added too much weight and they probably didn't need the extra strength that the veneers would have provided. The veneers in Rage and Ocean Planet were set on a 45 degree angle. I recall reading somewhere that in testing the Gougeon's found that veneers on a 45 didn't add much strength compared to running the veneers at 90 degrees. Leaving the veneers natural finish would certainly make the interior far more appealing then painted fiberglass.

 

Yeah. Very slow. High pressure to perform fast.

I would infuse if I started now. Not whole hull, but panels.