Custom Paul Mann

[cheeks]

Originally Posted by Glenn W

Thanks for the input on this. Your explaination would appear to make logical sense for an all wood boat, but I still don't understand the logic in glassed over boats using this plywood over plank techniue--- especially when the inside is also glassed and sealed.

The problem is it is not sealed. Epoxy is semipermiable. Moisture will get thru.

[Glenn W]

Originally Posted by cheeks

The problem is it is not sealed. Epoxy is semipermiable. Moisture will get thru.

That is my understanding and hense the use of sealers such as adtech (sp?) and others? I still don't understand how this plywood over planking is such a bad method if many boatbuilders are using this method with success that lasts.
What is the prefered method of wood coring?
And if it is not too much to ask, what is your background, and qualifications?--- I might be asking questions of a kid for all I know?
Thanks

[T380Fisher]

Cheeks...for informational purposes, some of us dreamers may actually look to own a custom Carolina dreamboat someday..

What production style do you recommend for cold mold....or is cold molding the problem in your opinion.

I always thought they used juniper because it had an extremely low tolerance for movement wet or dry. Is it just the fact that in PM's case they skin it with plywood?

More info on your point of view would be great...info is what I am looking for from this site as I am not a professional fisherman or boatbuilder, but want to expand my knowledge of both...that is what I like about this site.....I don't like people trashing others without the facts to back it up.

[cheeks]

Originally Posted by Glenn W

I say all this not because I have any allegence to Paul Mann, but rather because I am interested in modern wood core boat construction. So I am most interested in undertanding why this techniue is so poor in your opinion.

Plank on frame and Lapsrake were the way boats were built before we had gap filing glues such as epoxy. Epoxy opened up a whole new world of possibillities in the sixties. There are alot of ways to build a "cold molded" boat and alot of good techniques out there.

Plank on Frame is the old school way to build a Carolina Boat. A few guys still build this way. If you want to see pictures check out the Bobby Sullivan thread. There is nothing wrong with plank on frame boats. They have a few draw backs. They are heavy because all of those frames and you have to cork the seems. You also must be careful the fastners are not eaten away by electrolosis. A "hot" marina can cause big problems for plank boats.

What you see in those photos is a poorly built plank boat beeing sheethed with plywood. I am at a complete loss for why anyone would do this. There is no reason too. Forgeting the delamination problem for a minute, why would you want the additional weight of the frames. If you strip planked the boat instead you would only need half as many frames.

Plank on frame boats require alot of skill and skilled labor. You have to Line off every single plank. Every single plank is "hogged" or planed to fit the frames it lays on. This is a skill that seperates the men form the boys. Truly an art form that requires years of experience. Especially on carolina boats with extreme flair.

They are attempting to get around lining off by just running four inch planks(I assume scarfed together) using fastners at each frame. Then covering the whole boat with plywood. Ahhhh........... and this is where these boys have created a huge problem for themselves. You have to plank with flatsawn boards or you will split the plank by putting fastners in the same grain line splitting the plank. Even if you use quatersawn it wouldn't work with planks that wide. Flatsawn boards are the least dimensionally stable. Trying to sheeth them with plywood is insanity.

[cheeks]

Originally Posted by T380Fisher

Cheeks...for informational purposes, some of us dreamers may actually look to own a custom Carolina dreamboat someday..

What production style do you recommend for cold mold....or is cold molding the problem in your opinion.

Cold molding is not the problem. It is a great way to build a boat. There are alot of ways to build them. IMHO strip is probably the the best becuse of the increased longitudinal strength.

[bac jr]

One thing that is for sure about the plywood sheathing is it definately makes fairing for final finish easier.

[fishskipper]

I'm just trying to understand this.... If there is delamination between the plywood and the juniper, wouldn't the juniper still be there... Since it is put on in lengths how could this cause a hole in your boat when the hole is no bigger than 12 by 18 inches as in the Dream Catcher.

[dubb]

The only reason that plywood is there is to make the fairing process faster and cut down on labor.

Cheek, How much shrink/swell do you think there is in one of those planks?

[Fortunate One]

Cheeks -

Perhaps you should pick up: The 4th edition of "The Gourgeon Brothers On Boat Construction Wood And West System Materials" and read chapter 20 entitled "The Strip Plank Method for Laminating and Strip Composite Construction."

If I may:
Chapter 20 Paragraph 1

The strip plank method for laminating hulls is a cross between the mold method and traditional strip planking techniques. Mold frames are set up and solidly planked, usually with edge glued strips of softwood. The set up is then covered with layers of plywood veneer. The strip planks become the interior lamination of the finished hull. When construction is finished, temporary frames are removed. The rigid, monococcque structures which can be built with these methods require substantially less interior framing than other types of wooden boats."

Although that chapter refers to installing diagonal layers of plywood strips over a planked hull. Elsewhere in the book I'm sure I've read where it is OK to use larger sheets of plywood as a preferred method to save time.

Chapter 17 Laminated Hulls - A General Discussion Page 145
THE STRIP PLANK METHOD

" Because of the expense of the mold and the labor needed to install interior members, it's often hard to justify the use of the mold method on larger one -off hulls. To get around these extra costs, we thought about using the mold as part of the hull, and from this developed the strip plank method of laminating. Most molds are strip planked anyway; with this technique, the planking becomes part of the structure and does not remain part of the mold. Strip planking is efficient and economical for bigger custom boats.

Hulls have been planked with edge-glued strips of wood for many years. Strip planked fiberglass hulls appeared at about the same time. Larger strip planked boats rely on intricate interior framework for athwart ship strength and stiffness. The alternative to interior support, sheathing the planking with fiberglass cloth as is done with stripper canoes does not provide enough strength for larger hulls. We discovered however, that we can build an exceptionally rigid and strong monocoque by using the basic strip planked hull as a form over which to laminate diagonal layers of veneer. The layers of exterior veneer eliminate most of the interior framework associated with larger wooden boats." It goes on for a paragraph on bulkheads but then it gets back to; " Strip planked hulls have thick load-bearing wooden skins. They are reasonably light, with high strength and stiffness to weight ratios. As a bonus, the thickness of a strip-planked hull provides excellent insulation from noise and temperature and it may also reduce condensation problems. Practical considerations generally limit the use of strip plank method to boats of perhaps 30 feet or more, but some heavier displacement, shorter oceangoing cruisers have been built with this technique."

My hull is carvel planked mahogany on full frames 16" on center and full length Douglass fir stringers tying into a solid oak stem and using a solid purple heart keel mounted to a full length Douglas fir keelson. There are 2 layers of Okoume scarfed diagonal plywood strips running in opposite directions over the mahogany planking and the exterior skin is glass and epoxy and the interior is epoxied with fillets at every connection where the planks meet the frames. This hull construction is rock solid and will be around longer than I.

We've built a hull that has no flex what so over. We will use laminations of plywood and blasa and nidacore for all non structural components including decks but any place where we want strenght we were sure to add it. Nothing worng with having full lenght stringers that measure over 20" in height in the deepest part of the boat.


I'm sure Mr. Gougeon knows of what he writes.

[cheeks]

Originally Posted by fishskipper

I'm just trying to understand this.... If there is delamination between the plywood and the juniper, wouldn't the juniper still be there... Since it is put on in lengths how could this cause a hole in your boat when the hole is no bigger than 12 by 18 inches as in the Dream Catcher.

I have no idea what happened to Dream Catcher. I have never seen the boat nor do I know how she was built.

The problem with delamination is modern adhesives form joints that are much stronger than the wood itself. The joint itself does not fail the wood around it fails. So when in this case the plywood delamites it could take alot of juniper with it.

If you want so see this for yourself, get a piece of 1 by 3 lumber and put a 10to 1 scarf in it and glue it together. The next day put one end in a vice and pull on the other until something breaks. You will see what I mean.