T&G Skin

I'm just now starting my first "real" boatbuilding project. Aside from my crazy OSB adventures, or my fir stripped galleon.

My designs are for a 21' gaff sloop, 3,100 lb displacement, single chine.

My main question(s) is about skin.

What types of wood are suitable?

Is it worth while to T/G, spline, or otherwise go the extra mile between planks?

Is there a benefit to turning the planking under the chine to a steeper angle of attack to the keel?

I met a man who rebuilt a 1940's cruiser. He used Fir 2x material for his skin, with nothing between, and relying on the wood expanding to seal the hull...I have to admit that frightens me.

My main problem is that, being a carpenter, I am not rich. I was considering red fir, and I like the look of a smooth hull. I'm really just not clear on the benefits or reasoning behind many of the skinning methods I've read about. it seems like a t/g with some kind of sealant applied to each groove would resist leaks much better than most other methods.

Repairing the skin would be harder, I suppose, but realistically on a small boat like that, with a chine, and cheap wood, I wouldn't necessarily mind replacing all the skin when it comes to that.

Any suggestions would come in very handy.

 

It sounds to me like you're being over-ambitious. You can find out how boats are built by reading boatbuilding books. It's less time-consuming than asking questions like the ones above.
A boatbuilding glossary would tell you that what you call skinning is planking.
The method you describe, of using tongue and groove planks, is not going to be a breakthrough boatbuilding method, it's just something that appears to make sense to a house carpenter.
Do youir homework. Nobody's so brilliant that they are going to reinvent the wheel before they have even begun their education in the subject. Start small and trust those who have come before you.
Follow a plan and deviate very little, especially with the design. Then ask questions that make sense, and you will be answered.

 

You're in luck, you have wood working experience. Many build their first boat with little more the a set of plans and a dream, learning how to butcher wood during the process.

There are many different ways to "skin" a boat, but it's not so important to the novice as Alan has mentioned. If interested in a dissertation about the different planking schemes, methods and principles behind these hull shell approaches, then there are several good books on the subject. You'll also get a lot of other helpful information as well.

The most important thing a beginner can do is stick to the plans. There's a fair bit of engineering going on and a seemly small change can have big impacts.

T&G planking has been tried, but it most often fails, unless the planks are especially thick. When the planks get wet, the tongue swells up and splits open the groove and now you've got a broken plank edge that's leaking, which generally isn't a good thing..

Yep, you can use sizable lumber, edge butted and have a water tight hull. If the planks are well fastened, when they swell, they'll seal against each other. This assumes nicely fitted joints and a boat that will not see much wet/dry cycling, which would eventually mash the seams and she'd leak.

You can make material and technique substitutions, but they have to be carefully weighed against the original concepts employed and the physical properties of the replacement(s).

Repairability is a very important consideration and one a good designer will anticipate, likely forcing them to make decisions about methods, application and materials in the process. No one likes to think about punching a hole in the planking or springing open a butt block, but these things happen. You can guarantee it will happen if you don't plan for the eventuality.

I'm just completing a build for a client. It's an 18' sailboat and it has a three piece rub strip on the bow. It's more trouble to fit this multiple piece rub then a single one, but it'll be a lot easier to fix when it gets dinged up and cheaper too. On the very point of the bow is a small nearly 90 degree bent piece. This area will likely be the first to receive damage and need replacement. Below this is another piece, down to the bow eye. This is the place where the bow will bash into things that seem to miss the deck line. Lastly is a rub strip that goes from the bow eye to the centerboard opening. This is the one that will get beat into the trailer rollers and winch stand chock. All can be removed without disturbing the others, if (WHEN) they get damaged, which is the whole point of planning for repairs. I'm the designer and builder on this little boat. I would have much preferred to install just one piece for the rub strip on the stem. Replacing 10' of stainless solid back half oval for a dinky little dent, would just piss me off, so it's in three pieces instead.

 

Hopefully, my post wasn't too off-putting. I too am a contracter. I've built homes and done a huge amount of finish work, including complicated staircases and custom kitchen cabinets.
It is indeed a natural assumption that such and such a method could cross-apply from homes to boats, and to a certain extent that's true.
However, there is so much to designing and building a wooden boat of the size you mentioned that there is very little room for guesswork and innovation for the beginning builder. If I could compare PAR's expertise, for example, with that of a graduate with a doctorate in quantum physics, I'd say that the doctor might begin in three decades or so to equal
PAR's level within his field.
Always innovate when other means to solve a problem fail. We all have to come up with new ways to do things as a matter of necessity when we have to survive in a field. My best advice to the beginner, however, is to be humble in the face of the thing you intend to master. You are likely not to have an original boatbuilding thought in your head for years, except maybe for minor methodology (little tricks of the trade). Accepting that takes a lot of humility.
Boat designing/building is a gestalt of many talents, so many that even amongst boatbuilders, few both design and build really well. They always seem to excell in one area or the other. Life is just too short for ordinary mortals to know that much about so many things.
Books are really a good resource because they actually save you all of the mistakes the writer himself has made, and at almost no cost. For design, look up Dave Gerr's books. For construction, all depends on the method---- strip-building, carvel, lapstrake, cold-molded, and on and on. There are books on each method. Those here with familiarity in each type can advise best.

 

I spend far more of my time with quantum physics equations than I do with boats (much to my chagrin) and I would agree with you Alan... but the corollary does not hold. It may take a physicist (ie, me) 30 years to match PAR's understanding of boatbuilding, but I think if the positions were reversed, PAR would see quite quickly that no matter how many equations and computer models you toss at it, nobody really understands quantum mechanics!

Sound advice. One of the telltale signs that you're dealing with a master is when he is not only generous with his wisdom, but humble about his expertise. The amateur is always jubilant over his new ideas- the master looks at it and says "yup, tried that once, doesn't work."

Are you familiar with George Buehler's "Backyard Boatbuilding" book? In it, he describes a traditional method of single-chine wood construction, developed from working/fishing craft, that is reportedly quite inexpensive. His method takes the hefty, durable workboat construction (carpentry skills required, but none of the difficult, arcane techniques of the wooden yacht builder) as the starting point, and adds some- but not much- modern cruising luxury.

In terms of what kind of wood- well, that depends what you have access to. Personally, I don't see much point in specifying something you can't get locally at a good price.

I don't think a 21-foot gaff sloop is too complicated for a competent amateur to design and build for himself, given enough planning time, enough books, and enough visits to the boatyard to poke around similar craft. It won't have the resale value that one by a big-name designer would, but that shouldn't stop you from having fun. But it is definitely worth the trip to the local library (or to amazon.com, or ebay, or wherever) to scrounge up whatever books you can find on boat building and design.

 

True about quantum mechanics. Until you concede that the very nature of evidence itself is subjective. Then, you can see how a chain of causes and effects are established as lowest energy outcomes. Only massive agreements are served, not objective realities. Classical physics describes the most complex agreements, quantum physics describes how it's not anything more than an agreement about a set of equations, and it could all be rearranged at any time. It makes sense in that respect.

 

Actually quantum mechanics and particle physics are pet hobbies of mine. Don't get me started on my opinions of why a photon remains a reasonable constant, or how badly E=MC squared doesn't work. Einstein was a brilliant man, while looking at other peoples work, at his deck in the copyright office. Then spent the remainder of his life trying to prove something that didn't work. I suspect I would have a different feeling of him, if he had use of my direct algebraic entry, hand held calculator.

This is one of my small gaff sloops. It's double chine, which provides a much more "sea kindly" hull form, with a ride like a round bilge. It's smaller then what you desire, but could be stretched to suit. It's also available in round bilge and either has a more shoal option available too. Building methods range from plywood over frame, thru taped seam, plus strip planked or molding are possible. She'd look especially nice as a glued plywood lapstrake. This isn't a puddle jumper, but more like a real little ship, fully capable of open water work.

 

This is one of my small gaff sloops. It's double chine, which provides a much more "sea kindly" hull form, with a ride like a round bilge. It's smaller then what you desire, but could be stretched to suit. It's also available in round bilge and either has a more shoal option available too. Building methods range from plywood over frame, thru taped seam, plus strip planked or molding are possible. She'd look especially nice as a glued plywood lapstrake. This isn't a puddle jumper, but more like a real little ship, fully capable of open water work.[/QUOTE]

Reminds me of a Ralph Stanley. Which design did you just complete, by the way?

 

I just finished a CS-17 (a highly modified Core Sound) for a fellow a few hours south of here. The current project is a similar sized boat as a fractional sloop (slightly larger), with an elliptical stern.

I think Discrete (RYD-14.11) has a lot of different influences in her. She was intended for wholesome cruising in a minimalist sort of way. She has lots of room for a 15' LWL boat and carries herself well in all conditions. There is one built and two presently under construction.

 

I like that category of boat. I've found that a boat that size gets more use than any other size. In this economy I'd guess there's a growing market potential. Up here too, a lot of folks must be hard put to continue cruising the 30 footers they no longer have the money to maintain.

 

Alan, I've updated the images above to include a couple of diagonals, displacement curve and the Bermudian version. The shoal keel is shown in a dashed line on the Bermudian plan.

 

Yeah, I noticed, and thanks. The full keel version is appealing. The Vagabond by Ted Geary, at 17' 2", is very close. It was an early double chine design, one I liked so much I swore I'd build it one day. My email address begins with vagabond172 in fact.

 

I remember that old design Alan, so I looked it up and found they are surprisingly similar.

RYD-14.11 is longer on deck by over a foot, has several inches more LWL, almost a half a foot more beam, but the draft is the same. In general my hull, though very similarly shaped, is leaner. Vagabond's D/L is 439, Discrete's is 385. Discrete has a higher SA/D to match it's large sail area, though stability and capsize screen are quite similar. My higher ballast/displacement in the full keel version makes for a stiffer boat.

The entry to Discrete's hull is slightly hollow, while Vagabond isn't and the diagonals are flatter in Discrete as well (leaner hull).

I also have slightly rounded sections below the first chine because of the torture in the plywood planking (a function of developed shapes), while Vagabond has straight sided sections between the chines, as it was planked with solid lumber.

Deadrise at various portions of the hull are close, but different enough to lessen wetted surface and reduce displacement (comparatively) in Discrete. She's only about a 100 pounds heavier in displacement then Vagabond, but over a longer length, so easier to propel.

It's interesting how striving toward obviously a like minded design brief, we'd come to conclusions and decisions that make a both shaped as they are. There are many differences, but also many similarities. I guess the saying " there's nothing new in yacht design" is more true then I thought.

 

Did you get all that from Monk's book, or find it online? I have the book, but one significant page (a fold out) is missing. I've been carrying the book for 35odd years.
I never found it online, but there was a reprint of the book I saw in a book store once..

 

Neither, it's in a data base I've assembled over the years, which includes basic drawings and dimensions. Which drawing are you missing, I may just have a digital copy of it.