Cross-Planking Suitability for “Large” Boat

I would like to build myself or contract with someone to build a wooden, shallow draft workboat hull with LOA LxW dimensions of roughly 49’x16’. Intended use is as a platform on which to construct appropriate weight and height cabins and pilothouse out of lightweight materials to create a “houseboat” with more seaworthiness than the typical box-on-pontoons approach as well as being able to walk safely around the perimeter. Slow, deliberate voyaging in rivers, bays and occasional coastal stretches and modest crossings are the hope, with willingness to delay frequently for good weather. A combo of outboard motors and simple sail plan for propulsion. I’m picturing a design with no decks or minimal decks, but that’s really only because I’ve thought I’d like to have free access to the bottom hull planks for regular oiling and inspection. A cross planked bottom appeals to me for it’s construction simplicity and as I think it looks appropriate to a simple workboat hull. I have three primary questions for those knowledgeable of cross planked construction and/or use of boats with same: (1) is it reasonable to use cross-planking where the boat width would require planks this long (i.e., 15’ mol)? (2) if so, can you speculate as to an appropriate type of wood and thickness? (3) might there actually be any advantage to a deckless design for regular inspection and oiling of bottom planks from the interior or is that a dumb idea? Thank you very much for your consideration.

 

Welcome to the forums.

What you are actually proposing is a 1800's "flatboat" (which fits you location better) rather than a "scow"; and, yes, they were open decked and their bottoms were cross planked generally in two staggered seam layers. However, it must be considered that historical flatboats where generally one-way items, broken up at the end of the trip for the timber, so the bottom planks were fairly thick (3-4") and fairly wide (12"+) plain sawn from the heart of the bole of, what was then, the pick of a virgin forest of trees. Because of this, and the farmers who built them, don't expect plans; though you can examine the USS CAIRO and CSS NEUSE for construction details because they were effectively built the same way by people with the same building skills/tools. The real issue I think is going to be the keels and/or keelsons; this type of construction generally has 3 or 4 (or more) external or internal keels that the bottom planks and frame knees are attached to. These are not insignificant timbers in size or length, generally running the full length of the bottom.

So, to answer the questions: 1) yes; 2) at the time they used anything long, straight and available; today it will be very expensive to buy the timber for a reasonable hull life of 20-30 years; 3) depends on how it is constructed, coated, and protected from the weather...way too many variables.

 

Thank you. I will see what I can look up regarding the two examples you provided, USS CAIRO and CSS NEUSE. Regarding the extremely long keels/keelsons, i was thinking I might be able to employ leeboards to help with lateral resistance and limit the longitudinal timbers that help tie together the cross-planking to being on the inside of the hull. If that’s the case, I wonder if I could utilize some type of laminated beams or similar - I’m sure I could never acquire any timber long enough naturally to run the boat’s length. Regarding my location, I don’t plan to stay in Oklahoma with the boat in question. Plan is to live aboard long-term and travel in my boat/home. Thanks again for the input!

 

1. Yes, but inefficient when it comes to lumber use, regardless if it's double planked or caulked. The keels jehardiman was mentioning above aren't for lateral resistance they're structural longitudinal members keeping the boat together.
2. Local species: bur oak, black walnut, eastern red cedar. Non local: other white oaks, western red cedar, douglas fir, larch, etc.
3. Every boat provides access to the bilge, for maintenance and storage. Asuming you don't want to step over the structural members keeping the sides attached to the bottom every day, you will have to build a second "floor" above them to have a straight surface to walk on. Before you ask, no, this isn't a house, you can't just nail the sides to the bottom with 16d nails and call it a day.
In boat language a "deck" is the thing that keeps water from entering from above, a "deckless" boat is an open boat like a pot without a lid, when it rains it fills with water and maybe sinks. On a boat any cabin that isn't entirely "above deck" is like living in the basement, you have to step down into the hull.

To get serious, this is 2026, a time when insurance companies and boatyards exhibit a pronounced negative attitude towards wooden boats, even new ones (yes you will need both on a regular basis). Also, the appropiate mechanical fasteners are more expensive overall then epoxy. If you have your own forest or can get very cheap wood then you build a wood/epoxy/fiberglass boat and use the word "composite" in any description and hope nobody finds out about the wood part. Otherwise you buy several barrels of polyester resin and fiberglass rolls and learn how to use it, workboat fashion (youtube is your friend, it has videos from India and Vietnam). If you don't like the smell of polyester you buy a truckload of steel or aluminum, a welder and enroll in the welding class at the nearest community college.
Afterwards you can line the inside with the woods of your choice to make it nice and keep you busy oiling and waxing.

 

Points taken re Insurance, boatyards, etc.. Also, understood with regard to the purposes of a deck on a boat. However, as to that point, there are loads of wooden boats with no decks and exposed bottoms, although probably not so large or used in the manner I described. No deck would undoubtedly create a variety of pains in the neck (and maybe safety issues) as to water getting into the hull in various ways.

I surely wasn’t thinking to just nail on the sides, but was thinking of construction techniques similar to that used on flat bottom skiffs, although that approach might be inadequate for a boat of these dimensions.

I have considered the idea of starting with an aluminum or steel workboat hull (built by professionals), maybe something like a hull used for an oyster barge. However, I’ve just wondered if some type of traditional wooden workboat hull might also be a viable choice.

 

I'm gonna put it in words you understand: you're gonna build a house with a porch. Around the porch you're gonna build a chest high wall and everything is going to be watertight but without a roof. Every time it rains the water is going to pool in the tub you created until the pumps kick in. All the airborne dust and falling leaves and whatever else the wind blows around is going to transform itself into sticky muck and you will have to power wash the porch afterwards and oil it.
That my friend is why if we don't put a roof over our porch we leave a gap between the boards and/or slope it down so the rain can leave taking the muck away.
Now, the joists for the porch and the house are going to be above the floor. You are also gonna put some joists at chest height, just so you can vary the exercise, step over the one, duck under the other, just to keep you nimble.
All of this isn't important when you haul a load of bricks or lumber or fish, the cargo doesn't care and the men have rubber boots and are paid for it.

Another thing is that on a houseboat you need to carry around all the things you would normally put in a shed, or a basement or a garage, meaning a septic system, a water cistern, fuel tanks, a generator, batteries, pumps, etc. Since most people like to have a view, they put the lot the basement that's created by having a deck and live above it. The ones that like living in the basement skip the house part and just buy the boat. If you like wooden boats it's not hard to find a 50+ft wooden powerboat for very cheap. You just have to afford the maintenance and the gas to move it.

 

Thanks. Your rudeness makes your advice much more useful. However, I don’t know why you’re using house construction terms like “porch”. I’m familiar with the terms normally used for the components of a boat and I’d guess you are also familiar with them.

 

I'm not rude I'm trying to make a point. You will have to use floors, so you need a sole. Workboats also often used heavy structural ceilings. Most barges and lighters aren't actually completely open, they have one or two big central openings designed to be covered.
Typical designs that also sail: Thames barge, Humber keel, Norfolk wherry, various dutch barges, great lakes scows.
We have a nice thread on New Zealand scows with photos showing the structure involved, and yes, some are cross planked and some are houseboats. New Zealand Scow https://www.boatdesign.net/threads/new-zealand-scow.28735/

 

It is viable if you have the budget for the construction and maintenance. Besides the skill workers for the build, you will need skilled labor for maintenance and repair. Other materials, including wood/plywood with fiberglass lamination, will be cheaper and require less maintenance.

 

Gonzo: Thanks for the reply re steel and aluminum hulls. Is the higher cost and skilled labor requirement for maintenance of those materials due to periodic need for welding and other metal repair, or is basic surface maintenance and painting also more difficult and expensive than with plywood/epoxy/fiberglass hulls? Also, setting aside the need for decking that’s been discussed, do you have any thoughts re viability of a traditional cross-plank wood bottom for a boat of this size (i.e., a hull bottom of roughly 15’ x 45’)?

Rumars: The NZ scows were definitely among examples I’ve been looking at. Also, 19th century scow schooners and scow sloops of US Gulf Coast, Great Lakes, etc.. Although smaller and less seaworthy than I’m aiming for, the “Toue Cabinee” traditional river boats of the Loire, with their flat, slightly rockered garvey hulls and fold down sail masts are also something influencing my ideas a little bit.

Thanks.

 

In ship building, like any other industry, the cost is one of the main driving considerations in design. Wooden boats are now either built by amateurs, as replicas, or paid for by wealthy individuals. Steel and aluminum can last for decades without the need for welding. The cost of painting is similar for metal or plywood/fiberglass. For planked construction the caulk must be renewed or repaired periodically. That is a very skilled labor that is disappearing as a trade. The ancient method of construction you mention would be like getting a Conestoga wagon as a motorhome. It is possible, but you will need to find feed for the horses and blacksmiths to shoe them periodically. Some people with enough wealth indulge themselves on projects like that. Is your goal to go boating or to have a traditionally built wooden hull with a cross planked bottom?

 

I think I misunderstood your prior message. I thought you were saying that maintenance of a steel or aluminum hull would be significantly MORE costly than for a wooden, fiberglass or ply/epoxy/glass hull. I think now that’s NOT what you meant, at least as comparing aluminum/steel to traditional planked wood construction. Sounds like maintenance of traditional wood construction would be typically the most expensive and challenging.

Although I find the aesthetics of a traditional and rustic wooden work boat very attractive, I’m not wealthy and I’m more interested in practical considerations of cost, maintenance, reliability, where I can safely travel in the boat, plumbing that works, easily accessed and repaired propulsion, etc.. Sounds like I’d be better off to steer away from the traditional wood idea. I had hoped that, if I kept it simple and rustic in nature without a bunch of fine joinery, teak, varnish, etc., it might be more practical but it sounds like I was fooling myself.

Thank you for the input.

 

I think steel would be the cheapest. One of the advantages of steel is that it can be easily repaired in the field. Also, adding brackets, etc. can be done by welding in the field. Are you planning on building yourself?

 

My primary idea for this, rightly or wrongly, was to get a professionally built barge/scow hull, either existing or newly/custom/semi-custom built with some firmly attached stringers built or added along the bottom onto which I could self-build a pilothouse, cabins, etc. using sturdy but lightweight construction and leave space to be able to walk around the perimeter. If a custom build, I’d work with the architect and/or builder to draft the design of the self-build parts and spec out correct parameters for weight, height, etc.. In a manner, a shantyboat of sorts but with extra attention toward seaworthiness and a pilothouse from which I can see fore and aft. Powered by a pair of outboards, but with a mast that can be easily laid down and a rig that could be safely single handed (maybe a junk rig).

 

Also, I really like your point about having it be “field repairable”.