Boats – Some A Bit Too “Minimal”

We’ve had a boating discussion break out on a couple of threads now. Then I spent part of an evening looking into various “minimal” boat designs. Why? Well, not having a lot of space on which to park things, like a boat, and not having a giant truck in which to haul one, and being “under endowed” without $Thousands++ to buy one; I’m in the more “minimal” and potentially DIY market.

On YouTube there are some truly great DIY boat building examples. One make a miniature Viking Boat (sized for 2 to 4 as my best guess). Another makes boats using aircraft techniques for ultra light weight craft that are easy to carry, port and even hang on the wall, but that don’t allow disassembly for minimal storage. It’s just fascinating the different things folks use to make boats. It would seem “Gotta hava Boat!” is deep in some folks…

But some of them have gone to extremes that are a bit too “minimal” for my tastes. Yes, it works. Yes, it’s a boat. Yes, it’s better than my nothing. But….

So here’s a collection of a few of the more interesting minimal boats I’ve run across.

Nice. Workable.

Just be careful where you step getting in… There’s a series of these designed by Platt Monfort here:

I especially like their “Car Topper 9” at 28 lbs that can take a sail or motor.

This looks like a not quite as high tech nor as light “knock off” in general look and feel, but could also just be a more traditional canoe design with the open wood and dacron look about it, prior to being paint coated.


Has lots of good ideas on how to make a sailing cat. Also shows, IMHO, the evolution of boats in history as one man recapitulates those motivations and actions. Just substitute a tree trunk for PVC pipe ;-)


The next one has an interesting pontoon design. I’d likely use ‘joist hangers’ on that center beam instead of hanging it on screws, but it seems to work. I’d also go for a PVC rudder handle or reuse an old rake / hoe hardwood handle, but you use what you’ve got.

For the limited money, and the generally simple assembly required, this guy got a quite usable craft out of not much stuff. A layer or 3 of spar varnish over the wood is needed for long term use. I would likely need larger pontoons (being a bit, erm, “large”…) and I’d add some ‘junk & gator catching’ nets for and aft of the seating; but I could see fishing from one of these…

At the other end of things, this design is made to be modular, fit in the back of a “Smart Car” (so anything else will be bigger and more roomy!) but takes a few weeks / months to build and careful technique. It is a micro-sized cat with a motor not a sail. Being small and close to the water surface, not for rough waters or gator country, but the techniques are interesting. Though to see the techniques, you will need to hunt up parts 1 & 2. Here’s the final in the water part:

Have plywood, need boat. No frills, just Jon Boat and kids.


Well, it is a boat

One piece of plywood, 4 x 8, some trim wood 1 x 2 and a 2 x 4 keel. Nails & screws. Glue. Paint.

Well, it works. I’d rather have a seat like in the next boat, and I’d leave out the “window” so as to allow a more middle of the boat seating position. As it is, in his test run, the weight is too far back and the rear is too close to swamping. Certainly quite a low barrier to that Gator looking for a snack on a cracker… ( or a Cracker on a shingle?)

There are occasional cardboard boat competitions. The idea being to make something fast and not sink before the end of the race. This guy takes it a step further and makes a more durable boat, even if it does take a while to build. IF you can keep it dry inside the walls, cardboard is quite light and strong.

This one claims to be a “Pallet raft” but it looks like about 2/3 of the wood is bought new. Still, I love the 3 generations boat building together, and the appropriate attention being placed on beer bottle holders ;-) His accent is something Germanic, but a bit more north; while I can’t place it, it does speak to a beer appreciation ;-) The use of tension members holding plasitc flotation cells, attached to eye bolts reminds me of my own design approach (steel barrels held on with steel wire to eye bolts on my old raft).


You did WHAT?

Clearly I’m not thinking big enough with my desire for a pontoon boat with a gator fence around it. What could be better for reaching those hard to reach fishing nooks than a flying boat? And one equipped with a ring of “Gator Choppers” around the edge, to boot!?

Though for folks wanting an even bigger ride with longer reach, there’s this one; though it’s a bit commercial:

A “pool noodle” raft / boat. Note that at about 6 minutes you can see some earlier creations being “tested” on a local lake using larger PVC pipes as a kind of “pontoon snowboard” on the water… There’s a design principle in building stable boats that the buoyancy needs to rise (preferably non-linearly) as a boat tips to one side or the other, in order to impart stability. Basically, once your pontoon goes underwater, you are going on over as weight is increasingly shifted over it – that’s why pontoon boats need to be very wide (less mass shift) and have the pontoon only 1/2 underwater (since for round pontoons, buoyancy increases taper off as the ever smaller top 1/2 submerges – the opposite of what you want – which is why “professional” pontoons are wedge shaped and fatter on top). This guy “didn’t get the memo” at 6 minutes, but has realized some improvements needed for his noodle boat.

With added “features”, but not quite enough for 2 riders:

But not to be outdone in the noodle boat arena, we have lots more room for creativity.

This guy wanted a kind of a ‘sea turtle cycle’ so made one of noodles. WITH an electric motor!

Then, a couple of what I think are Ukranians doing some extreme minimalism. First a boat of just styrofoam. Yet it works. Does give me ideas for styrofoam covered with “something”. I could see a 1/8 inch plywood surface then spar varnish, or just a fabric / resin topper. (Though the resin would need to be styro-safe… low in hydrocarbons that dissolve styrene)

Then one from just cardboard and a plastic skin:

It is just amazing what can be done with nearly nothing…

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About E.M.Smith

A technical managerial sort interested in things from Stonehenge to computer science. My present "hot buttons' are the mythology of Climate Change and ancient metrology; but things change...
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52 Responses to Boats – Some A Bit Too “Minimal”

  1. ossqss says:

    Minimal and simple ;-)

    Talk about recycling! Look at the friggin engine on this thing! Must be to escape Croc’s maybe……

    I better get back to work *¿*

  2. jim2 says:

    I think something other than PVC pipe would make a better float/$. Something like this, maybe:

    There are a lot of other water tanks out there, portable or otherwise. Most have a good bit more volume per length, or per dollar, than PVC pipe. Although the pipe will be tougher in most cases.

  3. philjourdan says:

    It would seem “Gotta hava Boat!” is deep in some folks…

    Some? I thought it was all. Learn something new every day. :-)

  4. H.R. says:

    I see the Rebel Cat builder caught on to what I noticed; 2x4s add weight whereas properly braced 1x4s would work just as well. I did like how the wooden pontoons were boxed in halves and then joined together with bolts. That makes 4 chambers for safety and greatly eases transport and storage.

    My father grew up in a town along the Ohio River and built a plywood jon boat while in his teens. It’s just what guys did at his age back then. He lost it in the flood of ’39. He had it chained and padlocked at the river (more to prevent joyriding than prevent theft). He went down to unlock it, hoping to find it later downstream, with a bit of luck. Too late; he said he was almost swept away trying to get to the padlock and he was very lucky to get back to safe ground, so the boat got beat to death at the end of the chain by flood debris.

    I’m still mulling over the options, though this post opened up several new ‘ponts’ to ponder. Doped fabric on a frame looks promising to make pontoon chambers. It would require judicious applications of wood veneers to protect against punctures and bottom scrapes.

    @Phil: Yeah, I think the ‘gotta-have-a-boat’ gene appeared in men about 1.5 million years ago at about the same time the ‘ummmm-bacon’ gene began to express itself. 😜

    @jim2: Scrollong down, the 40-gallon cylinders look really good for making a raft-like rig, and only $78 bucks a pop. Four of those would float a lot of light decking.

  5. Graeme No.3 says:

    Some alternate designs. Have fun even before your boat is built.

    Also Google etc. for images.
    F.Y.I. Darwin harbour is known to contain salt water crocodiles which would eat your alligators, especially if they were riding in a make-piece boat. Darwin inhabitants are also noted as ummh? ( I might want to go there in the southern winter).

  6. Graeme No.3 says:

    “I would likely need larger pontoons (being a bit, erm, “large”…)”
    Multiple PVC pipes at largest diameter (120mm?) with cross frames they fit into. The seat could be the top of one ‘frame’. Netting attached to the end of the frames? More a raft than a catamaran but who wants to set a spead record?

  7. p.g.sharrow says:

    If you go that route, polyester resin can be applied to the Dacron and will shrink just like dope,.It can be repaired or added to later.
    If you go with polystyrene foam, use epoxy resin to coat it as polyester will melt it.
    Rigid polyurethane foam board can be polyester coated.
    If you are not in a hurry, 6 miles a hour, most any shape will work well as it is mainly flotation. As you speed up the shape becomes critical…pg

  8. H.R. says:

    PVC is out… too expensive. A 10″ 45 degree elbow is around $100. A 10′ length of 10″ pipe is closer to $200.

    Wood is looking good. Covered foam is also looking good, though I haven’t priced it yet. That Wide Cat is starting to look better and better.

  9. jim2 says:

    I think aluminum angle and aluminum expanded mesh would probably be lighter than wood. It can be bolted together, welded, or brazed. There exist aluminum brazing rods.

    Also, aluminum sheet might make a good wedge for the front of the boat.

  10. p.g.sharrow says:

    Unless you are a real welder and metallurgist I would recommend you Do Not consider using Aluminum. Expensive stuff and tricky to work with. Professional only, I have done a lot of Aluminum work.
    I would recommend wood and fiber glass/ polyester resins as the materials most suited to backyard construction abilities, Most versatile, most forgiving, light weight, repairable, inexpensive…pg ..

  11. E.M.Smith says:

    Aluminum isn’t hard to work with at all… until you have to weld it.

    Unless you have a lot of experience as a welder, have a good inert gas TIG rig or similar, and don’t mind practicing a bit prior to starting the job; I’d avoid trying to weld aluminum. Very high heat transfer rate means you put in a lot of energy and then if you get just a little too much or move your line of weld just a little too slowly, you get a puddle of melt on the floor and a hole in the work piece. Melt temperature is low, so hard to tell when it’s about to transition, and then the high heat transfer means a large area “goes when it goes”. Oh, and it burns well… Some alloys have a goodly level of magnesium in them.

    For real fun, the early VWs had a magnesium / aluminum alloy transmission case. Properly made piles of filings were reputed to make a nice bright light when lit on fire. We didn’t have a welder then so tried lighting it with other means and never got it to go. But still, it was one of those things you were supposed to be aware not to try, welding one of them…

    Don’t know about aluminum brazing. I’d think the tough intractable aluminum oxide coating would make that hard to do… but hay, technology marches on and I’d be willing to investigate it if metal was my design.

    Per Other Materials:

    I’m thinking I really don’t want heavy. The idea of a foam core with 1/8 inch plywood over it and then a single layer resin / fabric skin is speaking to me. Basically, lots of near nothing foam for buoyancy and as support for the thin wood skin, then the wood layer for strength and surface protection (and some looks). A bonded 4 inch foam with thin ply each side is quite strong and resistant to many insults… Then a layer of composite for the places that need added strength and abrasion resistance. Varnish over wood for places where looks matter and strength not so much.

    Having the foam inside things like the floats also makes them more gator proof. He can put a tooth through it easily enough, but water does NOT flood in and fill your pontoon.


    Yeah, did a turn through the local Home Depot today. Was shocked at the prices on materials. Plywood at $40 to $50 / sheet? When did that happen?…

    Not even marine grade or A grade surface either. Just crap plywood…

    I’m drifting ( ;-‘) toward the idea of veneer over foam. Oddly, nice flooring was fairly cheap and looked good too, and includes nice formed edge joints. So I could see a ‘mostly squarish’ design with foam core, wood flooring veneer, and top coat of spar varnish (all held together with adhesives) and then with wear edges reinforced with composite fabric / resin (fiberglass or dacron)

    Not too heavy, nor too expensive, yet strong enough and punctures don’t sink you. Not as easy to make as a bit PVC pipe, but it looks like retail prices for construction goods are a bit crazy and large PVC is going to be a custom order (unless you buddy up with someone building out a subdivision with large orders of pipe for drainage… when last in Florida one highway had miles of what looked like about 16 inch greenish pipe laid out. I think it was taking water to a new subdivision… or draining it…)

    Frankly, that well made cardboard boat with paper and varnish finish surprised me. Not keen on the idea that water under the skin would turn your core material to pulp (literally…) but it got me thinking. There are “coroplast” boats made with what is basically plastic “cardboard”. Usually these are single sheets folded as Origami boats. But nothing would prevent using it as general structural core with skin over… I could see a trimaran with coroplast center and resin / glass over Styrofoam pontoons.

    I really like the designs at, but they would be worthless if a gator decided to take a swipe or bite at them. I’m not willing to bet my life that no gator will ever get to the boat before I see it coming. That “must take gator bite or claw” design point means not going ultralight with open air flotation chambers. I’m going to have foam flotation somewhere enough to keep the boat functional even if bitten or swamped. (Had figured on tough PVC pontoons, but the cost is much higher than expected and they are heavy)

    So as of now I’m leaning toward something like an upgraded version of the Styrofoam cat above, or a wooden Jon Boat style made with some added foam sections and maybe an outrigger (stand up casting… even small outriggers can stabilize it a lot against tipping and swamping)

    I think I need to make a few thin wood over styro panels to assess how hard they are to make and how strong they are when done. Think of it as ultralight plywood… and make a resin / fabric test piece or two also. Folks make very strong aircraft wings out of doped dacron over foam with a spar in the middle… (Dacron is the same as PET or PETE water bottles is the same as Polyester in cloth. So you do not require aircraft grade dacron. One could hit up the local fabric store for whatever polyester fabric was not selling well… )

    Oh God, I can see it now: A paisley boat… May be worth paying extra for a tartan instead…

    @Graeme No 3:

    Oh yes! The beer can regatta! I’d forgotten about them…


    Hmmm…. spouse goes through a case of water bottles a week… (Kidney stone resulted in doctor ordering a lot of water be consumed and one brand in particular has more of the right chemistry to keep things flowing for her. Dasani has added magnesium…) I could easily get ll the materials needed faster than I could use them…. Hull drag looks a bit high though ;-)

    There’s a pontoon boat that uses one of those big barrels as the main compartment and then pipe for the pontoons… Fun for one, but hard to put stuff in it ;-)

    @Phil & Jim2:

    Hmmm…. Which came first, the “Ummmm Bacon” gene or the “Gotta hava boat” gene? Interesting question ;-0

    Pigs can swim.. wonder if it was while chasing a pig that hit the water….

    Polynesians carried pigs with them to new islands, so clearly boats and bacon have been fellow travelers since the dawn of man… or at least of Polynesians…

  12. E.M.Smith says:

    Forget all that structure and skinning and all, just use a chunk of foam and add gunnel rails…

    Someone already did the glass on foam test for me

    here’s 5 of at least 8 segments where the boat is mostly done. Looks like glass over foam is quite easy and strong. I find it interesting he uses fleece cloth for the skin..

    So overall it looks like it would be very easy to build up some styrofoam pontoons and cover them with cloth / resin and be “good to go” on that front. Form in a wood beam to attach it to a deck bit in the process. Varnish or resin over the wood.

    Then make a nice light modular deck for the fishing platform and Bob’s Yer Uncle.


  13. E.M.Smith says:

    Folks will find a way…

    The fishing chair. (Note the trolling motor!)


  14. E.M.Smith says:

    Interesting school project making pontoons:

    Uses polyester resin over foam so no need to pre-coat with white glue…

    Just form your foam and apply glass / resin. Set in sun to UV cure.

    By rounding the corners on the bottom they get very good and easy glass conformance to the foam.

  15. Graeme No.3 says:

    E.M.S. and others:
    Do NOT, repeat NOT, try to use polystyrene foam with polyster resin. The resin attacks the foam.
    Polyurethane foam as used in surfboards is OK.
    At some cost there are flexible foam sheets used in professonal boat building between layers of fibreglass which lighten and stiffen the resulting structure. Probably too expensive for occasional use, as would be end-grain balsa wood blocks.
    EMS there are catalysts which cure unsaturated polyester resins in sunlight; reliable and avoid the need to use peroxides (hardeners) and their associated hazards, but I am out of date since retirement. When designing remember polyester resins shrink when curing, which can be an advantage when wrapped around a filler and a disadvantage if they cannot grip the object.
    Hollow ‘glass’ beads have been mixed into resin to lighten the structure but the only successful one I can recall was a ‘syntactic foam’ used in a small submarine for deep sea use, something I think you should try not to be involved in.

  16. jim2 says:

    Aluminum brazing. Lot of info on the web, of course.

  17. jim2 says:

    Demo of a $114 stick welder. It worked quite well.

  18. jim2 says:

    Pop rivets might be an option.

  19. p.g.sharrow says:

    @EMSmith; Read the Cal-poly paper, Pretty much sums up the best way for an amateur to build with Polyurethane foam /polyester resin. As to your idea of wood framing, just remember that the wood must be kept dry. Damp wood will rot out in short order in a warm damp climate. I have seen plywood boats covered with fiberglass rot out in 1 season. Any wood embedded must be well encapsulated or rot resistant…pg .

  20. p.g.sharrow says:

    this will give an idea of FRP over light wood framng:
    typewriter paper, actually old tractor feed paper glued to wood and then polyester “painted” to make the shell skin. very light at this point…pg

  21. Larry Ledwick says:

    A couple of decades ago I was tinkering around with foam and fiber glass for home built structures. I was trying to build an ultra light but very strong capsule to put a radio in under a balloon for amateur radio applications. (this sort of application)

    Anyway I was dinking with foam and fiber glass and looked for a way to get the basic structure built with out dealing with resin fumes (it being winter and doing it indoors) and hit on instead of covering the foam with just white glue – which being transparent when dry it is easy to miss a spot and have the later resin application eat a hole in your foam, found that paper mache was a great solution. It is fume free, created a ridged skin that was easy to handle and then glass at a later stage.

    I took plain white glue and cut it with just a bit of water to make it a bit thinner and to increase the pot time before it was too thick to work with and started to skin over. It also more effectively wet the news paper so that it formed easily over complex curves.

    Based on that experience I would, if I built a boat use common bead board insulation, cut to form bulkheads and stringers like the way we used to build balsa wood and fabric model airplanes, then cover all those pieces with paper mache until you have finished pieces for the final assembly.

    You could easily glue in wood blocks in appropriate locations for stress points and fasteners.

    The chopped fiberglass mat is much much easier to work with if you have compound curves to cover. Woven fiberglass fabric forms well over single axis curves but is a pain on curves on more than one axis and especially on sharp bends unless you can clamp it or hold it in place until the resin begins to set.

    Another option for decking would be to pick up some salvage hollow core doors from a building material recycling place and use them as the core of your decking. They would be a bit stronger than bead board foam and have built in hard points along the edges for the hinge attachments.

    Hollow core door backed with a layer of bead board glued into a sandwich and then covered in fiberglass would be quite light and strong.

    You can fill tight interior corners with the expanding foam insulation, which you can sand and trim down after it is set to get smooth internal fillets instead of trying to get fiberglass fabric to stick to sharp internal corners with multiple bend axis.

    Another thought I had when I was investigating home built boats was to use empty 2 liter bottles for the flotation cells, bonded in place with a bit of the expanding sealing foam, so most of the buoyancy volume was just air trapped in those 2 liter bottles rather than relatively expensive expanding foam.

    Being a poor swimmer I too would insist on positive flotation cells big enough to float the boat and passengers even if the boat was completely swamped. Nice thing about the 2 liter bottles is you know each one you use represents 2 kilograms of buoyancy. If you want 100 pounds of positive buoyancy find a way to stick (100/2.2 = 45 two liter bottles in the various voids).

    You could also build a buoyant removable seat cushion out of a layer of 2 liter bottles bonded with expanding foam and then covered with an appropriate outer cover. Very light for the volume, cheap and gives you multiple independent flotation chambers so you know even if the boat gets gator bit you can’t hole all the internal flotation cells.

  22. E.M.Smith says:

    Looks like one needs to get into the specifics of a given resin, not just the class:

    from comments:

    We have a retailer here who offers a styrene-free polyester resin that is specially formulated to be used on EPS.

    though the link is now dead.

    I had roughly skimed the article dead of night and saw the word polystrene, then looking at the pictures it was very white (all urethane I’ve seen has been yellowish) and lept to a false conclusion. Ought to have read further…

    Pontoon Design Options

    Table 2 shows that the first three options are out-of-budget. The urethane core reinforced by plastic mesh and sealed with aerosol sealant would have a high drag coefficient; we also have a bigger budget than one hundred dollars that would allow us to develop a better-performing and better-looking product. The closed-cell polystyrene foam lacks stiffness and aesthetics, but was considered for a cheap alternative to full glassing. Because we would have to buy the closed-cell foam, the closed-cell design ended up being more expensive than completely glassing George Leone’s donated foam core. Thus, the urethane foam core fully fiber glassed in polyester resin is the best design

    At this point, we have verified that shaping and glassing our pontoons is the option best suited for producing a lightweight, low drag, waterproof, and cost effective design. Thanks to George Leone, head machinist at California Polytechnic University of San Luis Obispo, we have a free supply of 4 lbf/ft^3 density polyurethane foam core; hence, to keep cost low, we based our glassing decisions upon using this free foam.

    So my bad.

    It does look there are some polystyrene compatible resins and / or coatings, so specifics TBD at time of design

  23. H.R. says:

    Don’t forget about hole saws if you want to make some neat round pockets in the foam.
    This link will probably be good for a few days.

    I’m thinking foam pontoons because you can make them in halves or thirds, box the joints with wood, then put pockets on either side of the joints to access the ends of the connecting bolts.

    p.g. has graciously pointed out the problems of wood and water, so maybe foam over a wood core could be used to build a box.

  24. E.M.Smith says:

    Discussion of resin / foam compatibility here:

    Basically use epoxy resin with Styrofoam.

    For my low impact low stress slow fishing pontoon goal, I think coating the Styrofoam then using either resin (like the guy using fleece above) would be adequate, but as I have no idea the relative costs of the resins, it may be a silly thing to do. (Unless there’s a huge difference in costs, I can’t see a reason to choose the 2 step process…)

    Last seen: 1 week 17 hours ago
    Joined: 01/14/2006

    Both eps and xps are essentially styrofoam. One is expanded the other extruded. Two different processes with essentially the same chemistry.

    The “sty” part indicates that it’s styrene based. Neither one can be used with polyester resin. Poly contains styrene and is basically a solvent. That is why it melts foam. Polyurethane foam is the only one you can safely glass with polyester resin. All others need epoxy.

    “That which can be asserted without evidence, can be dismissed without evidence.

    Really like his signature line too ;-)

    Since it’s likely 2 years away before I can even think about starting a build, I have lots of time to work on design and materials specifics… At present, thinking a deck made of ~4 foot x 4 foot panels (whatever is light enough to move easy and fits in the car…), each made from aluminum angle box with aluminum waffle deck material filler, that bolt up into a platform about 4 x 8 or 6 x 8 feet. Use bolts with wing nuts to assemble, and an aircraft pin just outside each wing nut as a ‘keeper’ (so vibrations can’t loosen things much…) Then 2 x pontoons made in 4 foot sections (or whatever is the max I can fit in the Subaru… might consider car topping them) attached to the outboard edges of the platform. (IF added stability needed, put them on poles a bit further outboard as quasi-outriggers – say when testing it as a 4 x 8 kayak like build… If made with a decent attachment design, you could have 2 x box beams back to the deck and adjust width as desired.

    Maybe I’ll make a model / toy boat first… ;-) Easier to work out the kinks at 1/12 scale…

  25. E.M.Smith says:


    You can easily glass over wood. I’m figuring on a generally foam based pontoon, but with the foam glued to wood cores for load spreading to the mount point, then a wood butt panel (glassed outer surface… and bolt holes resin or varnish sealed) used to connect pontoon sections. BIG washers to spread load over wood sections.

    Likely also to put each pontoon section on a direct attach to the outer edge railing, or more likely on individual spars under the deck. P====P where P is a pontoon and the ==== is the deck with a spar under it. Think 2 or 3 of those in a row, bolted along the join lines for both deck and pontoons. Now bending forces are shared over a lever arm of the height difference between pontoons and deck, not just over the height of one set of bolts in the deck segments… Though for fore – aft forces I’d be tempted to add a set of beams running edge to edge, that violates the ‘fit in the car’ goal… so would need box beams with socket fittings on each end and more aircraft pins…

    For a flat deck trolling motor fishing platform, not much force to face. But put a real motor on it, there will be a need for significantly more stiffening of the deck, and those beams become key… I think I need to look at either car-topping 8 foot box beams, or learning more about how aircraft with removable wings do the spar attachment points…

  26. Larry Ledwick says:

    If you want to invest in a book the one to get is this one by West Marine it goes into boat building in great detail with epoxy or fiberglass resin. It obviously pushes their products but it is an excellent book on building boats, from small stuff to yachts. I bought a copy years ago when I was playing with this stuff and it was well worth the investment.–the-gougeon-brothers-on-boat-construction-book–8010100

  27. jim2 says:

    There are also a wide variety of locking pins that might make set up and break down faster and easier.

  28. E.M.Smith says:


    Ooooh! more choices than just the aircraft pins I knew…


    Where’s the fun in that? Why, with a book I’d never invent anything new. Without the book, I can re-invent dozens of things and eventually, maybe, something new. I’d also get to explore 100 and One ways to NOT do it right ;-)

    FWIW, my usual pattern is to “brainstorm” for a goodly while without following the trodden path, THEN read the reference materials, toss out the things I thought of that were wrong, adjust some of the new ideas for known good practices, then proceed. Usually gets me the best of both worlds.

    THE biggest issue I’m seeing with my proposed modular method is that there is no long strong spar taking the bending / twisting mode forces. It all ends up in the module joints. Only ways out of that I see ATM are a long strong spar carried car top, or a “modular spar” via those aircraft wing attachment methods, or trussing. I’d rather not be adding wire trusses onto an already multiple part kit. Not only does it end up looking hokey but you have lots of things to hang up, catch on, collect crap, etc. etc.

    I’m pretty sure I can make modular spar work. We see that working in things like tent poles and aircraft wings Even just using regular bridge building girder / bolt systems would work. Don’t want too many fasteners though, or it becomes a PITA operationally. So “some testing required” to get the whole thing down to minimal parts / maximal performance.

    Deck panels are pretty easy / straight forward. Biggest issue there is just not over designing them so much it is too heavy, nor under designing so much it bends… I could even see just having a line of deck down the middle or as a cross shape and the sides / corners being netting like on sailing cats. So for that it’s easy to make a panel, put it on some supports, and then jump on it. If it bends, add more “stuff”. If it doesn’t, take some off ’till it does ;-) (then back up a step or two…)

    Pontoons look like a pretty easy well established methods kind of thing with every possible material and method having been done already by someone, so mostly just picking something you like. A bit of customizing around the load spreading and attachment design. (Having the fibreglass shell take the loads and convey them to the load bearing attachment point, or put internal load spreading members?) I lean toward a bit of a hybrid with a wood top member glassed into the shell that provides the attachment point to the spars and spreads load to both interior foam and the shell. But I’d research prior art on that for better ideas. I like the way the plywood was used with slabs of foam on that low cost cat. Something like that, with water protection coated wood, and then fancier shape foam, then all glassed in / over for smooth surface, easy clean, and durability. As “out of gator height” is a big feature for me, the tall thin section is attractive. Just need a way to make it modular… perhaps as simple as a spar along the top that has modular joins at the segment interfaces. (think joist hangers or similar) and a single bolt at the lower edge (waves hands…)

    Once you have panels, modular spars, and a pontoon: the rest is just fasteners, fittings and testing the bend strength as assembled. Oh, and maybe some finishes and fencing ;-) And a lawn chair cable tied to the deck with an umbrella stand ;-)

    And a beer cold box… and a BBQ… and…

    I could see some “custom panels” with built ins for things like an ice box and BBQ holder…

    Just think of it as a Back Yard Patio with pontoons and a trolling motor ;-)

  29. E.M.Smith says:

    An interesting build of a sailing cat. Uses just plywood, construction wood (i.e. 2 x 4x) and a thin skin of fiberglass / resin over the thin plywood pontoons.

    Light enough for one person to carry it, yet 4 meter long pontoons!

    I could easily see making the pontoons as section boxes with an access up top for the bolts and a panel about 4 inches back so no water could get into the main lifting area even if some did get into the bolt access bits. Some kind of plastic snap in lid normally expected to keep water out, and rubber grommets on the bolts between sections. Or maybe glue the bolt into one so it’s always water tight and only the other has a nut access / shaft grommet issue…

    Somewhat surprised at how thin the plywood can be and still be stiff enough. I presume the glass is adding a lot of stiffness / strength. “Stitch & glue” is the method.

  30. Larry Ledwick says:

    You might want to look at the build design of the WWII mosquito aircraft and WWII PT boat for some design ideas on light weight construction adaptable to the materials you are likely to use.

    The PT boat hull was built of simple ribs covered with two layers of mahogany planking sandwiched in between those layers was a layer of aircraft fabric saturated with urea resin glue (weldwood resin glue) which requires water to cure, making it ideal for boat construction as it did not dissolve if it got wetted.

    The mosquito (and all monocoque construction used in aircraft and race cars) deals with the problem of load spreading between a light weight stressed skin and strong hard points for mounting. On the mosquito they used bulkheads skinned with aircraft plywood over a core of end grain balsa wood (modern equivalent would be foam with a fiberglass or plywood/fiberglass skin)

    The same problem crops up in auto racing monocoque construction for mounting hard points for things like engine mounts and suspension. Typically that uses a hard primary block of solid aluminum (oak in the case of wood construction) built into a stiff bulkhead structure which gradually spreads the load out over an area using larger and larger doubler plates to spread the load onto the stressed skin foam core so that it does not try to pull a plug out of the foam core structure under a high shock load.

    For example for a bolt hard point, a small piece of end grain oak fitted into a piece of light weight wood then skinned with epoxy fiberglass and at the point where you intend to bolt through drill through the oak wood plug and fit a small piece of steel or aluminum tubing epoxied in place. Then to prevent chaffing, put a top plate of aluminum or stainless steel glued to the fiberglass with a construction adhesive.

    This article shows some pictures of how ribs are laminated into the skin and core of a composite construction boat to spread the loads.

    This item gives some interesting observations about laminate core construction and thickness of the outer layer to resist normal impacts. Stating that thickness necessary to resist impacts results in little weight savings on smaller boats, where for pure strength requirements the outer skin could be very thin but easily damaged by a chance bump with a pier or debris in the water.

    The problem with hard points on lightweight fiberglass construction is the tendency of the bolt to slowly fret and chew its way through the epoxy glass top layer where all the stress is concentrated. By putting a top and bottom plate of metal on there the fastener won’t slowly eat its way through the structure as is moves under load.

    See figure 8 and 9 in this doc for what I am trying to describe verbally above.

    i always like to play with small models (my 10 year old getting back to model building I guess). You can learn a lot about design choices on a 1 inch to the foot model of what you want to build.

    As you said above one of the key design features you will need to figure out is how to build a simple to build and easy to load and unload structure that can be quickly and reliably fastened together. I personally would look at some sort of box beam spar design where you get lots of bending and torsion strength in light weight and due to the distance from the fastening points none of the fasteners will be highly loaded. Sort of like a square scaled up telescoping tent pole segment only made of fiberglass laminated wood or foam core.

  31. H.R. says:

    @ E.M.: I’m homing in on sectioned catamarans and or a kayak design with outriggers.

    I am beginning to get a handle on design and portability (Florida and Mid-west). What has been invaluable is the pointers to materials and construction techniques.

    I have a neat CAD program (Turbo-CAD) that I have used for many home projects and extensively for work tooling, fixtures, and vended parts. I’m getting closer to firing it up for a boat project. As you noted, material costs are an issue (except for pool noodle designs 😆), so I’m still working on the blend of safety, fish-ability, gator-proofing, portability, comfort, and motive power where I favor those glorified weed-whacker-to-outboard-motor designs of about 1.5hp.

    I was doing the “annual-cleaning-of-the-koi-pond” today and while running a few errands, the idea of buying a couple of Walmart $199 kayaks and joining them together popped into my woolly pate. Dual kayak transport car-topper rigs are reasonable, so all you need to design is something to connect two of the kayaks and the appropriate motive power (sails, paddles, small gas or electric motor) sun protection, and any other bling to add comfort to fishing… and a beer cooler (assumed as a matter of course) 😜

    DIY boats has been a productive line of thought on your blog; lots of links to bright ideas, cost factors, various designs, innovative joining and flotation materials (pickle buckets being one of my faves 😆).

    I am still torn between just ‘buy sumpthin’ and build something.

    The key factors remain: safety, cost, portability, cost, fish-ability, cost, comfort. and cost. Did I mention cost? 🤣🤣🤣

  32. E.M.Smith says:


    Looks like the desire for a portable boat has been around a long time, and so has a solution. From a 1915 booklet, this kid builds a folding boat. Basically three section wood boat that folds into a box made of the two rear / center sections (nose section inside)

    Actually looks easier and in some ways better than the whole pontoon thing. As long as the box is small enough to fit in the truck and big enough to support me. He does say some DIY design is needed as the 1915 drawings were more ideas than plans…

    Then this one really changed my perspective on minimal hull thickness. 5 mm marine grade plywood (so a bit under 1/4 inch at about 1/5 inch…) that folds flat (so more a car topper). Just plywood, epoxy sealant, and some assembly hardware (with a rubber facing glued onto the outside over the hinging areas).

    I don’t think I’d want to test this against a gator trying to get in it (where the box one above is sturdy enough IMHO that it would not break the boat), nor would I want to try it in rough water with a motor bigger than a trolling motor; but still, it floats, holds 2 people, and folds very flat.

  33. H.R. says:

    @E.M.: wOw! The bacon-and-gotta-have-a-boat genes have remained, unaltered, for thousands of generations.

    That is one very slick folding plywood boat.

  34. E.M.Smith says:


    Yeah, and a kid made it too… so maybe I can if I try real hard! ;-)

    One of the drawings shows the big section as 3 foot 9 inches, so I think it ought to fit in my truck. I’m ready to take tape measure to truck to set dimensions / bounds.

    I’m thinking of making one of these just to play with while working on the idea of a fishing cat. It seems big enough, and gator resistant enough (with a trolling motor it has enough freeboard and speed and with an oar to push gators away ought to be enough…) and certainly cheap enough.

    Then there’s that amusing possibility of putting it ON some eventual 8 foot Cat as a ‘spare boat’ ;-)

    I think it is time to hit the BBQ with some pork (almost bacon ;-), pop a cold one, and take tape measure to vehicle to figure the actual fit / limits…

  35. E.M.Smith says:

    Want a 52 foot yacht? Don’t want dock fees? Need to tow it behind your work truck and store it in a 20 foot shipping container? No Problem… Just fold it…

    I’m liking the way the nose is made. I could see doing something like that for the bow of a smaller boat as I rarely do anything in the bow and closed boxes would be fine (just hinges then, no need for water gasketted through bolts between bow and middle box)

    My God folks can be creative…

  36. Larry Ledwick says:

    That folding boat is a cool design, best part, is that if for some reason the sections broke apart at the hinge line, you would still have 3 float-able sections due to the full bulkheads.

    I was thinking of a slightly different way to attack that problem of nested storage with a catamaran style where each of the pontoons consisted of a trapezoid shape (narrower at the bottom wider at the top, so the two pontoons would nest inside each other when stored. (or even a trimaran to get more hull volume)

    Think of two very narrow Cajun pirogues a little narrower than this one

    Specifically designed to nest inside each other and have mounting methods for a slat deck between them with a light weight box beam front and back that also would fit inside the nested pontoons.

    Only down side is that the design would not have positive flotation cells unless you put something like inflated inner tubes under the decking (or used the box beams as flotation cells) to create enough buoyancy that it would still float even if the pontoons were fully swamped.

    Possible way around that is to form the pontoons out of thick bead board with a fiberglass skin so the total wall volume would satisfy full buoyancy along with what ever closed volume you had in the box beams under the deck.

  37. E.M.Smith says:

    Not a boat, but a camper from a boat company using DIY boat techniques. Stitch & glue teardrop.

    I think I need to learn this stitch & glue stuff… maybe right after a folder… or to lighten and toughen a folder…

  38. Larry Ledwick says:

    That stitch and glue method has lots of possibilities, I was looking at that among other methods when I was playing with this sort of project.

    You can take very light polystyrene bead board panels and as long as you don’t bend them too sharp so they break you can use it to quickly form a basic shape like those simple boats. Then you just need to cover with a durable shell material.

  39. H.R. says:


    My boat may be watertight, alligator-proof, and very portable, but my brain is FLOODED!!!!

  40. H.R. says: my 12:37 am comment above: There has been enough info presented, and more to come, I hope, that I don’t think an off-the-shelf solution will suffice.

    Boat design and construction is truly – going back multi-multi-thousands of years – a product of the needs and desires of the boat-builder.

    Now I have to design in a winch and a crane for Goliath Grouper. 😳

  41. Larry Ledwick says:

    By the way on your comment about plywood prices I recently had sticker shock when I went looking for a few pieces of plywood to build a pedestal bed. Huge jump recently.

    Apparently it is a production capacity issue (closed plants, big orders by government in the recent past and a commodity which is “must have” for builders) so there is little incentive to bring the prices down as not much replacement product competition due to its inelastic need.

    I wonder if those plant closures were driven by cost of energy increases due to green initiatives?

    It almost looks like another one of those industrial disasters due to regulatory strangulation.

  42. H.R. says:

    @Larry L.: You can depend on government ‘help’ to totally screw up a market.

    Just as a rule of thumb, cut the price of any product affected by government regulation by half to get the ‘real’ price of the product.

    Somebody is making money and it ain’t you or me.

    President Trump is aware of this and he and his cabinet are addressing the problem. The YSM is ignoring the positive effects of the elimination of unnecessary regulation and is instead is in “this is the end of the World as we know it” mode.

    Don’t even mention to me how they treat Melania. She’s arguably the best First Lady EVAH!, and all the YSM can do is push her to “Divorce Trump.”

    P.S. My wife has said I can leave her for Melania if I can woo her away from Billionaire President Trump. Go for it, said she. No doubt; I will have the best ever home-built boat before that happens, but hey! a fella’ can dream… Boat? Melania? Boat? Melania? Boat? Melania? Which is more likely?

  43. Larry Ledwick says:

    By the way apparently the girls baby name Melania is catching on and becoming a very popular choice.

  44. E.M.Smith says:

    Hmmm…. Measuring the back of the vehicles, about 3.5 ft between wheel wells. May need longer skinnier boat…

    4 sections make a Cajun Canoe and fit on rear seat… $150 or so

    This one is a bit short on freeboard for gators, and tippy with a gator paw on the gunnel… but made a bit taller and with some light out riggers (aka gator tip thwarter) might do… Also claims $150.

  45. jim2 says:

    I may never build a small boat, but the brainstorming has been fun and informative.

  46. jim2 says:

    Here’s a case of government regulation where a perfectly good and cheap wood preservative was banned and replaced by inferior and more expensive ones.

  47. E.M.Smith says:

    @Graeme No.3 :

    Do note that Florida has BOTH alligators and Crocodiles…

    The American is one of the larger crocodile species. Males can reach lengths of 6.1 m (20 ft), weighing up to 907 kg (2,000 lb). On average, mature males are more in the range of 4.1 m (13.5 ft) to 4.8 m (15.7 ft) in length weighing about 400 kg (880 lb). As with other crocodile species, females are smaller; rarely exceeding 3.8 m (12.5 ft) in length.

    So yeah, a one ton more or less crocodile of up to 20 feet long… (historical records pre-colonizing imply more like 25 feet.. but are doubted by current folks for no good reason other than nobody lets them live 200 years to find out how big they get now…)

    So don’t know if yours are bigger or not, but 6 meters and a ton makes me a bit cautious about flimsy boats with a light snack on top ;-)

    Mostly found in salt water or brackish… but I’d like to fish some of those brackish bays…

    So yes, it’s a concern…

  48. p.g.sharrow says:

    Go for the boat! I doubt you can afford the maintenance cost of a Melania.
    You probably have too much invested in your present lady to start over with a new one…pg

  49. E.M.Smith says:


    Definitely go for the boat. I agree with P.G. on this.

    The boat costs much less than any woman.
    The boat will always be ready when you are.
    The boat never complains when “you and the guys” want to spend time on the water.
    The boat will quietly wait while you finish your beer and NOT look on unapprovingly.
    The boat will not complain about your getting old, less athletic, or eating too much.
    The boat will hold you up when you’ve had a few too many, and do its best to get you home, if slowly.
    The boat LOVES to go fishing with you.
    While fishing, the boat will not complain about the smells.
    The boat will hold your beer for you, any time you like, and not drink any of it.
    The boat will not ask you about your day, nor talk to you endlessly about its day.
    The boat will not ask you if you still love it; it knows you do…

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