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Thread: Lightweight construction method advice

  1. #1
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    Default Lightweight construction method advice

    Hello all,

    I have done a few searches and haven't come up with any previous threads that ask this question directly, but please forgive me if I've missed one somewhere.

    I have been thinking lately (I suppose "daydreaming" may be more apt) about a pleasure rowboat for use on small lakes, larger lakes, and in fine weather inshore on Puget Sound. Something like the Rangeley boat from BCSC or perhaps a Rushton model 109 or guideboat.

    The ideal would be for two adults - one rowing and one lounging - or an adult and two or three small children. Essential, due to water access restrictions (i.e. no ramp), would be light weight for launching off a beach. Or rather, for conveying the boat from the car or trailer to the beach for launching.

    It seems like there are three possible building techniques that would be suitable: strip planking with perhaps 1/4" stock and inside and outside glass layers, light (3mm or 4mm) glued ply lapstrake (with or without frames or stringers), and skin on frame. There may be other methods that would work as well.

    If this were your project, which method would you choose and why?

  2. #2
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    Default Re: Lightweight construction method advice

    Strip planked with 3/16" planking of western red cedar.
    60z on both sides, but it could be 4 oz.

    I like smooth boat hulls with nice flowing lines.
    I also don't like 100 little ribs - difficult to keep clean or refinish.
    Strip plank doesn't take very long if you will accept paint.
    If you want wood look, that takes lots more pickyness and some extra time.

    Note that 3/16 requires you use formers spaced at 12" or less to get it smooth without lots of problems. 1/4" should be less of an issue, just a little more weight (12" former spacing recommended).

    Just my HUMBLE opinion.

  3. #3
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    Default Re: Lightweight construction method advice

    ^ good solution. Glued clinker ply with internal 'poxy fillets is light and strong, does not need ribs and can be varnished bright. Probably needs fewer formers in the build jig.
    It really is quite difficult to build an ugly wooden boat.

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    Default Re: Lightweight construction method advice

    Diagonal cold-mold using cedar. Skinned with 3-oz 90-deg biaxial 'glass fabric in System Three Silvertip epoxy. Quite possible (depending on hull size & form) that there will no need for any internal framing. Labour hours will be high, though, the build will be fussy, and the expense of building a jig will not be insubstantial. But you will have the strongest, stiffest, lightest wooden hull you can create.
    Hope for the best, but plan for the worst.

  5. #5
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    Default Re: Lightweight construction method advice

    Quote Originally Posted by mmd View Post
    Diagonal cold-mold using cedar. Skinned with 3-oz 90-deg biaxial 'glass fabric in System Three Silvertip epoxy. Quite possible (depending on hull size & form) that there will no need for any internal framing. Labour hours will be high, though, the build will be fussy, and the expense of building a jig will not be insubstantial. But you will have the strongest, stiffest, lightest wooden hull you can create.
    Tricky to create a wine glass transom which will be a slippery double-ender underwater whilst having the width of a transom for seating in the stern-sheets. But otherwise, as light and strong as any other.
    It really is quite difficult to build an ugly wooden boat.

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    Default Re: Lightweight construction method advice

    But not impossible. I built a 16-ft x 7.5-ft catboat hull with wineglass transom using the materials described. The hardest part is getting really thin veneers in quantity at a decent price.
    Hope for the best, but plan for the worst.

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    Default Re: Lightweight construction method advice

    Quote Originally Posted by mmd View Post
    But not impossible. I built a 16-ft x 7.5-ft catboat hull with wineglass transom using the materials described. The hardest part is getting really thin veneers in quantity at a decent price.
    The demise of the veneer sources seemed to kill amateur building of small cold molded boats maybe 20 years ago.
    Are any left?

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    Default Re: Lightweight construction method advice

    Quote Originally Posted by JimConlin View Post
    The demise of the veneer sources seemed to kill amateur building of small cold molded boats maybe 20 years ago.
    Are any left?
    May have something to do with this kind of influence on the import / trade in tropical woods:

    https://www.woodworkingnetwork.com/n...-investigation

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    Default Re: Lightweight construction method advice

    I built this Rushton pulling boat around 15 years ago from plans I got at the Adirondack Museum at Blue Mountain Lake. I lengthened it from (I believe 14'4") to 15' and adapted it to glued lap. I used 4mm okoume marine ply, no ribs. Spanish cedar for the decks and philipine mahogany for the seats and trim. Boat weights 80 lbs. It has three seats and two rowing stations. Oarsman can sit in the center when alone or with two passengers or can row from the bow seat while one passenger lounges in the stern seat.
    IMG_2339.jpg
    I was born on a wooden boat that I built myself.

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    Default Re: Lightweight construction method advice

    ^ I should add that I put floors in it to stiffen up the bottom and support floor boards.
    I was born on a wooden boat that I built myself.

  11. #11
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    Default Re: Lightweight construction method advice

    The Rushton looks good.
    Did you expect 80#?
    I just haven't looked at boats of this type.

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    Default Re: Lightweight construction method advice

    I'd go with frameless glued lap ply. It'll be stable, easily maintained and won't require fairing. Add to that that you won't need to protect the epoxy from UV. The outside is easy enough to fair, especially on a small boat, but the inside is painful, and very time consuming. I'm truly and thoroughly tired of fairing.
    Last edited by Gib Etheridge; 07-15-2020 at 11:50 PM.

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    Default Re: Lightweight construction method advice

    [QUOTE=Rich Jones;6230436]I built this Rushton pulling boat around 15 years ago from plans I got at the Adirondack Museum at Blue Mountain Lake. I lengthened it from (I believe 14'4") to 15' and adapted it to glued lap. I used 4mm okoume marine ply, no ribs. Spanish cedar for the decks and philipine mahogany for the seats and trim. Boat weights 80 lbs. It has three seats and two rowing stations. Oarsman can sit in the center when alone or with two passengers or can row from the bow seat while one passenger lounges in the stern seat.
    IMG_2339.jpg[/QUOte

    That's beyond plain old everyday gorgeous Rich, it's an exquisite work of art. +

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    Default Re: Lightweight construction method advice


    This is "Fine" 1/4inch cedar strip 4 oz cloth in and out. Beech trim, sliding seat rack and aluminum rigger. 18 foot LOA and 34 inch beam. Set up with "jump seat" for a passenger, Rigger and seat remove, this hull came in at 62 lbs. I row this year round in Pender Harbour, averaging 4+ knots and can peak over 6. It could be lighter if you left out the flotation bow and stern, but would loose a bit of security. I built the first one to have a boat for fitness that I could cartop on my VW van, and launch by myself. I have been thinking about 3/16 strips, or maybe a self-bailing version, but haven't got there yet.
    oysterbayboats.ca

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    Default Re: Lightweight construction method advice

    Hi,

    what about a 2 sheet Flywood?

    http://forum.woodenboat.com/showthre...Flywood-Family

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    Default Re: Lightweight construction method advice

    My suggestion would be glued clinker hull if you want light & strong. But be aware that there is a very big difference between the different types of plywood available. I have a strong preference for Bunyzeel ply because of its quality, lightness and strength, Hoop pine ply is about twice the weight of Brunyzeel). I can lift the stern of my 14' 6" Gannet with 1 hand and I am not a strong person I can assure you. Have a look at lots of designs (I like Iain Oughtred and Alan Payne, others like Gartside), decide what you key selection criteria are and which are top<>low priority, and if you can (?) make an objective choice...................... Good Luck.

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    Default Re: Lightweight construction method advice

    Nobody has mentioned Skin On Frame?

    Here's one of Dave Gentry's that might fit the bill... but there are others out there --

    http://gentrycustomboats.com/Whitehallpage.html

    David G
    Harbor Woodworks
    https://www.facebook.com/HarborWoodworks/

    "It was a Sunday morning and Goddard gave thanks that there were still places where one could worship in temples not made by human hands." -- L. F. Herreshoff (The Compleat Cruiser)

  18. #18
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    Default Re: Lightweight construction method advice

    Quote Originally Posted by Rich Jones View Post
    I built this Rushton pulling boat around 15 years ago from plans I got at the Adirondack Museum at Blue Mountain Lake. I lengthened it from (I believe 14'4") to 15' and adapted it to glued lap. I used 4mm okoume marine ply, no ribs. Spanish cedar for the decks and philipine mahogany for the seats and trim. Boat weights 80 lbs. It has three seats and two rowing stations. Oarsman can sit in the center when alone or with two passengers or can row from the bow seat while one passenger lounges in the stern seat.
    IMG_2339.jpg
    Your boat is one of the ones that inspired this daydream. 80lbs is a touch heavier than I was imagining - how do you think this boat would work out with 3mm ply?

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    Default Re: Lightweight construction method advice

    Quote Originally Posted by upchurchmr View Post
    Strip planked with 3/16" planking of western red cedar.
    60z on both sides, but it could be 4 oz.

    I like smooth boat hulls with nice flowing lines.
    I also don't like 100 little ribs - difficult to keep clean or refinish.
    Strip plank doesn't take very long if you will accept paint.
    If you want wood look, that takes lots more pickyness and some extra time.

    Note that 3/16 requires you use formers spaced at 12" or less to get it smooth without lots of problems. 1/4" should be less of an issue, just a little more weight (12" former spacing recommended).

    Just my HUMBLE opinion.
    I was actually thinking that I'd prefer paint for this project - I have more experience with paint and feel more comfortable with its maintenance. It also seems like varnished wood gets awfully hot in the sun; fine for trim, but I don't know that I'd want the entire hull to be that way.

    Is there any reference book you'd recommend for strip planking in this way? Would it produce comparable weight to the 4mm ply in, for example, Rich Jones' boat above?

  20. #20
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    Default Re: Lightweight construction method advice

    We used to build 36" wide canoes using 3/16" thick strips (usually sitka spruce or redwood) and six ounce cloth doubled over the bottom, both inside and out. It made a boat that would hold its shape and have good durability without the need for other interior hull structure. Going much wider, or lighter than that for the glass layup tended to make boats which exhibited a lot of bottom bounce - which is eventually (or sometimes more like instantly) the kiss of death for a stripper. It can result in longitudinal cracks and splits either down the grain lines or the strip joints. Some sort of internal half ribs or other bottom cross-grain stiffening may be needed to prevent this on wider hulls or those built with reduced layup schedules. It is also the reason that the new builder's frequent idea to reduce the inside glass layup to save weight is a huge mistake which very often results in a broken boat.

  21. #21
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    Default Re: Lightweight construction method advice

    Nick Schade has two books on strip planking. His ideas change a little between the first and last, but not a lot.
    He also has extensive how to build videos on his website - https://www.guillemot-kayaks.com/information
    He has a website for his business of personally building kayaks for sale - check this out if you want a very high standard to try to duplicate. http://woodenkayaks.com/

    The laughingloon.com website is another strip planked website and the author (Rob Macks) has an extensive section on how to build. If you go here you might find one of my kayaks. My son is posed with a 18' 4" bidarka on one of the "customer built" pages. The boat is leaned up against a tree vertically, so it is easy to recognize. This is about the hardest kayak I have ever built - not for a first timer.
    https://laughingloon.com/north.star.html
    Another owner built comment on the same boat - http://etiennemuller.com/northstar/N...ncereview.html
    And 100 pictures of that build = http://etiennemuller.com/northstar/index.html

    The north star kayak was approx 52# (I don't know exactly). Using 3/16" cedar and 1 ply 6 oz inside and out.
    But a kayak is much narrower and less height than the boats you are talking about.
    3/16 cedar is .1875 thick while 4mm is .160. But ply is heavier density.
    I really don't know what the weight comparison would be.

    If you choose strip plank, I always suggest making a "nose" to practice on. That being about 4' of the bow of the boat. It doesn't take up much space, or cost much. You can fiberglass it and learn maybe 85% of the techniques for the boat, without making mistakes on your pride and joy. For a kayak, the wood required is about 2 each 2x4's.
    I have two of them hanging in my garage - I call them my moose heads (like hunters trophy's). 2 more in the attic.

    Natural finish wood does not get noticably hot in the sun. My kayaks never bothered me in the Texas summer sun.

    Last comment: Listen to anything Todd Bradshaw says. I do, and I don't believe anybody (very often).

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    Default Re: Lightweight construction method advice

    I think it depends on your experience, you can build light with strip plank and glass BUT if you new to building you will add extra weight and ply stick and glue will be easier to get light.

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    Default Re: Lightweight construction method advice

    Tink,

    What is "ply stick and glue"?

    Maybe I just don't recognize the method. Did you mean "ply STITCH and glue"?

    Why do you think Strip planked could be heavy if you are not experienced?

    Of course, anything can be botched up.

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    Default Re: Lightweight construction method advice

    Quote Originally Posted by pandelume View Post
    Your boat is one of the ones that inspired this daydream. 80lbs is a touch heavier than I was imagining - how do you think this boat would work out with 3mm ply?
    The boat is very stiff with the 4mm ply. 3mm might be OK, but I won't be the one to tell you to go ahead with it. I was looking for lightweight and feel the 80 for a 15' rowing boat is good enough. I always knew I would have to trailer it. At age 67, throwing things on top of my car is in the past!.
    I was born on a wooden boat that I built myself.

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    Default Re: Lightweight construction method advice

    The ideal would be for two adults - one rowing and one lounging - or an adult and two or three small children. Essential, due to water access restrictions (i.e. no ramp), would be light weight for launching off a beach. Or rather, for conveying the boat from the car or trailer to the beach for launching.
    I got a boat that does most of that -

    SAM_6321.JPG

    It's fine for rowing with two adults, but is to small for three kids!

    48246250821_b952ac6152_o.jpg

    It's Nothing fancy, just a Payson/Bolger style "Instant Boat", call it stick, ply and glue construction if you will, very easy and fast to do.
    The Instant Boat method is a good idea if you want to use the boat this summer, because you can make one in in a couple of weekends.

    Any reasonably light plywood boat can be easily wheeled down to the water with a dolly on the transom.
    Mine is nothing more than a 2x4 with lawn mower wheels stuck on the ends, connected to my curved transom with a single bolt and wing nut.
    Makes car-topping easier too. Wheel it up to the car, put the bow on up, push the back of the boat as close to the car as it will go, then lift the stern up and push the boat into place on your racks.

    You don't want a double ender for this - Way to hard to car-top and rig a dolly for.

    I prefer plywood for this mission, ( either Instant Boat style like mine, or lapstrake or stitch-N-glue ) because a plywood boat is light, tolerant of the abuse of beach launching, and easily repaired!

    For specific recommendations, I think one of Jim Michalaks rowboats would work very well -

    Roar 2 is 14' x 42' x 75 lbs.



    https://www.duckworks.com/product-p/jm-roar2.htm


    I think maybe his 14', 60 lb "Robote" would work too, and if you want to pull two sets of oars his 18', 90 lb. "RB42" would work fine.

  26. #26
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    Default Re: Lightweight construction method advice

    Stitch and glue yes

    First time you strip plank you are going get more gaps in the planking, get a less fair hull and use more filler. To laminate the glass over that area without experience you I doubt you will get a good wet out without adding extra resin

    With stick - that was spell check changing- stitch and glue there are areas of relatively small glass and filleting. Getting the tape wetted out is much easier. Cut the tape weigh it, mix that amount of resin plus a small amount to pre coat the area. I then actually wet out on a glass table, and roll up and apply. Then peel ply. Very easy optimal joint. Regardless with stitch and glue most of the area of the hull is as it was when bought, a thickness of ply and so weight not added.

    I admit I havenít built a stripper but researched pretty heavily. Have built ply boats and they are always light.

  27. #27
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    Default Re: Lightweight construction method advice

    Stripper building isn't that difficult if you can work carefully and follow directions (folks often seem to have more trouble with the follow directions part than the work carefully part - they try to get creative and improve or reinvent the wheel without ever rolling one). There is no reason though, to assume that the boat won't turn out OK and with reasonable weight, strength and performance for a good first time builder.

    Whether or not it is a ideal construction method for a particular type or design of boat to build that way is another question. My wood strip/fiberglass drift boat (late 1970s) was a good example. I had heard that Wonnacott (one of the leading strip builders of the day) had built one and I thought "Gee, I've always wanted one of those and if he can build one, so can I." So I did. It worked, and was pretty, but considering that it could have been easier to build and probably a more practical and still pretty boat from a good mahogany-like marine plywood it's hard to think of it as a total success.

  28. #28
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    Default Re: Lightweight construction method advice

    So far there doesn't seem to be much interest in "Lightweight".

    I'd not call any 52lb kayak light - the heaviest one I own is perhaps forty pounds and the lightest well under twenty.

    No mention of Skin on Frame - see Here
    I'd much rather lay in my bunk all freakin day lookin at Youtube videos .

  29. #29
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    Default Re: Lightweight construction method advice

    Quote Originally Posted by Rich Jones View Post
    The boat is very stiff with the 4mm ply. 3mm might be OK, but I won't be the one to tell you to go ahead with it. I was looking for lightweight and feel the 80 for a 15' rowing boat is good enough. I always knew I would have to trailer it. At age 67, throwing things on top of my car is in the past!.
    Fair enough - I was just looking for an opinion. I certainly wouldn't think of blaming you for my choice of planking

    I also have a feeling that car-topping is probably unrealistic; a light trailer is probably the right way to go. The only downside is that lots of the hand-launch parks have no trailer parking.

  30. #30
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    Default Re: Lightweight construction method advice

    I much appreciate all the feedback. The advice to look at Dave Gentry's and Jim Michalak's designs is well taken. Gentry's Shenandoah Whitehall is something I have seriously considered.

    I also think the SOF Rushton rowboat from Dreamcatcher Boats is a contender:

    home_image4.jpg

    https://boat-building-plans.com/boat-plans/

    I should note that the plans description states 45lbs, but I have been advised by the website proprietor that it would more likely be around 65lbs. SOF seems like a construction method that wouldn't deal well with rocky beaches or barnacles; although you wouldn't drag the boat up the beach, when you launch and return you inevitably touch the ground. But I understand that many people get good service from boats made this way, so I am likely wrong about its durability.

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    Default Re: Lightweight construction method advice

    Quote Originally Posted by upchurchmr View Post
    Strip planked with 3/16" planking of western red cedar.
    60z on both sides, but it could be 4 oz.

    I like smooth boat hulls with nice flowing lines.
    I also don't like 100 little ribs - difficult to keep clean or refinish.
    Strip plank doesn't take very long if you will accept paint.
    If you want wood look, that takes lots more pickyness and some extra time.

    Note that 3/16 requires you use formers spaced at 12" or less to get it smooth without lots of problems. 1/4" should be less of an issue, just a little more weight (12" former spacing recommended).

    Just my HUMBLE opinion.
    great

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    Default Re: Lightweight construction method advice

    SOF is really not delicate.
    The biggest risk is dropping or hitting a frame member on a rock hard enough to crack it.
    The skin is very tough unless you cut it with a very sharp knife or something in the water.
    You can see utube videos of people hitting the skin with hammers or dull knives and never hurting it.
    I suggest around 8 oz polyester, the 3oz used by one designer is made for aircraft where you don't hit rocks, etc.
    Even then others have said it is just fine with a little care, and depending on your area.

    It should be lighter than strip planking. All my kayaks were. Trust Gentry on the weight for his boats. Assuming you don't "improve" the design.

  33. #33
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    Default Re: Lightweight construction method advice

    Quote Originally Posted by pandelume View Post

    I also think the SOF Rushton rowboat from Dreamcatcher Boats is a contender:

    home_image4.jpg

    https://boat-building-plans.com/boat-plans/

    But I understand that many people get good service from boats made this way, so I am likely wrong about its durability.
    Depends on what you put on the skin. Coat the skin with Corey's Goop available from the Skin Boat School. The most durable coating available. Been described as rhino hide. Sharp rocks shouldn't do any damage but try and avoid the oyster shells.

    https://shop.skinboats.com/2-Part-Ur...Skin-goop1.htm
    Last edited by Woody Jones; 07-17-2020 at 03:28 PM.

  34. #34
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    Default Re: Lightweight construction method advice

    So I just reread the chapter in Building Classic Small Craft on the Herreshoff rowboat and the McInnis bateau. These are both boats that seem close to what I'm looking for - particularly the McInnis boat. Gardner's version has a 3/8" ply plank bottom, six 3/16" ply strakes per side, and laminated frames every 6 inches or so. Instructions call for epoxy gluing and clench nailing through the laps and frames.

    From what I understand of glued ply lapstrake construction, this is overkill. Gardner estimates ~90lbs for the finished boat, which seems on the high side.

    The original version drawn by McInnis was a multichine with 1/4" ply bottom, 3/16" sides and seam battens on the inside of the chines. According to Gardner it weighed ~60lbs. This is closer to the weight I'm looking for, although I believe Gardner's version will make a prettier boat.

    What do those with lightweight boatbuilding experience think of these methods of construction? I'm wondering whether it might work well to build Gardner's version with laminated frames and stringers - perhaps three or four - instead of the ply planking, and then skin each side with 8oz polyester. This would give a solid bottom for beaching, and seems like it should be lighter - lighter still if I use 1/4" ply instead of 3/8". I'm sure this has been done before - I recall a previous thread where someone had a SOF pram with a solid plank bottom - but I'm not sure how successful it has proven to be. Thoughts?

    Here's a photo of this boat that I found on the internet:

    Mayenburg_A_5_26_0101.jpg

    Source: https://www.woodenboat.com/boat-launchings/shaunti

  35. #35
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    Default Re: Lightweight construction method advice

    In the era when John Gardner was writing his excellent books we had a lot less experience of using epoxy.There have been numerous boats built with epoxy as the only thing holding the boat together and no mechanical fastenings at all.Unless you local beaches feature lots of rocks I would think it preferable to add a couple of 7/8" X 5/8" bilge keels along the edge of the bottom panel.I have read Pete Culler's objections to bilge keels that aren't parallel to the keel and have difficulty believing that the flow along the outboard edge of a bilge panel is parallel to the keel either.I would think it would be easier to build the McInnis multi chine version than the glued clinker version with 3/16 ply,mainly because the chine stringers will do much to stiffen the hull.The clinker version will be a bit more challenging to fit a thwart riser to and it will be the thwarts that give stiffness to the boat.Decent thwart knees will help and I would have four stiffening strips on the bottom panel,more or less equally spaced.

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