Of Wooden Boats and Weight Capacities

Discussion in 'Boat Design' started by YotaTruck, Jul 16, 2014.

  1. YotaTruck
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    YotaTruck Junior Member

    I'm looking at building a simple nail and glue skiff for the purposes of puttering around on local lakes and rivers with the family. With little ones on board safety is paramount, though I guess it should be no matter who is on board, right? One of the boats I'm considering is the Bolger/Payson Work Skiff 18:

    http://www.instantboats.com/skiff18.htm

    It's about as simple as it gets. My question is regarding safe loading. It's hard to see, but the study plans do show a water line at 1100lbs displacement on the top right. Accurately extrapolating the scale from the screen is impossible, but if I had to guess I'd say maybe 3-4". However, given the materials used-14 sheets of 1/2" plywood, 60' of 2 x 6 lumber, five gallons of resin, and 13 yards of 50" 10oz cloth, the boat itself must weight about 1000lbs. What would be considered a safe load for a boat like this? I would estimate that my crew weight (Me, wife, two year old, four year old, 70lb dog) would be just under 600lbs. Throw in gear, a cooler, outboard, etc...and that's probably another 400, so total weight would be 2000lbs. I've ordered Payson's Instant Boats book-does anyone know if there are guidelines in there on max loading?
     
  2. Tad
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    Tad Boat Designer

    It will take about 390 pounds to sink this boat (level) one inch in fresh water. The sides appear to be about 18" high, reducing that to 15" is a lot. If you are using the boat in flat water it will be fine, but for open water, say a mile across a lake or so, I would look for a higher sided boat.
     
  3. YotaTruck
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    YotaTruck Junior Member

    Thanks-that at least gives me some idea. The boat will be used on flat water/nice days, but two of the lakes we go out on are relatively large (2 miles across or so), which is part of what gives me pause. A very closely related design from Jim Michalak (a designer heavily influenced by Bolger) is the AF4 Casa, which is 18' x 6', so a bit wider/more displacement:

    http://www.duckworksbbs.com/plans/jim/af4casa/index.htm

    The scantlings on AF4 Casa are much lighter than Work Skiff 18 (350lbs empty) and sheer height is 24". Also, I had thought about adding a shoe to it similar to the one on the Work Skiff which will also add some displacement in addition to stiffening the bottom. Would you say that this boat would be the better choice given my intended use?
     
  4. NavalSArtichoke
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    NavalSArtichoke Senior Member

    Dang, what are you building, a skiff or an Ark? By the time you get yourself, the wife, the kids, the dog, the TV, the fridge, a cooler of beer, a motor, gas, steering, BBQ grill, generator, etc., 18 feet isn't going to cut it. And don't skimp on the PFDs for all the people and critters going on your little odyssey.
     
  5. Rurudyne
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    Rurudyne Senior Member

    A yacht is just a superbly finished skiff with room for everyone's stuff...
     
  6. YotaTruck
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    YotaTruck Junior Member

    Hence the reason I'm looking for advice from folks more learned than I on the subject. It's hard for a layman like myself to know what kind of load a boat can safely handle since few designs include such information. Some list maximum displacement, but that's not really very helpful considering that number represents how much weight is required to sink the boat to the gunwhales. Also, I have heard from other folks/seen pictures of plenty of boats about this size with families of four aboard plus gear, and yes, even a dog. Granted, those people may have been operating outside the limits, but then again maybe not. I will say that the boats I've seen did not look as though they were hurting for freeboard.

    With regard to what we're bringing with us, (what I referred to as "gear") I think you're overestimating (I probably was too). First of all, no beer-these are state park lakes. Cooler is for water and snacks. Maybe 25 lbs. The rest of the gear would be basic safety stuff-First, PFDs would be counted in crew weight because we wear them at all times-no exceptions. The rest would be the usual-extinguisher, tool kit, air horn, first aid kit, 15lb anchor plus line, and everything needed for a 15HP tiller with external fuel tank. And some fishing poles.
     
  7. tom28571
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    tom28571 Senior Member

    Although it is heavy for an 18' skiff, I think you have probably overestimated the weight of the boat. There is a good percentage of waste plywood and lumber in building a boat. Scantlings of this skiff appear suitable for an ore barge. Doesn't Bolger give a hull weight?

    It does look big enough for the expected load to me. There are a number of AF4's around and people seem happy with them.
     
  8. YotaTruck
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    YotaTruck Junior Member

    I probably did-I took the weight of square foot of 1/2" plywood and weight per foot of a 2x6 and simply multiplied by the quantities specified. For the epoxy/cloth weight I was guessing. The weight of the hull for Work Skiff 18 is not given on the study plans, but it may contained within the full plans. I've ordered the book so I'll see soon enough. Not sure if you caught it above, but Michalak gives the weight of AF4 Casa as 350lbs empty, but he is using 1/4" side planking as opposed to 1/2", the transom is not nearly as heavy, and there is no shoe like on Work Skiff 18, but I would plan to add one.

    I've seen plenty of AF4s (with cuddy, etc...) loaded down with four people (even four full sized adults) and plenty of camping gear which is what I was referencing before. The AF4 Casa is about 200-300lbs lighter than AF4 I believe.
     
  9. messabout
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    messabout Senior Member

    YT when a designer states the displacement, it is the displacement (or total weight) of the boat, occupants, and gear that allows the boat to run on its' designed lines. Displacement quotations are NOT the immersion up to the gunnels as you may have surmised in your post above.

    The Bolger work boat is what it says it is. It is designed to survive long term abuse and neglect that a work boat is likely to endure. Almost surely not the best choice for a family boat. The boat is butt ugly but it will be a reliable one and more than a few of them have survived an arduous existence. It is way too heavy for practical use as a trailered boat.

    Do not let the apparent simplicity of that box like construction con you into accepting it because it looks easy. Well, yes it is easy to build but a better looking and perfectly safe family boat is not much, if any, more difficult.
     
  10. YotaTruck
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    YotaTruck Junior Member

    I have actually seen displacement as you're describing it listed as "Displacement at design water line." Bateau puts this on all their study plans.

    You're talking to a guy whose favorite kind of boat is a Garvey (spent time in many on Barnegat Bay as a kid)-for some, simplicity is elegant. I am looking for a boat that will take my family to some of the more wild places on the lakes and rivers around here that not many people see because they're harder to get to. The boat is going to cart us across the lake, or to an island in the Delaware, beached on a rocky shoreline, and will eventually be tramped upon by muddy, happy, tired kids after a day of exploring, fishing, picnicking, etc...

    AF4 Casa has not been built yet to my knowledge, but here's a picture of a nicely done Work Skiff 18-can you really say that's not a good looking boat? Plain, for sure, but not ugly IMHO:

    [​IMG]

    In the time it took to post this I actually got a response from someone on the Duckworks Yahoo group about the particulars on AF4 Casa. The plans specify a 6" draft at 2000lbs-with the shoe added it should be slightly less, plus my load will only be about 1600lbs. With a 24" sheer height a 6" draft will leave me 18" of freeboard, worst case scenario. Does that sound adequate?
     
  11. messabout
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    messabout Senior Member

    YT:I take back my remark about the boat being butt ugly. The one in the picture is looking pretty good but it is still far short of glamorous. That it is serviceable is beyond question.

    For the record, I am a fan of simple flat bottomed boats such as the one pictured. Matter of fact my 16 foot sail boat is a sharpie/flattie which pleases me no end.....It is painted and varnished to a fair-thee-well but it is still not very pretty by the standards of the day.
     
  12. YotaTruck
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    YotaTruck Junior Member

    Fair enough-far short of glamorous definitely describes the boat well but glamorous ain't exactly my style :D For me it's not really about the boat itself, but rather the experiences and memories the boat will facilitate.
     

  13. Petros
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    Petros Senior Member

    I think anything with fair lines, and lots of varnished wood ("bright" finished as they say) looks good. Even though painting is more practical, for some reason when the natural grain of the wood, even in trim and non-esseitial structure, it somehow evokes a very pleasing and satifying emotion in most that look at it. So rather than justify it with it costs vs. benefits, etc. if people ask, I say I used wood because I like the look.

    wood is a great material, renewable (trees grow back), recyclable (or "re-purposed" from salvage lumber piles, and cheap!), it is mass produced by unskilled labor, it is easy to work with simple hand tools, non-toxic, takes no costly tooling, but most of all, it looks the best when done!
     
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