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Thread: Construction method costs

  1. #1
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    Default Construction method costs

    In the very early stages of designing a 12’ x 3’ Peapod, I am wanting something light but also cost effective.

    I am fully aware SOF will probably be the lightest and probably the cheapest but want to understand other methods also

    I have made a very rough calculation of material requirements based on just the timber requirements - core material for strip plank and just the plywood for stitch and glue.

    For Strip the core comes out at £500 - US$670
    For S&G the ply comes out at £250 - US$335

    So the question is does the base material of a strip planked boat cost double stitch and glue and I sure further increases when all materials taken into account and certainly if labour included.

    Are these calculations in line with other people’s experience, I would love to build a strip boat just for the aesthetics and I haven’t before

  2. #2
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    Default Re: Construction method costs

    Why are you counting labour costs? Are you a commercial business? If not, then why count labour? Your doing it as a hobby after work.
    Otherwise you better write yourself out an invoice when you watch TV at night. LOL

  3. #3
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    Default Re: Construction method costs

    Sorry for confusion, I am not including labour just saying if I did it would further increase the additional cost of strip plank relative to other methods

  4. #4
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    Default Re: Construction method costs

    I would like to see a detailed description of the material list. Looks like you will buy wrc strips for core or topquality plywood considering what you will spend on materials. Did you include Peel-ply? I myself am invariably too optimistic about material costs and building time.

  5. #5
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    Default Re: Construction method costs

    There may not be much difference in the cost if comparing sawing your own strips vs quality ply. It might be better to ignore cost and focus instead on the design, then choose the most suitable method. Strips for a smooth round hull, ply for a not so round one. If you have a hankering to try strip plank then you should. It is time consuming, but not hard, and definitely satisfying to see the completed hull. If you just want to knock out a boat really fast, it would be hard to beat ply.

  6. #6
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    Default Re: Construction method costs

    Just a reminder - designing your own boat and 'cost effective' seldom coincide. Prototyping is not an inexpensive process.
    David G
    Harbor Woodworks
    http://www.harborwoodworking.com/boat.html

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  7. #7
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    Default Re: Construction method costs

    ah, i see that you are in England, thats why the WRC is so expensive.
    if you are wanting to go with WRC, contact me, i will see what i can do for you.
    WRC prices are through the roof right now, and clears even more so, but i live in WRC and Alaskan yellow cedar country- i am sure we could work out something for you.
    I probably have 20 plus WRC logs at least 5' in diam sitting in my yard right now.

  8. #8
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    Default Re: Construction method costs

    Thanks one and all for the replies, I am still at the very start of the design phase. Will work up some models of ply and strip planked and see where that leads me. Other projects to complete and boats to sell before I am close to a build.

  9. #9
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    Default Re: Construction method costs

    I went down the same path with a dinghy idea. I came to the conclusion that a multi chine ply build would be both cheaper and faster than strip plank. I did not calculate the SOF option as the boats girth was bigger/wider than the availiable cloth, and i did not want to have a join, and all the waste. The built in stowage /bouyancy was the benefit of the ply hull over the extra cost of float bags on a SOF. Im yet to build it. Round bilge might suit some deigns better than others, no reason you can not do the bottom in strip and a couple of lap planks on top.

    EDIT: Multi chine, as in glued lap or on a batten, not stitch and tape.

  10. #10
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    Default Re: Construction method costs

    If you design for ply construction the panels of the hull will have to be 'developable' unless the boat has narrow, light planking which can be 'tortured' into place and fastened. It's not as easy as you might suppose and making small scale models out of thin modeler's plywood will help.

    "Developed plywood construction

    Developed plywood construction is an excellent method of hull construction. With this method, you can produce very lightweight, strong hulls. In certain cases it can minimize lofting, setting up and laminating, so a boat can be built in fewer work hours. A very thorough description of this building technique can be found in Chapter 23 of The Gougeon Brothers on Boat Construction.

    In this construction method, plywood panels that become the hull can be cut to a designed shape. Second, they are temporarily joined so the two panels can be opened like a book. The panels are then bonded permanently to a specific angle.
    With some designs, plywood is compounded or tortured, bent in two directions at once and forced into shape. Stitch and glue panels are bent in one plane and joined. Rigidity is gained by the joined panels meeting at an angle."
    If I had a dollar for every girl who found me unattractive, eventually they would find me attractive.

  11. #11
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    Default Re: Construction method costs

    The cabin roof on the Welsford Pathfinder is spec'd (from memory) in 20mm thick cedar strip with two layers of 6oz glass each side.
    If I was building again, I'd go for two layers of 9mm ply, with one layer of 6oz glass each side. It would be half the cost, probably take a third of the time to build, and I don't think it would give away much of anything, in terms of finished weight or strength.
    I started with 25mm thick rough sawn cedar planks, and was gobsmacked by the bill - I was that close to asking the timber yard to put it back on the rack.
    Pre made strips would have been even worse, so yes, I can completely believe the OP 's numbers for s&g vs strip.

    Pete
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  12. #12
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    Default Re: Construction method costs

    A 12’x3’ Peapod is really small. Those dimensions are more like a tiny canoe.

  13. #13
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    Default Re: Construction method costs

    I am after something light for cartopping for quick trips on inland waters. It is a stealth boat, quick to get from storage to the river, a few hours pottering and back again before the family have realised I have gone.

    I like the look of Arch Davis 12ft Peapod

    http://www.archdavisdesigns.com/davis_peapod.html

    Just realised the typo in the OP
    LOA 12ft
    Beam 4ft
    Depth Midships 1ft 5inches
    - sorry for confusion one and all.
    Last edited by tink; 06-15-2018 at 07:29 AM.

  14. #14
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    Default Re: Construction method costs

    yup, i truly feel for you guys, By the time you get your hands on the cedar, its been through so many hands, the loggers, the log snake ( log buyers) the mill,then a distributor, then the shipping company, finally the retail outlet. and each and every guy along the way is making a sizable chunk of change.
    Good tight/clear WRC direct from the small mill in town costs 2000/1000- so thats $2000canadian per 1000 board feet. so for a peapod of the dimensions above- one should get away with change out of $100. thats not accounting for the decking and thwart etc, that was just material for strips.

  15. #15
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    Default Re: Construction method costs

    For car-topping this size and weight is much the easiest and quickest without help or special arrangements. Made from light plywood panels for the bottom (in place of canvas) it would only be a bit heavier: https://www.offcenterharbor.com/flot...kwoods-school/
    If I had a dollar for every girl who found me unattractive, eventually they would find me attractive.

  16. #16
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    Default Re: Construction method costs

    Someone is definitely making money out of this, perhaps it is being used by the building trade, supply and demand. We have some social housing here that has all been beautifully clad, looks so out of place in post industrial North England town - should be on some beech somewhere io California.

    Plywood requires all of the above plus all the machinery to cut the veneers and manufacture but still a lot cheaper .

    All a bit academic now based on the cost, more research and the modelling I have be doing I have discounted strip plank for this design. I have my basic DelftShip model made and feel that the beauty of the peapods curves are lost aesthetically in a smooth hull. Now have 3 directions:
    > stitch and glue - quick
    > lapstrake - aesthetically nice
    > SOF - thinking composite with ply bottom like Chamberlain, just realised Dave Gentry does a version of this. As this would be lighter could increase the length a bit (I ideally want 13 foot but never designed anything with 13 in it, when I was an engineer my drafts man worried about me as along side draft angle and material thickness etc was the instruction on 13mm dimensions)

  17. #17
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    Default Re: Construction method costs

    I never thought about "unlucky" 13, but the "13" i built ended up being better than expected.....maybe not being superstitious helps.

    It may well be that the framework you need for a 13ft SOF, could be heavier than a few ply bulkheads needed to wrap ply around......if the matter of a few pounds is really an issue? S+G needs lots of finishing that lapped does not, and uses more resin than a glue joint on a small batten or lap, if your counting cost....certainly less abrasive paper used.

  18. #18
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    Default Re: Construction method costs

    Somewhere in an interview Iain Oughtred is dismissive of S&G saying something along the lines the time difference S&G is minimal and if you’re investing all that time and money do it right.

    Dave Gentry’s Chamberlain comes it at 7lb per foot
    Arch Davies 12 foot Peapod is also 7lb per foot
    Selway Fisher Kingfisher Peapod 10lb per foot
    Joel White must be a heavier build at 15lb per foot

    The Arch Davies construction is interesting, stringers and put onto the mold frames and then used as part of the final build to join the planks. The must add a good amount of stiffness as it is built with 4mm ply. I am sure that works ok on the sides but a bit light for the bottom IMHO. The web site says it uses 3 sheets, so one sheet could be 6mm for the bottom.

    http://www.archdavisdesigns.com/davis_peapod.html

    Trying to figure out a way of joining the planks and stringer to look more traditional lapstrake than a 4mm plank

  19. #19
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    A nights sleep and a fresh look at things, a look at weights
    Dave Gentry Light Melonseed 5.9 lbs/ft

    Dave Gentry Annabelle 6.3 lbs/ft

    Dave Gentry Shenandoah Whitehall (not sailing) 4.4 lbs/ft

    Michael Storer Goat Island Skiff 8.2 lbs/ft

    RS Aero (lightest production dinghy probably) 5.0 lbs/ft

    Aerolite classic 12 2.5 lbs/ft



    So this mornings direction, SOF Dave Gentry style but internals like bottom boards and seats as light as possible and or removable target 5 lbs/foot = 16lbs (27kg)



    https://tinkboats.wordpress.com
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    https://youtu.be/X9NZEyvpb_Y Streaker dinghy
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  20. #20
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    Default Re: Construction method costs

    27lb (16kg)?
    Don't underestimate the power of stupid people in large numbers!

  21. #21
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    Default Re: Construction method costs

    Hum, don’t think foamed graphene sheet is yet building material in your world yet, pity
    not sure where that came from 60lb (27kg) as target weight for the bare hull, 35 up a max of 40kg would be an absolute max as a frequently put 35kg on the car roof.

  22. #22
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    More calculations and a ply frame, cedar stringers and nylon skin looked a good route. As I costed it up the costs increased due to supply and demand of good wood here in the UK.

    I also started thinking about what is wanted from the wood especially the frames and from a strength the weight consideration ply frames can’t be very efficient as the grain is not working for you. Please don’t see this as a criticism of the Dave Gentry method of SOF, I think for a time effective method for the average builder it is very hard to beat.

    Didn’t like the idea of multiple steam bent frames as traditional SOF, good wood required again.

    So then came the thought of laminated beams, and this led to glulam roof trusses, popular in big public buildings. The massive advantage is by laminating any defects are spread throughout the beam and a much stronger beam is produced vs solid wood. With this method I could produce the beams from construction grade timber from a timber merchant and material cost would plummet. Just rip the timber to 3/16”; (5mm) and sort for defects. Sounds like a lot of work but my 12 ft peapod I figure on 4 frames, the hull is symmetrical so just make two twice. Rough picture of a frame and stringer joint



    Started looking at http://www.yostwerks.org and like the idea of a PVC skin, no coating required and easily available in the UK. It comes in 2m wide so apart from bow and stern not much gluing. The skin would then be lashed down a bit like a Umiak



    But with the subtle difference in that a sleeve would be glued in the edge of the skin, a pole inserted in this and the pole pulled down equalising the tension and reducing the lashing. It would be possible to remove the skin for transport and so reduce lifting weight and windage on the roof rack.

    Anyway still thinking, DelftShip model coming on nicely. From my rough costings I think excluding rig I can build a boat for about £200 (US$265). The hard part will be keeping check on the consumables, glues etc.

    The idea is not a million miles away from ‘two day boat’ by Ian Nicholson described in Iain Oughtred’s designs for boatbuilding. A design how ever doesn’t come up on an internet search.


    https://tinkboats.wordpress.com
    http://proasail.blogspot.co.uk
    What I get up to
    https://youtu.be/X9NZEyvpb_Y Streaker dinghy
    https://youtu.be/oni-3rJzxqQ Sail Canoe
    https://youtu.be/eW078PPgJak Proa
    Last edited by tink; 06-19-2018 at 03:14 AM.

  23. #23
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    Default Re: Construction method costs

    The Gentry Chautaqua i built came in at 4.4lb ft, that is with screwed in floorboards, but with the rig,rudder and leeboard removed. I think a shorter but slightly beamier "pod" could be done around the same weight. Wider the frames, the stiffer they need to be, or more stringers. Laminated frames would certainly work.

  24. #24
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    Default Re: Construction method costs

    My advice? Build the way you want to build. Sounds like that is strip planked. By the time you take into account other costs and make any accounting for your time, a couple of hundred pounds difference in the basic timber cost is neither here nor there.

  25. #25
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    Default Re: Construction method costs

    i would consider the durability of quick growth, low ring count lumber.
    it would have to be extremely well sealed.
    which ( looking at your attention to detail thus far) is something i am sure you have taken into consideration

  26. #26
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    Default Re: Construction method costs

    Quote Originally Posted by skaraborgcraft View Post
    The Gentry Chautaqua i built came in at 4.4lb ft, that is with screwed in floorboards, but with the rig,rudder and leeboard removed. I think a shorter but slightly beamier "pod" could be done around the same weight. Wider the frames, the stiffer they need to be, or more stringers. Laminated frames would certainly work.
    Encouraging thanks

    The thing I love about design is that you can spend a lot of time going down the road to find it is a dead end but can be seen as a positive as it validates where you where.

    Frames
    I separately asked about cascamite as a glue
    http://forum.woodenboat.com/showthre...29#post5596829
    Essentially it is not good for flexible applications and more suitable glues add a lot of cost which feel a poor investment on lumber yard timber. I also looked at the Section Modulus of the laminated frame vs ply and laminated frames looks like a lot of work for small rewards.
    Decision - plywood frames as per Dave Gentry

    Stringers
    Previous costs based on 3/4” x 1” WRC
    Looking a the costs here in the UK Ash is a cheaper alternative, for the same size as the WRC Ash would be 3.4 times stiffer (flexual rigidity EI) but 50% heavier and nearly half the price
    Reducing the Ash to 5/8” x 3/4” reduces the stiffness to 130% of the WRC a slight weight saving and a little cheaper than the bigger size of Ash - though the stiffness is the about the same as the WRC 5/8’” feels thin.
    I also looked at Alloy tube, GF tube and GF rod and though the tubes are stiffer and lighter they where expensive or not stiff enough for similar cost. Aesthetics, feel and practicality not appealing.
    Decision go for Ash, size depends on how weight turns out in during the detail design

    Skin
    Still like the idea of a removable PVC skin as it offers weight saving (when removed), low windage and easy frame maintenance.

    Feel happy with this direction, low risk and still a very economical way to produce a boat

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