Guide to Strip planking construction?

Discussion in 'Wooden Boat Building and Restoration' started by Dhutch, Dec 29, 2012.

  1. michael pierzga
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    michael pierzga Senior Member

    Strips are easy to cut...the profiles are tedious to machine.

    I like bead and cove. Square strips are slippery when coated with epoxy and wander out of line. Extra time fairing , filling and possible more stations and structure in the mold.

    I would think a small electric boat would be 12 or 15mm core ?

    150 dollars per square meter bead and cove .... not cheap.



    How much does that Electra launch weigh ?

    And why the fancy carbon hull on the patterson boat ? Marketing ?

    [​IMG]
    photo sharing
     
  2. Dhutch
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    Dhutch Junior Member

    I currently only have a portable circular mitre saw, however I have space and budget for small bandsaw or tablesaw, as well as a hobbie-spec planner thicknesser, and for that mater a table router or table attachment for my current one. I also have a friend with a large woodshop, with two bandsaws, and if you really wanted, a 3ft diesel log saw.

    I had always thought, assuming the cost of the epoxy didnt make it a silly cost cutting there wasnt much point, however the point about strips being slippery and misalignment are noted, and im not at all against paying for work that I would find far more difficult and tedious than the cost difference of having someone else do it!
     
  3. Dhutch
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    Dhutch Junior Member

    A ton, and yes, I presume so... maybe stiffness? to carry off the highgloss finish?

    The specs on Irens website are as below:
    LOA/LWL 7.3m (24ft)
    Beam 2m (6ft7)
    Displacement 1 ton (2200LB)
    Power 22kw (30bhp)
    MaxSpeed 15knots (17mph/28kph)
    SLmax 3.1 DL 81

    No, I would be planning a small IC engine for the power, probably petrol, with a conventional transmission. While the electric only version quotes 15knots there is a hybrid which claims the ability to product 90kw giving 'up to 30knots' for short bursts.
     
  4. michael pierzga
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    michael pierzga Senior Member

    Displacement one ton...what about hull weight ? That carbon foam hull shell pictured is ultra light.

    Perhaps find out the weight of its power plant and systems then work backwards to see what kind of wiggle room you have for simplifying the hull construction
     
  5. Dhutch
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    Dhutch Junior Member

    Valid point, although I assumed the displacement was the same as the dry weight, which may or may not be the case, and didnt see that you where asking about the hull wieght, which Im not sure it will be easy to find out.

    I have the broker advertising the boat what the dry weight is (which is a start, to confirm the 1ton) as well as if there is any diffrence in weight between the all Electric and the Hybrid. Then as you say, if I can get some infomation on the weight of the batteries/motor/controller, you can work from there.

    What do you have in mind in terms of simplification? The converting from foam core carbon to softwood glass? Would you suspect the original hull to be all carbon, or a carbon/glass mixture? Kevlar?


    Daniel
     
  6. ancient kayaker
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    ancient kayaker aka Terry Haines

    Displacement refers to the amount of water the boat displaces when floating freely in water, which eqauls the total weight of boat plus fuel and water plus crew and anything else placed in it. To illustrate, the dry weight of my canoe is 10 kg, the displacement is closer to 100 kg until I get those Christmas and New Year dinners worked off . . .
     
  7. PAR
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    PAR Yacht Designer/Builder

    Again, with very little block plane experience, you can make perfectly fitted bevels, on strips in literally a few minutes. This is less time then it is, to push the darn things through a router to profile them (twice). On small strips, a swipe or two is all it takes, in most cases. At the turn of the bilge, you'll need to focus a bit, ditto any reverse curves, like a built down hull might have, but and again, unless the hull is to be finished bright, these are just aesthetic considerations, as all can be cured with wood butcher's friend, sheathings and paint. A slippery strip is what happens until you get some experience. After a few strips into the project, you'll learn to have a finish nail already in the end of the strip, so it can be located next to it's neighbor and tacked down, thus no slipping as you walk it in, the rest of the way.
     
  8. ancient kayaker
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    ancient kayaker aka Terry Haines

    The el-cheapo table router in my previous post was not for beveling, it was used for adjusting strip thickness after ripping slightly oversize. I only routed one side and put that on the inside of the hull - it's easier to sand the outside.

    Some other pointers:

    I routed a groove in the edge of a plank to fit a strip; with the plank held in a vise the groove held the strip for beveling. A tack at one end of the groove stops the strip from sliding.

    If you rip your own strips a thin-kerf blade saves a lot of wood from being wasted.

    Applying glue is easier with bead and cove since the cove holds the glue: when applying glue to square-edged strips a little guide on the tube helps to keep the glue bead centered: freehand can make a mess. If you have a big enough shop to risk horsing around with a glued strip you can also apply the glue to the strip while it is in the groove.

    You can strip-build without using staples but it is slower: add a narrow batten along the edge of each station form to gold the inner jaw of a spring clip: you'll need at least two clips per form. With this approach you have to wait for the glue to dry before adding the next layer of strips.

    Since a stripper has to be glassed both sides thre's no need to use epoxy to glue the strips - carpenter's glue is fine and faster and cleans up with water.

    Some good information here http://www.laughingloon.com/shoptips3.html
     
  9. michael pierzga
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    michael pierzga Senior Member


    Well, in the perfect world...design is beautiful...and exotic materials are wasteful. It would be perfect if that design could be built from normal cedar core, Eglass skins, with lightweight plywood structure and fit out.

    These material are cheap and easy to use.

    If you must use carbon, foam and exotics to achieve the one ton displacement , then its a bad design.

    You should guesstimate the surface area of the boat so that you can guesstimate the weight of a typical cedar core, eglass hull.
     
  10. Dhutch
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    Dhutch Junior Member

    Yes, I suppose the smaller the boat the greater the room for discrepancy.

    I'm not afraid of planing a bit of a bevel on and I suppose a meter or so of strips is only 40 off 25mm strips per side(guessing dimensions based on what I've seen, to get a feel of the job) and as you say, somewhat glue dependant, it doesn't matter too much if there is some gap.

    Fair enough, and presumably if the strips are a little over length you can always put the nail on the part to be trimmed, not that it does any real harm if its included. And you could if needed add odd nails elsewhere if some sections where being troublesome.


    There appears to be some discrepancy as to what 'carpenters glue' is but most point to it being ' aliphatic resin' (a slightly improved PVA) which requires a good clamping force and is not typically waterproof. I suppose to a point it will be encapsulated in the sheath and ultimate strength may not be required but I have to admit my gut feeling rightly or wrongly is I would prefer to use epoxy, or perhaps PU.

    Im slightly lost by your later comments. I have seen staples used in cold moulded construction, but surely with a 15mm or so core they cannot be used to secure strips in the same way they are used to secure veneer? Where am I putting the clips? I have seen clamps used to hold strips against the former, is there what you are describing? As said, your then limiting yourself to a strip (per side) at a time which fi you where trying to make progress over a weekend would be an issue, although it might work if doing a strip or two a night after work during the week (one when you get in at 6, one when you go to bed 4-5hours later?).

    Daniel
     
  11. Dhutch
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    Dhutch Junior Member

    Posts crossed, at which point, I must thank everyone who has replied so far for their thoughts, comments, suggestions, advice and the rate at which they have been coming, its great.

    As you say, a rough calculation of area, based on the overall dimensions as known, and the various images we have available would be another good pointer.
    I somewhat agree with you about exotic materials being a excuse for poor design, athough given its a lithium power electric boat, you could argue carbon fibre is infact relatively estabilished!


    Daniel
     
  12. michael pierzga
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    michael pierzga Senior Member

    Concerning what methods to use, there are many ways to build a hull. I would choose the method that produces a fast hull build , then concentrate on fit out. Fit out and attention to detail is what makes a good boat and its the most labour intensive, expensive phase.

    and For power , why not poke a 4 stroke outboard thru the hull, fix the outboard permanently , faired in like a sail drive unit , then use a rudder to steer the boat.
     
  13. TeddyDiver
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    TeddyDiver Gollywobbler

  14. michael pierzga
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    michael pierzga Senior Member

    Sure...looks logical. Ive seen several ways to keep the strips in line.

    When costing a job its best to choose the expensive materials...speed strip or pre milled bead and cove strips.

    Once you get the cost of the "good stuff " then you can look for ways such as shop milled strips to make savings.

    For a homebulder, without decent shop machines or helpers , it is cheaper to purchase pre milled
     

  15. PAR
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    PAR Yacht Designer/Builder

    It's important to understand that some strip methods rely on the sheathing, while others don't. Also, some strip methods use fasteners in every strip, while others don't. If using a PVA or similar, fasteners are a good idea and the sheathing must be load bearing. There are (again) lots of little tricks and techniques for strip planking. I use a "U" shaped wedge, cut from plywood to help keep the strips aligned.

    As far as speed, strip planking isn't one of the best. If I wanted a round bilge hull, I'd consider Ashcroft or glued lap, long before strip for speed. Then again, the hull shell is just 20% or less of the total effort to build a boat, of course depending on size and utility.
     
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