Anyone used pine for strip planking?

Discussion in 'Multihulls' started by Saylaman, Feb 18, 2008.

  1. TeddyDiver
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    TeddyDiver Gollywobbler

    I wouldn't worry so much about the potentiality of rotting. Encapsulating the strips properly, and Biax/epoxy on both surfaces is quite enough to protect any wood. How well epoxy bonds to wood is much greater concern along with the other fysical properties such as workability and strength. In a case of a hole in the coating most of the wood species will eventually rot (with the exceptions like Teak and Sibirian Larch and they aren't never used in cored hulls). It's just a matter of time, but with barrier coating it won't spread.
     
  2. Saylaman
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    Saylaman Junior Member

    catsketcher
    Thanks very much for all the info on foam. The info is very helpful. Pine is looking less and less attractive. At the moment it is looking more likely to be foam for the hulls and kiri for the deck. As soon as I make the decision I can move forward with the design, finalising sizes etc.
    Thanks
     
  3. Saylaman
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    Saylaman Junior Member

    Teddy Diver
    Thanks for your input. I've used pine for a lot of other applications and there is usually some resin seeping out somewhere. I expect that bond will be a problem. There must be some very good reason it is not used for boat building otherwise I guess lots of people would use it. I suppose when the boat is done if it turns out well, I'll be sorry I used pine. It will be impossible to sell if I ever tried.
    Thanks
     
  4. rwatson
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    rwatson Senior Member

    Saylaman - yes the pine isnt a good choice. You may get a few years out of it, but its not a good bet, especially since the seasoning can be very mixed quality.
    To get good results from encapsulation, you have to have quite low moisture content, and radiata pine isnt that well seasoned in many cases.
    The other big reason it is rubbish for boat building, is that fairing it is a real problem. The oils and wax muck up power tools and sanding papers of all sorts. A high speed drill will almost burn its way through on average grade Radiata pine timber. Also, the grain is very cranky, and trying to get it fair would drive you mad.
    I would be very interested in comparative prices on Kiri V Foam, as I have a small project that I have on the drawing boards. Airex keeps getting a good rap, but where to source it here in Oz for a decent price is the question.
    Anyway, the cost of the hull material is going to be a very small part of the overall cost.
    Using western red cedar, the final two part sealer and 4 top coats cost more than all the timber on my last project.
    Bye the bye, one reason I am favouring foam myself is the fact that you can use VynelEster (as opposed to Polyester) rather than Epoxy, which could be a big cost saving.
     
  5. Saylaman
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    Saylaman Junior Member

    rwatson
    Thanks, your input is very helpful. I've experienced the way pine gums up sand paper etc, but never having faired didn't realize what a problem it would be. Thanks for saving me the catastrophe! I also like the fact that foam doesn't need the epoxy. Foam would require a much thicker laminate than kiri, both in and out, I haven't worked out yet which would be cheaper. I tried to work it out the other day, but could not find someone with a price on the 200gsm uni that I'd used in the kiri design. I'd be interested to hear from anyone who's done the comparison.
    Thanks again!
    Saylaman
     
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  6. Raggi_Thor
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    Raggi_Thor Nav.arch/Designer/Builder

    You got a lot of good answer, but here's another one.
    Pine (Pinus Sylvestris) is used a lot in Norway (and Scandinavia) both in traditional building, lapstrake and carvel, and in stripl-planking. It's easy to work and takes glue and varnish well. I think it depends on availability and price. I would like to try Kiri because of tghe weight. Norwegian pine is approx 400kg/m3. Spruce is a little less but harder to get.
     
  7. PAR
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    PAR Yacht Designer/Builder

    Saylaman, be careful. Switching core products from a self supporting material like wood to a non-self-supporting material like foam, requires a completely different tack from a engineering point of view. The two are not interchangeable.

    There are several approaches to strip planking and to sandwich construction and these generally aren't interchangeable either.

    Basically it boils down to two different concepts, one has a self supporting internal structure that typically carries a large percentage of the yacht's longitudinal stiffness, while the other doesn't, instead relying on sandwich dimensions and separate reinforcement, plus the laminate itself.

    Consider your options wisely, as I can think of at least a dozen different variations to these methods, all having good and bad points to them, not only from an engineering aspect, but from a builder's view as well. If you enjoy fairing 'glass structures and playing with goo and fabrics, then a sandwich method could be for you. But, if you'd rather just use some inexpensive strips, which don't need to be perfect, then one of the more traditional strip methods might be the ticket.

    I'd also strongly recommend you have your design (if self designed) looked over by a qualified designer, particularly if you'll be going the sandwich route. These types of structures need to be highly engineered to work successfully and remain cost effective.
     
  8. rwatson
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    rwatson Senior Member

    Raggi - the pine in australia from tree farms is Radiata Pine - and as I have said, is rubbish for any type of marine work (although copper treated logs are ok for jetties etc.
    Par, your comments on the foam technique are very useful. The BIG factor in my mind that steers me towards foam is the price of the resin used. Epoxy (over timber) is quite a bit more expensive than polyester or vinylester .
    I will be doing the sums soon on my project
     
  9. TeddyDiver
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    TeddyDiver Gollywobbler

    I'm not aware of the poly/vinylester prices, but epoxy for my 33' project made about 3000e (300kg purchased last year). In the total budget of 30k (just hoping and telling lady) to 60k (closer the truth) it's irrelevant even if the resin were free. There's also to consider the price of the core. Foam is generally more pricy than timber and with foam core you need more resin/glass.
     
  10. PAR
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    PAR Yacht Designer/Builder

    Teddy's comments reinforce my contention you should weigh things carefully. Foam cored structures are GRP construction, which require considerably more laminate, hence resin, while some of the strip methods gain a substantial amount of the hull stiffness derived from the core material, with a thin sheathing, which requires considerably less resin, even after encapsulation of the core. Price out a square foot of sandwich construction compared to a few of the strip methods and you'll quickly see the difference, especially if using one of the honeycombs or fancy foams.
     
  11. rwatson
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    rwatson Senior Member

    I did some quick research tonight, and some figures I have come up with need verifying.

    For a start, I have priced Epoxy as low as $au15 per kilo when bought in bulk. Teddy Divers 300kg of epoxy, around $au20 per kilo sounds like it would have been a quality system like West Systems. The amount sounds very realistic.

    Theoretical amounts for a 28ft trailer sailer would have been around $2000 to wet out the cloth. But after doing a smaller strip plank WRC, I would double that. The sealing coats on the timber prior to the cloth (inside and out), the endless sanding leaving a good third as white powder in the rubbish, has to be allowed for.

    The price of foam core is about 1.5 times that of plywood, but it doesnt absorb very much due to its closed cell nature. Timber stripping can be allowed up to $50 per square metre, and I will need around 40 square metres, or $au2000
    Foam core is about $au50 to 60 per square metre, and doesnt need gluing in 45mm strips

    A good quality polyester resin is about 2/3 the price of epoxy, so with a slightly more expensive core (with less work) that uses quite a bit less 'goo' that costs a fair bit less, the core sounds a good candidate.

    I know designers hardly allow any structural strength for wood strips when they calculate scantlings, due to the fact that the glued edges of the strips are less than 50% of the shear strength of the timber. Yes, I know good glue will break the wood before the glue, but the fact that the wood has been sawn means there is no lignin fibre between the planks, and the edges will just be torn away from the glue on impact. It is just a 'filler', and the amount of fibreglass is not a lot less than foam core.

    The other big candidate for the project is aluminium. The costs for materials is actually less than all the other methods, not allowing for the skilled welding labour and the foam in the interior, and the obligatory timber liner. and the big kicker is - no special coating on the outside!

    Gets complicated - doesnt it!!!! More ideas welcome,
     
  12. TeddyDiver
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    TeddyDiver Gollywobbler

    Endless sanding. No not for me. If I were sanding that much the sanding paper would be the highest cost of the boat. Better do the sanding before epoxywork and drylaminate the cloths.

    I don't know timber prices in Oz but wouldn't never pay that much (of course I'm in Finland so..). Just some good quality contruction timber like 2''x5'' and a good table saw..

    A good NA would calculate the strenth of timber. You know boats used be build of that "filler" :p Read Dave Gerr's The Elements of Boat Strength theres scantlings for various building methods so it makes the comparison of different materials and building methods easier.

    Chears Teddy
     
  13. rwatson
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    rwatson Senior Member

    Its true, they used to build boats out of timber - I come from an island that *used* to have the best boat building timber in the world till it was all used up.

    However, the boats they built back then had more than 7mm planks for canoes like my last project, and any timber 25mm thick for my 28footer that I can source these days, would not last long without a lot of re-inforcing.

    Western red cedar is way too soft to use by itself, and at 25mm thick its around $60 per square metre (sawn). The other alternative, Kirri (Pawlonia) is also way too soft for 'raw' boat building.

    In my grandfathers day we would have used 'Swamp Gum' for the keel and main structural members, 'Celery Top Pine' for the hull and that could have been 25-30 mm thick without any trouble, and "Huon Pine" for the interior. The cost of the traditional method *if* you could source that kind of timber is around $3000 per cubic metre, so it is not in contention even though fibreglass prices are increasing with the cost of oil.

    So, with the lack of available 'good' boat timbers in my world, you cant rely on uniform structural strength - even by *good* NA's. Just check out the grades of WRC that get delivered - they range from dry, very clear hard to soft, grainy grades - its just luck. Kirri's main virtue is its flexibilty, lightness, ease of working and longevity (excellent rot and borer resistance) - but its shear strength is less than WRC, and its quality is variable like all modern timber.

    The only people relying on timber strength alone will pay very high prices, unless they are close to the last remaining sources on the planet.

    The exception of course, is plywood - but that is re-inforced soft timber that can be made up from the smaller trunk sizes that are available these days.

    And as for sanding epoxy - you lay the first layer on the faired timber, then you have to sand off the runs. If you, dont, then subsquent layers will enlarge the run area. It takes a minimum of three coats on WRC to get a non porous base before the cloth is laid for the softer wood, especially if you need a clear finish.
    Then you can "dry" lay the cloth with minimum wetout, wait till its tacky, and then do another coat. But unless you are doing a flat surface, you get runs that have to be sanded out. Then another two coats is recommended, and then that has to be faired back also. Dont forget, unless you can be with your boat 24 hours a day for a week, you have to sand prior to applying further coats to get a good contact. If the finish is clear, then the demands are even higher. The layers of cloth often create areas that need to be faired back after filling (near overlaps for example) so a lot of epoxy gets sanded back off, that you have to pay for.

    Aluminium is looking better all the time.
     
  14. TeddyDiver
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    TeddyDiver Gollywobbler

    :D Just hard to remember you got much warmer climate. I got to warmup my tent in summer time just to get adequate temperature to get the stuff throw the pump.. no problemo with runs...
    However, think 5-10% for spils, leftovers and sanding should be enough..

    70' I was (helping) building wooden aeroplane, and the wingspar material was sended to be tested. 5x10mm pine strip broke (draw) once at 740 kg twice around 900kg and one specimen holded 1000kg without breaking (it was the maximum force they could do):cool:
     

  15. Saylaman
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    Saylaman Junior Member

    Hi All
    Thanks so much for your replies. Sorry for the delay, I've been moving from Perth to Sydney over the last two weeks and have only just been 'connected' again. Before I left Perth I visited Highpoint timber for some Kiri samples to experiment with. I will take some time to look through your replies. Thanks again.

    Saylaman
     
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