Anyone used pine for strip planking?

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

  1. Saylaman
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    Saylaman Junior Member

    If anyone has experience with pine for strip planking I'd appreciate some feedback. I know there are lots of varieties of pine. I have weighed some local samples and get a density of 370 kg per cube. Kiri is around 260 kg per cube. When I compare the stiffness of similar sizes of pine and kiri, the pine is much stiffer. I intend to cover both outside and inside with epoxy/glass. I have considered using 12 mm pine strips rather than 14 mm kiri strips. This will add about 50 kg to my 8.5 m cat. Pine is easily available, very cheap, not excessively heavy. Apart from the extra weight, what other disadvantages will I have? Does epoxy bond well to pine? Thanks.
     
  2. PAR
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    PAR Yacht Designer/Builder

    As you eluded to, there are several dozen sub species of "pines", each with different physical properties. To make matters more confusing, there are also several different ways to do strip planking. Each strip planking method utilizes the strips differently, with everything from traditional strip, which has no sheathing and the longitudinal stiffness is totally born by the strips, to the Lord method, which is really a sandwich construction build, that uses strips as the core, with many variations in between.

    So, it depends on what you want and the method you're going to use, which determines the scantlings of the strips, laminate schedule and material properties necessary. An example would be the Lord method requires high modulus, continuous biax sheathing and a light weight core. This means you could use very light, less then ideal strips, but the inner and outer skins have to be well engineered and applied. The other end of the scale is a basic strip build, with a light weight sheath. It uses a denser core, of reasonable quality and an abrasion resistant sheathing to protect it.
     
  3. Saylaman
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    Saylaman Junior Member

    Thanks PAR
    The method is not traditional or Lord, but somewhere in between. Lord uses flexible sheething, I want to use glass in epoxy. The laminate is 400/14/400. The 400 sheathing on each face is two layers of 200 gsm uni in epoxy. The 14 'core' is kiri, very similar to the red cedar.
    I know that if I substitute pine for the kiri it will be as stiff, probably stiffer and it will be heavier. What I don't know is whether it will bond as well as cedar. Have you had experience with epoxy and pine? I also need to decide whether I will waste too much pine rejecting strips with knots or poor grain.
    Thanks
     
  4. BWD
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    BWD Senior Member

    Being "1/2 way" done building a strip planked boat (hull done) I have some ideas. I used Western red cedar, also thought about pine. Beyond wood species, I thought about:

    1)Selecting whole logs + having them milled to get the grain alignment and clear runs etc. that you want.
    -too much of a pain.

    2)Buying from a source that specializes in boat wood.
    $$ ouch.
    3) Buying from a "normal" lumber yard that allows you to pick boards from stock, rather than just throwing whatever is atop the pile into your truck (some let you do this, some don't where I live).

    I found a yard that let me pick boards from stock, and had them milled to the strip size I needed. This gave me good wood cheaper than from a boat specialist yard, and control over grain, knots, etc. The milling quality though was not as good as what you would get from a specialist.

    To do it over again, I would have spent the extra money to have wood shipped from a specialist, because it would have saved me at many hours of fairing. I also might mill the strips myself.

    Best bet for deciding on species I think is to make test panels. In a few hours you could make small panels with cedar, kiri, and a couple of other woods, and glass them up. After a few days cure, destructively test them, paying attention to impact, peel strength, bending.....
    Also this way you might find out which wood you and your tools like working best, saving more aggravation later...
     
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  5. Saylaman
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    Saylaman Junior Member

    BWD
    Thanks very much for the response. Since you're in the middle of the job your feedback is very valuable. I've had the same questions, thoughts and ideas going through my mind. Your advice to make up some samples is good. I'll get going with some sample panels. I'd be interested to know what boat size and type you're building what the strip thickness and laminate is. Thanks again.
     
  6. PAR
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    PAR Yacht Designer/Builder

    If the pine is very "resin" filled, then you can have bond issues. Again it depends on the pine. Do you know what it is?
     
  7. Saylaman
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    Saylaman Junior Member

    I don't unfortunately know the pine species. I have some from the local hardware. I'll have to find a timber supplier who has more comprehensive information about the types available and their properties. I suppose the only way to find out would be to do proper samples and testing.
    Thanks
     
  8. PAR
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    PAR Yacht Designer/Builder

    You can cut off a small section and ask the agricultural department of the local collage to determine the species for you. If you dropped by with donuts and coffee, first thing in the morning, I'll bet you'd have a reasonable guess pretty quickly.

    You can also remove the surface contaminates with acetone or denatured alcohol. This would have to be done, just prior to epoxy wet out (let the solvent flash off first).
     
  9. BWD
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    BWD Senior Member

    Nothing big. It's to be a sailing outrigger canoe, 18 feet long. Strips are 1/4 by 3/4 inch (~6mm x 18mm). Typical laminate for canoes with small sails is 6oz Eglass in and out plus local reinforcements. I may use a bigger sail and do not anticipate a pampered life for the boat so I went with 9oz S glass in and out, with a healthy 3-5 inch overlap at the keel outside. Bulkheads are 1/4 fir ply in 9oz S glass, taped in with 2 x 6oz biaxial eglass.

    I did find the S glass a bit of a pain in wet hand layup, by the way, but it got easier going along....

    I did not do hull test panels, just went with the western red cedar as it's a standard and very easy to shape, although it makes me sneeze (use a mask).

    I did decide to do cedar inner gunwales though, reinforced with unidirectional carbon, instead of hardwood gunwales. I made a gunwale test sample and was reassured by being able to park my truck on top of a 1 foot section of 1.5x3/4 inch thick cedar supported only at the ends, with <2% deflection!
    Here's a picture of the vaka serving as a tool bin a while back, with a rub rail going on....
    Best luck with your project.
     

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  10. catsketcher
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    catsketcher Senior Member

    consider foam

    Hello all

    I have constructed four boats - 3 cats and one tri. One cedar strip, one Kiri strip. one strip foam with bean and cove and one strip foam.

    I would suggest going vertical strip foam for easiest, fairest and cheapest method. When I built my little 6m trailer sailer cat Kiri was cheaper but it has increased in price whereas the foam hadn't.

    Kiri was very hard to get straight - maybe I got a tricky lot. Cedar was lovely to work with and produced a great boat but is pricey and slower than foam. Vertical foam is quicker and really easy to plod along on your own.

    If the boat is small and inexpensive make it out of whatever you want. As soon as it gets to be a significant investement make the hulls out of good materials. I once had a friend who saved $2000 by making his 40ft cat out of construction grade ply. He had to reduce his selling price over $50 000 after he had spent many thousands trying to cover the ply up.

    cheers

    Phil Thompson
     
  11. Saylaman
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    Saylaman Junior Member

    PAR
    Thanks for the tips, both the donut tip and the acetone tip are good ones. I didn't realize that the 'bond problem' could be solved with cleaning, thanks very much. I was doing some calculations after getting prices yesterday. By using pine the cost of timber would be 35% of the cost of Kiri.
    Thanks
     
  12. Saylaman
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    Saylaman Junior Member

    BWD
    Thanks very much for your input, the pic and all the info. Sure looks great. It would be nice to have some pics when you finish. I like your test. Parking a truck on a sample and measuring deflection. That auta be strong enough.
    All the best with the boat.

    Catsketcher
    Thanks very much for your feedback. I have been considering all these options back and forth in my mind. Your feedback is very valuable. I was (and am still) very tempted to go with the vertical strip foam. Being my first build and design I'm not confident of the final position of deck hardware. I'd like to be able to finalize the positions after some sailing. Foam core will be more difficult to modify later. I suppose I could go with a foam hull and Kiri (or pine) deck.
    Thanks
     
  13. rwatson
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    rwatson Senior Member

    You dont need too much testing - just drop by the local timber yard with a sample and they will tell you in a couple of seconds.
    If you got your pine from a local hardware shop, its probably Radiata if its a pale almost white colour with thick growth rings. This can be a bit too oily for epoxy, and it certainly has not got the longevity of Kiri. Even little bits of moisture will rot it out.
    Western red cedar is pink to brown, with close growth rings.

    On the subject of foam strips - what type of foam are we talking about here?
    Theres must be a lot of different types.
     
  14. Saylaman
    Joined: Dec 2007
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    Saylaman Junior Member

    rwatson
    Thanks for the input. I know that pine will be very likely to rot with moisture ingress. Having had no experience with maintenance I have no idea of how 'watertight' the strip planking and epoxy sheathing is. Does some water still get into the wood? Is it very difficult to ensure that the wood core is watertight?
    I haven't looked into foam all that much except download some specs for a few types off the internet. I was interested in the way the Corsair tri's are constructed, but still need to do a lot of work getting information on which foam to use. If anyone has recommendations they would be valuable and appreciated.

    I have been studying yacht design for years, but I feel it is useless unless I've built one of my designs and sailed it. I don't want to even consider selling plans until I've done this. Being my first design and build I don't expect to recover any money on it. I'm sure I won't get everything right on the first try. I don't want to pour huge amounts of money into something that is more part of my education than anything else. At the same time, I would like to be able to sail the boat for a good number of years. I don't want to take years to build something, just for it to rot two years later. The design is an 8.5 m trailerable camping-style cat. The expected use is probably only a few weekends a year and an annual coastal 'camping trip' of up to two weeks duration.

    Pine is cheap, but obviously has a potential bond problem, a rot problem, a weight disadvantage and is very variable. Information on how watertight the epoxy laminate really is would be valuable so that I can decide whether the pine will have enough life in it to make the cost saving worth it.

    Thanks
     

  15. catsketcher
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    catsketcher Senior Member

    Foam types

    There are a few foams around - Airex and its sister foam - Herex. Airex is very flexible - less cross linking - good for hulls that get slammed - not so good for decks.

    Divinycell is a cross linked PVC foam which can be used in hulls and decks. It will not bend as well as Airex but in thin sizes will bend fine. 10mm does an 800mm radius easily - tighter with a heat gun.

    Core cell is a SAN foam - it supposedly has properties between Airex and Klegecell. I built a 38 foot tri out of it and found it very similar to Divinycell.

    As to density - just use 80kg per metre cubed - everyone else does. For a small boat you can go down to 8mm. It will bend like crazy when molding and stiffen right up with a laminate on it.

    Don't use pine. You must value your time and all the other bits of equipment - resin, glass and hardware you will be putting in the boat. The amount saved will be small especially if you factor all the glue in the strips.

    cheers

    Phil
     
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