Tree species for a big mast

Discussion in 'Sailboats' started by ShaneK, Mar 19, 2014.

  1. ShaneK
    Joined: Mar 2014
    Posts: 5
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: Ireland

    ShaneK Junior Member

    Hi all. Can you advise me of a tree species for a BIG mast, preferably something that is grown in Scotland or possibly Scandinavia. I KNOW that just about everything grown in Ireland is crap for this purpose !

    I want to construct a 25 - 30m cantilever mast with a hollow section and probably reinforced with inlaid glass or even Kevlar unidirectional roving.
    I am familiar with wooden aeroplane propellors being made in similar fashion.

    Thanks-in-advance.
    Shane
     
  2. jehardiman
    Joined: Aug 2004
    Posts: 2,264
    Likes: 160, Points: 63, Legacy Rep: 2040
    Location: Port Orchard, Washington, USA

    jehardiman Senior Member

    You may get more/better answers if you go ask this question on the Wooden Boat forum.

    http://forum.woodenboat.com/

    Tight straight grained spruce or fir is most likely what you need, but even in the early 19th century there weren't enough suitable tree left so masts began to be pieced. Even a hollow birdsmouth mast that big is going to be very heavy compared to an alloy or carbon fiber mast.

    http://duckworksmagazine.com/06/howto/birdsmouth/index.htm
     
    Last edited: Mar 19, 2014
  3. Petros
    Joined: Oct 2007
    Posts: 2,938
    Likes: 138, Points: 63, Legacy Rep: 1593
    Location: Arlington, WA-USA

    Petros Senior Member

    I have many years experience engineering wood structures, and a cantilever mast that size made out of wood is going to be very large, and there are not many species that would be suitable. I do not think there have ever been all wood cantilevered masts that large, almost all of them taller than about 10 meters would have been braced or use shroud lines.

    Unless you intend to use the wood as a hollow plug and the composite skin is going to provide all of the strength, it will be VERY heavy.

    You should also get some competent assistance on designing and detailing the design of such a large structure. Either a Navel Architect familiar with hand build cantilever masts or a structural engineer familiar with wood design.

    Good luck.
     
  4. gggGuest
    Joined: Feb 2005
    Posts: 770
    Likes: 9, Points: 18, Legacy Rep: 76
    Location: UK

    gggGuest ...

    Carbonus Fiberensis is surely the most suitable species... You could vac bag on some pine veneer if you are feeling picky...
     
  5. PAR
    Joined: Nov 2003
    Posts: 18,598
    Likes: 377, Points: 93, Legacy Rep: 3967
    Location: Eustis, FL

    PAR Yacht Designer/Builder

    Douglas fir is the logical choice, but why a solid mast? There's no reason to burden any boat with this type of arrangement. There's also no need or desirable trait for 'glass or other sheathings on a solid grown timber mast, so skip this step.
     
  6. Stumble
    Joined: Oct 2008
    Posts: 1,884
    Likes: 67, Points: 48, Legacy Rep: 739
    Location: New Orleans

    Stumble Senior Member

    Shane,

    I think you are barking upan incredibly difficult tree. A cantilever mast this size is not only going to be incredibly heavy, but also very expensive to build well. In fact I would posit that it would be the largest wooden mast of its type ever built, which leads me to think there may be a terminology issue here more than a technical one.

    Every mast I have seen in this size for the last decade have been carbon fiber, and there are a lot of good reasons for it. Could you provide more information on why a free standing mast of this size, made from wood is even desirable?
     
  7. Tad
    Joined: Mar 2002
    Posts: 2,275
    Likes: 161, Points: 73, Legacy Rep: 2281
    Location: Flattop Islands

    Tad Boat Designer

    The biggest unstayed masts I can think of are those in Norfolk Wherry's. Below is Albion, around 58' by 15'. Her mast is only 42' overall and around 14" in diameter. The sail is about 1200 sq ft.

    albionlk4.jpg
     
  8. bregalad
    Joined: Dec 2010
    Posts: 108
    Likes: 4, Points: 0, Legacy Rep: 36
    Location: Georgia

    bregalad Senior Member

    Bolger's 50 foot Tonweya (in 30-Odd Boats) has a 55' 6" unstayed hollow wood main. 10-1/2" diameter with some carbon fiber let into the rounded corners. I don't know if that was his largest though.
     
  9. rasorinc
    Joined: Nov 2007
    Posts: 1,850
    Likes: 69, Points: 48, Legacy Rep: 896
    Location: OREGON

    rasorinc Senior Member

  10. Eric Sponberg
    Joined: Dec 2001
    Posts: 1,987
    Likes: 190, Points: 73, Legacy Rep: 2917
    Location: St. Augustine, FL, USA

    Eric Sponberg Senior Member

    The best species are Sitka Spruce and Douglas Fir. You need to hand-select each piece to make sure there are no knots or imperfections in the wood. Cut and splice as necessary. Use epoxy resin.

    Reinforcement with fiberglass or Kevlar is folly. Glass has similar strength and stiffness to wood, but it is heavier than wood, so you would do better to simply increase the wood thickness than adding fiberglass. And Kevlar has very poor compression strength. Wood free-standing masts fail in compression, so Kevlar is not going to help. If you want to reinforce with anything at all, in my opinion, it should be carbon fiber.

    For guidance on size, you can use the book "Practical Junk Rig" by Hasler and MacLeod to get an idea of how big your mast will be. That book also gives guidance on making a hollow section mast with the appropriate wall thicknesses and section tapering. The authors admit to NOT being engineers, so take that seriously. The size of your mast is quite large, so you may want to consider hiring a professional to do the mast design for you.

    The largest wood mast that I ever designed was for a motorsailer called Nai'a, 120' long. The wood-epoxy wingmast was built on the beach in Fiji and was 99.2' long (30.2 meters). To my knowledge, it is still the largest wood-epoxy wingmast in the world. You can read about it on my website:

    http://www.sponbergyachtdesign.com/Nai'a.htm

    Eric
     
  11. SukiSolo
    Joined: Dec 2012
    Posts: 1,268
    Likes: 25, Points: 0, Legacy Rep: 271
    Location: Hampshire UK

    SukiSolo Senior Member

    I think Eric has summed this up nicely. Sitka is probably the best material. Collar in Oxford make masts out of it for quite a few boats and use Douglas Fir for spreaders.

    I can give you the name of a UK supplier of high quality Sitka but it is directly imported from mainly British Columbia by the supplier - who is not a large timber company. PM me if you need this information.

    If you use any fibre reinforcing it should be good in compression. Timber is stiff OK (for weight) but 4 to 5 times better in tension than compression. Also a lot of early carbon masts had fibres not as good in compression as current fabrics.
     
  12. Tad
    Joined: Mar 2002
    Posts: 2,275
    Likes: 161, Points: 73, Legacy Rep: 2281
    Location: Flattop Islands

    Tad Boat Designer

    Sometime in the night I remembered Phouma, a Phil Bolger design stretched to around 125' by 16'. Her foremast is huge and appears unstayed......I don't know if she ever sailed anywhere......

    Phouma1.jpg

    Phouma2.jpg

    Phouma3.jpg
     
  13. Eric Sponberg
    Joined: Dec 2001
    Posts: 1,987
    Likes: 190, Points: 73, Legacy Rep: 2917
    Location: St. Augustine, FL, USA

    Eric Sponberg Senior Member

    Phouma looks to have stayed masts--you can see the shrouds and stays in your photos. Looks to be either a gaff or junk rig by the boom on the mizzen mast. Can't tell on the main mast.

    Eric
     
  14. Tad
    Joined: Mar 2002
    Posts: 2,275
    Likes: 161, Points: 73, Legacy Rep: 2281
    Location: Flattop Islands

    Tad Boat Designer

    Okay I should have said it looks to me that the main mast is partially or un-stayed. ;) The chanplates, shrouds, and turnbuckles on the mizzen are obvious, not so (to me) on the main. There do appear to be a couple of light runners with small tackles attached running to the bulwark just forward of the pilothouse. If I was responsible for this design I would have included these just to keep the stick under control (which is where I get partially stayed).

    Phil was partial to big full-battened gaff sails on un-stayed masts. With a jib set flying........
     

  15. DCockey
    Joined: Oct 2009
    Posts: 3,824
    Likes: 127, Points: 63, Legacy Rep: 1485
    Location: Midcoast Maine

    DCockey Senior Member

    Phuma's main mast has stays. Also, it appears to me that the masts are metal, possibly galvanized steel light poles or sign poles. Attached images are crops from photos I took in July 2012 in Eureka, California.

    Information about Phuma from documentation record http://www.st.nmfs.noaa.gov/pls/webpls/cgv_pkg.vessel_name_list:
    Vessel Name: PHUMA USCG Doc. No.: 970996
    Vessel Service: COMMERCIAL FISHING VESSEL IMO Number: *
    Trade Indicator: Coastwise Unrestricted, Fishery Call Sign: *
    Hull Material: STEEL Hull Number: 32
    Ship Builder: J A GAST Year Built: 1991

    Length (ft.): 121.1
    Hailing Port: ARCATA CA Hull Depth (ft.): 8.9
    Owner: Hull Breadth (ft.): 16
    Gross Tonnage: 148
    Net Tonnage: 44
    Documentation Issuance Date: April 01, 1998 Documentation Expiration Date: April 30, 2001

    Previous Vessel Names: PHUMA WAGL205
    Previous Vessel Owners: AHR COMPANY INC
    AHR COMPANY INC​

    Paragraph about Phuma from The North Coast Journal, 06 December 2012 http://www.northcoastjournal.com/humboldt/backyard-of-boats/Content?oid=2185428
     

    Attached Files:

    Last edited: Mar 20, 2014
Forum posts represent the experience, opinion, and view of individual users. Boat Design Net does not necessarily endorse nor share the view of each individual post.
When making potentially dangerous or financial decisions, always employ and consult appropriate professionals. Your circumstances or experience may be different.