Results 1 to 14 of 14

Thread: repair of a wooden mast

  1. #1
    Join Date
    Dec 2018
    Location
    netherlands
    Posts
    4

    Default repair of a wooden mast

    Hi I am a long time woodenboat reader. I also race a Friesian steel flatbottomed barge called Skūtsje built in 1905. www.doekevanmartena.nl .The mast is normally bent and is tensioned up on the forestay with around 1000 kg for racing so if there is a mast problem we know when we tension up. The mast is made up of 6 section glued up, total thickness at the base maybe 400 mm and the length around 15 m. Our mast and boom, both Oregon pine as far as I can tell, has a lot of cracks in the wood from drying. I do not want to fill these with anything but wood and my repair plan is to router out the cracks to a groove about 30 to 40 mm deep and glue in a plank with epoxy glue. After hardening I will remove the excess plank and fair the mast. There are maybe 30 cracks in total around the mast over the length, most about I metre in length. I want to use a router with rounded bottom and planks with a rounded edge, of the same material which will expand and contract with the same setting. As an alternative I am thinking red cedar which is more forgiving, less strong and less likely to induce new cracks. Any thoughts on this?

  2. #2
    Join Date
    Aug 2005
    Location
    SF Bay Area- Richmond
    Posts
    15,577

    Default Re: repair of a wooden mast

    Oooh, a tough call! Can you post photos? I'll let the more experienced folks answer, but I do know you should use a flexible epoxy like G-Flex. Remember that the wood splines will expand and contract but the epoxy won't nearly as much...

    A mast is a critical part of the boat, and failure can be dangerous if not just expensive -- don't ask me how I know this. Do you have access to anyone at nearby wooden boat centers / schools? I'd get local knowledge from a spar maker if at all possible.
    "The enemies of reason have a certain blind look."
    Doctor Jacquin to Lieutenant D'Hubert, in Ridley Scott's first major film _The Duellists_.

  3. #3
    Join Date
    Jan 2010
    Location
    Northern Europe
    Posts
    9,569

    Default Re: repair of a wooden mast

    Would need to see how big these "cracks" are. My last spar dried out over the first year and opened up in a few places, not big enough to warrent putting in splines, in my opinion, so got filled with epoxy. Seems to have been stable since, but its still hanging in the roof.



    Open up each end of the split with a forstner bit, it relieves stress/stops it spreading.

  4. #4
    Join Date
    Jun 2010
    Location
    PNW, an island west of Seattle
    Posts
    1,805

    Default Re: repair of a wooden mast

    It is not clear to me what "6 section glued up," means.

    Jeff

  5. #5
    Join Date
    Dec 2018
    Location
    netherlands
    Posts
    4

    Default Re: repair of a wooden mast

    Hi all and thanks for the advice.
    To answer Jeff the mast is made up of 6 parts glued together rather than a single bole. The masts for reacing are made up bent about 1 metre out backwards in 15 metres and we pull the top straight with the front rigging to get a good stiff mast.

    I have looked at filling the splits with epoxy but my concern is that the difference in material will cause more splits. Aside from that, currently the splits are full of varnish so the epoxy would not get much grip and would likely be pushed out. We know that the wood underneath is healthy so that is why I want fill up the splits and keep the interior planks dry.
    Nice detail on the filled splits @scaraborgcraft. that micht work for us as well. I am thinking a 20mm drill and a wood dowell to peg the hole and relieve the strain around the edges. I have seen that in folded metal constructions. @Thorne: I agree that wood splines could expand. For that reason I would maybe look at red cedar which is quite soft for the spline wood. Even with the current situation our mast is strong enough, we took it out in a full 5 with full sail which for a racing Skūtsje is a lot , running us at over 9 knots. We have some issues in the top end but that can be repaired. And true for safety sake we need to be carefull, we have 13 aboard in a race, and I am the one under the mast on the main winch and sail trim ;-) setting the gaff on each course. We had a local mastmaker who does a lot of work for the fleet (there are around 180 Skūtses in the racing fleet) and he warned us of some issues in the top. I figure we can only make it better. In fact he did mention that the front and rear planks where we have splits should have been quarter sawn. They clearly were not, but that is done and cannot be undone.
    Any ideas on using a softer wood spline, such as red cedar?
    Thanks for all the feedback!
    Paul

  6. #6
    Join Date
    Oct 2005
    Location
    The Netherlands
    Posts
    720

    Default Re: repair of a wooden mast

    Perhaps the inland red cedar would be even better: The guys at the sawmill Van Leersum told me it is less britle then the imported stuff and tougher. Alan Vet, Evecom, is the man for epoxy. He started using it as one of the first in the country. His epoxy is a bit more flexible then West. Frank
    Www.oarandsail.nl

  7. #7
    Join Date
    Nov 2004
    Location
    Port Townsend WA
    Posts
    11,894

    Default Re: repair of a wooden mast

    You are wise to be aware of the fact that a solid filler of those cracks can possibly cause the cracks to open as the wood swells and shrinks with changes in humidity! This action is almost akin to driving a splitting wedge into the wood! A soft filler was used in times past in order to allow the wood to change dimensions without splitting. This would be either pitch which is the traditional filler or Dolfinite Bedding compound which has a reputation of being an ideal product for this kind of use.
    Even G/Flex epoxy is not all that good for this application because semi flexible fillers can reach a point of their crushing limits and then cause damage as well.
    Jay

  8. #8
    Join Date
    Dec 2018
    Location
    netherlands
    Posts
    4

    Default Re: repair of a wooden mast

    Thanks for all the good advice. I think I will go with a softer commercial grade of red cedar which is used here as building cladding and a round dowell at the end to spread the load. I use a local brand of Epoxy from Duursma who produces a 2:1 mix ratio which is forgiving enough to eyeball the mix. It is glue rather than structural and I have used it in the past to make a stitch and glue kayak, a strip built proa and an electric whitehall launch, so I trust it. Time to write the repair plan!
    Thanks again,

    Paul

  9. #9
    Join Date
    Mar 2014
    Location
    Hasslö, Blekinge, Sweden
    Posts
    643

    Default Re: repair of a wooden mast

    I'm not entirely sure you really need to do anything.
    Our ships boats all have masts with multiple cracks and they seems to last, I believe the oldest mast was made in the 80ies. Well, some got problems with rot, they incidently had the cracks filled with putty...
    There are some advocating that a varnished (or painted) mast is problems waiting to happen since water is trapped inside, but I don't really believe that's true.

    ETA: If you manage to create voids inside the mast you may be in trouble a few years from now.

    /Mats
    Last edited by mohsart; 12-02-2018 at 07:10 AM.
    Yes the avatar depicts me; yes I drew the comic boat pic, it's a joke on the pop song I'm not a robot by Marina and the diamonds

  10. #10
    Join Date
    Apr 1999
    Location
    Hyannis, MA, USA
    Posts
    45,830

    Default Re: repair of a wooden mast

    mohsart may be on to something. Pix would help. Does the mast swell and the cracks shrink with moisture? How long is the mast out of the boat between uses? How stored?

    I'd like some clarity on what you mean by "bent". One possibility is that the spar is bent. When laid out on a bench it has a curve. However your description of pulling the mast more upright or unbent, a most traditional way to use the wood's flex strength in lieu of a backstay, it sounds like the mast could be a straight stick that when put in place, the partners being centered a tad abaft the step, the mast rakes aft until the head stay pulls it more upright. That will induce a bend with an apex at the partners. Maybe some pix of the stick up would help me understand. Sounds like a very cool boat.

    G'luck

  11. #11
    Join Date
    Dec 2018
    Location
    netherlands
    Posts
    4

    Default Re: repair of a wooden mast

    Hi There and thanks for the advice.
    My first instict was to do nothing as the bend strength is hardly hampered by a vertical split. Its just that we have a lot of them and that will not be good for torsional stiffness. The load on the mast could induce it to twist and the combination of torsion load and bend is a mastbreaker it would occur. The mast is used on a racer with a lot of sail :14 tons of iron . And to answer Ian: the mast is assembled out of 6 pieces of oregon pine and laminated together with a bend, mostly in the top end. We can also trim the boards forward and back to keep her neutral on the helm and we constantly trim the gaff top, inhaul, outhall and cunningham during a race. Great fun and hard work. I used to run a competiton ready Finn class and could never keep up with them, on any course untill I went to a full plane on a reach.

  12. #12
    Join Date
    Oct 2008
    Location
    Walney, near Cumbria UK
    Posts
    41,812

    Default Re: repair of a wooden mast

    Quote Originally Posted by schut58 View Post
    Hi There and thanks for the advice.
    My first instict was to do nothing as the bend strength is hardly hampered by a vertical split. Its just that we have a lot of them and that will not be good for torsional stiffness. The load on the mast could induce it to twist and the combination of torsion load and bend is a mastbreaker it would occur. The mast is used on a racer with a lot of sail :14 tons of iron . And to answer Ian: the mast is assembled out of 6 pieces of oregon pine and laminated together with a bend, mostly in the top end. We can also trim the boards forward and back to keep her neutral on the helm and we constantly trim the gaff top, inhaul, outhall and cunningham during a race. Great fun and hard work. I used to run a competiton ready Finn class and could never keep up with them, on any course untill I went to a full plane on a reach.
    I can't see much that would induce twist in the mast, all of the loads are applied so close to the axis that there is little in the way of a couple to apply a twisting moment.
    I would consider keeping the wet out with something like beeswax and lard to produce a soft water repellent, adhesive filler. If you are afraid of the splits continuing to run drill the ends and glue in a cross grain plug as a crack arrester.
    It really is quite difficult to build an ugly wooden boat.

    The power of the web: Anyone can post anything on the web
    The weakness of the web: Anyone can post anything on the web.

  13. #13
    Join Date
    Jun 2018
    Location
    Southeast MA, USA
    Posts
    59

    Default Re: repair of a wooden mast

    As Nick said, we used to fill cracks in large schooner masts witha soft water repellant adhesive filler. We melted some beeswax and mixed it with raw linseed oil.

  14. #14
    Join Date
    Mar 2014
    Location
    Hasslö, Blekinge, Sweden
    Posts
    643

    Default Re: repair of a wooden mast

    +1 for beesway and linseed oil, or my favorite product tallow.
    But I think that any filling may cause more problems than they cure; if the cracks are open they are ventilated, if you seal them up you may end up with voids where the water stays and rot begins.

    /Mats
    Yes the avatar depicts me; yes I drew the comic boat pic, it's a joke on the pop song I'm not a robot by Marina and the diamonds

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •