Page 1 of 8 12 ... LastLast
Results 1 to 35 of 251

Thread: Making a birdsmouth catboat mast

  1. #1
    Join Date
    Nov 2006
    Posts
    8,278

    Default Making a birdsmouth catboat mast

    It was not my intention to build a birdsmouth mast in the middle of winter. The cold temperatures make even gluing a scarf complicated, forget about the long birdsmouth joints.

    The problem is, the lumber is sitting under the boat. I have to relocate it in order to clear the area underneath the boat for planking the bottom. It just seems a shame to move the pile somewhere else without reducing and subtracting some wood.

    These are the first steps...







    Last edited by Jim Ledger; 07-21-2017 at 09:19 AM.

  2. #2
    Join Date
    Dec 2001
    Location
    Too far inland.
    Posts
    8,905

    Default

    What is the finished length?
    (Just for some sense of the scale of the undertaking)
    No adversary is worse than bad advice.

  3. #3
    Join Date
    Nov 2006
    Posts
    8,278

    Default Re: Making a birdsmouth catboat mast

    Thirty nine feet, eight and a half inch diameter at the deck. The lumber is vertical grain Doug Fir, 1 7/8" thick by 8" wide, mostly sixteen footers.

    The first thing to do was to scrub the scurf off one face in order to have a clean surface, reasonably flat, to mark with an ink line...



    Last edited by Jim Ledger; 07-19-2017 at 06:40 PM.

  4. #4
    Join Date
    May 2009
    Location
    Fort Worth, Texas, USA
    Posts
    2,145

    Default Re: Making a birdsmouth catboat mast

    More detail.
    The ink line is to set the taper??

  5. #5
    Join Date
    Apr 2009
    Location
    Mountain lakes of Vermont
    Posts
    11,181

    Default Re: Making a birdsmouth catboat mast

    Almost 40' ! Wow! We've seen a lot of small birdsmouth spars put together on this Forum, but nothing nearing that size. Eagerly looking forward to the process.
    I was born on a wooden boat that I built myself.

  6. #6
    Join Date
    Nov 2006
    Posts
    8,278

    Default Re: Making a birdsmouth catboat mast

    Quote Originally Posted by upchurchmr View Post
    More detail.
    The ink line is to set the taper??
    Details emerging as they happen.

    The ink line is similar to a chalk line except the line is finer and it uses ink instead if chalk. The result is a very visible thin line. I believe that both Jay Greer and KC8PQL use one, and that's good enough recommendation for me.

    The aim is to cut a straight line down the center of each piece with a Skilsaw, then hand plane the new edge straight and square. The pieces will be left wide, birdsmouth machined in, scarfed together full length...and only then cut to the taper.

    The ink line...you might notice some sapwood on this piece. This is the only one with sap and that half won't get used as a stave, maybe blocking, maybe something else.



    Last edited by Jim Ledger; 07-19-2017 at 06:41 PM.

  7. #7
    Join Date
    Sep 2009
    Location
    Saint Helena Island, SC
    Posts
    9,428

    Default Re: Making a birdsmouth catboat mast

    Quote Originally Posted by Jim Ledger View Post
    The lumber is vertical grain Doug Fir, 1 7/8" thick by 8" wide, mostly sixteen footers.



    Man do I need some of that for my chine logs!
    Nice.
    Fight Entropy, build a wooden boat!

  8. #8
    Join Date
    Sep 2003
    Location
    Brunswick, Maine
    Posts
    1,501

    Default Re: Making a birdsmouth catboat mast

    Two scarf joints per stave, nicely laid out on a helix up the mast, I'd venture to guess?
    (Longtime lurker on your other thread! )

  9. #9
    Join Date
    Apr 2007
    Location
    Singapore
    Posts
    11,895

    Default Re: Making a birdsmouth catboat mast

    Just be sure to save at least 9-10" of your offcuts. .. . .

  10. #10
    Join Date
    Apr 2009
    Location
    Mountain lakes of Vermont
    Posts
    11,181

    Default Re: Making a birdsmouth catboat mast

    Quote Originally Posted by James McMullen View Post
    Just be sure to save at least 9-10" of your offcuts. .. . .
    Eight and a half inch dia mast. That would make one huge beer stein!
    I was born on a wooden boat that I built myself.

  11. #11
    Join Date
    Jan 2003
    Location
    in Orygun
    Posts
    2,685

    Default Re: Making a birdsmouth catboat mast

    Any rough approximation on how much it will weigh?

  12. #12
    Join Date
    Feb 2002
    Location
    Uki, NSW, Australia
    Posts
    26,795

    Default Re: Making a birdsmouth catboat mast

    My 9 metre mast is 212 mm at the partners. The 8 staves are 40mm x 80mm and the timber is Douglas fir. The mast weighed in at 87kgs.
    When I tapered the first stave I then used it as a template for the other 7.

    The plug I made for the bottom 2 metres is also birdsmouth, it was my test run.
    The definition of stupid has got to be the belief that more guns will negate the bloodshed done with guns.

  13. #13
    Join Date
    Jan 2011
    Location
    Norwalk CT
    Posts
    997

    Default Re: Making a birdsmouth catboat mast

    Scurf?
    I love learnin' new stuff...scurf....

  14. #14
    Join Date
    Apr 2009
    Location
    Mountain lakes of Vermont
    Posts
    11,181

    Default Re: Making a birdsmouth catboat mast

    OK, A while ago, we watched you make the solid boom and you've got that squirrelled away somewhere. Now comes the birdsmouth mast. Will the gaff also be birdsmouth to save weight aloft?
    I was born on a wooden boat that I built myself.

  15. #15
    Join Date
    Nov 2006
    Posts
    8,278

    Default Re: Making a birdsmouth catboat mast

    Quote Originally Posted by Rich Jones View Post
    OK, A while ago, we watched you make the solid boom and you've got that squirrelled away somewhere. Now comes the birdsmouth mast. Will the gaff also be birdsmouth to save weight aloft?
    Hi, Rich. Here's the boom from last year. It was cut down out of a solid Fir mast and then eight-sided.








    This is the gaff. It was a gift, a glued-up solid fir spar. Since this picture was taken it has been shaped to eight sides. If I was building it from scratch I would certainly use birdsmouth construction.



    Last edited by Jim Ledger; 07-19-2017 at 06:45 PM.

  16. #16
    Join Date
    Nov 2006
    Posts
    8,278

    Default Re: Making a birdsmouth catboat mast

    Quote Originally Posted by Rob Hazard View Post
    Two scarf joints per stave, nicely laid out on a helix up the mast, I'd venture to guess?
    (Longtime lurker on your other thread! )
    Nope, just a random pattern, widely separated. hopefully the scarfs will be inconspicuous.

  17. #17
    Join Date
    Nov 2006
    Posts
    8,278

    Default Re: Making a birdsmouth catboat mast

    Quote Originally Posted by James McMullen View Post
    Just be sure to save at least 9-10" of your offcuts. .. . .
    After reading your inspiring thread, James I intend doing just that...except instead of a handle I'll be making a seat.

  18. #18
    Join Date
    Nov 2006
    Posts
    8,278

    Default Re: Making a birdsmouth catboat mast

    Quote Originally Posted by Dave Gray View Post
    Any rough approximation on how much it will weigh?
    I'm going to do some figgering on that one. I'll get back to you, Dave.

  19. #19
    Join Date
    Nov 2006
    Posts
    8,278

    Default Re: Making a birdsmouth catboat mast

    Quote Originally Posted by WX View Post
    My 9 metre mast is 212 mm at the partners. The 8 staves are 40mm x 80mm and the timber is Douglas fir. The mast weighed in at 87kgs.
    When I tapered the first stave I then used it as a template for the other 7.

    The plug I made for the bottom 2 metres is also birdsmouth, it was my test run.
    You'll be my go-to, Gary, in case I have any questions. Nice mast.

    First question...do you have any wires running inside?

  20. #20
    Join Date
    Nov 2006
    Posts
    8,278

    Default Re: Making a birdsmouth catboat mast

    Quote Originally Posted by willin woodworks View Post
    Scurf?
    I love learnin' new stuff...scurf....
    Ya wants to let loose with a stream of 'baccy juice after you say that and not quite miss your beard. Try it.

  21. #21
    Join Date
    Nov 2005
    Location
    Montreal
    Posts
    7,469

    Default Re: Making a birdsmouth catboat mast

    Quote Originally Posted by Jim Ledger View Post
    You'll be my go-to, Gary, in case I have any questions. Nice mast.

    First question...do you have any wires running inside?








    Good Morning Mr.Ledger,


    Great to see you able to tackle so many interesting boat bits despite the weather. Has me longing for my dearly departed bow shed like there's no tomorrow!

    You may have to get yourself an antipodean translation dictionary when dealing Gary. Recall, he is the one who not all that long ago made light of his mast with this brilliant pose:


    What some would call heavy, he would probably call light.He's tiger in disguise, he is and not easily dissuaded from manly tasks!

    I hope your mast comes out to a manageable weight.....but not too light,mind you, as I've read how cats like some heft way up front like that....something to do with gentle motions and loose vectors,if I recall.




    Cheers!



    Peter
    Do it,do it,do it,do it,do it,do it,do it,now!
    J.Lennon

    This boat was built with ten thumbs.No fingers were harmed in anyway.

  22. #22
    Join Date
    Sep 2004
    Location
    Ohio
    Posts
    3,512

    Default Re: Making a birdsmouth catboat mast

    Quote Originally Posted by Jim Ledger View Post
    The pieces will be left wide, birdsmouth machined in, scarfed together full length...and only then cut to the taper.
    I tapered mine before machining and scarfing together. I didn't find the thought of handling glued up 50' staves by myself appealing.
    Last edited by kc8pql; 01-07-2014 at 12:07 PM.

  23. #23
    Join Date
    Apr 1999
    Location
    Hyannis, MA, USA
    Posts
    45,806

    Default Re: Making a birdsmouth catboat mast

    Just a warning: A bird's mouth is a great way to use wood but don't go as light as structurally possible. The Chappy shape needs the high weight of a heavy mast to slow her response to waves.

    I've sailed alongside another Chappie, Island Girl. She's glass but the hull weight and distribution were compared when she and Marmalade happened to be in the same yard and they are close as makes no never mind. Yet if there's a little slop in the water Marmalade is quite noticeably faster. After watching both boats with care I realized that Island Girl's motion responding to the sea state was much quicker than Marmalade's and that she was basicly shaking the wind out of her sail. The only difference is Island Girl has an aluminum mast while Marmalade's solid mast weighs quite alot - I don't know how much really but well over 500# though likely less than 900#.

    So, don't worry about making the walls thicker. Unlike the majority of boats, a bit of weight aloft for this hull is a very good thing.

    G'luck

  24. #24
    Join Date
    Mar 2000
    Location
    The land of reefs
    Posts
    32,057

    Default Re: Making a birdsmouth catboat mast

    Don't worry Jim..... You can always fill it with lead shot if it's too light...

  25. #25
    Join Date
    Mar 2002
    Location
    Atlanta
    Posts
    2,335

    Default Re: Making a birdsmouth catboat mast

    Or just make provision for an extra halliard and haul the anchor to the mast head to settle her down when required ...(have actually read of that being done in the distant past) .
    Last edited by Bill Perkins; 01-07-2014 at 03:53 PM.

  26. #26
    Join Date
    Feb 2002
    Location
    Uki, NSW, Australia
    Posts
    26,795

    Default Re: Making a birdsmouth catboat mast

    Quote Originally Posted by Jim Ledger View Post
    You'll be my go-to, Gary, in case I have any questions. Nice mast.

    First question...do you have any wires running inside?
    Yes, I have a VHF cable and a power cable for the mast head light. These run through half inch polypropylene pipe fastened to one stave. Both exit the mast a foot or so above the foot of the mast. Pm me your email address and I'll send you the article I wrote on it.
    The definition of stupid has got to be the belief that more guns will negate the bloodshed done with guns.

  27. #27
    Join Date
    Dec 2001
    Location
    Northern NSW Australia
    Posts
    73,417

    Default Re: Making a birdsmouth catboat mast

    Quote Originally Posted by Ian McColgin View Post
    Just a warning: A bird's mouth is a great way to use wood but don't go as light as structurally possible. The Chappy shape needs the high weight of a heavy mast to slow her response to waves.

    I've sailed alongside another Chappie, Island Girl. She's glass but the hull weight and distribution were compared when she and Marmalade happened to be in the same yard and they are close as makes no never mind. Yet if there's a little slop in the water Marmalade is quite noticeably faster. After watching both boats with care I realized that Island Girl's motion responding to the sea state was much quicker than Marmalade's and that she was basicly shaking the wind out of her sail. The only difference is Island Girl has an aluminum mast while Marmalade's solid mast weighs quite alot - I don't know how much really but well over 500# though likely less than 900#.

    So, don't worry about making the walls thicker. Unlike the majority of boats, a bit of weight aloft for this hull is a very good thing.

    G'luck
    Your certainly right on the advantages of extra weight aloft on a traditional hull shape. Light masts may not be what the designer had in mind.
    '' You ain't gonna learn what you don't want to know. ''
    Grateful Dead

  28. #28
    Join Date
    Dec 1999
    Location
    Eagan, Minnesota, USA
    Posts
    11,133

    Default Re: Making a birdsmouth catboat mast

    It's not just the weight, but where it is.
    Await dreams, loves, life; | There is always tomorrow. | Until there is not.

    Grieving love unsaid. | Tomorrow will fail someday. | Tell them today, OK?

  29. #29
    Join Date
    Nov 2006
    Posts
    8,278

    Default Re: Making a birdsmouth catboat mast

    These boards are 1 3/4" thich by 3 3/4" wide. An average weight, after cutting the birdsmouth is 1 1/2 pounds per foot. Times eight gives 12 pounds per foot of mast. This will be the case right up to the throat halyard block. Above that the mast tapers quickly. However, some of the mast will be filled solid. On the other hand some gets planed off. Using the maximum diameter times forty feet the weight comes out to 480 pounds. It'll probably be a bit less.

    All are welcome to guess the final weigh at any time during the proceedings and after it's glued up and shaped I'll weigh it.

    So, it's certainly not light, nor is it pushing any design limits. It's well within established birdsmouth rule-of-thumb guidelines for wall thickness.

    Most of the boards sprung when ripped, as this one did. This one was the worst, each half bowed about a half inch. None sprung the other way and some hardly moved at all.



    Last edited by Jim Ledger; 07-19-2017 at 06:46 PM.

  30. #30
    Join Date
    Feb 2002
    Location
    Uki, NSW, Australia
    Posts
    26,795

    Default Re: Making a birdsmouth catboat mast

    I used the calculators on this site to work out the specs for my mast.
    http://www.duckworksmagazine.com/04/...outh/index.cfm
    The definition of stupid has got to be the belief that more guns will negate the bloodshed done with guns.

  31. #31
    Join Date
    Oct 2007
    Location
    Above flood level, NSW, Australia
    Posts
    17,715

    Default Re: Making a birdsmouth catboat mast

    I seem to remember an article in the not too distant past in our hosts' magazine about a big replica catboat that had rods of carbon fibre routed an epoxied into the back of the mast staves prior to the final glue up which made the whole thing immensely strong for a hollow mast, compared to a solid stick.

    I could see how a heavy mast amidships may make for a gentler/smoother roll considering how much buoyancy there is there compared to the stem, so I'm still trying to work out how this same effect can be garnered from having a heavy stick up front. I'd personally want a bit of stiffness in a boat because those slower motions just make me go green at the gills.

    As always I'm sure to learn something else here Jim! Carry on...
    Jarndyce and Jarndyce

    The Mighty Pippin
    Mirror 30141
    Looe
    Dragon KA93

  32. #32
    Join Date
    Nov 2006
    Posts
    8,278

    Default Re: Making a birdsmouth catboat mast

    Quote Originally Posted by P.L.Lenihan View Post
    Good Morning Mr.Ledger,


    Great to see you able to tackle so many interesting boat bits despite the weather. Has me longing for my dearly departed bow shed like there's no tomorrow!

    You may have to get yourself an antipodean translation dictionary when dealing Gary. Recall, he is the one who not all that long ago made light of his mast with this brilliant pose:


    What some would call heavy, he would probably call light.He's tiger in disguise, he is and not easily dissuaded from manly tasks!

    I hope your mast comes out to a manageable weight.....but not too light,mind you, as I've read how cats like some heft way up front like that....something to do with gentle motions and loose vectors,if I recall.




    Cheers!



    Peter


    Yes, Peter, a fine figure of a man is our Gary, if I didn't know he was from Down Under I'd swear he was from Texas. However, I doubt I'll be trying to match his mighty feat...it's not so much the picking up but the putting back down that would get me.


    Back to the business of birdsmouth building. The first operation was to run the staves through the planer, not worrying overmuch about cleaning off every patch of scurf, favoring rather to keep all the thickness possible.

    Following a nice thicknessing I set up a shaper to cut the birdsmouth, as can be seen here.







    Last edited by Jim Ledger; 07-21-2017 at 09:20 AM.

  33. #33
    Join Date
    Nov 2006
    Posts
    8,278

    Default Re: Making a birdsmouth catboat mast

    Quote Originally Posted by kc8pql View Post
    I tapered mine before machining and scarfing together. I didn't find the thought of handling glued up 50' staves by myself appealing.
    Fifty feet is too much, agreed, but I think thirty-nine might be doable. In any case we'll find out soon enough.

    Here's the shaper set-up. Two passes were taken on a forty-five degree cutter, although the cutter is a little hard to see in the picture.. A nice fence was put together just for the occasion. Actually, after the first few passes I changed the direction of feed, so the machine was climb-cutting. This reduced chip-out to nothing while blowing tons of dust into the shop. A good trade-off. You can climb cut on a shaper only if you're using a power feed, never try this feeding by hand as the piece will be flung with great force through whatever happens to be in the way.



    Last edited by Jim Ledger; 07-19-2017 at 06:48 PM.

  34. #34
    Join Date
    Nov 2006
    Posts
    8,278

    Default Re: Making a birdsmouth catboat mast

    Quote Originally Posted by Ian McColgin View Post
    Just a warning: A bird's mouth is a great way to use wood but don't go as light as structurally possible. The Chappy shape needs the high weight of a heavy mast to slow her response to waves.

    I've sailed alongside another Chappie, Island Girl. She's glass but the hull weight and distribution were compared when she and Marmalade happened to be in the same yard and they are close as makes no never mind. Yet if there's a little slop in the water Marmalade is quite noticeably faster. After watching both boats with care I realized that Island Girl's motion responding to the sea state was much quicker than Marmalade's and that she was basicly shaking the wind out of her sail. The only difference is Island Girl has an aluminum mast while Marmalade's solid mast weighs quite alot - I don't know how much really but well over 500# though likely less than 900#.

    So, don't worry about making the walls thicker. Unlike the majority of boats, a bit of weight aloft for this hull is a very good thing.

    G'luck
    Thanks, Ian, I remember you giving me this particular piece of advice last year at Mystic. Not to worry, I think there will still be a substaintial amount of weight to the mast. I also remember you saying that you didn't have any ballast in Marmalade. Does Island Girl carry any? Brewer calls for two thousand pounds, although finding a good place to put it down low is not an easy problem. I originally sailed Sea Rover without ballast, and putting in four hundred pounds did wonders damping the motion of the boat and helping it carry through the chop.

    Here are some of the completed staves .The thickness worked out to a heavy inch and three quarters. They were milled without jointing, other than hand planing the saw marks. Consequently the edges are not exactly straight. This leaves the maximum amount of width to play with. Gluing up on a jig will pull them into line nicely.



    Last edited by Jim Ledger; 07-19-2017 at 06:49 PM.

  35. #35
    Join Date
    Nov 2011
    Location
    Virolahti,Finland
    Posts
    210

    Default Re: Making a birdsmouth catboat mast

    Quote Originally Posted by Jim Ledger View Post
    then hand plane the new edge straight and square. The pieces will be left wide, birdsmouth machined in, scarfed together full length...and only then cut to the taper.
    I made Mary III mast the same way, tapering after, mast is 50 feet spruce. Only disadvantage was that I needed helper to carry pieces.
    Spruce is light, mast wooden weight is 115 kg.
    I have no fancy machines, I made birdsmouth with table saw, two 45 decree cuts, after that with hand plane.
    Matti

Posting Permissions

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