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Thread: Formosa Sitka Box Mast/Spar Repair Advice

  1. #1
    Join Date
    Apr 2018
    Location
    New Orleans, LA, USA
    Posts
    7

    Question Formosa Sitka Box Mast/Spar Repair Advice

    Im helping a buddy with some sitka mast repairs on his formosa. The box seems to be splitting apart along many seams that have not been splined in the past. It seems like the previous owner routed it out or just used the kerf on a portable saw to cut a channel where thyve glue splines in. My buddy wants to replace the mast and sail gaff rigged down the road so he is hesitant to split it open and reglue (and I believe that may be a lot of work with the splines already glued into place). The foot of the mast (haven't gotten to get a close look) appears to have worse glue failure/seperation and and there is a scraph popping out where glue has failed and wood is warping toward the top. My feeling is that since he wants to do this all on the boat I should continue with the splines where its opening up now but I am wondering how you all feel about that and how I should proceed on scarps repair and heel. After that, the mizzen boom is showing some signs of rot and fungus and has started checking badly. Inside the checks all seems solid some of the poor carpenter bee repairs I think have leet to a little water intrusion. My intuition was to just start pouring boat soup in those checks and see how it goes with a plan to replace the spar. But I was worried that pouring that much oil in there would make it hard on the glue if I decided to grave a big piece in down the road. Thoughts? Warnings? Ideas? I really appreciate them all. ALSO, Ive searched for more information on here but can't quite find this situation at hand, please link me if this is well covered, which I assumed it was. My previous reading has led me to believe that using Doug fir should be fine for splining in the sitka.

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    Thank you so much,
    Rush Jagoe

  2. #2
    Join Date
    Nov 2004
    Location
    Port Townsend WA
    Posts
    14,363

    Default Re: Formosa Sitka Box Mast/Spar Repair Advice

    One thing that needs caution when scarfing a patch into a box section mast is a bull nose rabbet plane such as a Shop Fox Bull Nose Plane. https://www.amazon.com/Woodstock-D37...Plane/dp/B005W This is a copy of the old Stanly 90 plane. A Stanly 92 is also a must for every serious wooden boat builder to have in his kit! These two rabbet planes were the first essential specialty planes I bought for myself over sixty five years ago. They have served me very well over the years!
    https://www.amazon.com/Stanley-12-14...-Chisel/dp/B00
    With these planes you can cut the inside rabbet for the scarf joint accuratly. Be sure to add a vertical support block inside of of the joint to allow pressure for clamping. This should be a relatively thin piece no less than 3/4" in thickness. This will insure ventilation and drainage but is needed for one plane of the scarf on the inside rabbets. A crook necked flat chisle is nice if you have one.
    Jay

  3. #3
    Join Date
    Mar 2011
    Location
    Mukilteo, WA
    Posts
    3,065

    Default Re: Formosa Sitka Box Mast/Spar Repair Advice

    A delaminating marconi mast of thin wall box section is not something you can cure with boat soup. I would be afraid of catastrophic failure, and afraid enough not to sail it until fixed. I have a set of old soft formosa masts out back just barely holding up my lumber pile, so I know what you are looking at. They are spruce I believe, not at all rot resistant, and certainly not glued with epoxy. Unfortunately, every one of those glued joints is critical. Frankly, if its got rot already, and is also coming unglued, I think its time to condemn the whole thing. It can be fixed, but will still have a short life once the rot has taken hold.

    To fix it, you'll really have to get the masts down, run a circle saw down every seam and glue in new splines, it would be pretty quick. Maybe do one long seam at a time so it all doesn't fall apart. Scarf a whole new heel on where the rot is.

    Or better yet, start the gaff conversion now.

  4. #4
    Join Date
    Apr 2018
    Location
    New Orleans, LA, USA
    Posts
    7

    Default Re: Formosa Sitka Box Mast/Spar Repair Advice

    Thank you Jay! My only experience with graving is in graving in pieces on lapstrake planking with a lot of bad knots. And with scarfing it's all be new planking scarphs, not repairs. I was using mostly flat chisels and a Stanley 71 for the knot graving. Ill need to rely more on my hand tools for this since Ill have to cut everything out at the shop and just tune it on the boat. These bull nosed planes look like they'd be much more efficient along with that crooked neck chisel! Thanks for the advice.


    Quote Originally Posted by Jay Greer View Post
    One thing that needs caution when scarfing a patch into a box section mast is a bull nose rabbet plane such as a Shop Fox Bull Nose Plane. https://www.amazon.com/Woodstock-D37...Plane/dp/B005W This is a copy of the old Stanly 90 plane. A Stanly 92 is also a must for every serious wooden boat builder to have in his kit! These two rabbet planes were the first essential specialty planes I bought for myself over sixty five years ago. They have served me very well over the years!
    https://www.amazon.com/Stanley-12-14...-Chisel/dp/B00
    With these planes you can cut the inside rabbet for the scarf joint accuratly. Be sure to add a vertical support block inside of of the joint to allow pressure for clamping. This should be a relatively thin piece no less than 3/4" in thickness. This will insure ventilation and drainage but is needed for one plane of the scarf on the inside rabbets. A crook necked flat chisle is nice if you have one.
    Jay

  5. #5
    Join Date
    Apr 2018
    Location
    New Orleans, LA, USA
    Posts
    7

    Default Re: Formosa Sitka Box Mast/Spar Repair Advice

    Thank you! I definitely wasn’t thinking boat soup for that delaminating box. But was thinking about it for the solid Sitka mizzen boom where checking is present.

  6. #6
    Join Date
    Dec 2003
    Location
    Portland, Oregon
    Posts
    66,602

    Default Re: Formosa Sitka Box Mast/Spar Repair Advice

    Quote Originally Posted by J.Madison View Post
    A delaminating marconi mast of thin wall box section is not something you can cure with boat soup. I would be afraid of catastrophic failure, and afraid enough not to sail it until fixed. I have a set of old soft formosa masts out back just barely holding up my lumber pile, so I know what you are looking at. They are spruce I believe, not at all rot resistant, and certainly not glued with epoxy. Unfortunately, every one of those glued joints is critical. Frankly, if its got rot already, and is also coming unglued, I think its time to condemn the whole thing. It can be fixed, but will still have a short life once the rot has taken hold.

    To fix it, you'll really have to get the masts down, run a circle saw down every seam and glue in new splines, it would be pretty quick. Maybe do one long seam at a time so it all doesn't fall apart. Scarf a whole new heel on where the rot is.

    Or better yet, start the gaff conversion now.
    I'd agree with most of this.

    The key issues is whether the Sitka in the mast is sound. If not - new mast. If it is, then unstepping, splitting it open at the seams, and re-gluing is the ticket... and no new mast needed... short term or medium term. The adhesives typically used for those older box-section spars had a definite liftime. Once exceeded, as I suspect this one has, it's gonna open up everywhere. I repaired one that was mostly held together by hardware and rigging and varnish. Once everything was stripped off... I could take most of it apart with my bare hands.

    So, I agree, any partway repairs will be only short term fixes, and I wouldn't be comfortable trusting it.
    David G
    Harbor Woodworks
    https://www.facebook.com/HarborWoodworks/

    "It was a Sunday morning and Goddard gave thanks that there were still places where one could worship in temples not made by human hands." -- L. F. Herreshoff (The Compleat Cruiser)

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