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Thread: Inspecting wooden masts

  1. #1
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    Default Inspecting wooden masts

    Last week, my sharp-eyed wife spotted a small soft spot near the bottom of our 50-foot mainmast. It looked innocent enough until I started probing with an awl. Turns out there is some significant dry rot down there.

    The mast was built about 40 years ago in Germany. It is hollow, rectangular shaped, with solid core at the base, and probably at the top, and at the two sets of spreaders. The wood looks like some sort of fir.

    The mast is stepped on deck, in a well drained steel box. Either water is being sucked upwards from the deck into the bottom of the mast (doubtful, but the best case scenario), or water is getting in from above somewhere, draining down to the foot, where it seeps into the core and causes softening and rot.

    I plan to pull the mast next week, and to scarf in a new base. My question is, how can I inspect the rest of the mast, to make sure there arenít other problem areas, like at the spreaders?

    There is also a mizzen mast, which doesnít show any problems, but how can I find out for sure?

    This is a blue water boat that needs to be strong and trustworthy. We were recently hove to off Cape Hatteras for 10 hours in a 45 knot blow. The next time that happens, I donít want to be fretting about the integrity of either mast.

    Thanks in in advance for any ideas.

  2. #2
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    Default Re: Inspecting wooden masts

    Tap it with a small mallet. Punky wood sounds dull, good timber has more of a ring to it. Try it on the bit that you know is punky to learn the different sounds.
    It really is quite difficult to build an ugly wooden boat.

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    Default Re: Inspecting wooden masts

    Brings back some memories of the dreaded rot discovery a week before relaunch way back when. That was a big mission and learning curve for me.
    What you say implies paint rather than varnish. I think just meticulous checking visually and the awl,expose any suspected areas. The only alternative is to wood it, but if you get to that ,perhaps you could target the danger spots . Masthead, spreaders, gooseneck, vang if there is one....any fastening or piercing, mast track.

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    Default Re: Inspecting wooden masts

    There are many ways for moisture to get into the wood of a hollow wooden mast. Firstly, it's there in the lumber. Secondly, older and/or improperly bedded fastenings - all those screws for the track, spreaders, stay tangs, truck blocks - hundreds of ways in. Sometimes rot can develop at those sites. But more often the moisture is evaporated out of the wood on hot days. Most paints are fairly vapor proof so the vapor evaporates to the air in the hollow of the mast. When things cool a bit, that vapor condenses on the inner walls of the mast and then rolls down.

    Thirty six years ago I learned about this as I probed extensive rot at the partners in Goblin's sixty-something year old foremast. Many hollow masts have compression blocks at key places, notably the partners and spreaders. Goblin's were solid, so the moiisture rolled to there and settled in to making rot. In my repair I gave the new compression block a shallow inverted cone shape down to a weep hole. I also attended to some rot at the top of the solid butt of the mast and put a back slope to an aft side weep hole there. And I made sure the step had weeps.

    With this lesson firmly in mind, I double checked the spar maker for Meg's sticks and found that she absolutely knew this and always provided for drainage past compression blocks.

    Don't be afraid to rip out mast rot. Buy some sitka spruce and scarf in new, duplicating the structure already in the mast. If you have a major chunk to take out, like a fully broken mast, measure first so what you do ends up the same size as the original. Then duplicate the structure with a plug and "cloths pin scarf" (12:1 - It's a mast) everything back together.

    With imagination for the typography: ===========>=====<===========

    Note how the sharp male ends are on the original and face each other leaving the plug with a female at each end. This is because it's easier to handle and manipulate the plug and the female ======< is harder to make accurately. Even at that, I make the females first and then worry fit the male ends. You want really clean surfaces and a fine glue line as fillers tend to make hard points where they fill imperfect work.

    G'luck

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    Default Re: Inspecting wooden masts

    An old fart told me once...
    Hold a watch against one end of the spar and put an ear on the other end of the spar.
    tic tic tic is good
    digi watch not so good

  6. #6
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    Default Re: Inspecting wooden masts

    Quote Originally Posted by wizbang 13 View Post
    An old fart told me once...
    Hold a watch against one end of the spar and put an ear on the other end of the spar.
    tic tic tic is good
    digi watch not so good
    The Hudson Bay Company boat builders did that with the logs that they were selecting for the keels of their craft. Do not know if it would work for a hollow box mast though.
    It really is quite difficult to build an ugly wooden boat.

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  7. #7
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    Default Re: Inspecting wooden masts

    Yes, the masts are painted, unfortunately.

    Ideas for inspecting other area,so far:

    - tapping with a plastic hamme
    - probing with an awl
    - removing the paint in select areas to check for discoloration

    What about taking core samples, as they do with trees?

    https://en.m.wikipedia.org/wiki/Increment_borer

    It’s going to be a big job to pull mast, fix known problem at base, paint mast, re-bed all hardware, etc. I want to make sure I find and fix all the problem areas while I have the mast down.

  8. #8
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    Default Re: Inspecting wooden masts

    John, just a suggestion - any chance you could use a fiber-optic scope to 'see' inside the mast. I hope this is not too far-fetched an idea.


    Rick

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    Default Re: Inspecting wooden masts

    Quote Originally Posted by hawkeye54 View Post
    John, just a suggestion - any chance you could use a fiber-optic scope to 'see' inside the mast. I hope this is not too far-fetched an idea.


    Rick
    Thatís a terrific idea. I just got one for inspecting inside tanks and hard to reach places.

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    Default Re: Inspecting wooden masts

    Quote Originally Posted by jalmberg View Post
    Thatís a terrific idea. I just got one for inspecting inside tanks and hard to reach places.
    I was going to suggest that too but I still think systematically tapping, prodding with an awl or small screwdriver and stripping paint to inspect is the best way. Allow for a lot more time and do it properly
    whatever rocks your boat

  11. #11
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    Default Re: Inspecting wooden masts

    You can buy boroscopes that connect to a mobile phone very easily and cheaply these days. As long as you like too.

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    Default Re: Inspecting wooden masts

    Jberg,
    Wood spars need careful maintenance, paint finishes make that vigilance all the more important, when you have them down, you will need to strip at least the affected area to assess and repair the full extent of the damage, many spars are damaged from water intrusion further up, likely entering at wire runs ( do look to proper service loops and small cowl covers for all wire entrances)... The spar should have drainage provisions through all of the blocking, to allow any water making its way in a ready exit, it is alarming how frequently that step is neglected.
    The good news is that box spars are readily repairable and once you put her back as original, with either better drainage, or better maintenance, or both, she will live to serve for many years.
    Best of luck, Steve

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    Default Re: Inspecting wooden masts

    I use a fiber optic for inspection of areas that can't be reached otherwise. But it can be difficult to intemperate what is seen. You are fortunate that this is a box section mast as it will be easier to splice than a round one. The lower area of a box mast is often doubled up in thickness from the butt to the gooseneck. Some builders do not take the time to bevel off the upper end of the doubling and seal the inner components which, results in drain water saturating that section and causing rot to develop. You might want to check the photos of the box section mast repair we did on our H28 ketch "Bright Star". They might be of help to you as you can see the temporary spar bench we made.

    Wishing you good luck for an easy repair.
    Jay

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    Default Re: Inspecting wooden masts

    am finishing a very similar job now. borescope is cheap and fun, but you'll be very hard pressed to gain useful info from it. I used it to help find the extent of blocking and to see if any fasteners projected in there. Looking to see the state of the wood by eye will be impossible unless you find big mushroom heads.

    Take the paint off; all of it. Only way to see what's going on. Usually it's easier to just dive in with both feet than goof around trying to save paint that's probably old anyway and going to be a patchwork after this repair. Once you start you'll wonder why you hesitated.

    I asked the original question to Bruce Tipton before I started this job ("I'm taking an old wood mast out, what do I do to inspect it"), and his response was to go up and down it with a moisture meter -- that will tell you quite a story about where water is moving around in it.

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    Default Re: Inspecting wooden masts

    Okay! The project is underway.

    It turns out that the problem was caused by the mast soaking up water from the deck. Here it is with all the rot cut out.

    Interestingly, we discovered that this is the second time the mast has had to be repaired for this problem. The first repair was not done very well.

    When we re-step the mast, I'm going to bed it down good on a fiberglass pad and LOTS of bedding compound. That should stop the problem from re-occuring.

    While the mast is down, I want to take the chance to freshen up the paint. The current paint is a Turkish 2-part polyurethane. I can't get the Turkish paint, of course, but I'm wondering if anyone has any good reasons to prefer one brand of 2-part poly over another brand? If not, I will probably go with the Interlux version, simply because that's what I've used before.

    Recommendations?


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    Default Re: Inspecting wooden masts

    I'd coat the end-grain butt, when complete, with several coats of epoxy before painting. Interlux 2-part is fine. For bedding compound, I'd use butyl tape is this application.
    David G
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    Default Re: Inspecting wooden masts

    Yer gonna fill that bottom with solid wood?
    Consider using a cedar or even a hardwood rather than spruce?

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    Default Re: Inspecting wooden masts

    Quote Originally Posted by wizbang 13 View Post
    Yer gonna fill that bottom with solid wood?
    Consider using a cedar or even a hardwood rather than spruce?
    Yes, will definitely have solid core. Already ordered some good quality DF. If the bottom had been cared for properly, I donít think there would be any problem.

    Wood wants to suck up water. Itís the nature of the beast.

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    Default Re: Inspecting wooden masts

    You probably know your mast etc best, so there is no need to allow drainage for any water coming through from other fastenings - If you glass the base the water will stand there and possibly cause some issues?

  20. #20
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    Default Re: Inspecting wooden masts

    Quote Originally Posted by Ensio View Post
    You probably know your mast etc best, so there is no need to allow drainage for any water coming through from other fastenings - If you glass the base the water will stand there and possibly cause some issues?
    I wont be fiberglassing the base. I think that would cause more problems than it would solve. I think sitting it on a fiberglass pad, and bedding it down well will stop it wicking up water well enough.

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    Default Re: Inspecting wooden masts

    Quite frankly, I would extend the scarf above that rotten area by several feet. This will afford a stronger splice and allow you to build in a better drain than was there before, as well as to allow you to check the interior higher up. I would build an entire new butt on that spar! Remember that you need to drain condensation as well as any other moisture that enters that stick. It is given that shellac or CPER is a must on the interior.
    Jay

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    Default Re: Inspecting wooden masts

    Quote Originally Posted by jalmberg View Post
    Okay! The project is underway.

    It turns out that the problem was caused by the mast soaking up water from the deck. Here it is with all the rot cut out.

    Interestingly, we discovered that this is the second time the mast has had to be repaired for this problem. The first repair was not done very well.

    When we re-step the mast, I'm going to bed it down good on a fiberglass pad and LOTS of bedding compound. That should stop the problem from re-occuring.

    While the mast is down, I want to take the chance to freshen up the paint. The current paint is a Turkish 2-part polyurethane. I can't get the Turkish paint, of course, but I'm wondering if anyone has any good reasons to prefer one brand of 2-part poly over another brand? If not, I will probably go with the Interlux version, simply because that's what I've used before.

    Recommendations?

    The way the paint reveals implies the heel was not sealed at all? Because that would certainly explain a great deal.

    Looks like a straightforward repair anyway, which is great news.

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    Default Re: Inspecting wooden masts

    Time was, the tradition was to put a large coin beneath the heel of a mast when it was stepped "for good luck." An old timer once told me when we pulled the stick on an old boat at the yard and found a silver dollar was that the "good luck" was that the coin raised the heel of the mast just enough to keep the endgrain of the heel from soaking up water and rotting out. I don't know if he was pulling my leg or not, but it seemed to make sense.

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    Default Re: Inspecting wooden masts

    Quote Originally Posted by Bob Cleek View Post
    Time was, the tradition was to put a large coin beneath the heel of a mast when it was stepped "for good luck." An old timer once told me when we pulled the stick on an old boat at the yard and found a silver dollar was that the "good luck" was that the coin raised the heel of the mast just enough to keep the endgrain of the heel from soaking up water and rotting out. I don't know if he was pulling my leg or not, but it seemed to make sense.
    Harking back to microbiology lectures half a century ago, silver and copper demonstrate the oligodynamic effect, very small concentrations are toxic to many microorganisms. The silver leaching from the coin may also have inhibited rot in addition to ventilating the base of the mast. I think copper might be more effective. The old US dollars were 90Ag 10Cu, so both metals were available.

    Too bad pennies are mostly zinc. Other US currency is a copper nickel alloy 25Ni 75Cu and should have a similar effect. The coins may be less expensive than the copper you would buy to put under the mast. https://www.usmint.gov/learn/coin-an...specifications Mea culpa, I did have to google this part, the silver concentration needed to kill bacteria is in the 10 to 100 parts per billion range, which is available from contact with the oxide on the surface of a coin.

  25. #25
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    Default Re: Inspecting wooden masts

    Google expertise:
    Commercially available timber inspection:
    https://inspectapedia.com/structure/...Test.php#Table

    Microwave imaging may have reached an affordable cost.
    http://terasense.com/applications/nd...od-processing/

    EDIT: While you may not want the picture, it beats another 1000 words:
    Last edited by MN Dave; 08-25-2018 at 12:09 PM.

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    Default Re: Inspecting wooden masts

    I am not sure how well CuNi alloys would work. One of the alloy's advantages is extremely high corrosion resistance, so there would be little copper available to kill micro-organisms.

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    Default Re: Inspecting wooden masts

    Quote Originally Posted by robm View Post
    I am not sure how well CuNi alloys would work. One of the alloy's advantages is extremely high corrosion resistance, so there would be little copper available to kill micro-organisms.
    CuNi does work as an antifouling. Dunno about this application though.
    It really is quite difficult to build an ugly wooden boat.

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  28. #28
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    Default Re: Inspecting wooden masts

    Quote Originally Posted by Bob Cleek View Post
    Time was, the tradition was to put a large coin beneath the heel of a mast when it was stepped "for good luck." An old timer once told me when we pulled the stick on an old boat at the yard and found a silver dollar was that the "good luck" was that the coin raised the heel of the mast just enough to keep the endgrain of the heel from soaking up water and rotting out. I don't know if he was pulling my leg or not, but it seemed to make sense.
    Yes it is true that some people place a silver coin under the heel of a mast when it is stepped. In truth, most often, a copper coin was used as silver is extremely electricaly reactive and can cause degradation of the wooden fibers of the mast. The downward thrust of the mast normally forces the coin into the end grain and has little to do with raising the mast enough for drainage. A properly built step will have a drain hole built in that will allow the water from the mast interior to drain through a hole bored in he butt. And, the corrosion of the copper coin will impregnate the wood with copper sulfate and protect it against rot forming. Sorry to have to shoot down your post Bob but, this is the truth. A very wise old boat builder from England taught me this many years ago.
    Jay
    Last edited by Jay Greer; 08-23-2018 at 09:02 PM.

  29. #29
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    Default Re: Inspecting wooden masts

    Quote Originally Posted by Jay Greer View Post
    Yes it is true that some people place a silver coin under the heel of a mast when it is stepped. In truth, most often, a copper coin was used as silver is extremely electricaly reactive and can cause degradation of the wooden fibers of the mast. The downward thrust of the mast normally forces the coin into the end grain and has little to do with raising the mast enough for drainage. A properly built step will have a drain hole built in that will allow the water from the mast interior to drain through a hole bored in he butt. And, the corrosion of the copper coin will impregnate the wood with copper sulfate and protect it against rot forming. Sorry to have to shoot down your post Bob but, this is the truth. A very wise old boat builder from England taught me this many years ago.
    Jay
    I would have to agree that the coin is likely to be embedded in the wood. Janka hardness and all. The drain hole in the butt sounds like a no-brainer, and the basis for a tasteless joke. I have to disagree on some of the chemistry though.

    Silver is extremely electrically conductive, which is a far cry from reactive. Copper is similarly conductive and somewhat more reactive. As you may recall, there are only 3 common placer or native metals, Gold, copper and silver. They occur naturally because they are so non-reactive. I would recommend a copper sheet, but the coins might be cheaper and more easily recycled. One of the few things you can bury under a mast for 50 years and sell to a collector for a profit.

    The alkaline degradation problem is caused by coupling a metal object in wet wood to a zinc anode. The problem is much smaller with an isolated piece of metal, and if the end of the mast isn't waterlogged, you won't see that problem at all. Don't use pennies, they have a zinc core and may self destruct galvanically. Just to be ornery, I will add the useless comment that the patina on copper in a marine environment tends to be basic copper chloride according to Uhlig, if I remember correctly having just read it in 1984. The sulfate patina is what you get inland. Copper.org says similar.

    This I had to google: The silver concentration needed to kill bacteria is in the 10 to 100 parts per billion range, which is available from contact with the oxide on the surface of a coin. According to laboratory tests, if U.S. coins are free from dirt and grime, E. coli, MRSA, and other bacteria will die on their surfaces in less than an hour. Paper money, not so much.

    Copper nickel alloys are all antifouling to some degree. 90-10 is the most effective anti fouling alloy. It forms a layered scale that has very low shear strength. Once the scale forms, it will foul, but the fouling attaches to the scale, which sloughs off easily.

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    Default Re: Inspecting wooden masts

    Say what you will, say what wish but, hands on, practical experience has told me that copper works better than silver when placing a coin under a mast butt for the purpose of protecting the wood from rot. The spar maker I learned about mast building from was from Portsmouth and he knew a thing or two about masts. So why take a chance? Incidentally don't put one of each under a spar as the action of the silver will eat up the copper.
    Jay

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    Default Re: Inspecting wooden masts

    Quote Originally Posted by Jay Greer View Post
    Say what you will, say what wish but, hands on, practical experience has told me that copper works better than silver when placing a coin under a mast butt for the purpose of protecting the wood from rot. The spar maker I learned about mast building from was from Portsmouth and he knew a thing or two about masts. So why take a chance? Incidentally don't put one of each under a spar as the action of the silver will eat up the copper.
    Jay
    Yes, I should have added that while silver can work, copper will work better. Unless of course I should have just let it go. Jay, the trouble with arguing with you is that you tend to be right. The only trouble with copper coins is availability. The 'gold' dollars are as close as we get these days.

  32. #32
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    Default Re: Inspecting wooden masts

    Bugger. I believe I have a gold sovereign under my mast. Useless.

  33. #33
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    Default Re: Inspecting wooden masts

    Well, if coins are not available in copper you can make your own with an arch punch and sheet copper. And you can have it machine engraved by a trophy shop, boat name plus pertinant information if you wish.
    Cheers,
    Jay

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    Default Re: Inspecting wooden masts

    I make mast fittings out of copper water pipe, as long as no strength is required. Easy and cheap and looks good.

    You could make a grid of flattened copper pipe to put under the mast.

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    Default Re: Inspecting wooden masts

    Quote Originally Posted by jalmberg View Post
    Okay! The project is underway.

    It turns out that the problem was caused by the mast soaking up water from the deck. Here it is with all the rot cut out.

    Interestingly, we discovered that this is the second time the mast has had to be repaired for this problem. The first repair was not done very well.

    When we re-step the mast, I'm going to bed it down good on a fiberglass pad and LOTS of bedding compound. That should stop the problem from re-occuring.

    While the mast is down, I want to take the chance to freshen up the paint. The current paint is a Turkish 2-part polyurethane. I can't get the Turkish paint, of course, but I'm wondering if anyone has any good reasons to prefer one brand of 2-part poly over another brand? If not, I will probably go with the Interlux version, simply because that's what I've used before.

    Recommendations?
    If the Turkish paint was any good, it was made from the same raw material as any other good PU paint. Most reputable PU paints are pretty similar. I can't say which one is best, but I can say that the Turkish paint couldn't be all that different from something like Interlux.

    A paint manufacturer once told me that there are maybe 4 chemical plants in the world that produce polyurethane resin. The base material is expensive, every paint manufacturer uses essentially the same stuff and that because the raw material is expensive, cheap PU paint is mostly some other filler. So if it's cheap, avoid it.

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