Boomkin strength and my mistake

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  • July 26, 2013 10:25 AM
    Message # 1352408
    Deleted user
    So I made my boomkin out of clear vertical grain Doug Fir but came sort on the thickness.

    My original boomkin was 2.25" thick and my new one is 2" thick and now I wonder if there is a way to add the strength needed to this new piece of wood? Or do you think its going to be safe being only a half inch shy. 

    I considered laminating a quarter inch to it or glassing over but id like to keep the wood look and ask for your thoughts. 
    Last modified: July 26, 2013 2:49 PM | Deleted user
  • July 26, 2013 2:59 PM
    Reply # 1352613 on 1352408
    Deleted user
    A couple of thoughts.

    Mine were about 2.125" thk when I had them (no issues other than rot) You could be just fine? the biggest issues are rot, splits and cracks in the wood.

    You are in a great position to try glass work (1/8" thk on the bottom of the timbers)

    remember 1/8" of glass is allot but this should be really easy just strips (layers) on a pc of plastic (or peelply)  and some epoxy then lay the board on top of it and comback the next day to sand smooth the edges. (assumed you worked the epoxy into each layer)  = this will be on the bottom where no one will look

    For a good finish you could wrap the whole thing with, like 4oz. or less glass,  a thin layer of (wet) glass is transparent and can, or must be varnished or painted to protect it from the UV. Just don't let it go, as the epoxy will yellow if you do. Try it on a extra block of wood if you want to see the results (sand the glass smooth and then throw a coat of your varnish on top of it should look just like 3 coats of varnish and you should not be able to see the glass at all) oh  west 207 would be the best for this type of work.

    You would wind up at 2.15" thk and stronger than the 2.5" wood alone.

    oh while you are at it,  if you over drill all the holes and then fill them with the epoxy then redrill to the correct size;  you will have a timber that will not rot or warp if it was dry when you did the glassing. You will then only need to check the chain plates down on the hull.

    Best of luck, either way should be fine I just hate wood by itself as it has issues.  
    Last modified: July 26, 2013 3:08 PM | Deleted user
  • July 28, 2013 5:35 PM
    Reply # 1353381 on 1352408
    Deleted user
    In my humble opinion, when dealing with a natural fiber material such as Fir, 1/4" isn't going to make much of a measurable difference in strength. Ideally, the boomkin should only be in compression load: back-stay tension equals whisker stay tension, therefore resulting load on the boomkin is directly inward along it's long axis. Your 2" boomkins should be just fine.
  • July 29, 2013 5:30 AM
    Reply # 1353570 on 1353381

    I am certainly no engineer but I would have to agree with Thomas.

    If the stress was anything but a compression load or if it were more than a 1/4" mistake I would maybe be concerned.
  • July 29, 2013 12:05 PM
    Reply # 1353873 on 1352408
    Deleted user
    OK you guys got me (the wood strength is fine) 

    My long comment above was (wood = rot, splits, termite food)  I love it, but hate it, you see it looks nice, but you need to keep varnishing it, and checking on it, for; rot,splits and those little guys.

    The glassing would stop the rot, splits and the little guys. BUT YOU DO NOT HAVE TO DO IT. 

    I have removed my boomkin altogether, as it is not needed at all!  (twin back stays to the hull; I lost a few inches of boom and the foot of the sail is only 14'-0" )  The boat sails better with this mod and I would recommend it, as I have not need to even check on that thing call a boomkin and I don't have as much weather helm as I use to.

    The Guys above are correct, the wood is only in compression (which it is good, if it is along the grain which is "the way you have it")  1" should be more than enough for these loads.

    but if you stand on it in the middle = bending + compression you may want at least 1.5" thk.  if you weigh 300# or less
    and if you have your wind vane operating and you are standing on it you may want 1.8" thk
    and if you have a wind vane, standing and gibe you may want 2"  thk.
    but if you have a wind vane on , are standing on it, gibe and pitchpole all at the same time; well you are just having to much fun, the 2" thk still should be ok, but the back stay or the staps may fail.

    Smile  It is all good. and if you protect your wood, it is even better.
    Norm

    Oh I think Jay had a picture of a split issue on his boat some time back (I think he put a picture in "things that fail" album +/-

    Last modified: July 29, 2013 2:42 PM | Deleted user
  • July 29, 2013 5:12 PM
    Reply # 1354108 on 1352408
    Deleted user
    Thomas got it right , 2" is fine , but do like Thomas says compress don't pull . And while your at it would you mind changing your avatar pic ? It's kind of creeping me out . Thanks.
  • July 30, 2013 5:36 AM
    Reply # 1354484 on 1352408

    I glassed my boomkin planks.  Tis not that hard and the finished product is a fine, strong, and protected piece of wood...  wait, what was I talking about again :)

    Regardless, I laminated my planks.  The new age or non-old-growth wood in my opinion needs some type of support for security and protection.  Glass is cheap and easy to work with... cheaper than a mast lost at sea.

    If anybody wants more information regarding how I made my boomkin planks, I can follow up... else I like the way Norm explains it :)

    T.

  • July 30, 2013 7:14 PM
    Reply # 1355075 on 1352408
    Anonymous member (Administrator)

     

    Here is the picasa album of images when the toggle broke and took out the boomkins' -- but not the mast!!.  If you have these toggle on your boat -- please change ASAP.

    Jay

    Last modified: July 30, 2013 7:15 PM | Anonymous member (Administrator)
  • July 31, 2013 7:05 AM
    Reply # 1355385 on 1352408
    The best kind of wood is stainless steel.
  • August 03, 2013 10:52 PM
    Reply # 1357971 on 1352408
    Deleted user

    Bud,

    I agree that stainless steel wood is maintenance free, except for some polishing like your silverware. But there is also another advantage, it allows for other possibilities: Mooring cleats, a plate to mount your self steering to, an anchor roller to slow a boat down in a storm. But now I am thinking of adding a base with braces for a short SS mast that holds a wind generator and or solar panels outside the mainsheet which is attached like on the "real wood" boomkin to the blocks. - I had the bow sprit and boomkin built in 1975 and there is still no rot on the SS-316 wood. Wow! It is better than the aluminum tube bow sprits that the Islander 41 (or 43 ?) have; although 50 series aluminum machines like a dream!

    Btw., I looked at Jay Bietz's post and he has an interesting stainless steel boomkin. Since W32s are double enders, there is no good place to attach a swim ladder, this has a nice solution. I prefer myself to make the boomkin wider and leave off the railing. Anchoring stern to is not that common in North America, but in Europe. If I ever get there, I am well prepared, with a wide boomkin. I also have a double backstay with insulators for a single side band that got stolen in Hawaii, and I needed the width for the spread. The boomkin on Polaris is attached with brackets that are inside the bulwark riser, not below  and further aft.  The same with the bowsprit. Both the 'sprit and boomkin are through bolted, so that if the stays break, they still hang onto the through bolts in the deck.

    Do I see a platform on the side of Jay's boomkin? It is not clear from the photos, but it appears that there is something to step on when coming up on the ladder.

    Another item: Do you use a stelf steering on long passages? Electric or mechanical? If so, what do you use? This may be the subject for another topic.

    Keep on sailing!

    Mike

    Last modified: August 03, 2013 11:32 PM | Deleted user
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