[Public-List] Mast beam almost finished!

[Mike Lehman]

I believe that one of the problems with the original bolts was that Whitby 
drilled VERY deep countersinks for the nuts on the bottom of the beam. The 
ones I have seen were drilled about 1/2 way thru the beam and the holes are 
on the worst possible location where the main downward force is applied. The 
main contributing factor to beam failure was the glue failed.


~~~_/)_/)~~ Mike Lehman ~~_/)~~~


-----Original Message----- 
From: Jeffrey
Sent: Saturday, October 26, 2013 8:11 AM
To: Alberg 30 Public List -- open to all
Subject: Re: [Public-List] Mast beam almost finished!

Thanks Glen.

You are probably right about using the through bolts.  I'm still
trying to get my head around the forces on the last plate. Obviously
down. But then I'm sure there's some pushing to the side, depending on
the tack.  What I'm thinking is that the bolts holding down the mast
plate only need to resist force in sheer, so that depth wouldn't
matter after a certain point.  Shorter lag bolts that are thicker
might be stronger than thinner through - bolts?


jeff

Jeffrey Fongemie

Seagrass
Alberg 30 #116
Boothbay Harbor Maine






On Sat, Oct 26, 2013 at 2:19 AM, Glenn <brooks.glenn at comcast.net> wrote:
> Hi Jeff,  i had the same concern when I replaced my beam.  Eventually I 
> drilled the bolt holes and thru bolted.  My reasoning is that all the 
> boats have these bolts with no failures in 45 years so it is a proven 
> method.   Also I didnt think I would gain anything by using lag bolts. 
> They wont give you the structural integrity of thru bolts and will likely 
> pull out if the mast ever did go over.  At worst lag bolts have a high 
> risk for  creating pockets for water penetration and early dry rot.
>
> On that cheerful note....
>
> Glenn
> dolce 318
>
> Sent from my iPad
>
> On Oct 26, 2013, at 12:13 AM, Dominic Amann <dominic.amann at gmail.com> 
> wrote:
>
>> I suspect that bolting through will not introduce much more weakness than
>> drilled in lag bolts. Bear in mind that the failure you were observing 
>> was
>> a delamination of the beam, and I think through bolts would actually help
>> prevent that.
>>
>>
>> On Fri, Oct 25, 2013 at 4:10 PM, George Dinwiddie
>> <gdinwiddie at alberg30.org>wrote:
>>
>>> Jeff,
>>>
>>> On 10/24/13 7:17 AM, Jeffrey wrote:
>>>
>>>> Hi everyone,
>>>>
>>>> I'm nearly done replacing my mast beam. I've got the beam in, the
>>>> tabbing finished and the posts reinforced.
>>>>
>>>> http://216.172.166.167/~**seagrass/ <http://216.172.166.167/~seagrass/>
>>>>
>>>
>>> Nice work, and a very nice description.
>>>
>>> I still need to decide on how to deal with the bolts, that on the
>>>> original beam, went through the mast step and right through the beam.
>>>> I don't think bolts going all the way through the beam are necessary
>>>> and will weaken the beam. I'm thinking of using some lag bolts that
>>>> will go an inch or so into the beam.
>>>>
>>>
>>> - George
>>>
>>> --
>>> ------------------------------**------------------------------**
>>> ----------
>>>  When I remember bygone days                         George Dinwiddie
>>>  I think how evening follows morn;            gdinwiddie at alberg30.org
>>>  So many I loved were not yet dead,           http://www.Alberg30.org
>>>  So many I love were not yet born.                          also see:
>>>               'The Middle' by Ogden Nash     http://idiacomputing.com
>>> ------------------------------**------------------------------**
>>> ----------
>>>
>>>
>>>
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>>
>>
>>
>> --
>>
>>
>> Dominic Amann
>> M 416-270-4587
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-- 
______________

Jeffrey Fongemie
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