[Public-List] Mast Beam Repair

[Gordon Laco]

Hello friends -

Here is my 2 cents worth... white oak is nearly as bad for gluing as  
red... the main reason white oak is a good boat building wood is its  
rot resistance due to closed phylums.  It will not draw moisture the  
way red oak with its very open cell structure will.   Unfortunately  
white oak has the same acidic qualities that red has and it is this  
that will make glue releases over time more likely.

If you are making a beam with laminations - and they can be much  
stronger and more decay resistant than solid timbers - I would suggest  
use of ash.   Ash normally is not rates so high as white oak for rot  
resistance but it has no acid issues and glues up very well.  If the  
piece being fabricated is made up of laminations glued with epoxy, and  
the whole thing is saturated with more epoxy before varnishing, the  
glue joints should hold with no release issues as one would expect  
with red or white oak.

Cheers - Gord




On 7-Jan-10, at 11:48 AM, crufone at comcast.net wrote:

>
>
>
> Hi John and Bill,
>
> Red Oak makes great fire wood, but White Oak would be a better  
> choice for boatbuilding. Thanks for your input.  I only want to do  
> this once so I must get it right the first time. I am having a bit  
> of trouble visualizing the 'slots' which Bill is talking about in  
> the tabbing application.
>
> I assume if I were to cut shallow 1/16"slots into the face of the  
> laminates and then fit square keys into the slots as I do the layup  
> this would take up most of the sheer forces? One could also install  
> 304 SS screws from the top downward into the laminates? This would  
> function as both a keying device against sheer slippage and keep the  
> package of laminates under compression? This system would be  
> undetectable from the exterior of the beam, whereas the square keys  
> would be seen on outer face of the beam.
>
> I have also considered laminating using vertical laminates instead  
> of horizontal.  I could also make a new beam out of solid white oak  
> or some better wood....one piece with no laminations. Both of these  
> last two solutions would be basically re-engineering the beam....  
> where I would rather rely on the original engineering provided by  
> Whitby.
>
> I do appreciate your continued commentary, thanks
>
> Michael #133
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