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Old 11-11-2011, 10:09   #16
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Re: Major Mast Step Repair - Advice Please

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What about placing a truss underneath the mast that would attach to the bulkhead on each side. This would serve to transfer the mast load from the deck to the bulkheads. I have seen this done on smaller deck stepped boats where the mast support had failed after ten years or so.
I think that's kind of what my stainless triangulated bracket is going to be..... although I think it only needs it on the r/h side as that is where the loading is..... the compression was only on the right as the bulkhead had held the roof up on the left.
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Old 11-11-2011, 10:12   #17
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Re: Major Mast Step Repair - Advice Please

That stainless bracket may then put lateral force on the bulkhead causing it to deform in...I think Charlies idea would spread that load over a larger area.
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Old 11-11-2011, 10:14   #18
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Re: Major Mast Step Repair - Advice Please

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Originally Posted by gixerjen View Post
I think that's kind of what my stainless triangulated bracket is going to be..... although I think it only needs it on the r/h side as that is where the loading is..... the compression was only on the right as the bulkhead had held the roof up on the left.
So you're going to put the load on the new brackets? I think this is a bad idea.

I'd get the bulkhead perfectly lined up and then if it is crushed some on the top put a metal shim in at the top of it between the cabin top and the bulkhead. I'd bolt the brackets to hold the bulkhead and shim perfectly in place under the mast but let the weight of the mast take the weight straight downwards on the bulkhead and shim.

In the deck, I'll second what was said about using an aluminum plate as the new mast pad.
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Old 11-11-2011, 10:15   #19
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Re: Major Mast Step Repair - Advice Please

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That stainless bracket may then put lateral force on the bulkhead causing it to deform in...I think Charlies idea would spread that load over a larger area.
Don't quite get the difference..... (sorry, blonde moment)
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Old 11-11-2011, 10:16   #20
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Re: Major Mast Step Repair - Advice Please

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That stainless bracket may then put lateral force on the bulkhead causing it to deform in...I think Charlies idea would spread that load over a larger area.
+1

James has it right.


As a side note, Charlie, can you elaborate on building a full truss in such a confined space? Would not a piece of flat bar work or is a full truss called for?
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Old 11-11-2011, 10:18   #21
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Re: Major Mast Step Repair - Advice Please

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So you're going to put the load on the new brackets? I think this is a bad idea.

I'd get the bulkhead perfectly lined up and then if it is crushed some on the top put a metal shim in at the top of it between the cabin top and the bulkhead. I'd bolt the brackets to hold the bulkhead and shim perfectly in place under the mast but let the weight of the mast take the weight straight downwards on the bulkhead and shim.
I don't think I can do that as the bulkhead is off centre relative to the mast.
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Old 11-11-2011, 10:20   #22
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Re: Major Mast Step Repair - Advice Please

This is probably a more accurate sketch......

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Old 11-11-2011, 10:22   #23
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Re: Major Mast Step Repair - Advice Please

Plywood will compress. I don't think there is much you can do to prevent that other than drill a number of holes in it and fill those holes with an epoxy/filler mixture. Also, all holes for bolts through the plywood must have an epoxy/filler annulus. Someone mentioned an aluminum plate rather than the plywood and I agree it would be a good replacement. Also aluminum angle on the inside would be okay, through bolted to the mast compression plate (the one on deck) and to the bulkhead, with good size washers or plates on the other side of the bulkhead under the head of the bolts.
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Old 11-11-2011, 10:24   #24
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Re: Major Mast Step Repair - Advice Please

It appears to me from the pics that the bulkhead supports the mast, but is offset a few inches. The stainless bracket should help alot if it is big enough so that it distributes the load well. Make sure it has some length in the vertical dimension on the bulkhead, the more the better. If the bulkhead is not real thick and sturdy, make a solid wood piece to go between the bracket and the bulkhead... bigger than the bracket. Or make the plate that attaches to the bulkhead real big. If there is room, a compression post (attached to the bulkhead?) extending under the mast would be the ultimate solution. You're an engineer, just think it through!

Later: I just saw your sketch. You've got it! Just make the plate that bolts to that thick bulkhead big/wide to distribute the load. Wow, 1 3/8 is a thick bulkhead! SS will look a lot better than aluminum, unless you do a good alum paint job.
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Old 11-11-2011, 10:25   #25
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Re: Major Mast Step Repair - Advice Please

Hmm, thinking about it, I would be reluctant to use ally. Unless I could hundred percent remove all condensation between the 2 skins, ally would corrode.... Anyone used nylon? Wouldn't compress, wouldn't corrode, really easy to machine / drill etc??
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Old 11-11-2011, 10:25   #26
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Re: Major Mast Step Repair - Advice Please

Much better sketch Jen. I had a different idea of what was going on.
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Old 11-11-2011, 10:28   #27
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Re: Major Mast Step Repair - Advice Please

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This is probably a more accurate sketch......

Very crudely put....extend and support from bending i.e. truss....the vertical plate of your bracket...the further down the face of the bulk head the greater its surface area and the more resistant or rather able to disperse the torque
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Old 11-11-2011, 10:33   #28
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Re: Major Mast Step Repair - Advice Please

Also, Jen, do you do all of your artwork on the back of paper plates? ;P
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Old 11-11-2011, 10:33   #29
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Re: Major Mast Step Repair - Advice Please

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Very crudely put....extend and support from bending i.e. truss....the vertical plate of your bracket...the further down the face of the bulk head the greater its surface area and the more resistant or rather able to disperse the torque
Forgive me for sounding dumb (it comes so easily to me though ) does that mean you approve of the bracket - that it is essentially what you mean by truss?

Also, the first sketch is one off the internet that should represent pretty much what my pencil sketch does..... his surveyor signed his work off??
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Old 11-11-2011, 10:34   #30
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Re: Major Mast Step Repair - Advice Please

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Also, Jen, do you do all of your artwork on the back of paper plates? ;P
Hell yeah!

Nah.... left my notepad at home and the previous owner left them on the boat...... it's recycling don'tcha know?!
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