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attaching harken block to cs 17 aluminum mast


tfrei

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I'm switching my masts to accommodate the new b and b sailtrack.  I'll also  need to install a halyard block at the top of the mast (a harken 243) .  The plans call for "10 32 PH MS for bottom holes" and "1" 10 PH screws for top holes" 

 

1) I imagine that  the 10 32 pan head machine screws are to be tapped into the aluminum mast with a tap and die set.  And if so, should the screws be coated with anything to help prevent corrosion and becoming loose?

 

2) I guess I don't know what screws they are talking about for the top holes.  One inch size 10 pan head machine screws ? What thread count? Or are they wood screws, and is there a wood plug behind the aluminum?

 

3) I assume the screws are all stainless steel. Right?

 

4) And while I'm at it, since the attachment is at the top where the inside can be accessed, why not put a nut and washer on the inside of the screws with some thread lock?

 

Note: I didn't build this boat, so I don't know some of the construction details.

 

Thanks for the help. 

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I did SS machine screws on my P28. As you said - nut on the inside should work better than anything. Whole lot quicker too. I used Teffgell (sp?) because that is the recomended stuff to keep aluminum and SS happy together but I have no idea how well it is going to last. If the plan calls for screws on top -do it. Graham ALWAYS has a reason. In this case I suspect he simply wanted to save some work because with nuts and bolts on top you would have to cut dadoes in the plug to get it inside the mast over them. In other words not a strength issue rather KISS issue. Good luck PeterP

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There are 4 holes on the Harken halyard block flanges for fastening to the mast. I use 2 - 1/2" x 3/16" ( # 10) bolts for the lower holes. There is a plug in the top of the mast. I put in the plug with caulk after I install the lower bolts.   I use 2 - 3/4" #10 ph screws into the plug. Everything is caulked to prevent leaks and isolate the stainless from the aluminum.

 

We supply plastic caps or you can make a wood plug.

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