mast splicing

[mikestevens]

Brian,
Thanks for sticking with this thread. I give a lot of credibility to what you have been saying. In your first post you suggested flat head fasterners. I want to confirm that you are then countersinking. And that seems to leave you with enough meat to tap?

Also, Das Haus, I know your boat. Colombia Defender right. I think I saw your boat up in Block on my way down to VA and then I saw you again in Norfolk. Could that be? The current name on my boat is RIP Curl, but that is changing.

[Brian Duff]

Yes, flat head machine screw fasteners. Only the mast wall gets a countersunk and clearance hole, the splice plate receives the tapped hole . IF the head of the #10 is too thick, use # 8's (or a diffenet angle or undercut screw head, or any of so many options...)
I do not know what mast you have, but guessed at its wall based on the dimensions you gave. It is important to obtain the 'drawing in' of the splice plates to the mast wall. This is another reason that the splice pieces shouldn't be one piece. When splicing something like a 'pipe' mast where it is easy to obtain an extrusion that fits well inside, we split it lengthwise so the fasteners can draw the plates tight to the mast wall. I usually use three complete rows of fasteners each side of the splice, then two more rows with half as many fasteners.
Russ L is right in that the idea is to avoid stress risers. We also (sometimes, depending on the budget of the client) thin the plates toward the ends, as as antoher way to taper the material away. Most spar builder splices I have worked with have not done either type of tapering. some of the builders of spars use just three rows of fasteners each side, with a rather closer fastener spacing. Some have way more fastneners...

call your spar builder and have a chat with them about your plans, thats what we do.

heat works to loosen corroded stuck fasteners on all masts- anodized, powdercoated, awlgrip, or bare, you just gotta be careful ! Impact tools also are very effective at removing stuck fasteners. PB Blaster can help too. If a splice with mechanical fasters was corroded enough to "fall" apart, that should be clearly visable to even an untrained eye. Use some 'goop' to help slow the corrosion of fasteners in aluminium.


Self tapping screws are only to be used on wood. Do NOT use self tappers on aluminum or fiberglass, as it is WRONG. Self tappers are weak becasue they have both a smaller root diameter and must have less thread grip as well (in such hard materials) becasue the threads cannot compress the material away like in wood. It seems to me that self tapper screws in fiberglass are alway leaking, and the surely delaminate the fiberglass where they go through. thats for another thread though, if someone wants to start one....

[mikestevens]

Thanks for the reply brian.
If the splice is 12" long, plus the 3" tapers, than that gives me 6" on each side, not counting the tapers. If I make the first row 1" from the edge of the splice, then that leaves me with 5" until I get to the taper. if I follow your spec of 8X the thickness of the screw or about 2" apart It seems I would have room for only for 3 rows on each side of the splice.

Now for a new question. I have stripped the mast and was wondering how to do a dye penetration test to the standing rod rigging. Easy? Hard?
Mike.

Also, for managers of tghe site; is ther a way to post images?

[Russ L]

Hi Mike,
Your source for the dye penetrant kit is likely going to be an auto parts supply that has engine rebuilders as customers.
The kit will have a cleaner, penetrant & developer. Follow the directions on the cans... easy!
Brion recommends a small microscope to check for cracks.

To post images: you include a link in your messages to images that are stored elsewhere on the net. No provisions to send images to the Spartalk server.

Cheers, Russ

Originally Posted by mikestevens

Thanks for the reply brian.
Now for a new question. I have stripped the mast and was wondering how to do a dye penetration test to the standing rod rigging. Easy? Hard?
Mike.

Also, for managers of tghe site; is ther a way to post images?

[Wannafish]

Originally Posted by mikestevens

Now for a new question. I have stripped the mast and was wondering how to do a dye penetration test to the standing rod rigging. Easy? Hard?
Mike.

Mike,

You might also want to do a web search for a dye penetrant called "Zyglow". After it dries you shine a blacklight on it and the die in the crack shows up really well.

Rick