To screw...or rivet?

[Mookie B]

Hello, all. I'm leading the main halyard aft to a clutch via a turning block and a deck organizer. I also hope to do the same for my single reefing line. My question--is it better to use steel pop rivets or threaded screws to secure blocks to the mast and boom? Thanks in advance for the help!

 

[Rob19574]

I used pop rivets in my boom and mast where appropriate (ie they have the holding strength). If you have halyards, reef lines or other control lines running inside the spar, you will not need to worry about any chafe and such if you had shard screw threads coming thru. So for my exit plates and light control blocks for the reef lines, I used pop rivets. They are quick and easy to put on as well if you have the right tools.

 

[Ed Schenck]

I would say neither. There is just too much force with the direct right angle pull of the halyard. You could bolt through a large bail that spanned the mast. Or you could add one of those mast collars, check Rig-Rite for examples. My boat has a mast partner that bolts through. I remove bolts and replace with eye bolts to achieve the same thing.

P.S. an example: http://garhauermarine.com/catalog_process.cfm?cid=68
http://garhauermarine.com/ProductSpecs.cfm?pid=556

 

[woodster]

what ever you use make sure that you use stainles steel....the fasteners on my mast are pop rivits where there is no structual advantage needed and drilled and tapped where there is structual advantage required....hope this helps...

regards

woody

 

[David in Sandusky]

Cheek Blocks

We turn our main halyard and outhaul at cheek blocks screwed directly into the mast. This set-up has worked fine for us for 8 years now. A cheek block has a piece of wood shaped to the mast as a pad or cheek to hold the stainless turning block.

You can see our set-up under h27 mods on this site:

http://hunter.sailboatowners.com/in...7&cat_id=16&aid=7355&page=article&mn=27_75-84

 

[Roger Long]

Don't use sheet metal screws. Drill and tap for machine screw. It's very easy. You can get round head screws with a hex socket head that won't chafe lines. If you are putting something on close enough to the end that you can reach inside, you can back up the screws with washers and nuts if the load are high.

If you haven't tapped before, turn a little, back out until the chips come out the grooves, turn in a little more. Us a light touch at first and it will go very quickly. Cheaper than buying a pop riveter and stronger. Use a little oil on the tap.

Don't forget the TefGel.

 

[RichH]

Best is SS machine screws through the boom section and terminating into 'nuts', etc. on the inside of the boom. For drilling and tapping, use FINE threads in thin wall aluminum mast.

Next best would be MONEL pop-rivets (selected correctly for cross section vs. 'shear').
Aluminum pop rivets would be OK but would need to be MUCH larger than monel to handle the max. shear loads.
Blind aluminum expanding 'hammer rivets' or "Kep-Nuts" could be used instead of 'pop-rivets' as they are 'stronger' than Alum pop-rivets - example: http://www.fastenersuperstore.com/rivets/Drive-Pin-Rivets (must have SS 'plunger')

 

[Bob S]

How do you guys feel about installing stainless Helicoils in the mast. At least they would be stainless to match the stainless screws? They come in either free running or locking type. I drilled and tapped for locking Helicoils when I did my anchor light last year. I wet installed them using a zinc chromate primer. Not sure how easy it will be to remove them 10 years from now?

 

[Maine Sail]

How do you guys feel about installing stainless Helicoils in the mast. At least they would be stainless to match the stainless screws? They come in either free running or locking type. I drilled and tapped for locking Helicoils when I did my anchor light last year. I wet installed them using a zinc chromate primer. Not sure how easy it will be to remove them 10 years from now?

I know Brion Toss does not like them.. Toss generally uses stainless rivets in high load areas or fine threaded machine screws if the wall thickness is there. He generally prefers aluminum rivets in low loaded areas and Riv-Nut's he'll use too.

This mast base turning block is now 32 years old with well over 70k nm under the keel, heck the PO's did nearly 50k during a five years cruise, they are installed with rivets, but not aluminum. Toss also recommends using Tef-Gel to isolate the stainless rivet & aluminum spar. Monel rivets work too and tend to be easier to drill out.

 

[Mookie B]

I appreciate all of the replies! I had installed the blocks last week using ss machine screws and a tap, but will now go back and use Tef Gel per your recommendations. It seems solid but I was having second thoughts--just wanted to make sure I was at least close to a decent solution. I'll back the screws inside the mast next time the stick is off just to be on the safe side. Thanks again for the help!