Best practice for worn out rigging question? ( S.S. vs Alm.) I have older sailboats and at some point or another upgrades to the spars need to be done. The booms seem to need more help and there is some contention over using SS rivets and screws that hold rigging hardware into thin aluminum spars. I have used both types of rivets and everything seems to be fine other then I need a bigger rivet gun for the SS rivets. I now have a boom on my Catalina C22 that needs attention and my question is should factory SS screws be replaced with aluminum rivets now that longer rivets are available for most applications to reduce the corrosion problems? The thing I like about the rivets is they have a large surface area to cover elongated holes but are they as strong as the screw option? Any feed back would be greatly appreciated.
Elongated holes in spars questions
- Thread starter DJM
- Start date
I'm in the same camp as you are. After stripping down mast and boom of a C-22 of numerous corroded SS screws that were incorrectly installed without proper bedding/tef-gel plus years of neglect everything will have to be re-fastened properly. Some holes will have to be drilled out slightly larger. Without getting into a crazy analysis of the actual sheer strength of aluminum rivets vs SS screws I think I can be fairly confident AL rivets will be more that sufficient in certain low-load cheek blocks and other hardware. the corrosion potential will be dramatically reduced and it is way easier to drill them out and replace as needed. I use a pneumatic rivet gun that cinches down rivets at 90 psi, gives a very solid action and all you have to do is ensure you hold the gun square to the work. The gun has multiple tips for six sizes of rivet shafts. There will still be some SS screws on certain things, but you have to remember that in the thin aluminum of small boat spars only a very few threads are actually gripping the aluminum.
Thanks for the reply, I will have to look into a bedding compound, I did not know there was a product like that on the market and I have not even started on the mast yet. The area that most concerns me is where my boom attaches to the cap on the end of the boom that has the goose neck and clew. There is 3/16 of aluminum to screw into which gives the S.S. self tapping screws something to bite into but it would be the same problem years later which would be to move up to the next size screw. I was just wondering if anyone tried another approach by maybe tapping the aluminum and using a machine type screw or even the rivets? Good idea about pneumatic rivet gun, I'm going to get word to Mrs. Clause to get the elves working on one.
I have used alum rivnuts in similar installations They have worked well so far. You can size the damaged hole for the alum rivnut, install it, then install a SS screw with protective coating.
http://rivetsonline.com/39213-aluminum-threaded-insert-kit.html
http://rivetsonline.com/39213-aluminum-threaded-insert-kit.html
FYI, my Pneumatic Rivet Gun came from Harbor Freight and was only about $40. Not everything from HF is total garbage. I wouldn't necessarily use it on a real 'job site' where I have to send home hundreds of rivets a day, but for home use only a few rivets at a time its great.
For bedding compound on spars you can use numerous adhesive sealants, they just don't need to be high strength because all they are there for is electro isolation. Any bedding compound you would use on deck fittings would work, even butyl tape. If you use 3M 4200 or similar just get the UV resistant type. You'd only need bedding compound on the back face of things like cheek blocks or the stainless mast spreaders that sit flush against the mast face on the C-22. There is also Delrin Dielectric Self Adhesive Insulator, like a sticker basically... less messy.
http://www.catalinadirect.com/index.cfm/product/3217/delrin-dielectric-self-adhesive-insulator.cfm
Overall, for threads on SS Screws you should use Tef Gel. Even Blue Loc-Tite provides some isolation and is mostly water-proof when dry but I don't have any real world data to back that up. The Tef Gel is pretty much industry standard for preventing galv corrosion between dissimilar metals, also acting as a good lube for the threads to prevent galling. If you are inspecting your spars every season you'll probably find you only need to remove the screws and apply fresh Tef-gel about every 5 years (depending on how much you sail and where you boat sits). I know a skipper who does everything on average every 2 years, he races weekly...
I like the idea of the Rivnuts shown above, but I would only recommend them in holes that are badly damaged or elongated. For the most part I have broken #8 to #12 SS screws in my spars. I was able to remove almost all them without them braking off at the surface, only a few need to be drilled out. Almost all the hardware on my spars will have relatively low load/sheer forces. I will use MOSTLY aluminum rivets on everything.
- The Gooseneck and Boom end Cap will get rivets, the forces on the fittings push inward, not pulling outward.
- Even the Masthead will have AL Rivets, the forces of the shrouds pull downward against the shoulder flange of the Masthead onto the spar, not on the fasteners. Also, there is still the 5/16 SS Bolt that passes through the upper shroud tangs and Masthead. That will get Tef-gel, liberally on the bolt shaft, threads, and under side of bolt head, anywhere it could touch aluminum.
- For all 'cast aluminum' parts (Masthead, Gooseneck, Gooseneck Slide, Boom End Cap, etc); I will paint them all with a self etching aluminum primer (Rustoleum is fine, nothing fancy required) and top coat with a white enamel. This will add some additional anti-corrosion properties and look pretty too.
- I'm using lines led aft so this actually eliminates a good deal of hardware off my mast. the halyard winch is removed and the most of the cleats are no longer needed. I will keep a few key items for safety/redundancy and there will be some fairleads added eventually, but any 'left over' holes will be filled with an AL Rivet and a dab of 4200 to close the rivet's center hole.
I won't be rigging until the Spring I think. I'm in Grad School now, dirt poor, and have little time to work on my C-22 resto. I hope to have the decks painted by the end of this month and then I can finally get to the finishing work of installing hardware. When I do get to rigging I should have some pretty good additions to my thread (pictures) that will show all of this.
BTW... I have 3 masts for my C-22, LOL! Picked up 2 bone-yard masts, the OLD oval style. I thought they were 'weaker' than the heavier flat sided newer style mast that came with the boat, but the Racers tell me that the oval mast are highly sought after because they are easier to bend for sail trim and not really that weak vs the heavier spar section (unless maybe a big storm, but rare).
For bedding compound on spars you can use numerous adhesive sealants, they just don't need to be high strength because all they are there for is electro isolation. Any bedding compound you would use on deck fittings would work, even butyl tape. If you use 3M 4200 or similar just get the UV resistant type. You'd only need bedding compound on the back face of things like cheek blocks or the stainless mast spreaders that sit flush against the mast face on the C-22. There is also Delrin Dielectric Self Adhesive Insulator, like a sticker basically... less messy.
http://www.catalinadirect.com/index.cfm/product/3217/delrin-dielectric-self-adhesive-insulator.cfm
Overall, for threads on SS Screws you should use Tef Gel. Even Blue Loc-Tite provides some isolation and is mostly water-proof when dry but I don't have any real world data to back that up. The Tef Gel is pretty much industry standard for preventing galv corrosion between dissimilar metals, also acting as a good lube for the threads to prevent galling. If you are inspecting your spars every season you'll probably find you only need to remove the screws and apply fresh Tef-gel about every 5 years (depending on how much you sail and where you boat sits). I know a skipper who does everything on average every 2 years, he races weekly...
I like the idea of the Rivnuts shown above, but I would only recommend them in holes that are badly damaged or elongated. For the most part I have broken #8 to #12 SS screws in my spars. I was able to remove almost all them without them braking off at the surface, only a few need to be drilled out. Almost all the hardware on my spars will have relatively low load/sheer forces. I will use MOSTLY aluminum rivets on everything.
- The Gooseneck and Boom end Cap will get rivets, the forces on the fittings push inward, not pulling outward.
- Even the Masthead will have AL Rivets, the forces of the shrouds pull downward against the shoulder flange of the Masthead onto the spar, not on the fasteners. Also, there is still the 5/16 SS Bolt that passes through the upper shroud tangs and Masthead. That will get Tef-gel, liberally on the bolt shaft, threads, and under side of bolt head, anywhere it could touch aluminum.
- For all 'cast aluminum' parts (Masthead, Gooseneck, Gooseneck Slide, Boom End Cap, etc); I will paint them all with a self etching aluminum primer (Rustoleum is fine, nothing fancy required) and top coat with a white enamel. This will add some additional anti-corrosion properties and look pretty too.
- I'm using lines led aft so this actually eliminates a good deal of hardware off my mast. the halyard winch is removed and the most of the cleats are no longer needed. I will keep a few key items for safety/redundancy and there will be some fairleads added eventually, but any 'left over' holes will be filled with an AL Rivet and a dab of 4200 to close the rivet's center hole.
I won't be rigging until the Spring I think. I'm in Grad School now, dirt poor, and have little time to work on my C-22 resto. I hope to have the decks painted by the end of this month and then I can finally get to the finishing work of installing hardware. When I do get to rigging I should have some pretty good additions to my thread (pictures) that will show all of this.
BTW... I have 3 masts for my C-22, LOL! Picked up 2 bone-yard masts, the OLD oval style. I thought they were 'weaker' than the heavier flat sided newer style mast that came with the boat, but the Racers tell me that the oval mast are highly sought after because they are easier to bend for sail trim and not really that weak vs the heavier spar section (unless maybe a big storm, but rare).
Thanks again for the help, the bolt sounds like my best option then I can take it apart and inspect it with the rest of the rigging as needed. I will take down everything on the mast and boom that's bolted and pinned together then reset everything with Tef-Gel for peace of mind.