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Can someone make a logical case for only using stainless or silicon bronze screws. In the type of building most of us do I just can not see what the issue could be. The boat is totally encapsulated and usually the screws deep inside the structure. It looks like if there is enough moisture to eat up the fastener then the wood would be rotted out also.

Any screws that are exposed is a no brainer. Someone help me understand and make sense out of this, because I have never been able to grasp any reasoning.

 

Scott 

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If you can guarantee that there will never be even the slightest break in the epoxy barrier then you might have a point. But I certainly wouldn't count on it. I think it also matters how deep the fastener is buried. I've had screws that worked a bit over time and cracked the epoxy covering them. Admittedly the epoxy layer was pretty thin. If these screws had been plain steel they would have rusted immediately. 

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Back in the 80's there was a multihull designer here in Australia who recommended that one of his designs with ply decks could be built with steel staples to attach the ply arguing that as it was going to be covered in glass and epoxy then they wouldn't rust. History proved him wrong and soon all the boats had little lumps form on the decks with a rust mark. The swelling of the rust cracked the glass over every staple and let in more water so rot and rust accelerated. It was quite a job removing all those staples and repairing the rotten areas :(

I think that everyone needs to remember that epoxy is very waterproof but not absolutely waterproof.

I'll keep using stainless/bronze.

Cheers

Peter HK

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You can enough moisture in the wood, yet still have it below the threshold for rot to form. Simply put, a dry hunk of wood, still has enough moisture to cause corrosion in mild steel fasteners, even if it's not enough to cause wood rot.

 

. . . In the type of building most of us do I just can not see what the issue could be . . .

 

The builds focused on here are glued and/or taped seam so fasteners aren't as relevant as they once were. I'm putting the finishing touches on a 15' glued lap build. The total number of metal fasteners in the whole of the hull, deck and structure is about 28. I do have some through bolts holding the inner stem to the cutwater, some lags holding the skeg to the bottom and some stem bolts holding the centerboard case logs in place, but other than an odd screw or machine screw, here and there, that's it. It's all goo, silica, milled fibers and other filler materials, bonding everything together. In fact, rather then using a temporary fastener to hold something as the epoxy cures, just to have to remove it and fill the hole later, I've used dowels instead. I can insert these, during the glue up process and they stay in place, eliminating the need for a temporary fastener.

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I sort of like the idea of no fasteners.

 

It seems to me that 99% of these small boats can use epoxy and all the other stuff mentioned above.  I only use them if Graham calls for them and he usually does not call for very many.

 

I might be remembering this incorrectly but I think the Gougeon Brothers built a fairly large tri using only epoxy and it is still going great today after being sailed hard for a long time.

 

dale

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I believe Graham's plans show fastners in many key spots such as where the bottom of the mizzen mast goes into, or on certain pieces of deck framing connect to others. 

 

I do use bronze fasteners I get through Tacoma Screw (they have an amazing selection), For exposed traditional look I would go with bronze, for anything hidden I would use SS, especially since the cost is usually cheaper.

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18 8 stainless steel or type 304 is the most common stainless steel used in fasteners and most boat hardware. I would never use it on the outside, especially under water of an ocean going boat. It suffers badly from crevis corrosion.

 

I have had good success with type 316 SS under water. It is not as readily available as 304 and it is a lot more expensive. On small boats I use lots of 304 and it works well enough. Bronze as has been mentioned is good but not as readily available and quite expensive and you have to be extra careful driving screws as it is fairly soft. I still have some monel screws which are the best if you can find or afford them.

 

We have CS20 hull # 1 in the shop for a minor refit. She was built using all 304 fasteners. We pulled the centerboard and the pin was perfect. The rudder pivot bolt twisted the head off, it was eaten almost in two. The other fasteners that we have seen so far are OK. I think that replacing the odd fastener over the years is a reasonable trade off as the boat is over 16 years old and she has been used exclusively in salt water.

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I agree with Graham, in my experience with ocean fishing dory's here on the West coast the 304 and 18-8 fasteners below water line do not fare well after several years. Though Anchorfast nails used for ply fasteners on their bottoms after 24 years in one case still appeared to be as good as the day I drove them in. Had to do a repair job for a fella that required removal of some bottom ply around the motor well and discovered this.

Bronze boat nails seem to do well as long as the owner is careful of electrolysis damage especially within marinas. We had one of our dorys suffer damage to bronze 3/8 chine bolts  when loosening was noticed between frame and chine and sideply, when bolts were pulled some parts of the bolt were only 1/8 in dia. This boat had spent one season tied up in a sport marina and we think battery chargers or very poorly grounded docks were at fault, as well as owner not maintaining zincs. The bonding strap on these bolts had also been cut at some point in time so not the bolts fault.

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