Screws vs Nails

[Dave-Fethiye]

Thanks for that information about the copper riviting system.

I think for now I'll stick to using silicon bronze screws.

Just one thing though ... I was going to use cotton to caulk the joints but if I use a marine glue as well as the screws there wont be room for the caulk - so as this is just a couple of replacement planks, shall I glue and screw and forget about the cotton caulking ?

Thanks

[Steve Rust]

Some wood boats were built using what was called batten seam construction where thin wooden battens were glued into the calking seams instead of the traditional cotton. The planks were fasten in the usual manner with metal fasteners. This is only effective in boats that spend a minumim time out of water as the glue cannot overcome the force of the planking shrinking and swelling to any great extent. I don't think using glue in place of the cotton is a good idea. As the planks swell from being in the water it compresses the cotton, tightening the seam and strengthing the boat. If you use glue it will either crack as the planks shrink or swell and possibly impart stresses into the frames that may cause them to break.

[Dave-Fethiye]

Thats an excellent point.
Thank you for that comment Steve, it makes sense especiaiiy as my boat is pine and no doubt absorbs a lot of water.

In the docks I have seen them building new wooden boats with all the wood glued together - but the wood was dark - probably teak - or maybe mahogany. In that case I guess that the wood doesn't take in much water and therefore doesn't cahnge much and doesn't need cotton seals.

Thanks again.
Dave

[Tropic Cat]

bronze screws. They must be countersunk.

In my misspent youth, my job was steaming and bending oak planks and persuading them to stay neatly attached to the rather old wood boats we were rebuilding. We used a core bit to cut our bungs from oak and paid attention to match the angles of the countersinking bit. I'd use 1 3/4", and use bungs, not putty. Dip them in Shellac as Alan already mentioned and tap them in with a wood mallet. We used a coping saw to cut them once they were in place and a belt sander ( yes they had those in the good old days), to sand them flush.

Boy, does this bring back memories

Rick in Florida

[BBill]

Some comments from the peanut gallery...

Lots of info here. Pascoe is no dummy but he leaves some details out. When using round nails you pilot drill...it was common practice "back in the wood boat days". When using square nail you MUST size them correctly. Squares always look too small but they work fine. Either is good for 25 yr in saltwater if materials are NOT mixed and running gear properly protected with sacrificial zincs. Changing materials below the waterline is pixx poor practice, no ifs, ands or buts about it. No matter how close they are on the nobility scale it starts electrolysis. Old galvanized are always wasted worse in the areas around bronze thru hulls, struts, suffing boxes, etc. Bronze fasteners also waste worse in areas around bronze or stainless running gear. Running gear has sacrificals and fasteners don't. Fasteners in traditional wood hulls have enough moisture around them to create a path. Galvanized wastes at the head or joint and shows it as a reduction in size...bronze wastes thoughout the fastener, it looks the same size but turns pink as it gets weak...brittle.

I've pulled 30yr old galvanized screws out of garboard planks and they looked perfect. Pulled 20yrs old galv below the waterline that were 50% wasted. I've pulled 20 yr old bronze out of garboards and that were and weren't pink...pink is wasted. I've pulled 25yr old bronze fasteners on teak decks that were even totally wasted.

On the caulking part. Batten seam construction is a specific building method...it's not readily converted to other construction types. Stay with cotton and flexible caulk if the boat needs recaulking. Or be ready for a leaker after a few seasons.

One thing I see posted every now and then is that SS rusts when deprived of oxygen. It would be nice to see some scientific data posted on that because it goes totally against what empiracle data shows. SS is THE material used for gaseous nitrogen (GN2) and liquid nitrogen (LN2) delivery and vacuum systems. Nitrogen has no oxygen and those systems lasts longer than anyone cares to measure. After 20yrs the SS that has been exposed a 100% nitrogen atmosphere is still perfect...and we are talking ultra high purity deliver systems for manufacturing semiconductors.

bb

[hellosailor]

bb-
Your comparison of stainless in nitrogen systems and nitrogen in boats is totally invalid. The nitrogen is extremely dry, there is typically near-zero water content in it and it is actually used to dessicate phone lines.
The problem that is so well reported with stainless has to do with continued immersion in stagnant (oxygen depleted) water, and it is the WATER that is the problem. Without oxygen, the water causes the other crevice defects to occur.
No need to study it further, it is that simple a split. Make the nitrogen "wet" and you'd have the same problem. But, I'd also bet those big stainless nitrogen tanks get visual inspections and hydros regularly--so they are pulled before they fail.

Now, since every metal has some problem, how about just making cut nails from lexan or a similar engineering resin? No galvanic problems, stronger than the wood they bind, ought to last forever. Coupla sheets of plastic and a waterjet cutter to turn 'em into nails, and you'd have a fast cheap test bed to work with. (But if you don't give me patent rights and royalties, I'll come get you.)

[BBill]

Originally Posted by hellosailor

bb-
Your comparison of stainless in nitrogen systems and nitrogen in boats is totally invalid. The nitrogen is extremely dry, there is typically near-zero water content in it and it is actually used to dessicate phone lines.
The problem that is so well reported with stainless has to do with continued immersion in stagnant (oxygen depleted) water, and it is the WATER that is the problem. Without oxygen, the water causes the other crevice defects to occur.
No need to study it further, it is that simple a split. Make the nitrogen "wet" and you'd have the same problem. But, I'd also bet those big stainless nitrogen tanks get visual inspections and hydros regularly--so they are pulled before they fail.

Now, since every metal has some problem, how about just making cut nails from lexan or a similar engineering resin? No galvanic problems, stronger than the wood they bind, ought to last forever. Coupla sheets of plastic and a waterjet cutter to turn 'em into nails, and you'd have a fast cheap test bed to work with. (But if you don't give me patent rights and royalties, I'll come get you.)

I hear ya but...
LN2 is Liquid Nitrogen and as wet as water. This is getting far away from the "lack of oxygen" causing SS to corrode though. I worked with SS and nitrogen delivery systems for 24yrs...never saw a problem and the vacuum jacketed LN2 systems were only pumped back down when the vacuum in the jacket was low. Large tanks are not SS...there is no internal corrosion and the nitrogen is filtered for contamination at point of use. All H20 has oxygen in it. DI (deionized water = no minerals) has oxygen in it. There is no such thing as water without oxygen on a sailboat.

So where is credible data from the ASME or whoever that backs up the statement that lack of oxygen causes SS to corrode? I'd like to read it on my own and leave hearsay out.

bb

[GordMay]

It’s not lack of oxygen alone, that causes stainless corrosion - but removal of the original chromium oxide passive film, in an anaerobic environment.
Hence, a passivated SS pipe will not corrode, even in an oxygen depleted environment, unless & until the passive film is somehow removed (scratched, abraded).

[Alan Wheeler]

Firstly, Nitrogen is an inert gas. It will not corrode. Nitrogen is also very pure in it'self. Because of the way it is made, it is at some point a liquid. It maybe stored as a high pressure gas afterwards and is how we normally would come in contact with it. It can be obtained in liguid form, but it is not something to play around with. Anyway, I digress.
As Gord has stated, it is passivation that protects SST. The Chromium reacts instantly to the pressence of oxygen. It creates a thin film of Chromium oxide on the surface. This thin layer is non-reative and completly insulates the chromium from further contact with oxygen, thus stopping further reaction. The oxide layer is continually being renewed. In fact, the SST is actually slowly depleting away. But as the oxide is only electrons thick, the depletion is so little, we never see it. Give a pin a few thousand years, and it most likely will deplete away to nothing. So take the oxygen away from the SST surface and eventually the oxide depletes away till there is nothign but pure Chromium. This is a higly reactive metal in a pure form. Any acid will cause it to react. Remember, SST is not pure Chromium. It is an alloy of many metals. Iron, Nickel and so on. These dissimilar metals work against themselves. This is what causes Crevise corrosion by the way. But add an acid to the surface of the oxygen starved SST and the metal starts to desolve away very quickly. The acid is naturally created in timber when it is wet. Because chromium is so highly reactive, we are talking very weak solutions of acids and it is certainly strong enough in wet timbers.
Oh by the way, you can get oxygen starved water. Distilled water can have virtually no oxygen in it. The fact that water is H2O, does not mean it has free oxygen.

[cburger]

Hi Dave,

I build wooden sailboats, Silicon Bronze square drive screws with a matching tapered drill bit and countersink and an appropriate sized plug cutter are all you need. Always try to cut your plugs out of the same material you are fastening. Any size Silicon Bronze fastners are available from Jamestown Distributors in Rhode Island. They supply the pros, request their catolog also, filled with great info. The suggestion to see Wooden Boat magazine was also a good one, past issues with the info you need can be back ordered (on the web). They can tell you exactly what size screw for the size of your planking and ribs as well as how far they have to be set to get the most out of the fastener.

Cheers,

CB

[Dave-Fethiye]

And Finally,

Just as I was about to order some SB screws for my replacement timbers,
I got thişs comment about using them...

"It's not a good idea to mix fastener material below the waterline. Unless you plan to refasten the entire hull with bronze, stay with galvanized fasteners. Mixing the two will cause galvanic corrosion problems."

So looks like I should stick to the galvanised nails after all

Dave

[Lancerbye]

yes since you only doing a small section. That would be best. If you were doing it all the choices could be different.