SS in timber?

[Crazyhorse 47]

Cant get over the cost of silicon bronze screws but was told 316 screws are OK in timber if used above water? As this is the bow roller foreplate going on its going to be often IN the water so hoping someone knows if this is a good idea?

[ex TL systems 63]

If the bow roller is ss then I would think that the screws should also be ss. Every plywood boat I have had has used ss screws to hold cleats etc and I have never seen any of them dissolve.

[Crazyhorse 47]

Cheers mate. Couldn't believe the cost of bronze screws!!

[wheels 543]

It depends. Is there ever any chance the timber could get damp? or is it sealed over with Fibre glass? If not fully sealed, DO NOT use SST. SST will not last if the timber gets wet. Maybe a year or two at the most.
When using SST, ensure the timber is well sealed. When you drill the screw hole, seal it with evadure or similar, Then place sealant around threads and screw home.
How many screw do you need to hold down the Bow roller anyway? Where are you buying the screws? They shouldn't be that expensive. You are probably buying from some rookery nook

[Crazyhorse 47]

Gidday wheels. Holger at Norsand, $9 for large SB screws. Need 6 biggies and about the same in small screws. Yes, F'glass right over the cap and sides (once this rain stops!). Noel was working here yesterday so asked him about it. Said basically the same as you but no countersunk screws and to get the holes redone in the bow roller, welded over and re drilled! ($$$!!?). So going sst hex heads all round.

[wheels 543]

Go to here https://www.bronzeandbrassfasteners.co.nz/#silicon-bronze-brass-fasteners and then click on Silicon bronze price list.
But hey, SST will be fine if it is all sealed up.

When I first found out about SST in Timber, it was due to me doing some repairs on my Boat. I found all these rusty fastners. Both Nails and screws. I became really annoyed that the builder had used plated screws and nails, never in my wildest dreams ever thinking that SST would do what it did. It wasn't till well into the project that I discovered that SST will rust in damp timber. Apparently the Timber creates an acidic environment and the SST is Oxygen starved and the Fastening just rusts to bits in no time. The result is a hole where the Fastener was, a discoloured stain in the timber of quite some size out from the fastener and a nothing but this sliver of rust in the hole the fastener once was. I was absolutely stunned.

[Crazyhorse 47]

Yep, thats my understanding too. Two screws on the flat surface had totally been eaten through, only the countersunk head remained which simply fell off under the screw driver. Had to go digging to get the rest out. The others on the leading edge of the bow were fine but loose. It would seem sea water getting in setup some kind of galvanic reaction in the timber and desolved the wood (or at least softened it). My direction now is to fill the holes with a thinned down epoxy then use hex head sst screws with fibre washers which are epoxied too.

[Crazyhorse 47]

Oh, been warned to use washers, not weld and drill the plate as it will temper it. If I can keep the water out, everything should be fine? When you say "plated screws" are you saying galvanised!!!??

[rmiker 15]

If you are looking for a long term maintenance free installation  use silicon bronze.. End of story!!

 

These days you could probably use a duplex SS screw/bolt i.e 2205 if you can find one which I doubt and if you can it will be the same cost as s/b.

 

There are no shortcuts here. 316 SS and timber do not mix long term: The time frame is only governed or limited by the moisture content and that will go up and down constantly it will never be dry...

[Chewing Gum 17]

316 in timber will be fine. Use plenty of sealant. Our Lidgard built in 1982 had all deck fittings refastened around 10 years ago with 316.

The old fastenings were all sst and likely only 304 from that time. Out of all the deck fittings from memory there was only one that showed any corrosion of the fastenings and that was in the aft part of the boat. The stem head fastenings were fine.

[wheels 543]

316 is no better than 304. In fact in some cases, it is worse, because it is more brittle and suffers work hardening, cracking and crevice corrosion easier than 304. The difference between the two is that 316 withstands Chlorides better than 304. Salt is Sodium Chloride. So 316 is better for total immersion situations.
As already said, SST will be OK if completely sealed. But get damp timber around it, it will offer no protection at all.

[ex TL systems 63]

But it seems to work fine when used as specified outside for timber decks etc on buildings where the wood is often wet, ss bolts are still holding my deck up after 20 years

[wheels 543]

Yep, it can "breath" in that environment ex TL. The timber is not tight enough to starve the metal of oxygen. Where as in a Boat, it is encapsulated and can't get any oxygen at all.

[Crazyhorse 47]

A foot note. Have gone SS coach screws, bow roller now in dispite the weather. Was told by Noel here SS fine ABOVE waterline in timber. Seal it as much as possible so water can't get in, don't worry about air. Used nylon washers and epoxied the screws in. Will post a pic after sanding etc as it looks a mess at the moment.

[wild violet 38]

Couple of years ago I pulled my bowsprit off to paint it ,the 25mm ss bolt holding it on came out in 2 pieces completely rotted in half.Have smeared new one in grease hope it holds.

[wild violet 38]

If it breaks the bowsprit will just move back about an inch so not too worried.cant fall off too many stays holding it.