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How about stainless steel screws in the side panels

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How about stainless steel screws in the side panels

Postby FCE woodiesparts » Wed Aug 10, 2011 2:30 am

Can we use stainless steel screws in the side panels?

one would think yes. It is not under water!

Check with me the following idea:
The sides are painted on the inside and varnished on the outside, we plug the bugs in with glue and many times the glue touches the screws. So we have an oxygen poor environment, yes?

Let's take a close look to older Rivas with the original side flanks.
They have black stripes and black areas around the screws. That is mostly from sea water.
So we have a problem their,do we?

Let's take a look on how Carlo riva did it. The first boats he made , he used silicon bronze screws. But later( around 63 if I'm not mistaken) he changed it to chromed screws. Why ?
Read the other topic I wrote and you'll understand.
So we started fabrication chromed silicon bronze screws. We personally think that would be the best option.

Tell me your idea....
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Re: How about stainless steel screws in the side panels

Postby Don Ayers » Wed Aug 10, 2011 10:30 am

FCE;

Very good post.

I have seen the voids in the original side panel construction. I guess that the inner wood strips were not able to be held 100% tight when the side panel was pressed. The void left can allow water to inner between the layers and then mold. This causes the black strips. See pics

New construction avoids this problem with tight fitting inner and outer layers.
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Don Ayers
Oklahoma
1959 Ariston 266
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Re: How about stainless steel screws in the side panels

Postby Eric T. » Wed Aug 10, 2011 10:42 am

FCE woodiesparts wrote:Can we use stainless steel screws in the side panels?


Let's take a close look to older Rivas with the original side flanks.
They have black stripes and black areas around the screws. That is mostly from sea water.
So we have a problem their,do we?

Let's take a look on how Carlo riva did it. The first boats he made , he used silicon bronze screws. But later( around 63 if I'm not mistaken) he changed it to chromed screws.
...
Tell me your idea....



Here is my opinion, for what it is worth.

I agree with you that silicon bronze screws should be used for the construction... although this is contested by some builders both here in the USA and in Europe.

The physical properties of Stainless Steels (Inox) in an oxygen deprived environment, as you have pointed out, are well known in the boat building world... and there is much "hot discussion" among builders about the bronze/Inox topic.

I have seen many old Rivas in the storage yards (Magazines) of USA and European yards and of private collections... Some original boats (with original hull sides and screws) show heavy corrosion of the bronze hull fasteners , with the "halo" around the bung, and other equally vintage boat with original hull-sides/screws show no evidence of this. This was true of the early Tritone and Ariston boats from the 1950's as well as later Aquarama boats from the 1970's and 1980's.

I have also seen an iron (ferro) "halo" around the bungs on some recent Riva restorations used in ocean water that used stainless steel fasteners on the hull sides behind the wood bungs.

In the yachting world, I have been exposed to stainless (Inox) screws used in fairly recent repairs and others up to 40 yrs old... in many of these repairs the stainless screws holding planks to the boat had become corroded and weak. Many of these were embedded in epoxy.

When installed with modern methods, and the proper screws using a urethane bedding compound... the Bronze chine protectors work well and protect the original appearance of the boat.

I also believe that the staining of the plywood laminate hull sides in the original construction is from fungus making the wood black in the gaps between the diagonal layers of the lamination. Water enters these diagonal gaps in the planking of the plywood and becomes trapped and stagnant... this allows fungus to grow and causes the famous black stripes.

Here is a photo of an early Aquarama with the outer layer of the hull side removed showing the gaps in the plywood laminations... I have seen much worse with heavy fungal growth between.

Image

Have a look at the inside layer of the boat (the engine room is a good place for this). You will see some that have the planks tight in the plywood lamination and others that have wide gaps and sometimes splits.

I believe that Riva went to Nickle plate bronze screws in the mid 1960's...Is there some reason to believe that this was a nickle-chrome process on the hull screws?

There is also a difference in quality for the screws... some are Silicon Bronze (Everdur) others are lower grades of bronze or even brass.


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