What kind of screws to use?

Hi, everybody, this question comes from Greece.

I am about to built a new boat. A traditional kind of boat called "Varkala", and it will be equipt with sails too.
It's going to be 8,5 meters long and made of pine.

The question I have is this:
What kind of material is better for the srews I gona use to srew the planks to the frame.

Now, I have heard about silicon-bronze srews which are more resistant to corosion. I agree with that, but how much "bigger" is the benifit. Or, how much "worse" is stailness steel in compare to silicon-bronze.
Does somebody knows after how much time SS-srews should be replaced and after how much time silicon-bronze srews?

I ask because the use of SS-srews instead of nails has arrived to our places just the last decade(and silicon-bronze not at all), so we don't have much knoledge how these materials respond to time and wearness.

In a previus boat I built (12 years ago) I used stailness steel srews and I haven't notice any problems so far.

Consider as well that the boat will recieve very good maintence.

Thanks for reading,
regards, martinos

 

I don't think it matters very much whether you use silicon bronze or stainless screws. It is best to avoid mixing different metals on the same boat if it can be avoided, especially in salt water. One virtue of a stainless screw is that it is less likely to be deformed by the driver bit. Some of the modern types of driver bits minimize this problem somewhat for bronze. A very mild form of electrolysis can occur between the wood itself and a metal fastener which causes a very slow deterioration of the wood in the immediate vacinity of the fastener. Dipping the screw in something like linseed oil helps to minimize this by sealing the wood and slowing down the process and it also lubricates the screw so it drives easier.
And then you always have the possibility of materials on other boats moored close by and stray electrical currents from various sources that can cause problems too.
Of course you may have known most of this already but it never hurts to mention things that can be helpful.
I, for one, would like to see a picture or drawing of a Varkala if you can arrange it.

 

Usefull informations

Hi, Gilbert

what you wrote is very usefull. And no, for the half of it I had no knoledge of it.

I'm going to search for Varkala drawings, etc.

Thank you very much, regards Martinos

 

IF you use Sil/ bronze, you need be very careful they are up to strength, some chinese stuff has all the strength of a good gruyere cheese But made in uk or usa they will be very strong
I would go ss,316, SQUARE DRIVE , you can buy a sqaure drive hand driver of a driver to put is a drill, they are commonly number one 2 and 3 in sq size, the advantages are many, especially you can hold the screw in the driver and leave the other hand free, try that with pozi, or slot
Once again where they are made is important, some ss are like cheese too

 

Thanks Whoosh!

 

Three cheers for the Canadian designed Robertson (square) drive screw!

The majority of screws sold here in Canada are Robertson drive, and growing up with them makes us spoilt. I can't stand slotted screws!

Martinos: I to would love to see some pictures.

 

Personally I sometimes have problems camming out square drive SS screws. What works well for me is a cordless impact driver rather than a cordless drill for driving screws. I'm a carpenter and a Makita cordless impact driver has changed the way I work. A little pricey for the tool but so sweet. A good value and similar to the difference between a nail gun and a hammer, well maybe that's a bit optimistic but still a radical difference. My .02

 

On my boat, fresh water only, I used galvanized philips for
the structure. On the trim and any thing that showed I used
slotted bronze as would be found on a boat of the early 1900's.

Plilips were invented in the early 1930's.

Note the philips in the knee under the seat, I couldn't get
#10X3" in the bronze without buying a box of 100. I needed
a dozen or so that long.

 

Robertson (the square head screwdriver) is about the best head you can get for hand driving. However they do have disadvantages.

1. You need to keep your bits in good shape. Buy high quality, and buy often. The Robertson is less forgiving of slightly deformed tools than Phillips or Slot.

2. They are NOT designed for power tools. If you are really worried about working fast with a power tool, then go Phillips, it was derived from the Robertson's concept, but designed to easily disengage bit and screw for various reasons. You can still use a power tool for them, you'll just have to be a little more careful to not damage the head or the driver.

3. Buy only quality screws and drivers, cheap knock-off screws with a poorly defined head are a pain to use. You also shouldn't be skimping on screws anyway, poor heads go hand and hand with poor metals.

The biggest advantage of the Robertson will always be the ability to stick a screw on a non-magnetic head, and expect it to stay there even after you take your hand off it. Few other fasteners have this advantage.

 

Take a look here.

http://www.naftotopos.gr/index.php?option=com_content&task=blogcategory&id=61&Itemid=119

These are models of "Varkala".
I will tranlate some of the information a.s.a.p. and look for some "live" photos too.

 

Another cheer for the Robertson driver here.... they're the de facto standard throughout Canada, simply because everyone finds them so much easier to use than slotted or Phillips. (As long as you have good quality driver bits, that is.) For fast machine driving, of course, the self-centring Phillips is the bit of choice, being designed specifically for this type of use.

I'd be a little reluctant to use stainless steel for wood-to-wood fastenings below the waterline. Stainless is vulnerable to some rather complex forms of crevice corrosion when used in areas where it won't be exposed to oxygen (without oxygen, it can't form its protective chromium oxide layer, and goes into an "active" state where it wastes away scary fast). Silicon or nibral bronze, although expensive, might be a longer-lived choice ("manganese bronze", actually a kind of brass, is Very Bad). If you're on a tight budget, I would probably be tempted to suggest hot-dip galvanized mild steel ahead of stainless; at least mild steel lets you know when it's corroding.

 

Try it here for Bronce screws and bolts:

http://www.boegerschrauben.de/csshtml-e/2products/prod-specp.html
http://www.gevag.de/

Richard

 

A bit of a random question related to this, but just how common are Robertson style heads out side of Canada?

And are there any other designs that allow you to attach the screw to the driver and hold it with one hand while you hold it on its side? (Or even at a fairly steep vertical angle with good equipment.)

 

Here the majority of currently sold screws start to be equipped with Torx or T-tap heads.

http://en.wikipedia.org/wiki/Torx
http://www.ttapdrive.com/

Both hold a still loose screw in the bit wonderfully and guide it while screwing in.

 

Well, looong ago.