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Old 09-06-2007, 23:38   #16
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Hi Dave
Your screws should be 1.5 times the thickness of the plank by rule of thumb. However if you have deep sawn ribs 2 inch would be better #12 or #14. Socket type flat heads are the best but may not be available on that side of the pond. I tried finding Robertson screws and screw drivers in the middle east without any success. Once you have used them you will never want to use a Phillips or flat head again. They are a very good Canadian invention.
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Old 10-06-2007, 00:06   #17
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Actually Alan Stainless screws come in several grades 304 ,305 and 18-8 are what many hardware stores carry as stainless screws. 316 is considered Marine grade, applicable in wooden boat construction. 308 is more commonly found where high hardness level is needed not that readily available. I have used them in Industrial applications and they will rust a bit. They are not as soft as 316. Now if use guys would only learn to use Robertson type heads the clouds would part, the sun would shine and all would be right with the world.LOL The best are still Silicon-bronze but the heads twist off very easily.
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Old 10-06-2007, 00:45   #18
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Oh don't worry about the square drives. I have been on to that for sometime now.
Yes the heads twist off silicon bronze, but we tend to have this notion that we ahve to pull screws up really tight. Over tightening bolts is another, but different topic. Screws should be pilot hole drilled, countersunk to the depth they need to be set to and screwed in firmly with a drill with a clutch. NJot over tightend. I break them too, so I am no better that anyone else at it.
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Old 10-06-2007, 10:55   #19
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Robertson and "square" drive aren't quite the same, IIRC one has a tapered wall and the other does not.

But even slotted screws come in a variety of qualities, and most screwdriver bits are simply made cheaply and slip out of them too easily. Hollow-ground or flat-filed screwdrivers are used by gunsmiths and others who can't afford to have damage caused by cheap tools with simple tapered blades on them. I'd suggest that the choice of screw top (slotted, Robertson, whatever) won't matter if you are using the right bit to match--and the screws were properly made in the first place.

I'd also agree that silicon bronze is the only material for this application. Any type of ferrous screw is going to create problems in submerged wood, even a zinc galvanized one. Do you really want to know you've spent the time and effort of driving 4000 screws--and will need to REDO THAT any sooner than you must? (Not me.)

The commercial "wire nails" that we use today, by the way, are another example of cheap inferior products. Old fashioned cut nails (square nails) have more holding power and are a better way to go--but they cost many time more, per nail, to manufacture. Even in the 1800's, in the US west settlers would salvage the cut nails from burned down buildings--because cut nails were relatively so expensive compared to everything else. A cut nail, from what I'm told, spreads the wood grain instead of splitting and puncturing it like a wire (round) nail, so even size-for-size the holding power is several times greater.
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Old 10-06-2007, 13:14   #20
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Thanks for all this advice

I am looking at ordering the silicon bronze screw from the UK and have it shipped here (Turkey).

For my 1" planks I guess that I'll need 1 1/2" screws (or shall I make that 1 3/4" ?) and these should be what ? size 10 or 12 ?

I will try and order a drill bit that cuts the pilot and shank hole at the same time - are these called "step bits" or something like that ?
What size do I need to get ?


Do I need to use a counter sink or will the screw sink itself since it will have a shank hole ? My timber is Turkish pine (not very hard).

BTW
For heavy wood (on land) I have been using a screwhead that has a star (with about 8 points). These are for screws that are about 3" long. Always excellent grip and really power into the wood. I built some planter boxes out of thick preserved timber recently and these screws were great. I dont know what their name is though.

thanks
Dave
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Old 10-06-2007, 13:38   #21
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That sounds like a "torx" drive screw. Didn't know they were available in large fastenings.
Countersink!. You can buy a special drill with countersink head and a collar to set the depth. Use one of those as it will set all the holes to the right and uniform depths for plugging later.
For inch thick timber, I would use 1 3/4" screws and 12g. Sink the head at least 1/4" -3/8" into the timber. Sorry, I work in metric, so I hope those measurements are correct.
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Old 10-06-2007, 13:46   #22
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I am going to go against the "grain" here for a moment and my advice may or may not apply , so take it for what it is worth. I am assuming that this boat may be an older boat, what could be called "middle aged". Eventually these traditional wood boats reach a point where a total rebuild is needed, new frames, planking, and deck, etc. In many cases that is the death sentence as unless the boat is a special boat from well known designer it is just not worth the cost. Now your boat is probably not at that point and maybe just needs some replanking and some other minor stuff done. What is the expectancy here. Are you trying to make the boat sound enough for another 10-20 years. Eventually this boat will require a total structural rebuild and is it worth it? If not, why bother with silicon bronze/stainless steel fasteners now? It sounds like it is already fastened with galvanized fasteners and unless you are replanking the whole boat why go with something differant. You can probably locate galvanized fasteners locally and they do have a significant lifespan, enough for the expected life left in this boat before a total rebuild is needed. If my assumptions are off base then this advice may not apply.
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Old 10-06-2007, 15:29   #23
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Wheels-
An 8-pointed star sounds more like a PoziDrive, not Torx.
Wiha Index Of Pozi Drive Tools for an example. AFAIK they are designed to allow precise torquing in metal applications, not woodworking screws at all. Although sometimes I'm convinced people patent new screwhead designs just to vex the workmen.

In the US we have one-shot countersink/pilot bits available. Inexpensive, usually stamped(?) steel blade, nothing fancy or expensive. They are sold in profiles that match various screw sizes and lengths, so that there is no adjusting or setting necessary. So if you are using a #10x1-1/2 screw, you get the bit to match, and it is one hole, one screw, done.
Although with 4000 holes I think it might require more than one of these to make all the holes--they're not as robust as machine drill bits.<G>

But would you really countersink and predrill, when working in PINE?? I've always found you can just shoot screws into it and bury them flush. Unless you (Dave) are planning to bung cover all 4,000 of them instead of just using flush head screws?
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Old 10-06-2007, 17:03   #24
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For planking I would recommend only silicon bronze or monel wood screws. Ring nails have a lot of holding power for a direct pull, but don't have much diameter for sheer stress (plank sliding across frame). Apparantly on a traditional carvel planked boat, the fasteners are mostly in sheer, so diameter is important. I think that's why the old square nails were used for quick and dirty workboats, because they had plenty of bearing area. I agree that stainless steel is a no-no for planking fasteners. For length, the unthreaded portion of the shank should go all the way through the plank and into the frame if possible.
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Old 10-06-2007, 21:29   #25
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Dave
Are you suffering from information overload yet? LOL There have been a few good points made in earlier posts as to inquiring about your long term plans for the boat. Steve had a very valid point as to how much and for how long. I previously asked about the depth of the ribs. Chosing a screw lenght is going to be different if your ribs are 1 inch bent oak or 2 to 3 in. sawn fir. You don't want the screw tip going through the rib. If you have 1 in. plank and 1 in. rib (thickness) and you sink the flat head 1/4 in. 1 1/2 in would be the longest you would want to have. If however you have 2 in. ribs you could safely go to a 2 in. screw which would be better. Posidrive screws are modified phillips and suffer the same problems with camming out. Torx were designed for the automotive industry but are now getting into wood screws etc. If you can get them in the desired material they are great for power application but are a bitch to clean out and remove once putty has been used to cover. Robertson are great for power application and are easier to clean out. The fishing boat I previously mentioned had been nailed using square, cut tapered, galvinized boat nails and was over 30 years old when I refastened and recaulked it. So if 20 to 30 years is all you need then boat nails might be an easier and more economical choice. What ever you do, try to enjoy yourself.
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Old 10-06-2007, 21:33   #26
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1 1/2" screw in 1" plank

I would not expect 1/2" of screw thread to have any real holding power.

If there is room the old method of using copper rivets may be applicable.

If it were my boat I'd drill out the nail holes undersize, allow to dry and then saturate with epoxy resin. I'd then use stainless steel countersunk machine screws set in the wet epoxy to hold the planks. The epoxy would probably hold them well enough but I would use nuts and oversize washers where they could be fitted.

The el cheapo countersunk bits that I have been able to buy only work well if the drill is at maximum speed. A dedicated mains powered drill would speed up this part of the work.

#2 Philips heads with a bit in good condition and short bursts of low speed works for me. I throw away any screws that get damaged.
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Old 11-06-2007, 03:53   #27
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Copper nails and coopper roves are the way to fix wooden planks to wooden frames,my grandfather used this to build fishing boats in the 20s-50s and some of these are still around and being used.A 32ft boat i rebuilt 15yrs ago i replaced all the copper nails and roves below the water line it is still sound and water tight today.Greg
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Old 11-06-2007, 06:46   #28
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What are roves ?

BTW
the star type screws are 6 sided ( I cant count ! )
and they are called torx. They only appear to be in the large size of screw - and yes I agree that they would be a hell of a job to get putty , or varnish, out of if they even had to be taken out again !
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Old 11-06-2007, 07:01   #29
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Copper roves (or burrs) are slightly conical washers.

A copper nail is hammered through the joint, a rove is pushed over the end (concave side inward) and the nail is peened over so that a rivet is formed.

Riveting is a matter of through nailing two pieces of wood, slipping a washer over the pointed end of the nail, pushing it down the shank against the wood and then nipping off the excess nail leaving just enough excess to peen over the washer to lock it tight.

All copper riveted connections are made using two parts: nails; called the "rivet" and washers; called "burrs" or "roves". The rivets are generally just copper common nails; however, European boat-builders generally prefer the conical head and square shank of the Rose Head Boat Nail. Either way, the nail goes into the slightly undersized pre-drilled holes and through the pieces of wood to be joined. A burr with a slightly undersized center hole; to provide an interference fit, is then placed over the nail point to be driven down the nail shank. At this point you will need a Rove Set tool. We offer one here but you can make your own with a piece of rounded hardwood or a 1" hardwood dowel about 6" long. Drill a hole in one end, on center into the end grain deep enough to accommodate the exposed length of nail and size it slightly larger in diameter than the nail shank, and now you have a Rove set.

A heavy back-up tool is required to "buck-up" the head of the nail prior to setting the burr and forming the completed connection. We offer a heavy (4) pound hammer with a short handle suitable for this application. Now, to make the copper rivets connection, first tap the nail through the pre-drilled pieces of wood to be joined and back-up the head with the "buck" hammer. Next, place the burr over the nail and drive it down the exposed nail shank using the rove set tool applying light taps from a hammer. The burr should seat firmly against the wood. Using a set of diagonal cutters nip off the excess nail leaving about a nail diameter in length beyond the burr to peen over. Holding the "buck" hammer hard against the nail head, take a lightweight ball-peen hammer and start tapping with the flat end to mushroom over the cut nail stub. Finally using the rounded end of the ball-peen hammer tap the mushroomed stub around the edges forming the end to lock down the burr and draw up the connection.
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Old 11-06-2007, 20:49   #30
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The problem with copper rivets is that total inside access is required. This was a very popular system used in thinner planked wooden boats that had open ribs inside. It is a very good system but is somewhat impractical unless you plan on gutting the interior of the vessel.
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