Screwed up?

[Miami Mike]

Hello all,

As some of you may know from my rare previous posts, I'm working on a Penobscot 14, my first attempt at boat building.
I'm wondering if I made a mistake in the type of screws I purchased. The penobscot calls for about 1300 or so stainless steel screws. I know there has been discussion here as to whether there is truly a need for this many screws in the design but as it's my first stab at this I'm trying to follow the designers plans to the letter.
Following advice from the forum, I checked into online screw vendors (Hamilton marine & Jamestown for example). I also checked some local commercial sellers as I work for a lumber company and thought I could get a good discount. The screws I bought were half the price of the stainless from the online retailers including a box of 100 #10 2-1/2" stainless steel flathead philips for $8.00. This was about a third of the online sellers.
This leads me to question whether I actually bought the correct type of screws. The box reads:

1040APF.03
#10 X 2-1/2"
PHILIPS FLAT HEAD TYPE A 18-8 ST/ST
QTY : 100 BIN=G13D

Hamilton Marine was $25.99 for this box. The only difference I can see is that The picture on Hamiltonmarine.com shows a smooth throat on the screw and the ones I bought are threaded all the way to the head.
Did I screw up! Are my screws for some other use? Your help will be appreciated!

Thanks: Mike

[scepticus]

In any sort of woodwork, the ideal screw is one where the threads do not bridge the joint between the pieces being joined. However, that's often difficult and sometimes impossible to achieve, so the most important thing here is that the pieces are clamped tightly (dry) before a proper sized pilot hole is drilled, then goop added if any, then clampled tightly again, then screwed.

The idea is that the screw holds together what the clamp has already pulled together. you don't want to try to tighten up the joint by screwing tighter.

Therefore, while not ideal, it isn't a disaster having the threads all the way up.

[Paul Scheuer]

What are the 1300 screws doing ?

[Norm Bernstein]

I believe that stainless screws with threads all the way up to the head are actually 'sheet metal' screws... ones with a partial smooth bore are genuine wood screws. The truly skilled and knowledgable on this forum can give you the pros and cons. I do know that the fully threaded screws are more easily obtainable; even the local Lowes stockes them, albeit in small quantities, poly-bagged, and at a high price.

[Brian Palmer]

I'd talk to the designer. I do not see where on that boat you could use so many of that size screw (it appears to be glued lapstrake construction).

I would not use sheet metal screws in place of wood screws. Right now I have toe rails that were fastened with sheet metal screws and water got under the lower edge (because they could not be pulled down to the deck) and they are rotten. The Jamestown Catalog site has good tech info on different types of screws (JDs decoder).

Good luck!

-- Brian

[Dave Gray]

I don't know if this is just adding noise, but I too can't believe a glued lapstrake boat requires 1300 stainless screws. The only thing they might be used for is to stitch the laps together while the epoxy dries. For all practical considerations, drywall screws will pretty much do the same thing. It won't matter if the threads go all the way up the shank because you won't want to drive them that far. You will only want to drive the screws far enough to bind the planks together.

This assumes that the screws are used for stitching.

[Stephen Hutchins]

They'll work fine. Enjoy your screws!

[Steve Lansdowne]

I believe many of those screws act as temporary fasteners while the epoxy/glue dries. I once asked Arch how I could reduce weight on this boat and he suggested backing out all the screws once the glue was dry. There are various types of stainless. See the Jamestown Distributors catalog for particulars.

[rregge]

Wood screws will enable you to pull the joint tighter than if you use machine screws.

If you clamp the boards together tighly and them screw them u should be ok.

Ruseell

[Bruce Hooke]

How deep are the threads on the screws you have? If they are as deep as standard wood screws then they should work fine. If they are much shallower then they are probably true sheet metal screws in which case you may find that they strip out easily when you are driving them.

[Miami Mike]

Thanks for all the replies.

After a little research last night, I do believe that they are stainless steel sheet metal screws. As far as the depth of thread, they appear at least to my eye to be of equal depth to some stainless wood screws I have at the house. I tested a few using plywood to plywood and wood to wood and they seem to hold okay.

For those not familiar with Arch Davis designs he uses screws instead of clamps. A "belt and suspenders" approach as some have called it here. I also weighed the screws last night. 7 lbs in total including all the boxes and the 50 extra 2-1/2 that are in a box of 100. I don't think the weight is that big of a deal, at least to me.

I think I'm going to use them as they were about $50.00 less than the wood screw on line quotes. Since the epoxy really is doing all the work, I'm hoping that this should be okay.

Unless someone here can tell me I'm making a HUGE mistake! And then of course I'll spend the extra $50.00!

Thanks: Mike

[Bayboat]

The sheet metal screws, often called "self-tapping", are OK if the joint to be screwed is clamped for a flush fit. If you want to back out the screws after the adhesive has set up, stick them in some wax before driving. Also wax them if driving into oak, as in frames. A toilet ring, costing about a dollar, works fine.

[Norm Bernstein]

I hadn't thought of waxing the screws first... but I often use cheap 'big box' screws to 'clamp' a joint that has been epoxied, and I've never had a problem backing them out after the epoxy has cured.

[davef]

I think the screws will work just fine. My experience is that the SS screws are much softer (the ss used for screws usually cannot be work hardened or heat treated) than the silicon bronze or conventional carbon steel screws so I would recommend using a cordless driver with a clutch to prevent torquing the heads off. With a phillips head that's less of an issue than square or torx drive anyway...

For what it's worth, there are some useful bits of information on the McFeely's site www.mcfeeleys.com (http://www.mcfeeleys.com)

including the following which I've cut and pasted here.....

Regular vs BoatBuilding
There are two ways to manufacture screws: At one time, all screws had machine-cut threads and a shank diameter equal to the outside diameter of the screw thread.(Right Image)
Now, modern heat-treating and screw manufacturing processes create a reduced shank fastener with a rolled thread that usually requires nothing more than a pilot hole, making life so much easier for most recreational and professional woodworkers. (Left Image)
Many boatbuilders, especially those near salt water, prefer a screw with a full-body diameter shank. Unlike the reduced shank of a typical roll-threaded screw (like most of the screws we carry), the full-body shank fills the clearance hole boatbuilders usually drill in the first board, creating a rather good seal as water swells the wood. The bottom line is, the boat building screws are optimum if you need to seal a fastener hole in a wooden boat, but use our regular Silicon Bronze for other applications.

Information on materials:

Un-Plated Hardened Steel screws are the most popular, and are primarily used where they will not be visible or exposed to corrosive conditions. Their color variation from almost pure black through a bronze to silvery grey does not affect quality – it is simply a result of process-variable interactions as simple asthe screw’s location on the heat treat furnace conveyor belt. All McFeely’s Un-Plated screws receive a Dry-Lube finish which reduces driving torque requirements, but provides virtually no corrosion resistance. Hardened steel screws are the base stock for all our plated screws.
Stainless Steel provides the ultimate corrosion resistance for most woodworking projects. It is softer than our hardened steel screws because stainless steel is not generally heat-treatable – the wire must be soft enough to be formed, yet hard enough to provide the desired strength. We carry stainlesssteel in a variety of grades. Note that not all grades are designed to be completely “stainless”!

Aluminum is surprisingly strong because it work-hardens as it is formed into screws. Ours are made of 2024-T4, an aircraft grade suitable for screw manufacturing. These screws are just the thing for assembling aluminum doors, windows, or gutters because they eliminate the corrosion problems associated with the more common use of zinc plated fasteners.


Solid Brass screws are also very soft, and virtually demand a carefully sized pilot hole to eliminate installation breakage. (Pre-threading the hole with a steel screw helps minimize this problem). A Square Recess really makes a difference with these screws. The softness of the brass greatly increases cam-out problems with most other driver types, a situation neatly overcome by the Square Recess.


Silicon Bronze screws are primarily used for marine boatbuilding, although many people have used them to build decks made of Western Red Cedar or Redwood because the screws will eventually blend into the color of the wood. As pictured, screws right off the production line are generally the color of a fresh penny – after they have been around awhile they oxidize and darken as shown in the “Oxidized” Silicon Bronze picture.

Information on thread types

Thread Types
Deep Thread
Characterized by reduced diameter shank resulting in a a deep thread profile. A single lead thread, meaning that one revolution advances the screw one pitch. (Pitch is equal to 1 divided by the number of threads per inch. For a screw with 10 threads per inch, one revolution will advance the screw 1/10” into the wood.) The deep thread form provides superior resistance to pull out.

Double Lead
Two threads are wrapped around the shank. One revolution advances the screw 2 pitch lengths - advantageous on long screws or in situations requiring rapid assembly. Drywall screws typically use this thread since pull-out strength isn’t as important as speed. These screws lack the pull out resistance of “Deep” threaded screws.


Tapping
Also known as “Type A” or “Wood Tapping”, this is basically a sheet metal type thread. It is a single lead, fine thread design (more threads per inch). Also, the thread form is basically an “equilateral” triangle, instead of the special “flattened” triangular thread used for “Deep” threads. Generally the entire screw shank is threaded.

Wood Screw
A single lead, extra thick thread used primarily on solid brass or silicon bronze screws to accommodate the limitations of these soft materials. Unlike the traditional wood screw thread, the shank is of uniform diameter throughout most of its length. (Many wood screws are tapered.)

[hbrochs]

I'm building the 14 now, almost done planking. I mail ordered the ss screws from Hamilton, but I ordered less than Arch called for and I just back most of the screws out and re-use them. I didn't put wax on them and they back out just fine. I usually glue planks in the evening, then remove any screws the next am.

Good luck, you'll enjoy building this boat.

[Captain Pre-Capsize]

I just went over to the 'ol Ace Hardware, dug deeply and came up with all the SS screws that I needed for my Arch Davis Sanddollar. As my first boat I countersunk the holes and then drove the screws home, coming back later to overcoat the screwhead with thickened epoxy to make a nice smooth skin.

This will make you groan... As a first timer I didn't have but one drill - a clunky Makita. So I would drill and countersink ten holes, take out the bit and replace it with the Phillips head driver. Then drive ten screws. Take out the Phillips head driver reinsert the countersinker, drill ten more holes, and so on and so on. Week after week. Bulkheads, chines, stringers, seat risers, deck framing, planking.

My skiff is a bit smaller than the Penobscot but there are still around 1,000 screws in 'er. :eek: And I loved every minute of it - really. It was as close as I'll get to a Zen experience!

[John B]

epoxy won't stick to wax.