Request for BOM information

Discussion in 'Boat Design' started by Stumble, Dec 24, 2012.

  1. Stumble
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    Stumble Senior Member

    Does anyone have, and would be willing to provide a list of the fasteners used in boats they have either built or designed? I would like to get an idea of the cost of the parts in a number of different potential materials (304, 316, Monel, and titanium).
     
  2. viking north
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    viking north VINLAND

    Greg not sure if this is exactly what you are looking for but in my past builds/rebuilds/repairs/conversions up to 36footers. I generally make use of 304 or 316 stainless fasteners: Screws always Robinson heads and in sizes from #6 x 1/2 in. and up. Both in countersink and pan heads but I do make ample use of stainless finishing washers. Nuts & bolts from 1/4 in. dia. x 1/2 long and up both in dia. and length but rarely more than 1/2 in. dia. by 6 in. long. Also countersink, pan and carriage head. most full thread unless specifically where shearing due to thread cut is likely. Generally I use a flat as well as a lock washer under each nut and in some cases where I really want to be sure use that same combo with a lock nut. I also make ample use of from 1/4 to 1/2 in. dia.threaded rod in the deck framing and tying the cabin/wheelhouse to the deck beams. I make ample use of air nailing and glue in my interior woodworking. Here 304 stainless #16 and #18 finishing nails(pins) are the weapons of choice from 1/2 to 2 in. in length. Generally a box of each running in 1/2 in. incriments in increasing length, Plus an additional box of 1 1/4 in. and most woodworkers will know why. :D. At close to $100 a box these get pricey however the 1/2, 1 1/2, and 2 in. lengths will generally get me thru two boats. Keel bolts usually 1/2, 5/8, or 3/4 in dia. by anywhere from 1 up to 4 feet long depending on the floor timber and keel dept. 316 stainless where there is no danger of water contact and monel otherwise. As for the numbers of each of the above fasteners,i've never kept count as i have always kept a good supply in my shops stock and i am both the stock and tool man with the keys. :) Something I highly recommend in any shop as fastener shrinkage is one of the biggest underestimated drivers of rising production cost and profit loss. I would think any shop with a production run of identical craft should after a few boats have a good handle on fastener numbers.

    A Yacht is not defined by the vessel but by the care and love of her owner --
     
    Last edited: Dec 24, 2012
  3. Stumble
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    Stumble Senior Member

    Viking to some extent that's exacally what I am looking for, but with the addition of how many of each size/type you use.

    The point of the exercise is to try and quantify how much the fasteners would cost for a specific boat, assuming the boat used either 304, 316, titanium, or some mix of the three. So I can have a real understanding of how much more it would cost to switch to a different material.
     
  4. viking north
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    viking north VINLAND

    Dam just lost my whole post -- Oh well lets try out the memory :). In the marine world of fasteners there's not a whole lot of choice if one wants quality. Other than monel verses stainless (verging on double the cost) the only other is stainless verses the marine family of bronz/brass. In the long run there is no great savings here. Actually in the sceme of things fasteners percentage wise of overall cost will not show any great savings regardless of what is used. Since fasteners are the mechanical glues that hold the machine together why not use the best. The key to savings in any build is in the organizational planning of good supply and labour. I.E. The JIT system does not lend itself to a one off or low production numbers. In all honesty I can't see fastener cost as a key to any great savings on a build and we all know the Titanic Story, thus should strive to use nothing but the best.

    A yacht is not defined by the vessel but by the care and love of her owner ---
     
  5. Stumble
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    Stumble Senior Member

    Viking,

    Since I sell titanium fasteners I would agree with you, use the best! As a practical matter it would help to have a price comparison for stainless vs titanium fasteners.

    So for instance if a $100,000 36' sailboat had $4,500 in stainless fasteners, and it would cost $5,000 to swap all the stainless for titanium, that could make a pretty good sales pitch to builders. I have asked them for this information, but they are pretty stingy when it comes to providing this information, so I was hoping some designers here, or people who have built boats, would be willing to provide it.
     
  6. pdwiley
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    pdwiley Senior Member

    Pretty much zero so far but I've been through 180+kg of welding wire and 50+kg of rods plus literally hundreds of cutting & grinding disks.

    I can't think, offhand, of more than a handful of fasteners on the weather decks and rigging that'll be needed. Inside, sure, likely 316 or 304 Robertson drive screws as per Viking. Might use Ti if price not a lot higher. I also use a lot of staples, both the 12.7mm size and the 6.3mm size and brads in my nail guns. Can't see those being made in Ti but if they were, I'd be interested.

    PDW
     
  7. PAR
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    PAR Yacht Designer/Builder

    I would think a simple multiplier would do for fasteners, rather then a specific list for an actual, application specific fastener count.

    The cheapest fasteners are mild steel and this is the base line, with galvanized being next on the list and about a 20% increase in cost over mild steel in small quantities. 304 stainless is about 270% over the base line and 316 is about 380%, with silicon bronze being about 690% over mild steel. The conversion process would seem fairly straight forward in this regard. These multipliers are retail pricing, but in the general ballpark.

    As an example; a hundred count box of #10 x 1", flathead wood screws, in mild steel is about $4.60, with galvanized being about $5.50, 304 stainless being about $12.40, 316 stainless about $17.40 and silicon bronze $31.80 per box.

    So what's a box of 100 flathead, 1", #10's, cost in titanium? With this price, you have a new multiplier for this material. Of course this is an overly simplistic view, particularly with alloys, but a general pricing guide could be derived based on compatible alloy comparisons.
     
  8. Stumble
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    Stumble Senior Member


    Thanks Par.

    This size and number titanium would be $47 a box, so if I did the math right, it comes out to 1020% of mild steel. Or roughly 2.7 times 316 stainless.

    But what does this mean to the cost of the boat? What percentage of the float away cost of a boat are the fasteners?
     
  9. viking north
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    viking north VINLAND

    There are two different cost factors here and the biggest one is not being presented. Thus far we have only considered comparison prices of the individual types of fasteners, I.E. a box of stainless verses a box of bronz/brass or titanium. The real kick in the *** financial burden is in stocking all the different sizes required. Example I ran a one off/repair/maintenance and modification type shop. Not a big operation by no means generally staffed by myself and at times one or two additional employees. I would estimate i stock about $1500 to $2000 in stainless fasteners. If I switched to titanium that would mean an investment of up to $5400 in fasteners alone. This is where you'll run into reluctance of builders to step up to titanium. Especially so since stainless generally fufills the requirements. Having said that if you walked into my shop and pointed out where titanium would outperform and overcome the weakness of stainless in certain areas of my build, you could supply in small quanities, continue to do so JIT, Titanium would then become more viable financially to include in my choice as a low volume special purpose fastener to overcome the negatives of stainless in certain areas of the vessel's construction. I would get the benifits of using titanium where it really is required without the 270% increase in my shops fasterner stocking cost. To a supplier this is the thin edge of the wedge commonly known as getting ones foot in the door. ;)

    Seasons Greetings All --Off to do family things --
     
  10. PAR
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    PAR Yacht Designer/Builder

    On a well documented build, you should have a fastener count. If not supplied by the plans, then roughly worked out after reviewing them completely. With this in hand, you make a fastener purchase. Piece mealing it a small lot at a time is painful and costly. A recent job I did required 3,500 bronze machine screws and bolts. I bought them all at once, from the same supplier, getting a slight discount for the volume and had a couple of hundred left over, as I over estimated a bit and made changes along the way that lessened the fasten count. Of course I now have about 150 #6 x1" flathead machine screws and their nuts, plus another lot of about 50 #10x2" flathead machine screws and their nuts to find a home for, but they'll get used eventually and they've already been paid for in the previous job. Welcome to the wonderful world of boat building.

    As far as a percentage of the build, well it's not much, particularly with some methods. A traditional lapstrake might have a considerably higher percentage, but still likely less then 4%. A recent small daysailor build had $1,500 in plywood, $500 in fabrics and goo, and maybe a couple hundred in fasteners. Once you factor in the sails, solid stock, paint, etc., the fasteners were just 2.3% of the build. On larger craft, I suspect this percentage will drop considerably. So, maybe you're onto something Stumble, as doubling the fastener cost really isn't a big hit on the total project outlay, though talking most builders into accepting this hit, in their narrow margins will be a challenge.
     
  11. Stumble
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    Stumble Senior Member

    Viking,

    There are three primary reasons to make the switch to titanium over stainless. Which depending on application could vary.

    1) it is completely non-corrosive in normal service. Which has applications in two ways. first for things that cannot be allowed to fail like chainplates, keel bolts, ect. Second is in applications where corrosion can be costly, but not mission critical. Here things like deck hardware, rub rails, where rust stains can lead to warranty repairs that are more costly than the increased price of the fasteners.

    2) it is much stronger than stainless. Grade 5 is roughly 5 times stronger than stainless. Which again has two major applications. A) where fasteners or parts are size restricted like life line stantions or when mounting to other hardware. By switching to titanium you can increase strength without increasing size. B) mission critical parts like chainplates, where additional strength can provide additional safety margins, or allow parts to be designed smaller and stronger.

    3) at about 1/2 the weight of stainless it is used for weight sensitive applications, like up a mast, or in performance designs where every pound saved is advetagious.

    Where is gets really fun is when you can combine multiples of these advantages. Given that titanium is roughly double the price (for the same size) and five times the strength (for the same size) it's pretty clear that titanium is actually cheaper for the same strength as stainless.

    As an example: We are working with a couple of mast designers of some fitting for example where the design spiral has looked like the following:

    1) first they switched the part size for size to titanium to save weight.
    2) then they realized the part was now five times the strength they needed, so they reduced the size by half. Resulting in a part about 2.5 times the strength and 1/4 the weight at the top of a mast.
    3) because the amount of material was reduced by 1/2 the price dropped by about 1/2 so the part priced was about the same as the stainless part it replaced.

    They accepted that there was more reserve strength they could have removed from an engineering standpoint, but when they held the parts in their hands they were too small. Intellectually they accepted the strength, but emotionally they weren't willing to accept a part 1/4 the size would have been acceptable.
     
  12. Stumble
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    Stumble Senior Member


    One of the builders I am talking to is considering making titanium fasteners a premium upgrade (this is on a performance trimaran).

    The other thing that crosses my mind is that it may simplify inventory. Since the same parts can be used both above and below the waterline and in corrosion prone areas, the need to stock both 304 and 316 may be minimized. Though I don't know if this would make a real difference.
     
  13. viking north
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    viking north VINLAND

    Greg education exactly the approach thats going to increase the use of the product. You'll get no argument from me of it's superiority. Possibly with Halifax Nova Scotia being selected as the winning bid location for the mega billion build of Canada"s new military ships we will see you product in ample supply here at a reasonable cost due to competition and demand. Right now I doubt if any of the fastener suppliers stock any thing in titanium. I could possibly get such but only on a pre paid special order and then cross my fingers on import dutys and taxes oh and a new scam by UPS handling fees. (a $10 cost per package this is after the fact and in addition to pre paying the freight.) I recall the bronz/brass, hot dip galvanize/zinc days when miracle fastener stainless was thru the roof. But as more manufacturers got into stainless the price became very competitive and use climbed. I suspect the same will happen with Titanium within 10yrs. or so. Meanwhile us small frys out here on the edges of the universe will just have to make the best of it and continue to listen to Rock & Roll on transistor radios :cool:
     
  14. pdwiley
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    pdwiley Senior Member

    I almost never use 304 if I can get 316 simply because of the inventory issues. I don't have to worry about what the leftover ones are.

    Like PAR I buy in bulk. Buying retail 100 screws at a time is an invitation to get ***** on price. Also the general markup is ridiculous; I get 80% discount buying from an industrial supplier in bulk. They're still making a profit.

    If you make Robertson drive screws, do everyone a favour and make sure the damn sockets don't round out. Some of the screws I've used are notoriously bad at doing this.

    PDW
     

  15. viking north
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    viking north VINLAND

    PWD -- You might think this crazy but not all square drive heads are Robertsons. The Robertsons drive was invented by a Canadian Furniture Manufacturer and used in Canadian industry since 1935. All attempts to export this unique patented fastener into the U.S. (Our biggest trading partener) was prevented by the fastener manufacturing lobby groups there and only after the patent ran out has this fastener drive type slowely become available and made in the U.S. Even todate it is still not as common as in the commonwealth countries. The Robinson is called a square head or square drive in the U.S. and as a result of poor standardization is often not quite the same sizing. Compounding this, Robinson/square head screws manufactured in Europe/Asia often suffer from the same faults as a result of manufacturing using metric sizing. Thus you can run into three very slightly different (example) #2 (RED) Robinsons drive sized square slots. Often this very slight mismatch causes tear outs and a guaranteed trip to hell. Presently in my shop i have two /three different sizes of #2 Robinsons drive bits from which I select the one which best matches the screw batch i am using.
     
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