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Core Sound 20 Hull #102


wkisting

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The Cedar Key Small Boat Meet is always the first weekend in May.  It is very disorganized (on purpose).  Everyone gathers on the beach at Island Place Saturday morning.  We admire each other's boats and meet one another.  Then we sail around and admire one another's boats.  Then we gather on the beach at Atsina Otie (an island about a mile off shore) and admire one another's boats.  Then we sail around all afternoon, admiring the other boats.  The only organized activity is dinner (supper here in the south),  We gather back at the pavilion at Island place for thAt, put on by the West Coast Trailer Sailors.    It's the best gathering of all!

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If I recall, Wes, the only longish lengths of 3/4 X 1 1/2 that support the deck are the inwhales and carlins.  All the rest is a few feet here, a few feet there.  The only pieces of dimensional lumber I had to scarf were the inwhales and gunwhales.  Worth mentioning that I added extra framing under the seats and decks so I could ballroom-dance my 205lb without fear.

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The CS20 plans mention that the side stringers need to be "tapered to 1/8" from the bulkhead forward." Does that mean the taper should start BEFORE the bulkhead so that it is already down to 1/8" thick (continuous) from the bulkhead forward, or does the tapering START at the bulkhead (still at full 3/4") and taper forward to 1/8" at the end of the stringer? (Hope that made sense.)

Thanks Jeff... I couldn't imagine why I would need a 24' board for a 20' boat.  :)

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Oyster is correct. I ordered several sheets for my Garvey and he shipped them to me via common carrier. Since it was going to cost me $50 extra to have it delivered to the house, I met the driver at the local Wal-Mart parking lot and took delivery there. I saved a bunch of money ordering the wood thru them and getting it delivered that way.

The last bunch of wood was purchased from Graham as we were visiting Oyster and Graham last summer anyway.

Steve

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Well, I ended up placing an order from Boulter Plywood in MA because the prices were much better on the Okoume (which Southern Crown didn't have in stock anyway) and they were able to ship it out the same day (should arrive next Wednesday or Thursday).

FYI, I did some research and found out that the "HydroCore" Southern Crown carries is made of Gurjan (supplied by World Panel) and is heavier than Meranti/Hydrotek. If Okoume is 19 lbs., Hydrotek/Meranti will be about 24 lbs. and HydroCore/Gurjan will be about 28-29 lbs (Al at World Panel confirmed these numbers). I'm sure the CS20 could handle the extra weight fine, but I'm reluctant to add it if it isn't gaining any advantage.

Boulter had BS1088 Meranti and Okoume in stock, so I ordered Meranti for the bottom hull (for the better abrasion resistance) and Okoume for the rest. This way I'll only be adding about 30 lbs. to the design (compared to straight Okoume) and it will all be added down low, where the extra strength and superior rot-resistance of the Meranti will make me feel better. (I know, I know... there will probably never be a demonstrable advantage to using the Meranti, but still....)

Anyone have a good web link that shows how to scarf plywood? I've read up on this many times already, but should probably refresh my memory before I get started.

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If you'll go to Duckworks mag, and use their search, searching for scarfing plywood, you'll come up with a TON of references. Just do not be afraid of it- once you do one, you'll see it's a piece of cake to do. Once you learn how, a scarf in four sheets of ply should take you 20, 25 minutes max.

I doubt you'll even add 30 pound to the boat. You're only using 4 sheets for the hull bottom and not FULL sheets at that. 5 pounds per sheet difference in weight, means 20 pounds for four sheets, and those aren't full sheets, so at most you'll  be adding 18 pounds. Be careful in your filleting to not make them over sized and you'll gain your 18 pounds back easily.

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Thanks Charlie... the Duckworks articles were the ones I was thinking of. I lost all my old Bookmarks when I got a new laptop, so I'm "rediscovering" all this great boatbuilding info again.

Now I'm trying to track down good Fir or Pine or something else in my area for stringers, framing, etc. I've heard so many mixed things about the "Southern Yellow Pine" species, since the Longleaf variety is apparently a great boat building wood but others are not so ideal. As usual, the opinions seem to range from the extreme "you must use the super expensive stuff" to the ultra-practical "anything works as long as you coat it in epoxy." I wish I had a better knowledge of woods and lumber yards in my area... I knew lots of great places to get beautiful wood in Iowa, but the lumber situation in GA is all new to me.

Wes

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Wes, I'm nearby in Southern Tennessee near Chattanooga with grandchildren in Atlanta. 

I found a lot of 1 X fir at Lowes, and about every 20th piece was good enough.  I would just stop by and pick through what they had every time I was in the neighborhood.  Welcome to the South, the land of framing and deck lumber.

Doug

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Doug... is there a way to tell what is Fir at Home Depot or Lowes? I checked both places, but they list their wood as SYP ("southern yellow pine") and SPF ("spruce, pine, [or] fir"). Is there a way to identify for certain whether the wood is fir? Many of the other woods that may be thrown in the mix may not be suitable for boat-building. I haven't asked the salespeople because I fear they will simply say "Yeah, that's Fir" without actually knowing what kind of wood it is.

Wes

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What I found was at Lowes with the red oak (not suitable) and poplar and was labeled as fir.  They can be confusing, and nobody can tell me what "white wood" is (maybe kin to white fish?).  If you are not having luck, call the folks at Rockler or Highland Hardware (both good tool sources in Atlanta) and ask them where to look for wood.

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Quick question... Fumed Silica is a perfectly acceptable "gap filling" thickening agent for epoxy, right? I've fiberglassed many boats before, but this is my first time making epoxy fillets along the seams, and I'm assuming fumed silica is fine for that, but thought I better check.

I also have some very fine Maple wood flour for joints that will be finished bright (if any).

One other question: If I scarf the plywood panels together (instead of butt join) do I need fiberglass tape on either side of the seam, or will the scarf alone hold and bend until sheathing later?

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Yes- it's probably the strongest of the fillers. Really NOT needed in fillets- wood flour works very well there. If you do use it, glass it wet so you don't need to sand and if you do sand do it soonest- epoxy/silica gets HARD when it's cured a while. But it'll work just fine.

You can add silica to the mix for a smoother fillet and to lighten the color both. A very small percentage of silica makes for a smoother mix, but don't over do it. The wood flour you buy from WEST Sys has about 5% silica already mixed in by the way.

No, you don't need tape on the joint- a proper scarf joint is plenty strong. Besides, on outside hull panels you'll be glassing anyway in most cases.

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Thanks Charlie!

Is there any need to glass the interior of the CS20? If so, it might be easier to glass the panels before 3D assembly, no? Otherwise, perhaps I would just glass the floor and leave the spaces inside the seat compartments epoxy-only? What do you all recommend?

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I have the entire exterior glassed, including decks.  I also glassed the interior of the forepeak locker, in the belief that it might reduce damage in a collision with rocks, etc.  I know others who glassed the seats and floors to guard against abrasion (small children in crew).  I don't think anyone glasses the insides of lockers in general.  I once worried that my floorboards would wear on the floors (they do take a pounding when trailering on bumpy roads), but find they rest on the glass tape that joins cockpit sides to bottom anyway.  As far as I understand it, the only glass that is structural is the tape on the seams-- the rest is just for abrasion.

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Thanks Chris... I wondered about that too. I'll just add strategic 'glassing in high wear areas after the interior structure is assembled.

Anyone know how accurate the CS20 materials list is? I spec'd all the lumber, but I noticed it doesn't seem to list the stringers for the forward (curved) hull and those that span the 3/8" to 1/4" thick hull bottom transition... UNLESS those materials are included under other headings like the "Deck Framing" or "Seat Stringer" listings.

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Here's an absurd story... I found a source for clear Douglas Fir just about 5 miles from me, but it is sold as "C or better." They let me come look at their bins to see if they had what I need, and I found more than enough good wood to use. Here's the catch, they tell me I CAN'T "hand pick" the pieces if I actually buy it. (So what was the point of letting me look at it?) Of course, this means, if I actually order from them, they grab whatever is on the top of the bin... so it may have a few knots (though most of their wood was pretty clear) and it may be plain sawn or quarter sawn. I'm really annoyed... I guess they let me look at it so that I could know they had the stuff I need, but won't let me pick it so that I get the pleasure of playing the "mystery wood" game when I actually order. The alternative is to drive to Atlanta (about $50 in gas, and 6 hours round-trip) to another lumber yard that carries this stuff.

Anyway, how important is it that the wood for stringers, cleats, etc. on the CS20 be quarter sawn rather than plain sawn? I'm pretty confident from looking at their stock that I'll get clear Fir, but much of it will be plain sawn if I can't pick it myself.

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Ray, you would THINK I could specify specific stock to be "quarter sawn," but when I asked about that, they kept saying "We only sell it as C or better." I said, "Yes, but I'm willing to pay you a higher price if you will select the quarter sawn pieces." Apparently, they don't provide that service, though I can't imagine why... Instead, they said "MAYBE I could order you a load that is quarter-sawn." I can't imagine why they would place an order, though, if they could easily fill the measly 13 pieces I need from their generous stock.

I might just try talking to the owner and saying, "Look this is a special project, could you please help me out? All I need to do is select 13 pieces." In the meantime, I asked if they could get me a price-quote and time estimate on an "order" of quarter-sawn. I'm hoping when they look in to placing the order, someone will say, "Wait, this is stupid... we could fill this guy's order out of our current inventory."

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