scarf joint the best?

[tburris]

I have two 1 1/2 inch thick by 24 inch wide by 12 feet long VG DF and would like to join them to get the length for my keel. Is the scarf joint the best for keel? Im thinking of the stress of the ballast. Is 5200 strong enough to hold the joint?

Ted

[ssor]

Oh that I could draw a sketch of the joint. Scarfed, yes but at each end turn the scarf back on its self to support the ends of the scarf. So that the ends don't run out but are supported by the wood . It needs to look like a check mark at each end.

[tburris]

WOW that sounds difficult to cut. what do you call this joint and I will look it up on the net

[Beowolf]

I like the "check mark" idea, but would it be just as effective to square them off instead? I'm thinking of something about 1/8 to 1/16 in deep, just enough to give the pieces a square surface to register against. It seems to me that it would be a tad easier to make. Not sure about how much strength you would lose. Hope someone else can weigh in on that one.

Jeff

[seayou77]

Nibbed scarf! 5200 requires some thickness. A tight scarf might mean a dry glue joint.

[ssor]

Feature a long scarf two or three or four times the width of the planks, about two inches from the edge of the plank at each end of the scarf reverse the cut and intersect the long scarf cut at a 90 degree angle. When the planks are joined the ends will "lock" into the reverse notches. This type of joint is found in many timber assemblies. There is of course no lateral strength in this joint so that either drifts or cheeks must be considered.

[Ross M]

I am with seayou77. Polyurethanes, wonderful as they are, seem mostly applicable when a significant (1/32" or better) glue line is anticipated and relative flexibility of the joint is desired.

When it comes to keel structures, I think you may be better served by epoxy or resourcinol.

If the geometry of your selected scarf is rough and/or poorly clamped, epoxy. If the fit is excellent and real clamping forces can be brought to bear, resourcinol.

YMMV, of course - a careful look at the Jim H's Faq/Index (http://www.woodenboat-ubb.com/ubb/ultimatebb.php?ubb=get_topic;f=1;t=008298) wouldn't hurt

Ross

[ 02-22-2005, 10:43 PM: Message edited by: Ross M ]

[Bob Smalser]

http://pic3.picturetrail.com/VOL12/1104763/2595357/70507451.jpg

[Cuyahoga Chuck]

A 1 ½" board cut for an 8:1 scarf will produce aplank that is 12" shorter than the component parts. Do you have that much to spare? For a keel I would go to a 10 or 12:1 scarf if the wood was available.
My scarfs, which are numerous because I use a lot of cast off lumber, are always glued with epoxy!
A lot of the fancy scarfs were developed for joints that had to be fastened with bolts or other metal fasteners. With epoxy you don't need anything exotic unless your rehabing the USS Constitution.
Charlie
Charlie

[Andreas Jordahl Rhude]

We use plane slope scarfs for end jointing material we make for the USS Constitution "Old Ironsides." Gluing up some white materials at the present time. Phenol resourcinol adhesive is used.

[ssor]

There is a need to clarify the orientation of these scarfs. They are laid out on the width of the timber not on the thickness. And yes the overall length of the finished assembly will be less than the sum of the lengths of individual planks. Just as when you splice a rope some of the length is consumed in making the splice.

[JimD]

Depending on the circumstance, a butt joint will be just as good and easier. And I wouldn't use 5200 on a keel but maybe that's just me.

[JimConlin]

I'm just not comfortable with a single joint, however well made.
VG DF is available in much longer lengths than 12', particularly in your part of the world. I find stuff over 20' in MA. I'd try first for full-length pieces.
If needed, I'd piece together 3/4" or even 1/2" stock, with epoxy. Might take 6-10 runs. Scarph shorter lengths if needed, but stagger the joints longitudinally and laterally.

[Dale R. Hamilton]

How about a simple stepped scarf 6 or 8" long, epoxied and through bolted.

[John Hastie]

I believe the strongest scarf joint I have ever seen is also one of the oldest. It is an Egyptian double dovetail scarf joint pulled tight by wedges.

I wish I coud find the resource where i saw this.

[StevenBauer]

Didn't Tom Jackson write a WB article about keel scarfs a few years ago? Use the online index.

Steven

[StevenBauer]

Here it is:

Jackson, Tom, author:/"Joinery Lessons from the Distant Past," 155:50

That's issue #155 page 50.

Steven

[Bob Smalser]

At the buck eighty a foot you can get airdried DF for in Oregon, a scarf joint wouldn't be one of my options for stock that thin.

Plenty of other uses for that 6/4 CVG DF in the boat.

And 24"-wide troubles me a bit. Woulda had to come from a 58" log to have 24" of VG heartwood. That's a big log for DF. You sure that stock is all heartwood and the rings don't change direction at the center of the board...meaning it was cut from just above the pith? DF sapwood rots as quick as any other sapwood and if the rings change direction in the middle of the board it's subject to cupping.

[ 02-23-2005, 11:08 AM: Message edited by: Bob Smalser ]

[htom]

I think you need to use those two boards somewhere else, too. What craft are you building that you're going to cut the keel out of a 6/4" x 24" x22' ? That seems to be to be either too thin or too wide for efficient use of the wood.

[George Roberts]

tburris ---

Where is the ballast relative to the scarf?

The board seems to be the wrong width for the length.

[Dan McCosh]

Assuming that the joint will be supported by the ballast, where the bending load is very light, I'd use a simple shiplap joint--each half made by cutting halfway through the board, then joining to a single thickness. It's relatively weak in bending, but quite good in sheer. It's very easy to do on large pieces. Also--use epoxy.

[tburris]

well thanks for all the replies. it was available and I bought right wrong or indifferent Im going to make it work. the final size will be about 19 feet ranging from 18 inches to 2 inches wide. the final size overall is that the keel will be 3 ib=nches thick when finised. Im going to strip up to the side of this first layer then Im going to cap it with a wider piece to make a what will look like a rabet.

Ted

[StevenBauer]

Ted, dude, you can't just leave us hangin'! Let's hear some more about the project. What design, what designer, etc. Pictures?, drawings? smile.gif

Steven

[tburris]

allegra 24. Im attempting to build it out of wood. I only have one drawing that Im working off of since all of the other drawings deal with
c-flex. As you can see im in the process of trying to put a keel together along with the stem and the stern post. What im working on is just a part of the keel it will be a total of 3 inches thick when finished. I plan on using a keel cap to cover the stip/cold molding that i will be using. Then if all goes well I will have a ballast bolted to the that. Since I dont know all of the politically correct terms of boat building that is the best way I can describe it. If I succeed with putting this part of the keel on the forms I will have pics but right now I only have pics of the standing forms nothing to exciting. :rolleyes:

[ssor]

Ted, that changes our perceptions a little. rip the planks, scarf and stagger the joints, don't skimp on nails or glue(of whatever sort you decide to use) and let us know how it turns out.
C-flex is good if you plan to build in frp. Just substitute stripping for C-flex, maybe cold mold the hull.

[ 02-23-2005, 08:29 PM: Message edited by: ssor ]

[StevenBauer]

Thanks, Ted. Great boat. Looking forward to pics.

Steven

[tburris]

Now that I've got that cleared up, what about the glue? epoxy? 5200?

Ted

[JimConlin]

There are many ways to go wrong in building a boat- methods, materials, design for starters. SCrewing up any of these can kill you and your passengers. If you intend to transport souls across water, i'd recommend that you buy the plans for a well-designed boat. You will find a place to use the fir.

[tburris]

Excuse me but in several post on this site I was told that DOUG FIR would be suitable for the keel. if that isnt true please inform me of something else. I can change the top layer to a different wood if needed. Im building the stem and the stern post out of the same wood is this exceptable? At $6.50 a BF I would think that it was good enough. :confused:

Ted

[ssor]

Are you paying 6.50/BF for doug fir in Oregon? Are you getting kissed at the same time? :D
Seriously doug fir should be fine for the keel but the advise for getting proper plans should be heeded. Earier there was a thread from down Oklahoma way with a house carpenter making repairs on a large trawler and using house repair techniques. :eek:

[ 02-24-2005, 08:09 AM: Message edited by: ssor ]

[tburris]

no i wasnt kissed,but now i feel raped :mad: I went to several lumber yards and they all wanted the same thing and the stuff they were selling is green. I was going to laminate the whole thing but I didnt like the ideal of a bunch of joints. This is still possible, I was thinking of using the DF for the first layer below the floor then laminate some hard wood ( 2 inches worth) to the DF putting next to the ballast. the Df is going to be protected on the sides by the material from the hull, the inside piece I was planning on leave bare to breath. As far as the plans, the builder that I bought them from states that its is merly changing the skins as far as the method. The one Drawing that is for wood construction shows an outside ballast (which is what i want) and the C-flex has the ballast poured inside. If the first part of this keel doesnt workout its time to move on. I have read so many books it seems to me that there are as many ways to build a boat as there are builders. If it makes you feel better Im not in construction and Im not changing anything structurally on the boat Im following the plans to the best of my interpetation :eek:

Ted