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-   -   Advice on Joining Two Slabs (https://www.woodworkingtalk.com/f5/advice-joining-two-slabs-214551/)

Labow 09-12-2019 11:47 PM

Advice on Joining Two Slabs
 
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Reference the attached picture. I'm planning on sandwiching a different type of wood between these two pieces to make a table top. The piece I'm adding between them will be around 3/4-1".

I'm guessing just gluing all of this together wouldn't be strong enough? Would people put a few butterflies across the joints after it's glued? Or something else? Thanks

John Smith_inFL 09-13-2019 09:10 AM

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LaBow - each time you change subjects with different posts,
it would be a good idea to give the history and all you know
about the wood that you are currently working with.
that way, we all can be on the same page for the most accurate feedback.

with those two slabs, please post all the particulars such as species, thickness,
when the tree was cut down, when were the slabs cut off, how long have
they been drying and under what conditions.
and - do you intend to leave the bark on or take it off. (that is another issue).

if we don't know that, you may receive the wrong information that could possibly
lead you down the road of frustration that you may never recover from.
(as noted in your other post about working with green wood).

as for adding the strip of a different wood between the two, . . . . .
since they are so closely book matched, I would get them to join
flawlessly first, just to see how they look. and make your decisions then.

ChiknNutz 09-13-2019 10:23 AM

Butterflies would work. If you want them more inconspicuous, you can route a couple of stopped channels in the back side of both pieces, then span the gap with rebar or even wood dowels. Bond the rods into the tracks with bondo or epoxy.

Labow 09-13-2019 04:58 PM

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Thanks for the replies. So, I don't actually have much information about the piece. I found this piece last winter, and it's been sitting in my backyard since. Not sure when it was cut down. I'm looking into moisture meters so that I can check and see where the pieces are at (if anyone has a recommendation send me a message).
I cut the larger piece into these two pieces earlier this week, and they've been in my garage. I was thinking about keeping the bark, but when I was cutting the piece I knocked off a couple of good size pieces of bark, so I'll be taking it off.
I'm fairly new to all this, and am still learning how to identify different species (I have another post about that), so I'm not sure what species it is. I'm attaching a picture of the piece as it was before I cut it. Maybe someone here can help with that.
As far as size, about 2.25" thick, and 2' +/- across.

I was thinking of putting a strip between them because to me it looks like once I straighten the sides that will be joining together the outer edges wont match up, so the strip could be shaped in any way to bring those two edges together. But yeah, I'll check and if they fit together I'll most likely just put them together without the strip. good point

Thanks for helping me to be more thorough with my posts John. More info is always better.

ChiknNutz...I do want it to be inconspicuous. I've done butterflies on the underside before. Any reason that wouldn't work?

John Smith_inFL 09-14-2019 10:33 AM

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since you are still in the planning stage and exploring
your options, make a separate paper tracing of the two pieces
and mark where the darker heartwood starts by
putting a push pin (or nail) to connect parts "A" to match.
rotate the bottom of the pattern to where points "B" and "C"
come together. that will give you the cut line to have a very
close Book Match that can be joined together with dowels, biscuits,
splines, or whatever you are comfortable with.
but - the problem that is often experienced in this type of project
is the warping, cupping, twisting and splitting. just like in a "cookie round"
if the wood has not properly cured or dried first.
this is just another option to put in your design process.

DrRobert 09-14-2019 11:10 AM

Dealing with this type of wood can be tricky. You've got a 1/2 cookie there, and because of that, you don't have the usual stress cracks and checks so common with them.

So IMO if the wood is thoroughly acclimated you should be ok. That said, once you get the faces jointed and matched up, I would not glue them right away, but rather let them sit for a few weeks just to make sure you haven't released some stress.

And you'll have to figure out a clamping strategy. ;-)

Minor discrepancy in grain matching can probably be address with removing more material from C until you get back to where the sapwood ring matches. I agree with John it will look better without the strip.

Tony B 09-14-2019 03:04 PM

The problem here is gluing end grain to end grain so the joint would have to be supported by dowels, steel pins or butterflies. Expansion/contraction should not be an issue in this particular case if the wood has stabilized. If you go the way of butterflies, I would use either a very light OR a very dark colored butterfly to contrast with the cookie. Show it off. The butterflies should be right through the top down to the bottom OR butterflies on both top and bottom, to equalize stress if completely through is not possible. If you really want a stripe running down the middle, you will have cross grain issues to resolve because you will be gluing end grain to the long grain of the stripe. Using dowels or steel pins you will have to slightly elongate through holes in the stripe to help resolve expansion/contraction issues. This would not be practical since we dont know the moisture content of either the cookies halves or the stripe. Even if they it is the same in all. I'm sure there are charts/graphs online somewhere that would give you the coefficient of expansion of both the cookie species and the stripe species. So, if it were me, I would scrap the strip idea altogether.

Best of luck in whatever you decide

Labow 09-23-2019 01:25 AM

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Thanks for the diagram and the advice John. I’ll give that a try. Hopefully then I could leave the strip out.
I ended up buying a moisture meter and these are at 35%, so I wont be doing anything right now. I may be sending some wood to a local kiln to be dried, so if I do these will be in there.
I guess since the piece looks like a butterfly, butterflies would be appropriate. Should the grain of the butterfly to be going a certain direction? I would assume it should go with the long direction of the butterfly?

John Smith_inFL 09-23-2019 08:47 AM

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there is no set rule for bowtie or butterfly splices.
normally, they go across the grain.
check youtube - hundreds of really nice examples for your inspiration.
one mistake people make is making the middle of the patch too thin.
there is also no set rule (that I know of) for the dimensions of the patch.
just not too thin of a "waist" compared to the "shoulders"
the object of the patch is to keep the two pieces together. too thin of a
waist "could" pull apart - and it also looks funky.
best of luck in your project !! (your design looks about right).


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