Newbie with a few questions

[dr_innovation]

Newbie here getting ready for a project to carve a turtle, looking for some advice.. .

 

My goal with this piece is a chain-saw carved life-sized 3D green-see turtle to be positioned on a large rock in the yard.  I've been waiting for an appropriate piece of wood since I wanted it life size its been hard to find.  I recently got (for free) a sufficiently large piece of red elm. (photo below).   It is green (2month from tree uprooting in wind)    round slab  about 37" long by 30" wide and varies in thickness from 8 to 6 inches.   From reading I've been looking for a half-log but since this came along I wanted to try.     My concern is that there is a crack at the core and I'm curious if I should try stabilize it before I carve or   deal with the crack after carving. 

The heartwood is more than 2ft across and nearly 3ft long so just right for the turtle. The longest crack is about 5" radially (maybe 10" from end of crack to end) and goes through the full piece. The crack is vertical in the image. There are 2-3 smaller (maybe 1" radially) small cracks as well -- the other visible radial elements are just edges from cutting casting shadows. There is at least 7" ring of solid heartwood with no visible cracks around the outside edge.    I don't mind the cracks in the surface, I'll work that into the "shell" design, but am worried that while carving or after a short while it will break apart into two pieces. 

 

I know wood continues to crack as it dries but lack experience with this type of piece.  This is 6-8" thick and almost all end-grain. I just don't know how much more it will crack radially over time and hence the risk there is in carving this into nice piece -- would I be wasting my time-energy on a doomed effort.  Even worse would be it breaking while carving or carving makeing it much worse.    I wanted to carve it in the next week or so (for anniversary gift) , not waiting years for it to cure. 

 

If it matters the final piece would be outside -- I was originally planning on a burn+oil finish but could use epoxy if that would help keep it together and could do epoxy before or after carving.   Epoxy is strong and I've seen it use in many slab tables,  but it would in the crack not be across the joint, so not clear it would stop it from spreading or add strength.  With epoxy I add  saw dust to help it match in color. 

 

I could also try to address the carack without wood joints or metal joints .      if its likely to crack apart while carving, I could chisel out and glue in some bowtie/butterfly type inserts in a few places (which again I can work into "shell design" and let that dry before I carve it).    Adding it before will be much more complex.    If its likely to be okay while carving, I can also add a bowtie or metal joint fastners, afterwards.     But  adding a bow or joint fastner tie it will not look as nice so I'd rather not do that if I can avoid it. 

 

So the questions

1) what is the risk this breaks in two while I'm carving

2) what is the risk carving without addressing crack makes the crack much worse

3) what is the risk after carving it breaks in two 

4) if the risk are high, do I patch with epoxy to match  or with some joint fastner?   Would a 5/8" corregated metal fastner be enough  (used it bottom of in tables that cracked over time) or do I need a bowtie. 

 

 

 

[carver83]

I'd just keep it simple with this and drill two or three holes straight through , smash some oak dowels and gorilla glue in ,try get slight angle if possible to make it harder for wood pull apart. Then carve the turtle let it split (I tend put carvings in full sun if  I see a problem split happening to speed it up) then just tap some scrap wood wedges in with load of gorilla glue then let dry then re-carve the fix.

[dr_innovation]

1 hour ago, carver83 said:

I'd just keep it simple with this and drill two or three holes straight through , smash some oak dowels and gorilla glue in ,try get slight angle if possible to make it harder for wood pull apart. Then carve the turtle let it split (I tend put carvings in full sun if  I see a problem split happening to speed it up) then just tap some scrap wood wedges in with load of gorilla glue then let dry then re-carve the fix.

Thanks.. I should have though of that   I guess I was stuck thinking in 2d.    Definitely simpler to drill and dowl than do than a bowtie inlay, and I have the 3D thickness to get a good angles on them.      And a few small  ellipses on the shell will be pretty easy to hide.   

 

[Ratman]

Pictures of progress please! [emoji16][emoji106]

[dr_innovation]

5 hours ago, Ratman said:

Pictures of progress please!

Sure.    Not sure of the etiquette here .. some of the boat forums I frequent do build threads, with pic/feedback along the way,   My reading here seem to be finding mostly just finished piece pics..    But since you asked for progress pics, I can post regularly along the carve.  If that is appropriate I'll do a separate thread on it.

 

But since this had a question and explicit suggestion. I'll post a pic here on that and then  comment how it seems during/after carving.   Here is Step 1:  securing the ends of the crack with dowels.  My  primary goal was, to stop the crack spreading while I carve.   I decided to use many smaller dowels  (3" each, .2" diameter,  6 dowels per side, so 12 total. I drilled them  mounted at different angles just before, at, and just beyond the visible end of the crack to "sew" it up and keep it from propagating .  I left the bigger section of the crack as it was --  I will deal with that after carving and a bit more drying.   I ended up using bamboo rather than oak since bamboo has better compressive/tensile strength and  I had them handy in the form of chopsticks 😉  The image shows one dowl after driving in and gluing and 5 in their holes.  I drilled about 3.25" so I could counter sink them a little bit. 

 

Edited May 25, 2022 by dr_innovation
scale/crop image

[carver83]

9 hours ago, dr_innovation said:

Sure.    Not sure of the etiquette here .. some of the boat forums I frequent do build threads, with pic/feedback along the way,   My reading here seem to be finding mostly just finished piece pics..    But since you asked for progress pics, I can post regularly along the carve.  If that is appropriate I'll do a separate thread on it.

 

But since this had a question and explicit suggestion. I'll post a pic here on that and then  comment how it seems during/after carving.   Here is Step 1:  securing the ends of the crack with dowels.  My  primary goal was, to stop the crack spreading while I carve.   I decided to use many smaller dowels  (3" each, .2" diameter,  6 dowels per side, so 12 total. I drilled them  mounted at different angles just before, at, and just beyond the visible end of the crack to "sew" it up and keep it from propagating .  I left the bigger section of the crack as it was --  I will deal with that after carving and a bit more drying.   I ended up using bamboo rather than oak since bamboo has better compressive/tensile strength and  I had them handy in the form of chopsticks 😉  The image shows one dowl after driving in and gluing and 5 in their holes.  I drilled about 3.25" so I could counter sink them a little bit. 

 

 

[carver83]

Just now, carver83 said:

 

This is what meant by straight thru, 13mm oak dowels + gorilla glue full width of slab👍

[dr_innovation]

4 hours ago, carver83 said:

This is what meant by straight thru, 13mm oak dowels + gorilla glue full width of slab👍

Well that would be nice but, I don't have a 36" drill bit and don't know anyone who does,  so that was not an option.  The biggest bit I have access to is 12"  long bit at 1/2" diam so if I see any issues with the crack growing maybe I'll use that and larger dowels at an even shallower angle than what I did above.  I will be adding wedges/glue to large section of crack after I carve and let it dry a little, so I view the smaller dowels as a temporary fix.  

 

The diagonal use of the dowel was what was not obvious to me so even though I misunderstood you thanks for the idea.  And this was  doable with standard tools.    The dowels are is well across the crack so to expand the crack will need to fracture the dowel. Different angles provide different directional support against the fracture. 

Edited May 26, 2022 by dr_innovation

[dr_innovation]

Follow up post (progress) on the how this has held up during carving.  Overall the majority of carving is done and only minimal spread. 😀

 

On the top, the crack had not seem to progressed at all.   However on the bottom, where it was larger,  it expanded a bit and develope a bit of cup cracking maybe because it could not progress linearly and so went along the ring to reduce the stress.  I'll probably add more dowels on bottom. 

 

Edited June 6, 2022 by dr_innovation