Replies

1. 
   Westchester | May 22, 2011 07:35am | #1

   Wood Movement

   Mike - Don is correct but I would not let it discourage you from proceeding as indicated.  Use the correct joinery and correctly dried woods and go forward  -

   Many pieces are designed as you note with different species of woods,  plus there are too many factors with wood movement to worry about those issues - 

   SA

1. 
   1948mike | May 22, 2011 11:02am | #3

   I am tending to agree, I think that at times things can be over researched. Thanks for the reply.

2. 
   1948mike | May 22, 2011 11:00am | #2

   Thanks for the reply. I'll try to find the "shrinkulator".

3. 
   joinerswork | May 23, 2011 09:37am | #4

   mike,

   This has been standard procedure for hundreds of years.  While there may be a differential in shrinkage between your primary and secondary wooods, if both species are similarly dry, you ought not have any structural issues long term.  The worst thing that might happen would be cosmetic in nature- like a small split appearing alongside a dovetail, in the secondary (weaker, so it will appear there) wood's surface.  Since secondary wood is used because it isn't typically seen, potential cosmetic issues aren't a consideration.

   Ray

4. 
   oldusty | May 23, 2011 10:07am | #5

   Mike , With wood movement in mind when designing the species is not as important as the design.

                   regards    dusty

5. 
   DarinS | May 23, 2011 01:56pm | #6

   The Shrinkulator:   http://www.woodbin.com/calcs/shrinkulator.htm.  One caveat, you may need to cut and paste the link.

6. 
   SgianDubh | May 23, 2011 03:53pm | #7

   American white oak has shrinkage factors of 10.5% tangential (T) and 5.6% radially (R). Poplar, in comparison has shrinkage factors of 8.2%T and 4.6%R. The shrinkage factors are similar for both species. The shrinkage factors given relate to the amount of typical shrinkage to be expected in the shrinkage zone (SZ), ie between 30% moisture content (MC) and 0% MC.

   Your wood presumably is already dry at something probably between about 7-13% MC and in service it is likely it will hover between 7 and 13% MC. In this case a 24" wide panel in tangentially sawn oak at 7% MC at the time of construction will expand to approximately 24-1/4" if it reaches 13% MC. Similarly, the poplar, also 24" wide at construction and 7% MC, will expand to about 24-3/16". 

   In conclusion there shouldn't be a significant problem nor likelihood of splits developing if you mix these two species in one cabinet. I've done exactly what you propose on many occasions without problems, but I've always been careful to pick two species with similar shrinkage factors, and the oak and poplar you propose do have similar shrinkage factors as illustrated in the first pragraph. Slainte.    

7. 
   bones | May 24, 2011 08:58am | #8

   I've generally used poplar as a secondary wood.  By that I assume you mean like an interal wood not to be seen.  I work mostly in cherry and maple(drawers) and have used design and always allowed for movement where a crossgrain situation has occured.  Never had an issue.  I do acclimate my wood and don't bring stuff in and start cutting to final dimensions.  I mill and rest it, cut to close dimension and rest it, and then do the final cut.  I just assume that the medium I like to work in wood is gona move that's just the facts of life.  Only one bad experience which was a first project for me way way way back when when I did not understand that concept and had a split in a cradle I made for my son (who's in the army now)  Life is a good teacher.   Again I'd just allow for movement where you have those cross grain situation and not worry about it.  Somehting tells me those builders of yore did not have any puters to run moisture content calculations through and there's lots of pieces in museums that show they were ok.   Good luck. 

1. 
   DonStephan | May 26, 2011 09:00pm | #10

   Long ago I asked why modern woodworking articles suggested not using wide single boards for tabletops, cross grain construction,  et cetera, when we have pieces in museums with same.  Several responded that it was possible out of every 100 such pieces made 99 eventually became firewood because of significant warping, serious splitting, et cetera.  Don't know if that is why we have so few examples today of pieces that break the rules, but it seems possible.  Like you I try to allow for movement in cross grain situations.

8. 
   1948mike | May 25, 2011 07:36am | #9

   Thank you all, I thought that's how it worked.