Spurlock shimming method.

[JIMRPT@AOL.COM]

In a message dated 5/01/2001 10:58:09 AM, Larry T. wrote:

<<"I found that I could follow the crack with the angle aluminum even though
the crack was not straight.">>

This comment of Larry's leads me to make a few comments vis a vis Spurlock's 
shim system and shimming in general.

First..if there is a better shimming system/method on the market I am not 
aware of it. However it does have its limitations .....though most of those 
are limitations of 'operator' imagination rather than limitations of the 
system. I know about this
'operator limiting factor' from personal experience! :-)

 Can 'significant' crowning be acheived in the process of 
"shimming"?..........probably not...but 'significant' tension can be added to 
the crown in the process of shimming. The wider, or more numerous, the 
shim(s) installed the more prominent the added 'tension' will be. Consider 
the 'shimming' of two boards.... one shimmed without the board being 
wedged/propped/jacked up and one with said wedging/propping/jacking during 
the shimming process.

 A board shimmed while 'flat' will have little or no added tension from the 
shimming process and may have 'less' tension when the shimming is completed. 
Think about it..if the crack is widened on an unsupported board is the crack 
going to 'tend' to be moved down during the widening? If a shim is then added 
to the widened crack...... to what dimension is the shim fitted to? Will it 
be the cracks size when the board is at rest or the cracks size when the 
board is pressed down while pressure is applied to the shim to fit/glue it in 
the crack? Or will it be the size of the crack as widened with the board at 
rest?

 Conversely on a supported board..... a crack widened and shimmed before the 
support is removed will have more incidental tension in the boards 'at rest' 
state. This because the crack will have been widened while the board was 
under reverse, or crowning, tension from: wedging/propping/jacking. Does this 
count as much as "adding crown" to a board?.......no probably not...... but 
it 'should' be better than having an essentially 'flat' shim 
installed.......shouldn't it? ("flat" being defined as a shim installed 
without board support)

(I would think that these same general thoughts would apply to 
polyester/epoxy methods as well when those are functional and not "cosmetic" 
cracks, but I have no experience in that area.)

 Which is better a 'tensioned' shim or a 'flat' shim?

As for following curves while shimming...........if it works for you go for 
it but it might be better to install a straight shim instead. This applies 
when using the Spurlock system, of course. I have used Bills' system to 
install entire board sections/panels in S&S where the panel was infested with 
all those cute little curley-cue cracks/pressure ridges/separations, etc. 
Using the Spurlock system it is as easy to install a 1, or more, inch 
shim/insert as it is to install a 1/4 inch shim/insert.

As a result of the above I try to never shim an unsupported board, even for 
purely "cosmetic" cracks and I try to remove as much of the board as needful 
when shimming a functional problem.
But this is just my view.
Jim Bryant (FL)