[Rhodes22-list] UHMWPE Motor Mount

[Roger Pihlaja]

Joe,

I have a couple more recomendations re the replacement of the wood with UHMWPE on your motor mount.  UHMWPE is a relatively soft material.  So, to prevent the heads of the thru bolts from gouging into the plastic when you torque the bolts down, I recommend the use of SS fender washers under the heads of the bolts.  This will spread out the compression loads & prevent the bolt heads from being pulled into the plastic.  Another good practice would be to use SS nylock nuts instead of regular nuts & lock washers.  You see, there is quite a mismatch between the thermal expansion coefficients of stainless steel & UHMWPE.  Using nylock nuts will prevent things from loosening up as they thermal cycle.  My experience with nylock nuts is that they also resist loosening due to vibration much better than conventional nuts & lock washers as well, which could be significant on an outboard motor mount.

The devil is in the details, Joe.  I just don't want you to have any problems.

Roger Pihlaja
S/V Dynamic Equilibrium