And, 8150lbs. assumes you have a pretty damn strong boat too, or else don’t forget that damage, over and above a spilled drink on the deck above. Remember, energy absorbed or caused on impact has to do with velocity, mass, deflections on impact, and a big assumption about the time interval of the impact. The two equations above make some effort to take this into account. The energy is absorbed by both masses involved in the impact. Look in most Civil or Heavy Construction Handbooks, the Navy has specs. and good refs. on pier designs and loadings, fenders and the like. You may want some protection at the two outer corners of your boat house, against errant boats much larger than your own.
The piles are only partially fixed some distance below the mud line, and you’ve given no dimesnions, then canti. up to the water elev. which may vary; there may be some framing support or bracing at approx. this elev., at least in one wall line direction; then there may be some support or bracing under the upper deck depending upon how you frame it, in two directions. Then you train your skipper to kiss the dock, and live with some amount of movement up on the roof deck. Sorry, no answers, just some food for thought.
