Check the level before Cutting the Skins
Hi, all...
I was getting ready to cut the side deck skins today, and started thinking about the rigidity and shape of the hull...obviously for best performance we want as uniform a shape as we can get, and it suddenly struck me that the deck makes up quite a bit of rigidity! Another fellow I know has an identical Triton out in the yard on an identical bunk. His is of course assembled, making for much more weight up high, and on top of that the stick has been lowered for transport and secured to the pulpit, coachroof and pushpit. Reason would have it that his boat should be flexier than mine, as while some of my interior has been cut away I still have the majority of structural bulkheads in place. Wrong!!!
I have had occasion to A/B the two, and mine is floppy. Has to be the decks. There was almost nowhere you could step in a cored area that the deck didn't oilcan badly if you weigh 170 pounds like I do, or in places if you weigh 55 pounds like Junior!
If the hull is out of shape and I recore well, the hull is going to be forever locked in that distorted shape by the newly rigid and sound decks .
Point being, that if the boat isn't level, some distortion is going to happen in the hull from the weight on the jack pads...not on an old Pearson, huh? Guess again!
Bear in mind that the hull thickness is not near so huge as we roll up above the keel root, and gets much thinner(!) up by the deck/hull joint. Check out the pics from the deck removal at Tim Lackey's Triton Daysailor site!
So, armed with a long level and my smallest, lightest, most patient helper (who is also 7 years old) I set about to deal with it. The question comes to mind just what and where to trust on the boat. We set the level across the toerails up forward and found that the boat needed to come up almost an inch at the rail to make it right. Since I have the coamings off now, we laid the level across the cockpit sills and found the reading differed only slightly. Tried a shorter level across the lips of the cockpit locker openings and found it to concur. Further investigation showed that the Stbd. toe rail is in fact about 1/16" SHORTER than the one to port(!) and that accounted for the near total of the discrepancy.
Now, the question also begs as to just how swell the uniformity of the hull shape might or might not have been held at the time the deck went on...they really pumped these boats out, so who knows. I just didn't want to compound whatever problems may be there.
My boat is set up on a 6-pad bunk, and because of the number of people who are sometimes working at one time, I have a v-head jack under the bow and two extra jacks placed well aft to minimize the shimmy of the bunk and oilcanning (well, as much oilcanning as glass this heavy will do as it flexes) of the hull. I had a fair ways to go, so I patiently used all the screws (I found that the most significant pushes are from the aft) and cranked it upright in small and gentle increments. With the boat leaning, I was able to go ahead and loosen the pads I needed to tilt to until they really rattled and then a bit. Took forever. Started with the kid and the level up forward, then checked it aft.
I found a few interesting things. One was that no matter how uniformly I had worked, the boat was out of rack end-to-end by about a 1/4 bubble! Wasn't that way when I started. Hmmm.
I dropped all the pads but the v-head and the two aft jacks, then reset. Closer, but now the whole boat was tilting again! Squared it up one more time, then reset the pads. Real close. Right on. Now to make sure the pads were all bearing evenly...I have a drill for this, which is to drop and reset the center pads first, the bow (obviously with v-head in place) second, the stern last. As I backed off the stbd. center, I was informed that we weren't perfectly level anymore. But...the boat had leaned the OTHER WAY FROM THE SIDE I'D JUST BACKED OFF!
None of the pads were gorilla tight, mind you. One bow and one opposite stern were a bit tighter than the rest. That's all it took to make a "pressure wave" in the hull that did this! We went to the 3-point balance again, then brought up bow, center, stern, far stern. Whenever the bows were tight in this process I would slack and reset the v-head, as well. Went back thru again, Jr. watching the level with Jedi concentration. No movement. Rechecked at the bow, and if we allow for the unequal rail dimensions, we are off about 3/64! Not Bad! Just for grins, I got junior down out of the cockpit and then released the pressure evenly on all of the jack pads. The whole Triton will stand up on the keel blocking and the v-head! Reset the jacks again carefully and we went up to check the level fore and aft. Now, I fib not one bit here, with Jessica as my witness, not one bit of detectible change had occurred!
I also found a couple of other interesting things...when we started leveling, it was easy to push the boat up with the jackscrews, but as we got closer to dead level it became much harder. Also, perhaps very telling as to how much the hull does indeed flex, as you get nearly dead level, ALL the pads will rattle loose all of a sudden! I don't see how this can happen unless the whole hull shape shifts due to the weight all bearing straight down on the keel properly.
Anyway, I hope that this is all of some help and/or interest to anyone who is planning to recore or do any other structural/bulkhead work. As the thicknesses are pretty much identical between the two boats and the Ariel much smaller in surface area, I would think it would be less of a concern for Ariel/Commander...but still worth checking.
Dave