Arran de 2 incidents separats ocorreguts al llarg dels darrers 12 mesos (en embarcacions J/80 de més de 15 anys), referents a la subjecció de la quilla, JBOATS (amb l'ajuda de diversos experts del sector) ha publicat una guia de millors pràctiques per la inspecció, el manteniment, i l'ús, adreçada als propietaris d'aquestes embarcacions.
Transcrivim a continuació les recomanacions publicades en l'Associació internacional de la classe J/80 respecte la inspecció de les quilles:
Inspect Your Keels UpdateFollowing two separate incidents in the past 12 months where 15+ year old J/80s suffered apparent keel stub failures, J Boats, with the help of several industry experts, is compiling a best practices inspection, maintenance and use guide for J/80 owners. The following is an excerpt of the draft document, specifically regarding inspection of the keel and keel floor area. We strongly urge all owners to read carefully the recommendations and to inspect their boats.INSPECTION FREQUENCYConsidering the typical high-frequency use seen by many J/80s, at a minimum, we recommend that J/80s be inspected on an annual basis and that a professional survey be done every five years.HOW TO INSPECT YOUR KEEL/KEEL FLOORS (For Owners and Surveyors)1. With your boat suspended from travel lift straps (OK) or braced in a cradle (best) or trailer (good), grab the keel at the bottom and forcefully rock it back and forth. This tip deflection test on a deep keel boat should create a small amount of flex over the span of the keel and sump (if solid fiberglass like the J/80), but there should otherwise be minimal movement from side to side. When you release the keel it should immediately return to position (and not continue to cycle). It is also important to have someone belowdecks to check for movement in the keel floor or bilge area, or any evidence that the sump is moving independently of the keel floors.2. Are there any visible signs of cracking on the hull at the front and back of keel? Check the leading edge and bottom of keel for any impact marks/dents, scrapes. The two go hand in hand with grounding or impact damage. 3. Is there any cracking at the sump/keel joint? A crack in the cosmetic wrap could indicate that the keel nuts have loosened and need to be re-torqued. A crack may also permit water to penetrate to the keel bolts and cause crevice corrosion over time particularly if in salt water. Keel nuts should be torqued according to ISO standards, which specify the setting based on bolt material and thickness. For example, a 316 stainless keel bolt has a torque setting of 125 ft lbs assuming clean threads. 4. Is there any cracking, no matter how small, along the radius of the hull to molded sump interface? This is the transition from the hull fairbody to the keel sump. If yes, then bottom paint/gel coat should be sanded back to identify depth of cracking. One should also inspect the corresponding area on the turn of the sump inside the boat and consider sanding back interior gelcoat to see if any damage to the glass (white crazing). The tip deflection test (#1) can help better identify whether the cracks are a result of flex or a different issue. 5. Pull up all floorboards and thoroughly clean and dry all bilge components. With flashlight and mirror check all keel floor to hull intersections, including all edges of tabbing for any cracking or debonding. The integrity of the molded keel sump relies primarily on the keel floors and their secure attachment. If the keel and sump have excess movement, it is likely that the tabbing of one or more keel floors is compromised in some way (i.e. the floor is floating free from the hull). If there is any sign of different color gelcoats or paint, it is likely the keel sump has been previously repaired. When in doubt, sand away any gelcoat, clean area with a solvent, and look for white spots in the laminate-- this may be a sign of delamination. Have a surveyor immediately inspect this area for structural integrity. 6. Carefully inspect the keel bolt nuts for signs of corrosion. Periodically have your yard back off the keel nuts (one at a time) and inspect for crevice corrosion on the keel bolts. This can also be checked with a magnet. 316 stainless steel is not magnetic but crevice corrosion changes the properties and the steel could become magnetic. 7. A surveyor will use other tools to check the area: the tap test- tapping with a phenolic hammer to sound out both the exterior and interior for voids or delamination as well as to check the integrity of the glass tabbing along the keel floors; a moisture meter for finding areas of elevated moisture; even thermal infrared imaging to check for any inner laminate damage that might not otherwise be visible to the naked eye (see www.inspectboat.com for sample thermography images). Structural Repair Considerations For J/80s, the owner and a certified SAMS (www.marinesurvey.org) surveyor or composites expert should (1) determine the extent of cracking, distortion, wetness or delamination and (2) if there is any evidence discovered in step #1 that indicates a potential problem, the surveyor should then conduct destructive or non-destructive testing and, depending on the results of the test, recommend a repair procedure that is carried out by a qualified repair facility. | 01 May 2009 | |