ISO 12215-9:2012 pdf download – Small craft — Hull construction and scantlings — Part 9: Sailing craft appendages.
B.5.5 “Established practice” recommendations for installation of bolted keels and bolt tightening
Before installing, it should be checked that the nut can freely run down the thread without hanging up (snagging).
When installing, it should be ensured that the keel and hull mate correctly. This usually requires the use of an intermediate layer of gasketing material or oinIing compound (for further details, see D.4.7).
When tightening, a two stage process is recommended:
a) first, tighten to ‘snug 1k, i.e. a full effort of a person with the appropnately sized wrench:
b) then, If the pre-stressing torque is greater than snug fit (to be tested by a torque wrench). bnng up to torque with a torque wrench.
When re-installing, the same check as above should be made, replacing or adjusting screws or nuts when worn.
Bolt threads may need to be cleaned up with a die or a thread correcting tool if they have been highly loaded orgalled
A fncbon washer should be added above the backing plate recommended in Table D.2.
The nuts should be blocked with a wing washer, counter nut, gluing compound, punch mark, gel coat or laminate, etc. These methods may increase the nut friction (K coefficient without grease raised from O,Z2 to 025103) and the tightening torque for the same preload.
B.6 “Established practice” for welds on metal-fabricated keels
The production of a fabricated keel or other components with restricted access may require the use of slot and plug welds.
NOTE A &ot weld is a slot with a filet weld around its boundary; a pJug weed is a slot completely filed with welded metal.
Instances of poor performance under fatigue-inducing loads suggest that consideration should be given to replacing these by a continuous weld (I.e. placing a plating seam over a flanged internal stiffener and welding along the entire seam: see Figure B,1) or by evaluating the proposed configuration by calculation and inspection (see Annex F). This Is particularly Important at the root of the fin where stresses are higher and close to other components such as the canting keel trunnion. In general, slot welds are preferable to plug welds, and the latter are not allowed in high stress areas. For the most critical welds on keels, the use of backing plate and, possibly, grinding of Ihe weld is also recommended to improve fatigue life (see Table F.2).
Requirements on weld quality are not within the scope of this annex, but It is highly recommended that the quality of the welds of a fabricated keel be monitored. For welds on steel keels, the applicable Inlemational Standard is ISO 5817. It defines several levels of quality: B, Stringent; C, Intermediate; and D, Moderate, The difference between qualities C and B is mainly the amount and size of porosity and other minor imperfections. No surface cracks, lack of fusion or penetration are permitted. More imperfections are allowed by 0.
Level C Is the minimal recommended level, For critical welded joints — for example, those on the root of deep sailboat keels, and particularly slot welds — quality level B is recommended. For the same type of joints it is also recommended that a specific non-destructive testing such as radiographic. ultrasonic or magnetic induction, as relevant, be applied.
— LF, between the ends of a simply supported floor, as in Figure C.1 C). It is however important that shear transmissaon into the side shell is achieved and that the floor end depth should not terminate so as to give negligible floor web area combined with near horizontal side shell as shown In Figure C.1 C). In Figure C,1 d) the angle of the plating allows a non-thin ending and a good vertical load transfer.
Thus there is some room for interpretation of the defiition of the length of floors. ISO 12215-5:2008. 9.2 and ISO 12215-6 may also be used for determination of LF. However, ISO 12215-6:2008, 6.4.3 (Egg-box grid) is too crude for application to keel grids and should not be used. A grdlage analysis is recommended.