fixing keel on

i have just bought a 38 ft fin keel boat as a project. the boat had a prang that required new keel and rudder. the project had progressed to fixing the matrix and the internal structures and purchasing a new keel and rudder when i bought it. the boat is in a craddle the keel lying beside it. question i have is what is the best way to get the keel back on and insure that the keel is vertical and in line with the boat. this is important as boat will be raced.
cheers jon

 

With a laser like this http://www.amazon.com/DEWALT-DW087K-Self-Leveling-Horizontal-Vertical/dp/B000BK32EA/ref=pd_cp_hi_3

 

thanks i understand how you can make sure the keel is vertical to the land but i wonder how you insure that the hull is level, i.e the keel is at 90 degrees to hull?

 

Naturally you set the boat first..

ps. If that is difficult you can measure the deviation of the boat and set the keel accordingly.

 

Using a Laser level as suggested, you know you can get the keel level with the earth--line up the vertical Laser line with the trailing edge of the keel, which is usually better defined than the leading edge. On a boat this big, you will have to suspend the boat from slings, or set it on stands high enough, and in that position, check the levelness of the hull to the earth. You can pick a few reference points inside or in the cockpit to measure horizontal level both athwartships and fore/aft for trim. Hold the hull in that position. You can use a digital level here--make the boat level with the earth. So now both keel and boat are level with the earth. Slowly bring them together--either hull down onto the keel or keel up into the hull and mate them together.

Before tightening the keel bolts, take some triangulation measurements from the deck edge down to the keel. Pick two points on the hull edge that are identical but mirror images of each other port to starboard--these points will be the same distance back from the stem. With two tape measures, one from each of these points, measure down the girth of the hull and past the turn of the bilge. Go straight to two identical/mirror image points on the keel near the bottom of the trailing edge (hopefully your new keel is symmetric!). Pull the tape measures tight to remove any sag in the tapes. The measurements should be the same distance. If they are not, then the keel is canted too much toward the shorter side. Shift the bottom of the keel toward the longer side until the tape measures read exactly the same distance. Do this again at the leading edge of the keel. You can use the same hull/deck reference points or pick new ones. Mark the center of the keel leading edge with a marker. Measure down from the deck reference points to the mark, and again the tape measurements should be the same. This will assure that the keel is aligned on the same centerline as the hull. Keep checking trailing edge and leading edge measuremens until both pairs read the same dimensions respectively. When they do, tighten the keel bolts. Then check the tape measurements again, they should still read the same distances respectively.

In professional boat building, both custom and production builders will have a keel alignment jig that holds the keel and uses either screw jacks or hydraulic jacks to shift the keel one way or the other to make sure the keel is square to the hull. They always double-check with triangulation measurements as I describe above.

Good luck!

Eric

 

If you find it a lot of work to to level the boat...

You could just measure from same points along the sides at deck level as pointed out. In addition, a cardboard template can be made that would fit against keel and bottom equally on both sides which provides the angle relative to the bottom.
Between those two very precise methods (use both to double-check), you could easily locate the keel without the bother of levelling.
Fore and aft straightness is most important. That positioning can be checked with a tight string running from (touuching) two plumb (vertical strings with plumb bobs attached) lines at stem and stern. No levelling is required, just drop a plumb bob from centerline at transom and bow and run the longitudinal string so it touches both plumb strings equally. Just make sure you have a good line exactly on the centerline of the keel at both leading edge and trailing edge. The longitudinal string wants to be exactly paralell to both fore and aft vertical centerlines drawn on the keel.

 

thanks