J/30 Class Association Forums J/30 Forum The Boat, Sails and Equipment Keel Depth Limit

Just a quick question on the keel depth. In repairing Presto's keel (# 436) the bottom template (I borrowed Bengt's templates) is at the very bottom (actually below) my keel end point. Plus my keel bottom is flat as a pancake.

What is the max depth of the keel?

And what is the best shape of the bottom of the keel?


Thanks for any and all comments.

John,

The class rules have the specifications for the keel dimensions. On the top menu, mouse over "Class" and click on "By-laws, Rules & Specification". Scroll down to the specifications section and you'll see the keel details. The bottom is supposed to be "Tip rounded to centerline depth of 20mm maximum below section V". That pretty much defines a radius of curvature for the bottom of the keel. You can download a pdf document on that page and print out the pages you want.

I templated the keel on Rhapsody with it described in Putting Rhapsody's Keel on a diet.

I'm thinking that every time they bounce our keels on the wood blocks the fairing tends to fracture. you definitely don't want to put too much of a point on the bottom.

Just curious-does anyone know if any keels for the 30 ever were built conforming to the template pattern? If so, given the amount of fairing compound and glass I had to add to my keel to bring it up to proper shape-isn't it likely that a template legal all lead keel would be substantially heavier than those that have to be built out to match the template?

Also-Bill, when you faired your keel, did you find it was too short? I know Bengt's and mine both had the bottom template below the bottom of the keel.

Steve,

The keel on Rhapsody was very fat and had to be planed down. My guess is the mold used to make the keels "grew" over time each time a keel was poured. I also templated to the minimum allowable keel width and shaved just a little bit more off the lead so the outer surface was a skim coat of fairing compound.

I did have to build up the bottom of the keel about 3/4" to get the proper extension below station V of the keel templates. I attribute that more to the times that the keel may have bottomed over the life of the boat. The keel was "short" fore and aft so I built up the leading edge with a batten and faired it in. The front corner near the bottom was really short, probably since that is the first place that hit whenever the boat grounded. My guess is whoever fixed that area over its life just rounded it off and called it a day.

I guess the keel on Rhapsody is lighter by some extent due to the lead shaved off, but probably insignificant compared to the hydrodynamic improvement gained by fairing it.

Best of both worlds would be added weight for righting moment and the hydrodynamic improvement from fairing.

Interesting that many keels are too fat (i.e. mold getting larger) but also short in depth as well as fore and aft (mold too small?).

John ... while it may look ugly ... in many cases typical ... just fill it out, shape it and you're good.

photo shows simple build out to run longer leading edge.