CP19 Center of Mass Location?

[JLaman]

With the discussion on another thread regarding securing boats to trailers and some partial analysis offered of boat/trailer/vehicle/roadway interaction, it occurred to me that what's missing in the discussion is a precise location of the boat center of mass.  Anybody know where the CM of a CP19 is?  Let's say bare boat -- no gear just to keep it simple. 

[skip1930]

Sure. I have several times placed a 10 inch long 2 x 4 on top of my two ton floor jack and lifted my CP-19 clean off the trailer for sever reasons.
One to paint the bottom, one to unbolt and move the whole single axle assembly further astern, and one to readjust the winch and vee block, and last to better fit the hull bunks and to hang the hull from the hull bunks and glue on on Keel Boot to the bottom of the flat keel.

A posted a picture of my boat just sitting on it's keel and was only supported by three of the four trailer rollers. She was rock steady.

Anyway, put the 10" long piece of 2 x 4 under the keel about where you think the center of mass is and jack. If the whole boat comes up even your done.
If not move the board a few inches either way.

I remember a photograph in Small Craft Adviser that a guy had of his CP-16 sitting on it's keel in his front lawn. Nothing holding it up 'cept the keel.

I have been to Pentwater, Mi and made a sales call on a fellow who needed a paint line. He had a dog that 'free ranged' all around the shop. The employees loved the dog.
The dog was on the cover of his company literature.

skip.

[JLaman]

Okay, we have 2 coordinates out of 3 then.  I assume that the boat is symmetrical about its longitudinal axis, so the CM is in that plane.  Then, as Skip points out, he located the position fore and aft when lifting it.  Now all we need is the vertical location, which is really key to the trailering question.  The 800# ballast is below the hull.  Then we've got about 1200# above the bottom of the hull, so it seems to me the CM would be somewhere above the bottom of the hull.  That would have been calculated by the designer for stability calculations, but who knows if it is available?

[brackish]

The designer or possibly Hutchins.  I'm guessing on the 23 (different designer, more rounded hull profile).  1350# of ballast and I'm guessing at least 5-600# of structural weight below the bunks, so maybe 60-70% of the total weight.  Additionally, the load in motion acts like the center of buoyancy is also a factor.  Inertia in cornering (like pressure on the sail) presses the hull against the bunk in that direction, kind of like the boat is trying to heel, and the weight below the CG and the keel guide, resists that force.

So much for the hip shot physics, it's a nice day, think I'll go for a sail.