Keel Shapes

Status
Not open for further replies.
Jan 22, 1999
62
Hunter 35 PENSACOLA, FL
Glenn,
While in the yard recently I was parked next to a Hunter Legend 35 that was in the process of having its keel shaped from a pattern provided by CompUKeel. After much discussion with us fellow shipyard experts and a few phone calls to CompUKeel he had decided on a 12% chord pattern.
CompUKeel had recommended an 8% chord as that would take the least shaping material.
A 12% chord to them seem to be an overkil as their 8% chord was close to what Hunter was using.
In fitting the 12% chord shape to the old Hunter keel it showed where there were many voids and lumps in the Hunter casting and the 8% chord shape would have a hard time in getting a smooth shape
Also the 12% chord was selected because the owner had read where NSAA had determined that this was the most efficient shape moving through water.
Once back in the water the owner claimed the HL35 had picked up a one knot increase in water speed on a point to the first mark.
Have you had any experience with keel shaping and the 12% chord selected for the HL35: and why was the the original HL35 keel cast in the 1988 time frame so "rough" ??
Appreciate your interest in the older Hunters.

BR
 

ghen

.
Mar 15, 2009
104
2 216 St. Augustine
BReach,

Chord thickness ratio is a single component in the matrix of lift and drag in foil design. You need to evaluate the reynolds numbers you are operating in, keel area, aspect ratio, pitching moment of the boat on and on. If it is a specialty boat sailing in particular waters even the kinemetic viscosity of the water is part of the study. It is a complete design study on its own. I have devoted a crazy amount of time with this study as it is so fascinating. My gut feel is that your friend got extremely lucky or the old keel shape was so far out it was useless. A full knot is a massive amount of boatspeed.

I can't say why the old keels were so rough. I think in part it may be the market became more discerning in later years and sailors demanded closer tolerances. I know since I have been there a keel would be rejected if overly flawed.
 
Status
Not open for further replies.