I'm not a naval architectic, nor yacht designer
....I majored in physics, but took just enough engineering classes
to be "dangerous"
So, I leave the intricacies to the likes of Hinckley, Douglas, McCurdy and Rhodes, (all 3 of whose boats I've sailed offshore), Dashew, Perry, etc....
But, without arguing over opinions, nor quibbling over the minute details, I have a few comments to make/agree with.....
Originally Posted by Dockhead
But don't confuse keel type with bottom type. They're different things.
A cruising boat needs some depth
in the forefoot and some profile to the hull
, which does cost some speed but gives a comfortable motion and better tracking. There is no contradiction between this and an efficient bulb keel. Our boat is great downwind -- easily driven yet tracks like a freight train. The autopilot
easily deals with following seas.
Originally Posted by s/v Jedi
When you design a fin keel you end up with more draft
. Dashew had a problem with that because he wanted the Sundeers to be able to sail shallow areas too. This forced him to enlarge the rudder (something he wanted anyway for reasons of maneuvering under power) so that the rudder plays a bigger role in tracking and preventing leeway.
While I agree with the above points, they are specific comments on the general fact that vessel / yacht keel design is not done in a vacuum.....
The entire hull
, keel, and rudder designs/shapes/lengths/depths/etc. are designed and engineered together.....it is not wise (nor likely) for any vessel designer
to make arbitrary descisions on one aspect of the underwater design (such wanting shoal draft), without engineering/designing the entire vessel for this goal.....
And, therefore, while it is fun to discuss the various pluses and minuses of different designs, we should all keep in mind that most of us are not naval architectics nor yacht designers.....and while I (and many of you, as well) do understand there are many variables (some sublte and some blatant) which affect a particular yacht's performance, etc. perhaps blanket statements of opinion on a public forum need to be highlighted as such, and not factual......
(Gosh, that's a weird sentence!!!)
What, I'm trying to say is that my opinion agrees with some others opinions here.......
In my opinion, a well designed fin keel / spade rudder sailboat is my favorite for offshore
sailing, no question in my mind (whether a Hinckley I sailed on for years 30+ yrs ago, a Sundeer which I've always loved, or my current
Gerry Douglas designed 47' sloop
But, others have different opinions, and they are entitled to them.....even if they're wrong....
Oh, and my spade rudder (only 6" shorter than my fin/wing keel) is designed / built similarly.....its bottom 1/3 is designed to break away in the event of a catostrophic impact......
Originally Posted by s/v Jedi
It also has an engineered weak point so that you are left with 2/3rd of the surface area if something needs to break during a grounding.
What I try to say is that a spade rudder can be made just as strong as a skeg hung rudder.
And, I couldn't agree more about a spade rudder being made just as strong as a skeg-hung rudder.....
I'm going to try to attach 2 photos here.....
The first is my boat in the slings showing the underwater design, 6' draft
fin/wing keel, and spade rudder.....(~9700 lbs lead keel)
The second is a sistership, showing the exact same hull design and rudder, although this one was the deep draft 8' draft fin keel....(a few hundred lbs. less ballast, but deeper)
(I spoke with the designer, Gerry Douglas, a year or so after I bought my boat.....and he informed me that unless I was racing
hard to windward, I'd never notice any difference in performance at all, and even then the 8' deep draft version would only have a slight advantage in keeping from being pushed leeward, but no actual improvement in pointing ability.....)
I hope some appreciate my contribution here....