Hi,
Ok, now that I started this firestorm on the drum rudders, I think I have changed my mind from just one simple factor. It will make my lw hull too fat. I saw rob post in another thread that Solitarry's lw hull is only 400mm (15") wide. It seems like the smallest I could possibly make a hull with a drum would be 18", and more probably 24". For a 30' lw hull, that is just too fat, <sigh>. I only need the hull to be as wide as required to support the mast, so 400mm at most.
So, on to the backup plan!!
My main problem with the outside rudders is really the length and load on the rudder shaft, although I have never understood how to make kick up rudders compatible with non-tiller steering.
After looking at Todd's videos of his linked asymmetrical rudders, I can see how it could be modified to allow the rudders to lift vertically, for adjustable draft. I also think you could make the rudders cant back to balance the steering.
The brilliant thing about that system (apart from the asymmetrical rudders), is that your steering system is attached to the backing plate which is never in the water, and therefore does not have to kick up, so no matter what happens to the rudder, the steering stays undamaged.
The downside is that there is a horizontal shaft low above the waterline to support the bottom of the steering plate. I think I am probably more comfortable with streamlining that strut and letting it hit the water than I am with building it strong enough to be only supported from the top.
Anyway, this is what I am going to try to get put together on my plywood box proa. Now, if I can just get to it this summer!!
- Gardner
On Tue, Jun 15, 2010 at 11:06 AM, Mike Crawford <jmichael@gwi.net > wrote:
Carl,
Depending upon your priorities, nothing is wrong with the drum rudders. It's a very subjective matter.
<<What is the problem with the drum style for an ocean passage, given thats exactly what I plan to do>>
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If I were to purchase a monohull, I'd purchase an ETAP, because not only are they unsinkable, they can be actively sailed while full of water, and can even recover from a 90-degree knockdown while full of water.
Most monohull sailors don't think this is an important feature. Some reviews say that unsinkability is nice, but not worth the loss of interior space due to the foam-filled double hull.
Is it just a "nice" feature? For some, yes.
For me, it's a requirement for any boat I intend to sail more than a mile off the coast (I don't mind swimming longer distances, but my crew might, and the water temp in Maine can put some people out of commission pretty quickly). I'd say that unsinkability is like a seatbelt and airbag. You'll probably never need them. But if you do, and you don't have them, things can get pretty ugly.
But since people are accustomed to sailing very heavy boats that sink if there's a hole in them, unsinkability is seen by most as a novelty, not an important feature.
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Kick-up foils on multihulls are a similar nice feature to have that matters to some people and not to others.
But for me, if hitting a whale, sandbar, log, or submerged container could render your foils useless until you find a boatyard, or even worse, sink the boat, that could make for an ugly day.
I want to be comfortable with what might happen if my kick-up foils collide with whatever lies unseen beneath the water. I'd love for a grounding out to mean nothing more than cursing, retrieving my foil on it's line, setting it back in place, and sailing away.
Many people are more than happy to sail everywhere with tall daggerboards, and most never hit a thing. I've known a number of Corsair owners, and only one of them ever had issues with the daggerboard -- and he made the mistake of chartering the boat out to people who couldn't read charts, resulting in multiple repairs to the daggerboard and crash box.
Statistically, if you go with drum rudders in the hull, you'll probably be fine. Just as if, should you decide not to wear a seatbelt in a car, you'll also probably be fine.
To each his own.
I'd say that any harryproa on the water is a great thing, regardless of its foils, daggerboards, leeboards, mini-keels, and such.
- Mike
On 6/15/2010 10:16 AM, Omar Khayyam wrote:Mike, in your last post you said "And if you want to go fast, avoid steering balance issues, have an easy up/down system, and stay away from experimental designs, the drum is a good choice. Especially if you're not going to make an ocean passage."What is the problem with the drum style for an ocean passage, given thats exactly what I plan to do.Thanks,Carl.
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