Being the schipper on Henny's Blind Date video I will give you some background info, some answers and some opinions on the topics that were raised.
The reason these rudders were replaced by smaller rudders on the beams is that the construction was not solid enough. The rudder blades that point forward as you can see were not stabile at high speed. This was before I was involved. Rudolf can tell you all you need to know.
Now that the rudders are reinforced, the work pretty well, however we have some unfulfilled wishes.
When we made a strong construction, we sacrificed the safety measures. When the rudder blades hit the bottom something will break. Maybe the rudder will break from the leeward hull, leaving a big gap, I do not know. Sailing in unknown water is very risky. We have to stay close to Lelystad harbor.
We have not yet tried sailing with the rudder blades pulled up. Rudolf did this before the rudders were replaced. He said that there forces on the steering lines soon become too much, because the COE on the rudder blades gets too far behind the axis of rotation.
A second problem of sailing with the rudder blades (partly) pulled up is that the ship will turn it's nose into the wind, especially at low speeds shortly after shunting.
This is what also happened with the 2nd generation rudders that were placed on the beams.
Sailing up wind with the aft rudder straight, the Blind Date is pretty well balanced. We have not measured speed yet, to find the optimal angle for the aft rudder. In the video you can see me holding the aft rudder while someone else is steering with the front rudder.
I do this because we can not fix one rudder (clamp is broken). The clamp of the other rudder is kind of hard to release after the helmsman has accidentally used some force on the steering wheel. So with unexperienced Blind Date sailors I prefer hand held steering wheels.
In the meantime we are thinking about better ways to fix the rudder in the exact right position. Close to the rudder and independent of the rudder lines seems to be the best starting point for this detail.
Speaking of the rudder lines, there are some things that happened that are not on the video. The bearing of the steering wheel of one of the rudders broke loose. We sailed home using only one rudder. On the last shunt you can see me helping the boom to turn. We could not afford the ship turning into the wind.
Sailing with only one rudder felt like absolute poverty. You do not understand how all those monohulls manage to sail so well with only one rudder.
Even with 2 rudders we did not always shunt well. Henny made us look a little better than we were.
We have not sailed the Blind Date to it's limits yet. Probably not even close.
On the day of the video we had some showers blowing over with quite a lot of wind. We even sailed with 2 reefs for a while. Not even my socks got wet that day. But I know were to sit and walk by now.
Rudolf thinks the spraying of the rudders do slow the ship down quite a lot, especially in waves. I have not noticed much of that yet, however it is clear that spraying should be prevented when possible.
Action equals reaction: all the water that is thrown up will make the boat go down.
It feels like a contradiction to have these beautifully streamlined hulls and then use rudders that scoff at all the laws of hydrodynamics. Sorry Rob, we had to spoil your work of art!
It was an emergency.
I made drawings for a revolutionary proa rudder.
Very well streamlined, (almost) no spray, safe when hitting the ground and no lines other than the steering lines.
I will put drawings on the Files section of this Yahoo group.
It is really challenging to get the full speed potential of the Blind Date.
We know there must be more.
We will work on the rig in the months to come. (Winter for us).
I discussed the ballestron on this forum.
The rudders taught us to make small steps.
So we will probably improve all details before throwing it away.
>From all rig solutions that I have seen and drawn up to now, I like a schooner rig with masts on the beams best.
I hope that a better rig will solve the nose diving issue.
Rocker of the leeward hull, efficiency of the rig, rudders, all these things have to match and work together.
Lots to learn, many toys to play with.
Nol
--- In harryproa@yahoogroups.com.au, Ron Badley <sn1834@...> wrote:
>
> The boat looks great. Very comfortable, relaxed and certainly clips
> along. Interior looks better then I had imagined. All are good
> cruising traits.
>
> As far as the spray goes... look to float plane floats for
> inspiration. A good knuckle would do wonders.
>
> RonB.
>