Arto
Rudders are roughly NACA0012 section 400mm chord and 1m deep mounted on the centreline of the lw hull. In the video you can see the rudder inspection cap open as we left covers off after aligning both rudders. They have a chain and sprockets with about a 5:1 reduction from the helm. The two chains are not endless so it is possible to wind the chain off a sprocket if the helm is rotated too many turns - there is no stop. That is why we were tacking rather than shunting. Owner is currently considering gearboxes and shafts so rudders can rotate continuously.
The helm response was immediate and positive once moving over 4kts. There is a tendency to weather helm but hardly noticeable once moving. During the first couple of attempts to tack we got locked in irons for a few minutes just crabbing slowly sideways. From memory we had three goes at tacking before we resorted to motoring through the wind. With sails set properly and clean hulls it may be possible to tack but then it is a bi-direction boat so shunting should be the way to go once rudders are rotatable.
The lw bows are quite bluff. They lift a fair amount of water because they also have reverse rake. My impression is that they would dive if driven hard into the back of a wave and buried but you would need at least 3m waves and about 20kts of wind to drive hard enough. When beating or reaching the trim is almost level - maybe slight bow down. Wave impact in the 0.5 to 1m seas we encountered was not noticeable. The boat slowed a little a couple of times when we sailing on the reverse tack and the bluff section of the cabin was hitting the top of the occasional wave. There was no need to have anything secured in those conditions because the boat is near level most of the time. It was very relaxed sailing compared with the keel boats in the mid week races and we were doing similar speed.
The underdeck clearance along the lw hull is 1.2m. No prospect of water coming onto the deck in the light conditions we were in.
Rick
On 17/11/2011, at 8:33 PM, Arto Hakkarainen wrote:
Rob and RickThanks for the info. How is the rudder issue arranged? And on the video the lee bows seemed quite blunt so I was wondering if that is really the case or is it just the perspective to the camera?ArtoFrom: Rob Denney <harryproa@gmail.com>
To: harryproa@yahoogroups.com.au
Sent: Thursday, November 17, 2011 4:32 AM
Subject: Re: [harryproa] 18m Proa on Port Phillip
Many thanks. Looks good apart from the forest on the bottom!This is the first flat panel harry sailing. It was built by the owner who started with the standard Vis plans as a guide, with adjustments to suit his requirements and build method.I hope to be going for a sail as soon as the sails (sailmaker's dodgy measuring) and a few other problems are fixed.rob
On Wed, Nov 16, 2011 at 9:37 PM, Rick Willoughby <rickwill@bigpond.net.au> wrote:
RobYou may be interested in an update on the 18m proa down here.We ordered a perfect day for the first trial sail and were not disappointed. We had 8 to 15kts with most around 10kts. Here is the doppler wind image just after I got home:The 10 to 20kph was close to what we measured on the bay.Once we got over a few teething issues with rudders and sails we tracked southeast down the eastern shore pretty much on the wind for the south southwest but free enough to keep speed. The boat is still not bi-directional so this was on a reverse tack with wind coming in from the lee hull. We then turned west and sailed reasonably close on the wind. We tacked through about 110 degrees but could make 120 degrees with a single board down doing around 0.8X windspeed. It may be possible to pinch higher but the hull fouling is a bit of party pooper at this stage. Some fouling did wear off but it would take a lot more miles to get it clean. I will be diving before the next sail if I get invited out again.After tracking west we tacked and ran free to the east. The big cabin could not be coaxed through the wind under any conditions under sail so we had to start the motor to come about. I doubt there will be any problem shunting because the boat responds very well to the big under-hull rudders. On occasion when in irons we would start going backwards so it would have been wonderful if the rudders had full rotation.This is an image of the track:We did not take the boat over land but I did leave the GPS turned on when driving home. We did 31km at average of about 6kts. But there was a good deal of fiddling about. I am reasonably confident that clean hulls would give boatspeed of 1X windspeed with upwind shunts of around 120 degrees made good.This speed trace helps explain the track a bit more:We managed 17.6kph or say 9.5kts. This was reaching in about 10 to 12kts true with wind over the lw hull. The boat felt better however with wind over the ww hull but probably not faster with the amount of fouling.With the current limitation on sail adjustment I would not want to be out in wind over 15kts. The boom is still too high to get proper sail set. There is no way to flatten them. The linked photo shows the saggy set but this is with halyards hard up and main with a crudely rigged flattening reef. Sail set is fine for maximum power up to about 15kts.The linked video shows some different views on a couple of points of sailing:Overall it was an enjoyable day and gave plenty of opportunity and ideas for improvement.
Rick Willoughby
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