a rudder design question

[Birdseye]

They look pretty vertical to me compared to many.
Lead lower ballast is great and unusual these days providing a great ballast ratio.
Quite full forward sections as well, providing good buoyancy upwind compared to the fine entry/wide sterns that tend to dive when on the wind.

I think I'd be tempted to add a skeg.
Probably 50% of the depth of the rudder and 25% of the width.
If you glass in a 10 or 12 mm 316 plate with welded studs to the stub area in front of the rudder you could bolt on and try one without having to break through the hull. ( I hate holes in boats)

Changes to the rudder, in my view will have little effect other than the obvious, bigger area>more leverage>more turning moment, Smaller area>less leverage>less turning moment.

One other thought is, where are your rudder stops set?
If for example they are set at 35degrees you could try dropping it by 5 or 10 degrees.

I only thought of modding the rudder if I had to cut back at bit at the forward top end to allow for a skeg - a fin really since it wont be attached to the rudder itself. As it happens the hull area in front of the rudder is flat and about 10cm wide so ideal for through bolting a plate to hold the skeg.

The rudder stops will be about 35 deg either side - not easy to change because ( from meory) they are formed by an arc cut out of the thick stainless plate that holds the rudder shaft.

Having said all this, I am not sure that the issue is the boat so much as a geriatric me trying to race it single handed with half mile legs between marks. I will know much better when I start racing with crew outside the barrage beginning september. Certainly I am managing far better now than when I started.

 

[Greg Mamalis]

Anybody having the graph diagram "rpm versus bhp/torgue/specific consumption" for VOLVO PENTA KAD 43? I would much appreciate if you send to my email: grema1@otenet.gr Thanks n Regards

 

[Javelin]

In round the cans racing in cruisers you generally lose more time due to bad tacks, jybes and roundings than in straightline boat speed. Assuming of course you have half reasonable sails and sail settings.
Dinghy sailers who sail cruisers often struggle due to tacking/jybing too often and failing to factor in the extended time it takes to get 4000kg back up to speed compared to 150kg.
Have a dammed good reason to tack before you commit and be sure the tack will gain you at least five boat lengths, otherwise stick with it.
Remember the rudder is a break so when you tack, take it slow, use that 4tons of momentum to gain more height towards the windward mark.
Sorry if any of this is in sucking eggs territory.

 

[The Q]

I hundred percent agree with Javelins comments on tacking. You often see dinghy sailors who have hired a broads sailing cruiser tacking much too hard. When you've got something from half ton up to several tons, you sail the boat round a curve, taking the weight with you, only pushing the rudder over harder when close to head to wind,
Sharp tacks just kill boat speed.

 

[B27]

I hundred percent agree with Javelins comments on tacking. You often see dinghy sailors who have hired a broads sailing cruiser tacking much too hard. When you've got something from half ton up to several tons, you sail the boat round a curve, taking the weight with you, only pushing the rudder over harder when close to head to wind,
Sharp tacks just kill boat speed.

On flat water like the Broads, it pays to tack slowly as you can use minimal steering and use your momentum to gain ground up wind.
People do that sailing Enterprises on rivers.
On proper water, if you tack slowly, waves will stop the boat and you will lose ground, so you want to tack quicker.

A modern boat like the OP's does not have much resistance to turning, it does not have a deep V hull or a long keel, just a little skeg-ette in front the rudder. It will spin in a tight turn without losing much energy.

Time spent above closehauled is mostly just time when your sails are not producing any power.
The optimum rate of turn there depends on the boat and the ciircumstances.

 

[LittleSister]

Birdseye's reported problems with directional stability and reliability of tacking are likely to be amenable to improvement by means of sail and rig adjustments.

Some years ago one of the yachting mags (PBO, I think, perhaps YM) had a series where they put some highly experienced person (sailmaker?) on board a boat that was having some handling, tacking, speed or other issue, who then advised the owner how they could eliminate, or at least mitigate, that problem by adjusting the rig. Some of the reported results were quite dramatic, others I saw were at least a marginal improvement in what had been frustrating the owner.

In some cases it was just a matter of refining the owner's use of the sheets, halyards, kicking strap, mainsheet track, etc. More often, though, it might involve adjusting rig tension, changing mast rake, adding or moving a barber haul, having a sail recut to better fit the geometry of the boat (e.g genoa track positions, etc.).

if I were in Birdseye's deck shoes I would splash out on getting some advice on those lines before embarking on alterations to the hull.

Note that such 'improvements' to a rig are not just about making the boat 'better' in simply general terms, but about making it better suit the owner's needs. So, for example, one owner might have a full crew and want to get the maximum speed out of his/her boat, another might want to make it more easily manageable for single-handed cruising. In the former case the advice of a more experienced racing sailor, or even just a fresh pair of eyes from a different racing sailor, might do, but in the latter that might well be inappropriate - a racing sailor used to full crew might value, for example, the lively tracking that Birdseye finds a challenge, because they always have a dedicated helm fully concentrating on that task alone, and experience it differently anyway because they have crew sitting on the windward gunwhale keeping the boat more upright. So is what is required someone who can, most importantly, listen to the owner, and advise how their particular needs and aspirations can be better met

I wonder whether other owners of the same class of boat as Birdseye report the same issues. They may be the result of some 'problem' with the way his rig is set up, or they may be characteristics of the design which can be either emphasised or tempered by means of rig and sail adjustments. (Quite likely somewhere between those two possibilities.)

(I would emphasise that I am far from being any sort of expert on rig set up and sail trim, but I do know that these factors can be transformative.)

 

[LittleSister]

A modern boat like the OP's does not have much resistance to turning, it does not have a deep V hull or a long keel, just a little skeg-ette in front the rudder. It will spin in a tight turn without losing much energy.

Time spent above closehauled is mostly just time when your sails are not producing any power.
The optimum rate of turn there depends on the boat and the ciircumstances.

I agree that the optimum rate of turn depends on the boat and the ciircumstances, but think that one has to get the measure of the particular boat to know how, and how much, one adjusts one's approach to circumstances.

I disagree with the implication (perhaps not meant) that a sharper turn is always most desirable. Yes, Time spent above close-hauled is mostly just time when your sails are not producing any power', but that is not the only factor. In my previous heavyweight long-keeler sedate long curved tacks were what best suited. Yes, there was an extended period when the sails weren't drawing - bad, but on the upside during the whole of the time the sails weren't drawing the boat would still be carrying its way yards upwind, I was often effectively or actually single-handed and could pull in the other genoa sheet by hand, and cleat it off with the sail position ready to draw as soon as we were on the other tack, and not have to spend time grinding it gradually into position with the winch. On several occasions I beat much sportier boats with fuller crews short tacking up a river, They tacked faster and had a better slant on the wind, but I gained further to windward at each tack and didn't loose time in the first part of each leg grinding the foresail into the correct position.

Of course, such an extreme approach wouldn't suit (or even work with) a lightweight sporty fin-keeler, but it is a matter of degree. When B27 says 'A modern boat like the OP's does not have much resistance to turning, it does not have a deep V hull or a long keel, just a little skeg-ette in front the rudder. It will spin in a tight turn without losing much energy.', not all modern boats are the same. The key question is how much resistance to turning, and how tight a turn best suits that particular boat.

In any boat, a turn too turn too gently will be disadvantageous, and a turn too sharply will be disadvantageous. The issue is finding out what rate of turn best suits the particular boat, and in different conditions, and also what the available range is - what is so gentle or sharp that the bow won't successfully go through the wind.

 

[B27]

No intention to imply a faster turn is always better.
The optimum will vary from boat to boat, and with the conditions.
E.g. a Merlin with its deep bow will lose a lot of energy shoving the bow sideways compared to a topper where the flat bow offers next to no resistance to being turned.

Sailing on a river you have the added quirk that pinching or 'shooting' head to wind at the edge will usually be in less current.

Good points about trim etc,
Some boats you can tack using very little rudder, initiate the turn by easing the jib and heaving the main in, or by heeling the boat..

I sometimes sail a Laser, a boat with such a horrible rudder its use must be minimised.

 

[jwilson]

The solution could be to fit instead of an off the peg standard tillerpilot, a ram/linear drive that is permanently connected to the tiller with matching electronics. Then you have an autopilot that is absolutely instant on-off by one button press. Unusual but have seen this fitted on several tiller steered boats. A Sadler 290 is such a good sailing boat in many ways that I'd be very dubious indeed about messing with rudder construction and design.

 

[Birdseye]

The solution could be to fit instead of an off the peg standard tillerpilot, a ram/linear drive that is permanently connected to the tiller with matching electronics. Then you have an autopilot that is absolutely instant on-off by one button press. Unusual but have seen this fitted on several tiller steered boats. A Sadler 290 is such a good sailing boat in many ways that I'd be very dubious indeed about messing with rudder construction and design.

I have fond memories of the under deck hydraulic pilot on the Starlight I had.

Lots of useful comments here. The point about curving through the tack makes sense and mirrors what the designer has said to me. The weight of the boat ( 5 tonnes in 29ft) makes for momentum. I reckon Javelin has got it right when he says:

In round the cans racing in cruisers you generally lose more time due to bad tacks, jybes and roundings than in straightline boat speed. Assuming of course you have half reasonable sails and sail settings.
Dinghy sailers who sail cruisers often struggle due to tacking/jybing too often and failing to factor in the extended time it takes to get 4000kg back up to speed compared to 150kg.
Have a dammed good reason to tack before you commit and be sure the tack will gain you at least five boat lengths, otherwise stick with it.
Remember the rudder is a break so when you tack, take it slow, use that 4tons of momentum to gain more height towards the windward mark.
Sorry if any of this is in sucking eggs territory.

Anyway, another race tomorrow to try and adapt my old sailing brain to a new boat. It sailed beautifully out in the sea this weekend so I am increasingly sure that the issue is me rather than the boat.

Its good to have a challenge and if nothing else I am really enjoying it.

 

[dunedin]

Lots of useful comments here. The point about curving through the tack makes sense and mirrors what the designer has said to me. The weight of the boat ( 5 tonnes in 29ft) makes for momentum

A number of times you have said the main issue is coming out of tacks - and specifically round up too much when winching in the genoa, risking going aback.
There are three ways that racing boats are steered - with the rudder yes, but angle of heel and sail trim are also useful methods. Indeed lightweight race boats use these in preference to the rudder, which acts as a brake.
My worry about your rudder ideas is that exiting a tack the boat is going slowly - hence rudder and water balance less relevant than when going at speed.
That leaves angle of heel and sail trim.

Do you have a mainsheet traveler? Then presumably it is pulled tonwindwards when beating to get the main on the centreline?

On our boat, as stated previously, I drop the traveller before the tack - to save effort but also because this then pins the main in hard on the new tack, holding the bows close to the wind so can pull in jib quickly and with minimum effort.

With your issue I would do the opposite - either leave the traveller on the old windward / new windward side, or (more hassle) ease the mainsheet before the tack. This will make the boat tend to settle with the bows further off the wind, reducing the risk of going aback.
It will also reduce heel on the new tack, which again should help as heeling tends to make the boat luff up.

So perhaps try different mainsail trim during solo tacks?

 

[Birdseye]

Again lots of good comments.

Went racing today on a simple 3 leg course, the longest leg of half a mile being the windward one. Wind 5kn +/-. Water flat since we are inside the barrage and no currents at all.

The boat did really well, particularly to windward where it was pointing almost as well as the fin keelers. Not bad on the downwind legs either though the weak wind and the boats weight did tell. Only tacking cock up was when I got sandwiched between another boat rounding the mark to starboard ( he had right of way) and a large steel ferry / tripper boat on my port side. Cost me 100 yards.

She has a bridle arrangement for the mainsheet but no way can I operate this plus everything else single handed on such shortlegs. What you describe is what I did on my last boat fully crewed with legs often of a couple of miles, and a track directly in front of the wheel.

I consciously took Javelins advice about a more curved tack and that definitely worked better with no genoa issues except the one mentioned above.

No directional stability issues. The boat is still quick to turn but thats something for me to adjust to. I'm happy with the progress so far. Certainly trying to single hand short tacking in a race is a quick way of learning a new boat and upping your own game.