Leeway

[fisherman]

My antique rowing oyster dredging boat, 15ft, long shallow keel. Makes better upwind on port tack than stbd: this may be due to a slight bend in the keel, or a slight disparity in the hull from a long ago collision seemingly, she is 2in wider on the stbd side. Or both.
Made me think, what if a drop keel was designed to be steered, so maintaining the sail aspect while shoving the boat to windward?

I am aware of other options, like a detachable leeboard that a friend uses, slots into a rowlock hole. My boat tends to hold course while upright, better since I added 20mm to the keel which adds a square foot to it, but slides away when over on its ear. My ultimate solution if I wanted performance would be two drop keels, in the turn of each bilge.
The boat isn't designed to perform under sail, it's for fun.


a patent:
EP0232252B1 - A steerable keel - Google Patents

 

[neil_s]

Lee boards sound like the easiest way - you could fit different angle packers to the hull on each side to give you improved 'lift' to windward on starboard. Trim tabs on keels was tried back in the 70's ! I think a lot of more modern boats also sail best while upright.

 

[Daydream believer]

For the fixed keel types there was the trim tab attached to the aft end of the keel to aid upwind performance. Not sure if it was banned outright or penalised so much as not to be worthwhile. First seen on Americas Cup boats I think. But I am not totally sure.

What might be of interest to those with keels that are floppy in the box is a method used on dinghies. It appeared in the Amateur Yacht Research papers many years ago. Often referred to as a gybing centreboard
The idea was to let the dagger board rotate slightly depending on the tack upwind.

The back of the board would be a tight fit in the box (just add a couple of wooden strips each side) & the leading part much thinner.
Thus, going upwind the front would move over to windward giving a slight angle.

There were 2 schools of thought.
These depended on whether the dinghy had chines- like a Hornet- or rounded hull- like a 505. One would have a thicker front so the back dropped away a bit. This made less stopping power but still helped leaway. The other, as already described, made more drag, but pushed the boat upwind better. I think that was the option for rounded hulls with less inherent grip in the water


The OP may have the option to add vertical strips to the side of the keel where it fits the box in the down position to give it this twist. I am sure that he can look up the info on the AYR site & study first

 

[MisterBaxter]

The designer Phil Bolger designed a lot of boats with leeboards, his books have lots of useful construction detailing if you were thinking of adding them. He wrote that although it's tempting to toe them in or shape them or both to get lift to windward, it's very easy to overdo it and lose more in drag than you gain in reduced leeway. A degree or two of toe-in is about as far as he recommended going.

 

[fisherman]

The designer Phil Bolger designed a lot of boats with leeboards, his books have lots of useful construction detailing if you were thinking of adding them. He wrote that although it's tempting to toe them in or shape them or both to get lift to windward, it's very easy to overdo it and lose more in drag than you gain in reduced leeway. A degree or two of toe-in is about as far as he recommended going.

Yes I can see that. If the leeway could be reduced to zero no additional drag hopefully. Not driving the boat to windward, not allowing it to slip to leeward.
I'm not about to start chopping this eighty year old up to fit a drop keel. It's a rowing boat after all, which sails quite well. I point as high as a Wayfarer but don't make the same course. Downwind I do as well as eg a Bosun or similar.

 

[Daydream believer]

I point as high as a Wayfarer but don't make the same course.

Then perhaps you should concentrate less on pointing & more on speed, by easing off a bit.

 

[johnalison]

I think some bilge keels had a toe-in for a similar reason, but not having ever owned one I can't be sure.

 

[fisherman]

Then perhaps you should concentrate less on pointing & more on speed, by easing off a bit.

yes always a balancing act.
Looking to get a nav app to show me cog etc.........
I've had over 5kts downwind but gybes are a bit squeaky.......what are those strings threaded through the mainsail just above the boom for?

 

[Daydream believer]

.....what are those strings threaded through the mainsail just above the boom for?

The ties can be used to take some of the shape out of the sail to flatten it a little in windy weather.
If they are up above the boom a fair distance & opposite luff & leech cringles, then they can be used to gather in sail when the reef is applied. This is achieved by tying the cords together under the boom with reef knots. However, one should make sure that the principle load is carried between luff & leech as one might place undue load at a point not designed to take excessive load.
To be honest, if you do not really understand how they work, it may be better to leave well alone, until someone with practical knowledge can actually show you.

 

[LittleSister]

Made me think, what if a drop keel was designed to be steered, so maintaining the sail aspect while shoving the boat to windward?

You mean, like a rudder?

More generally, I think you're overthinking it. (I know, 'cos I do that!) Your boat will inevitably make a bit of leeway, whatever you do, so a central keel or plate along the boat longitudinal centreline will in fact present an angle to the flow practice and generate lift to windward. It's what it's for.

Many thousands of yacht designers and others have wrestled with the issues, and come to the conclusion that for practical purposes in the vast majority of boats, a keel or plate aligned along the centreline of the boat does the job well and avoids the various constructional and operational complications and disadvantages of other arrangements.

If you can keep your keel reasonably thin and make it a hydrofoil/aerofoil shape (like an aircraft wing - standard sections for these available online) - rounded front, widening to max thickness about 1/4 back from leading edge, tapering to near nothing, but trailing edge finished with a v narrow flat - it will maximise its effectiveness, but a flat plate/board section with rounded leading and trailing edges will do the job.

 

[KevinV]

It sounds to me like a case of "don't start from here" - you're trying to make a rowing boat behave like a sailing boat. Just accept that it's a rowing boat with auxiliary sail(s) - it may not point well, but surely it beats rowing any day

 

[B27]

Some centreboard dinghies have what is known as a 'gybing centreboard'.
The centreboard is thicker at the back where it sits in the plate case, so going up wind, the leading edge is lifted to windward.
The net effect is that the hull runs true upwhind, which has the side effect of putting the rudder in the fallout from the centreboard.

Marginal gains in some classes might be a fair summary?

 

[Fr J Hackett]

Think about two lifting boards as far back as you can get them, either side of the rudder should be ideal.

 

[William_H]

The ties can be used to take some of the shape out of the sail to flatten it a little in windy weather.
If they are up above the boom a fair distance & opposite luff & leech cringles, then they can be used to gather in sail when the reef is applied. This is achieved by tying the cords together under the boom with reef knots. However, one should make sure that the principle load is carried between luff & leech as one might place undue load at a point not designed to take excessive load.
To be honest, if you do not really understand how they work, it may be better to leave well alone, until someone with practical knowledge can actually show you.

Yes I agree. Actually reefing a dinghy can make the difference from sail in strong winds that is terrifying to reasonable. Reittering what has been said because it is important the sail when reefed is stretched between the clew eyelet (at back down to boom end) and tack eyelet at the mast. Without other facilities it is easy to fit a rope through the tack eyelet down around the boom at gooseneck then back to the eyelet and around the mast to bed the eyelet in tight to the corner boom to mast. Then do similar to tie the clew eyelet down to the boom back to the eyelet then out to the end of the boom (really tight stretching the foot of the sail flat.)
Having done that you will see that the bits of string attached to the sail along a line between the reefing eyelets are to bunch the bunt of spare sail up against the boom. Do not allow those ties to take any load sail to boom. That will distort the shape and rip the sail.
Try the reefing (obviously before departure) you will find it makes sailing very relaxed if a bit slower in gentle winds. if you really like a reef in you may want to set up with remote ropes so you can reef while out there like a big boat. ol'will