Twin Asymmetrical daggerboards

[Ormonddude]

My Issue would be is this Major Modification going to be worth it I mean what do you expect to gain? .1-.2 knots? our boats will never be racers so its simply not worth all that effort IMHO.

[Crikey]

This is the mod section, and saying everything is perfect and should be left un-investigated sounds a bit luddish to me. It could well be that the engineered 'gybing' turns out to be perfect on either tack. But like the widely noticed variables in steering and fit and finish, there seems to me a good likelihood for some improvements in this area as well. The X is a different beast with its keel pinned at one end, and may well cant in a positive direction. The M, without any constraints other than a somewhat loose housing, could either be right on the money, or held by the water pressure in an inefficient orientation.
Raising or lowering it with any sort of way on, becomes problematic (M model) even in the stock condition so a second, or related mod may be in order.
Either way, until someone measures and tests, no one really knows!

I'd like to put this on my list for next year, and if I'm wrong I'll eat my hat and be the first to admit it!

Ross

[finding41]

Ok just for a bit more excitement. Check the side stabilizers/ wings on this Quant28! Now that would make any Mac sit up strait!
Here is a link. It's in German but you get the idea and then can use Google translate.
http://sailinganarchy.de/assets/images/ ... 28_Neu.pdf
If I had the extra $ sitting around. Well there would be wings on my 26D!
Edit: found a English linkhttp://www.quant-boats.com/documents/FlyerDSSE.pdf
2nd Edit; Patten application; http://www.quant-boats.com/documents/US20090283023.pdf

[mastreb]

I'm not advocating that people waste their time on pointless pursuits, but my determination of whether a pursuit is pointless is based on my understanding of reality, as expressed in mathematics and dynamics, and not in "what's been done before" or "what the experts who are invested in how things are done right now think". I've actually made rather a good living poking my finger in the eye of the status quo.

We sail MacGregors. These are the boats of "What if I could put a sailboat on a trailer?" and "How can I get a mast up and down routinely without it being a total pain in the ass?" and "Hey, let's use water for the keel, even though decades of people will tell us that won't work!" and "Wait, what if the rudder kicks up?" and "Hey, instead of 6000 lbs. of lead, let's just put an aircraft wing below and see if it reduces leeward slip!".

I'm sorry to rant, but if you're so invested in "traditional sailing" that the exploration of ideas is anathema to you, you bought the wrong damned boat.

[Ixneigh]

re wing stabilisers:
Oh NOW we're talking. that WILL work. And it would work on the Mac style hull.
I would...
Cant it up 10 degrees.
Make it a bit wider and definety shorter
place it just over the trailer wheel fender
Have it swing out into position and held there with line forward somewhere.
Make the bracket and base of wing insanely strong
Expect a good lifting force under power when the wing is folded back along the hull

Ok, so lets look at the drawbacks, \\ opinion\\
Drag. Probably need a computer to figure out just how much
With a stiffer boat, all of the Mac safety margins are gone. Upgrade rigging, chainplates, mast tangs.
localised strain on hull where wing attaches.
Probably not a big increase in speed but maybe in comfort.

re worthless exploration into crazy mods
What else we got to do when we aint sailing??? but talk about crazy stuff

Ix

[mastreb]

The side wings are very interesting. There is definitely going to be a sudden increase in drag when they hit the water. My guess is that with a close to optimal foil shape, you're talking about 10 lbs. of lift for every 1 lb. of drag, which means that a useful amount of lift for righting is going to generate 30 lbs. of back pull as soon as the wing touches the water. That's not by any means insurmountable, but it's enough to feel it happen.

Won't make the boat any less tender at the dock, but it would reduce heel by about 10% at speed. I'm pretty sure you'd want these well aft of the center of effort, however, so that the induced drag doesn't impact heading. Where the lift occurs doesn't matter, so these should be back near the stern, not amidships as shown in the patent application.

[Crikey]

going to generate 30 lbs. of back pull as soon as the wing touches the water. That's not by any means insurmountable, but it's enough to feel it happen. Where the lift occurs doesn't matter, so these should be back near the stern, not amidships as shown in the patent application.

I imagine you'd want the lift effort to occur at, or near, the center of buoyancy or hull balance. Either way, with the fore-aft pitch angle changing all the time, the lift to drag ratio could vary greatly. Any sort of side wave would also cause it to dig-in, with unpleasant results.
R.

[seahouse]

There’s a “delta winged” dinghy called a CL Stealth that has moulded-in “bat wings” that ride in the water when heeled. The boat is built for speed, and is reportedly FAST. The initial prototype did, in fact, experience excessive drag in the wings and resulting extreme yaw “digging in” that was somehow corrected for in the final production run.

Don’t know exactly what they did to correct it, and I haven’t seen one up close yet, but here’s a link to a few pictures of it – scroll halfway down the page…

http://reddwarf.weebly.com/daily-dwarf-musings.html

So it’s not an insurmountable problem to overcome.

- Brian.

[mastreb]

going to generate 30 lbs. of back pull as soon as the wing touches the water. That's not by any means insurmountable, but it's enough to feel it happen. Where the lift occurs doesn't matter, so these should be back near the stern, not amidships as shown in the patent application.

I imagine you'd want the lift effort to occur at, or near, the center of buoyancy or hull balance. Either way, with the fore-aft pitch angle changing all the time, the lift to drag ratio could vary greatly. Any sort of side wave would also cause it to dig-in, with unpleasant results.
R.

I'm just guessing here, but I think any suddenly induced drag should trail the center of buoyancy for exactly the same reason that the center of effort leads it: helm balance. When the CE is aligned with the CB, the helm is very nervous and the boat has a hard time tracking. This occurs on main only. With both sails or jib only, the CE is well forward of the CB, and this lead in the forces acts like a pull from the front rather than a pull from the middle. My thinking is that drag at or forward of the CB will contribute to helm instability whereas drag after the CB will contribute to balance--as does a drogue or dipping the prop without running it.

Exact same principle Is in play with bicycle steering: when the forks are not raked forward enough, the steering is twitchy and will not track straight unless forced. Raked too far forward and it becomes very difficult to steer. There's a sweet spot at about 70 degrees where the steering is nicely balanced because the center of fork rotation when projected to the ground leads the center of balance for the wheel by a few inches, which acts like a force pulling on the wheel from the front rather than pushing it from behind. This stabilizes the steering dramatically, allowing the bike to both automatically track and to automatically steer into falling, automatically correcting the fall as long as its moving.

Anyway, just guessing, and too busy with my twin wing madness to test just yet. I'm buying a dinghy with twin leeboards however, so it'll be trivial to test this theory as well.

[finding41]

So now back to the dagger board...
I'm going to build a PDRacer (Link; http://www.pdracer.info/ ) this winter and am planning to have lee boards. One on each side. Link: http://www.leeboards.com/
After reading the discussions here I am going to make each a foil shape for lift. link: http://www.worldofkrauss.com/
(I've been looking for a way to gain an advantage as hull shape is regulated up to 10" from the bottom of the hull.There is no restriction on lee vs center board. Or foil shape of either.)
I think this will be the solution. If I can get extra lift from the lee board all the better.

[mastreb]

Happy to help if you'd like--I can work out the geometry of an ideal foil for the given speed and water density. Leeboards are the perfect application for this.

How fast can those PD racers get to? 4 knots?

[finding41]

Thanks for the offer! Any design help would be greatly appreciated! I was just going to use one I found or designed form that world of krauss site.... My foil knowledge is limited to what I have learned on sailing sites. (I did shape the rudder to .0018 ish on my 26D. I wanted .0012 but I was just working with what I had.)(2x12 with both edges rounded like these brackets!)
Yes PDRacers screams across/through the water at around 4 knots.
I'm going to fly a asymmetrical spinnaker when I can. I'm hoping to get it up on plane. (If it will.) I am yet to choose a main sail design/rig for it.
Note: I think I remember something about the max width....? May be 1"...?
I'll check later.

[finding41]

I'm wrong. No restriction on width or length. Link, http://www.pdracer.com/keel/
I am thinking of having them swing down from the back so I can cleat it in place.
This will make it quick and easy to un-cleat and cleat the other on a tack.

Oh. It says on the PDRacer site one guy had his up to 9 m/h or 7.8 knots!

[Boblee]

Reckon you blokes are making hard work out of what is meant to be a relaxing boat that sails and powers when the wind drops but whatever good luck with it.
See in the maxi yachts competing in the Sydney to hobart they shift ballast water and have canted keels but I guess those Keels are weighted too.
Anyway good luck will watch and if someone finds a way to dampen the heel might even have a go at it but for now will just stick to letting the sheets off a bit.

[mastreb]

I'm wrong. No restriction on width or length. Link, http://www.pdracer.com/keel/
I am thinking of having them swing down from the back so I can cleat it in place.
This will make it quick and easy to un-cleat and cleat the other on a tack.

Oh. It says on the PDRacer site one guy had his up to 9 m/h or 7.8 knots!

On the PDracer.com site where it shows keels, it points out rather clearly that a simple "teardrop" shape on the foil is nearly as good as a NACA foil. The reason this is the case is the low speed. At four knots, the difference in drag between a naive and complex foil is going to be negligible, and frankly, it's going to be negligible for an asymmetrical foil. The fluid speed is a straight multiplier for both drag and lift, and at low speeds, there's very little real difference.