Lee-ving

[NiceAft]

Bertil Rafting,

Don't forget to post some pictures if you actually do this.

Ray

[Ixneigh]

If your bent on this project I suggest an outside folding wing. That coujd even be installed as a temporary experiment.
Lightly glass a wood rail to the waterline. Attach the butt end of your foil to that with a hinge mechanism to allow it to fold up against the side of the boat. Hold the wing down while sailing with a strut braced on the rubrail some place. You might need a brace point installed. But that could be epoxied on easily. If you were ambitious you could have a set of these ready to try out in a couple weekends, and still be able to revert to factory, minus a small amount of cosmetic work, easily. I did that with my dual skegs. They are still on there. My temporary work turned out to be pretty durable so far. I would also make the hinge setup so the butt end of the foil is under the wood rail, that would take the upward thrust. Try it out in some calm water and let us know. I Highly doubt a boat like the Mac is going to benefit enough to make it worth while.

Some other points to consider. That wing sticking out could suddenly make the boat want to roll if it's caught wrong by a wave or the helmsman screws up. Since the Mac doesn't move very fast you will need a sizable surface down there.
Also note the macs lack of a long deep keel with a huge chunk of lead on the bottom to damp and rolling tendencies.

Since I can't pull up the board while the boats sailing I assume I could not slide the foil into the trunk to clear seaweed either, without luffing up and stalling the boat. How were you going to slide the foil in and out again?

Ix

[BOAT]

I find it hard to believe that a 40 inch wing would be required to lift such a light boat as the MAC. Perhaps someone should remind him how light the boat really is. I'm no engineer though so I guess a lot of the issue here is that the wing is probably really narrow (based on what I saw on his website) and that would make sense for a racing boat because the narrow wing would not create much drag. I suppose for a MAC you could make the wing a little wider so it has more lift, but I assume these guys know what they are doing.

The wing on the 50 foot boat on his site looked like about 20 inches wid - if you scale that down to a little 26 foot MAC I would have assumed a wing about the width of our rudders and not even that long.

[BOAT]

If your bent on this project I suggest an outside folding wing. That coujd even be installed as a temporary experiment.
Lightly glass a wood rail to the waterline. Attach the butt end of your foil to that with a hinge mechanism to allow it to fold up against the side of the boat. Hold the wing down while sailing with a strut braced on the rubrail some place. You might need a brace point installed. But that could be epoxied on easily. If you were ambitious you could have a set of these ready to try out in a couple weekends, and still be able to revert to factory, minus a small amount of cosmetic work, easily. I did that with my dual skegs. They are still on there. My temporary work turned out to be pretty durable so far. I would also make the hinge setup so the butt end of the foil is under the wood rail, that would take the upward thrust. Try it out in some calm water and let us know. I Highly doubt a boat like the Mac is going to benefit enough to make it worth while.

Some other points to consider. That wing sticking out could suddenly make the boat want to roll if it's caught wrong by a wave or the helmsman screws up. Since the Mac doesn't move very fast you will need a sizable surface down there.
Also note the macs lack of a long deep keel with a huge chunk of lead on the bottom to damp and rolling tendencies.

Since I can't pull up the board while the boats sailing I assume I could not slide the foil into the trunk to clear seaweed either, without luffing up and stalling the boat. How were you going to slide the foil in and out again?

Ix

Huh? That's strange - I pull up the board all the time while sailing - I pull it up a bit when I move to a broad reach and let it down when pointing. Geeze, I thought everyone did. Why can't you pull up your daggerboard when sailing?

[Jimmyt]

Kinda looks like this one is wider than the boat... Similar sized application.

[BOAT]

The Spreader? Yeah, the spreader is always almost as wide as the boat - but who's talking about spreaders? I thought we were talking about a wing. Oh, you just changed the picture on me -

Yes, I think the guy said they were using cassetes (wells) to mount these things so I must assume there is a well on each side for that one.

[Jimmyt]

You're not the only one that has trouble posting pictures... But you do have the ability to capitalize on an error - excellent timing!

[BOAT]

Sorry, part of the reason that I am a troll is because I just type whatever I am thinking immediately before I even look at what I am saying - that's why I always have posts that sound like troll talk.

If I would just slow down a little I would not get into so much trouble but I just can't slow down -

[Jimmyt]

I was thinking this was the retracted length. I don't see how that small foil at that short length would be that significant. Could you find a video of one in action (i found a Quant 28 ft racer - which would fly. They got knocked down during the run with a lot more foil out than this pic shows..). Neat idea, just a bit skeptical. http://youtu.be/Kd5k-l0NkC4

[Lee Ward]

The location of the foil with relation to the center of gravity (fore and aft) and it's angle of attack would appear to be critical. Without tank testing I would think it wold be difficult to achieve the optimum AOA on the foil. If the foil were off by a couple of degrees AOA one way or the other it would cause major performance losses IMO.

[BOAT]

The location of the foil with relation to the center of gravity (fore and aft) and it's angle of attack would appear to be critical. Without tank testing I would think it wold be difficult to achieve the optimum AOA on the foil. If the foil were off by a couple of degrees AOA one way or the other it would cause major performance losses IMO.

yes all of it would be difficult to achieve. It would require a pro. All the proper calculations would be required and tank testing and so forth.

[grady]

The location of the foil with relation to the center of gravity (fore and aft) and it's angle of attack would appear to be critical. Without tank testing I would think it wold be difficult to achieve the optimum AOA on the foil. If the foil were off by a couple of degrees AOA one way or the other it would cause major performance losses IMO.

Yes and remember with the X and the M with a big engine on the back your CG is way aft of the center of the boat.

[Ixneigh]

I can't pull the board up while sailing.

Because I'm not Herculese. I have to luff up and almost stall the boat...then I am able to pull it up.

Re size of wing...Its speed. Five knots is just not that fast. The effectiveness of the foil (math, someone) goes up with speed. That large sled is doing 25 knots. Now that's alot of force.

And any foil that is effective enough to reduce the macs heel to a worthwhile degree will not be able to be moved in its housing by hand.
But try my set up to test the foil idea. You won't find a simpler or easier way to do it.
Plus you can fool with angles by messing with the strut length.

Ix

[Bertil Rafting]

I have now togaetgher with a yacht designer started a for-study to see if it is suitable to build a lee-wing for the Mac M and the estimated cost for doing it.

[BOAT]

I seriously doubt it will be cheap enough - the boat only costs 22 thousand dollars brand new so no one is going to spend 5 grand on a wing.