Swing Keel mod (Skeg maybe?)

[Gerald Gordon]

I'm thinking about extending the keel 12" vertically. When the keel is retracted there would still be a 12 inch section (full length of the keel) showing below the hull.

What may be the effect of this mod on sailing/performance?
How would this mod effect motoring at full speed?

[March]

My uneducated guess is, Roger knew what he was doing. If a longer keel would have made a significant difference, he would have done it. He probably weighed out all possibilities and factors, and came up with the optimal solution--the present one

For motoring, you would retract the keel anyway, so that doesn't really apply.

I imagine you would either bolt the extension, or build a newer, longer keel from scratch (make a mould, pad fiebrglass, etc.) A lot of work--and for what?

[Frank C]

Gerald and March, you're referring to two different mods. Gerald wants a "wider" board, from current 12 inches to 24 inches. That means it would still have the forward 12" exposed beneath the hull when fully retracted. That means it would require a special trailer.

March is writing of a longer board, one that extends to 6+ foot depth when fully deployed. My take ... the boat needs a wider board in certain conditions, but I'd be happy with only 3 inches wider. It would be trailerable with minor trailer mods. It wouldn't increase side-loading on the trunk as much as the 24" board.

And, it's already been done. Not sure where the pix are stored, but Mad Mike did a similar mod to his 26X. At a moderate size, like 3 or 4 inches exposed, I'd guess it should be fine for moderate motoring speeds, with much improved tracking.

Roger's basic design has the hull leaning quite naturally to the inside of high-speed turns ... as all power launches should. However, with the wider centerboard, a WOT full-lock turn would probably tend to trip the boat, forcing it to lean dangerously to the outside of the turn - not good. Seems to me it would be a great mod for a basic "powersailor," but not one who's interested in towing water toys.

[Night Sailor]

Every keel design is a compromise, there is no perfect solution for a keel boat much less a power sailor hybrid.

One needs to consider also that adding greater area will necessarily add more weight, so the lifting mechanism needs to be repositioned and perhaps beefed up to manuever it while under sail. And, the mounting of the pivot axles to the boat's hanger may need redesign to accomodate the stresses of additoinal pressure under sail or power.

I think we all agree that the boat's performance and comfort design could benefit from a heavier more robust keel in the X or the M. More consideration was appartently give to keeping the gross weight of the boat down so it could be advertised as trailerable by a family car.

I think we would all agree too, that for seakindly motion and considerable autohelm use in open water, a keel that extended below the hull a few inches at all times when fully retracted would be beneficial though detracting slightly from top speed perhaps, ala MadMike's Arrow.

Given it's drawbacks and it's great points, the X is still the best boat for anywhere near the price, that is available and appropriate for a lot of situations, including my own for lake or river, shallow water coastal cruising with beaching capabilities, and relatively inexpensive slips. A cat that could do what the X does in shallow water would cost much, much more to purchase, and at least twice as much to dock, without being trailerable.

Fortunately I've learned to be a jack of all trades over the years instead of making a lot of money in one profession. It certainly had been a help on doing what I could to make the X more to my likeing. It must be hard to have to have someone else do the work.

[Duane Dunn, Allegro]

I've always felt the X would benefit from a forward skeg under power. I intend to add this at the forward end of the centerboard. It would not run the full length of the centerboard. It would stick out 3-4" and be about 18" long. It would be a simple 1/4" aluminum fin attached to the leading edge of the centerboard. The purpose is to improve tracking under power. No enhancement to performance under sail is expected.

As far as a full length expansion, I would think you could go to a 6' - 8" extension without having any trouble with the trailer. As long as your ramp is of a reasonable steepness there is actualy quite a bit of clearance to the cross bar when the boat floats on.

That said, I'm not convinced a larger section added to the full centerboard would really improve sailing performance and I think it would add too much extra drag under power for my needs.

[delevi]

I think the stock size boards provide sufficient lift for the boat to point well. IMHO, anything more would be overkill, more drag, more weight, and I just can't see any benefit in motoring performance, rather the contrary. When I upgraded my rudders to the IDA rudders, which I had made longer and wider, I noticed a significant improvement to pointing, probably due to the added lift created by the larger rudders. The boat also tracks better under sail and handles better under power at low speed. I would suggest looking into a rudder mod vs. messing with the cb/db configs, unless of course, you're adding ballast. But I won't open that can of worms again.

Leon

[Dimitri-2000X-Tampa]

Leon, I can see where larger rudders would make for better tacking and gybing and I can also see how they could better prevent rounding up during heavy wind, but I don't understand why your pointing would get better. Do you have any theories on that?

[Frank C]

Maybe Leon's running backstays are having that impact on pointing (improving the forestay).

So many mods, so little time to analyze each of them~!!

[March]

I can't quite see how larger rudders would result in less drag. On teh contrary: there would be more drag, because there would be more area of the rudders exposed to friction.

Now granted, eric didn;t refer to larger or longer rudders, but better ones. That would mean, more aerodynamic (or water-dynamic) or narrower, or even lighter, so they would not generate as much friction and consequently drag. Extending the rudders would not automatically create less drag. Seems that they would give better leverage when it comes to turning since a wider surface would prop itself more efficiently into the water and cause the boat to swing more readily to right or left--hence better control. At least that's how I visualize it

[Mork]

Getting back to the KEEL. If you have any board showing under the hull it will effect the way the boat turns under power. As has been said if using WOT the boat is in danger of tipping. I tend to motor at 5 knots with board and rudders down. 9-11 knots with about one or two inch of board down and no rudders. Above this everything up. and hatches shut. This way the boat responds as it should and is fairly easy to handle.

NaNu NaNu

[Duane Dunn, Allegro]

The talk about the rudders is interesting. Old X's like my '96 have significantly larger rudders. The later X's went to a smaller section and the M rudders look even smaller than the late model X's. Maybe the old big rudders are one of the reasons I've always felt my boat can point reasonably well.

As I said in my comments above, my reason for adding what amounts to a skeg is purely for performance under power. I'm refering to speeds above 8 knots when both rudders and centerboard are all the way up. I have many, many miles (almost 1500 at this point) under my hull operating the boat in this configuration and I find it has a tendancy to wander as it makes it's way through anything but smooth seas. It is highly influenced by waves which easily push the nose off course. I think having some side ways resistance up front would help resist this movement.

My skeg would be a purely flat thin profile section that developes no lift at speed. This would eliminate the roll induced by the centerboard if you have it down at higher speeds, yet would put a little bite into the water when the boat encounters waves.

[baldbaby2000]

Getting back to the KEEL. If you have any board showing under the hull it will effect the way the boat turns under power. As has been said if using WOT the boat is in danger of tipping.

I would take this comment seriously. I saw a posting on sailinganarchy that mentioned an X going fast and almost tipping when he turned. I assume he had some board down or it would have banked with the turn. Not only does it make Mac sailors look like bozos, but it is dangerous.

On the subject of whether it helps sailing. I've wondered if the M board is big enough because in very light winds the boat tends to turn downwind. It may be a rudder issue too (see Leon's and Richard's posts on rudders). I've read a lot about keels and the best keel depends a lot on how fast the boat is going. A deep narrow keel is good for fast boats but I'm not sure the Mac gets going quite fast enough to allow for the narrow keel to provide good lift. It does seem like making the keel longer might still help pointing ability even though an equivalent increase in surface area in width might be better on a slow boat.

BB

[Frank C]

... At a moderate size, like 3 or 4 inches exposed, I'd guess it should be fine for moderate motoring speeds, with much improved tracking.

Roger's basic design has the hull leaning quite naturally to the inside of high-speed turns ... as all power launches should. However, with the wider centerboard, a WOT full-lock turn would probably tend to trip the boat, forcing it to lean dangerously to the outside of the turn - not good. Seems to me it would be a great mod for a basic "powersailor," but not one who's interested in towing water toys.

I wrote conclusions on the first page of this thread, without the corresponding justification or logic.
Herewith, some logic (counterpoints welcomed):

The 26X centerboard is a sailing necessity, but a motoring detriment (likewise, the rudders, at speeds over ~5 knots). Even at 10 knots, dead ahead, the symmetrical foils set up vigorous alternating lift across one side or the other. This causes oscillations that constantly redirect the vessel's path. The result is imprecise, unpredictable, potentially dangerous self-steering. The foil is simply causing fully expected but undesireable lift to either side. The M-board would have similar effects. Either board will have greater impact as they drop deeper below the hull.

Just a guess ... nearly every Mac owner (w/50 hp) who has used his Mac at speed has felt this eerie, drunk-like response from his hull ... we ALL forget the boards, at least once.

During turns, it's also quite straightforward to understand. The Mac X's hull shape induces a quite natural feeling "powerboat" speed turn. The hull leans quite willingly and naturally INTO any turn, with authority, just as expected on any power runabout. It's quite eerie to feel this with a rig towering 35' above the water, but it's quite solid and predictable. Even at WOT we can crank into a hard turn without any fear of upsetting the boat.

Of course, centrifugal force simultaneously skids any boat to the outside of the turn ... more speed imparts more C-force & more skidding. Such beneficial drift is the reason there's no concern of upsetting. BUT, should the board be unknowingly left extended, the boat leans alarmingly outboard - not good! Since the board deters centrifugal drift, the hull "trips over" the board. The towering rig no doubt exacerbates. Here again, the effect is quite simple and understandable. The M-board - similar.

A centerboard that is left very slightly deployed, say just at the tip, would have only negligible sideways lift when dead ahead, and negligible impact on centrifugal force in turns. I'd guess the same is true for a skeg that's one inch deep by 5 feet long. As the skeg becomes deeper, it's impact on turns should be more pronounced.

[baldbaby2000]

On a daggerboard boat in light weather I would raise the board up a bit and raise one rudder, since there's little point dragging all that stuff underneath.

Are you suggesting raising the board even going to weather? It seems like you'd want all the board down when going up wind. I've tried going with a rudder up but haven't seem much difference.

BB

[Dimitri-2000X-Tampa]

If you are trying to go upwind in a Mac during light wind conditions, I think you need the board all the way down, but if it gets windy, then you want it up a bit. Also very important to have your sails well balanced. If you come from a keelboat background, you won't think the Mac goes upwind very well compared to the keelboat. It also has less inertia than a similar sized keelboat. But reaching and running are quite good in a Mac, especially when you can pull your CB all the way out while sailing on a broad reach.