Mod involving the X-Compression post

[Gerald Gordon]

I' thinking about doing a CB mod which would involve the compression post.

Has anyone ever taken the compression out and then successfully replaced it?

[Frank C]

Gerald,
I've never read that anyone reported removing the compression post. It should not be terribly difficult or dangerous to do it (after lowering the mast, of course) but I cannot recall that it's ever been described. I do recall seeing someone's mod of the entry into the bottom of the post. You can find his pictures in the Mods pages.

You wrote earlier that you expect the pipe is sched-40? I'd be very, very suprised if it's as thick as that size PVC. It's clearly stainless, so I'd bet it is about the same wall thickness as the mast crutch, or maybe one size thicker.

I had trouble understanding your earlier description of this mod, so cannot suggest anything else useful, other than maybe - good luck.

[Gerald Gordon]

I would like to deploy the CB horizontally: not have it pivot down the way it does now. Looking at maddmikes CB mod, he has perhaps 12 inches protruding from the hull even when the CB is retracted.
I think that the CB in a horizontal position would improve pointing as has been pointed out.

Im thinking about using three SS pipes and attaching them to the CB (like an upside down T. The pipes would slide up and down in the compression post and two other guideposts. The line that is now used to lower the CB would be attached to the pipe inside the compression post. So thats how I would deploy the CB.

I would add a guidepost on the front of the CB where the pivot bracket is now and another guidepost somewhere aft of the compression post, equidistant. All three pipes would run inside sleeves which would be secured in the boat. One of these sleeves would be the compression post itself. These sleeves would keep the CB from yawing.

I dont know exactly how wide the CB is. I would like it to be deployed to the maximum i.e. the top of the CB (long section) would be even with the bottom of the hull.

The retractable nature of this mood would not require a trailer mod and would still maintain the smooth undersurface of the hull

[Frank C]

Well, now that I understand it better ... at least it could largely occupy the trunk opening even when deployed, thereby reducing the drag from an open trunk. But that's a very minor advantage for the effort involved.

This horizontal board would be an involved, complex mod, that is only slightly more effective than releasing a short bit of line to pivot the aft board down by a foot or so. Roger's foil design, board & rudders, is high aspect ratio ... maximum lift with minimum drag. The CB you're describing is at the opposite end of the spectrum, lowest possible aspect ratio with deminimus (possibly even zero) hydro-lift.

It seems to me that you need some added advice from Maddmike regarding his board. I'll be very surprised if he suggests that his board adds more than a trivial advantage (for pointing) when horizontal. I'm almost certain that his board is vertical when it improves pointing (i.e reduciing tacks from 14 to 9). I kinda assumed that its major pointing contribution is from the added two feet of depth, plus maybe some added stiffness or stability within the trunk.
Could be wrong, but I don't think so.

EditToAdd: Upon reflection I'd guess Maddmike's board improves pointing more by brute force rather than design. Again, on the premise that both boards deter leeway primarily after they're lowered by 70% or more:

• - Width of the stock board is 12" or 14" (folds up fully within the trunk)
  - MM's is about 24" wide (fore-to-aft) when down, and also 24" deeper
  - With significantly more surface area, it MUST BE increasing surface drag
  - Conversely, all the added surface area of this "slab-board" resists leeway
  - MM-board is much stiffer & stronger to resist bending or twisting

Finally, I'm not sure I read the slab was faster, just that it improved pointing angle, and of course, was meeting the primary goal of being stronger in heavy seas.

[Bill at BOATS 4 SAIL]

I think the SS pipes/sleeves might keep the CB from yawing.
But, I think it might be difficult to keep them from jamming, with the center one acting as a pivot point, if you hit something with it, or even just from the pressure exerted on it from the forward motion of the boat.
The forward one might get jammed higher, or lower, than the rear one.
Also, what Frank C says about CB shape efficiency

[craiglaforce]

You may have lost your mind.

Sincerely,
Craig

Sorry, I couldn't resist.

Long, thin, high aspect foils are the most efficient shape for windward performance. But you have to balance the weather helm with the mast rake reduction to achieve this. On our boats, this balance point is in a narrow margin.

What you describe is the exact opposite of a high aspect foil and will work far worse, but it will be more forgiving on helm being out of balance, since the center of lateral resistance will be more spread out.

Furthermore, pokin a bunch of holes in the bottom, and putting a sliding tube system in like you describe, that has to hold the heeling forces of the boat on a couple or 3 tubes, without jamming, leaking or ripping out entirely, seems problem filled at best. Plus the centerboard is probably too narrow. I am pretty sure an 8 inch keel or wahtever is not enough.

Please forgive my first sentence, I couldn't resist being a smart alek.

[argonaut]

Amazing.
And I used to think Pintos with V-8s bolted in were goofy.
At least they -did- go appreciably faster after they'd been hacked to bits.

[Gerald Gordon]

...and to think, I was going to go where no man has gone before!

By the way, CDI now has a mainsail furler. It's not sustom made for the X. I think my design works better for a trailer boat......Oh, wait...I think these are the same comments I got when I did the sail mod.

I don't quite see how a cheezy SS hanging bracket with a 5 foot board is more solid than three schedule 40 pipes mounted inside the boat.

One good point was made...leaking.

Does anyone know the thickness of the fiber glass on the top portion of the CB boot (where the compression post is mounted)?

[ALX357]

X-boat CB side forces are supported/resisted by the reinforced trunk on the part of the board retained in the trunk, not the SS bracket, which just pivots it and keeps it from falling down at the front. Schedule 40 plastic is is not that torsional resistant, and instead of bending, if it is rigid, and under too much stress, will suddenly shatter. Made for pressure containment, it is not a structural material.
Also consider the presence of two more tubes in the cabin, the rear-most tube being particularly obstructive.

[Eric O]

Gerald,

I was looking at removing the mast compression post on my M19 so I could access the nut on the botoom of the bolt that goes through the mast step plate into the center of the post. It would have involved cutting away a part of the liner and sliding the bottom of the post off the top of the trunk to one side. But I gave the idea up when I could not budge the post with the mast removed. If the 26X is similar it will be quite a job to get the post out of there and probably even harder to get it back in.

For what it is worth I think it is the extra size (surface area) of MM's board that gave him better pointing ability not the fact that a small part of it is lower. If you were talking about extending a weighted bulb for ballast lower to improve heeling that would be a different matter, but my guess is putting the same size board just lower in the water is not going to give as much improvement for pointing as increasing the size does.

[Newell]

GG,

Consider a mod that replaces the Fiberglass CB with a SS one, similarily shaped, with the lower end shaped for a single point attachment. I know this would be challenging. However the mod would be to add a shaped leaded form (Wing?) with a design that would allow it to pivot 90 D. When the board is deployed to full down the wing would assume a horizontal position, providing added heeling moment for improved pointing. As the board is raised the wing would rotate to balence itself in the same position. When the CB is fully retracted the wing/form would rest parallel underneath and next to the belly of the hull.

Ancillary mods would be required to the trailer, the CB rasing system and perhaps the CB trunk. What would 100 lbs 5'6" below the boat do for improved performance?

[ALX357]

If the wing-bulb were heavy enough to make any difference in stability, it would not be light enough to deploy flat parallel with the forward motion of the boat with the board at different heights - in light air, causing it to add resistance and slow the boat further. Make it light enough to pivot parallel to fwd. motion at slow speeds in light air, and it would not add much stability, just cause a mess of complications and mechanical linkages to gum up with marine growth, corrosion, etc. and cause mods to the trailer to be necessary.
JMO, but learn the boat as it is, leave theat the hull and board design as it is, and learn to sail it as well as you can. It is not a racer, never will be, and excessive mods that add weight and complexity are counter-productive.
As for pointing higher, there are threads on this board that describe successful shortening of the spreaders, (by 8 inches each side) allowing tighter Genoa sheeting and better upwind performance, but there are many objections to its safety, mostly based on the theory that Roger made them as short as he safely could already, but i think the mod needs more examination.
Easy to do, enough, and not that radical IMHO.

[Greg]

Gerald,
I like how you think out of the box. How your design would affect the performance of the X is beyond my speculation, but I think rigging up a test board wide (deep?) enough to simulate your fin in the "deployed" state would be worth the effort.
Dropping the factory board is easy and simply replace it with the test board using the same bracket and rope to hold it up. If it works to your satisfaction, then work out the other details.
Good Luck
Greg

[Dimitri-2000X-Tampa]

I agree long thin foils are likely best for racing and will go the fastest, but in the case of MM being out in open water more often and going slower, an all around bigger CB probably helps overall both for going upwind in lighter air as well as more lateral stability in heavy seas.

[ALX357]

trying a test board first using the bracket and line without making a trailer mod would be really difficult. You'd have to be in shallow water, deep enough to float the boat with board "down" and shallow enough to have standing footing to manage the swap, and the lungs to work underwater several minutes at a time, or SCUBA gear, or an air hose etc.