Fail Unsafe

[bscott]

I have to disagree about the over engineering of a 5/32 forestay. My mast exhibits a fair amount of pumping at any speed over 8 knts in 2/3' chop--and that is with a 5/32 back stay and shrouds at Loos 240 and 280. That is alot more stress than your typical light weight tailer/sailor like a D and an S that typically cannot exceed hull speed while under power but not on a light weight boat like an that can go fast. I also witness a few in my marina that have jib covers that flog violently in the wind which can't be good for the rigging. Better safe than sorry.

Bob

[magnetic]

Better safe than sorry = take the mast down

I don't think its quite that bad,though I do check my standing rigging (including all the split rings) before and after every outing

The problem with the and the is that everything fitted by the factory is only just man enough for the job; redundancy and failsafe are not built into the boats, and the typical margin of error is consequently just not there to get you out of a sticky situation

[Catigale]

10000 hulls delivered and how many masts have failed from fatigue?? None that I can recall on this board in 7 years. Your mast undergoes much more pumping and flex when it is trailered than it ever undergoes while sailing btw. That's why it is relatively light and flexible. Again, rough engineering analysis is trumped by 1000s of experiences
To reiterate, engineering is not just a case of stronger is better.

Recap....don't change rigging unless you understand and measure the tensions on your new rig. Some of you guys like Dave clearly get this, but this thread is aimed at the new owner who might think a larger forestay is 'safer' - whereas only a properly installed and tensioned forestay is more important than it's size.

[Terry]

Better safe than sorry = take the mast down

I don't think its quite that bad,though I do check my standing rigging (including all the split rings) before and after every outing

The problem with the and the is that everything fitted by the factory is only just man enough for the job; redundancy and failsafe are not built into the boats, and the typical margin of error is consequently just not there to get you out of a sticky situation

Spot on Magnetic!
You couldn't be more correct, these are price point boats built with every cost cutting feature in mind. They are basically a hobby starter kit where you have to go out and buy the final pieces to finish and complete the boat. The newer M's have a smaller diameter mast and nylon winches for cost cutting examples. Who knows what else. Oh, the headsail is now an option whereas when I bought mine in 2003 it was standard fare. The mods section on this board is testament to how unfinished these boats truly are.
While there are new owners who may feel more comfortable leaving well enough alone, over time and experience these same new owners will come to realize that there is in fact plenty of room for improvement and with some aquired knowledge and experience they will make the neccessary changes. I am one of them!
I made it my business to learn all I could both from contributors on this board and other sources and over the years I have gained a lot of confidence and knowledge in my quest. I have a Loos guage that I measure the tension with every year and I keep my rigging tuned around the 10% range on the shrouds but the forestay seems to always have more tension no matter what I do. That is ok though because it is taking the force of four shrouds and a roller furler with sail. Through the winter I had to remove the sumbrella headsail sock/sleave and the headsail to stow them below because the winter wind storms were too much stress on the rigging, a bare foil reduced stress on the system. (I slip). I also had mast failure right in my driveway, while raising the mast with the brake winch the rotating mast pivoted to one side and the force caused the mast to crease quite badly right at the bail attachment point for the mast raiser. I now tie the mast off to a stationary position before raising to prevent future occurrences. That was my second mast failure, first one happened in a harbour while underway. It was my first year and some other inconsiderate boaters precipitated the circumstances that caused that situation to take place, even now several years later, in hindsight I can deny all or any blame but I did learn how to stay out of the way of other ignorant boaters. There are probably many mast failures out there but many go unreported so we assume they don't take place when in fact they do.
Bottom line is that due to cost cutting practices and price points these boats err on being under enginered not over enginered.

[DaveB]

I replaced my headstay two years ago because 2 strands of wire at top broke at the fitting. I went with 5/32nd .
I should have mentioned this.
Dave

10000 hulls delivered and how many masts have failed from fatigue?? None that I can recall on this board in 7 years. Your mast undergoes much more pumping and flex when it is trailered than it ever undergoes while sailing btw. That's why it is relatively light and flexible. Again, rough engineering analysis is trumped by 1000s of experiences
To reiterate, engineering is not just a case of stronger is better.

Recap....don't change rigging unless you understand and measure the tensions on your new rig. Some of you guys like Dave clearly get this, but this thread is aimed at the new owner who might think a larger forestay is 'safer' - whereas only a properly installed and tensioned forestay is more important than it's size.

[Judy B]

Magnetic;
Your dilema has served to re-inforce and substantiate my decision to go with the Shaefer CF700 Snapfurler. I have had it on a few years now and the open drum feature is no threat to the fingers plus this furler incorporates the use of the jib halyard to raise and lower the sail like a hank-on, so in your case it would have only been a couple minutes to drop that headsail and stuff it down the forehatch. The Snapfurler does cost a bit more but in the end you get what you pay for. I have no regrets especially after some of the episodes I read about and some of the situations I see first hand.

I quite agree with Terry that the SnapFurl is a far more capable furler than the CDI. But it doesn't have to be a lot more expensive than the CDI. I sell the SnapFurl CF-500 for under $500, plus shipping. With a 150% genoa in 6 oz High Modulus Dacron cloth from Challenge, including a UV edge cover, the whole package is under $1130, plus shipping. Add a set of Ronstan 5 foot of genoa tracks with composite cars and ball bearing blocks, and you're still under $1330.

You can use the Schaefer CF-500 for the Mac26's, because they are comparatively light displacement compared to most 26 footers. I have discussed this carefully with the engineers at Schaefer, and they confidently recommend the smaller SnapFurl.

Fair winds,
Judy B

PS. I have tried twice in the past month or two to contact the webmaster to advertise via a banner on this site, without getting a reply. Please excuse the blatant ad below, but maybe that will get a response. I will try to contribute and be of service when I participate on this forum. If posting this is out of line, I ask the webmaster to contact me and I will remove the image and buy advertising space. Sincerely, Judy.

[Judy B]

...I replaced my headstay two years ago because 2 strands of wire at top broke at the fitting. ...
Dave

Hi Dave,

Was there a toggle at the top of your forestay, where it attaches to the hounds? There should have been.

The most common reason for broken strands on a forestay with a furler is lack of a toggle at the top, which leads to point load flexing, point metal fatigue, and subsequent breakage of wires due to brittleness. When there is no toggle at the top wire strand breakage is virtually inevitable, given enough duty cycles.

Q: Why don't wire strands break at the bottom of the forestay at the fitting, like they do at the top?
A: Because there is a toggle built into the furler at the bottom of the drum.

Imagine a piece of wire rope.... pull on the ends and you won't be able to break it..... but bend it back and forth at one spot a few thousand times and the outer wires break, one by one, and the inner ones also break in due time....

Take a paper clip and flex it back and forth until it breaks.... that's what's going on if there is no toggle....

Fair winds,
Judy B

[Ixneigh]

Re light rigging.
In some respects these boats are high performance boats stuffed into a forgiving and roomy hull. The weight savings means you have to be careful with it. Race boats have little redundancy.
I did not think the spar on my new M was undersize, but it sure aint overkill either. But overkill means wieght ontop. I bet if you asked MacGregor, he would give that as a reason for reducing the mast size. Easier to raise and lower also.
Cost between the two extrusions is probably negligable.
Although the wire seems thin to my eyes, its matched to the rest of the boat. Go up in wire, then what about the chainplates? I went throu the whole upgrade chain on my v222. more glass on the hull, nice bromze chainplates.
Larger wire. Then i put a free standing mast in her. Oh well.
But the point remains. Id rather part a stay then rip something out of the deck or hull.

Ixneigh

[magnetic]

a forgiving and roomy hull

roomy, I'll concede.......

[bscott]

Judy, it's nice to have a professional rigging person aboard--thank you. Thanks for the heads up on the use of hound toggles--any pics?

Also, most of the Macs sold with furlers were CDIs with #6 luff tape. Since all my previous boats had excellent Harken 00 Flex. I chose the CF700 because it was the only high quality flex furler that accepts a #6. I agree the CF500 is more than adequate but by the time I converted my sail(s) to a #5 tape, I was close to the price of the CF700. Maybe you can convince Schaefer to offer the CF500 with a #6 tape.

Bob

[Catigale]

Judy...I'll ping Heath to alert him to the ad request.

I'll leave the ad up in lieu of the good faith effort to contribute.

Thanks for the participation on the Forum.

[Terry]

Judy, it's nice to have a professional rigging person aboard--thank you. Thanks for the heads up on the use of hound toggles--any pics?
Bob

Yes, I'll second this, professional advice is always welcome.

[Judy B]

Judy, it's nice to have a professional rigging person aboard--thank you. Thanks for the heads up on the use of hound toggles--any pics?

Also, most of the Macs sold with furlers were CDIs with #6 luff tape. Since all my previous boats had excellent Harken 00 Flex. I chose the CF700 because it was the only high quality flex furler that accepts a #6. I agree the CF500 is more than adequate but by the time I converted my sail(s) to a #5 tape, I was close to the price of the CF700. Maybe you can convince Schaefer to offer the CF500 with a #6 tape.

Bob

Hi Bob,

1.) Here below is a picture of a mast hound (Ronstan), which is a good way to attach a forestay to a mast. (because the fasteners and the mast wall are loaded in shear, rather than stress)



2) Here below is a picture of an "eye and jaw" toggle which should be used at the top of the forestay when a roller furler or luff extrusion is present. Toggles can be eye-jaw, double-jaw, or double-eye -- what ever is needed for your configuration. The important concept is that the toggle functions as a "universal joint" at the top of the forestay, which relieves lateral forces where the wire rope enters the swage or fitting.



With a "universal joint" at both the top and bottom, both enda of the forestay are free to move in translation on three axis, plus rotate on two axis, for 5 degrees of freedom. The only constraint is that it cannot rotate along its long axis -- which is a good thing or else the wires would unwrap.

With so much freedom to move around, the lateral forces on the headstay don't get concentrated on the swage, breaking strands from metal fatigue. Rule of thumb, IIRC, is that each broken strand reduces breaking strength by 5%, multiplicatively.

AHA! It all makes sense now, doesn't it !?!?! With furlers, we find broken wire strands at the top whenever we cut corners and don't install a toggle. We don't find broken strands at the bottom swage... because all furlers have toggles integrated into the drum at the bottom end!!! cool. Give yourself an A+ if you got that

3) I wholeheartedly agree with you that it would be *Much* better if Schaefer made the CF500 so we could use a #6 tape. It makes converting to the SnapFurl more expensive than it should. It sure does make sense to me, from a marketing perspective.

But .... putting #5 luff tape on a Mac26 150% genoa shouldn't cost $400 (the difference in cost between a CF-500 and a CF-700). So the CF-500 remains a viable option.

Regarding the cost of converting from #6 to #5 luff tape: I'm making an informed guess here - It shouldn't cost more than $200. I'll double check on that with my local Hyde Sails loft manager; he'll know. 1.5 hours of labor is more than enough to cut the old luff rope off and sew the new tape over it, at $70-$100 per hour, depending on where you live.

Sailrite sells everything you'd need for under $75: #5 tape, UV polyester thread, seam stick (two sided sticky tape), needles, etc.

You could do it yourself with a good sewing machine The labor part is not complicated. Cut the old luff rope off, just aft of the cord, using a heat knife to keep the edge from fraying. (A $20 soldering gun with a $5 hot-knife tip is what a lot of sailmakers use). Put the new luff tape over the old, using seam stick tape to hold it in place, and stitch with zig-zag.

Another very cost effective alternative is to sell your old genoa with the #6 tape for $100 or $200 less than you paid for it (if it's in good shape), and order one with a #5 tape. That's what I usually recommend to my customers who want to upgrade from a CDI to a SnapFurl CF-500.

For example, I sell a roller furling genny with a #5 tape for the 26M in 6 oz High modulus cloth by Challenge, including a UV cover, for under $700, about the same price or less than the lofts who cater to Mac owners. That's not the cheapest price around, but In my professional opinion, all-purpose Roller Furler genoas need a stronger cloth and extra reinforcements than you'd need for a light-air genny. If you roll it up and use in in high winds as a working jib, and it's not built to take the extra strength of the wind, it'll get stretched out of shape after just a couple of hours of use in high winds.

4.) A little sail-design engineering about roller furling genoas follows:

Sailcloth is highly technical stuff. there's a lot more to it than how much it weight. Equally important is how we align the load bearing yarns to bear the stress loads we place on the sail.

Take a look at the Roller Furling Genoa below. It has a large elliptically shaped reinforcement patch along the foot, to spread out the load at the "tack" when you furl it up. The dots are furling marks corresponding to reducing the genny to 70,80, or 90% of the LP dimensions



The reefing area calculations work thusly:
A 150% genoa for a Mac26M has roughly 185 square feet of area.

@ the 1st reef mark: it's reduced to 150 square feet, or 81% as big as the full genny (.9 * .9= .81)
@ the 2nd reef mark: 119 square feet, or 64% as big as the full genny (.8 *.8 = .64)
@ the 3rd reef mark: 91 square feet, or 49% as big as the full genny (.7 *.7* = .49)

A working jib for the Max26M is approximately 125 square feet. Compare that to the genoa when it's reefed to the third mark -- 91 square feet. When you reef the genoa to the third reef mark, it's much smaller than a working jib -- it's being asked to perform in the same conditions as a storm jib.

When you're sailing in winds strong enough to need to furl to the third furling mark, it is down to the size of a storm jib. The sail needs to be very strongly built if you're going to subject it to such high winds. If you use the factory genny, made with a 3.8 oz basic cruising dacron, it's going to get "blown out" in an hour or two..

6.) How much power does a storm sail generate compared to a big genoa? The surprising answer is that the storm sail generates more power than the 150% genoa , when used in typical, appropriate wind conditions.

Example:
Let's assume we have a 26X genoa with 180 square foot genoa in winds of 8 miles per hour. let's assume the force is 10-units per square foot of sail area .

Now, how about a storm jib in winds of 24 miles per hour? The force generated by the wind is is proportional to the velocity of the wind squared. The wind is 3 times stronger. The stress on the sail cloth of the small jib in high winds is 90-units of force per square foot of sail area. that's a lot of power being generated.

But what really matters is how the shape of the sail is distorted by the stresses and where the stresses are transmitted. In part, the stresses on the sail get transmitted to the corners, which causes distortion at the corners. Another part is that the stress causes distortion of the sail in arcs from the corners, along the luff and leech and, to a lesser extent, the foot .

If the sail is reefed to 50% of it's original size, but the lift being generated psf has increased to 9 times the original, the stress on each corner of the sail has been increased by a factor of 4.5. If the furled sail is made of light weight material, the distortion (strain) will be too far past the sail's limitsof resistance, and permanently distort the shape.

Both cloth and high-end construction features add to the sail's capacity to resist stretching. That's why the extra reinforcments along the foot of the reefing genoa are just as important as the choice of cloth.

With 4.5 times as much force on each part of the sail, you need to engineer it so the yarns in the cloth are properly aligned to take the abuse, and the cloth is 4.5 times more able to resist stretching

6. stretch is inversely proportional to the modulus of the material times the cross sectional area of the thread... sail cloth woven from high modulus yarns stretches far less than sailcloth woven from less expensive yarns.... adjusted for many other factors such as the amount of yarn crimp, thread alignment, tightness of weave, resination, .... etc... etc... whew.... it gets complicated.... yada, yada, yada


Fair winds,
Judy B

PS. It's been about 20 years since my last mechanical course, and I'm sure I've made a few mistakes in terminology, and maybe the math. If I've used the terms wrong, I hope a knowledgeable person will jump in to correct my terminology. Thanks.

[bscott]

WOW And you didn't even get around to the CE of a reefed head sail
I chose to sell my CDI for $200 rather than modify my sails and gave up my Bud Lite for a month to make up the difference.

Bob

[Judy B]

The manager of the Hyde loft in San Diego, CA quoted $4 per foot to change a luff tape from one size to another (not to be confused with converting from hanks to luff tape). The luff is about 25' -- so the job is $100 plus shipping. Not too bad.

Fair winds,
Judy B