Upper Spreaders and Shrouds

[kkearns]

I believe I've seen talk on these forums about removing the upper spreaders and shrouds on the DS1. The opinion has been expressed that they add no significant strength to the mast and do little more than add unneeded weight aloft. Can someone give me an authoritative answer on this? Many thanks.

By the way, I've had my "new" 1965 DS1 (#1827) out on the water quite abit this summer in both mild and not so mild conditions. I love this boat!!!

Kevin Kearns

[kokko]

You must be referring to the diamond spreaders. While they are not necessary, they are useful: they reduce mast bend on the upper half of the mast. I replace mine last spring, and had to rebuild the two 12" spreaders with copper pipe.

[K.C. Walker]

There are advantages to not having the upper spreaders and shrouds to stiffen up the upper section of the mast. Having a somewhat bendy mast is considered a good thing in a small boat. It helps with gust control and sail shape. If you look at the pictures of the 2009 national championships you will see that none of the boats have the upper diamond spreaders. By the way, I've looked at these pictures over and over again to see what all the good setups are. http://forum.daysailer.org/forum/viewtopic.php?t=2941

One of the most desirable masts for racing a daysailer is a Proctor tapered mast. These masts are even bendier up top than a straight mast.

This summer I've been reading Stuart H. Walker's manual of sail trim. In this book, mast bend is a big part of sail trim.

KC

[Imgaryo1]

K.C. Walker is absolutely correct. Mast bend is desirable. Take the upper spreaders OFF!

[seandwyer]

I've accepted the fact that removal of the jumper struts / upper spreaders is desirable, but I'm curious as to why they were there to begin with. Was the mast simply designed by thinking too much like a bigger boat, or has the theory concerning sail design and shape changed over the years? I spent half this summer with them on, then removed them in July. I haven't noticed any difference, but occasionally during heavy wind I feel nervous that things aren't as stout up top as they should be - considering I've essentially removed something that was designed to be there. Anyone else have thoughts on this? How much flex is the mast capable of before it becomes to much?

[dannyb9]

'in my opinion' sailors and shapers have learned that a more bendy mast can be used to help control sail shape...if you have a bendy mast you can flatten the sail by adding sheet and or vang tension. very useful upwind and reaching in a breeze. then when you go offwind, the mast straightens and the sail becomes fuller. with a rigid mast, the sail shaping options are more limited. plus a bendy mast allows the top of the sail to blow off some power up high in gusts, reducing heel and making it easier to keep the boat flat. flat is faster

[Imgaryo1]

If you reach that point you should definitely have been off the water.

[K.C. Walker]

The sail area above the shrouds is not very big. I expect that it's no more than what a laser carries in sail area, if that. Have you seen the size of a laser mast? Or, how much bend they put in them and how they bend with wind gusts? Oh yes, and have you seen what kind of conditions they will go out in? In high winds you're much more likely to damage your mast by turning turtle and having it stuck to the bottom! The boat is going to go over before you put too much stress on the mast up top.

Another example of good use of a bendy mast is with the fastest sail craft in the world, a windsurfer. Windsurfers use mast bend as THE method of tuning their rig. If you watch a windsurfer in high winds you can see most definitely how the top of the rig being flexible helps with gusts control. The top of the mast flexes and lets the top of the sail twist out. It's the same idea with a daysailer but just not as obvious. As you learn to control your sails more and pay attention to sail twist you will observe how the bendy mast helps you out.

One of the things that I really like about sailing is paying attention to the subtleties. We are definitely talking subtleties here and unless you have a way to measure the difference you may not be able to tell.

KC

[Marv Irwin]

Greetings,

Let me toss in another perspective: I agree with the previous posts about a bendy upper mast allowing the sail to be depowered for flatter progress in gusty conditions..........but......I have kept my upper spreaders because I think they make my little Daysailer look nautical. The noisy chorus of halyards at anchor and the very nautical look of those diamond spreaders can almost make me believe I'm in the Caribbean.

Marv

[seandwyer]

Marv - I agree. It pained me to remove them because the look definitely suffered. I was told to cut them - but I removed the pins and have stored them in case.

Here is the question that still resides in my nervous little brain - I understand the point about bendy masts - but is one mast designed to be bendy whereas another may not have been? I am thinking about different shapes, wall thicknesses or alloys that lend themselves to flexibility rather than brittleness and the possible necessity of more support. Could my original 1968 mast eventually be stressed to the point of failure? However - K.C. - you certainly make a good point - we aren't talking about a fixed object, but rather a boat free to move and rock and even (gasp) turn turtle. Considering that I've heard that guys pull their boats over to repair the bottom by simply yanking on the halyard ought to console me, but nevertheless, I remain filled with questions. I need to let go, don't I?

[K.C. Walker]

Looking nautical... don't forget your captain's hat, parrot on your shoulder, and your smoking pipe.

Maybe to let go you should try tipping your boat. I was working on the bottom of my boat this summer and tipped it on its side by pulling the main halyard out to the side. I think you'd truly be amazed at how little force it takes to tip the boat. I mean, it's truly easy to tip them over by pulling the halyard at the top of the mast. Ask the many racers that capsize these boats, believe me the boats going over first.

KC

[GreenLake]

(@K.C: nicely put!)

In order for the bendy mast to be optimal, I suspect the sail has to be cut to make best use of the degree of mast bend. I wonder whether the original sails were cut differently than modern sails?

I could also imagine that a really old sail (in terms of years of service, not age of the design) could be too baggy to allow the effect of the increased mast bend to be noticeable. Or a sail cut for the tapered mast could be such that the lesser bend of the straight mast isn't enough to cause a noticeable effect.

Also, I wonder whether anyone of the "old guard" still reads the forum and can chime in with actual before/after experience. As usual with subtle modification, there's the problem of whether (or at what point) qualitative improvements become quantifiable. In other words, while the effect may be theoretically present, is it observable at all, in casual sailing? or only when racing in very high winds??

Just curious. (Now for the full disclosure: I haven't tried to remove mine yet - inertia for the most part...)

[K.C. Walker]

Okay, this is sort of a good test of my understanding of the bendy mast.

The upper 3rd of the sail is where a great deal of the driving force and healing force of the mainsail in a fractional rig sloop happens. Also, the upper 3rd of the sail is in a higher wind velocity due to winds aloft being higher than those near the water. Also, the upper 3rd of the sail experiences a different angle of incidence due to there being no jib in front of it.

So, a bendy mast automatically helps you control the power of the sail in a gust by allowing the leech to open and twist away (as the mast tip moves aft and to leeward), also, automatically flattening the sail by pulling on the luff (as the middle of the bend moves forward and to windward). This happens on all sails regardless of cut and condition. Of course, it works much better with well cut sails that are new.

As to being able to tell the difference; everything in sailing is subtle. However, in 12 kn breeze the beginning sailor can be overwhelmed and going nowhere, whereas the more experience sailor can be planing cross the water with a big grin on their face.

KC

[GreenLake]

Your description of the theory matches my understanding. Except for a small detail. I've read somewhere that the effect of different wind speed (and direction) with increasing height along the mast is less pronounced when the air flow is turbulent (breeze) compared to laminar flow when the air is moving more slowly across the water. About 6 knots is where one should change into the other. (Turbulent flow mixes upper and lower air constantly, bringing "fast" air down).

(I admit, the "planing cross the water with a big grin" is not something that happens to me very frequently - too often I find myself stuck in light winds, or with beginner crew that are not ready for stronger winds.)

[jpclowes]

Sean
I took the Diamond stays off my mast several years ago. I have never had a problem. I don't think I ever sailed the boat with them on, so I can't say if they made a change. I have sailed my boat in most conditions that you are likely to find here in Ohio, and never thought twice about the top of the mast being strong enough on its own. I also increased the size of the shrouds and forestay from what was standard, (from 3/16 to 1/8) which would put even more stress on the top of the mast. Again, never had a problem.

IMHO the real danger to your mast, is your main stays. If you lose a stay, for whatever reason, that is when you are likely to do the most damage to your mast. Inspect your pins, and the wires frequently. If there is any sign of broken strands replace them.