Rig loading with deck stepped mast on a Flicka

[William Hogan]

Hi all!

I'm new to this forum, and have read many posts about rig tuning, as well as Brion's book, Ivar's book, and the instructions on my Loos tuning gauge.

I'm also a licensed Architect in California, so while I'm not a wire splicing bowline throwing mast swinging rigger, I do have some expertise in structural engineering, properties of materials, physics, and and all that. I'm also a sailor with a Pacific Seacraft Flicka 20

There is a lot of BS flying around my dock and in various online forums about the proper way to tune and tension rigs, with most people recommending slack rigs.

I disagree with this. I recently tuned my rig at sea over a couple of days in fresh conditions, following the advice I found in Ivar Dedekams "Sail and Rig Tuning" Toss's "Riggers Apprentice" and my gage's instruction manual - which all agree on the allowable tensions and basic techniques for accomplishing this task. The recommended proceedures and theories I read in each reference square perfectly with my engineering knowledge, so I put to sea, and when conditions were right, I started tuning and tacking.

When finished with sea-tuning, I checked the various rigging loads with my gauge and found them all to be under 20% of the 3/16 wire's breaking load - and I sailed the boat HARD - over canvassed and heeled over between 25 and 35 degrees in flat water, in around 25 knots of wind. Headstay sag is now minimal, the leeward shrouds don't go slack, the mast is straight, and it bends very little at the head when fully heeled over.

So far, so good, right?

Well, when I posted the numbers (I won't bore you with them) from my gauge in the Yahoo groups Flicka list, a number of fellow owners freaked out, saying I was going to collapse my roof, etc, etc, etc...

When prompted for evidence of weakness in said roof, or of any known failures, there was silence.

As most you know, Flickas are small, heavy displacement traditional style pocket cruisers. They are heavily constructed, most by Pacific Seacraft, and designed and fitted for bluewater passage making. Many have crossed oceans, and the only reason no one has ever circumnavigated one is that they are small, expensive boats, and there are cheaper, more comfortable options if that's your goal.

The mast is deck stepped, and supported by a thick solid plywood coach roof, which is in turn supported by a 2" thick wooden arch. Sail area is modest at around 200 square feet, the rig is short, and displacement is 3 tons with an 18 foot waterline.

From what I understand and have read, lose rigging is dangerous, and leads to all sorts of really bad things like load cycling, metal fatigue, excessive deflection, etc. Weekend sailors in calm conditions might never notice this, but venture out in bad weather, or put to sea for months on end, and this is going to be a BIG problem eventually, that will no doubt manifest at the WORST possible moment.

I have not been able to find any allowable tension specs for the design, so have used empirical sea trials to set tension, and that exercise yielded tension values that are well under the already conservative 25% of breaking load rule of thumb.

My argument is that unless Bruce Bingham was an incompetent Naval Architect, PSC a shoddy builder, and all of my research sources and engineering knowledge are consistently wrong, the hull, fittings, and coach roof of a Flicka should EASILY support 20% of breaking load, and a hell of a lot more in extremis.

If you don't properly snub the rig down and load up the coach roof tangs, wires, and chainplates once, properly, the ocean and wind will do so repeatedly on passage, imposing large dynamic loads 1000s of times.

This is bad - very, very bad.

If my rig or support structures can't support proper loading I want to find out now in my slip, not at sea in a gale, thank you very much.

Any input on this will be appreciated. If I'm wrong on anything, I want to know, because I hate ignorance. I'll link to this thread and share your input with those on the Flicka forum. I believe this is an important safety and performance topic - one that is basic, yet poorly understood by most sailors.

Thanks in advance -

Bill Hogan

[Ian McColgin]

You're doing fine. There are plenty of boats with deck stepped boats where the step is supported on a usually arched deck beam rather than a compression post. If engineered properly, like the old Electra, a very early cruiser by Pearson with more hulls done in the daysailor Ensign version, it's plenty strong enough for the small rig.

In general a rig is tensioned to the point where the lee shrouds in a good breeze are just unloaded. Not slack but not bar taught. At that point, the total compression of the loaded shrouds and stays on the mast and step is the same as with a rig that's slack when no sail is up. So, having a slack rig does not rest things to any meaningful extent.

Sometimes in winter a rig, especially on an older wooden hull, might be detuned a little, but not slacked to the point of rattling about. If too loose, the rig will just shake the boat and stress the fastenings even sitting on the mooring.

G'luck

[William Hogan]

Thanks Ian - that's exactly what I suspected. I'll share this and any other comments with the Flicka 20 owners group so we can finally lay this issue to rest over there. I have some rigging tricks and configurations I've figured out for the Flicka that are simple, cheap, and make her much easier and safer to sail and tack down wind with that I'll share with all of you for comment and use - if you like them that is!

In the mean time, though you guys might enjoy some salty super slow motion footage I've shot of my Flicka "Nomad" and a Contessa 26 in fresh conditions on Santa Monica bay last week:

http://www.youtube.com/watch?v=Z4obYYuC1m0&sns=em

Enjoy.

[Brion Toss]

Hello,
I'll just add that the "slack-tune-is-good" argument exists, somehow, in the face of exhaustively detailed and proven evidence to the contrary, and that this evidence is available, repeatable, and produces consistent results. On the other hand, it is possible to overtune a rig, with harmful consequences, and people might be reacting to episodes of that behavior. As with all other endeavors, there are many more ways to do things wrong than there are to do them right.
Fair leads,
Brion Toss