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Catalina/Capri 25/250 Sailor's Forums

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Loos Gauge

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Robb
1st Mate

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Canada
31 Posts

Initially Posted - 07/26/2021 : 11:50:18

Having some challenges getting my rigging tuned. I've read that a Loos gauge is a good thing to have. Does anyone use one when they set up their rigging annually? (for those who lower their mast at annually). Are they difficult to use?

Robb
2004 C250 WK hull# 739

k3fuller
1st Mate

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USA
73 Posts

Response Posted - 07/26/2021 : 13:03:12

I don't use mine. I still go by Arlyn Stewarts comments in this post from 2007 and it has served me well since I've owned the boat (2004 WB).

http://www.catalina-capri-25s.org/forum/topic.asp?ARCHIVE=true&TOPIC_ID=15249

Throw away the loose gauge numbers from web sites, books, riggers or any other place they can be found because the 250 isn't typical and those numbers are not suitable to her.

I'm not saying that the guage is worthless... just the numbers you will see out there as applying to the 250.

Here is the deal... the 250 has a very different rig than most of those numbers apply to. The 250 has a modified form of a B&R rig and has no forward lowers. It also has lighter rigging as it is a lightly keeled boat. It is also an open hull without interior bulkheads. The available numbers just don't fit.

The 250 should be tuned firm but not hard, with the upper shrouds (the aft shrouds that go to the spreaders and then on to the mast head) a good bit firmer than the forward (those just below the spreaders).

I know it would be easier if someone could just yield some numbers but first thing to understand is that the loose guages often read very different and there are several differing guages making things even worse. It is better to understand the dynamics of the rig tuning.

What is wanted is a settup that doesn't allow the foresail too much power. To get that the aft lowers should be tuned firm as they are the opposing force to the headstay (though you may be saying...this guy is whacko, the backstay is the opposing force to the headstay... trust me, I'm right about this on the 250.) Tighten them firm but loose enough to allow an inch of deflection when pulling the shroud after grasping it with two fingers at the last finger joints and curling the fingers inward. I know there are those who are thinking this ain't scientific enough... but trust me you will get a feel for it.

The forward lowers should deflect about twice as much as the aft given the same test. If the forwards are tightened too much (equal to the uppers), it will induce reverse (aft) mast bend that is not desirable.

The light rig of the 250 cannot sustain the numbers given for a boat with bulkheads and having a heavy keel and a rig needed to handle a heavy keel.

The last stay to tune is the backstay...tighten it only enough to pull it straight where it won't sag into the sail roach. Do not overtighten the backstay as to do so will release some of the tension on the aft lowers. It is the aft lowers that leverage against the raked spreaders that hold the center of the mast forward so overtightening the backstay reduces the ability of the uppers to hold the center of the mast forward... this is why the 250 is not a candidate for an adjustable backstay tensioner.

If after tuning, one feels that in a breeze the headsail has too much power because of a loose forestay and is sagging off too much...then tighten the uppers a bit more.

A simple test is when running hard to windward in a breeze, the leeward upper shouldn't be shaking but the leeward lower should have some slack. If there isn't any slack... then the lowers may be too tight. If the rig is too tight... light air performance will suffer and if it is too loose, then it can be overpowered in a breeze and suffer too much heel and helm pressure.

Of course it goes without saying when adjusting shrouds to observe symmetry. Once the mast head has been centered using a halyard to the rub rail on each side and the mast column straightness has been set by the lowers... any further adjustment of a shroud has to be countered by an equal adjustment on the other side.

Now...once a settup has been achieved that seems good...then one can use a loose guage and write down those numbers and use them to compare further adjustments and possibly even use them against other similar 250's... but not other boat designs. Keep in mind however that even with the same boat and loose guage... the guages may not read the same.

One final point... the 250 is not typical to heavily keeled boats that need a firm tough rig to handle the sailplan opposing the keel. Those boats will groan and strain under a broach whereas the 250 heels over and rounds up and shakes a broach off like it was no big thing. Many a tradional boat skipper will scoff at the light rigging of the 250 thinking it is dangerous... but it's not true... the rigging is very adequate to the boat design.

I've yet to hear reported to this forum an instance of rig failure from overload on a 250. There have been a couple of failures reported but do to snagging the shrouds on other boats or objects.
Edited by - on

2004 250WB #781

Edited by - k3fuller on 07/26/2021 13:04:23

alippold
Deckhand

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USA
22 Posts

Response Posted - 07/26/2021 : 14:47:22

I do use my Loos gauge to tune the rig. I was having trouble tuning and hired an rigging expert from our boatyard to tune it several years ago. My 250 WB was much faster than it had ever been before after this tuning job! I wrote down the numbers using the Loos gauge and replicate them every year. I go through all the steps in the manual but try to end up with 38 for the uppers, 30 for the lowers and about 18 on the backstay (as measured on one of the side of the lower V).

Amber Waves

TakeFive
Master Marine Consultant

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2269 Posts

Response Posted - 07/26/2021 : 15:07:01

quote:
Originally posted by alippold

I do use my Loos gauge to tune the rig. I was having trouble tuning and hired an rigging expert from our boatyard to tune it several years ago. My 250 WB was much faster than it had ever been before after this tuning job! I wrote down the numbers using the Loos gauge and replicate them every year. I go through all the steps in the manual but try to end up with 38 for the uppers, 30 for the lowers and about 18 on the backstay (as measured on one of the side of the lower V).

You need to supply a little more detail. What model gauge? PT-1, or something else? Also, are the numbers raw numbers off the gauge, % of full load for the diameter of cable, or some other units?

I have no skin in this game, but I'd hate to see someone damage his rig by over-torquing.

Also, how much pre-bend did you end up with?

Rick S., Swarthmore, PA
PO of Take Five, 1998 Catalina 250WK #348 (relocated to Baltimore's Inner Harbor)
New owner of 2001 Catalina 34MkII #1535 Breakin' Away (at Rock Hall Landing Marina)

TakeFive
Master Marine Consultant

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2269 Posts

Response Posted - 07/26/2021 : 15:16:37

quote:
Originally posted by k3fuller

The forward lowers should deflect about twice as much as the aft given the same test. If the forwards are tightened too much (equal to the uppers), it will induce reverse (aft) mast bend that is not desirable.

The C250 has no forward lowers.

Rick S., Swarthmore, PA
PO of Take Five, 1998 Catalina 250WK #348 (relocated to Baltimore's Inner Harbor)
New owner of 2001 Catalina 34MkII #1535 Breakin' Away (at Rock Hall Landing Marina)

JB
Navigator

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USA
110 Posts

Response Posted - 07/26/2021 : 15:23:33

I only use mine to set the relative tension left to right.

1988 C25 Wing Keel Std Rig Tohatsu 9.9 Tiller Steering and 2003 C250 Wing Keel Std Rig Inboard Diesel Wheel Steering

Steve Milby
Past Commodore

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USA
5851 Posts

Response Posted - 07/26/2021 : 16:09:23

I agree that a loos gauge has almost nothing to do with tuning the rig of a sailboat.

When you tune a rig, your overall goal is to adjust the balance between the center of effort (CE) of the sailplan against the center of lateral resistance of the keel (CLR). If you move the center of effort of the sailplan aft, in relation to the CLR, then you will cause a stronger weatherhelm. If you move it forward, you will either decrease weatherhelm, or even cause lee helm, if you move it too far forward. The way you move the CE forward or aft is by tilting the mast forward or aft. This is called adjusting the rake of the mast. A loos gauge doesn't help you adjust the rake. You adjust the rake by sailing the boat in about 10 kt winds and feeling how much weatherhelm it has. Then you tilt the mast forward a little at a time until you feel a light weatherhelm.

Another goal of rig tuning is to make sure your mast is in column (straight), because a mast that is out of column is weak, and susceptible of breaking. A loos gauge doesn't help here either. You check to see that the mast is straight and in column by lying on your back on the deck and sighting up the mast.

The last goal is to adjust the power of the rig. In light air, you want a very powerful rig, and in strong winds, you want to depower the rig. In that vein, a loose rig is powerful, and a taut rig is depowered. If you know what loos gauge readings are best for each stay in light, medium and strong winds, then a loos gauge might be useful. Absent such detailed information, a loos gauge can only be used to adjust rig tension for average or ordinary sailing conditions.

In reality, the only significant value of a loos gauge is that, after your rig has been adjusted, it can tell you if any of your stays are too taut, and thus apt to cause damage to your boat.

The first goal is the most important in achieving excellent boat performance. Strong weatherhelm requires the helmsman to use strong pressure on the tiller to keep the boat pointing where you want it to go. By reducing weatherhelm to a minimum, you reduce drag caused by the rudder. A boat with light weatherhelm points high and sails fast.

The second goal ensures that the mast stays in column and strong, even when the boat is pounding through steep seas and chop.

The third goal matches the power of the rig to the sailing conditions.

As you can see, rig tuning really isn't as mysterious or complicated as one might think. Follow each of the above steps, tighten the stays equally from side to side, so that the rig doesn't slap loosely in a chop, and it will be good. If you plan to sail in rougher conditions, tighten them up a bit. Loosen them a bit in light air.

That might sound unscientific, but rig tuning is more art than science, and this process will get better results than the arbitrary settings of a loos gauge, because your rig will be adjusted more accurately for the sailing conditions.

Steve Milby J/24 "Captiva Wind"
previously C&C 35, Cal 25, C25 TR/FK, C22
Past Commodore

alippold
Deckhand

Members Avatar

USA
22 Posts

Response Posted - 07/27/2021 : 14:26:54

quote:
Originally posted by TakeFive

quote:
Originally posted by alippold

I do use my Loos gauge to tune the rig. I was having trouble tuning and hired an rigging expert from our boatyard to tune it several years ago. My 250 WB was much faster than it had ever been before after this tuning job! I wrote down the numbers using the Loos gauge and replicate them every year. I go through all the steps in the manual but try to end up with 38 for the uppers, 30 for the lowers and about 18 on the backstay (as measured on one of the side of the lower V).

You need to supply a little more detail. What model gauge? PT-1, or something else? Also, are the numbers raw numbers off the gauge, % of full load for the diameter of cable, or some other units?

I have no skin in this game, but I'd hate to see someone damage his rig by over-torquing.

Also, how much pre-bend did you end up with?

I didn't know there were so many different Loos gauges. Mine came with the boat when I bought it and is an old Model A. The numbers I entered are raw numbers from the gauge. Here is a picture of the gauge so anyone who is interested can convert those numbers to lbs tension for the 5/32 shrouds on a Cat 250 WB

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I strive to follow the user manual for the boat when tuning. The prebend in my mast appears to be about the 1.5 inches called for in the manual. Since you can't really measure the prebend, I am just making the halyard taut to the mast and eyeballing it.

Amber Waves

Robb
1st Mate

Members Avatar

Canada
31 Posts

Response Posted - 07/27/2021 : 22:33:44

Folks - thanks so much for sharing your expertise on this and taking the time to provide such detailed information. I'll be taking another kick at the Cat (couldn't resist - sorry) later this weekend/early next week and will take into account all your guidance and report back! Having sailed a Freedom and a Laser for the past 25 yrs (both freestanding masts with no standing rigging) I'm still a novice at tuning so your guidance is appreciated!